An isotropic elliptical trajectory scanning based photoacoustic brain imaging method and system

Abstract

The application discloses an equal-distance-ellipse-trajectory-scanning-based photoacoustic brain imaging method and system, and relates to the biomedical imaging technical field. The method comprises the following steps: constructing an equal-distance-ellipse-trajectory laser scanning system, setting the optical path distance of the equal-distance-ellipse-trajectory laser scanning system, and determining the scanning range of the equal-distance-ellipse-trajectory laser scanning system; acquiring equal-distance-ellipse parameters according to the scanning range of the equal-distance-ellipse-trajectory laser scanning system, and determining the dynamic-ellipse scanning trajectory of the equal-distance-ellipse-trajectory laser scanning system; generating an equal-distance-ellipse-trajectory driving signal according to the dynamic-ellipse scanning trajectory, controlling the equal-distance-ellipse-trajectory laser scanning system to perform scanning, and obtaining a three-dimensional photoacoustic brain imaging result. The application can reduce the edge distortion of an image by designing an equal-distance-ellipse scanning trajectory, and further significantly improves the resolution of brain imaging. The application can be widely applied to the biomedical imaging technical field as an equal-distance-ellipse-trajectory-scanning-based photoacoustic brain imaging method and system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biomedical imaging, in particular to a photoacoustic brain imaging method and system based on equidistant elliptical trajectory scanning. BACKGROUND

[0002] Photoacoustic imaging (PAI) is a non-invasive biomedical imaging technology that combines the high contrast of optical imaging and the high resolution of ultrasound imaging. It reconstructs the optical absorption distribution image of biological tissue by detecting the light-induced ultrasonic signal. The basic principle is that when pulsed laser irradiates biological tissue, the molecules in the tissue absorb light energy and convert it into heat energy, causing local temperature rise and thermal expansion, thereby generating ultrasonic waves. These ultrasonic waves are received by an ultrasonic detector and processed by an image reconstruction algorithm to ultimately generate an optical absorption distribution image of the tissue. Photoacoustic imaging technology can provide information about tissue structure, function and metabolism under non-invasive or minimally invasive conditions, and has great application potential in the fields of blood vessel imaging, tumor detection and neural imaging.

[0003] However, despite the many advantages of photoacoustic imaging technology, existing photoacoustic imaging systems still face some challenges in practical applications, especially in the field of brain imaging. Traditional photoacoustic imaging technology often uses straight or simple circular scanning paths, which are difficult to fully adapt to the complex anatomical structure and curvature characteristics of the brain, resulting in uneven detection coverage, limited imaging resolution, and susceptibility to skull acoustic interference. In addition, the existing scanning method is prone to motion artifacts in deep tissue imaging and difficult to achieve dynamic real-time monitoring. SUMMARY

[0004] To solve the above technical problems, the purpose of the present application is to provide a photoacoustic brain imaging method and system based on equidistant elliptical trajectory scanning, which can reduce image edge distortion by designing equidistant elliptical scanning trajectories, thereby significantly improving the resolution of brain imaging.

[0005] The first technical solution adopted by the present application is: a photoacoustic brain imaging method based on equidistant elliptical trajectory scanning, comprising the following steps:

[0006] Constructing an equidistant elliptical trajectory laser scanning system, setting the optical path distance of the equidistant elliptical trajectory laser scanning system, and determining the scanning range of the equidistant elliptical trajectory laser scanning system;

[0007] According to the scanning range of the equidistant elliptical trajectory laser scanning system, obtaining equidistant elliptical parameters, and determining the dynamic elliptical scanning trajectory of the equidistant elliptical trajectory laser scanning system;

[0008] An equidistant elliptical trajectory driving signal is generated according to the dynamic elliptical scanning trajectory to control the equidistant elliptical trajectory laser scanning system to perform scanning, thereby obtaining three-dimensional photoacoustic brain imaging results.

