WO2025044188A1 - Vascular imaging system, method and device, and electronic device and storage medium - Google Patents

Abstract

A vascular imaging system, method and device, and an electronic device and a storage medium. The vascular imaging system comprises: an ultrasound device, which is used for collecting intravascular ultrasound images of a target object; an angiography device, which is used for collecting coronary angiography images of the target object; and a processing device, which is connected to both the ultrasound device and the angiography device, and is used for: determining a waveform-free interval of a diastolic phase within a cardiac cycle of the target object; respectively acquiring, from the images respectively collected by the ultrasound device and the angiography device, a target ultrasound image and a target angiography image of a target blood vessel of the target object within the waveform-free interval of the diastolic phase; performing vascular reconstruction on the basis of the target ultrasound image and the target angiography image, so as to generate a vascular model for the target blood vessel; and determining a fractional flow reserve of the target blood vessel on the basis of vascular parameters in the vascular model. The solution can reduce the discomfort of a subject, save on the test costs of the subject, and facilitate an improvement in the calculation precision of the fractional flow reserve of the target blood vessel.

Description

Vascular imaging system, method, device, electronic device and storage medium Technical Field

The present application relates to the technical field of image acquisition and processing, and more specifically to a vascular imaging system, a vascular imaging method, a vascular imaging device, an electronic device and a computer-readable storage medium.

Background Art

Fractional flow reserve (FFR) is defined as the ratio of the maximum blood flow that can be obtained by the myocardial area of the coronary artery under the condition of stenosis to the maximum blood flow that can be obtained by the same area under normal conditions. FFR truly reflects the impact of coronary artery stenosis caused by obstruction on its function and describes the limitation of the maximum blood flow of the myocardium when the coronary artery is stenotic. In the case of maximum hyperemia (when the resistance in the coronary artery is the smallest and relatively constant), the blood flow in the coronary artery lumen is linearly related to the pressure. Therefore, the value of FFR can be simplified as the ratio of the mean pressure at the distal end of the coronary stenosis ( _Pd ) to the mean pressure at the aortic root or the coronary artery opening ( _Pa ) under maximum hyperemia.

In the related art, the measurement of FFR is mainly to measure the ratio of the distal pressure of the lesion stenosis to the proximal arterial pressure under the state of maximum hyperemia through a pressure intervention guidewire or a microcatheter. In this process, vasodilators (such as adenosine) are usually required to make the blood vessels reach the maximum hyperemia state. And the measurement process needs to span several cardiac cycles to ensure that the pressure in the coronary artery reaches the lowest and is relatively stable. However, even after the administration of potent drugs such as adenosine, the resistance in the coronary artery is not static, but fluctuates in a phase mode throughout the cardiac cycle. These fluctuations reflect the changes in the myocardium and microvessels during systole (high coronary artery resistance, microvascular compression) and diastole (low coronary artery resistance). Therefore, in order to minimize these effects, FFR usually calculates the maximum flow to the vascular bed during hyperemia and averages it over several cardiac cycles to ensure that the resistance in the coronary artery is constant and minimal. Therefore, the whole process takes a long time and has high requirements for drug dosage and administration method. In addition, there are differences in the response and tolerance of different subjects to drugs, which will also affect the measurement accuracy. Adenosine also has related contraindications in clinical use, such as asthma, severe chronic obstructive pulmonary disease, hypotension and bradycardia, which further limit its clinical use.

Summary of the invention

The present application is proposed in view of the above problems. The present application provides a vascular imaging system, a vascular imaging method, a vascular imaging device, an electronic device and a computer-readable storage medium.

According to one aspect of the present application, a vascular imaging system is provided, comprising: an ultrasound device for acquiring an ultrasound image within a blood vessel of a target object; an angiography device for acquiring a coronary angiography image of the target object; a processing device, connected to the ultrasound device and the angiography device, respectively, for: determining a diastolic waveform-free interval within the cardiac cycle of the target object; acquiring a target ultrasound image and a target angiography image of a target blood vessel of the target object within the diastolic waveform-free interval from the images acquired by the ultrasound device and the angiography device respectively; performing vascular reconstruction based on the target ultrasound image and the target angiography image to generate a vascular model of the target blood vessel; and determining a blood flow reserve fraction of the target blood vessel based on vascular parameters in the vascular model.

Exemplarily, the vascular imaging system also includes an electrocardiogram device for acquiring an electrocardiogram signal of a target object, and a processing device is connected to the electrocardiogram device, wherein the processing device determines the diastolic waveform-free interval within the cardiac cycle of the target object in the following manner: receiving the electrocardiogram signal of the target object from the electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal; the processing device is also used to: when the start moment of the diastolic waveform-free interval is identified, control the ultrasound device to start acquiring intravascular ultrasound images; when the end moment of the diastolic waveform-free interval is identified, control the ultrasound device to stop acquiring intravascular ultrasound images; the processing device acquires a target ultrasound image of a target blood vessel of the target object within the diastolic waveform-free interval from the image acquired by the ultrasound device in the following manner: acquiring the intravascular ultrasound image acquired by the ultrasound device as the target ultrasound image.

Exemplarily, the vascular imaging system further includes an electrocardiogram device for collecting electrocardiogram signals of the target object, and the processing device is connected to the electrocardiogram device, wherein the processing device determines the diastolic phase in the cardiac cycle of the target object by the following method: Waveform-free interval: receiving an electrocardiogram (ECG) signal of a target object from an electrocardiogram (ECG) device; identifying a diastolic waveform-free interval based on the ECG signal; a processing device acquiring a target ultrasound image of a target blood vessel of a target object within the diastolic waveform-free interval from an image acquired by an ultrasound device in the following manner: based on the identified diastolic waveform-free interval, selecting a target ultrasound image from intravascular ultrasound images acquired by the ultrasound device; wherein the ultrasound device and the ECG device synchronously acquire their respective corresponding intravascular ultrasound images and ECG signals, and the ultrasound device continuously acquires intravascular ultrasound images.

Exemplarily, the vascular imaging system also includes an electrocardiogram device for collecting electrocardiogram signals of a target object, and a processing device is connected to the electrocardiogram device. The processing device determines the diastolic waveform-free interval within the cardiac cycle of the target object in the following manner: receiving the electrocardiogram signal of the target object from the electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal; the processing device is also used to: when the start moment of the diastolic waveform-free interval is identified, control the angiography device to start collecting coronary angiography images; when the end moment of the diastolic waveform-free interval is identified, control the angiography device to stop collecting coronary angiography images; the processing device obtains a target angiography image of a target blood vessel of the target object within the diastolic waveform-free interval from the image collected by the angiography device in the following manner: from the coronary angiography images collected by the angiography device, select at least two frames of angiography images at different angiography angles as target angiography images.

Exemplarily, the vascular imaging system also includes an electrocardiogram device for acquiring an electrocardiogram signal of a target object, and a processing device is connected to the electrocardiogram device, and the processing device determines the diastolic waveform-free interval within the cardiac cycle of the target object in the following manner: receiving the electrocardiogram signal of the target object from the electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal; the processing device obtains a target angiography image of a target blood vessel of the target object within the diastolic waveform-free interval from an image acquired by an angiography device in the following manner: based on the identified diastolic waveform-free interval, selecting at least two frames of candidate coronary angiography images of different angiography angles from the coronary angiography images acquired by the angiography device as target angiography images; wherein the candidate coronary angiography image is a coronary angiography image acquired by the angiography device during the diastolic waveform-free interval; wherein the angiography device and the electrocardiogram device synchronously acquire their respective corresponding coronary angiography images and electrocardiogram signals, and the angiography device continuously acquires coronary angiography images.

Exemplarily, the processing device identifies the diastolic waveform-free interval based on the ECG signal in the following manner: based on the waveform amplitude characteristics of the ECG signal, calculating the instantaneous resistance at each moment in the cardiac cycle; based on the instantaneous resistance at each moment in the cardiac cycle, determining the diastolic waveform-free interval.

Exemplarily, the processing device performs blood vessel reconstruction based on the target ultrasound image and the target contrast image to generate a blood vessel model of the target blood vessel in the following manner: identifying the centerline of the target blood vessel from the target contrast image; identifying the lumen contour of the target blood vessel from the target ultrasound image; and aligning and reconstructing the lumen contour along the centerline to obtain a blood vessel model.

Exemplarily, the processing device is also used to: identify side branches of a target blood vessel from a target ultrasound image; the processing device registers and reconstructs the lumen contour along the centerline to obtain a blood vessel model by registering and reconstructing the side branches together with the lumen contour along the centerline.

Exemplarily, the ultrasound device includes an ultrasound catheter and an ultrasound transducer disposed on the ultrasound catheter; the ultrasound transducer is used to acquire an intravascular ultrasound image of the target object during the retraction of the ultrasound catheter; the processing device identifies the centerline of the target blood vessel from the target angiography image in the following manner: for each frame of coronary angiography image in the target angiography image, determine the retraction starting point and the retraction end point of the ultrasound catheter in the coronary angiography image; based on the retraction starting point and the retraction end point, extract the retraction path of the ultrasound catheter from the coronary angiography image; based on the retraction path corresponding to each frame of coronary angiography image in the target angiography image, generate a three-dimensional retraction path of the ultrasound catheter; wherein the centerline of the target blood vessel is represented by a three-dimensional retraction path.

Exemplarily, the processing device extracts the retraction path of the ultrasound catheter from the coronary angiography image based on the retraction starting point and the retraction end point in the following manner: preprocessing the coronary angiography image to obtain a preprocessed coronary angiography image, wherein the preprocessing includes filtering and/or histogram enhancement processing; performing vascular boundary enhancement on the target blood vessel in the preprocessed coronary angiography image to obtain a boundary-enhanced coronary angiography image; performing image binarization and morphological denoising on the boundary-enhanced coronary angiography image to obtain a processed coronary angiography image; and extracting the shortest path with the retraction starting point as the starting point and the retraction end point as the end point from the processed coronary angiography image as the retraction path.

Exemplarily, the vascular parameters include the cross-sectional areas corresponding to each point on the long axis of the vascular model. The processing device determines the blood flow reserve fraction of the target vessel based on the vascular parameters in the vascular model in the following manner: determining the stenotic vessel segment and the normal vessel segment in the vascular model based on the size of the cross-sectional areas corresponding to each point on the long axis of the vascular model; obtaining the mean arterial pressure of the target vessel; and determining the blood flow reserve fraction of the target vessel based on the cross-sectional areas corresponding to the stenotic vessel segment, the cross-sectional areas corresponding to the normal vessel segment, and the cross-sectional areas corresponding to the stenotic vessel segment. The length of the segment is used to determine the pressure difference corresponding to the stenotic vessel segment; based on the mean arterial pressure and the pressure difference, the blood flow reserve fraction of the target vessel is determined.

According to another aspect of the present application, a vascular imaging method is also provided, including: determining a diastolic waveform-free interval within the cardiac cycle of a target object; acquiring a target ultrasound image and a target angiography image of a target blood vessel of the target object within the diastolic waveform-free interval from images acquired by an ultrasound device and an angiography device respectively; performing vascular reconstruction based on the target ultrasound image and the target angiography image to generate a vascular model of the target blood vessel; and determining a blood flow reserve fraction of the target blood vessel based on vascular parameters in the vascular model.

Exemplarily, determining the diastolic waveform-free interval within the cardiac cycle of the target object includes: receiving an electrocardiogram signal of the target object from an electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal; the method also includes: when the start moment of the diastolic waveform-free interval is identified, controlling the ultrasound device to start acquiring intravascular ultrasound images; when the end moment of the diastolic waveform-free interval is identified, controlling the ultrasound device to stop acquiring intravascular ultrasound images; acquiring a target ultrasound image of a target blood vessel of the target object within the diastolic waveform-free interval from the image acquired by the ultrasound device, including: acquiring the intravascular ultrasound image acquired by the ultrasound device as the target ultrasound image.

Exemplarily, determining a diastolic waveform-free interval within a target object's cardiac cycle includes: receiving an electrocardiogram (ECG) signal of the target object from an electrocardiogram (ECG) device; identifying the diastolic waveform-free interval based on the ECG signal; and acquiring a target ultrasound image of a target blood vessel of the target object within the diastolic waveform-free interval from an image acquired by an ultrasound device, including: selecting a target ultrasound image from intravascular ultrasound images acquired by the ultrasound device based on the identified diastolic waveform-free interval; wherein the ultrasound device and the ECG device synchronously acquire their respective corresponding intravascular ultrasound images and ECG signals, and the ultrasound device continuously acquires intravascular ultrasound images.

Exemplarily, determining the diastolic waveform-free interval within the cardiac cycle of the target object includes: receiving an electrocardiogram signal of the target object from an electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal; the method also includes: when the start moment of the diastolic waveform-free interval is identified, controlling the angiography device to start acquiring coronary angiography images; when the end moment of the diastolic waveform-free interval is identified, controlling the angiography device to stop acquiring coronary angiography images; obtaining a target angiography image of a target blood vessel of the target object within the diastolic waveform-free interval from the image acquired by the angiography device, including: selecting at least two frames of coronary angiography images at different angiography angles from the coronary angiography images acquired by the angiography device as target angiography images.

Exemplarily, determining the diastolic waveform-free interval within the cardiac cycle of the target object includes: receiving an electrocardiogram (ECG) signal of the target object from an electrocardiogram (ECG) device; identifying the diastolic waveform-free interval based on the ECG signal; and obtaining a target angiography image of a target blood vessel of the target object within the diastolic waveform-free interval from an image acquired by an angiography device, including: based on the identified diastolic waveform-free interval, selecting at least two frames of candidate coronary angiography images of different angiography angles from the coronary angiography images acquired by the angiography device as target angiography images; wherein the candidate coronary angiography images are coronary angiography images acquired by the angiography device during the diastolic waveform-free interval; wherein the angiography device and the ECG device synchronously acquire their respective corresponding coronary angiography images and ECG signals, and the angiography device continuously acquires coronary angiography images.

Exemplarily, identifying the diastolic waveform-free interval based on the ECG signal includes: calculating the instantaneous resistance at each moment in the cardiac cycle based on the waveform amplitude characteristics of the ECG signal; and determining the diastolic waveform-free interval based on the instantaneous resistance at each moment in the cardiac cycle.

