X射线光声成像的信号检测与仿真

Simulation and experimental detection of X-ray photo-acoustic

通过理论仿真和实验检测结果,分析由医用直线加速器产生的X射线照射铅块所产生的光声信号特性.使用光电二极管搭建一个光电检测电路,检测到医用直线加速器所产生的脉冲X射线的光脉冲宽度约为4μs.采用K-wave工具包仿真分析脉冲宽度为几个微秒的光脉冲所产生的光声信号.搭建了一个光声信号检测系统,对比分析分别使用Olypus V301商用探头与自制的PZT-4陶瓷换能器时的检测性能.结果表明,两款探头都检测到了光声信号,V301商用探头检测结果与理论仿真波形一致性较好,但信噪比低,而本研究设计的PZT-4检测灵敏度高,但检测到的信号波形与理论仿真结果偏差较大.两款探头在检测脉冲宽度为4μs的X射线脉冲所产生的声信号时都存在不足,为更好的检测该光声信号,需设计一款中心频率在70 kHz附近、带宽较宽、检测灵敏度较高的探头.

The aim of this paper is to analyze the characteristics of the photo-acoustic（PA） signal,which is induced by irradiating the lead with X-ray from a medical linear accelerator. Related theoretical simulations and experiments are done. A photodiode detection circuit is put up to detect the width of X-ray pulses,which is about 4 μs. The K-wave software is used to simulate and analyze the PA signal generated by X-ray whose pulse width was several microseconds. We also put up a single element photo-acoustic signal acquisition system and carry out the comparative experiments with Olympus V301 commercial probe and the probe designed by the piezoelectric ceramics PZT-4.Results show that both probes can detect the PA signal. The signal detected by V301 is in good accordance with the simulation signal waveform,but has low signal noise ratio. The probe designed by PZT-4 has high sensitivity,butthe detected signal deviates from the simulation waveform. Both probes have shortcomings in detecting the PA signals generated by X-ray pulse with a pulse width of 4 μs. Both simulation and experiment results indicate that a probe with high sensitivity,wide bandwidth and 70 kHz center frequency should be designed to detect the PA signal without distortion and with higher signal noise ratio.