DE19915583A1 - Device and method for 3D real-time sonography - Google Patents

Abstract

The invention relates to a device and a method for real-time 3D sonography. The inventive device comprises an ultrasound head, a signal processor and a display. The ultrasound head consists of at least one transmitter and at least three receivers independent therefrom. The positions of the receivers to the transmitters is known. The inventive device is characterised in that a signal processor consists of a signal generator for producing a transmission signal with any modulation function. The signal processor also consists of a correlator on each receiver which is connected to the signal generator respectively, a calculating unit for determining the paths of the transmission signal via the reflecting structure and to the receivers on each correlator and a calculating unit for determining the space co-ordinates of the reflecting structure, whereby each calculating unit is connected to the space co-ordinates for determining the paths of the transmission signal via the reflecting structure and to the receivers.

Description

The invention relates to an apparatus and a method for 3D real-time ultrasound with an ultrasound head, one Signal processing and a display device in which the Speed of data acquisition over unknown structures only through the physics of the formwork conductor in the respective body is limited.

In ultrasound diagnostics is the simplest Application emitting an ultrasound pulse into a tissue and the returning echo pulses are related to the Runtime evaluated to the depth and the extent or the Course of a certain structure on which the reflections arise to determine. With the conventional devices of Ultrasound diagnostics use ultrasound heads that in the best known versions from a linear arrangement individual mechanically separated piezo elements exist. The Piezo elements send a pulse train into the tissue and then received continuously in a fixed period of time Lich the returning echo signals. The same piezo elements then act as pressure sensors to receive the echo pulses. The time period is determined by the last one on the sensor incoming echo signal from the deepest reflection zone certainly. In such an ultrasound system generally the same piezo elements as both transmitters also as a recipient. In the resulting pictures, by a large amount of noise are then possibly recognizable certain structures, which in most Precise cases only due to a great experience of the doctor can be assessed.

The resolution (lateral and axial) has so far been an essential one Criterion for the quality and quality of an ultrasound device. A resolution of 0.5 mm (= 500 µm) is common.  

The development of "scanning pulse technology" due to the physical limits of the techno used logies found their end. It is only with great effort through modern computer technology (hardware) and modern Processes from signal processing (software) in general possible to achieve slight improvements in image quality. A further improvement of the picture quality could by special contrast agent administered to the patient are achieved, but these funds are often included considerable burdens on the patient and their Use is therefore controversial.

This is also the case with conventional 3D ultrasound devices "classic" scanning technology used, similar to CT Devices, when absorbing "layers" from the body. Due to the enormous amount of data associated with this, these are Technologies narrow limits in terms of "real time" - Data acquisition set. As a rule, when recording, the affected volumes between 0.3 s and 2 min all disturbing patient movements (internally and externally) either not allowed to take place or as statistical Disturbance must be included. This will make the Accuracy severely affected.

U.S. Patent 5,601,083 describes an apparatus which the ellipsoidal backprojection used to resolve improve. The device has a receiver array in which each receiving element has a reconstruction pixel angle corresponds. The echoes picked up by the receiver become in an amplitude function generator as a function of Reconstruction pixel angle weighted. In a post following back projection image reconstruction processing reconstructs an image from the weighted echoes and shown.  

In the recent development of sonography, the three-dimensional representation a decisive further experienced development. The three-dimensional images are at the known process from single images calculated. The main problem so far has been the very high one Time required to calculate these images. Through the Fast computers can also be provided today larger picture sequences with more than 30 pictures without problems calculate within approx. 10-15 s. But it is still not a real-time representation, i.e. H. the Disadvantages already described remain.

The basis of every three-dimensional ultrasound technology is the detection of several precisely determined in their position two-dimensional image planes, the entirety of which is volume results. A special transducer contains e.g. B. an engine, the inner array sound element at the push of a button depending on the type of the head swings by 10 ° to 95 °. This gives you one Large number of cutting planes that are equidistant from one another stand differently. The recorded echoes are after the Signal processing and quantization as digital signals stored in a volume memory true to location. The recording time is depending on volume size, type of head and Swing speed of the sound element between 0.3 s and 2 min. All of them can then be saved from the volume memory Section planes calculated within the respective volume and being represented. The three-dimensional images can be then either as single images or in the form of a rotation Display animation one after the other on the monitor.

