. The American journal of roentgenology, radium therapy and nuclear medicine . ter. Therefore I looked for anothermethod, dilTerent from that of Holfelder,in order to get the results, and investigatedse\eral .v-ray cones in water-])hantoms The Use of Isodosis Curves in X-Ray Therapy 899 using a photographic tihii for measuringthe [relative intensities. The iihns weredeveloped immediately after size reproductions of these fdmsare shown in Figures 2, 3 and 4. Figure 2 shows a narrow cone of .v-ray,having a width of 6 cm. at a focal distanceof 70 cm., using the same quality of ra
. The American journal of roentgenology, radium therapy and nuclear medicine . ter. Therefore I looked for anothermethod, dilTerent from that of Holfelder,in order to get the results, and investigatedse\eral .v-ray cones in water-])hantoms The Use of Isodosis Curves in X-Ray Therapy 899 using a photographic tihii for measuringthe [relative intensities. The iihns weredeveloped immediately after size reproductions of these fdmsare shown in Figures 2, 3 and 4. Figure 2 shows a narrow cone of .v-ray,having a width of 6 cm. at a focal distanceof 70 cm., using the same quality of radia-tion as for making the diaphragm was close to the surface of distance of 80 cm., where the diaphragmwas placed in the center between thesurface of water and the focal point. Herethe film was placed slightly at a slant tothe center ray, so that there seems to be aconvergence of the rays toward the depth,which, however, shows only the obliquesection of the cone. In this case too, wecan see a perfect agreement with themeasurements, and the fundamental form. Fig. 3. A wider cone shows the same form of distribution of intensities. Thestray-field is only slightly stronger than that of a narrower cone. Thisfilm was taken with a focal distance of 50 cm. and a diaphragm of 12 The conditions of tests were the same as before. This shows,too, the exact agreement with the Holfelder curves, and the strongdifference from Dessaucrs forms. Reduction one-third original size. the water in this case. One can clearlysee the rather deep sharply defined coneand the weak pear-shaped stray fieldaround the same. Figure 2 shows the sameproportion with a field of 12 cm. in widthand having a focal depth of 50 cm. Herewe have also found a complete agreementwith the iontoquantimetric results. Figure3 shows a narrow cone having a focal is the same as in the other pictures, exceptthat the edges seem to be slightly blurred,due to the effect of a partial shadow. Whenmaking expos
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