HIFU Pulse Waveform Reconstruction Based On Robust Hydrophone Feature Parameters Inversion

With the rapid development of the ultrasound medical device market at home and abroad,High Intensity Focused Ultrasound(HIFU)is gradually gaining public attention because of its non-invasive and non-invasive nature as well as its technical advantages in tumor treatment.In the field of medical ultrasound,accurate measurement of HIFU sound field parameters is essential for developing clinical protocols and safeguarding treatment outcomes.In recent years,hydrophone measurement is one of the most widely used sound field measurement methods worldwide.However,because the high-intensity focused ultrasound of HIFU may damage the normal hydrophone,researchers usually use a robust hydrophone with a protective layer for sound pressure measurements.However,because the robust hydrophone with a protective layer suffers from non-flat frequency response and spatial averaging effect problems,which may lead to distortion of the HIFU pulse waveform.Therefore,the purpose of this paper is to investigate the effect of the characteristic parameters of the robust hydrophone on the HIFU pulse waveform and further reconstruct the HIFU pulse waveform.The specific work is accomplished as follows:1.At present,the hydrophone sound pressure sensitivity calibration is mainly divided into primary calibration and secondary calibration based on the reference hydrophone,and it is found that the primary calibration has the disadvantages of tedious and time-consuming operation process compared with the secondary calibration,so in order to realize the rapid calibration of hydrophone,the paper adopts the secondary calibration comparison method to study the calibration of hydrophone sound pressure sensitivity.Firstly,a theoretical analysis of the non-flat frequency response problem caused by the missing phase in the current comparative calibration method is carried out,and the phase information is obtained by Hilbert transformation of the sound pressure sensitivity in the minimum phase system.Further,the problem of spatial averaging effect caused by the aperture of hydrophone in comparative method calibration is discussed,and a correction model of spatial averaging effect is established by analyzing the sound beam width of ultrasonic field and the effective radius of hydrophone.Finally,through experiments on different types of hydrophones with different apertures,the average relative error after correction is reduced by 9.2% compared with that before correction,and the measurement uncertainty is close to the certificate value.2.The reconstruction study of the HIFU pulse waveform by the inversion of the robust hydrophone characteristic parameters is carried out.For the traditional method of amplitude-frequency deconvolution to reconstruct the pulse waveform,which can underestimate the measured HIFU sound field parameters due to the lack of phase information,the method of complex-frequency deconvolution to reconstruct the pulse waveform is proposed.By characterizing the frequency response of sound pressure sensitivity and spatial averaging effect,the HIFU pulse waveform reconstruction model is established,and it is finally determined through experiments that the reconstruction method based on complex-frequency deconvolution improves the peak compressed sound pressure by 12.4%,the peak sparse sound pressure by 16.4%,and the pulse intensity integral by25.5% compared with the traditional method.