In another process, the volume data is external detected. The movement of the sound element is one Position transmitter coupled. The transducer can then also from Be moved by hand. Together with the image data, the  Image position can be captured and saved. Then it can a standard transducer can be used, but the system is very unwieldy and requires a lot of time for the Acquisition of the image data. Because the distance between each two dimensional images is not identical, it may be too intersections of the cutting planes come that are too bad Presentations.

The other disadvantages of both methods are that the transducers in general only on the specially for this provided device can be operated, otherwise the Location is lost. On the other hand, there is none Real-time display, because the cutting planes one after the other be recorded. For a cardiological examination, the Representation of a heart reaction only after 6 to 7 Seconds worthless under certain conditions. In many In cases it is very important for the doctor to make a change to grasp immediately. The efforts in the Diagnostics are therefore definitely in the direction of real-time position.

The object of the present invention is a To create a device that has high image quality and Fast data acquisition and a 3D visualization enabled in real time.

The task is accomplished with the help of a device for the 3D Real-time sonography according to claim 1 and a method solved according to claim 7. The device consists of a Ultrasound head, signal processing and display device in which the ultrasound head consists of at least one Transmitter and separately there are at least three receivers, whose positions to the transmitters are known, the signal processing from a signal generator to generate a Transmitted signal with any modulation function, one  Correlator on each receiver, each with the signal generator is connected, a calculation unit for the Determination of the paths of the transmission signal via the reflective Structure to the receivers at each correlator, and one Calculation unit for determining the spatial coordinates of the reflective structure to which each calculation unit for the determination of the paths of the transmission signal via the reflec ting structure is connected to the receivers, consists.

It is completely up to the user where he or she the sender and receiver on the medium with the under arranges structure. This makes it possible to cheapest "viewing and lighting angle" one in Structure to be determined within a medium. Become at least three receivers arranged in one level and this determined as the "viewing window", d. H. as the reference plane for all transmitters, can be a shadow-free illustration of one in one Medium embedded structure can be created. It is that Users also exempted how many transmitters and how much Receiver can be arranged. For a three-dimensional However, at least one transmitter and three are shown Receiver or three transmitters and one receiver required.

The transmitter and receiver can e.g. B. also arranged so that the broadcast signal from the side to the structure hits or the medium lies between the transmitters and the Recipients. The echo signals are then essentially from the absorption quality of the medium and those to be examined Structure influenced. If there are several transmitters, you can Echo signals are received, both the quality of absorption as well as reflect the quality of reflection of a structure.

In a further embodiment of the device for the 3D Real time sonography is between the transmitter or transmitters and the  Correlator and each receiver and the correlator an A / D Transducer arranged. As a result, the transmission signals and the Receiver signals digitized and then digitally further processed.

The device for 3D real-time ultrasonography can A / D converter of the transmission signal contain a memory that stores the digitized broadcast signals to everyone further sound process in the same form To have available. To do this, the memory is direct or via a control unit connected to the generator. The tax unit can be designed to be manual or can be triggered automatically.

The invention also includes a method for 3D real-time sonography, in which ultrasound signals are emitted from an ultrasound head into a medium and the echo signals are received and displayed on an image unit, the method comprising the following steps:

• a) sending a transmission signal with any one Modulation function of at least one transmitter in one Medium;
• b) receiving the echo signals from at least three receivers, which are arranged separately from the transmitters and their Positions on the transmitters are known;
• c) correlation of the echo signals with the transmission signal Determination of the paths of the transmission signal from the transmitter via a reflective structure in the medium down to the respective Receivers by the pattern features of the transmission signal in the Echo signals are determined;
• d) determining the spatial coordinates and the reflection and / or absorption quality of the reflective structure from the Results of step c) using triangulation; and
• e) display of the spatial coordinates and the reflection and / or  Absorption quality of the reflective structure on one Display device.

If more than one transmitter is used in the process, the send a sedend signal with the same modulation function should, so that the "lighting directions "can be distinguished, the individual stations send the transmission signals one after the other. Become broadcast signals with different modulation functions, the transmitters can also send their broadcast signal into the Deliver medium.

Owing to the separation of the receiver from the transmitter the transmission signal has no length limitation. Its duration is only limited by the modulation function.

Contains the device after the transmitter and the receivers A / D converter, the transmit signal and the echo signals before digitized the correlation.

For the correlation between the transmission signal and echo signals, at the reflection points of the transmission signal can be determined all known methods can be used. It can be a simple correlation / convolution or an impulse compression procedures can be performed, it can be a Wavelet methods can be used, or it can be neural Networks are used, with the help of the characteristics of Search signal can be searched in the echo signals.