[0009] Furthermore, the steps of constructing the equidistant elliptical trajectory laser scanning system, setting the optical path distance of the equidistant elliptical trajectory laser scanning system, and determining the scanning range of the equidistant elliptical trajectory laser scanning system specifically include:

[0010] Construct an equidistant elliptical trajectory laser scanning system;

[0011] Based on the equidistant elliptical trajectory laser scanning system, an optical path distance of the equidistant elliptical trajectory laser scanning system is set, where the optical path distance represents the vertical distance between the scanning center point of the XY two-dimensional laser scanning device and the plane to be scanned;

[0012] According to the optical path distance of the equidistant elliptical trajectory laser scanning system, a mapping relationship between the scanning angle and the plane coordinate is established;

[0013] Combined with the mapping relationship between the scanning angle and the plane coordinates and the optical path distance of the equidistant elliptical trajectory laser scanning system, the scanning angle amplitude is determined to meet the conditions and the scanning range of the equidistant elliptical trajectory laser scanning system is determined.

[0014] Furthermore, the equidistant elliptical trajectory laser scanning system specifically includes several laser emitters, MEMS galvanometers, transducers, signal acquisition modules, DAC modules, control systems and user interface modules, wherein:

[0015] The plurality of laser emitters are used to emit laser beams;

[0016] The MEMS galvanometer is used to control the deflection of the laser beam according to the equidistant elliptical trajectory driving signal;

[0017] The transducer is used to receive the photoacoustic signal;

[0018] The signal acquisition module is used to synchronize laser pulse and ultrasonic signal sampling;

[0019] The DAC module is used to convert the digital drive signal into an analog voltage signal;

[0020] The control system is used to initialize the equidistant ellipse parameters and generate an equidistant ellipse trajectory driving signal;

[0021] The user interface module is used to receive user input and display three-dimensional photoacoustic brain imaging results.

[0022] Furthermore, the control system specifically includes a parameter setting module, a trajectory generation module and a signal processing module, wherein:

[0023] The parameter setting module is configured to initialize equidistant ellipse parameters according to a scanning range of the equidistant ellipse trajectory laser scanning system.

[0024] The trajectory generation module is configured to generate an equidistant ellipse trajectory driving signal based on the initialized equidistant ellipse parameters.

[0025] The signal processing module is configured to process a feedback signal from the MEMS galvanometer and adjust the driving signal.

[0026] Further, the step of obtaining equidistant ellipse parameters according to the scanning range of the equidistant ellipse trajectory laser scanning system and determining a dynamic ellipse scanning trajectory of the equidistant ellipse trajectory laser scanning system specifically includes:

[0027] According to the scanning range of the equidistant ellipse trajectory laser scanning system, equidistant ellipse parameters are obtained, including an ellipse base amplitude, a linear offset velocity coefficient, and an angular frequency.

[0028] According to the equidistant ellipse parameters, a dynamic ellipse scanning trajectory of the equidistant ellipse trajectory laser scanning system is determined.

[0029] Further, the step of generating an equidistant ellipse trajectory driving signal based on the dynamic ellipse scanning trajectory and controlling the equidistant ellipse trajectory laser scanning system to scan to obtain a three-dimensional photoacoustic brain imaging result specifically includes:

[0030] Based on the dynamic ellipse scanning trajectory, an equidistant ellipse trajectory driving signal is generated in combination with a deflection control mode of the MEMS galvanometer, and the deflection control mode of the MEMS galvanometer is to switch the deflection direction according to the parity of the scanning frame number.

[0031] The equidistant ellipse trajectory driving signal is converted into an analog voltage signal and combined with a photoacoustic signal for signal synchronization to obtain a synchronized equidistant ellipse trajectory driving signal.

[0032] By constraining the linear offset velocity and the single-frame time, an equidistant ellipse trajectory laser scanning range coverage condition is determined.

[0033] Based on the equidistant ellipse trajectory laser scanning range coverage condition, the synchronized equidistant ellipse trajectory driving signal is combined to control the equidistant ellipse trajectory laser scanning system to scan, reconstruct a photoabsorption distribution image, and obtain a three-dimensional photoacoustic brain imaging result.

