A method for FLASH radiotherapy three-dimensional scanning water tank device based on radiation-induced sound technology

Abstract

The application discloses a FLASH radiotherapy three-dimensional scanning water tank device method based on radiation-induced sound technology, and belongs to the technical field of FLASH radiotherapy time high-dose rate beam parameter verification, and comprises the following steps: collecting a sound signal excited by a water tank irradiated by a beam, and then acquiring a multi-channel time-varying sound signal; amplifying and filtering the sound signal; estimating the original sound signal based on the filtered sound signal; performing signal inversion on the original sound signal to reconstruct a dose distribution at a desired depth in the water tank, and then obtaining a Profile curve and a PDD curve of the beam in the water tank. The application can greatly shorten the three-dimensional water tank Profile curve measurement time under the FLASH radiotherapy condition, and can improve the curve measurement error caused by the influence of multiple factors such as the dose rate measurement range of the nuclear radiation probe and the ultra-high dose rate radiotherapy.

Description

Technical Field

[0001] This invention belongs to the technical field of verifying ultra-high dose rate X-ray beam parameters during FLASH radiotherapy, specifically relating to a method for a FLASH radiotherapy three-dimensional scanning water tank device based on radiation-induced acoustic technology. Background Technology

[0002] FLASH radiotherapy (FLASH-RT), also known as ultra-high dose rate radiotherapy, is an emerging radiotherapy technique. Currently, X-rays, proton beams, heavy ion beams, and electron beams have been researched and applied to FLASH radiotherapy. It typically uses ultra-high dose rates of radiation to irradiate the tumor site within a very short time, significantly reducing damage to normal tissues while ensuring the effectiveness of the radiotherapy. Before cancer patients receive FLASH radiotherapy, a three-dimensional scanning tank device is usually used to measure the depth-percentage dose (PDD) curve of the radiation within the tank and the dose distribution curve (profile) along the central axis of the irradiation field to ensure that FLASH radiotherapy achieves the desired effect.

[0003] However, existing 3D scanning tanks typically rely on nuclear radiation probes to detect the dose deposited by the radiation beam within the tank to determine PDD and profile curves. Since FLASH radiotherapy uses ultra-high dose rates of high-energy radiation, nuclear radiation probes face dose saturation during detection, and measurement errors significantly deviate from the true values, thus failing to meet the clinical application requirements of FLASH radiotherapy. Furthermore, existing 3D scanning tanks require continuous probe movement to collect radiation dose at different locations within the tank, resulting in significant time consumption. Radiotherapy profile determination typically takes anywhere from ten minutes to half an hour (using the Blue Phantom 3D scanning tank as an example), making rapid profile and two-dimensional dose distribution determination impossible.

[0004] Therefore, we can see that existing technologies face the following major challenges: 1. Existing technologies typically involve installing a nuclear radiation probe in a 3D scanning tank and performing linear scanning by moving the probe to determine the PDD and Profile curves. However, during FLASH radiotherapy, the accuracy of probe measurements decreases significantly due to dose saturation effects, leading to a risk of serious distortion in the measurement results. Furthermore, the need for linear scanning results in lengthy measurement times when determining Profile curves, greatly increasing the radiation protection safety risks within the irradiation room.

