Japanese Journal of Radiological Technology

As a means to extend the diagnostic range with a bone radiograph we have made aluminum filters conforming to the density distribution pattern of object. 1) The outline and thicknesses of each filter were calculated from the characteristic curves of a film of a stepped aluminum model X-rayed on the same voltage as that for the object. 2) The contour lines of the stepped aluminum model were drawn on an X-ray fiim. On the basis of this drawing and the reduction ratio of the focus-film distance, aluminum plates were cut out and pasted together to form the filter. 3) The compensation, which can be made in two direction, is especially useful in X-raying an area having a complex density distribution pattern. 4) The picture taken through the filter, although somewhat reduced in clearness and contrast due to light suppression, permits a wider diagnostic range.

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For finding the equation to calculate volume dose in telecobalt therapy, the experiment and the theoretical consideration were carried out, and the following result was obtained. The volume dose (VD) can be calculated as the following equations. If X≦10cm VD=F_0D_6 {28.3-(28.3+0.694X)e^<-0.0634X>} [gR] If X≧10cm VD=F_0D_6 {27.27-(27.50+0.58X)_e^<-0.0634X>} [gR] F_0 : Irradiated field (cm^2) D_0 : Irradiated dose X : Thickness of irradiated body (cm) Abave equations are arailable provided that source-skin distance is from 35 to 110cm. The volume dose factor calculated by the above equations is placed on the table 1 so that volume dose could be calculated extremely simple. The volume dose is proportionate to irradiated field and irradiated dose of center of irradiated field in telecobalt therapy.

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The authors have reported on the study of the principle and a part of medical application of Xeroradiography. (1). Se sensitive plate has similar sensitivity to X-Ray film, however, in fact, it can not be used with the intensifing screen without special divice as it apply to statical electricity, therefore, it has greatly defection for medical application of Xeroradiography that Se sensitive plate ha very lower sensitivity than the combination of X-Ray film and intensifing screen has. Cu and Al filterin addition reduce the exposed dose without changing original X-Ray exposure factors. It is concluded that the technique of filter addition is value in reducing the exposed dose for medical application of Xeroradiography. (2). There are many discussion of edge effect, however, there are little discussion of density distribution of Xeroradiography. Radiograph is negative picture which is made by X-Ray film and Xeroradiograph is positive picture which is made by made by Se sensitive plate, that is, Radiograph has transmission density and Xeroradiograph has reflection density. Then the reflection density were caluculated and was compared relatively, not absolutely, with transmission densiety of Radiograph. It is improved that the reflection density distribution of Xerodiograph comes to singularity which has narrow range as compared with the transmission density distribution of Radiograph.

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In order to deal with the rapid increase of X-ray films in our hospital, we have recently equipped two automatic developmental apparatus (RP X-OMAT PROCESSOR M6-N), which, however, bring up the following problem. When we develop, for instance, many films exposed under the same radiographic conditions, by using these two apparatus, we try so that they would produce the same results in respects to the film density and its contrast. As to produce proper results, we must pay special attention in controlling them. This paper has referred to these points and our experimental result.

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