Intensity images, i.e. 3D B- Images are displayed, the choice of coordinates is free. In The calculation unit can, depending on the specification, reflect points in Cartesian coordinates, cylindrical coordinates ten, polar coordinates or the like can be determined.  

The procedure for 3D real-time sonography is also used extended when the transmission signals are stored in a memory be and to control the transmission generator for a renewed generation of the same transmission signals can be used. This process step is particularly favorable if a body is initially free with a broadcast signal with a adjustable modulation function is sonicated until visible reflections on the display device become visible. In the case of repetitions, the transmission signal can be used as often as desired retrieved the same modulation function from memory become.

Each echo signal is a superimposition of the reflection signals from the volume. The echo signals are in each channel processed separately and with the respective transmission signal correlated. To determine the position of the reflection points the path from the transmitter via the reflection points must first be closed the individual recipients. To do this, the Echo signals correlated with the transmission signal. The result the resulting signal shows a certain one at the times Signal pattern when a reflected signal arrives. Out The ellipses or ellipsoids become these times determined by the path of the transmission signal to the Reflection points are further determined to the receivers with the transmitter and the receiver in the focal points of the respective ellipses or ellipsoids. From the Intersections of the individual recipients Ellipsoids result in the spatial coordinates of the reflection Points.

The decisive difference to the conventional processes is due to the fact that the individual levels of Reflections are not recorded one after the other, but all data are recorded simultaneously. That fact is  an essential requirement for real-time sonography, that has not yet been realized. This is the first time possible to track moving structures in real time, e.g. B. the movement of the heart valves as a 3D image in slow motion. This makes cardiologists and gynecologists very happy important instruments in hand.

According to the physical conditions, the Penetration depth with increasing frequency. This reason Additional contradiction is the investigation of living Matter basically. The contradiction can be reduced when the sound energy is increased, but what is only possible to a limited extent in living matter. Through the The solution is given a very inventive solution high resolution with a large penetration depth achieve. Ultrasound diagnostics can be very useful low energies and thus with the lowest possible Load on the patient. With the conventional process, the maximum resolution is 1.5 mm a penetration depth of about 20 cm. With the inventive The procedure is e.g. B. at a penetration depth of 30 cm Resolution constant 0.1 mm. The resolution can go down to 0.05 mm increase.

An arbitrarily modulated ultrasound signal (e.g. also a growing or falling frequency sequence - based on the method of bats and dolphins used Echolocation). With a single such signal can get the information for the entire image volume be, the time required for this depending on the depth of the Structure in the medium can be in the microsecond range. The Echo signals become "parallel" and therefore very much recorded more time-efficiently than with the conventional methods.  

Another key advantage is that the Representation of the recorded structures much less Contains noise components. This makes the display significant more clearly, d. H. the experience of a doctor is no longer decisive for the assessment of a sonogram. There in primarily signal processing and no image processing processing - as with conventional processes - takes place, the entire information content is retained. A Falsification of the representation is therefore excluded.

Another advantage especially for the investigation of living tissue is very possible to use lower energies with which the body must be sonicated. This is the decisive disadvantage of all previous ones Eliminated procedures that only improve resolution by increasing energy.

The invention is intended to be explained in more detail with the aid of some illustrations are explained. Designate in the individual drawings same reference numerals same or similar parts.

Fig. 1 is a block diagram showing an apparatus for real-time 3D ultrasound according to the present invention with analog broadcast signals and corresponding analog processing of the echo signals;

Fig. 2 is a block diagram showing an apparatus for real-time 3D ultrasound according to the present invention with digital processing of the echo signals;

Figs. 3A and 3B show a specific than "chirp" designated transmit signal and the a corresponding echo signal;

FIG. 4 shows an echo signal of the “chirp” according to FIG. 3, which was reflected by 3 points;

FIG. 5 shows the result of the correlation of the "chirp" according to FIG. 3 with the echo signal according to FIG. 4;

Fig. 6 shows an echo signal with an SNR of 0 dB;

FIG. 7 shows the result of the correlation of the echo signal corresponding to FIG. 6 with the transmit signal according to FIG. 3; and

Fig. 8, the method of triangulation illustrates a reflection point with three receivers to determine the space coordinates.

