In order to know the dose rate of Co60
γ-ray in the finite distances in air, a simple sliding rule of the dose rate for Co60
γ-ray has been made based on the decay factor, the inverse square law and the fiield factor.
In order to obtain materials for diagnosis as correct as possible, the author studied the method of soft graduation : he lowered the contrast of the limited affected part and the other wider part of the film as much as they could diagnosis by the film. Among the developers for soft graduation on the market, Paphydol, Pandol and Minidol, Pandol was proved to be the most suitable for that method of soft graduation. Moreover, the method was applied to radiographing hand joint, ankle joint, lumbal vertebra, the nipple and thoracic and alimentary canal. The conclusion obtained from above studies was as follows : The method of soft graduation does never debase the quality of X-ray photographs, so far as it is used for a certain purpose or some limitted parts. Moreover, the method makes it possible to obtain more correct and more comprehensive materials for diagnosis.
There have been a lot of studies obout many factors on which the quality of a X-ray photograph depends. The geometrical relation between the blende and screen is one of tne factors. Here, the experiments were made to examine how the relation made an influence on the X-ray grame. Some ways of radiographing were examined under the following conditions. a) 1. the castte and blende were put closely. 2. the castte and blende were set at a some distance from each other. b) Setting apart the holder in front of the casette and attached it to the screen closely. (the way is so called S-type framework) The results obtained showed that the latter is excellent to the former both in density and sharpness. The S-type framewoyk means that the front screen and the blends are combined directly and the plate in front of the casette is put away.
By using the condenser discharge X-ray apparatus, they fixed the charge voltage and suspended the discharge at a suitable voltage by photo-timer control, in order to obtain a radiography of a fixed censity. Needless to say, there is a certain relation between the chest thickness of the patient and the voltage under a suspended discharge. The author studied that relation, comparing with the relation between the voltage under the suspended discharge and weight and specific weight of patients. These relation were studied statiscally in the view of age and sex of patients. The conclusion obtained from the study mentioned above was as follows : -Among the chest thickness, whight and specific weight of patients, the first has most to do with the voltage under the suspended discharge, on which weight has more influence than chest thickness. Comparing both sexes who have the same chest-thickness, same weight and specific weight, the voltage under the suspended discharge of women is apt to be higher than that of men. Among common adults from 20 years old to 50,there was found no special relation between age and the voltage under the suspended discharge.