[0005] 2. Due to the limitation of measurement points per probe, it is usually necessary to control the stepper motor to perform linear scanning within the irradiation field area at a certain step size to achieve two-dimensional dose distribution measurement in the water tank. Therefore, existing technologies face great difficulties in conducting three-dimensional scanning of the X-ray beam dose distribution in the water tank for FLASH radiotherapy, making it difficult to complete the dose distribution measurement task within the expected time. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned shortcomings in the prior art by providing a method for a FLASH radiotherapy three-dimensional scanning water tank device based on radiation-induced acoustic technology, thereby solving the problem of limitations in the determination of PDD curves and Profile curves of three-dimensional scanning water tanks under FLASH radiotherapy conditions using existing methods.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for a FLASH radiotherapy three-dimensional scanning water tank device based on radiation-induced acoustic technology includes the following steps: S1. Acoustic signals excited by the X-ray beam irradiating the water tank are collected based on the array transducer; S2. Amplify and filter the acoustic signal to obtain the filtered acoustic signal; S3. Estimate the original acoustic signal based on the filtered acoustic signal; S4. Perform signal inversion on the original acoustic signal to reconstruct the dose distribution at the desired depth in the water tank, thereby obtaining the profile curve of the X-ray beam in the water tank. S5. Based on the reconstructed dose distribution at the desired depth in the water tank, control the array transducer to perform a linear scan in the vertical height plane of the water tank to obtain the PDD curve of the X-ray beam in the water tank.

[0008] Furthermore, S1 specifically includes: When an ultra-high dose rate pulsed X-ray beam irradiates the medium in a water tank, a multi-physics field conversion occurs, and the dose deposited in the medium by the ultra-high dose rate pulsed X-ray beam is ultimately converted into a sound pressure signal. The control array transducer performs a circular scan in three-dimensional water to collect sound pressure signals, thereby obtaining multi-channel time-varying sound signals at different angle positions.

[0009] Furthermore, in S1, the converted sound pressure signal is represented as: In the formula, Indicates the position of the medium The sound pressure at that location; Represents the Grüneisen coefficient. Represents the volumetric thermal diffusivity. Indicates the isothermal compressibility coefficient. The density parameter representing the irradiated medium. Indicates specific heat capacity; This indicates the percentage of the deposited dose converted into heat energy; Indicates the position of the medium The dose of the deposited substance.

[0010] Furthermore, in S1, the multi-channel time-varying acoustic signals obtained by the array transducer at different angular positions are represented as follows: In the formula, Indicates in Time array transducer at position The sound signal recorded at the location; Speed ​​of sound; Indicates position The initial sound pressure at the location; This represents the Dirac function.

[0011] Furthermore, S2 specifically includes: amplifying the acoustic signal in S1 to obtain an amplified acoustic signal; then, performing adaptive filtering and bandpass filtering on the amplified acoustic signal in sequence to finally obtain a filtered acoustic signal.

[0012] Furthermore, adaptive filtering is applied to the amplified acoustic signal, which is expressed as follows: In the formula, This represents the acoustic signal after adaptive filtering. This represents the amplified sound signal; This indicates the coefficients updated by the adaptive filter algorithm; Indicates noise interference signal; Bandpass filtering is used for the adaptively filtered acoustic signal Denoising is performed, which is represented as: In the formula, This represents the filtered acoustic signal; This represents the impulse response of the bandpass filter.

[0013] Furthermore, S3 specifically includes: The filtered acoustic signal is deconvolved using a Wiener filter to provide an optimal estimate in the frequency domain with minimum mean square error. The distribution of the original acoustic signal is then obtained by inverse solving, and is expressed as follows: In the formula, This represents the optimal estimate of the original acoustic signal; This represents the inverse transformation from power spectral density to a time-domain signal; The power spectral density of the original acoustic signal is estimated to be the optimal estimate provided by the Wiener filter in the frequency domain in the sense of minimum mean square error.

