| Co-Investigator(Kenkyū-buntansha) |
KAWASAKI Satoshi Department of Physics, School of General Education, Iwate Medical University, 教養部物理, 助手 (70195072)
FUJIYAMA Toshiaki Department of Pyhsics, School of General Education, Iwate Medical University, 教養部物理, 助手 (20173479)
SATO Sanae Department of Physics, School of General Education, Iwate Medical University, 教養部物理, 助手 (50154050)
SATO Eiichi Department of Physics, School of General Education, Iwate Medical University, 教養部物理, 講師 (90154038)
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| Research Abstract |
Fundamental studies for the high intensity flash x-ray generators for biomedical radiography are described. The single flash x-ray generators are as follows: (a) a high intensity type (less than 100kV) for performing the soft radiography, (b) a low-impedance and high intensity type (less than 120kV) for obtaining radiographs of tissues deep inside of the human body, and (c) a portable type (less than 200kV). Each generators had the control functions for the x-ray intensity, the spectrum distribution, and the effective focal spot size, and mainly consisted of the following essential components: a high voltage generator, a pulse condenser, a gas gap system, a turbo molecular pump, and a flash x-ray tube using field emission.
Two types of the triple-pulsed x-ray generators consisted of the following components: a high-voltage generating unit, a voltage divider unit, three high-voltage generating unit, three high-voltage pulsers used for a portable generator, a tiple parallel impulse switch
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ing system, a high-power gas diode having three terminals, a turbo molecular pump, and three remote x-ray tubes having cold cathode. For the single-tube generator, the pulsers were charged to the same or different voltages by using a voltage divider unit and were connected to the x-ray tube through a high-power gas diode using SF_6. For the triple-tube generator,since three pulsers were connected directly to the tubes without a diode, three x-ray outputs could be obtained simultaneously. The minimum time intervals for the single-tube and the triple-tube types were about 100 and 3us, respectively. The x-ray intensities increased in proportion to the third or fourth power of the charging voltage. The pulse width was less than 300ns, and the x-ray quality (average spectrum distribution) became hard according to increases in the charging voltage and increases in the thickness of metal filters inserted outside of the x-ray window. The effective focal spot size could be reduced by decreasing the anode angle, decreasing the cathode diameter, decreasing the anode-cathode space, and inserting the metal filters.
The high-speed radiographic system consisted of the following components: two types of delay switches,i. e. (a) direct switching and (b) laser switching, a delayed pulse generator, a CR system,and an FX generator. When the radiographic object triggered the delay switch, a short electric pulse was produced and was transmitted to the delayed pulse generator. An accurate delayed x-ray pulse was produced when the delayed pulse was transmitted to the high-speed impulse switching system. Next, when the radiographic object was exposed to the controlled x-rays under the optimum radiographic conditions, the permeating x-rays produced the digital image. Since the time resolutions for two types of delay switches were less than 20ns, the total time resolution for the x-ray production was less than 1<micrn>s. Various kinds of high speed biomedical radiography, e. g., the stroboscopic radiographgs, the continuous delayed radiographs the energy subtraction radiographs, and the continuous three-dimensional analysis could be performed by controlling the radiographic conditions. Less
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