Exemplarily, blood vessel reconstruction is performed based on the target ultrasound image and the target contrast image to generate a blood vessel model of the target blood vessel, including: identifying the centerline of the target blood vessel from the target contrast image; identifying the lumen contour of the target blood vessel from the target ultrasound image; and aligning and reconstructing the lumen contour along the centerline to obtain a blood vessel model.

Exemplarily, before the lumen contour is registered and reconstructed along the centerline to obtain the vascular model, vascular reconstruction is performed based on the target ultrasound image and the target angiography image to generate a vascular model of the target blood vessel, which also includes: identifying side branches of the target blood vessel from the target ultrasound image; and registering and reconstructing the lumen contour along the centerline to obtain the vascular model, including: registering and reconstructing the side branches together with the lumen contour along the centerline.

Exemplarily, the ultrasound device includes an ultrasound catheter and an ultrasound transducer disposed on the ultrasound catheter; the ultrasound transducer is used to acquire an intravascular ultrasound image of a target object during the withdrawal process of the ultrasound catheter; identifying the centerline of the target blood vessel from the target angiography image, including: for each frame of a coronary angiography image in the target angiography image, determining a withdrawal start point and a withdrawal end point of the ultrasound catheter in the coronary angiography image; extracting an ultrasound image from the coronary angiography image based on the withdrawal start point and the withdrawal end point; A retraction path of the ultrasound catheter; based on the retraction path corresponding to each frame of the coronary angiography image in the target angiography image, a three-dimensional retraction path of the ultrasound catheter is generated; wherein the centerline of the target blood vessel is represented by the three-dimensional retraction path.

Exemplarily, based on the pullback starting point and the pullback end point, the pullback path of the ultrasound catheter is extracted from the coronary angiography image, including: preprocessing the coronary angiography image to obtain a preprocessed coronary angiography image, wherein the preprocessing includes filtering and/or histogram enhancement processing; performing vascular boundary enhancement on the target blood vessel in the preprocessed coronary angiography image to obtain a boundary-enhanced coronary angiography image; performing image binarization and morphological denoising processing on the boundary-enhanced coronary angiography image to obtain a processed coronary angiography image; and extracting the shortest path with the pullback starting point as the starting point and the pullback end point as the end point from the processed coronary angiography image as the pullback path.

Exemplarily, the vascular parameters include the cross-sectional area corresponding to each point on the long axis of the vascular model; based on the vascular parameters in the vascular model, the blood flow reserve fraction of the target blood vessel is determined, including: based on the size of the cross-sectional area corresponding to each point on the long axis of the vascular model, the stenotic blood vessel segment and the normal blood vessel segment in the vascular model are determined; the mean arterial pressure of the target blood vessel is obtained; based on the cross-sectional area corresponding to the stenotic blood vessel segment, the cross-sectional area corresponding to the normal blood vessel segment and the length of the stenotic blood vessel segment, the pressure difference corresponding to the stenotic blood vessel segment is determined; based on the mean arterial pressure and the pressure difference, the blood flow reserve fraction of the target blood vessel is determined.

According to another aspect of the present application, a vascular imaging device is provided, including: a first determination module, used to determine the diastolic waveform-free interval within the cardiac cycle of the target object; an acquisition module, used to respectively acquire a target ultrasound image and a target angiography image of the target blood vessel of the target object within the diastolic waveform-free interval from images respectively acquired by an ultrasound device and an angiography device; a vascular reconstruction module, used to perform vascular reconstruction based on the target ultrasound image and the target angiography image to generate a vascular model of the target blood vessel; and a second determination module, used to determine the blood flow reserve fraction of the target blood vessel based on the vascular parameters in the vascular model.

According to another aspect of the present application, there is also provided an electronic device, comprising a processor and a memory, wherein the memory stores computer program instructions, and the computer program instructions are used by the processor to perform the following operations when executed: determining a diastolic waveform-free interval within the cardiac cycle of a target object; acquiring a target ultrasound image and a target angiography image of a target blood vessel of the target object within the diastolic waveform-free interval; performing vascular reconstruction based on the target ultrasound image and the target angiography image to generate a vascular model of the target blood vessel; and determining a blood flow reserve fraction of the target blood vessel based on vascular parameters in the vascular model.

According to another aspect of the present application, a computer-readable storage medium is provided, on which program instructions are stored, and the program instructions are used to perform the following operations when run: determine the diastolic waveform-free interval within the cardiac cycle of the target object; obtain a target ultrasound image and a target angiography image of the target blood vessel of the target object within the diastolic waveform-free interval; perform vascular reconstruction based on the target ultrasound image and the target angiography image to generate a vascular model of the target blood vessel; and determine the blood flow reserve fraction of the target blood vessel based on the vascular parameters in the vascular model.

According to the above technical scheme, the blood flow reserve fraction of the target vessel is determined by obtaining the target ultrasound image and the target angiography image of the target vessel in the diastolic waveform-free interval. There is no significant difference between the coronary artery resistance in the diastolic waveform-free interval in the normal state and the coronary artery resistance in the maximum hyperemia state achieved by applying vasodilator drugs such as adenosine. Therefore, this scheme can achieve the measurement of the blood flow reserve fraction without the application of drugs. In addition, the present application can perform vascular reconstruction based on the target ultrasound image and the target angiography image, generate a vascular model of the target vessel, and determine the blood flow reserve fraction of the target vessel based on the vascular parameters in the vascular model. Therefore, this scheme can determine the blood flow reserve fraction of the target vessel by algorithms such as vascular reconstruction without pressure measurement. In summary, this scheme is a minimally invasive method for determining the blood flow reserve fraction, which can reduce the discomfort of the subject (i.e., the target object), and can reduce the consumables during the test, reduce the cost and time of the subject, and thus save the test cost of the subject. In addition, the duration of the waveform-free interval during diastole is relatively long, which is conducive to obtaining more ultrasound image data, so that a vascular model of the target blood vessel can be more accurately generated based on the ultrasound image data, which in turn is conducive to improving the calculation accuracy of the blood flow reserve fraction of the target blood vessel.

The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below.

BRIEF DESCRIPTION OF THE DRAWINGS

By describing the embodiments of the present application in more detail in conjunction with the accompanying drawings, the above and other purposes, features and advantages of the present application will become more apparent. The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application. In the accompanying drawings, the same reference numerals generally represent the same components or steps.

FIG1 is a schematic block diagram of a vascular imaging system according to an embodiment of the present application;

FIG2 is a schematic diagram showing a reconstructed blood vessel model according to an embodiment of the present application;

FIG3 is a schematic diagram showing a centerline of a target blood vessel according to an embodiment of the present application;

FIG4 is a schematic flow chart of a blood vessel imaging method according to an embodiment of the present application;

FIG5 is a schematic block diagram of a blood vessel imaging device according to an embodiment of the present application;

FIG6 shows a schematic block diagram of an electronic device according to an embodiment of the present application.

DETAILED DESCRIPTION

In order to make the purpose, technical solutions and advantages of the present application more obvious, the example embodiments according to the present application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application, and it should be understood that the present application is not limited to the example embodiments described herein. Based on the embodiments described in the present application, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present application.

The commonly used method for measuring FFR is to measure the ratio of the distal pressure of the lesion stenosis and the proximal arterial pressure under the maximum hyperemia state through a pressure interventional guidewire and a microcatheter to calculate FFR. However, the pressure guidewire is an invasive measurement and is used for a single time, which will increase the additional cost of the subject and prolong the interventional surgery time. And the pressure guidewire has a large measurement error for blood vessels with severe blockage and small lumens. In addition, during the measurement process, the maximum hyperemia condition is generally obtained by injecting vasodilators such as adenosine into the patient's body through a vein or artery. As mentioned above, vasodilators are harmful to the human body to a certain extent and are not suitable for some patient groups (such as liver and kidney dysfunction, drug allergy, etc.), and significantly increase the measurement time and complexity. In view of this, the present application provides a vascular imaging system, method, device, electronic device and computer-readable storage medium, which does not require the use of vasodilators and can accurately determine the blood flow reserve fraction of the target blood vessel in a short time. The vascular imaging system, method, device, electronic device and computer-readable storage medium are described below.

In order to solve the above technical problems, the present application provides a vascular imaging system. FIG1 shows a schematic block diagram of a vascular imaging system 100 according to an embodiment of the present application. As shown in FIG1 , the vascular imaging system 100 may include an ultrasound device 110 , an angiography device 120 , and a processing device 130 .

The ultrasound device 110 is used to collect an intravascular ultrasound image (which may be referred to as an ultrasound image) of a target object. The ultrasound device 110 is an intravascular ultrasound (IVUS) device. The ultrasound device 110 may include an ultrasound catheter, and an ultrasound transducer may be provided at the top of the ultrasound catheter. The ultrasound catheter in the ultrasound device 110 may be placed in a blood vessel, and the intravascular ultrasound image may be collected by the ultrasound transducer.

The angiography device 120 is used to collect coronary angiography images (which may be referred to as angiography images) of the target object. The angiography device 120 is a coronary angiography (CAG) device. When performing coronary angiography, a contrast agent may be injected into the coronary artery to make the blood vessel appear under X-rays. The angiography device 120 may emit X-rays to collect corresponding coronary angiography images. Optionally, the blood vessel may also be replaced with other blood vessels other than the coronary artery, and the implementation method is similar to that of the coronary artery, which will not be described in detail here.

The processing device 130 is connected to the ultrasound device 110 and the angiography device 120, respectively. The processing device 130 can be used to perform the following operations: determine the diastolic waveform-free interval in the cardiac cycle of the target object. Obtain a target ultrasound image and a target angiography image of the target blood vessel of the target object in the diastolic waveform-free interval from the images respectively acquired by the ultrasound device and the angiography device. Perform blood vessel reconstruction based on the target ultrasound image and the target angiography image to generate a blood vessel model of the target blood vessel. Determine the blood flow reserve fraction of the target blood vessel based on the blood vessel parameters in the blood vessel model.

It can be understood that the diastolic waveform-free interval refers to the diastolic phase of the cardiac cycle when the resting coronary artery resistance reaches its minimum. And it is a relatively constant period. When the blood vessels are kept in a normal state (i.e., without the use of vasodilators), the coronary artery resistance during the diastolic waveform-free interval is compared with the coronary artery resistance when the blood vessels reach the maximum hyperemia state through the use of vasodilators such as adenosine. There is no significant difference between the two. During the diastolic waveform-free interval, the blood flow and pressure in the blood vessels are linearly related, and the rise and fall of the pressure value can directly reflect the changes in blood flow, and then reflect the true physiological vascular stenosis. Therefore, during the diastolic waveform-free interval, the coronary artery resistance of the target blood vessel can be directly measured without the need to inject vasodilators into the target blood vessel.

Optionally, the method for determining the diastolic waveform-free interval in the cardiac cycle can adopt any existing or future developed method. In one embodiment, the diastolic waveform-free interval can be determined in the cardiac cycle based on empirical values. For example, it can be determined that the starting time of the diastolic waveform-free interval is 112 ms after the start of the diastolic period, and the duration of the diastolic waveform-free interval is 354 ms. In another embodiment, the diastolic waveform-free interval can be determined in the cardiac cycle based on the electrocardiographic signal on the electrocardiogram (ECG) of the target object. The specific determination method is described below. For different target objects, the time period occupied by the diastolic waveform-free interval in the entire cardiac cycle can be the same or different. Optionally, the current target object can be tested in advance to determine the time period occupied by its diastolic waveform-free interval in the entire cardiac cycle. Subsequently, the current target object can be imaged by blood vessels, and at this time, based on the results of the previous test, it can be determined which images of the acquired intravascular ultrasound images and coronary angiography images are acquired during the diastolic waveform-free interval. Optionally, during vascular imaging of the current target object, it is also possible to determine in real time which period of time the diastolic waveform-free interval is in each cardiac cycle, and then determine in real time which intravascular ultrasound images and coronary angiography images are acquired during the diastolic waveform-free interval.

The processing device 130 can respectively obtain a target ultrasound image and a target angiography image of a target blood vessel of the target object in a diastolic waveform-free interval from the images acquired by the ultrasound device 110 and the angiography device 120 .

Optionally, the target blood vessel may be any blood vessel in the target subject's body for which FFR needs to be calculated. The present application does not limit the location, blood vessel type, etc. of the target blood vessel.

Optionally, the target ultrasound image and the target contrast image can be directly acquired by corresponding acquisition devices (e.g., ultrasound device 110 and contrast device 120), or can be acquired by performing image preprocessing on the acquired ultrasound image and contrast image. Image preprocessing can include operations such as mean filtering. In some embodiments, the acquisition of the target ultrasound image and the target contrast image can be completed simultaneously. Alternatively, the target ultrasound image and the target contrast image can also be acquired asynchronously. This application does not limit this.

Optionally, when the ultrasound device 110 acquires an ultrasound image, the ultrasound catheter inserted into the blood vessel can be withdrawn, and the ultrasound transducer installed at the top of the ultrasound catheter can be used to acquire and display the ultrasound image of the target blood vessel in real time, that is, the cross-sectional image of the target blood vessel. The ultrasound image acquired by the ultrasound device 110 can clearly display information such as the thickness of the blood vessel wall structure, the size and shape of the lumen, etc. Therefore, by acquiring the target ultrasound image of the target blood vessel, the cross-sectional characteristics of the target blood vessel can be accurately determined.

The number of target ultrasound images can be selected according to actual needs. For any target blood vessel, the more ultrasound images corresponding to the target blood vessel, the more the blood vessel model obtained in the subsequent blood vessel reconstruction can truly reflect the situation of the target blood vessel. In some embodiments, the target ultrasound image of the target blood vessel can be obtained by uniformly withdrawing the ultrasound catheter inserted into the blood vessel. In this embodiment, the number of target ultrasound images obtained can be adjusted by adjusting the withdrawal speed of the ultrasound catheter and/or the acquisition frequency of the ultrasound transducer. Optionally, the target ultrasound image can be obtained by high-speed withdrawal and high-frame rate acquisition. That is, the ultrasound device 110 can be used to collect ultrasound images at a higher withdrawal speed and a higher imaging frame rate, which is conducive to ensuring that the acquisition of the ultrasound image of the target blood vessel is completed as soon as possible, shortening the acquisition time, and is conducive to obtaining more target ultrasound images to more accurately determine the real target blood vessel structure. The above-mentioned higher withdrawal speed can be, for example, 3 millimeters per second (mm/s), 6 mm/s or 9 mm/s, and the above-mentioned higher imaging frame rate can be, for example, 60 frames per second (frames/s) or 90 frames/s.

