CN118603895A - A photoacoustic imaging device and method based on multi-wavelength LED excitation - Google Patents

Abstract

The present invention discloses a photoacoustic imaging device and method based on multi-wavelength LED excitation, which relates to the field of material property determination and visualization, so as to realize low-cost, small-volume, multi-wavelength, and high-precision photoacoustic imaging. Each LED array of the LED module of the present invention is composed of a plurality of LED sub-arrays arranged in an array, the wavelengths of the LEDs between the LED sub-arrays are different, and the optical power of each LED sub-array is in the same interval. Under the control of a host computer, a motion control module moves an ultrasonic transducer to a specified position, drives the LED module to emit a nanosecond pulse light beam to act on an imaging sample through an LED driving circuit, and uses a photoacoustic signal acquisition module to collect and store the ultrasonic signal generated by the imaging sample, and the host computer performs image reconstruction. The present invention uses a low-cost, small-volume LED as an excitation source, and the LED array includes multi-wavelength, same-power LED sub-arrays, and realizes multi-wavelength, high-precision imaging under the control of nanosecond signals.

Description

A photoacoustic imaging device and method based on multi-wavelength LED excitation

Technical Field

The invention relates to the field of material property measurement and visualization, and in particular to a photoacoustic imaging device and method based on multi-wavelength LED excitation.

Background Art

Photoacoustic imaging is an emerging radiation-free, non-invasive imaging technology in recent years. It is also the key to overcoming the limited depth of optical imaging. It plays a supporting role in material property analysis, pathological analysis, biochemical research, etc. Because it has the advantages of high contrast and high resolution of optical imaging and low attenuation and high penetration of ultrasonic imaging, it has been widely used in the fields of physical property determination of biomaterials in recent years. At present, photoacoustic imaging is widely used in the fields of tumor hypoxia in vivo monitoring. However, the nanosecond pulse laser source used in the excitation source of traditional photoacoustic imaging, such as the photoacoustic imaging system proposed in the Chinese patent document with publication number CN110367942A, uses a laser as an excitation source to achieve photoacoustic three-dimensional imaging. However, due to the disadvantages of its pulse laser source, such as high price, large size, and strict use conditions, it limits the development of photoacoustic imaging to a certain extent.

With the development of semiconductor technology, LED (light-emitting diode) is more and more widely used. Compared with traditional pulsed laser sources, LED excitation sources are 50-100 times cheaper and extremely small in size. In comparison, LED-based photoacoustic imaging excitation sources have the advantages of low cost, portability, and ease of use. For example, a handheld photoacoustic imaging device proposed in a Chinese patent document with publication number CN112603263A uses LED/LD as an excitation light source to achieve real-time display imaging on the palm. However, its single-wavelength excitation light source cannot meet the requirements of differentiated imaging such as blood oxygen quantitative measurement.

Based on the excitation source of multi-wavelength LED, different light absorbers in the target tissue can be visualized separately, thereby achieving more fine-grained imaging. For example, in the quantitative measurement of blood oxygen, by dynamically tracking the tissue distribution of hemoglobin and molecular probes, photoacoustic imaging can analyze the blood oxygen changes (SO2) and molecular responses in tumor tissue in real time, which can achieve the quantitative measurement of blood oxygen in the hypoxic area of the tumor and provide more accurate information for clinical diagnosis and treatment. For example, the Chinese patent document with publication number CN112557302A proposes a multi-wavelength photoacoustic imaging drive system, which realizes multi-wavelength excitation by setting a continuous laser with multiple wavelengths. Or the multi-wavelength photoacoustic sensing and imaging method based on mixed pulse continuous laser disclosed in the Chinese patent document with publication number CN106338473A, which selects multiple continuous lasers of different wavelengths to heat the object to be measured. However, they all achieve wavelength tunability through selective light emission, and in essence each time step is still single-wavelength operation. In addition, the optical power of each wavelength laser in the multiple wavelengths cannot be kept stable, resulting in different excitations for different light absorbers and obvious imaging differences.

Summary of the invention

The object of the present invention is to provide a photoacoustic imaging device and method based on multi-wavelength LED excitation to achieve low-cost, small-volume, multi-wavelength, and high-precision photoacoustic imaging in order to address all or part of the above-mentioned problems.

