Quasi-monochromatic parallel radiography achieved with a plane-focus x-ray tube

摘要

Fundamental study on quasi-monochromatic parallel radiography using a polycapillary plate and a plane-focus x-ray tube is described. The x-ray generator consists of a negative high-voltage power supply, a filament (hot cathode) power supply, and an x-ray tube. The negative high-voltage is applied to the cathode electrode, and the transmission type target (anode) is connected to the ground potential. The maximum voltage and current of the power supply were -100kV (peak value) and 3.0mA, respectively. In this experiment, the tube voltage was regulated from 20 to 25kV, and the tube current was regulated by the filament temperature and ranged from 1.0 to 3.0mA. The exposure time is controlled in order to obtain optimum film density, and the focal spot diameter was about 10mm. The polycapillary plate is J5022-21 made by Hamamatsu Photonics Inc., and the outside and effective diameters are 87 and 77mm, respectively. The thickness and the hole diameter of the polycapillary are 1.0mm and 25 μm, respectively. The x-rays from the tube are formed into parallel beam by the polycapillary, and the radiogram is taken using an industrial x-ray film of Fuji IX 100 without using a screen. In the measurement of image resolution, we employed three brass spacers of 2, 30, and 60mm in height. By the test chart, the resolution fell according to increases in the spacer height without using a polycapillary. In contrast, the resolution slightly fell with corresponding increases in the height by the polycapillary. In angiography, fine blood vessels of about 100 μm are clearly visible.