In Fig. 1, an apparatus for real-time 3D ultrasound according to the invention in the form of a block diagram is shown in which an analog transmission signal is generated and the echo signals accordingly, are processed analogously. The generator 1 generates a carrier which is modulated in a modulator 2 with any function. In this exemplary embodiment, this transmission signal is emitted by a transmitter 3 into any medium or body. The echo pulses reflected from the structures in the medium are received in this embodiment, for example, by the three receivers 4 . To determine reflections, each echo signal in correlator 5 must therefore first be correlated with the transmitted signal. Each point of reflection in the medium is "seen" by the individual receivers 4 at a different time. For this purpose, the modulator 2 is connected to the correlator 5 of each individual receiver 4 . The same features in the transmission signal and the respective echo signal mean a reflection. The detection of these features can, for. B. done by shifting the transmission signal on the echo signals until there is a match that is an indication of a reflection. The result of this correlation shows a set of reflections, each representing the total path of the transmission signal from the transmitter 3 to the reflection point and back to the respective receiver 4 . That is, the transmitter 3 and the respective receiver 4 lie in the two focal points of an ellipsoid. The spatial coordinates of these reflection points are determined in the following calculation unit 6 by a simple triangulation method. The starting point is that the points of the same distance from the transmitter 3 to the reflection point and to the receiver 4 lie on an ellipsoid. The intersection of the three ellipsoids indicates the spatial coordinates at which the actual reflection took place. Fig. 8 illustrates this fact. The spatial coordinates are then displayed on a display device 7 with the corresponding intensity.

In Fig. 2 is a block diagram of an apparatus for real-time 3D ultrasound prepared according to the invention, but a digital processing is performed here of the information. The generator 1 generates a carrier which is modulated in a modulator 2 with any function. In this exemplary embodiment, the transmission signal is also emitted by a transmitter 3 into any medium. In contrast to the first exemplary embodiment, an A / D converter 8 is arranged between the modulator 2 and each correlator 5 and each receiver 4 and the associated correlators 5 . In this exemplary embodiment, a memory 9 is also arranged between the A / D converter 8 for the modulated signal and the generator 1 and stores the transmitted transmission signal for later repetition. For this purpose, the memory 9 is coupled to the generator 1 .

In Fig. 3, a transmission signal is presented with an increasing frequency. It is a chirp with a frequency of f _min to f _max . The wavelength of this signal decreases from left to right in the drawing. The entire information content of the area of interest is recorded at the same time with only one transmission signal and processed in parallel in a fast computer.

The echo signals of the transmission signal described in FIG. 3 are received by each receiver 4 . Such an echo signal, which was detected by one of the receivers 4 and which was reflected at three points, is shown in FIG . No noise components are superimposed on the echo signal in this representation. Only the first reflection point can be seen in this illustration. Additional reflection points are no longer recognizable in this diagram due to the superimposition of the echoes. Only after the correlation of the echo signal with the transmission signal, further reflection points become visible.

FIG. 5 shows the result of the correlation of the “chirp” according to FIG. 3 with the echo signal according to FIG. 4. A pattern feature arises precisely at the reflection points, the amplitude of which is proportional to the quality of reflection or absorption.

Fig. 6 shows the course of a very noisy echo signal in which the SNR is 0 dB. No reflections can be seen in this echo signal. After the correlation with the transmission signal, the signal curve according to FIG. 7 results . This signal is comparable to the signal according to FIG. 5, ie the reflection points are clearly recognizable. This makes a decisive advantage of the method according to the invention clear. Even at an SNR of -20 dB, the reflection points were still clearly detectable, but a certain level of noise was retained in the echo signals. Evaluation was only possible if the SNR was very bad.

When the device and the method according to the invention are used in medical diagnostics, the properties of the medium are of eminent importance. Because of its complicated composition, it is very difficult to derive a simple model that describes the frequency dependence of the attenuation of the ultrasound. In general, a linear relationship between the attenuation, the distance traveled by the signal and the frequency is assumed. If G represents the attenuation (in dB), f the frequency (in MHz), z the depth (in cm) in the medium and β the attenuation constant (in dB / [MHz cm]) of the medium, you get:

G = 2 β f z.

Higher frequencies are attenuated more than low frequencies. Table 1 shows the attenuation constant for different types of tissue:

Table 1

In Table 2 the attenuation (in dE) is dependent on the depth in the tissue and the frequency for tissue with the Attenuation constant of 0.7 dB / [MHz cm]).  