The technical solution adopted by the present invention is as follows:

A photoacoustic imaging device based on multi-wavelength LED excitation comprises a host computer, an LED driving circuit, an LED module, a photoacoustic signal acquisition module, a motion control module and a water tank, wherein the water tank contains a lipid medium; wherein:

The motion control module is configured to: in response to a movement instruction sent by the host computer, drive the ultrasonic transducer of the photoacoustic signal acquisition module to move to a specified position;

The LED driving circuit is configured to: in response to the pulse instruction of the host computer, drive the LED module to emit a pulse light beam to act on the imaging sample, so that the imaging sample generates an ultrasonic signal;

The LED module includes a plurality of LED arrays, each of which faces the same position; each LED array is formed by a plurality of LED sub-arrays arranged in an array, each LED sub-array includes at least one LED, the wavelengths of the LEDs in each LED sub-array are different, and the optical power of each LED sub-array is in the same range;

The photoacoustic signal acquisition module is configured to: acquire the ultrasonic signal generated by the imaging sample through the ultrasonic transducer, and store the acquired ultrasonic signal;

The imaging sample, the LED module and the ultrasonic transducer are all located in the lipid medium in the water tank;

The host computer is configured to: generate a movement instruction and send the movement instruction to the motion control module; send a pulse instruction to the LED drive circuit; and perform image reconstruction according to the ultrasound signal stored in the photoacoustic signal acquisition module.

Furthermore, the LED arrays of the LED module are arranged in a circular shape, and each LED array faces the center of the circle.

Furthermore, the LEDs of each LED subarray of the LED array are arranged layer by layer from inside to outside with the same geometric center, and in each two adjacent layers of LED subarrays, the wavelength of the inner layer LED is larger than that of the outer layer LED, and the number of the inner layer LEDs is less than that of the outer layer LEDs.

Furthermore, the LEDs of the LED sub-arrays with more than one LED are evenly arranged on a circular ring with the geometric center as the center.

Furthermore, the LED array includes at least three layers of LED sub-arrays, and each layer of LED sub-arrays from the inner to the outer comprises LEDs, n is a natural number, representing the circle levels of the LED sub-array from the inside to the outside.

Furthermore, the host computer is also configured as follows:

The blood oxygen quantification is measured according to the ultrasonic signal stored in the photoacoustic signal acquisition module.

Furthermore, the motion control module includes a three-dimensional turntable, the ultrasonic transducer is connected to the free end of the three-dimensional turntable, and the free end of the three-dimensional turntable extends vertically into the lipid medium; the turntable motor of the three-dimensional turntable is connected to the host computer.

Furthermore, the photoacoustic signal acquisition module also includes an amplifier and a data acquisition card, the data acquisition card is connected to the host computer, and the amplifier is connected between the data acquisition card and the ultrasonic transducer.

Furthermore, the LED driving circuit includes a voltage-stabilizing power supply circuit, a high-voltage power supply circuit, a driving circuit, a switching circuit and an energy storage circuit; wherein:

The voltage-stabilized power supply circuit provides a DC power supply for the driving circuit, and the high-voltage power supply circuit provides a high-voltage power supply for the energy storage circuit;

The driving circuit is connected to the host computer and the switch circuit respectively, and sends a pulse signal to the switch circuit according to the pulse instruction of the host computer;

The energy storage circuit, the switch circuit and the LED module are connected in series to form a ground loop. The switch circuit closes or opens the ground loop in response to a received pulse signal.

The present invention also provides a photoacoustic imaging method based on the above-mentioned photoacoustic imaging device based on multi-wavelength LED excitation, which comprises the following steps:

Operate the host computer to generate a movement command, and the host computer sends the movement command to the motion control module;

The motion control module drives the ultrasonic transducer to move to a specified position according to the received movement instruction;

The host computer is configured to generate a pulse instruction, and the host computer sends the pulse instruction to the LED driving circuit;

The LED driving circuit drives the LED module to emit a pulse light beam according to the received pulse instruction, and the pulse light beam acts on the imaging sample, and the imaging sample generates an ultrasonic signal under the action of the pulse light beam;

The ultrasonic signal is collected by using an ultrasonic transducer of a photoacoustic signal collection module, and the collected ultrasonic signal is stored by the photoacoustic signal collection module;

The ultrasonic signal stored in the photoacoustic signal acquisition module is acquired through the host computer, and the image is reconstructed according to the acquired ultrasonic signal.