[0014] Furthermore, step S4 specifically includes the following sub-steps: S41. Optimal estimation of the original acoustic signal using the channel impulse response from the target region to each array element. The transmitted waveform is constructed through time-domain inversion and is represented as follows: In the formula, This indicates a time-domain reversal operation; This represents the signal acquired by the j-th element of the array transducer; This represents the time-reversed signal; J represents the j-th element of the array transducer; S42. After the transmitted waveform is retransmitted, it propagates through the medium and achieves adaptive focusing at the original observation point. The output signal is obtained by convolving and superimposing the echoes of each array unit with the time-reversal weighting coefficients, which is expressed as: In the formula, Indicates the location Place, Sound pressure at any given moment; The number of elements in the array transducer. The first array transducer represents the array transducer. One element, For the first The weighting factor corresponding to the signal channel of each element; S43. The initial sound pressure distribution is calculated using positive constraint conditions, and it is expressed as follows: In the formula, Indicates the initial sound pressure level for reconstruction; S44. Substitute the reconstructed initial sound pressure into the expression of the converted sound pressure signal in S1 to quantitatively calculate the dose distribution delivered by the X-ray beam in the water tank. By extracting the dose value of the central axis of the dose distribution, plot the profile curve of the X-ray beam in the water tank.

[0015] Furthermore, S5 specifically includes: Based on the quantitatively calculated dose distribution of the X-ray beam delivered in the water tank, the array transducer is controlled to perform a linear scan in the vertical plane of the water tank. The array transducer records the signal amplitude at different heights and extracts the signal amplitude values ​​at different heights. The amplitude values ​​are then normalized, and the PDD curve of the X-ray beam in the water tank is plotted.

[0016] The method for a FLASH radiotherapy three-dimensional scanning water tank device based on radiation-induced acoustic technology provided by this invention has the following beneficial effects: 1. This invention achieves high-precision PDD curve and profile curve determination using acoustic signals recorded by an array transducer, and can also determine the two-dimensional dose distribution of the radiation beam in a water tank. Compared to traditional three-dimensional scanning water tank measurement methods, this invention can significantly shorten the three-dimensional water tank profile curve determination time under FLASH radiotherapy conditions, while improving the curve measurement errors caused by multiple factors such as the dose rate measurement range of the nuclear radiation probe and ultra-high dose rate radiotherapy.

[0017] 2. This invention enables the reconstruction of semi-quantitative or quantitative dose distribution of ultra-high dose rate X-ray beams under FLASH radiotherapy conditions. Existing methods are affected by the ultra-high dose rate irradiation and extremely short delivery time characteristics of FLASH radiotherapy, facing problems such as dose saturation effect and significant deviation of measured values ​​from actual values. The method designed in this invention detects the acoustic signal induced by ultra-high dose rate X-ray beam irradiation in the water tank, reconstructs the acoustic signal after signal processing of the acoustic signal recorded by the array transducer, and reconstructs the dose distribution in the water tank by inverting the sound pressure distribution. This allows for the determination of semi-quantitative or quantitative dose distribution of the X-ray beam in the water tank, completing the dose verification and evaluation work before clinical irradiation.

[0018] 3. This invention is applicable to the determination of PDD and Profile curves in a three-dimensional scanning water tank under FLASH radiotherapy conditions. Existing three-dimensional scanning water tanks are generally suitable for conventional radiotherapy conditions, but in FLASH radiotherapy, the dose rate measurement deviation of the water tank is relatively large, making it difficult to achieve accurate PDD and Profile curve determination. The three-dimensional scanning water tank dose measurement method proposed in this invention, which uses radiation-induced acoustic technology, can efficiently and accurately determine the PDD and Profile curves of ultra-high dose rate pulsed X-ray beams in the water tank due to the use of multi-array transducers and acoustic reconstruction algorithms.

[0019] 4. The method proposed in this invention can significantly shorten the dose measurement time of a three-dimensional scanning water tank and reduce design costs. Because this invention uses a multi-array transducer to collect the acoustic signal induced by the X-ray beam in the water tank, it can significantly shorten the measurement time compared to the linear scanning of a traditional single nuclear radiation probe. Existing methods require at least dozens or hundreds of dose measurements to achieve profile curve determination, resulting in long waiting times for operators and clinicians. This invention, using a multi-array transducer to control the measurement, can collect the required multi-channel acoustic signal data after several operations, thereby reconstructing the dose distribution at the desired depth in the water tank and obtaining the corresponding profile curve, thus significantly shortening the measurement time. Simultaneously, because it uses an acoustic transducer instead of a high-precision radiation probe to collect data, manufacturing costs can be significantly reduced. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of data acquisition for the FLASH radiotherapy three-dimensional scanning water tank array transducer in an embodiment of the present invention.