[0034] Further, the expression of the equidistant ellipse trajectory driving signal is specifically as follows:

[0035]

[0036] In the above formula, x(t) and y(t) should represent functions of the positions of the scanning device on the X-axis and the Y-axis with respect to time t, Ax represents the X-axis half long axis in the elliptical base amplitude, By t represents the Y-axis half short axis in the elliptical base amplitude, By2 represents a linear offset velocity coefficient, ω represents an angular frequency, and N represents a direction control number.

[0037] Further, the equidistant elliptical trajectory laser scanning range coverage condition comprises a rectangular scanning area and a circular scanning area, wherein:

[0038] When the equidistant elliptical trajectory laser scanning range coverage condition is the rectangular scanning area, the dynamic adjustment of the elliptical rotation angle is performed to align the long axis direction with the long side of the rectangle.

[0039] When the equidistant elliptical trajectory laser scanning range coverage condition is the circular scanning area, the standard circular trajectory is degenerated.

[0040] Further, the expression for reconstructing the light absorption distribution image is specifically as follows:

[0041]

[0042] In the above formula, p(x, y, t) represents a time-domain sound pressure signal, v represents a sound speed, τ represents a time delay, z represents an imaging depth, I(x, y, z) represents three-dimensional body data, N represents a direction control number, and t represents time.

[0043] The second technical solution adopted by the present application is: a photoacoustic brain imaging system based on equidistant elliptical trajectory scanning, comprising:

[0044] The first module is configured to construct an equidistant elliptical trajectory laser scanning system, set the optical path distance of the equidistant elliptical trajectory laser scanning system, and determine the scanning range of the equidistant elliptical trajectory laser scanning system.

[0045] The second module is configured to obtain equidistant elliptical parameters according to the scanning range of the equidistant elliptical trajectory laser scanning system, and determine a dynamic elliptical scanning trajectory of the equidistant elliptical trajectory laser scanning system.

[0046] The third module is configured to generate an equidistant elliptical trajectory driving signal according to the dynamic elliptical scanning trajectory, control the equidistant elliptical trajectory laser scanning system to perform scanning, and obtain a three-dimensional photoacoustic brain imaging result.

[0047] The method and system have the advantages that the equal-distance elliptical trajectory laser scanning system is constructed, the optical path distance of the equal-distance elliptical trajectory laser scanning system is set, the scanning range of the equal-distance elliptical trajectory laser scanning system is determined, the equal-distance elliptical parameters are acquired according to the scanning range of the equal-distance elliptical trajectory laser scanning system, the dynamic elliptical scanning trajectory of the equal-distance elliptical trajectory laser scanning system is determined, the continuity in the scanning process is realized by designing the equal-distance elliptical scanning trajectory, the three-dimensional adaptability is enhanced, the system structure is simplified, the equal-distance elliptical trajectory driving signal is generated according to the dynamic elliptical scanning trajectory to control the equal-distance elliptical trajectory laser scanning system to scan, the edge distortion of an image is reduced while the galvanometer is controlled to quickly and widely scan, the resolution of brain imaging is significantly improved, and the service life of the galvanometer is prolonged. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 is a step flow chart of a photoacoustic brain imaging method based on equal-distance elliptical trajectory scanning according to the present application;

[0049] Figure 2 is a structural block diagram of a photoacoustic brain imaging system based on equal-distance elliptical trajectory scanning according to the present application;

[0050] Figure 3 is a step flow chart of equal-distance elliptical trajectory scanning according to the present application;

[0051] Figure 4 is a structural schematic diagram of an equal-distance elliptical trajectory laser scanning system according to the present application;

[0052] Figure 5 is a planar structural schematic diagram of a scanning result according to the present application;

[0053] Figure 6 is a driving waveform schematic diagram of a scanning trajectory according to the present application;

[0054] Figure 7 is a scanning trajectory schematic diagram according to the present application. DETAILED DESCRIPTION

[0055] The present application will be further described in detail below in combination with the drawings and specific embodiments. For the step numbers in the following embodiments, only the setting is for the convenience of description, and the order between the steps is not limited in any way, and the execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0056] First of all, it needs to be pointed out that the traditional laser scanning method has the following disadvantages:

[0057] 1) Scanning efficiency is low, and the return time of raster scanning accounts for more than 30%, so the effective scanning time is significantly shortened. This results in slow imaging speed, which is difficult to meet the needs of real-time dynamic monitoring.