In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

1. The photoacoustic imaging device based on multi-wavelength LED excitation of the present invention uses LED as a pulse source to achieve the excitation energy required for photoacoustic imaging in a low-cost and small-volume manner. It can also emit lasers of multiple wavelengths at the same time to act on imaging samples, which can meet the needs of blood oxygen concentration measurement and other scenarios.

2. The LED module of the present invention adopts an algorithm for layout, taking into account the design concepts of multi-wavelength and equal power, ensuring that the radiation energy of light from LED arrays of different wavelengths on the imaging sample tends to be equal, avoiding the difference in imaging of different light absorbers, making it more practical in fields such as material property measurement, while also ensuring the measurement efficiency, and having excellent application prospects in medical testing and clinical applications.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a structural diagram of a photoacoustic imaging device based on multi-wavelength LED excitation according to the present invention.

FIG. 2 is a diagram showing the LED array structure of a photoacoustic imaging device based on multi-wavelength LED excitation according to the present invention.

FIG. 3 is a light field simulation diagram of the LED sub-arrays with wavelengths of 860 nm, 730 nm, and 650 nm in FIG. 2 working alone.

FIG. 4 is a circuit diagram of an LED driving circuit of a photoacoustic imaging device based on multi-wavelength LED excitation according to the present invention.

FIG5 is a signal transmission flow chart of the photoacoustic imaging device based on multi-wavelength LED excitation of the present invention.

FIG. 6 is a system hardware test diagram of the photoacoustic imaging device based on multi-wavelength LED excitation of the present invention.

FIG. 7 is a test diagram of an ultrasonic signal collected by an ultrasonic transducer.

In the figure, 1 is an LED module, 2 is an ultrasonic transducer, 3 is a motion control module, 31 is a turntable motor, 4 is a water tank, 5 is an imaging sample, and 6 is an LED array.

DETAILED DESCRIPTION

All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and/or steps, can be combined in any manner.

Any feature disclosed in this specification (including any additional claims and abstract), unless otherwise stated, may be replaced by other alternative features that are equivalent or have similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

Example 1

A photoacoustic imaging device based on multi-wavelength LED excitation, as shown in FIG1 , includes a host computer (such as a computer, not shown in the figure), an LED driving circuit (not shown), an LED module 1, a photoacoustic signal acquisition module, a motion control module 3 and a water tank 4. The water tank 4 contains a lipid medium, which serves as a contrast agent for photoacoustic imaging, provides an imaging environment for an imaging sample 5, and helps to improve the contrast and resolution of the photoacoustic imaging.

The host computer is configured to generate a movement instruction and send the movement instruction to the motion control module 3. Usually, by setting a detection area in the host computer, the host computer analyzes the detection area to obtain the coordinates of the detection area, and plans a movement strategy based on the coordinates and the current position of the ultrasonic transducer 2, and generates a movement instruction based on the movement strategy and sends it to the motion control module 3.

The motion control module 3 is configured to drive the ultrasonic transducer 2 of the photoacoustic signal acquisition module to move to a specified position in response to a movement instruction sent by the host computer.

The host computer is further configured to send a pulse instruction to the LED driving circuit. The LED driving circuit is configured to drive the LED module 1 to emit a pulse light beam in response to the pulse instruction of the host computer, and act on the imaging sample 5 so that the imaging sample 5 generates an ultrasonic signal (i.e., a photoacoustic signal).

During detection, the imaging sample 5 , the LED module 1 and the ultrasonic transducer 2 are all located in the lipid medium in the water tank 4 .

The LED module 1 includes a plurality of LED arrays 6, each of which faces the same position to work together on the imaging sample 5 at that position. Each LED array 6 is composed of a plurality of LED sub-arrays arranged in an array, each LED sub-array includes at least one LED, the wavelengths of the LEDs between the LED sub-arrays are different, and the optical power of each LED sub-array is in the same range, that is, the difference between the optical powers is within a set threshold, or within a set order of magnitude. In this way, the LED module 1 achieves multi-wavelength, same-power excitation of the imaging sample 5 through an optimized layout.

After the imaging sample 5 generates an ultrasonic signal, the ultrasonic signal is collected by the photoacoustic signal collection module and can be used for image reconstruction. The photoacoustic signal collection module is configured to: collect the ultrasonic signal generated by the imaging sample 5 through the ultrasonic transducer 2, and store the collected ultrasonic signal.

