Photoacoustic brain imaging method and system based on isometric elliptical trajectory scanning

Abstract

The invention discloses a photoacoustic brain imaging method and system based on isometric elliptical orbit scanning, and the method comprises the steps: constructing an isometric elliptical orbit laser scanning system, setting the optical path distance of the isometric elliptical orbit laser scanning system, and determining the scanning range of the isometric elliptical orbit laser scanning system; according to the scanning range of the equidistant elliptic track laser scanning system, equidistant elliptic parameters are obtained, and a dynamic elliptic scanning track of the equidistant elliptic track laser scanning system is determined; and according to the dynamic elliptical scanning track, generating an equidistant elliptical track driving signal to control an equidistant elliptical track laser scanning system to scan to obtain a three-dimensional photoacoustic brain imaging result. According to the method, the edge distortion of the image can be reduced by designing the equidistant elliptical scanning track, so that the resolution of brain imaging is remarkably improved. The photoacoustic brain imaging method and system based on isometric elliptical trajectory scanning can be widely applied to the technical field of biomedical imaging.

Description

Technical Field

[0001] The present invention relates to the field of biomedical imaging technology, and particularly to a photoacoustic brain imaging method and system based on equidistant elliptical trajectory scanning. Background Art

[0002] Photoacoustic Imaging (PAI) belongs to non-invasive biomedical imaging technology. It combines the high contrast of optical imaging and the high resolution of ultrasonic imaging, and reconstructs the optical absorption distribution image of biological tissues by detecting light-induced ultrasonic signals. Its basic principle is: when a pulsed laser irradiates biological tissues, the molecules in the tissues absorb light energy and convert it into heat energy, resulting in a local temperature increase and thermal expansion, thereby generating ultrasonic waves. After these ultrasonic waves are received by an ultrasonic detector and processed by an image reconstruction algorithm, an optical absorption distribution image of the tissue is finally generated. Photoacoustic imaging technology can provide information about tissue structure, function, and metabolism under non-invasive or minimally invasive conditions, and shows great application potential especially in the fields of vascular imaging, tumor detection, and neuroimaging.

[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 being easily affected by skull acoustic interference. In addition, existing scanning methods are prone to motion artifacts in deep tissue imaging and are difficult to achieve dynamic real-time monitoring. Summary of the Invention

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

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

[0006] 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;

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

[0008] Generate an equidistant elliptical trajectory drive signal according to the dynamic elliptical scanning trajectory to control the equidistant elliptical trajectory laser scanning system for scanning, and obtain the three-dimensional photoacoustic brain imaging result.

[0009] Further, the step 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 includes:

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

[0011] Based on the equidistant elliptical trajectory laser scanning system, set the optical path distance of the equidistant elliptical trajectory laser scanning system, and the optical path distance represents the vertical distance between the scanning center point of the X-Y 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, establish the mapping relationship between the scanning angle and the plane coordinates;

[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, determine that the amplitude of the scanning angle meets the conditions, and determine the scanning range of the equidistant elliptical trajectory laser scanning system.

[0014] Further, the equidistant elliptical trajectory laser scanning system specifically includes 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:

[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 drive signal;

[0017] The transducer is used to receive photoacoustic signals;

[0018] The signal acquisition module is used to synchronize the laser pulse and the 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 elliptical parameters and generate the equidistant elliptical trajectory drive signal;

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

[0022] Further, 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 used to initialize the isometric ellipse parameters according to the scanning range of the isometric ellipse trajectory laser scanning system;

[0024] The trajectory generation module is used to generate an isometric ellipse trajectory drive signal based on the initialized isometric ellipse parameters;

[0025] The signal processing module is used to process the feedback signal from the MEMS galvanometer and adjust the drive signal.

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

[0027] According to the scanning range of the isometric ellipse trajectory laser scanning system, obtain the isometric ellipse parameters, and the isometric ellipse parameters include the ellipse basic amplitude, the linear offset speed coefficient, and the angular frequency;

[0028] According to the isometric ellipse parameters, determine the dynamic ellipse scanning trajectory of the isometric ellipse trajectory laser scanning system.