Optionally, the imaging device 120 may be an X-ray imaging machine, a CT scanner, etc. This application is not limited thereto. Optionally, the number of target imaging images is at least two frames. Each of the at least two frames of target imaging images has a different imaging angle. The difference in imaging angles between any two frames of target imaging images in the at least two frames of target imaging images satisfies an angle difference condition. The angle difference condition is that the difference in imaging angles between the two frames of target imaging images is between [30°, 150°] In a specific embodiment, the number of target angiography images is two, and the difference between the angiography angles of the two target angiography images is 60°. In this embodiment, by making each target angiography image in the target angiography image have a different angiography angle, it is helpful to provide a more accurate basis for the subsequent vascular reconstruction step.

After acquiring the target ultrasound image and the target contrast image, the processing device 130 may perform blood vessel reconstruction based on the target ultrasound image and the target contrast image to generate a blood vessel model of the target blood vessel.

It can be understood that the target angiography image can provide the retraction trajectory of the ultrasound catheter and the geometric information of the long axis direction of the target blood vessel and the spatial position of the cross section of the blood vessel, and the target ultrasound image can provide the morphological structure of multiple cross sections of the target blood vessel. This embodiment facilitates accurate reconstruction of the three-dimensional structure of the target blood vessel by fusing the two. The specific reconstruction method is described in detail below.

In many commonly used marking periods of the cardiac cycle, for example, if the target ultrasound image is collected at the end of diastole of each cardiac cycle, the end of diastole of each cardiac cycle is short, and the number of target ultrasound images collected in each cardiac cycle is small, resulting in a large amount of data loss, so that the amount of data used to reconstruct the vascular model is small, and the reconstructed vascular model cannot truly reflect the situation of the target blood vessel. In an embodiment of the present application, the target ultrasound image is acquired during the waveform-free interval of the diastole. Compared with other cardiac periods such as the end of diastole, the echo-free interval is longer, so that the target ultrasound image can be collected in a longer period of each cardiac cycle, which is conducive to increasing the number of imaging of the target ultrasound image in each cardiac cycle, obtaining more vascular cross-sectional information of the target blood vessel, and then more truly reflecting the situation of the target blood vessel. At the same time, when the acquisition period of the target ultrasound image in each cardiac cycle is increased, the withdrawal speed of the ultrasound catheter can be increased while ensuring that the amount of target ultrasound image data is sufficient, which is conducive to further improving the image acquisition efficiency.

After obtaining the blood vessel model, the processing device 130 may determine the blood flow reserve fraction of the target blood vessel based on the blood vessel parameters in the blood vessel model.

Optionally, the vascular parameters may include characteristic data of each vascular cross section in the vascular model, such as cross-sectional diameter, cross-sectional area, etc. The vascular parameters may also include the length of a specific vascular segment in the vascular model, such as a stenotic vascular segment as shown below.

During the diastolic waveform-free interval, a new pressure index that can evaluate the degree of vascular stenosis without the use of vasodilator drugs can be obtained through pressure measurement: instantaneous wave-free ratio (iFR). iFR is defined as the mean pressure at the distal end of the stenosis during the diastolic waveform-free interval divided by the mean arterial pressure during the diastolic waveform-free interval. The diastolic waveform-free interval can be determined by an algorithm related to the calculation of iFR, or coronary flow reserve (cFR) derived from iFR, or diastolic hyperemia-free ratio (dFR) derived from iFR. The processing device 130 can perform vascular reconstruction based on the target ultrasound image and target angiography image collected during the diastolic waveform-free interval to generate a vascular model. After obtaining the vascular parameters in the vascular model, the blood flow reserve fraction of the target vessel can be determined based on the mean arterial pressure in the target vessel and the blood flow velocity in the target vessel. The specific determination method is described in detail below.

According to the above technical scheme, the blood flow reserve fraction of the target vessel is determined by obtaining the target ultrasound image and the target angiography image of the target vessel in the diastolic waveform-free interval. There is no significant difference between the coronary artery resistance in the diastolic waveform-free interval in the normal state and the coronary artery resistance in the maximum hyperemia state achieved by applying vasodilator drugs such as adenosine. Therefore, this scheme can achieve the measurement of the blood flow reserve fraction without the application of drugs. In addition, the present application can perform vascular reconstruction based on the target ultrasound image and the target angiography image, generate a vascular model of the target vessel, and determine the blood flow reserve fraction of the target vessel based on the vascular parameters in the vascular model. Therefore, this scheme can determine the blood flow reserve fraction of the target vessel by algorithms such as vascular reconstruction without pressure measurement. In summary, this scheme is a minimally invasive method for determining the blood flow reserve fraction, which can reduce the discomfort of the subject (i.e., the target object), and can reduce the consumables during the test, reduce the cost and time of the subject, and thus save the test cost of the subject. In addition, the duration of the waveform-free interval during diastole is relatively long, which is conducive to obtaining more ultrasound image data, so that a vascular model of the target blood vessel can be more accurately generated based on the ultrasound image data, which in turn is conducive to improving the calculation accuracy of the blood flow reserve fraction of the target blood vessel.

Exemplarily, the vascular imaging system further includes an electrocardiogram device for collecting an electrocardiogram signal of the target object, and the processing device 130 is connected to the electrocardiogram device. The processing device 130 determines the diastolic waveform-free interval in the cardiac cycle of the target object by: receiving the electrocardiogram signal of the target object from the electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal; The processing device 130 obtains a target ultrasound image of a target blood vessel of a target object in a diastolic waveform-free interval from the image acquired by the ultrasound device 110 in the following manner: based on the identified diastolic waveform-free interval, a target ultrasound image is selected from the intravascular ultrasound images acquired by the ultrasound device 110. The ultrasound device 110 and the electrocardiogram device synchronously acquire the intravascular ultrasound images and electrocardiogram signals corresponding to each other, and the ultrasound device continuously acquires the intravascular ultrasound images.

It can be understood that the ultrasound image of the target blood vessel can be acquired in one or more cardiac cycles. The target ultrasound image includes an ultrasound image acquired in the diastolic waveform-free interval of each cardiac cycle.

It can be understood that for different target objects, the time periods of the diastolic waveform-free intervals in the cardiac cycle of the target object may be different. For the same target object, the time periods of the diastolic waveform-free intervals in different cardiac cycles may also be different. Therefore, the diastolic waveform-free intervals in each cardiac cycle can be determined separately. Therefore, compared with using empirical values to determine the diastolic waveform-free interval in the cardiac cycle, determining the diastolic waveform-free interval based on the electrocardiogram signal is more helpful to ensure the accuracy of the determined blood flow reserve fraction. The specific method of identifying the diastolic waveform-free interval based on the electrocardiogram signal is described in detail below.

In this embodiment, the ECG signal and the ultrasound image are collected synchronously. For any cardiac cycle, the ultrasound device can collect multiple frames of ultrasound images in the cardiac cycle. Among the multiple frames of ultrasound images, only some of the ultrasound images may correspond to the diastolic waveform-free interval. In some embodiments, the multiple frames of ultrasound images correspond to different acquisition times. In this embodiment, the diastolic waveform-free interval of the current cardiac cycle can be identified according to the ECG signal. And according to the time period corresponding to the diastolic waveform-free interval, the ultrasound image corresponding to the time period is selected from the multiple frames of ultrasound images. The selected ultrasound image is the target ultrasound image. For example, if it is identified that the time period corresponding to the diastolic waveform-free interval of the current cardiac cycle is from the 230ms after the start of acquisition to the 600ms after the start of acquisition, the ultrasound image collected between the 230ms after the start of acquisition and the 600ms after the start of acquisition can be selected from the multiple frames of ultrasound images collected by the ultrasound device. The ultrasound image collected during this time period is the target ultrasound image.

In the above embodiment, by synchronously acquiring the ECG signal and the ultrasound image, and selecting the target ultrasound image from the ultrasound image using the diastolic waveform-free interval determined based on the ECG signal, it is helpful to ensure the accuracy of the vascular model generated based on the target ultrasound image, thereby further improving the calculation accuracy of the blood flow reserve fraction. At the same time, this embodiment continuously acquires ultrasound images, which helps to improve the imaging speed.

Exemplarily, the vascular imaging system also includes an electrocardiogram device for collecting electrocardiogram signals of the target object, and the processing device is connected to the electrocardiogram device. The processing device 130 determines the diastolic waveform-free interval within the cardiac cycle of the target object in the following manner: receiving the electrocardiogram signal of the target object from the electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal. The processing device 130 is also used to: when the start moment of the diastolic waveform-free interval is identified, control the ultrasound device 110 to start collecting intravascular ultrasound images; when the end moment of the diastolic waveform-free interval is identified, control the ultrasound device 110 to stop collecting intravascular ultrasound images. The processing device 130 obtains a target ultrasound image of the target blood vessel of the target object within the diastolic waveform-free interval from the image collected by the ultrasound device 110 in the following manner: obtain the intravascular ultrasound image collected by the ultrasound device 110 as the target ultrasound image.

The ECG signal can be acquired in real time through any existing or future developed ECG device. It can be understood that each cardiac cycle corresponds to a continuous ECG signal. The diastolic waveform-free interval in the corresponding cardiac cycle can be determined based on the ECG signal. Optionally, the start time of the diastolic waveform-free interval can correspond to a specific data point on the ECG signal. The data point can be referred to as the first data point. Similarly, the end time of the diastolic waveform-free interval can also correspond to a specific data point in the ECG. The data point can be referred to as the second data point. In one embodiment, when the first data point is identified, the ultrasound device 110 can be controlled to start collecting ultrasound images. When the second data point is identified, the ultrasound device 110 is controlled to stop collecting ultrasound images. Thus, the ultrasound device 110 can be controlled to collect enough target ultrasound images within the diastolic waveform-free interval. The specific method for identifying the diastolic waveform-free interval based on the ECG signal is described in detail below.

As shown above, during the withdrawal of the ultrasound catheter in the blood vessel, the ultrasound transducer at the top of the ultrasound catheter is used to collect the intravascular ultrasound image of the blood vessel. In the description herein, controlling the ultrasound device 110 to start collecting images may refer to controlling the ultrasound catheter placed in the blood vessel to start withdrawing and collecting ultrasound images. Controlling the ultrasound device 110 to stop collecting ultrasound images may refer to controlling the ultrasound catheter placed in the blood vessel to stop withdrawing and stop collecting ultrasound images.

The above technical solution is based on the ECG signal triggering ultrasound equipment to collect ultrasound images of the target blood vessels. Therefore, the solution only collects ultrasound images during the diastolic waveform-free interval in the cardiac cycle, and does not collect ultrasound images during other periods (such as the systolic period) except the diastolic waveform-free interval in the cardiac cycle. Compared with the method of continuously collecting ultrasound images, the solution is conducive to preventing the loss of intravascular ultrasound images corresponding to other periods except the diastolic waveform-free interval, and can obtain relatively complete target blood vessel spatial geometric information, which is conducive to improving calculation accuracy. At the same time, the solution can minimize the collection of useless ultrasound images (i.e., ultrasound images collected during periods other than the diastolic waveform-free interval), which is conducive to improving the utilization rate of ultrasound images and reducing data redundancy. Preferably, the above-mentioned triggered ultrasound image acquisition scheme can be mainly applied to a vascular imaging system that can realize high-speed retracement and high frame rate acquisition. In such a vascular imaging system, the above-mentioned triggered ultrasound image acquisition scheme is relatively feasible.

Exemplarily, the vascular imaging system also includes an electrocardiogram device for collecting electrocardiogram signals of the target object, and the processing device is connected to the electrocardiogram device. The processing device 130 determines the diastolic waveform-free interval in the cardiac cycle of the target object in the following manner: receiving the electrocardiogram signal of the target object from the electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal. The processing device 130 obtains a target angiography image of the target blood vessel of the target object in the diastolic waveform-free interval from the image collected by the angiography device 120 in the following manner: based on the identified diastolic waveform-free interval, at least two frames of candidate coronary angiography images of different angiography angles are selected from the coronary angiography images collected by the angiography device 120 as the target angiography image; wherein the candidate coronary angiography image is a coronary angiography image collected by the angiography device in the diastolic waveform-free interval. The angiography device and the electrocardiogram device synchronously collect their respective corresponding coronary angiography images and electrocardiogram signals, and the angiography device continuously collects coronary angiography images.

As described above, during a cardiac cycle, the pressure and volume of the blood vessel will change periodically. Therefore, in order to ensure the accuracy of the geometric information of the retraction trajectory of the ultrasonic catheter and the long axis direction of the target blood vessel determined based on the target angiography image when generating the blood vessel model, the angiography image of the diastolic waveform-free interval can be obtained as the target angiography image. In this embodiment, the electrocardiogram signal and the angiography image are collected synchronously. In a specific embodiment, after the acquisition is completed, the diastolic waveform-free interval in each cardiac cycle can be determined based on the electrocardiogram corresponding to each cardiac cycle. Then, from all the angiography images collected by the angiography device, the angiography image corresponding to the diastolic waveform-free interval is selected as the candidate coronary angiography image. Finally, at least two frames of angiography images with different angiography angles can be selected from the candidate angiography images as the target angiography images. In this embodiment, the difference in the angiography angle between any two frames of the target angiography images in at least two frames satisfies the angle difference condition. The angle difference condition has been described in detail above. For the sake of brevity, it will not be repeated here.

The above embodiment synchronously acquires the ECG signal and the angiography image, and selects the target angiography image from the angiography image using the diastolic waveform-free interval determined based on the ECG signal, which helps to ensure the accuracy of the vascular model generated based on the target angiography image, thereby helping to further improve the calculation accuracy of the blood flow reserve fraction.

