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

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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