[0021] Figure 2 This is a flowchart of a method for a FLASH radiotherapy three-dimensional scanning water tank device based on radiation acoustic technology, according to an embodiment of the present invention. Detailed Implementation

[0022] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0023] Before cancer patients receive FLASH radiotherapy, a three-dimensional scanning tank device is needed to accurately measure the depth percentage dose curve (PDD) of the radiation beam in the tank and the dose distribution curve (profile) of the central axis of the irradiation field. This is to evaluate the performance and compare the consistency of the radiation beam and the irradiation field, so as to ensure that FLASH radiotherapy can achieve the expected results.

[0024] Based on this, this embodiment provides a method for a FLASH radiotherapy three-dimensional scanning water tank device based on radiation-induced acoustic technology. The method involves signal processing of the acoustic signals collected by the transducer from a multi-channel data acquisition system, and reconstructing the original acoustic signals by combining the frequency response curves of the transducer and amplifier. A linear scan is performed in the vertical direction of the three-dimensional scanning water tank with a fixed step size, and the PDD curve is accurately calculated using acoustic signals measured at different depths. The dose distribution in the water tank is quantitatively reconstructed using multi-channel acoustic signal data collected by the array transducer, and the profile curves at different depths are calculated from the reconstructed dose distribution. This reduces the measurement time of the three-dimensional water tank and improves the accuracy of profile curve determination in FLASH radiotherapy water tanks. This embodiment is the first to attempt to reconstruct the dose distribution in the irradiation field and surrounding area by acquiring acoustic signals excited by a pulsed X-ray beam, thus solving the problem of limitations in the determination of PDD and profile curves of three-dimensional scanning water tanks under FLASH radiotherapy conditions using existing methods. (Reference...) Figure 2 Specifically, it includes the following: S1. Acoustic signals excited by the X-ray beam irradiating the water tank are collected based on the array transducer, and then multi-channel time-varying acoustic signals are obtained. For details, please refer to Figure 1 When an ultra-high dose rate pulsed X-ray beam irradiates the medium in a water tank, a multi-physics transformation occurs. The dose deposited in the medium by the ultra-high dose rate pulsed X-ray beam undergoes a series of transformations and is ultimately converted into a sound pressure signal, which is represented as follows: In the formula, Indicates the position of the medium The sound pressure at that location; Represents the Grüneisen coefficient. Represents the volumetric thermal diffusivity. Indicates the isothermal compressibility coefficient. The density parameter representing the irradiated medium. Indicates specific heat capacity; This indicates the percentage of the deposited dose converted into heat energy; Indicates the position of the medium The dose of the deposited substance.

[0025] Based on this, the acoustic signal obtained by the array transducer is represented as: In the formula, Indicates in Time array transducer at position The sound signal recorded at the location; Speed ​​of sound; Indicates position The initial sound pressure at the location; This represents the Dirac function.

[0026] This embodiment utilizes a ring array transducer deployed outside the radiation field to acquire ionizing radiation acoustic signal (acoustic signal) data across the entire field of view. By controlling the array transducer to perform a ring scan using a controller, multi-channel acoustic signal data acquired by the array transducer at different angle positions can be obtained, providing sufficient data support for subsequent dose distribution reconstruction.