[0029] Further, the step of generating an isometric ellipse trajectory drive signal according to the dynamic ellipse scanning trajectory to control the isometric ellipse trajectory laser scanning system to perform scanning and obtain a three-dimensional photoacoustic brain imaging result specifically includes:

[0030] Based on the dynamic ellipse scanning trajectory, generate an isometric ellipse trajectory drive signal in combination with the deflection control mode of the MEMS galvanometer. The deflection control mode of the MEMS galvanometer is to switch the deflection direction according to the parity of the scanning frame number;

[0031] Convert the isometric ellipse trajectory drive signal into an analog voltage signal and synchronize the signal with the photoacoustic signal to obtain a synchronized isometric ellipse trajectory drive signal;

[0032] Determine the coverage condition of the isometric ellipse trajectory laser scanning range by constraining the linear offset speed and the single-frame time;

[0033] Based on the isometric ellipse trajectory laser scanning range coverage condition and the synchronized isometric ellipse trajectory drive signal, control the isometric ellipse trajectory laser scanning system to perform scanning, reconstruct the light absorption distribution image, and obtain a three-dimensional photoacoustic brain imaging result.

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

[0035]

[0036] In the above formula, x(t) and y(t) should represent the functions of the position of the scanning device on the X-axis and Y-axis changing with time t, Ax represents the semi-major axis of the X-axis in the elliptical base amplitude, By t represents the semi-minor axis of the Y-axis in the elliptical base amplitude, By2 represents the linear offset velocity coefficient, ω represents the angular frequency, and N represents the direction control number.

[0037] Furthermore, the coverage condition of the equidistant elliptical trajectory laser scanning range includes a rectangular scanning area and a circular scanning area, where:

[0038] When the coverage condition of the equidistant elliptical trajectory laser scanning range is a rectangular scanning area, dynamically adjust the elliptical rotation angle so that its major axis direction aligns with the long side of the rectangle;

[0039] When the coverage condition of the equidistant elliptical trajectory laser scanning range is a circular scanning area, it degenerates into a standard circular trajectory.

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

[0041]

[0042] 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 volume data, N represents the direction control number, and t represents the time.

[0043] The second technical solution adopted by the present invention is: An optoacoustic brain imaging system based on equidistant elliptical trajectory scanning, including:

[0044] The first module is used 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 used to obtain equidistant elliptical parameters according to the scanning range of the equidistant elliptical trajectory laser scanning system, and determine the dynamic elliptical scanning trajectory of the equidistant elliptical trajectory laser scanning system;

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

[0047] The beneficial effects of the method and system of the present invention are as follows: By constructing an equidistant elliptical trajectory laser scanning system, setting the optical path distance of the equidistant elliptical trajectory laser scanning system, determining the scanning range of the equidistant elliptical trajectory laser scanning system, further obtaining equidistant elliptical parameters according to the scanning range of the equidistant elliptical trajectory laser scanning system, determining the dynamic elliptical scanning trajectory of the equidistant elliptical trajectory laser scanning system, and realizing the continuity during the scanning process by designing the equidistant elliptical scanning trajectory, the three-dimensional adaptability is enhanced, and the system structure is simplified. Finally, 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, which can reduce the edge distortion of the image while controlling the galvanometer to perform fast and large-angle scanning, significantly improve the resolution of brain imaging, and extend the service life of the galvanometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a flowchart of the steps of a photoacoustic brain imaging method based on equidistant elliptical trajectory scanning according to the present invention;

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

[0050] Figure 3 is a schematic diagram of the steps of equidistant elliptical trajectory scanning provided by a specific embodiment of the present invention;

[0051] Figure 4 is a schematic structural diagram of an equidistant elliptical trajectory laser scanning system provided by a specific embodiment of the present invention;

[0052] Figure 5 is a schematic plan view of the scanning result provided by a specific embodiment of the present invention;

[0053] Figure 6 is a schematic diagram of the driving waveform of the scanning trajectory provided by a specific embodiment of the present invention;

[0054] Figure 7 is a schematic diagram of the scanning trajectory provided by a specific embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0055] The following further describes the present invention in detail with reference to the drawings and specific embodiments. For the step numbers in the following embodiments, they are only set for the convenience of explanation and illustration, and no limitation is imposed on the order between the steps. 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 should be noted that the traditional laser scanning method has the following deficiencies:

[0057] 1) The scanning efficiency is low. The return time of raster scanning accounts for more than 30%, significantly shortening the effective scanning time. This results in a slow imaging speed and makes it difficult to meet the requirements of real-time dynamic monitoring.

[0058] 2) The trajectory coverage rate is insufficient. Fixed elliptical or spiral trajectories cannot adapt to complex-shaped scanning areas, making it difficult to achieve uniform coverage of the target area. This non-uniformity leads to a decrease in imaging resolution and contrast, limiting the application of photoacoustic imaging in complex tissue structures.

[0059] 3) The mechanical loss is large. The sudden change in acceleration shortens the lifespan of the galvanometer, increasing the maintenance cost and usage limitations of the device.