[0058] 2) Trajectory coverage is insufficient, and fixed elliptical or spiral trajectories cannot adapt to complex scanning areas, making it difficult to achieve uniform coverage of the target area. This unevenness can lead to a decrease in imaging resolution and contrast, limiting the application of photoacoustic imaging in complex tissue structures.

[0059] 3) Large mechanical loss, sudden acceleration leads to shortened life of galvanometer, increases maintenance cost and use limit of equipment.

[0060] Therefore, although the scanning method of double helix structure can prolong the service life of scanning device and improve the scanning stability to some extent due to its continuous and non-sudden trajectory design, in the process of photoacoustic imaging, the scanning interval between the inner and outer circles of the spiral is different, resulting in uneven energy distribution of the scanning points in the inner and outer circles. This energy difference is easy to cause thermal damage to the tissue in the central scanning area, further limiting its application in biomedical imaging.

[0061] Based on this, the embodiment of the present application meets the comprehensive needs of large range, high speed and high precision in the field of laser scanning imaging. By designing an equidistant elliptical scanning trajectory, continuity in the scanning process is achieved, thereby enhancing three-dimensional adaptability and simplifying the system structure. In addition, the present application also improves the smoothness of the scanning trajectory, ensuring the continuity of the mirror rotation motion of the first axis and the second axis of the two-dimensional laser scanning device, effectively reducing the adjustment time required due to sudden mirror rotation, and thereby improving the scanning speed. The continuous and non-sudden scanning method not only helps to prolong the service life of the scanning device, but also significantly improves the stability of the scanning. These characteristics make the system have important application potential in the field of biomedical imaging, especially in the field of photoacoustic imaging technology, which combines the high contrast of optical imaging and the deep penetration of ultrasonic imaging, can reflect the distribution of endogenous absorbing substances in living organisms without labeling and non-invasively, and is suitable for imaging of rodent models whole brain.

[0062] Referring Figure 1 , the present application provides a photoacoustic brain imaging method based on equidistant elliptical trajectory scanning, which comprises the following steps:

[0063] S100, an equidistant elliptical trajectory laser scanning system is constructed, the optical path distance of the equidistant elliptical trajectory laser scanning system is set, and the scanning range of the equidistant elliptical trajectory laser scanning system is determined;

[0064] S110, an equidistant elliptical trajectory laser scanning system is constructed;

[0065] In this embodiment, asFigure 4 as well as Figure 5 As shown, Figure 4 The solid line in the figure represents the control flow, the dotted line between the laser emitter, the galvanometer and the scanning area represents the transmission of optical signals, and the dotted line between the scanning area, the ultrasonic transducer and the signal acquisition module represents the transmission of optical and acoustic signals. The equidistant elliptical trajectory laser scanning system specifically includes several laser emitters, MEMS galvanometers, transducers, signal acquisition modules, DAC modules, control systems and user interface modules, wherein the several laser emitters are used to emit laser beams; the MEMS galvanometers are used to control the deflection of the laser beam according to the equidistant elliptical trajectory driving signals; the transducers are used to receive photoacoustic signals; the signal acquisition module is used to synchronize laser pulses and ultrasonic signal sampling; the DAC module is used to convert digital driving signals into analog voltage signals; the control system is used to initialize equidistant elliptical parameters and generate equidistant elliptical trajectory driving signals; the user interface module is used to receive user input and display three-dimensional photoacoustic brain imaging results.

[0066] It should be further explained that the control system specifically includes a parameter setting module, a trajectory generation module and a signal processing module, wherein the parameter setting module is used to initialize the equidistant ellipse parameters according to the scanning range of the equidistant ellipse trajectory laser scanning system; the trajectory generation module is used to generate an equidistant ellipse trajectory driving signal based on the initialized equidistant ellipse parameters; the signal processing module is used to process the feedback signal from the MEMS galvanometer and adjust the driving signal.