Exemplarily, the vascular imaging system further includes an electrocardiogram device for collecting electrocardiogram signals of the target object, and the processing device 130 is connected to the electrocardiogram device. The processing device 130 determines the diastolic waveform-free interval in the cardiac cycle of the target object in the following manner: receiving the electrocardiogram signal of the target object from the electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal. The processing device 130 is also used to: when the start time of the diastolic waveform-free interval is identified, control the angiography device 120 to start collecting coronary angiography images; when the end time of the diastolic waveform-free interval is identified, control the angiography device 120 to stop collecting coronary angiography images. The processing device 130 obtains a target angiography image of the target blood vessel of the target object in the diastolic waveform-free interval from the image collected by the angiography device 120 in the following manner: from the coronary angiography images collected by the angiography device 120, select at least two frames of coronary angiography images at different angiography angles as the target angiography images.

In this embodiment, all contrast images are acquired during the waveform-free interval of the diastolic period. Optionally, all contrast images acquired by the contrast device can be acquired as target contrast images. Alternatively, two contrast images with different contrast angles can be selected from the contrast images acquired by the contrast device as target contrast images. The difference in contrast angle between the two target contrast images meets the angle difference requirement. In this embodiment, only two contrast images are selected as target contrast images, which is beneficial to reduce the amount of data that needs to be calculated in the process of generating the vascular model, thereby further improving the calculation efficiency of FFR.

The above technical solution triggers the angiography device to collect angiography images of the target blood vessels based on the ECG signal. Therefore, the solution can minimize the collection of useless angiography images (i.e., angiography images collected during periods other than the diastolic waveform-free interval). It is beneficial to improve the utilization rate of contrast images and reduce data redundancy.

It should be noted that the above-mentioned selection of images based on the diastolic waveform-free interval and the acquisition of the target blood vessel image by the device based on the ECG signal triggering can be combined with each other to obtain the target ultrasound image and the target angiography image. It can include at least the following combinations:

1) When the beginning moment of the diastolic waveform-free interval is identified, the ultrasound device is controlled to start acquiring intravascular ultrasound images and the angiography device is controlled to start acquiring coronary angiography images; when the end moment of the diastolic waveform-free interval is identified, the ultrasound device is controlled to stop acquiring intravascular ultrasound images and the angiography device is controlled to stop acquiring coronary angiography images; the intravascular ultrasound image acquired by the ultrasound device is acquired as a target ultrasound image; and from the coronary angiography images acquired by the angiography device, at least two frames of coronary angiography images at different angiography angles are selected as target angiography images.

2) When the beginning moment of the diastolic waveform-free interval is identified, the ultrasound device is controlled to start acquiring the intravascular ultrasound image; when the ending moment of the diastolic waveform-free interval is identified, the ultrasound device is controlled to stop acquiring the intravascular ultrasound image, and the intravascular ultrasound image acquired by the ultrasound device is acquired as the target ultrasound image; based on the identified diastolic waveform-free interval, at least two frames of candidate coronary angiography images with different angiography angles are selected from the coronary angiography images acquired by the angiography device as the target angiography images.

3) Based on the identified diastolic waveform-free interval, a target ultrasound image is selected from the intravascular ultrasound images acquired by the ultrasound device; when the beginning moment of the diastolic waveform-free interval is identified, the angiography device is controlled to start acquiring coronary angiography images, and when the end moment of the diastolic waveform-free interval is identified, the angiography device is controlled to stop acquiring coronary angiography images, and at least two frames of coronary angiography images at different angiography angles are selected from the coronary angiography images acquired by the angiography device as target angiography images.

4) Based on the identified diastolic waveform-free interval, a target ultrasound image is selected from the intravascular ultrasound image acquired by the ultrasound device; based on the identified diastolic waveform-free interval, at least two frames of candidate coronary angiography images with different angiography angles are selected as target angiography images from the coronary angiography images acquired by the angiography device.

Exemplarily, the processing device 130 identifies the diastolic waveform-free interval based on the ECG signal in the following manner: calculating the instantaneous resistance at each moment in the cardiac cycle based on the waveform amplitude characteristics of the ECG signal. Determining the diastolic waveform-free interval based on the instantaneous resistance at each moment in the cardiac cycle.

It can be understood that by calculating the instantaneous resistance at each moment in the cardiac cycle, the hemodynamic changes of the target blood vessel in each cardiac cycle can be evaluated, and then the resistance index can be obtained. According to the resistance index at each moment, the period in the cardiac cycle when the resistance in the target blood vessel is the smallest and relatively stable can be identified. In some embodiments (such as the above-mentioned embodiment of synchronously acquiring the ECG signal and the ultrasound image or the contrast image), after synchronously acquiring the ECG signal and the ultrasound image or the contrast image, the instantaneous resistance at each moment in the cardiac cycle can be calculated based on the waveform amplitude characteristics of the ECG signal. And according to the instantaneous resistance at each moment, the period in the cardiac cycle when the resistance in the target blood vessel is the smallest and relatively stable (i.e., the diastolic waveform-free interval) is determined.

In other embodiments (such as the above-mentioned embodiment of triggering an ultrasound device based on an ECG signal to collect an ultrasound image or angiography image of a target blood vessel), the ECG signal of the target object may be collected in advance before collecting the image (ultrasound image or angiography image), and the characteristic information of the diastolic waveform-free interval may be determined based on the ECG signal. The characteristic information may be the resistance index corresponding to the diastolic waveform-free interval of the target object (hereinafter referred to as the resistance index threshold), or the start time and end time of the diastolic waveform-free interval in each cardiac cycle. In a specific embodiment, the ECG signals of multiple cardiac cycles of the target object may be collected in advance. For each cardiac cycle, the instantaneous resistance at each moment in the cardiac cycle is calculated based on the waveform amplitude characteristics of the ECG signal corresponding to the cardiac cycle. And according to the instantaneous resistance at each moment, the period (i.e., the diastolic waveform-free interval) when the resistance in the target blood vessel is the smallest and relatively stable in the cardiac cycle is determined. Then, based on the size of the minimum resistance corresponding to each of the multiple cardiac cycles, the resistance index corresponding to the largest minimum resistance in the multiple cardiac cycles is determined as the resistance index threshold. When the ultrasound device is triggered based on the ECG signal to collect ultrasound images or angiography images of the target blood vessels, the instantaneous resistance at each moment in the cardiac cycle can be calculated based on the waveform amplitude characteristics of the ECG signal. When the resistance index corresponding to the instantaneous resistance at the current moment is less than or equal to the resistance index threshold, the current moment can be considered to be the beginning of the waveform-free interval of the diastole in the cardiac cycle. Continue to calculate the instantaneous resistance at each moment in the cardiac cycle based on the waveform amplitude characteristics of the ECG signal. When the resistance index corresponding to the instantaneous resistance at the current moment is greater than the resistance index threshold, the current moment can be considered to be the beginning of the waveform-free interval of the diastole in the cardiac cycle. When the force index threshold is reached, the current moment can be considered as the end moment of the diastolic waveform-free interval in the cardiac cycle.

The above technical solution calculates the instantaneous resistance at each moment in the cardiac cycle based on the electrocardiogram signal, and determines the diastolic waveform-free interval in the cardiac cycle according to the instantaneous resistance at each moment. This solution helps to more accurately determine the diastolic waveform-free interval in the cardiac cycle.

Exemplarily, the processing device performs blood vessel reconstruction based on the target ultrasound image and the target contrast image to generate a blood vessel model of the target blood vessel in the following manner: identifying the centerline of the target blood vessel from the target contrast image; identifying the lumen contour of the target blood vessel from the target ultrasound image; and aligning and reconstructing the lumen contour along the centerline to obtain a blood vessel model.

As shown above, the target angiography image can provide the direction of the blood vessel, that is, the retraction trajectory of the ultrasound catheter. Optionally, the retraction trajectory of the ultrasound catheter can be determined based on the target angiography image, and the retraction trajectory can be used as the centerline of the target blood vessel. The specific method of identifying the centerline of the target blood vessel from the target angiography image is described in detail below.

Optionally, the lumen contour of the target blood vessel can be identified from the target ultrasound image using any existing or future developed neural network model for segmenting images. For example, the neural network model can include one or more of the following neural network models: U-Net, Fully Convolutional Networks (FCN), Deep Convolutional Encoder-Decoder Structure for Image Segmentation (SegNet), etc. In a specific embodiment, the U-Net model can be selected, and the annotated ultrasound image can be used as training data so that the U-Net model can automatically segment the lumen contour of the blood vessel in the ultrasound image. In some embodiments, after the lumen contour of the target blood vessel is obtained using the neural network model, the result can be output, and feedback information (such as confirmation information or modification information) from the user on the result can be received. According to the feedback information, the lumen contour of the target blood vessel in the current ultrasound image is confirmed or corrected, thereby completing the processing of the target ultrasound image.

Fig. 2 shows a schematic diagram of a reconstructed blood vessel model according to an embodiment of the present application. As shown in Fig. 2, the reconstruction process includes reconstruction of a target blood vessel three-dimensional path, acquisition and processing of a target ultrasound image, and registration reconstruction of a target angiography image and a target ultrasound image.

The reconstruction of the three-dimensional path of the target blood vessel may include: synchronously acquiring two frames of target angiography images in the diastolic waveform-free interval of the cardiac cycle through the electrocardiogram signal, determining the withdrawal path (i.e., the center line of the target blood vessel) based on the two frames of target angiography images, and completing the three-dimensional reconstruction of the withdrawal path using the withdrawal paths corresponding to the two frames of target angiography images.

The acquisition and processing of the target ultrasound image includes: triggering the acquisition of ultrasound images based on the waveform-free interval of the diastolic period of the electrocardiogram signal in the cardiac cycle. The acquired ultrasound image is the target ultrasound image. After the acquisition is completed, the lumen contour in each target ultrasound image is identified.

The registration and reconstruction of the target angiography image and the target ultrasound image includes: registering the lumen contours in each target ultrasound image with the three-dimensional retrieval path, determining the position of the lumen contours in each frame of the target ultrasound image, and then fitting each lumen contour using surface fitting to complete the three-dimensional reconstruction of the vascular model of the target blood vessel.

Exemplarily, the processing device is also used to: identify side branches of a target blood vessel from a target ultrasound image; and when registering and reconstructing the lumen contour along the center line to obtain a blood vessel model, register and reconstruct the side branches together with the lumen contour along the center line.

In a specific implementation, the side branch detection of the target blood vessel can be implemented based on a convolutional neural network, or based on a Transformer model, or based on a deep learning algorithm of both a convolutional neural network and a Transformer model. The above is only an example. In actual implementation, there may be other detection methods, which are not limited in this application. It can be understood that due to the existence of side branches in the target blood vessel, it may affect the reconstruction of the vascular model of the target blood vessel and the calculation of the blood flow reserve fraction. This embodiment helps to further improve the calculation accuracy of the blood flow reserve fraction by identifying the side branches of the target blood vessel.

After determining the centerline of the target blood vessel and the lumen contour of the target blood vessel in each frame of the target ultrasound image, registration reconstruction can be performed. Registration reconstruction may include the following operations. Using the distance mapping method, the lumen contour of each frame of the target ultrasound image is inserted on the centerline of the target blood vessel, thereby determining the position of the lumen contour in each frame of the target ultrasound image. Then, surface fitting is used to fit each lumen contour to complete the three-dimensional reconstruction of the vascular model of the target blood vessel. In a specific embodiment, a non-uniform rational B-spline curve (NURBS) can be used to fit each lumen contour, and the fitted contour can be reconstructed. The combined result is smoothed to complete the three-dimensional reconstruction of the vascular model of the target blood vessel. In the embodiment of identifying the side branch, when the lumen contour is registered and reconstructed along the center line, the side branch can be registered and reconstructed together with the lumen contour along the center line. The side branch itself is connected to the lumen contour, and the positional relationship between the two is fixed. Therefore, by identifying the side branch, it is possible to obtain information such as the position of the side branch on the lumen contour and the shape of the side branch. Subsequently, the side branch can be registered and reconstructed together with the lumen contour.

The above technical solution uses the center line of the target blood vessel confirmed by the target angiography image and the lumen contour in the target ultrasound image to complete the reconstruction of the blood vessel model. This embodiment is conducive to accurately reconstructing the blood vessel model of the target blood vessel, thereby ensuring the calculation accuracy of the blood flow reserve fraction.

Exemplarily, the ultrasound device 110 includes an ultrasound catheter and an ultrasound transducer disposed on the ultrasound catheter; the ultrasound transducer is used to collect an intravascular ultrasound image of the target object during the retraction of the ultrasound catheter; the processing device 130 identifies the centerline of the target blood vessel from the target angiography image in the following manner: for each frame of coronary angiography image in the target angiography image, determine the retraction start point and the retraction end point of the ultrasound catheter in the coronary angiography image. Based on the retraction start point and the retraction end point, extract the retraction path of the ultrasound catheter from the coronary angiography image. Based on the retraction path corresponding to each frame of coronary angiography image in the target angiography image, generate a three-dimensional retraction path of the ultrasound catheter. Wherein, the centerline of the target blood vessel is represented by a three-dimensional retraction path.

Optionally, the target angiography image includes at least two frames of coronary angiography images at different angiography angles, and the withdrawal paths corresponding to the coronary angiography images at each angiography angle can be determined respectively, and the three-dimensional withdrawal path of the ultrasound catheter is generated by fusing the withdrawal paths at different angiography angles.

Optionally, the retraction start point and the retraction end point of the ultrasound catheter may be automatically determined in the target angiography image by the processing device 130. Alternatively, the retraction start point and the retraction end point of the ultrasound catheter may be selected according to user needs. For example, the retraction start point and the retraction end point of the ultrasound catheter may be manually selected by the user in the target angiography image.

In the above embodiment, the retraction path of the ultrasound catheter is used as the centerline of the target blood vessel. Therefore, when identifying the centerline of the target blood vessel based on the target angiography image, only the retraction path in the target angiography image needs to be extracted. This helps to simplify the algorithm complexity.

Exemplarily, the processing device 130 extracts the retraction path of the ultrasound catheter from the coronary angiography image based on the retraction starting point and the retraction end point in the following manner: preprocessing the coronary angiography image to obtain a preprocessed coronary angiography image. The preprocessing includes filtering and/or histogram enhancement processing. The target blood vessel in the preprocessed coronary angiography image is enhanced by vessel boundary enhancement to obtain a boundary-enhanced coronary angiography image. The boundary-enhanced coronary angiography image is binarized and morphologically denoised to obtain a processed coronary angiography image. The shortest path starting from the retraction starting point and ending at the retraction end point is extracted from the processed coronary angiography image as the retraction path.