[0060] Therefore, although the scanning method of the double helix structure can, to a certain extent, extend the service life of the scanning device and improve scanning stability through its continuous and mutation-free trajectory design, during the photoacoustic imaging process, due to the gap in the scanning interval between the inner and outer circles of the helix, the energy distribution of the scanning points on the inner and outer circles is uneven. This energy difference is likely to cause thermal damage to the tissue in the central scanning area, further limiting its application in biomedical imaging.

[0061] Based on this, the embodiments of the present invention meet the comprehensive requirements of the laser scanning imaging field for large range, high speed, and high precision. By designing an equidistant elliptical scanning trajectory, the continuity during the scanning process is achieved, thereby enhancing the three-dimensional adaptability and simplifying the system structure. In addition, the present invention also improves the smoothness of the scanning trajectory, ensuring the continuity of the mirror rotation movement 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 thus improving the scanning speed. The continuous and mutation-free scanning method not only helps to extend the service life of the scanning device but also significantly improves the scanning stability. These characteristics make the system have important application potential in the field of biomedical imaging, especially in photoacoustic imaging technology, which combines the high contrast of optical imaging and the deep penetration of ultrasonic imaging, can reflect the distribution of endogenous absorption substances in the living body without labeling and non-invasively, and is suitable for imaging the whole brain of rodent models.

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

[0063] S100. 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;

[0064] S110. Construct an equidistant elliptical trajectory laser scanning system;

[0065] In this embodiment, asFigure 4 and Figure 5 as shown in, where Figure 4 The solid line in represents the control flow, the dashed line between the laser emitter, galvanometer and the scanning area represents the optical signal transmission, and the dotted line between the scanning area, ultrasonic transducer and the signal acquisition module represents the acousto-optic signal transmission. 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. Among them, several said laser emitters are used to emit laser beams; the MEMS galvanometer is used to control the deflection of the laser beam according to the equidistant elliptical trajectory drive 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 drive signals into analog voltage signals; the control system is used to initialize equidistant elliptical parameters and generate equidistant elliptical trajectory drive signals; the user interface module is used to receive user input and display three-dimensional photoacoustic brain imaging results.

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

[0067] S120. Based on the equidistant elliptical trajectory laser scanning system, set 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 X-Y two-dimensional laser scanning device and the plane to be scanned;

[0068] S130. According to the optical path distance of the equidistant elliptical trajectory laser scanning system, establish the mapping relationship between the scanning angle and the plane coordinates;

[0069] S140. Combine the mapping relationship between the scanning angle and the plane coordinates and the optical path distance of the equidistant elliptical trajectory laser scanning system to determine that the scanning angle amplitude meets the conditions and determine the scanning range of the equidistant elliptical trajectory laser scanning system.

[0070] In this embodiment, as Figure 3 shown, set the optical path distance D of the scanning system, that is, the vertical distance between the scanning center point of the X-Y two-dimensional laser scanning device and the plane to be scanned, and establish the mapping relationship between the scanning angle and the plane coordinates. Its expression is specifically 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 respectively represent the scanning angles of the two-dimensional laser scanning device on the X-axis and Y-axis, and X max and Y max respectively represent the maximum dimensions of the scanning area in the X-axis and Y-axis directions.

[0075] S200. Obtain the equidistant ellipse parameters according to the scanning range of the equidistant ellipse trajectory laser scanning system, and determine the dynamic ellipse scanning trajectory of the equidistant ellipse trajectory laser scanning system;

[0076] S210. Obtain the equidistant ellipse parameters according to the scanning range of the equidistant ellipse trajectory laser scanning system, and the equidistant ellipse parameters include the ellipse basic amplitude, the linear offset velocity coefficient and the angular frequency;

[0077] S220. Determine the dynamic ellipse scanning trajectory of the equidistant ellipse trajectory laser scanning system according to the equidistant ellipse parameters.

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

[0079] 1) The ellipse basic amplitude A x (semi-major axis of the X-axis) and B yt (semi-minor axis of the Y-axis), and 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) The linear offset velocity coefficient B y2 (unit: mm / s), and its expression is:

[0084]

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

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

[0087]

[0088] In the above formula, n represents the number of complete cycles of the elliptical trajectory within a single frame.