The host computer is further configured to: reconstruct an image according to the ultrasound signal stored in the photoacoustic signal acquisition module. Alternatively, the host computer is further configured to measure blood oxygen quantification according to the ultrasound signal stored in the photoacoustic signal acquisition module.

As a major focus of the present invention, the design of the LED module 1 takes into account the design concept of multiple wavelengths and the same power. In some embodiments, the LED array 6 of the LED module 1 is arranged in a circular ring, and each LED array 6 is facing the center of the ring. During testing, the imaging sample 5 is placed in the center of the ring. As shown in Figure 1, in some embodiments, 32 (or other numbers, only for example here) LED arrays 6 are designed to be arranged in a circular ring to form an LED module 1, and each LED array 6 is designed on a 2.5cm×2.5cm aluminum substrate. This power-type LED pulse light source has a wider wavelength coverage, a higher pulse frequency and a smaller duty cycle, thereby reducing the repetition rate.

The circular arrangement enables the LED array 6 to irradiate the entire circumference of the imaging sample 5. The excitation of multiple LED arrays 6 can increase the power of the imaging sample 5, thereby improving the imaging accuracy. At the same time, the uniformly arranged LED array 6 can ensure the uniformity of the excitation of the imaging sample 5.

As shown in FIG2 , in some embodiments, the LEDs of each LED subarray of the LED array 6 are arranged layer by layer from the inside to the outside with the same geometric center, that is, each LED subarray is distributed on the same layer. For example, the LEDs of the LED subarray with more than one LED are evenly arranged on a circular ring with the geometric center as the center, and the LED subarray with one LED is located at the geometric center.

In each of two adjacent layers of LED sub-arrays, the wavelength of the inner layer LED is larger than that of the outer layer LED, and the number of the inner layer LED is smaller than that of the outer layer LED. In this way, the optical power of different LED sub-arrays tends to be the same.

Taking the LED array 6 of FIG. 2 as an example, in some embodiments, the geometric center is an LED with a typical peak wavelength of 860 nm and a size of 1.5 mm×1.5 mm. Since there is only one LED and no annular band is formed, it serves as the 0th layer LED subarray. The first circle is an LED with a typical peak wavelength of 730 nm, a size of 3.0 mm×3.0 mm, and a number of 4 LEDs. These 4 LEDs are arranged to form the first layer LED subarray. The second circle is an LED with a typical peak wavelength of 640 nm, a size of 3.0 mm×3.0 mm, and a number of 8 LEDs. These 8 LEDs are arranged to form the second layer LED subarray. Under this arrangement, it can be achieved that the energy generated by LEDs of different wavelengths in the imaging area is roughly equal. The simulation results of the LED array 6 are shown in FIG. 3. The darker the grayscale, the greater the light power. From left to right, they are schematic diagrams of LED radiation light power with wavelengths of 860nm, 730nm, and 650nm. It can be seen from the figure that the light power of the LED sub-arrays at each wavelength at the geometric center position is roughly the same. After testing, the light power radiated by the three LED sub-arrays is 0.13114W, 0.13533W, and 0.13615W, respectively, verifying the effectiveness of the LED array 6 layout.

The LED array 6 in FIG2 is only an example, and more LED sub-arrays can be designed based on this. The number of LEDs in each layer of the LED sub-array follows (n is a natural number, representing the circle level of the LED sub-array from the inside to the outside), for example, the 0th layer LED sub-array contains 1 LED, the 1st layer is 4, the 2nd layer is 8, and so on.

As mentioned above, the ultrasonic transducer 2 is moved to a specified position by the motion control module 3, and the ultrasonic transducer 2 needs to extend into the lipid medium of the water tank 4. Due to the obstruction of the water tank 4, the motion control module 3 needs to have multiple dimensions of freedom to facilitate the movement of the ultrasonic transducer 2.

In some embodiments, the motion control module 3 includes a three-dimensional turntable, and the ultrasonic transducer 2 is connected to the free end of the three-dimensional turntable. The free end of the three-dimensional turntable extends vertically into the lipid medium. The turntable motor 31 of the three-dimensional turntable is connected to the host computer. The three-dimensional turntable has three degrees of freedom of motion in the x-axis, y-axis, and z-axis. A turntable motor 31 that controls the motion of the dimension can be designed on each axis. Each turntable motor 31 can be a stepper motor and connected to the host computer respectively. The host computer can obtain the motion of each dimension of the three-dimensional turntable, for example, by measuring with a grating ruler, and then control the motion of each turntable motor 31 of the three-dimensional turntable through PID (Proportional-Integral-Derivative) and the like to move the ultrasonic transducer 2 to a specified position.

