In the plasma flash x-ray generator, a high-voltage main condenser of approximately 200 nF is charged up to 55 kV by a power supply, and electric charges in the condenser are discharged to an x-ray tube after triggering the cathode electrode. The flash xrays are then produced. The x-ray tube is a demountable triode that is connected to a turbo molecular pump with a pressure of approximately 1 mPa. As electron flows from the cathode electrode are roughly converged to a rod molybdenum target of 2.0mm in diameter by the electric field in the x-ray tube, weakly ionized linear plasma, which consists of molybdenum ions and electrons, forms by target evaporation. At a charging voltage of 55 kV, the maximum tube voltage was almost equal to the charging voltage of the main condenser, and the peak current was about 20 kA. When the charging voltage was increased, the linear plasma formed, and the K-series characteristic x-ray intensities increas&l. The K lines were quite sharp and intense, and hardly any bremsstrahlung rays were detected. The x-ray pulse widths were approximately 700 ns, and the time-integrated x-ray intensity had a value of approximately 35 pCikg at 1.0 m from the x-ray source with a charging voltage of 50 kV.

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Treatment planning for ultrasound-guided transperitoneal 1-125 permanent prostatic implants is a time consuming task, because this treatment uses many seeds (e. g.50-80) and there are many solutions (seed positions) for optimizing the dose distribution. In conventional treatment planning for brachytherapy the locations of sources are usually input into a computer manually with reference to two X-ray films. We use so many sources in this treatment that we can hardly obtain accurate location of each source. That is, the identification of each seed with two X-ray films is very difficult. Even though we can use X-ray CT images for deciding on the source position, there are artifacts due to the high attenuation material. This paper proposes a method for obtaining accurate locations of radioactive sources from some projection data (e. g. RPO 60,40,20, LPO 60,40,20 and 0 deg. ) with a reconstruction method. In our method for obtaining actual source positions we use an iterative image reconstruction technique. The results obtained by experiments with a simple prostate phantom and the RANDO phantom showed that the locations of dummy seeds were accurately decided with a reconstructed image by six or seven projection data.

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A guideline for quality assurance of CT systems for radiotherapy treatment planning is proposed. Quantitative interpretation of CT number is very important especially for range calculation in heavy charged particle radiotherapy, for which we adopted the polybinary calibration method to correct variations among CT systems and scanning conditions. Practical procedures for comissioning and constancy testing are documented along with the methodologies against various sources of uncertainty. We propose this guideline for quality assurance of heavy charged particle radiotherapy.

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A simple model for efficiency analysis of daily operation in proton radiotherapy is applied to numerical calculation with fixed time advancing. For the simplifying, man power is assumed to be enough and troubles in the equipments are ignored. To generate random numbers which become the time for adjusting the patient position and for waiting the next patient, typical probability distributions are utilized in the simulation. By using the simulation, treatment capacity of a facility is estimated for different number of treatment rooms to know the efficient number of gantries for proton radiotherapy.

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We developed micro blood vessel diameter measurement algorithm for angiography using refraction contrast by monochromatic X-ray of the 3rd generation synchrotron radiation with the high degree parallel beam. The accuracy is evaluated using the actually obtained image.

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