[0089] 3) Angular frequency, whose expression is:

[0090] ω = 2πf

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

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

[0093] S310. Generate an equidistant elliptical trajectory driving signal based on the dynamic elliptical scanning trajectory and in combination with the deflection control mode of the MEMS galvanometer. The deflection control mode of the MEMS galvanometer is to switch the deflection direction according to the parity of the scanning frame number;

[0094] In this embodiment, based on the above-set parameters, determine the scanning trajectory; generate a corresponding equidistant elliptical driving signal according to the control mode of the used galvanometer to control the deflection of the MEMS galvanometer, thereby realizing the control of the laser scanning trajectory. Among them, 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 the functions of the positions of the scanning device on the X-axis and Y-axis changing with time t, A x represents the semi-major axis of the X-axis in the elliptical basic amplitude, B yt represents the semi-minor axis of the Y-axis in the elliptical basic amplitude, B y2 represents the linear offset velocity coefficient, ω represents the angular frequency, and N represents the direction control number.

[0097] Furthermore, it should be noted that N ∈ {+1, -1} is the direction control number, which is switched according to the parity of the scanning frame number. When the scanning frame number is odd, set N = +t, and when the scanning frame number is even, set N = -t.

[0098] S320. Convert the equidistant elliptical trajectory driving signal into an analog voltage signal and synchronize the signal in combination with the photoacoustic signal to obtain the synchronized equidistant elliptical trajectory driving signal;

[0099] In this embodiment, the drive signal is converted into an analog voltage by a high-precision DAC module to control the galvanometer mirror to deflect along an equidistant elliptical trajectory, and at the same time, the photoacoustic signal is synchronously received by the transducer. During the synchronous acquisition of the signal, the emission of the laser pulse and the reception of the ultrasonic signal are hard-synchronized through time delay integration (TDI) to ensure that the time resolution of the photoacoustic signal corresponds precisely to the scanning position.

[0100] S330. Determine the coverage condition of the equidistant elliptical trajectory laser scanning range by constraining the linear offset speed and the single-frame time; in this embodiment, first, the scanning process needs to meet the following coverage conditions:

[0101] |B y2 ·T| ≤ 2R yt

[0102] Furthermore, by constraining the linear offset speed and the single-frame time, ensure that the elliptical trajectories of adjacent scanning frames are completely covered along the Y-axis to eliminate the scanning blind area. When the scanning area is rectangular, dynamically adjust the elliptical rotation angle φ(t) so that its major axis direction is aligned with the long side of the rectangle. When the scanning area is circular, as Figure 7 shown, it degenerates into a standard circular trajectory: A x = R yt ,B y2 = 0.

[0103] S340. Based on the coverage condition of the equidistant elliptical trajectory laser scanning range and combined with the synchronized equidistant elliptical trajectory drive signal, control the equidistant elliptical trajectory laser scanning system to perform scanning, reconstruct the light absorption distribution image, and obtain the three-dimensional photoacoustic brain imaging result.

[0104] In this embodiment, after the collected ultrasonic signal is filtered and amplified, the time reversal algorithm or the delay and sum algorithm is used to reconstruct the light absorption distribution image, and the three-dimensional volume data is generated through the following formula, and its 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 volume data, N represents the direction control number, and t represents the time.

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

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

[0109] The first module 201 is used 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;

[0110] The second module 202 is used to obtain equidistant elliptical parameters according to the scanning range of the equidistant elliptical trajectory laser scanning system, and determine the dynamic elliptical scanning trajectory of the equidistant elliptical trajectory laser scanning system;

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

[0112] The content in the above method embodiments is applicable to the system embodiments of the present invention. The functions specifically implemented in the system embodiments of the present invention are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0113] The above is a specific description of the preferred embodiments of the present invention. However, the present invention is not limited to the described embodiments. Those skilled in the art can make various equivalent deformations or substitutions without departing from the spirit of the present invention. These equivalent deformations or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A photoacoustic brain imaging method based on equidistant elliptical trajectory scanning, characterized in that: The following steps are involved: 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; According to the scanning range of the equidistant ellipse trajectory laser scanning system, the equidistant ellipse parameters are obtained, and the dynamic ellipse scanning trajectory of the equidistant ellipse trajectory laser scanning system is determined; 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 scan and obtain three-dimensional photoacoustic brain imaging results.

2. According to claim 1, a photoacoustic brain imaging method based on equidistant elliptical trajectory scanning is characterized in that: The step of constructing an equidistant elliptical trajectory laser scanning system, setting an optical path distance of the equidistant elliptical trajectory laser scanning system, and determining a scanning range of the equidistant elliptical trajectory laser scanning system specifically includes: Construct an equidistant elliptical trajectory laser scanning system; Based on the equidistant elliptical trajectory laser scanning system, an optical path distance of the equidistant elliptical trajectory laser scanning system is set, wherein the optical path distance represents a vertical distance between a scanning center point of an XY two-dimensional laser scanning device and a plane to be scanned; 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; 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.