[0067] S120, based on the equidistant elliptical trajectory laser scanning system, setting the optical path distance of the equidistant elliptical trajectory laser scanning system, where the optical path distance represents the vertical distance between the scanning center point of the XY two-dimensional laser scanning device and the plane to be scanned;

[0068] S130, establishing a mapping relationship between scanning angles and plane coordinates according to the optical path distance of the equidistant elliptical trajectory laser scanning system;

[0069] S140. Determine whether the scanning angle amplitude satisfies the conditions based on the mapping relationship between the scanning angle and the plane coordinates and the optical path distance of the equidistant elliptical trajectory laser scanning system, and determine the scanning range of the equidistant elliptical trajectory laser scanning system.

[0070] In this embodiment, if Figure 3 As shown, the optical path distance D of the scanning system is set, that is, the vertical distance between the scanning center point of the XY two-dimensional laser scanning device and the plane to be scanned, and the mapping relationship between the scanning angle and the plane coordinate is established. The specific expression is as follows:

[0071]

[0072] Among them, the scanning angle amplitude satisfies the following expression:

[0073]

[0074] In the above formula, the scanning angle θ x and θ y They represent the scanning angles of the two-dimensional laser scanning device on the X axis and Y axis, respectively. max and Y max Respectively represent the maximum size of the scanning area in the X-axis and Y-axis directions.

[0075] S200, acquiring equidistant ellipse parameters according to a scanning range of the equidistant ellipse trajectory laser scanning system, and determining a dynamic ellipse scanning trajectory of the equidistant ellipse trajectory laser scanning system;

[0076] S210, acquiring equidistant ellipse parameters according to a scanning range of the equidistant ellipse trajectory laser scanning system, wherein the equidistant ellipse parameters include an ellipse base amplitude, a linear offset velocity coefficient, and an angular frequency;

[0077] S220 , determining a dynamic elliptical scanning trajectory of the equidistant elliptical trajectory laser scanning system according to the equidistant ellipse parameters.

[0078] In this embodiment, if Figure 6 As shown, initialize the equidistant ellipse parameters and determine the following parameters according to the size of the scanning area:

[0079] 1) Ellipse basic amplitude A x (X-axis semi-major axis) and B yt (Y-axis semi-minor axis), its expression is:

[0080] A x =X max / 2

[0081] B y2 =Y max / (2k)

[0082] In the above formula, k represents the ellipse compression ratio to adapt to the aspect ratio of the rectangular scanning area.

[0083] 2) Linear offset speed coefficient B y2 (Unit: mm / s), its expression is:

[0084]

[0085] In the above formula, η∈[0.8,1.2] is the overlap rate adjustment factor.

[0086] Where T represents the single frame scanning time, and its expression is:

[0087]

[0088] In the above formula, n represents the number of complete periods of the single-frame elliptical trajectory.

[0089] 3) the angular frequency, expressed as:

[0090] ω = 2πf

[0091] In the above formula, f represents the scanning frequency (unit: Hz).

[0092] S300, generating an equidistant elliptical trajectory driving signal according to the dynamic elliptical scanning trajectory to control the equidistant elliptical trajectory laser scanning system to scan, and obtaining a three-dimensional photoacoustic brain imaging result.

[0093] S310, generating an equidistant elliptical trajectory driving signal based on the dynamic elliptical scanning trajectory and in combination with the deflection control mode of the MEMS scanner, wherein the deflection control mode of the MEMS scanner is to switch the deflection direction according to the parity of the scanning frame sequence number.

[0094] In this embodiment, based on the above-mentioned set parameters, the scanning trajectory is determined; the corresponding equidistant elliptical driving signal is generated according to the control mode of the used scanner, the deflection of the MEMS scanner is controlled, and thus the scanning trajectory of the laser is realized, wherein the expression of the equidistant elliptical trajectory driving signal is specifically as follows:

[0095]

[0096] In the above formula, x(t) and y(t) should represent functions of the positions of the scanning device on the X-axis and the Y-axis with respect to time t, A x represents the X-axis half major axis in the elliptical base amplitude, B yt represents the Y-axis half minor axis in the elliptical base amplitude, B y2 represents the linear offset velocity coefficient, ω represents the angular frequency, and N represents the direction control number.