FIG3 shows a schematic diagram of identifying the centerline of a target blood vessel according to an embodiment of the present application. As shown in FIG3 , the method for identifying the centerline of a target blood vessel may include the following steps a, b, c, d, and e (the angiography images corresponding to each step are identified by the same symbols in FIG2 ). a. Obtain the starting point and end point of the target blood vessel for ultrasound imaging. The starting point (equivalent to the withdrawal starting point above) and the end point (equivalent to the withdrawal end point above) of the target blood vessel may be manually selected by the user in the target angiography image. For example, the developing point of the ultrasound catheter may be used as the starting point, and the angiography guide catheter used to collect the target angiography image may be used as the end point. In this embodiment, the starting point is point A in the figure, and the end point is point B in the figure. b. Perform image preprocessing on the target angiography image. The preprocessing may include filtering and/or histogram enhancement processing. The filtering may be implemented in any filtering manner. For example, the target angiography image may be average filtered and histogram enhanced. c. Perform vascular boundary enhancement on the target blood vessel in the target angiography image. For example, a multi-scale Hessian matrix may be used to perform vascular boundary enhancement on the target blood vessel in the target angiography image. d. Perform morphological processing on the target angiography image. In one embodiment, the target angiography image may be first subjected to image binarization processing, and the grayscale value of the area corresponding to the blood vessel in the target angiography image is set to 255, and the grayscale value of the area other than the blood vessel is set to 0. Then, the target angiography image is subjected to morphological denoising processing to highlight the blood vessels in the target angiography image, thereby removing interference from other non-vascular areas. e. Extract the shortest path. In this step, the shortest path may be extracted based on the starting point and end point of the target blood vessel, and the target angiography image enhanced by steps b, c, and d, using an existing shortest path algorithm such as the Dijkstra algorithm. The shortest path is the withdrawal path of the ultrasonic catheter in the target blood vessel (i.e., the center line of the target blood vessel).

According to the above technical solution, by sequentially performing preprocessing, blood vessel boundary enhancement, image binarization and morphological denoising on the contrast image, it is helpful to improve the image quality of the contrast image, thereby facilitating accurate determination of the center line of the target blood vessel.

Exemplarily, the vascular parameters include the cross-sectional area corresponding to each point of the long axis of the vascular model. The processing device 130 determines the blood flow reserve fraction of the target vessel based on the vascular parameters in the vascular model in the following manner: based on the size of the cross-sectional area corresponding to each point of the long axis of the vascular model, determine the stenotic vessel segment and the normal vessel segment in the vascular model; obtain the mean arterial pressure of the target vessel; based on the cross-sectional area corresponding to the stenotic vessel segment, the cross-sectional area corresponding to the normal vessel segment and the length of the stenotic vessel segment, determine the pressure difference corresponding to the stenotic vessel segment; based on the mean arterial pressure and the pressure difference, determine the blood flow reserve fraction of the target vessel.

Optionally, based on the size of the cross-sectional area corresponding to each point of the long axis of the vascular model, the mutation point on the long axis corresponding to the mutation of the cross-sectional area can be identified along the long axis. It can be understood that the diameter of the stenotic vascular segment is smaller than that of the normal vascular segment. In one embodiment, when identifying the cross-sectional area along the long axis, if the cross-sectional area corresponding to the current long axis point changes greatly relative to the cross-sectional area corresponding to the previous long axis point, for example, the cross-sectional area corresponding to the current long axis point is smaller than the cross-sectional area corresponding to the previous long axis point and the difference between the two is greater than the first preset difference threshold, then the current long axis point can be considered as a mutation point. Continue to identify the cross-sectional area along the long axis. When a mutation point is identified again, for example, the cross-sectional area corresponding to the current long axis point is larger than the cross-sectional area corresponding to the previous long axis point and the difference between the two is greater than the second preset difference threshold, then the vascular segment between the two mutation points can be regarded as a stenotic vascular segment. The first preset difference threshold and the second preset difference threshold can be equal or different.

Optionally, the size of the cross-sectional area corresponding to each point on the long axis of the vascular model can be compared with a preset area threshold. If the cross-sectional area of a vascular segment in the vascular model is smaller than the preset area threshold, the vascular segment is a stenotic vascular segment. Otherwise, the vascular segment is a normal vascular segment. It can be understood that the preset area threshold can be determined according to the target object and the target blood vessel type. Different target objects and different types of target blood vessels can have different preset area thresholds.

Optionally, the mean arterial pressure of the target blood vessel can be measured based on any existing or future developed in vitro or in vivo pressure measurement method, which is not limited in the present application.

It can be understood that FFR refers to the ratio of the maximum blood flow in the myocardium when the stenotic coronary artery is supplied with blood to the maximum blood flow that the myocardium can obtain during the normal blood flow supply of the same coronary artery. Since the myocardial blood flow can be defined as: myocardial tissue blood flow = perfusion pressure / intramyocardial microcirculatory resistance, that is, Q = P/R, FFR can be calculated by the following formula:

Where _Pd represents the distal pressure of the stenotic vessel segment. _Pa represents the proximal pressure of the stenotic vessel segment. The proximal pressure of the stenotic vessel segment is roughly equal to the pressure of the normal vessel segment, so the proximal pressure of the stenotic vessel segment can be used to represent the pressure of the normal vessel segment. _Pv represents the venous pressure. _Rs represents the myocardial microcirculatory resistance of the stenotic vessel segment. _RN represents the myocardial microcirculatory resistance of the normal vessel segment. As mentioned above, there is no significant difference between the coronary artery resistance at the maximum hyperemia state achieved by vasodilators and the coronary artery resistance during the diastolic waveform-free interval under normal conditions (i.e., no vasodilators are used). Therefore, the myocardial microcirculatory resistance during the diastolic waveform-free interval can be small enough to be ignored and is constant. Based on this, vascular reconstruction is performed, where the venous pressure _Pv is also close to 0, then the calculation formula for FFR can be simplified to:

Therefore, FFR can be calculated by dividing the distal pressure of the stenotic vessel segment during the diastolic waveform-free interval by the mean arterial pressure during the diastolic waveform-free interval.

It can be understood that the distal pressure of the stenotic vessel segment can be obtained by calculating the pressure difference between the stenotic vessel segment and the normal vessel segment. That is, _Pd = _Pa -ΔP. And the pressure difference can be calculated by a simplified fluid dynamics equation, that is, ΔP = _fvV + _fsV2 . Among ^them , V represents the blood flow velocity in the target vessel. _fv represents the pressure loss coefficient caused by viscous friction. _fs represents the local pressure loss coefficient caused by blood flow separation. Both _fv and _fs are related to the length of the stenotic vessel segment and the cross-sectional area corresponding to the stenotic vessel segment. The blood volume, the cross-sectional area corresponding to the normal blood vessel segment, the blood flow viscosity coefficient and the blood density. For example, the following relationship exists:

Where _As represents the cross-sectional area corresponding to the stenotic blood vessel segment. _An represents the cross-sectional area corresponding to the normal blood vessel segment. L represents the length of the stenotic blood vessel segment. μ represents the blood viscosity coefficient, and ρ represents the blood density.

It can be understood that _As , _An and L can all be determined by the generated blood vessel model. μ and ρ can both be determined based on empirical values.

Optionally, the blood flow rate in the target blood vessel can be calculated based on the transit time of the contrast agent in the target angiography image from one position to another. It is understood that in the process of angiography imaging the target blood vessel, it is necessary to inject the contrast agent into the target blood vessel to display the blood flow in the target blood vessel. In one embodiment, any two frames of the target angiography image in which the contrast agent appears can be selected, and the blood flow rate in the target blood vessel can be calculated based on the moving distance of the contrast agent in the two frames and the interval between the acquisition time of the two frames.

Alternatively, the blood flow rate in the target vessel can be calculated by a frame counting method (e.g., TIMI frame counting method). In this embodiment, the contrast image includes all images from the first image taken to show the appearance of contrast agent in the target vessel to the contrast agent moving to the other end of the target vessel. After the contrast agent is injected into the target vessel, the target vessel can be imaged by contrast imaging at a preset imaging frequency to obtain multiple frames of contrast images. The blood flow rate in the target vessel can be calculated by the number of contrast images and the preset imaging frequency.

Therefore, after determining the pressure difference corresponding to the stenotic vessel segment, the distal pressure of the stenotic vessel segment can be further determined. The distal pressure of the stenotic vessel segment and the mean arterial pressure are used to calculate the FFR. The specific calculation method has been described in detail above. For the sake of brevity, it will not be repeated here.

The above technical solution calculates the blood flow reserve fraction of the target blood vessel by using the distal pressure of the narrowed blood vessel segment and the mean arterial pressure, which is conducive to improving the calculation efficiency of the blood flow reserve fraction and ensuring good accuracy.

According to another aspect of the present application, a vascular imaging method is also provided. Figure 4 shows a schematic flow chart of a vascular imaging method according to an embodiment of the present application. As shown in Figure 4, the method 400 may include the following steps S410, S420, S430, and S440.

In step S410, a diastolic waveform-free interval in the cardiac cycle of the target subject is determined.

In step S420, a target ultrasound image and a target angiography image of a target blood vessel of the target object in a diastolic waveform-free interval are respectively acquired from images acquired by the ultrasound device and the angiography device.

In step S430, blood vessel reconstruction is performed based on the target ultrasound image and the target angiography image to generate a blood vessel model of the target blood vessel.

In step S440 , the blood flow reserve fraction of the target blood vessel is determined based on the blood vessel parameters in the blood vessel model.

Exemplarily, determining the diastolic waveform-free interval in the cardiac cycle of the target object may include the following steps: receiving an electrocardiogram signal of the target object from an electrocardiogram device, and identifying the diastolic waveform-free interval based on the electrocardiogram signal.

The method 400 may further include the following steps: when the start time of the diastolic waveform-free interval is identified, the ultrasound device is controlled to start acquiring intravascular ultrasound images. When the end time of the diastolic waveform-free interval is identified, the ultrasound device is controlled to stop acquiring intravascular ultrasound images.

Acquiring a target ultrasound image of a target blood vessel of a target object in a diastolic waveform-free interval from an image acquired by an ultrasound device may include the following steps: acquiring an intravascular ultrasound image acquired by the ultrasound device as a target ultrasound image.

Exemplarily, determining the diastolic waveform-free interval in the cardiac cycle of the target object may include the following steps: receiving an electrocardiogram signal of the target object from an electrocardiogram device, and identifying the diastolic waveform-free interval based on the electrocardiogram signal.

Acquiring a target ultrasound image of a target blood vessel of a target object in a diastolic waveform-free interval from an image acquired by an ultrasound device may include the following steps: based on the identified diastolic waveform-free interval, selecting a target ultrasound image from an intravascular ultrasound image acquired by the ultrasound device, wherein the ultrasound device and the electrocardiogram device synchronously acquire the intravascular ultrasound image and electrocardiogram signal corresponding to each other, and the ultrasound device continuously acquires the intravascular ultrasound image.

Exemplarily, determining the diastolic waveform-free interval in the cardiac cycle of the target object may include the following steps: receiving an electrocardiogram signal of the target object from an electrocardiogram device, and identifying the diastolic waveform-free interval based on the electrocardiogram signal.

The method 400 may further include the following steps: when the start time of the diastolic waveform-free interval is identified, the angiography device is controlled to start acquiring coronary angiography images. When the end time of the diastolic waveform-free interval is identified, the angiography device is controlled to stop acquiring coronary angiography images.

Obtaining a target angiography image of a target blood vessel of a target object during a waveform-free interval during diastole from an image acquired by an angiography device may include the following steps: selecting at least two frames of coronary angiography images at different angiography angles as target angiography images from among the coronary angiography images acquired by the angiography device.

Exemplarily, determining the diastolic waveform-free interval in the cardiac cycle of the target object may include the following steps: receiving an electrocardiogram signal of the target object from an electrocardiogram device, and identifying the diastolic waveform-free interval based on the electrocardiogram signal.

Acquiring a target angiography image of a target blood vessel of a target object in a diastolic waveform-free interval from an image acquired by an angiography device may include the following steps: based on the identified diastolic waveform-free interval, selecting at least two frames of candidate coronary angiography images of different angiography angles from the coronary angiography images acquired by the angiography device as target angiography images. The candidate coronary angiography images are coronary angiography images acquired by the angiography device in a diastolic waveform-free interval. The angiography device and the electrocardiogram device synchronously acquire their respective corresponding coronary angiography images and electrocardiogram signals, and the angiography device continuously acquires coronary angiography images.

Exemplarily, identifying the diastolic waveform-free interval based on the ECG signal may include the following steps: calculating the instantaneous resistance at each moment in the cardiac cycle based on the waveform amplitude characteristics of the ECG signal. Determining the diastolic waveform-free interval based on the instantaneous resistance at each moment in the cardiac cycle.

Exemplarily, performing blood vessel reconstruction based on the target ultrasound image and the target contrast image to generate a blood vessel model of the target blood vessel may include the following steps: identifying the centerline of the target blood vessel from the target contrast image. Identifying the lumen contour of the target blood vessel from the target ultrasound image. Registering and reconstructing the lumen contour along the centerline to obtain a blood vessel model.

Exemplarily, the method 400 may further include the following steps: identifying the side branches of the target blood vessel from the target ultrasound image, and registering and reconstructing the lumen contour along the centerline to obtain the blood vessel model, and registering and reconstructing the side branches together with the lumen contour along the centerline.

Exemplarily, the ultrasound device includes an ultrasound catheter and an ultrasound transducer disposed on the ultrasound catheter. The ultrasound transducer is used to collect an intravascular ultrasound image of the target object during the retraction of the ultrasound catheter. Identifying the centerline of the target blood vessel from the target angiography image may include the following steps: for each frame of coronary angiography image in the target angiography image, determining the retraction starting point and the retraction end point of the ultrasound catheter in the coronary angiography image. Based on the retraction starting point and the retraction end point, extracting the retraction path of the ultrasound catheter from the coronary angiography image. Based on the retraction path corresponding to each frame of coronary angiography image in the target angiography image, generate a three-dimensional retraction path of the ultrasound catheter. Wherein, the centerline of the target blood vessel is represented by a three-dimensional retraction path.