Table 2

Since it is possible, as was shown in FIGS. 4 to 7, to determine the positions of reflection points even in the case of a very poor SNR, one can therefore also at relatively low frequencies and low exposure energies despite the weakening in the tissue in accordance with Tables 1 and 2 achieve very good results.

Fig. 8, the method of triangulation illustrates a reflection point with three receivers to determine the space coordinates. It is illustrated how it is possible to determine the spatial coordinates of reflection points by sending an arbitrarily modulated signal. After the distances of the reflection points from the respective transmitter 3 to the reflection points to the respective receiver 4 have been determined in the correlator, one can define ellipsoids in the focal points of which the transmitter 3 or the receiver 4 are arranged. Each intersection of all three ellipsoids characterizes the spatial coordinates of a reflection point. If there are more than three receivers for a transmitter, there are also more than three ellipsoids for each reflection point, all of which intersect at a point which determines the spatial coordinates of the respective reflection point.

List of the reference symbols used

1

Signal generator

2nd

modulator

3rd

Channel

4th

receiver

5

Correlator

6

Calculation unit for determining the spatial coordinates of the reflective structure

7

Display device

8th

A / D converter

9

Storage

Claims (11)

1. Device for 3D real-time ultrasonography with an ultrasound head, a signal processing device and a display device, characterized in that the ultrasound head consists of at least one transmitter ( 3 ) and, separately, at least three receivers ( 4 ), the positions of which relative to the transmitters ( 3 ) It is known that the signal processing from a signal generator ( 1 ) for generating a transmission signal with any modulation function, a correlator ( 5 ) on each receiver ( 4 ), each of which is connected to the signal generator ( 1 ), a calculation unit for determining the Paths of the transmission signal via the reflecting structure to the receivers ( 4 ) at each correlator ( 5 ), and a calculation unit for determining the spatial coordinates of the reflecting structure ( 6 , to which each calculation unit for determining the paths of the transmission signal via the reflecting structure connected to the receivers. 2. Device for 3D real-time sonography according to claim 1, characterized in that the transmitter ( 3 ) and receiver ( 4 ) are arranged arbitrarily on a medium with a structure to be examined. 3. Device for 3D real-time sonography according to claim 1, characterized in that the receivers ( 4 ) are arranged in one plane. 4. Device for 3D real-time sonography according to one of claims 1 to 3, characterized in that an A / D between the individual transmitters ( 3 ) and each correlator ( 5 ) and each receiver ( 4 ) and the corresponding correlators ( 5 ) Converter ( 8 ) is arranged. 5. The device for 3D real-time sonography according to claim 4, characterized in that the A / D converter ( 8 ) for the transmission signal is followed by a memory ( 9 ) which is coupled to the signal generator ( 1 ). 6. The device for 3D real-time sonography according to claim 5, characterized in that the memory ( 9 ) is connected to the signal generator ( 1 ) via a control unit, and the control unit can be triggered manually or automatically. 7. Procedure for 3D real-time sonography, in which ultrasound signals are emitted into a medium and the echo pulses are displayed after an evaluation, with the following steps:

• a) emitting a transmission signal with any modulation function from at least one transmitter into a medium;
• b) receiving the echo signals from at least three receivers which are arranged separately from the transmitters and whose positions to the transmitters are known;
• c) correlation of the echo signals with the transmission signal for determining the paths of the transmission signal from the transmitter via a reflective structure in the medium to the respective receivers, by determining the pattern features of the transmission signal in the echo signals;
• d) determining the spatial coordinates and the quality of reflection and / or absorption of the reflecting structure from the results of step c) using triangulation; and
• e) displaying the spatial coordinates and the quality of reflection and / or absorption of the reflecting structure on a display device.

8. method for 3D real-time sonography according to claim 7, characterized in that in an arrangement with more as one transmitter, the individual transmitters are the same Send out transmission signals one after the other. 9. The method for 3D real-time sonography according to claim 7, characterized in that in an arrangement with more as a transmitter, the individual transmitters at the same time Transmission signals with different modulation functions send. 10. Method for 3D real-time sonography according to one of the Claims 7 to 9, characterized in that the Transmitted signal and the echo signals before the correlation be digitized. 11. The method for 3D real-time sonography according to claim 10, characterized in that the transmission signal in one Memory is stored and for controlling the transmission generator for generating the same again Transmission signal is used.