[0097] Further, it needs to be explained that N ∈ {+1, -1} is the direction control number, which is switched according to the parity of the scanning frame sequence number, when the scanning frame sequence number is odd, N is set to +1, and when the scanning frame sequence number is even, N is set to -1.

[0098] S320, converting the equidistant elliptical trajectory driving signal into an analog voltage signal and combining the photoacoustic signal for signal synchronization, to obtain a synchronized equidistant elliptical trajectory driving signal.

[0099] In the embodiment, the driving signal is converted into an analog voltage by a high-precision DAC module, the galvanometer is controlled to deflect along an equidistant elliptical trajectory, and the photoacoustic signal is received synchronously by the transducer. When the signals are synchronously collected, the time delay integration (TDI) is used to achieve hard synchronization between the laser pulse emission and the ultrasonic signal reception, so that the time resolution of the photoacoustic signal is accurately corresponding to the scanning position.

[0100] In S330, the coverage condition of the equidistant elliptical trajectory laser scanning range is determined by restricting the linear offset speed and the single-frame time. In the embodiment, first, the following coverage conditions are met in the scanning process:

[0101] |B y2 ·T|≤2R yt

[0102] Further, by restricting the linear offset speed and the single-frame time, it is ensured that the elliptical trajectories of adjacent scanning frames are completely covered along the Y axis, and the scanning blind area is eliminated. When the scanning area is a rectangle, the rotation angle φ(t) of the ellipse is dynamically adjusted so that the long axis direction is aligned with the long side of the rectangle. When the scanning area is a circle, as shown in the following formula, it is degenerated into a standard circular trajectory: Figure 7 x =R yt , B y2 = 0.

[0103] In S340, the equidistant elliptical trajectory driving signal after synchronization is combined based on the coverage condition of the equidistant elliptical trajectory laser scanning range, the equidistant elliptical trajectory laser scanning system is controlled to scan, the photoabsorption distribution image is reconstructed, and the three-dimensional photoacoustic brain imaging result is obtained.

[0104] In the embodiment, after the collected ultrasonic signal is filtered and amplified, the time reversal algorithm or the delay and superposition algorithm is used to reconstruct the photoabsorption distribution image, and the three-dimensional body data is generated by the following formula, and the expression is:

[0105]

[0106] In the above formula, p(x, y, t) represents the time-domain acoustic pressure signal, v represents the sound speed, τ represents the time delay, z represents the imaging depth, I(x, y, z) represents the three-dimensional body data, N represents the number of direction controls, and t represents the time.

[0107] In summary, by optimizing the scanning path and the signal collection strategy, the resolution, the signal-to-noise ratio and the adaptability of the brain imaging are significantly improved. The main purpose of the present application is to reduce the edge distortion of the image while controlling the galvanometer to perform fast and large-angle scanning, and to prolong the service life of the galvanometer.

[0108] Referring to Figure 2 , a photoacoustic brain imaging system based on equidistant elliptical trajectory scanning comprises:​

[0109] The first module 201 is configured to construct an equidistance elliptical trajectory laser scanning system, set an optical path distance of the equidistance elliptical trajectory laser scanning system, and determine a scanning range of the equidistance elliptical trajectory laser scanning system.

[0110] The second module 202 is configured to acquire equidistance elliptical parameters according to the scanning range of the equidistance elliptical trajectory laser scanning system, and determine a dynamic elliptical scanning trajectory of the equidistance elliptical trajectory laser scanning system.

[0111] The third module 203 is configured to generate an equidistance elliptical trajectory driving signal according to the dynamic elliptical scanning trajectory, control the equidistance elliptical trajectory laser scanning system to perform scanning, and obtain a three-dimensional photoacoustic brain imaging result.