3. According to claim 2, a photoacoustic brain imaging method based on equidistant elliptical trajectory scanning is characterized in that: The equidistant elliptical trajectory laser scanning system specifically includes several laser transmitters, MEMS galvanometers, transducers, signal acquisition modules, DAC modules, control systems and user interface modules, wherein: The plurality of laser emitters are used to emit laser beams; The MEMS galvanometer is used to control the deflection of the laser beam according to the equidistant elliptical trajectory driving signal; The transducer is used to receive the photoacoustic signal; The signal acquisition module is used for synchronous laser pulse and ultrasonic signal sampling; The DAC module is used to convert the digital drive signal into an analog voltage signal; The control system is used to initialize the equidistant ellipse parameters and generate an equidistant ellipse trajectory driving signal; The user interface module is used to receive user input and display three-dimensional photoacoustic brain imaging results.

4. The photoacoustic brain imaging method based on equidistant elliptical trajectory scanning according to claim 3, characterized in 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.

5. The photoacoustic brain imaging method based on equidistant elliptical trajectory scanning according to claim 4, characterized in that: The step of obtaining equidistant ellipse parameters according to the scanning range of the equidistant ellipse trajectory laser scanning system and determining the dynamic ellipse scanning trajectory of the equidistant ellipse trajectory laser scanning system specifically includes: According to the scanning range of the equidistant ellipse trajectory laser scanning system, the equidistant ellipse parameters are obtained, wherein the equidistant ellipse parameters include the ellipse basic amplitude, the linear offset velocity coefficient and the angular frequency; According to the equidistant ellipse parameters, the dynamic ellipse scanning trajectory of the equidistant ellipse trajectory laser scanning system is determined.

6. The photoacoustic brain imaging method based on equidistant elliptical trajectory scanning according to claim 5, characterized in that: The step of 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 obtain the three-dimensional photoacoustic brain imaging result specifically includes: Based on the dynamic elliptical scanning trajectory, an equidistant elliptical trajectory driving signal is generated in combination with a deflection control method of a MEMS galvanometer, wherein the deflection control method of the MEMS galvanometer is to switch the deflection direction according to the parity of the scanning frame sequence number; The equidistant ellipse trajectory driving signal is converted into an analog voltage signal and combined with the photoacoustic signal for signal synchronization to obtain a synchronized equidistant ellipse trajectory driving signal; By constraining the linear offset speed and single frame time, the coverage condition of the laser scanning range of the equidistant elliptical trajectory is determined; Based on the coverage condition of the equidistant elliptical trajectory laser scanning range and the synchronized equidistant elliptical trajectory driving signal, the equidistant elliptical trajectory laser scanning system is controlled to scan, reconstruct the light absorption distribution image, and obtain the three-dimensional photoacoustic brain imaging results.

7. The photoacoustic brain imaging method based on equidistant elliptical trajectory scanning according to claim 6, characterized in that: The expression of the equidistant elliptical trajectory driving signal is specifically as follows: In the above formula, x(t) and y(t) should represent the function of the position of the scanning device on the X-axis and Y-axis changing with time y, A x Indicates the X-axis semi-major axis in the ellipse base amplitude, B yt Indicates the Y-axis semi-minor axis in the ellipse base amplitude, B y2 represents the linear offset velocity coefficient, ω represents the angular frequency, and N represents the direction control number.

8. The photoacoustic brain imaging method based on equidistant elliptical trajectory scanning according to claim 7, characterized in that: The equidistant elliptical trajectory laser scanning range coverage condition includes a rectangular scanning area and a circular scanning area, wherein: When the equidistant elliptical trajectory laser scanning range covers a rectangular scanning area, the ellipse rotation angle is dynamically adjusted so that its long axis direction is aligned with the long side of the rectangle; When the laser scanning range of the equidistant elliptical trajectory covers a circular scanning area, it degenerates into a standard circular trajectory.

9. The photoacoustic brain imaging method based on equidistant elliptical trajectory scanning according to claim 8, characterized in that: The expression for reconstructing the light absorption distribution image is specifically as follows: In the above formula, p(x, y, t) represents the time domain sound pressure signal, v represents the sound velocity, τ represents the time delay, z represents the imaging depth, I(x, y, z) represents the three-dimensional volume data, N represents the direction control number, and t represents time.

10. A photoacoustic brain imaging system based on equidistant elliptical trajectory scanning, characterized in that: Includes the following modules: The first module is used 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; The second module is used to obtain equidistant ellipse parameters according to the scanning range of the equidistant ellipse trajectory laser scanning system, and determine the dynamic ellipse scanning trajectory of the equidistant ellipse trajectory laser scanning system; The third module is used to generate 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 obtain three-dimensional photoacoustic brain imaging results.

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