[0027] S2. Amplify and filter the acoustic signal to obtain the filtered acoustic signal; In this embodiment, a preamplifier is used to amplify the acoustic signals collected by the array transducer. Simultaneously, since the collected signals include background noise from the radiotherapy room and sensor noise, filtering and noise reduction processing is required. Specifically, the acoustic signal in S1 is amplified. Let the time-varying acoustic signal recorded by the array transducer be... It consists of the original sound signal and noise signals (including background noise and sensor noise). Composition, namely: Since the signal acquired by the array transducer is relatively weak, it needs to be amplified. The amplification gain to reach the desired signal is set to... Then the amplified sound signal will be output. It can be represented as follows: Since the signal contains noise, the amplified acoustic signal needs to be filtered and denoised. An adaptive filter is used for denoising. The adaptive filter employs an FIR structure, and the algorithm updates the coefficients accordingly. , The signal is a noise interference signal. The adaptively filtered signal can then be expressed as follows: In the formula, This indicates the coefficients updated by the adaptive filter algorithm; This represents the acoustic signal after adaptive filtering. Since the frequency domain of the acoustic signal is distributed within a certain range, bandpass filtering is used to further denoise the adaptively filtered acoustic signal, resulting in the final output filtered signal. It is represented as follows: In the formula, This represents the filtered acoustic signal; This represents the impulse response of the bandpass filter.

[0028] S3. Estimate the original acoustic signal based on the filtered acoustic signal; The original acoustic signal distribution is obtained by inverse kinematics of the system's frequency response using Wiener filtering. To perform high-precision 3D scanning of the water tank's PDD and Profile curves, the original ionizing radiation acoustic signal needs to be recovered from the acquired ionizing radiation acoustic signal. Therefore, a Wiener filter is used for deconvolution of the signal to provide an optimal estimate in the frequency domain with minimum mean square error. The optimal estimate of the original time-domain signal can be expressed as follows: In the formula, This represents the optimal estimate of the original acoustic signal; This represents the inverse transformation from power spectral density to a time-domain signal; The power spectral density of the original acoustic signal is estimated to be the optimal estimate provided by the Wiener filter in the frequency domain in the sense of minimum mean square error.

[0029] By implementing this step, the original acoustic signal can be recovered, enabling subsequent quantitative dose distribution reconstruction.

[0030] S4. Perform signal inversion on the original acoustic signal to reconstruct the dose distribution at the desired depth in the water tank, thereby obtaining the profile curve of the X-ray beam in the water tank. S41. After obtaining the estimated original sound signal, it is necessary to perform optimal estimation of the original sound signal. An inversion operation is performed to reconstruct the original sound pressure and dose distributions. Time-reversal beamforming using an array transducer first utilizes the channel impulse response from the target region to each array element to construct the transmitted waveform through a time-domain inversion operation, and then coherently superimposes the echo signals. The mathematical expression for this time-domain inversion operation can be stated as: In the formula, This indicates a time-domain reversal operation; This represents the signal acquired by the j-th element of the array transducer; This represents the time-reversed signal; J represents the j-th element of the array transducer; S42. After the transmitted waveform is retransmitted, it propagates through the medium and achieves adaptive focusing at the original observation point. The output signal is obtained by convolving and superimposing the echoes of each array unit with the time-reversal weighting coefficients, which is expressed as: In the formula, Indicates the location Place, Sound pressure at any given moment; The number of elements in the array transducer. The first array transducer represents the array transducer. One element, For the first The weighting factor corresponding to the signal channel of each element; S43. The initial sound pressure distribution is calculated using positive constraint conditions, and it is expressed as follows: In the formula, Indicates the initial sound pressure level for reconstruction; S44. Substitute the reconstructed initial sound pressure into the expression for the converted sound pressure signal in S1 to quantitatively calculate the dose delivered by the X-ray beam in the water tank. The dose distribution is analyzed by extracting the dose value along the central axis of the dose distribution and plotting the profile curve of the X-ray beam in the water tank, providing data support for subsequent beam quality analysis and consistency assessment.