The photoacoustic signal acquisition module includes an amplifier and a data acquisition card in addition to the ultrasonic transducer 2. The data acquisition card is connected to the host computer, and the amplifier is connected between the data acquisition card and the ultrasonic transducer 2.

The ultrasonic transducer 2 is used to capture the ultrasonic signal generated by the imaging sample 5 and convert it into an analog electrical signal. However, the power of the electrical signal output by the ultrasonic transducer 2 is very small, so it needs to be amplified by an amplifier to improve the sensitivity and resolution of imaging. The amplifier can amplify electrical signals at the microvolt level. Afterwards, the amplified electrical signal is collected and stored by the data acquisition card. In the present invention, the data acquisition card can perform multi-channel parallel analog-to-digital conversion and storage operations under the control of the host computer to efficiently process and record the amplified electrical signal.

As a key module for driving the LED module 1 to emit a pulsed light beam, the LED driving circuit needs to be driven stably, timely and efficiently. In some embodiments, the LED driving circuit includes a voltage-stabilizing power supply circuit, a high-voltage power supply circuit, a driving circuit, a switching circuit and an energy storage circuit. Among them:

The voltage-stabilized power supply circuit provides a direct current power supply for the driving circuit, and the high-voltage power supply circuit provides a high-voltage power supply for the energy storage circuit.

The driving circuit is connected to the host computer and the switch circuit respectively, and sends a pulse signal to the switch circuit according to the pulse instruction of the host computer.

The energy storage circuit, the switch circuit and the LED module 1 are connected in series to form a ground loop. The switch circuit closes or opens the ground loop in response to the received pulse signal.

As shown in FIG4, an embodiment of the circuit structure of the LED driving circuit is shown. The circuit can be laid out on a 10 cm × 6 cm PCB (Printed Circuit Board), which greatly simplifies the pulse light source excitation method, not only improving reusability, but also reducing manufacturing costs. The driving circuit uses FPGA (Field Programmable Gate Array) to obtain other pulse signal generators, which are programmed and burned by Quartus to achieve the generation of pulse signals with an adjustable repetition frequency of 0-10 kHz and an adjustable pulse width of 0-1 ms.

The high-voltage power supply outputs an adjustable high-voltage power supply of 0-1000V and 0-3A, such as the 370V high-voltage power supply provided in FIG. 4 . The high-voltage power supply is used to charge the energy storage circuit.

According to the pulse instruction of the host computer, the FPGA generates a pulse signal of high level 5V and low level 0V and sends it to the switch circuit. When the switch circuit is at high level 5V, the ground loop is closed. At this time, the voltage stored in the energy storage circuit is released through LED module 1, and LED module 1 is lit; when the switch circuit is at low level 0V, the ground loop is disconnected. At this time, the high-voltage power supply recharges the energy storage circuit, and LED module 1 is extinguished due to no current passing through. This is repeated. Under the action of the pulse signal, the switch circuit closes and disconnects the ground loop at high frequency, realizing high-frequency lighting and extinguishing of LED module 1, thus emitting a pulse light signal.

In the embodiment shown in FIG4 , the pulse signal generated by the FPGA is converted by the electro-optical conversion module, and then the optical fiber transmitter emits an optical pulse signal. The electro-optical conversion module and the optical fiber conversion head are both provided with a 5V DC power supply by a voltage-stabilized power supply circuit. The optical pulse signal is received by the optical fiber receiving head and converted into an electrical pulse signal. The switching circuit includes a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) driver and a MOSFET. The electrical pulse signal of the optical fiber receiving head is output to the MOSFET driver. The output end of the MOSFET driver is connected to the gate of the MOSFET. The source and drain of the MOSFET are connected in series to the loop of the LED module 1 and the energy storage circuit. The MOSFET driver generates a pulse voltage signal according to the input electrical pulse signal and acts on the gate of the MOSFET. The MOSFET is periodically turned on and off according to the law of the pulse voltage signal to realize the periodic discharge of the energy storage circuit. In this way, the LED module 1 generates a pulse beam with high overload, high repetition rate and narrow pulse.