Exemplarily, extracting the retraction path of the ultrasound catheter from the coronary angiography image based on the retraction starting point and the retraction end point may include the following steps: preprocessing the coronary angiography image to obtain a preprocessed coronary angiography image. Preprocessing includes filtering and/or histogram enhancement processing. Performing vascular boundary enhancement on the target blood vessel in the preprocessed coronary angiography image to obtain a boundary-enhanced coronary angiography image. Performing image binarization and morphological denoising processing on the boundary-enhanced coronary angiography image to obtain a processed coronary angiography image. Extracting the shortest path starting from the retraction starting point and ending at the retraction end point from the processed coronary angiography image as the retraction path.

Exemplarily, the vascular parameters include the cross-sectional area corresponding to each point of the long axis of the vascular model. Determining the blood flow reserve fraction of the target vessel based on the vascular parameters in the vascular model may include the following steps: determining the stenotic vessel segment and the normal vessel segment in the vascular model based on the size of the cross-sectional area corresponding to each point of the long axis of the vascular model. Obtaining the mean arterial pressure of the target vessel. Determining the pressure difference corresponding to the stenotic vessel segment based on the cross-sectional area corresponding to the stenotic vessel segment, the cross-sectional area corresponding to the normal vessel segment, and the length of the stenotic vessel segment. Determining the blood flow reserve fraction of the target vessel based on the mean arterial pressure and the pressure difference.

According to another aspect of the present application, a vascular imaging device is also provided. FIG5 shows a schematic block diagram of a vascular imaging device according to an embodiment of the present application. As shown in FIG5 , the vascular imaging device 500 includes a first determination module 510 , an acquisition module 520 , a vascular reconstruction module 530 , and a second determination module 540 .

The first determination module 510 is used to determine the diastolic waveform-free interval in the cardiac cycle of the target object.

The acquisition module 520 is used to respectively acquire a target ultrasound image and a target angiography image of a target blood vessel of a target object in a diastolic waveform-free interval from images acquired by the ultrasound device and the angiography device respectively.

The blood vessel reconstruction module 530 is used to perform blood vessel reconstruction based on the target ultrasound image and the target angiography image to generate a blood vessel model of the target blood vessel.

The second determination module 540 is used to determine the blood flow reserve fraction of the target blood vessel based on the blood vessel parameters in the blood vessel model.

Exemplarily, the first determination module 510 includes: a first receiving submodule for receiving the ECG signal of the target object from the ECG device; a first identification submodule for identifying the diastolic waveform-free interval based on the ECG signal. The vascular imaging device also includes: a first control module for controlling the ultrasound device 500 to start acquiring intravascular ultrasound images when the start moment of the diastolic waveform-free interval is identified; a second control module for controlling the ultrasound device to stop acquiring intravascular ultrasound images when the end moment of the diastolic waveform-free interval is identified. The acquisition module 520 includes: a first acquisition submodule for acquiring the intravascular ultrasound image acquired by the ultrasound device as the target ultrasound image.

Exemplarily, the first determination module 510 includes: a second receiving submodule, for receiving an electrocardiogram signal of a target object from an electrocardiogram device; and a second identification submodule, for identifying a diastolic waveform-free interval based on the electrocardiogram signal. The acquisition module 520 includes: a first selection submodule, for selecting a target ultrasound image from an intravascular ultrasound image acquired by an ultrasound device based on the identified diastolic waveform-free interval. The ultrasound device and the electrocardiogram device synchronously acquire their respective corresponding intravascular ultrasound images and electrocardiogram signals. The ultrasound device continuously acquires intravascular ultrasound images.

Exemplarily, the first determination module 510 includes: a third receiving submodule for receiving the ECG signal of the target object from the ECG device; a third identification submodule for identifying the diastolic waveform-free interval based on the ECG signal. The vascular imaging device 500 also includes: a third control module for controlling the angiography device to start collecting coronary angiography images when the start time of the diastolic waveform-free interval is identified; a fourth control module for controlling the angiography device to stop collecting coronary angiography images when the end time of the diastolic waveform-free interval is identified. The acquisition module 520 includes: a second selection submodule for selecting at least two frames of angiography images at different angiography angles from the coronary angiography images collected by the angiography device as target angiography images.

Exemplarily, the first determination module 510 includes: a fourth receiving submodule, which is used to receive the ECG signal of the target object from the ECG device; and a fourth identification submodule, which is used to identify the diastolic waveform-free interval based on the ECG signal. The acquisition module 520 includes: a third selection submodule, which is used to select at least two frames of candidate coronary angiography images of different angiography angles from the coronary angiography images acquired by the angiography device as target angiography images based on the identified diastolic waveform-free interval. The candidate coronary angiography image is a coronary angiography image acquired by the angiography device during the diastolic waveform-free interval. The angiography device and the ECG device synchronously acquire their respective corresponding coronary angiography images and ECG signals, and the angiography device continuously acquires coronary angiography images.

Exemplarily, the first determination module 510 includes: a calculation submodule for calculating the instantaneous resistance at each moment in the cardiac cycle based on the waveform amplitude characteristics of the electrocardiogram signal; and a first determination submodule for determining the diastolic waveform-free interval based on the instantaneous resistance at each moment in the cardiac cycle.

Exemplarily, the vascular reconstruction module 530 includes: a fifth recognition submodule, used to identify the centerline of the target blood vessel from the target angiography image; a sixth recognition submodule, used to identify the lumen contour of the target blood vessel from the target ultrasound image; and a reconstruction submodule, used to align and reconstruct the lumen contour along the centerline to obtain a vascular model.

Exemplarily, the vascular reconstruction module 530 also includes: a seventh identification submodule, used to identify the side branches of the target blood vessel from the target ultrasound image before the reconstruction submodule aligns and reconstructs the lumen contour along the centerline to obtain the vascular model; the reconstruction submodule includes a reconstruction unit, used to align and reconstruct the side branches together with the lumen contour along the centerline.

Exemplarily, the ultrasound device includes an ultrasound catheter and an ultrasound transducer disposed on the ultrasound catheter. The ultrasound transducer is used to acquire an intravascular ultrasound image of the target object during the withdrawal of the ultrasound catheter. The fifth identification submodule includes: a determination unit, for determining, for each frame of the coronary angiography image in the target angiography image, the position of the ultrasound catheter in the coronary angiography image; A retracement start point and a retracement end point; an extraction unit, used to extract the retracement path of the ultrasound catheter from the coronary angiography image based on the retracement start point and the retracement end point; a generation unit, used to generate a three-dimensional retracement path of the ultrasound catheter based on the retracement path corresponding to each frame of the coronary angiography image in the target angiography image. The centerline of the target blood vessel is represented by the three-dimensional retracement path.

Exemplarily, the extraction unit includes: a preprocessing subunit, used to preprocess the coronary angiography image to obtain a preprocessed coronary angiography image, wherein the preprocessing includes filtering and/or histogram enhancement processing; an enhancement subunit, used to perform vascular boundary enhancement on the target blood vessel in the preprocessed coronary angiography image to obtain a boundary-enhanced coronary angiography image; a binarization and denoising subunit, used to perform image binarization and morphological denoising processing on the boundary-enhanced coronary angiography image to obtain a processed coronary angiography image; an extraction subunit, used to extract the shortest path with the retracement starting point as the starting point and the retracement end point as the end point from the processed coronary angiography image as the retracement path.

Exemplarily, the vascular parameters include the cross-sectional area corresponding to each point of the long axis of the vascular model. The second determination module 540 includes: a second determination submodule, which is used to determine the stenotic vascular segment and the normal vascular segment in the vascular model based on the size of the cross-sectional area corresponding to each point of the long axis of the vascular model; a second acquisition submodule, which is used to acquire the mean arterial pressure of the target vessel; a third determination submodule, which is used to determine the pressure difference corresponding to the stenotic vascular segment based on the cross-sectional area corresponding to the stenotic vascular segment, the cross-sectional area corresponding to the normal vascular segment and the length of the stenotic vascular segment; and a fourth determination submodule, which is used to determine the blood flow reserve fraction of the target vessel based on the mean arterial pressure and the pressure difference.

According to another aspect of the present application, an electronic device is also provided. FIG6 shows a schematic block diagram of an electronic device according to an embodiment of the present application. As shown in the figure, the electronic device 600 includes a processor 610 and a memory 620, wherein the memory 620 stores computer program instructions, and the computer program instructions are used by the processor 610 to perform the following operations when running: determining the diastolic waveform-free interval in the cardiac cycle of the target object; obtaining a target ultrasound image and a target angiography image of the target blood vessel of the target object in the diastolic waveform-free interval; performing vascular reconstruction based on the target ultrasound image and the target angiography image to generate a vascular model of the target blood vessel; and determining the blood flow reserve fraction of the target blood vessel based on the vascular parameters in the vascular model.

Exemplarily, the target ultrasound image is acquired by an ultrasound device; the step of determining the diastolic waveform-free interval in the cardiac cycle of the target object executed by the computer program instructions when the processor 610 is running includes: receiving the electrocardiogram signal of the target object from the electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal. The computer program instructions are also used to execute when the processor 610 is running: when the start time of the diastolic waveform-free interval is identified, control the ultrasound device to start acquiring the intravascular ultrasound image; when the end time of the diastolic waveform-free interval is identified, control the ultrasound device to stop acquiring the intravascular ultrasound image. The step of acquiring the target ultrasound image of the target blood vessel of the target object in the diastolic waveform-free interval executed when the computer program instructions are running by the processor 610 includes: acquiring the intravascular ultrasound image acquired by the ultrasound device as the target ultrasound image.

The electrocardiogram device described herein may be included in the vascular imaging system or may be independent of the vascular imaging system. In one example, the vascular imaging system may further include an electrocardiogram device for collecting electrocardiogram signals of the target object, and the processing device is connected to the electrocardiogram device.

Exemplarily, the target ultrasound image is acquired by an ultrasound device; the step of determining the diastolic waveform-free interval in the cardiac cycle of the target object executed by the computer program instructions when the processor 610 is running includes: receiving the electrocardiogram signal of the target object from the electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal. The step of acquiring the target ultrasound image of the target blood vessel of the target object in the diastolic waveform-free interval executed by the computer program instructions when the processor 610 is running includes: selecting the target ultrasound image from the intravascular ultrasound images acquired by the ultrasound device based on the identified diastolic waveform-free interval; wherein the ultrasound device and the electrocardiogram device synchronously acquire the respective corresponding intravascular ultrasound images and electrocardiogram signals, and the ultrasound device continuously acquires the intravascular ultrasound images.

Exemplarily, the target angiography image is acquired by an angiography device; the computer program instructions are used by the processor 610 to execute the steps of determining the diastolic waveform-free interval within the cardiac cycle of the target object, including: receiving the electrocardiogram signal of the target object from the electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal. The computer program instructions are also used by the processor 610 to: control the angiography device to start acquiring coronary angiography images when the start moment of the diastolic waveform-free interval is identified; and control the angiography device to stop acquiring coronary angiography images when the end moment of the diastolic waveform-free interval is identified. The computer program instructions are used by the processor 610 to execute the steps of acquiring the diastolic waveform-free interval of the target blood vessel of the target object when the processor 610 is running. The step of obtaining a target ultrasound image within the coronary angiography interval includes: selecting at least two frames of angiography images with different angiography angles as target angiography images from the coronary angiography images acquired by the angiography device.

Exemplarily, the target angiography image is collected by an angiography device; the step of determining the diastolic waveform-free interval in the cardiac cycle of the target object executed by the computer program instructions when the processor 610 is running includes: receiving the electrocardiogram signal of the target object from the electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal; the step of obtaining the target angiography image of the target blood vessel of the target object in the diastolic waveform-free interval when the computer program instructions are run by the processor 610 includes: based on the identified diastolic waveform-free interval, selecting at least two frames of candidate coronary angiography images of different angiography angles from the coronary angiography images collected by the angiography device as the target angiography image. The candidate coronary angiography image is a coronary angiography image collected by the angiography device during the diastolic waveform-free interval. The angiography device and the electrocardiogram device synchronously collect their respective corresponding coronary angiography images and electrocardiogram signals, and the angiography device continuously collects coronary angiography images.

Exemplarily, the steps of identifying the diastolic waveform-free interval based on the ECG signal executed by the computer program instructions when the processor 610 is running include: calculating the instantaneous resistance at each moment in the cardiac cycle based on the waveform amplitude characteristics of the ECG signal; and determining the diastolic waveform-free interval based on the instantaneous resistance at each moment in the cardiac cycle.

Exemplarily, the computer program instructions are used by the processor 610 to perform blood vessel reconstruction based on the target ultrasound image and the target contrast image, and the steps of generating a blood vessel model of the target blood vessel include: identifying the centerline of the target blood vessel from the target contrast image; identifying the lumen contour of the target blood vessel from the target ultrasound image; and aligning and reconstructing the lumen contour along the centerline to obtain a blood vessel model.

Exemplarily, before the computer program instructions are executed by the processor 610 to register and reconstruct the lumen contour along the centerline to obtain the blood vessel model, the computer program instructions are also executed by the processor 610 to identify the side branches of the target blood vessel from the target ultrasound image. The computer program instructions are executed by the processor 610 to register and reconstruct the lumen contour along the centerline to obtain the blood vessel model, including: registering and reconstructing the side branches along the centerline with the lumen contour.

Exemplarily, the target ultrasound image is collected by an ultrasound device; the ultrasound device includes an ultrasound catheter and an ultrasound transducer disposed on the ultrasound catheter; the ultrasound transducer is used to collect an intravascular ultrasound image of the target object during the retraction of the ultrasound catheter; the steps of identifying the centerline of the target blood vessel from the target angiography image executed by the computer program instructions when the processor 610 is running include the following operations. For each frame of coronary angiography image in the target angiography image, determine the retraction starting point and the retraction end point of the ultrasound catheter in the coronary angiography image. Based on the retraction starting point and the retraction end point, extract the retraction path of the ultrasound catheter from the coronary angiography image. Based on the retraction path corresponding to each frame of coronary angiography image in the target angiography image, generate a three-dimensional retraction path of the ultrasound catheter. Among them, the centerline of the target blood vessel is represented by a three-dimensional retraction path.