[0112] The contents in the method embodiments are applicable to the system embodiments, the system embodiments specifically implement the functions same as those of the method embodiments, and achieve the same beneficial effects as those of the method embodiments.

[0113] The above is a specific description of the preferred embodiments of the present application, but the present application is not limited to the embodiments, and those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present application, and these equivalent modifications or replacements are all included in the scope defined by the claims of the present application.

Claims

1. A photoacoustic brain imaging method based on equi-lateral elliptical trajectory scanning, characterized in that, The method comprises the following steps: constructing an equal-ellipse trajectory laser scanning system; The equal-ellipse trajectory laser scanning system specifically comprises a plurality of laser emitters, a MEMS mirror, a transducer, a signal acquisition module, a DAC module, a control system and a user interface module, wherein: The plurality of laser emitters are used to emit laser beams; The MEMS mirror is used to control the deflection of the laser beams according to an equal-ellipse trajectory driving signal; The transducer is used to receive photoacoustic signals; The signal acquisition module is used to synchronize laser pulses and ultrasonic signal sampling; The DAC module is used to convert digital driving signals into analog voltage signals; The control system is used to initialize equal-ellipse parameters and generate an equal-ellipse trajectory driving signal; The control system specifically comprises a parameter setting module, a trajectory generation module and a signal processing module, wherein: The parameter setting module is used to initialize equal-ellipse parameters according to the scanning range of the equal-ellipse trajectory laser scanning system; The trajectory generation module is used to generate an equal-ellipse trajectory driving signal based on the initialized equal-ellipse parameters; The signal processing module is used to process feedback signals from the MEMS mirror and adjust the driving signal; The user interface module is used to receive user input and display three-dimensional photoacoustic brain imaging results; Based on the equal-ellipse trajectory laser scanning system, the optical path distance of the equal-ellipse trajectory laser scanning system is set, which represents the vertical distance between the scanning center point of the X-Y two-dimensional laser scanning device and the plane to be scanned; According to the optical path distance of the equal-ellipse trajectory laser scanning system, a mapping relationship between the scanning angle and the plane coordinate is established; Combined with the mapping relationship between the scanning angle and the plane coordinate and the optical path distance of the equal-ellipse trajectory laser scanning system, it is determined that the scanning angle amplitude satisfies the condition, and the scanning range of the equal-ellipse trajectory laser scanning system is determined; According to the scanning range of the equal-ellipse trajectory laser scanning system, equal-ellipse parameters are obtained, including an ellipse base amplitude, a linear offset velocity coefficient and an angular frequency; According to the equal-ellipse parameters, a dynamic ellipse scanning trajectory of the equal-ellipse trajectory laser scanning system is determined; According to the dynamic ellipse scanning trajectory, an equal-ellipse trajectory driving signal is generated to control the equal-ellipse trajectory laser scanning system to scan, and three-dimensional photoacoustic brain imaging results are obtained.

2. The photoacoustic brain imaging method based on the equidistant elliptical trajectory scanning according to claim 1, characterized in that, The step of generating an equal-ellipse trajectory driving signal based on the dynamic ellipse scanning trajectory to control the equal-ellipse trajectory laser scanning system to scan and obtain three-dimensional photoacoustic brain imaging results specifically comprises: Based on the dynamic ellipse scanning trajectory, an equal-ellipse trajectory driving signal is generated combined with the deflection control mode of the MEMS mirror, which switches the deflection direction according to the parity of the scanning frame number; The equal-ellipse trajectory driving signal is converted into an analog voltage signal and combined with a photoacoustic signal for signal synchronization to obtain a synchronized equal-ellipse trajectory driving signal; By constraining the linear offset velocity and the single-frame time, the equal-ellipse trajectory laser scanning range coverage condition is determined; The equal-ellipse trajectory laser scanning system is controlled to scan based on an equal-ellipse trajectory laser scanning range coverage condition combined with a synchronized equal-ellipse trajectory driving signal, a light absorption distribution image is reconstructed, and a three-dimensional photoacoustic brain imaging result is obtained. 3.The photoacoustic brain imaging method based on the iso-centric elliptical trajectory scanning according to claim 2, characterized in that, An expression of the equal-ellipse trajectory driving signal is specifically as follows: In the above equation, x(t) and y(t) should represent functions of the position of the scanning device on the X and Y axes as a function of time t, A x represents the X axis half-long axis in the elliptical base amplitude, B y1 represents the Y axis half-short axis in the elliptical base amplitude, B y2 represents the linear offset velocity coefficient, ω represents the angular frequency, and N represents the direction control number.