The total volume of the photoacoustic imaging device of this embodiment is much smaller than that of common lasers such as OPO (Optical Parametric Oscillator, optical parametric oscillator), and the total cost is much lower than that of traditional lasers.

Example 2

Based on the photoacoustic imaging device based on multi-wavelength LED excitation in Example 1, this example introduces a photoacoustic imaging method.

FIG5 is a signal transmission flow chart of a photoacoustic imaging device based on multi-wavelength LED excitation. Referring to the flow chart, the photoacoustic imaging method includes the following steps:

S1. Operate the host computer to generate a movement instruction, and the host computer sends the movement instruction to the motion control module 3.

The so-called operation of the host computer refers to Example 1, that is, configuring the detection area or inputting the control instruction on the host computer so that the host computer obtains the target position or motion instruction. The host computer then generates a specific movement instruction to control the motion control module 3.

S2. The motion control module 3 drives the ultrasonic transducer 2 to move to a specified position according to the received movement instruction.

S3. Configure the host computer to generate a pulse instruction, and the host computer sends the pulse instruction to the LED drive circuit.

By writing a nanosecond pulse control program and loading it into the host computer, a nanosecond control pulse instruction is generated, and then the LED driving circuit realizes nanosecond control of lighting or extinguishing the LED module 1.

S4. The LED driving circuit drives the LED module 1 to emit a pulse light beam according to the received pulse instruction. The pulse light beam acts on the imaging sample 5. The imaging sample 5 generates an ultrasonic signal under the action of the pulse light beam.

S5. Collect the ultrasonic signal using the ultrasonic transducer 2 of the photoacoustic signal collection module, and store the collected ultrasonic signal through the photoacoustic signal collection module.

S6. The host computer obtains the ultrasonic signal stored in the photoacoustic signal acquisition module, and reconstructs the image based on the acquired ultrasonic signal. The host computer reconstructs the imaging object by filtering back projection, model-based, notch filtering, statistical weighted model-based, median filtering and other algorithms on the ultrasonic signal. Furthermore, for biological tissue samples, blood oxygen quantification can also be calculated based on the imaging results.

After testing the device, the upper computer gave a narrow pulse and high repetition rate pulse signal, and the LED drive circuit and LED module 1 both worked in an ideal state. As shown in Figure 6, curve 1 is a pulse signal, which controls the MOSFET switch and then controls the LED on and off. Curve 3 is the pulse current of the LED measured by the current sensor, and curve 2 is the pulse beam measured by the photodetector. Although the pulse current and pulse beam of the LED are delayed with the pulse signal, the response degree of the pulse beam to the pulse current is ideal.

In this embodiment, pencil lead is used as imaging sample 5, and LED module 1 is used to irradiate above the ultrasonic coupling medium. The data collected by ultrasonic transducer 2 is averaged 5000 times in MATLAB, and then filtered through a 0.1MHz-8MHz bandpass filter. The final imaging result is shown in Figure 7. In the absence of imaging sample 5, no ultrasonic signal is found; when the distance between ultrasonic transducer 2 and imaging sample 5 is changed, the time when ultrasonic signal appears will also change accordingly, which preliminarily verifies the feasibility of the photoacoustic imaging device based on multi-wavelength LED excitation.

The present invention is not limited to the aforementioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims (10)

