Development of a Dual Flash X-Ray System Having a Spectrum Control Function and its Application to Medical Shock Wave Research

随着高压脉冲技术的进步，各种闪光x射线发生器已被开发出来，对应于特定的射线照相物镜，光子能量低于150 keV的软发生器已被设计用于软高速射线照相，包括生物医学应用。与体外冲击波碎石术（ESWL）相结合，迫切需要在活体组织中可视化冲击波诱导的空化，而气泡的时空分布尚未在体内观察到。为此，我们研制了两种类型的双闪光x射线发生器，并对等离子体x射线源进行了提高闪光x射线强度的基础研究。每个闪光x射线发生器由以下基本部件组成：高压电源、极性反转高压脉冲发生器、涡轮分子泵和两个闪光x射线管。脉冲发生器内的组合式陶瓷电容器在50 ~ 80kv范围内由电源负充电，电容器内的电荷通过两根同轴电缆排至两根管中。这样就同时产生了两束闪光x射线（A型）。在使用两个脉冲器的情况下，两次射击之间的时间间隔可以控制（类型B）。等离子体x射线源对产生高强度闪光x射线非常有用，因为当该源在靶处形成时，静电能量转化为x射线的效率大大提高。使用几种不同类型的等离子体x射线源，我们成功地产生了更高强度的特征x射线。为了在高速射线照相前对射线图进行粗略的计算和想象，我们开发了一个图像模拟系统（SPECTRA）。在该系统中，利用闪光x射线发生器获得的有关管电压和电流的数据计算包括特征x射线在内的光谱分布，并在CRT上观察射线图（灰度级）。利用这些闪光x射线发生器（本工作开发）与图像模拟系统相结合，我们成功地对ESWL实验中空化气泡云的时空分布进行了成像。少

Together with advances in high-voltage pulse technology, various kinds of flash x-ray generators have been developed corresponding to specific radiographic objectives, and soft generators with photon energies of less than 150 keV have been designed to perform soft high-speed radiographies including biomedical applications. In conjunction with the Extracorporeal Shock Wave Lithotripsy (ESWL), there is an urgent need for visualizing shock wave induced cavitation in living tissue, and the spatial and temporal distributions of the bubbles have not been observed in vivo. For this purpose, we developed two types of dual flash x-ray generators and performed fundamental studies on the plasma x-ray source for increasing flash x-ray intensity.Each flash x-ray generator consists of the following essential components : a high-voltage power supply, a polarity-inversion high-voltage pulser, a turbo molecular pump, and two flash x-ray tubes. A combined ceramic condenser in the pulser is negatively ch … More arged from 50 to 80 kV by the power supply, and the electric charges in the condenser are discharged to two tubes through two coaxial cables. Thus two shots of flash x rays are then produced simultaneously (Type A). In the case where two pulsers are employed, the time interval between two shots can be controlled (Type B).The plasma x-ray source is quite useful to produce high-intensity flash x rays since the conversion efficiency of electrostatic energies into x rays substantially increases when this source is formed at the target. Using several different types of plasma x-ray sources, we succeeded in producing higher-intensity characteristic x rays.In order to roughly calculate and imagine radiograms before high-speed radiography, we developed an image simulation system (SPECTRA). In this system, the spectrum distributions including characteristic x rays are calculated by the data concerning the tube voltage and current obtained by the flash x-ray generator, and the radiograms (gray levels) are observed on a CRT.Using these flash x-ray generators (which were developed in the present work) in conjunction with the image simulation system, we succeeded in imaging the spatial and temporal distributions of the cavitation bubble clouds in the ESWL experiment. Less