4. The photoacoustic brain imaging method based on iso-centric elliptical trajectory scanning according to claim 3, characterized in that, The equal-ellipse trajectory laser scanning range coverage condition includes a rectangular scanning area and a circular scanning area, and wherein: When the equal-ellipse trajectory laser scanning range coverage condition is the rectangular scanning area, the ellipse rotation angle is dynamically adjusted so that the long axis direction is aligned with the long side of the rectangle; When the equal-ellipse trajectory laser scanning range coverage condition is the circular scanning area, it is degenerated into a standard circular trajectory.

5. The photoacoustic brain imaging method based on iso-centric elliptical trajectory scanning according to claim 4, characterized in that, An expression of the reconstructed light absorption distribution image is specifically as follows: In the above formula, p(x, y, t) represents a time-domain acoustic pressure signal, v represents a sound speed, τ represents a time delay, z represents an imaging depth, I(x, y, z) represents three-dimensional body data, N represents a direction control number, and t represents time.

6. A photoacoustic brain imaging system based on equi-lateral elliptical trajectory scanning, characterized in that, The method comprises the following modules: A first module is configured to construct an equal-ellipse trajectory laser scanning system. The equal-ellipse trajectory laser scanning system specifically comprises a plurality of laser emitters, a MEMS galvanometer, a transducer, a signal acquisition module, a DAC module, a control system, and a user interface module, wherein: The plurality of laser emitters are configured to emit laser beams. The MEMS galvanometer is configured to control deflection of the laser beams according to an equal-ellipse trajectory driving signal. The transducer is configured to receive photoacoustic signals. The signal acquisition module is configured to synchronize laser pulse and ultrasonic signal sampling. The DAC module is configured to convert a digital driving signal into an analog voltage signal. The control system is configured to initialize equal-ellipse parameters and generate an equal-ellipse trajectory driving signal. The control system specifically comprises a parameter setting module, a trajectory generation module, and a signal processing module, wherein: The parameter setting module is configured to initialize equal-ellipse parameters according to a scanning range of the equal-ellipse trajectory laser scanning system. The trajectory generation module is configured to generate an equal-ellipse trajectory driving signal based on the initialized equal-ellipse parameters. The signal processing module is configured to process feedback signals from the MEMS galvanometer and adjust the driving signal. The user interface module is configured to receive user input and display a three-dimensional photoacoustic brain imaging result. Based on the equal-ellipse trajectory laser scanning system, an optical path distance of the equal-ellipse trajectory laser scanning system is set, the optical path distance representing a vertical distance between a scanning center point of an X-Y two-dimensional laser scanning device and a to-be-scanned plane. According to the optical path distance of the equal-ellipse trajectory laser scanning system, a mapping relationship between a scanning angle and a plane coordinate is established; combined with the mapping relationship between the scanning angle and the plane coordinate and the optical path distance of the equal-ellipse trajectory laser scanning system, a scanning angle amplitude value satisfying a condition is determined, and a scanning range of the equal-ellipse trajectory laser scanning system is determined. A second module is configured to obtain equal-ellipse parameters according to the scanning range of the equal-ellipse trajectory laser scanning system, the equal-ellipse parameters including an ellipse base amplitude, a linear offset velocity coefficient, and an angular frequency. According to the equidistant ellipse parameter, a dynamic ellipse scanning track of the equidistant ellipse track laser scanning system is determined; The third module is configured to generate an equidistant ellipse track driving signal according to the dynamic ellipse scanning track, control the equidistant ellipse track laser scanning system to perform scanning, and obtain a three-dimensional photoacoustic brain imaging result.

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