1. A photoacoustic imaging device based on multi-wavelength LED excitation, characterized in that it comprises a host computer, an LED driving circuit, an LED module (1), a photoacoustic signal acquisition module, a motion control module (3) and a water tank (4), wherein the water tank (4) contains a lipid medium; wherein: The motion control module (3) is configured to: in response to a movement instruction sent by the host computer, drive the ultrasonic transducer (2) of the photoacoustic signal acquisition module to move to a specified position; The LED driving circuit is configured to: in response to a pulse instruction from the host computer, drive the LED module (1) to emit a pulse light beam to act on the imaging sample (5), so that the imaging sample (5) generates an ultrasonic signal; The LED module (1) comprises a plurality of LED arrays (6), each LED array (6) facing the same position; each LED array (6) is formed by a plurality of LED sub-arrays arranged in an array, each LED sub-array comprises at least one LED, the wavelengths of the LEDs in each LED sub-array are different, and the optical power of each LED sub-array is in the same range; The photoacoustic signal acquisition module is configured to: acquire the ultrasonic signal generated by the imaging sample (5) through the ultrasonic transducer (2), and store the acquired ultrasonic signal; The imaging sample (5), the LED module (1) and the ultrasonic transducer (2) are all located in the lipid medium in the water tank (4); The host computer is configured to: generate a movement instruction and send the movement instruction to the motion control module (3); send a pulse instruction to the LED drive circuit; and perform image reconstruction according to the ultrasound signal stored in the photoacoustic signal acquisition module. 2. The photoacoustic imaging device based on multi-wavelength LED excitation according to claim 1, characterized in that the LED array (6) of the LED module (1) is arranged in a circular ring shape, and each LED array (6) faces the center of the ring. 3. The photoacoustic imaging device based on multi-wavelength LED excitation according to claim 1 or 2, characterized in that the LEDs of each LED sub-array of the LED array (6) are arranged layer by layer from the inside to the outside with the same geometric center, and in each two adjacent layers of LED sub-arrays, the wavelength of the inner layer LED is larger than the wavelength of the outer layer LED, and the number of the inner layer LEDs is less than the number of the outer layer LEDs. 4. The photoacoustic imaging device based on multi-wavelength LED excitation as described in claim 3 is characterized in that the LEDs of the LED sub-array with more than one LED are evenly arranged on a circular ring with the geometric center as the center. 5. The photoacoustic imaging device based on multi-wavelength LED excitation according to claim 4, characterized in that the LED array (6) comprises at least three layers of LED sub-arrays, and each layer of LED sub-arrays from the inner to the outer comprises LEDs, n is a natural number, representing the circle levels of the LED sub-array from the inside to the outside. 6. The photoacoustic imaging device based on multi-wavelength LED excitation according to claim 1, characterized in that the host computer is further configured as: The blood oxygen quantification is measured according to the ultrasonic signal stored in the photoacoustic signal acquisition module. 7. The photoacoustic imaging device based on multi-wavelength LED excitation as described in claim 1 is characterized in that the motion control module (3) includes a three-dimensional turntable, the ultrasonic transducer (2) is connected to the free end of the three-dimensional turntable, and the free end of the three-dimensional turntable extends vertically into the lipid medium; the turntable motor (31) of the three-dimensional turntable is connected to the host computer. 8. The photoacoustic imaging device based on multi-wavelength LED excitation according to claim 1, characterized in that the photoacoustic signal acquisition module also includes an amplifier and a data acquisition card, the data acquisition card is connected to the host computer, and the amplifier is connected between the data acquisition card and the ultrasonic transducer (2). 9. The photoacoustic imaging device based on multi-wavelength LED excitation according to claim 1, characterized in that the LED driving circuit comprises a voltage-stabilizing power supply circuit, a high-voltage power supply circuit, a driving circuit, a switching circuit and an energy storage circuit; wherein: The voltage-stabilized power supply circuit provides a DC power supply for the driving circuit, and the high-voltage power supply circuit provides a high-voltage power supply for the energy storage circuit; The driving circuit is connected to the host computer and the switch circuit respectively, and sends a pulse signal to the switch circuit according to the pulse instruction of the host computer; The energy storage circuit, the switch circuit and the LED module (1) are connected in series to form a ground loop, and the switch circuit closes or opens the ground loop in response to a received pulse signal. 10. A photoacoustic imaging method based on the photoacoustic imaging device based on multi-wavelength LED excitation according to any one of claims 1 to 9, characterized in that it comprises the following steps: The host computer is operated to generate a movement instruction, and the host computer sends the movement instruction to the motion control module (3); The motion control module (3) drives the ultrasonic transducer (2) to move to a designated position according to the received movement instruction; The host computer is configured to generate a pulse instruction, and the host computer sends the pulse instruction to the LED driving circuit; The LED driving circuit drives the LED module (1) to emit a pulse light beam according to the received pulse instruction, and the pulse light beam acts on the imaging sample (5), and the imaging sample (5) generates an ultrasonic signal under the action of the pulse light beam; The ultrasonic signal is collected by using an ultrasonic transducer (2) of a photoacoustic signal collection module, and the collected ultrasonic signal is stored by the photoacoustic signal collection module; The ultrasonic signal stored in the photoacoustic signal acquisition module is acquired through the host computer, and the image is reconstructed according to the acquired ultrasonic signal.