It has been reported that infants' positions in taking roentgenography have great influence on lung marking and that lying positions result in mose difficult examination than standing positions because in the former lung fields are compressed arud lung markings, condensed mainly due to the elevated diaphragma and transversally dilated heart shadows. Many cases of infants' chest films were examined measuring the hight and vertical and transversal diameter of the thorax, transversal diameter of heart and square measure of the lung field and thorax in either lying or standing position. No significant difference between lying and standing position was found leading us to conclude that lying position as well as standing position will do without resulting in condensed lung marking due to the elevated diaphragm and transversally dilated heart.
Various methods to decrease surface doses in taking a radiography have been deviced. It one of the methods of decreasing surface dose to cut X-ray of long wave by using a filter. By using the combination of Cu and Al, several experiments were made according to every voltage from high to low one. The several kinds of filter were found so be able to decrease surface dose without having an effect on the brightness of screen.
In the X-ray dosimetry of X-ray depth therapy unit, cone type or distance of mersurement have been paid no attaintion. The experiments on the infulence of cone type in the X-ray dosimetry were made and the following results were obtained. 1) Out put dose increased in proportion to the field of cone. 2) Out put dose increased in proportion to the cone length. The phenomena mentioned in 1) and 2) were caused by that off focus X-ray was cut off by diaphragm of cone. 3) The increase of effective focus size caused by the contamination of off focus X-ray led the phenomena of inverse squers law to fail. Those results came to a conclusion as follows : In the X-ray dosimetry of X-ray depth therapy unit, the thimble chamber shuld be contacted with the front part of the cone.
The sharpness, focus of skin distance and proper density in taking an enlargement high voltage chest radiography were examined by using a rotating anode X-ray tube with 0.3×0.3mm focus under the high voltage of 140 kVp. The following results were obtained from those experiments : The lowering of sharpness caused by enlargement of image were found in the half shadow of 0.3-0.6mm lengthened 1.7-2 times as long as that in usual radiolography. The focus of skin distance of 70 : 50cm was good. As for the density, the thickest one of 1.4-1.6 was most proper.