[0031] S5. Based on the reconstructed dose distribution at the desired depth in the water tank, control the array transducer to perform a linear scan in the vertical height plane of the water tank to obtain the PDD curve of the X-ray beam in the water tank. Specifically, based on the quantitatively calculated dose distribution of the X-ray beam delivered in the water tank, the controller sends control commands to the stepper motor to control the array transducer to perform linear scanning of the vertical height plane in the water tank. The array transducer records the signal amplitude at different heights and extracts the signal amplitude values ​​at different heights. The amplitude values ​​are then normalized to plot the PDD curve of the X-ray beam in the water tank.

[0032] In summary, this embodiment achieves the determination of PDD curves in a three-dimensional scanning water tank. The PDD curve of the X-ray beam in the water tank is one of the most important indicators in clinical radiotherapy, as it reflects the location of the maximum dose depth of the X-ray beam within the tank. By analyzing the PDD curve, clinicians can also obtain the maximum irradiation depth of the X-ray beam in the water tank and perform beam quality analysis and consistency assessment.

[0033] This embodiment achieves profile curve determination in a three-dimensional scanning water tank. The profile curve visually reflects the symmetry and consistency of the radiation beam field, and is a crucial indicator for evaluating beam quality. Analyzing the water tank's profile curve provides effective data support and quality verification for determining whether subsequent FLASH radiotherapy for patients will achieve the expected results.

[0034] This embodiment achieves the determination of relative and absolute dose distribution within a 3D scanning tank within the desired timeframe. The determination of the delivery dose distribution of the X-ray beam within the tank is also a crucial indicator in clinical radiotherapy. It verifies the consistency of dose distribution between the planned and actual radiation fields, facilitating the evaluation of the efficacy of FLASH radiotherapy for cancer patients. The dose distribution within the tank also reflects the dose distribution within the patient's target area and organs at risk. By significantly shortening the dose distribution determination time while maintaining the accuracy of dose distribution reconstruction, this embodiment enables efficient verification of treatment plans during clinical radiotherapy and provides data support for subsequent in vivo dose verification and efficacy prediction.

[0035] Although specific embodiments of the invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by a person skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this patent.

Claims

1. A method for a FLASH radiotherapy three-dimensional scanning water tank device based on radiation-induced acoustic technology, characterized in that, Includes the following steps: S1. Acoustic signals excited by the X-ray beam irradiating the water tank are collected based on the array transducer; S2. Amplify and filter the acoustic signal to obtain the filtered acoustic signal; S3. Estimate the original acoustic signal based on the filtered acoustic signal; S4. Perform signal inversion on the original acoustic signal to reconstruct the dose distribution at the desired depth in the water tank, thereby obtaining the profile curve of the X-ray beam in the water tank. S5. Based on the reconstructed dose distribution at the desired depth in the water tank, control the array transducer to perform a linear scan in the vertical height plane of the water tank to obtain the PDD curve of the X-ray beam in the water tank.

2. The method of the FLASH radiotherapy three-dimensional scanning water tank device based on radiation-induced acoustic technology according to claim 1, characterized in that, S1 specifically includes: When an ultra-high dose rate pulsed X-ray beam irradiates the medium in a water tank, a multi-physics field conversion occurs, and the dose deposited in the medium by the ultra-high dose rate pulsed X-ray beam is ultimately converted into a sound pressure signal. The control array transducer performs a circular scan in three-dimensional water to collect sound pressure signals, thereby obtaining multi-channel time-varying sound signals at different angle positions.

3. The method of the FLASH radiotherapy three-dimensional scanning water tank device based on radiation-induced acoustic technology according to claim 2, characterized in that, In S1, the converted sound pressure signal is represented as: In the formula, Indicates the position of the medium The sound pressure at that location; Represents the Grüneisen coefficient. Represents the volumetric thermal diffusivity. Indicates the isothermal compressibility coefficient. The density parameter representing the irradiated medium. Indicates specific heat capacity; This indicates the percentage of the deposited dose converted into heat energy; Indicates the position of the medium The dose of the deposited substance.