Exemplarily, the computer program instructions used by the processor 610 to execute the steps of extracting the retraction path of the ultrasound catheter from the coronary angiography image based on the retraction starting point and the retraction end point include the following operations. The coronary angiography image is preprocessed to obtain a preprocessed coronary angiography image. The preprocessing includes filtering and/or histogram enhancement processing. The target blood vessel in the preprocessed coronary angiography image is enhanced by the vessel boundary to obtain a coronary angiography image with enhanced boundary. The coronary angiography image with enhanced boundary is binarized and morphologically denoised to obtain a processed coronary angiography image. The shortest path starting from the retraction starting point and ending at the retraction end point is extracted from the processed coronary angiography image as the retraction path.

Exemplarily, the vascular parameters include the cross-sectional area corresponding to each point on the long axis of the vascular model. The steps for determining the blood flow reserve fraction of the target vessel based on the vascular parameters in the vascular model executed by the processor 610 when the computer program instructions are executed include: determining the stenotic vessel segment and the normal vessel segment in the vascular model based on the size of the cross-sectional area corresponding to each point on the long axis of the vascular model; obtaining the mean arterial pressure of the target vessel; determining the pressure difference corresponding to the stenotic vessel segment based on the cross-sectional area corresponding to the stenotic vessel segment, the cross-sectional area corresponding to the normal vessel segment, and the length of the stenotic vessel segment; and determining the blood flow reserve fraction of the target vessel based on the mean arterial pressure and the pressure difference.

According to another aspect of the present application, a computer-readable storage medium is further provided, on which program instructions are stored, and the program instructions are used to perform the following operations when running: determining a diastolic waveform-free interval in a cardiac cycle of a target object; acquiring a target ultrasound image and a target contrast image of a target blood vessel of the target object in the diastolic waveform-free interval; performing blood vessel reconstruction based on the target ultrasound image and the target contrast image to generate a blood vessel model of the target blood vessel; Based on the vascular parameters in the vascular model, the blood flow reserve fraction of the target vessel is determined. The computer-readable storage medium may include, for example, a storage component of a tablet computer, a hard disk of a personal computer, an erasable programmable read-only memory (EPROM), a portable read-only memory (CD-ROM), a USB memory, or any combination of the above storage media. The computer-readable storage medium may be any combination of one or more non-volatile storage media.

Exemplarily, the target ultrasound image is acquired by an ultrasound device; the step of determining the diastolic waveform-free interval within the cardiac cycle of the target object executed by the program instructions at runtime includes: receiving the electrocardiogram signal of the target object from an electrocardiogram device. Identifying the diastolic waveform-free interval based on the electrocardiogram signal. The program instructions at runtime are also used to execute: when the start moment of the diastolic waveform-free interval is identified, controlling the ultrasound device to start acquiring the intravascular ultrasound image; when the end moment of the diastolic waveform-free interval is identified, controlling the ultrasound device to stop acquiring the intravascular ultrasound image. The step of acquiring the target ultrasound image of the target blood vessel of the target object within the diastolic waveform-free interval executed by the program instructions at runtime includes: acquiring the intravascular ultrasound image acquired by the ultrasound device as the target ultrasound image.

Exemplarily, the target ultrasound image is collected by an ultrasound device; the step of determining the diastolic waveform-free interval in the cardiac cycle of the target object executed by the program instructions when running includes: receiving the electrocardiogram signal of the target object from the electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal. The step of obtaining the target ultrasound image of the target blood vessel of the target object in the diastolic waveform-free interval executed by the program instructions when running includes: selecting the target ultrasound image from the intravascular ultrasound images collected by the ultrasound device based on the identified diastolic waveform-free interval; wherein the ultrasound device and the electrocardiogram device synchronously collect the corresponding intravascular ultrasound images and electrocardiogram signals, and the ultrasound device continuously collects the intravascular ultrasound images.

Exemplarily, the target angiography image is acquired by an angiography device; the step of determining the diastolic waveform-free interval in the cardiac cycle of the target object executed by the program instructions during operation includes: receiving the electrocardiogram signal of the target object from the electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal. The program instructions during operation are also used to: control the angiography device to start acquiring coronary angiography images when the start time of the diastolic waveform-free interval is identified; and control the angiography device to stop acquiring coronary angiography images when the end time of the diastolic waveform-free interval is identified. The step of acquiring the target ultrasound image of the target blood vessel of the target object during the diastolic waveform-free interval executed by the program instructions during operation includes: selecting at least two frames of angiography images at different angiography angles from the coronary angiography images acquired by the angiography device as the target angiography images.

Exemplarily, the target angiography image is collected by an angiography device; the step of determining the diastolic waveform-free interval in the cardiac cycle of the target object executed by the program instructions during operation includes: receiving the electrocardiogram signal of the target object from the electrocardiogram device; identifying the diastolic waveform-free interval based on the electrocardiogram signal; the step of obtaining the target angiography image of the target blood vessel of the target object during the diastolic waveform-free interval executed by the program instructions during operation includes: based on the identified diastolic waveform-free interval, selecting at least two frames of candidate coronary angiography images of different angiography angles from the coronary angiography images collected by the angiography device as the target angiography image. The candidate coronary angiography image is a coronary angiography image collected by the angiography device during the diastolic waveform-free interval. The angiography device and the electrocardiogram device synchronously collect their respective corresponding coronary angiography images and electrocardiogram signals, and the angiography device continuously collects coronary angiography images.

Exemplarily, the steps of identifying the diastolic waveform-free interval based on the electrocardiogram signal executed by the program instructions during operation include the following operations: Calculating the instantaneous resistance at each moment in the cardiac cycle based on the waveform amplitude characteristics of the electrocardiogram signal. Determining the diastolic waveform-free interval based on the instantaneous resistance at each moment in the cardiac cycle.

Exemplarily, the program instructions used to perform blood vessel reconstruction based on the target ultrasound image and the target contrast image during runtime to generate a blood vessel model of the target blood vessel include: identifying the centerline of the target blood vessel from the target contrast image; identifying the lumen contour of the target blood vessel from the target ultrasound image; and aligning and reconstructing the lumen contour along the centerline to obtain a blood vessel model.

Exemplarily, before the step of registering and reconstructing the lumen contour along the centerline to obtain the blood vessel model is executed by the program instructions when running, the program instructions are also used to execute: identifying the side branches of the target blood vessel from the target ultrasound image. The step of registering and reconstructing the lumen contour along the centerline to obtain the blood vessel model executed by the program instructions when running includes: registering and reconstructing the side branches together with the lumen contour along the centerline.

Exemplarily, the target ultrasound image is acquired by an ultrasound device; the ultrasound device includes an ultrasound catheter and an ultrasound transducer disposed on the ultrasound catheter; the ultrasound transducer is used to acquire an intravascular ultrasound image of the target object during the withdrawal of the ultrasound catheter; The steps of identifying the centerline of the target blood vessel from the target angiography image executed by the program instructions during operation include the following operations. For each frame of coronary angiography image in the target angiography image, determine the withdrawal starting point and withdrawal end point of the ultrasound catheter in the coronary angiography image. Based on the withdrawal starting point and withdrawal end point, extract the withdrawal path of the ultrasound catheter from the coronary angiography image. Based on the withdrawal path corresponding to each frame of coronary angiography image in the target angiography image, generate a three-dimensional withdrawal path of the ultrasound catheter. Among them, the centerline of the target blood vessel is represented by a three-dimensional withdrawal path.

Exemplarily, the steps of extracting the retraction path of the ultrasound catheter from the coronary angiography image based on the retraction starting point and the retraction end point executed by the program instructions at runtime include the following operations. Preprocessing the coronary angiography image to obtain a preprocessed coronary angiography image. The preprocessing includes filtering and/or histogram enhancement processing. Performing vessel boundary enhancement on the target blood vessel in the preprocessed coronary angiography image to obtain a boundary-enhanced coronary angiography image. Performing image binarization and morphological denoising processing on the boundary-enhanced coronary angiography image to obtain a processed coronary angiography image. Extracting the shortest path starting from the retraction starting point and ending at the retraction end point from the processed coronary angiography image as the retraction path.

Exemplarily, the vascular parameters include the cross-sectional area corresponding to each point on the long axis of the vascular model, and the program instructions used to execute the steps of determining the blood flow reserve fraction of the target blood vessel based on the vascular parameters in the vascular model during execution include: determining the stenotic vascular segment and the normal vascular segment in the vascular model based on the size of the cross-sectional area corresponding to each point on the long axis of the vascular model; obtaining the mean arterial pressure of the target blood vessel; determining the pressure difference corresponding to the stenotic vascular segment based on the cross-sectional area corresponding to the stenotic vascular segment, the cross-sectional area corresponding to the normal vascular segment, and the length of the stenotic vascular segment; and determining the blood flow reserve fraction of the target blood vessel based on the mean arterial pressure and the pressure difference.

A person skilled in the art may understand the specific implementation scheme of the above electronic device and non-volatile storage medium by reading the above description of the method for determining the blood flow reserve fraction, which will not be described in detail here for the sake of brevity.

Although example embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above example embodiments are merely exemplary and are not intended to limit the scope of the present application to this. Those of ordinary skill in the art may make various changes and modifications therein without departing from the scope and spirit of the present application. All these changes and modifications are intended to be included within the scope of the present application as required by the appended claims.

Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of the units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed.

In the description provided herein, a large number of specific details are described. However, it is understood that the embodiments of the present application can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

Similarly, it should be understood that in order to streamline the present application and help understand one or more of the various inventive aspects, in the description of the exemplary embodiments of the present application, the various features of the present application are sometimes grouped together into a single embodiment, figure, or description thereof. However, the method of the present application should not be interpreted as reflecting the following intention: the claimed application requires more features than the features clearly stated in each claim. More specifically, as reflected in the corresponding claims, the inventive point is that the corresponding technical problem can be solved with features less than all the features of a single disclosed embodiment. Therefore, the claims following the specific embodiment are hereby explicitly incorporated into the specific embodiment, wherein each claim itself serves as a separate embodiment of the present application.

Those skilled in the art will understand that, except for mutually exclusive features, all features disclosed in this specification (including the accompanying claims, abstract and drawings) and all processes or units of any method or device disclosed in this specification (including the accompanying claims, abstract and drawings) can be combined in any combination. Each feature disclosed in the abstract and drawings may be replaced by alternative features serving the same, equivalent or similar purpose.

In addition, those skilled in the art will appreciate that, although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the claims, any one of the claimed embodiments can be used in any combination.

The various component embodiments of the present application can be implemented in hardware, or in software modules running on one or more processors, or in a combination thereof. It should be understood by those skilled in the art that a microprocessor or a digital signal processor (DSP) can be used in practice to implement some or all of the functions of some modules in the vascular imaging device and electronic device according to the embodiments of the present application. The present application can also be implemented as a device program (e.g., a computer program and a computer program product) for executing part or all of the methods described herein. Such a program implementing the present application can be stored on a computer-readable medium, or can be in the form of one or more signals. Such a signal can be downloaded from an Internet website, or provided on a carrier signal, or provided in any other form.

It should be noted that the above embodiments illustrate the present application rather than limit the present application, and that those skilled in the art may design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbol between brackets should not be constructed as a limitation to the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "one" or "an" preceding an element does not exclude the presence of multiple such elements. The present application may be implemented by means of hardware including several different elements and by means of a suitably programmed computer. In a unit claim that lists several devices, several of these devices may be embodied by the same hardware item. The use of the words first, second, and third, etc. does not indicate any order. These words may be interpreted as names.

The above is only a specific implementation or description of a specific implementation of the present application, and the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. The protection scope of the present application shall be based on the protection scope of the claims.

Claims (25)

