The relation between the exponent of tube voltage and photographic effects has been studied by many experimenters both at home and abroad. In these experiments, however, the numerical value is apt to be different in every case, and most of the conditions remain unexplained. In order to throw light on this relation, the following experiments were devised. 1) Exponents of tube voltage were counted at every additional 60 kVp, under low voltage. 2) In order to gauge the thickness of object and filter, which are the factors of difference in the numerical value, the Al Keil phantom was used. 3) These experiments were based on the deristy gradient. From these experiments the following conclusions were obtained. 1) The exponent was not constant as tube voltage changed The difference in thickness of objects and filters made the exponent change a little. 2) A filter 0.5 mm.-1.0 mm, thick was considered to be the most suitable to decrease absorbed dose and to get good photographic effects. 3) The exponents counted in these experiments were put into the form of a diagram, which was used to take radiograms in a rational manner. This was found to be clinically useful.
Recently Ellis and Krantz reported that the total digestive tract is able to be rapidly contrasted by adding Sorbitor, a kind of hexose, into the usual contrast medium of barium surfate. We tried various modifications of this method and obtained a optimal ratio of mixing for Japanese. Time for passage was considerably different according to individuality and concentration of Sorbitol (ratio of mixing). Our observations, however, revealed that mixture of 100-150g of barium sulfate, a viscsus substance (consisting of 0.5g of C.M.C. and 1.0g of Arabian rubber), 200-300cc of warm water, and 15% of Sorbitol was appropriate. Characteristics of Sorbitol as well as addition of the viscous substance made it possible to observe filling and mucosal relief pictures of the total digestive tract within considerably short time (3-5 hours after oral administration). Moreover, the photographic evaluation bore comparison with the customary method. In addition, the appendix was visualized in more than 90%, that is, the presenting method had even more extensive diagnostic field than the ordinary one.
The greatest possible reduction in the dosage of X-rays for use in roentgen diagnosis is in urgent need, as has been pointed out by the I.C.R.P., if the hereditary transmission of the injurious effect of the rays-the effect on the reproductives organs of direct or scattered rays, in particular, -is to be prevented, although it is none the less important that X-ray photographs taken for diagnostik purposes are not at the same time reduce in accuracy on that account. The author's investigation into the problem seems to have thrown some light on the desirable conditions under which the danger of roentgen diagnosis may be minimized. The conditions was described under seven different headings below. 1. Frequency of exposure. 2. Dosage. 3. Field. 4. Filterring. 5. Environmental. 6. Legal. 7. Clothing.
In radiography of the dorsal spine (A-P), the image of thoracic vartebrae is blurred because the contrast between it and that of the surrounding organs is excessively intense. In order to get a clear image that is significant in diagnosis, the authors used a slit filter made of copper and aluminum, which not only eliminated the scattering X-rays and decreased the useless surface dose but also reduced the difference in contrast between the two images. This method was applied to radiography of hyphotic thoracic vertebrae with good results.
As radiation is more extensively used, the measurement of absorbed dose has been called in question in the fields of industry, medicine, etc. And extrapolation chamber was manufactured to be used especially in medical treatment, in an attempt to measure accurately the absorbed dose in patients. Using this chamber, the following experiments were made : 1) Based on the principle of the Bragg-Gray cavity theory, the absorbed dose (rad) in acrylite was measured. 2) Various kinds of filter swere used, and the build up curve of Co 60 γ-ray in acrylite phantom was drawn. The results of these studies made it possible to select the most suitable filter for Co 60 irradiation.