A K-edge energy subtraction imaging system has been constructed for non-invasive transvenous angiographic research. It utilizes synchrotron radiation and consists of a monochromator, an X-ray television camera with a high-speed shutter, and a data acquisition and control unit. Kedge energy subtraction angiography of rats and rabbits were performed by intravenous injection of iodine dye. Dual-energy images were acquired using 17 msec exposures with the sau e interval. Repetition of this sequence gave a series of K-edge subtraction images. Rabbit coronary arteries of 0.8 mm diameter and rat carotid arteries of 0.3-0.4 mm diameter were clearly seen respectively. For the boundary detection of low SNR images such as intravenous coronary angiography, a new boundary estimation named minimum difference of density (MDD) method using the stochastic technique and looking for variance of integrated density of the opacified vessel was proposed.

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The structure and the radiographic characteristics of a compact pulsed x-ray tube utilizing a pipe-shaped graphite cathode for biomedical radiography are descri. This x-ray tube for producing pulsed x-rays consisted of the following major parts: a rod-shaped long anode tip made of tungsten, a pipe-shaped graphite cathode, and a glass body. This tube can be driven by various kinds of high-voltage pulsers. In this experiment, the tube was driven by the simplest single-stage pulser with a condenser capacity of about 1700pF. Since the condenser was charged from 40 to 100kV, the output peak voltage was less than 100kV. The average pulse width was less then 300ns, and the x-ray intensity was less tahn 1.0μC at 0.5m per pulse. The x-ray quality became hard according to increases in the charging voltage and insertion of metal filters. The effective focal spot size was primarily determined by the diameter of the anode tip and ranged from 0.5 to 3.0mm in diameter.

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The fundamental studies for the long-duration flash x-ray generator utilizing a cold cathode radiation tube for biomedical radiography are described. This generator consisted of the following components: a high-voltage power supply, a high-voltage coaxial oil coondenser of 0.2μF-100kV, a vacuum pump, a trigger system for the cathode, and an x-ray tube with a set of graphite cathodes. When trigger currents flowed across cathode electrodes, the main discharge for producing flash x-rays was generated. The x-ray output was a single pulse and its pulse width was about 5.0μs. The x-ray pulse height and the time integrated intensity increased when the condeser charging voltage was increased, and the intensity was less than 2.0μC/kg at 1m per pulse. The x-ray quality became hard according to increases in the charging voltage and to the insertion of metal filters. The effective focal spot size was primarily determined by the diameter of anode tip and was less than 3.0mm in diameter.

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The voltage-ripple dependence relations on x-ray spectra and mean energies at 70 kVpeak were obtained theoretically by using the semi-empirical formula of emission spectra given by Birch and Marshall (1979). The calculations were carried out for objects of various thicknesses of acrylic resin and aluminium, and also without an object. As the ripple increases, the spectral componeuns generally move to the low photon-energy side. But with the ripple at 40-60%, the spectral components return slightly to the high photon-energy side in both the saturating and unaturating current modes. Therefore the mean energy reaches the minimum value at 40-60%ripple. This phenomenon was pointed out by Birch et al (1979) only for the saturating current modes. We found this phenomenon also for the unaturating current mode. We verified this phenomenon experimentally for the saturating mode. The reasons for this phenomenon were clarified.

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The ability of planar Ge detector has been examined to measure soft X-ray spectra (less than about 30keV). The two Ge detectors, whose crystal sizes were 6mmφ×5mm and 10mmφ×7mm, were used. By performing the Monte Carlo simulation, the detector response functions for two detectors were numerically obtained at the energy interval of 02 keV for the incident monoenergetic photons of every 0.2 keV. No difference was found for the two detectors in the soft X-ray region. The spectra of soft X-rays transmitted through the polyvinyl chloride with various thicknesses were measured by using the two Ge detector systems. The measured spectra were corrected by using the detector response functions. The results showed that the Ge detector systems were profitable for the measurement of soft X-ray spectra.

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We measured the fading effect in a relatively short time (minute order) on Imaging Plate indirectly from pixel value. We ascer lore fading effect than been recognized. So, especially when we measure the digital characteristic curve of FCR system, the fading effect cannot be ignored. Therefore we prevented a change of the digital characteristic curve from fading effect to some degree when we read images after 20 minutes from an exposure.
Nevertheless, when we measure in a small latitude, the fading effect is strong and we can't get a true digital characteristic curve.
But, by use of exposure with aluminum step-wedge method, we finally had a good result.

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