Preliminary Exploration Of Sparse Sampling Photoacoustic Technology For Radiotherapy Image Guidance

The use of Image-guided Radiotherapy(IGRT)in radiotherapy can improve the quality of radiotherapy to a certain extent.The existing image-guided technique improves the imaging quality by increasing the dose of X-rays of patients to achieve image response.The need,but increased the harm of radiotherapy to patients.According to the principle of photoacoustic effect,when the radiotherapy generated by the medical linear accelerator irradiates the tissue with X-rays,a weak photoacoustic signal is generated,and the photoacoustic signal contains the absorption distribution information of the X-ray in the illuminated tissue,if effective The sampling method is to sample the photoacoustic signal generated in the target area during radiotherapy to obtain high-quality and effective information,and to perform photoacoustic imaging,which can perform radiotherapy without acquiring X-ray dose and real-time acquisition of X.Based on this principle,this paper proposes a sampling based on sparse sampling technique to realize photoacoustic imaging of radiotherapy pulse X-ray source to solve the problem of dose control hazard in current image guidance.The main research contents of this paper are as follows:1)Through putting up a photodiode detection circuit,the width of X-ray pulses generated by medical linear was detected.The measure result is 4?s;2)According to the width of X-ray pulse,based on the photoacoustic effect,simulations of the photoacoustic signal using X-ray whose pulse width is several microseconds were done in the Matlab environment,using the K-wave toolbox.Results show that the signal amplitude is low and bandwidth is wide.3)Based on the X-ray photoacoustic image reconstruction algorithm,based on the research of filtered inversion projection image reconstruction algorithm and time-reversed image reconstruction algorithm,a time reversal algorithm based on multiple interpolation algorithm optimization is proposed.The algorithm can effectively improve the quality of the imaged image.4)A single-element optical acoustic signal acquisition system is built,and the pulsed X-ray generated by the linear accelerator is used as an excitation light source to detect the generated acoustic signal.The difference between the photoacoustic signals received by the designed PZT-4 probe and the Olypus V301 commercial probe is compared and analyzed.Based on the optimized time reversal algorithm,the multi-channel parallel data of X-ray photoacoustic signals is realized.The imaging is collected to verify the correctness of the design and the reliability of the algorithm.5)The ultrasonic imaging equipment S-Sharp was improved in order to receive low-frequency and wideband ultrasonic signal.The improved device could realize the multi-channel parallel X-ray photoacoustic signals acquisition.Conclusion: Time Reversal image reconstruction algorithm with the support vector machine interpolation algorithm based on PSO optimization can obtain better effect in image reconstruction when using the X-ray as the excitation light source.For better acquisition of the acoustic signals excited by X-ray,the probe with high sensitivity,wide bandwidth and the central frequency near 70 kHz needs to be designed.The imaging is collected to verify the correctness of the design and the reliability of the algorithm.