4. The method of the FLASH radiotherapy three-dimensional scanning water tank device based on radiation-induced acoustic technology according to claim 3, characterized in that, In S1, the multi-channel time-varying acoustic signals obtained by the array transducer at different angular positions are represented as follows: In the formula, Indicates in Time array transducer at position The sound signal recorded at the location; Speed ​​of sound; Indicates position The initial sound pressure at the location; This represents the Dirac function.

5. The method of the FLASH radiotherapy three-dimensional scanning water tank device based on radiation-induced acoustic technology according to claim 1, characterized in that, S2 specifically includes: amplifying the acoustic signal in S1 to obtain an amplified acoustic signal; then, performing adaptive filtering and bandpass filtering on the amplified acoustic signal in sequence to finally obtain a filtered acoustic signal.

6. The method of the FLASH radiotherapy three-dimensional scanning water tank device based on radiation-induced acoustic technology according to claim 5, characterized in that, Adaptive filtering is applied to the amplified acoustic signal, as shown below: In the formula, This represents the acoustic signal after adaptive filtering. This represents the amplified sound signal; This indicates the coefficients updated by the adaptive filter algorithm; Indicates noise interference signal; Bandpass filtering is used for the adaptively filtered acoustic signal Denoising is performed, which is represented as: In the formula, This represents the filtered acoustic signal; This represents the impulse response of the bandpass filter.

7. The method of the FLASH radiotherapy three-dimensional scanning water tank device based on radiation-induced acoustic technology according to claim 1, characterized in that, S3 specifically includes: The filtered acoustic signal is deconvolved using a Wiener filter to provide an optimal estimate in the frequency domain with minimum mean square error. The distribution of the original acoustic signal is then obtained by inverse solving, and is expressed as follows: In the formula, This represents the optimal estimate of the original acoustic signal; This represents the inverse transformation from power spectral density to a time-domain signal; The power spectral density of the original acoustic signal is estimated to be the optimal estimate provided by the Wiener filter in the frequency domain in the sense of minimum mean square error.

8. The method of the FLASH radiotherapy three-dimensional scanning water tank device based on radiation-induced acoustic technology according to claim 1, characterized in that, S4 specifically includes the following steps: S41. Optimal estimation of the original acoustic signal using the channel impulse response from the target region to each array element. The transmitted waveform is constructed through time-domain inversion and is represented as follows: In the formula, This indicates a time-domain reversal operation; This represents the signal acquired by the j-th element of the array transducer; This represents the time-reversed signal; J represents the j-th element of the array transducer; S42. After the transmitted waveform is retransmitted, it propagates through the medium and achieves adaptive focusing at the original observation point. The output signal is obtained by convolving and superimposing the echoes of each array unit with the time-reversal weighting coefficients, which is expressed as: In the formula, Indicates the location Place, Sound pressure at any given moment; The number of elements in the array transducer. The first array transducer represents the array transducer. One element, For the first The weighting factor corresponding to the signal channel of each element; S43. The initial sound pressure distribution is calculated using positive constraint conditions, and it is expressed as follows: In the formula, Indicates the initial sound pressure level for reconstruction; S44. Substitute the reconstructed initial sound pressure into the expression of the converted sound pressure signal in S1 to quantitatively calculate the dose distribution delivered by the X-ray beam in the water tank. By extracting the dose value of the central axis of the dose distribution, plot the profile curve of the X-ray beam in the water tank.

9. The method of the FLASH radiotherapy three-dimensional scanning water tank device based on radiation-induced acoustic technology according to claim 8, characterized in that, S5 specifically includes: Based on the quantitatively calculated dose distribution of the X-ray beam delivered in the water tank, the array transducer is controlled to perform a linear scan in the vertical plane of the water tank. The array transducer records the signal amplitude at different heights and extracts the signal amplitude values ​​at different heights. The amplitude values ​​are then normalized, and the PDD curve of the X-ray beam in the water tank is plotted.

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