A vascular imaging system, comprising: Ultrasound equipment for acquiring intravascular ultrasound images of a target object; Angiography equipment, used for acquiring coronary angiography images of the target object; A processing device, connected to the ultrasound device and the imaging device respectively, for: determining a diastolic waveform-free interval within a cardiac cycle of the target subject; Respectively acquiring a target ultrasound image and a target angiography image of a target blood vessel of the target object in the diastolic waveform-free interval from the images respectively acquired by the ultrasound device and the angiography device; Performing blood vessel reconstruction based on the target ultrasound image and the target angiography image to generate a blood vessel model of the target blood vessel; Based on the blood vessel parameters in the blood vessel model, a blood flow reserve fraction of the target blood vessel is determined. The vascular imaging system according to claim 1, characterized in that the vascular imaging system further comprises an electrocardiogram device for collecting electrocardiogram signals of the target object, the processing device is connected to the electrocardiogram device, wherein: The processing device determines the diastolic waveform-free interval in the cardiac cycle of the target object by: receiving an electrocardiogram signal of the target subject from the electrocardiogram device; Identifying the diastolic waveform-free interval based on the electrocardiogram signal; The processing device is also used for: When the start time of the diastolic waveform-free interval is identified, controlling the ultrasound device to start acquiring intravascular ultrasound images; When the end time of the diastolic waveform-free interval is identified, controlling the ultrasound device to stop acquiring the intravascular ultrasound image; The processing device acquires a target ultrasound image of a target blood vessel of the target object in the diastolic waveform-free interval from the image acquired by the ultrasound device in the following manner: An intravascular ultrasound image acquired by the ultrasound device is acquired as the target ultrasound image. The vascular imaging system according to claim 1, characterized in that the vascular imaging system further comprises an electrocardiogram device for collecting electrocardiogram signals of the target object, the processing device is connected to the electrocardiogram device, wherein: The processing device determines the diastolic waveform-free interval in the cardiac cycle of the target object by: receiving an electrocardiogram signal of the target subject from the electrocardiogram device; Identifying the diastolic waveform-free interval based on the electrocardiogram signal; The processing device acquires a target ultrasound image of a target blood vessel of the target object in the diastolic waveform-free interval from the image acquired by the ultrasound device in the following manner: Selecting the target ultrasound image from the intravascular ultrasound images acquired by the ultrasound device based on the identified diastolic waveform-free interval; The ultrasound device and the electrocardiogram device synchronously acquire their respective corresponding intravascular ultrasound images and electrocardiogram signals, and the ultrasound device continuously acquires intravascular ultrasound images. The vascular imaging system according to claim 1, characterized in that the vascular imaging system further comprises an electrocardiogram device for collecting electrocardiogram signals of the target object, and the processing device is connected to the electrocardiogram device. The processing device determines the diastolic waveform-free interval in the cardiac cycle of the target object by: receiving an electrocardiogram signal of the target subject from the electrocardiogram device; Identifying the diastolic waveform-free interval based on the electrocardiogram signal; The processing device is also used for: When the start time of the diastolic waveform-free interval is identified, the angiography device is controlled to start collecting coronary artery Contrast images; When the end time of the diastolic waveform-free interval is identified, controlling the angiography device to stop acquiring the coronary angiography image; The processing device acquires a target angiography image of a target blood vessel of the target object in the diastolic waveform-free interval from the image acquired by the angiography device in the following manner: At least two frames of coronary angiography images at different angiography angles are selected from the coronary angiography images acquired by the angiography device as the target angiography images. The vascular imaging system according to claim 1, characterized in that the vascular imaging system further comprises an electrocardiogram device for collecting electrocardiogram signals of the target object, and the processing device is connected to the electrocardiogram device. The processing device determines the diastolic waveform-free interval in the cardiac cycle of the target object by: receiving an electrocardiogram signal of the target subject from the electrocardiogram device; Identifying the diastolic waveform-free interval based on the electrocardiogram signal; The processing device acquires a target angiography image of a target blood vessel of the target object in the diastolic waveform-free interval from the image acquired by the angiography device in the following manner: Based on the identified diastolic waveform-free interval, selecting at least two frames of candidate coronary angiography images at different angiography angles from the coronary angiography images acquired by the angiography device as the target angiography images; Wherein, the candidate coronary angiography image is a coronary angiography image acquired by the angiography device during the diastolic waveform-free interval; The angiography device and the electrocardiogram device synchronously acquire corresponding coronary angiography images and electrocardiogram signals, and the angiography device continuously acquires coronary angiography images. The vascular imaging system according to any one of claims 2 to 5, characterized in that: The processing device identifies the diastolic waveform-free interval based on the electrocardiogram signal in the following manner: Calculating the instantaneous resistance at each moment in the cardiac cycle based on the waveform amplitude characteristics of the electrocardiogram signal; The diastolic waveform-free interval is determined based on the instantaneous resistance at each moment in the cardiac cycle. The vascular imaging system according to any one of claims 1 to 5, characterized in that the processing device performs vascular reconstruction based on the target ultrasound image and the target angiography image to generate a vascular model of the target blood vessel in the following manner: identifying a centerline of the target blood vessel from the target angiography image; identifying a lumen contour of the target blood vessel from the target ultrasound image; The lumen contour is registered and reconstructed along the center line to obtain the blood vessel model. The vascular imaging system according to claim 7, characterized in that: The processing device is also used to: identify side branches of the target blood vessel from the target ultrasound image; The processing device registers and reconstructs the lumen contour along the center line to obtain the blood vessel model in the following manner: The side branches are registered and reconstructed together with the lumen contour along the center line. The vascular imaging system according to claim 7, characterized in that the ultrasound device comprises an ultrasound catheter and an ultrasound transducer disposed on the ultrasound catheter; the ultrasound transducer is used to acquire an intravascular ultrasound image of the target object during the withdrawal of the ultrasound catheter; and the processing device identifies the centerline of the target blood vessel from the target angiography image by: For each frame of coronary angiography image in the target angiography image, Determining a withdrawal starting point and a withdrawal end point of the ultrasound catheter in the coronary angiography image; Extracting a withdrawal path of the ultrasound catheter from the coronary angiography image based on the withdrawal starting point and the withdrawal end point; generating a three-dimensional retraction path of the ultrasound catheter based on the retraction path corresponding to each frame of the coronary angiography image in the target angiography image; Wherein, the centerline of the target blood vessel is represented by the three-dimensional retracement path. The vascular imaging system according to claim 9, characterized in that the processing device extracts the retraction path of the ultrasound catheter from the coronary angiography image based on the retraction starting point and the retraction end point in the following manner: Preprocessing the coronary angiography image to obtain a preprocessed coronary angiography image, wherein the preprocessing includes filtering and/or histogram enhancement processing; Performing blood vessel boundary enhancement on the target blood vessel in the preprocessed coronary angiography image to obtain a boundary-enhanced coronary angiography image; Performing image binarization and morphological denoising processing on the boundary-enhanced coronary angiography image to obtain a processed coronary angiography image; The shortest path starting from the retrieval starting point and ending at the retrieval end point is extracted from the processed coronary angiography image as the retrieval path. The vascular imaging system according to any one of claims 1 to 5, characterized in that the vascular parameters include the cross-sectional areas corresponding to each point of the long axis of the vascular model, and the processing device determines the blood flow reserve fraction of the target blood vessel based on the vascular parameters in the vascular model in the following manner: Determining a stenotic blood vessel segment and a normal blood vessel segment in the blood vessel model based on the size of the cross-sectional area corresponding to each point on the long axis of the blood vessel model; obtaining a mean arterial pressure of the target blood vessel; determining a pressure difference corresponding to the stenotic blood vessel segment based on a cross-sectional area corresponding to the stenotic blood vessel segment, a cross-sectional area corresponding to the normal blood vessel segment, and a length of the stenotic blood vessel segment; Based on the mean arterial pressure and the pressure difference, a fractional flow reserve of the target blood vessel is determined. A vascular imaging method, comprising: determining a diastolic waveform-free interval within a cardiac cycle of the target subject; Acquire a target ultrasound image and a target contrast image of a target blood vessel of the target object in the diastolic waveform-free interval from images acquired by an ultrasound device and a contrast imaging device respectively; Performing blood vessel reconstruction based on the target ultrasound image and the target angiography image to generate a blood vessel model of the target blood vessel; Based on the blood vessel parameters in the blood vessel model, a blood flow reserve fraction of the target blood vessel is determined. The vascular imaging method according to claim 12, characterized in that: The step of determining the diastolic waveform-free interval in the cardiac cycle of the target object comprises: receiving an electrocardiogram signal of the target object from an electrocardiogram device; Identifying the diastolic waveform-free interval based on the electrocardiogram signal; The method further comprises: When the start time of the diastolic waveform-free interval is identified, controlling the ultrasound device to start acquiring intravascular ultrasound images; When the end time of the diastolic waveform-free interval is identified, controlling the ultrasound device to stop acquiring the intravascular ultrasound image; The step of acquiring a target ultrasound image of a target blood vessel of the target object in the diastolic waveform-free interval from an image acquired by an ultrasound device includes: An intravascular ultrasound image acquired by the ultrasound device is acquired as the target ultrasound image. The vascular imaging method according to claim 12, characterized in that: The step of determining the diastolic waveform-free interval in the cardiac cycle of the target object comprises: receiving an electrocardiogram signal of the target object from an electrocardiogram device; Identifying the diastolic waveform-free interval based on the electrocardiogram signal; The step of acquiring a target ultrasound image of a target blood vessel of the target object in the diastolic waveform-free interval from an image acquired by an ultrasound device includes: Selecting the target ultrasound image from the intravascular ultrasound images acquired by the ultrasound device based on the identified diastolic waveform-free interval; The ultrasound device and the electrocardiogram device synchronously acquire their respective corresponding intravascular ultrasound images and electrocardiogram signals, and the ultrasound device continuously acquires intravascular ultrasound images. The vascular imaging method according to claim 12, characterized in that: The step of determining the diastolic waveform-free interval in the cardiac cycle of the target object comprises: receiving an electrocardiogram signal of the target object from an electrocardiogram device; Identifying the diastolic waveform-free interval based on the electrocardiogram signal; The method further comprises: When the start time of the diastolic waveform-free interval is identified, controlling the angiography device to start collecting coronary angiography images; When the end time of the diastolic waveform-free interval is identified, controlling the angiography device to stop acquiring the coronary angiography image; The step of acquiring a target angiography image of a target blood vessel of the target object in the diastolic waveform-free interval from an image acquired by an angiography device comprises: At least two frames of coronary angiography images at different angiography angles are selected from the coronary angiography images acquired by the angiography device as the target angiography images. The vascular imaging method according to claim 12, characterized in that: The step of determining the diastolic waveform-free interval in the cardiac cycle of the target object comprises: receiving an electrocardiogram signal of the target object from an electrocardiogram device; Identifying the diastolic waveform-free interval based on the electrocardiogram signal; The step of acquiring a target angiography image of a target blood vessel of the target object in the diastolic waveform-free interval from an image acquired by an angiography device comprises: Based on the identified diastolic waveform-free interval, selecting at least two frames of candidate coronary angiography images at different angiography angles from the coronary angiography images acquired by the angiography device as the target angiography images; Wherein, the candidate coronary angiography image is a coronary angiography image acquired by the angiography device during the diastolic waveform-free interval; The angiography device and the electrocardiogram device synchronously acquire corresponding coronary angiography images and electrocardiogram signals, and the angiography device continuously acquires coronary angiography images. The vascular imaging method according to any one of claims 13 to 16, characterized in that the step of identifying the diastolic waveform-free interval based on the electrocardiogram signal comprises: Calculating the instantaneous resistance at each moment in the cardiac cycle based on the waveform amplitude characteristics of the electrocardiogram signal; The diastolic waveform-free interval is determined based on the instantaneous resistance at each moment in the cardiac cycle. The vascular imaging method according to any one of claims 12 to 16, characterized in that the target ultrasonography The method of reconstructing a blood vessel using the acoustic image and the target angiography image to generate a blood vessel model of the target blood vessel includes: identifying a centerline of the target blood vessel from the target angiography image; identifying a lumen contour of the target blood vessel from the target ultrasound image; The lumen contour is registered and reconstructed along the center line to obtain the blood vessel model. The vascular imaging method according to claim 18, characterized in that: Before registering and reconstructing the lumen contour along the center line to obtain the blood vessel model, reconstructing the blood vessel based on the target ultrasound image and the target angiography image to generate the blood vessel model of the target blood vessel further includes: identifying a side branch of the target blood vessel from the target ultrasound image; The step of registering and reconstructing the lumen contour along the center line to obtain the blood vessel model comprises: The side branches are registered and reconstructed together with the lumen contour along the center line. The vascular imaging method according to claim 18, characterized in that the ultrasound device comprises an ultrasound catheter and an ultrasound transducer disposed on the ultrasound catheter; the ultrasound transducer is used to acquire an intravascular ultrasound image of the target object during the withdrawal of the ultrasound catheter; and the identifying the centerline of the target blood vessel from the target angiography image comprises: For each frame of coronary angiography image in the target angiography image, Determining a withdrawal starting point and a withdrawal end point of the ultrasound catheter in the coronary angiography image; Extracting a withdrawal path of the ultrasound catheter from the coronary angiography image based on the withdrawal starting point and the withdrawal end point; generating a three-dimensional retraction path of the ultrasound catheter based on the retraction path corresponding to each frame of the coronary angiography image in the target angiography image; Wherein, the centerline of the target blood vessel is represented by the three-dimensional retracement path. The vascular imaging method according to claim 20, characterized in that extracting the withdrawal path of the ultrasound catheter from the coronary angiography image based on the withdrawal starting point and the withdrawal end point comprises: Preprocessing the coronary angiography image to obtain a preprocessed coronary angiography image, wherein the preprocessing includes filtering and/or histogram enhancement processing; Performing blood vessel boundary enhancement on the target blood vessel in the preprocessed coronary angiography image to obtain a boundary-enhanced coronary angiography image; Performing image binarization and morphological denoising processing on the boundary-enhanced coronary angiography image to obtain a processed coronary angiography image; The shortest path starting from the retrieval starting point and ending at the retrieval end point is extracted from the processed coronary angiography image as the retrieval path. The vascular imaging method according to any one of claims 12 to 16, characterized in that the vascular parameters include the cross-sectional areas corresponding to each point of the vascular model at the long axis; and determining the blood flow reserve fraction of the target vessel based on the vascular parameters in the vascular model comprises: Determining a stenotic blood vessel segment and a normal blood vessel segment in the blood vessel model based on the size of the cross-sectional area corresponding to each point on the long axis of the blood vessel model; obtaining a mean arterial pressure of the target blood vessel; determining a pressure difference corresponding to the stenotic blood vessel segment based on a cross-sectional area corresponding to the stenotic blood vessel segment, a cross-sectional area corresponding to the normal blood vessel segment, and a length of the stenotic blood vessel segment; Based on the mean arterial pressure and the pressure difference, a fractional flow reserve of the target blood vessel is determined. A vascular imaging device, comprising: A first determination module is used to determine a diastolic waveform-free interval in a cardiac cycle of a target object; An acquisition module, configured to respectively acquire a target ultrasound image and a target angiography image of a target blood vessel of the target object in the diastolic waveform-free interval from images acquired by an ultrasound device and an angiography device respectively; A blood vessel reconstruction module, used for performing blood vessel reconstruction based on the target ultrasound image and the target angiography image to generate a blood vessel model of the target blood vessel; The second determination module is used to determine the blood flow reserve fraction of the target blood vessel based on the blood vessel parameters in the blood vessel model. An electronic device includes a processor and a memory, wherein the memory stores computer program instructions, and when the processor is executed, the computer program instructions are used to perform the following operations: determining a diastolic waveform-free interval within a cardiac cycle of the target subject; Acquire a target ultrasound image and a target angiography image of a target blood vessel of the target object in the diastolic waveform-free interval; Performing blood vessel reconstruction based on the target ultrasound image and the target angiography image to generate a blood vessel model of the target blood vessel; Based on the blood vessel parameters in the blood vessel model, a blood flow reserve fraction of the target blood vessel is determined. A computer-readable storage medium stores program instructions, which are used to perform the following operations when executed: determining a diastolic waveform-free interval within a cardiac cycle of the target subject; Acquire a target ultrasound image and a target angiography image of a target blood vessel of the target object in the diastolic waveform-free interval; Performing blood vessel reconstruction based on the target ultrasound image and the target angiography image to generate a blood vessel model of the target blood vessel; Based on the blood vessel parameters in the blood vessel model, a blood flow reserve fraction of the target blood vessel is determined.