COMPARATIVE STUDY ON THE DIAGNOSTIC VALUE OF 70 MM RADIO PHOTOGRAM BY ODELCA CAMERA AND CANON MIRROR CAMERA:Report I. The Results of Basic Experiments

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Comparative study was made on the diagnostic value of 70 mm radiophotogram by Odelcacamera and Canon mirror camera. The results of basic experiments were presented in thisreport, and the results of clinical experiments will be mentioned in the second report. Pictures were taken by both cameras using tube voltage from 65 to 80 kV at 5 kV interval.Correlation between the density of picture and the tube voltage was shown in Fig. 5, and thedensity of picture by Odelca camera was slightly higher than that by Canon camera on thesame tube voltage. The density of pictures by both cameras was measured along the middle horizontal line, andthe results were presented in Fig. 6. The density was highest in the central part, and becamelower in the peripheral part. The decrease of density in the peripheral part was slightly lessin the case of Canon camera than that of Odelca camera. The resolving power of cameras was measured by three different methods. In the first experiment, the maximum number of lines clearly distinguished in 1 cm was measured by usingthe test chart made of thin leaves of lead and cupper, which was set in the middle part ofthe fluorescent screen. This chart was used as the standard test chart in U. S. A. As shownin Fig. 7, number of lines clearly distinguished in 1 cm was more in the case of Odelca camerathan that of Canon camera. In the second experiment, test chart made of cupper wire set in the'different width was used, and the minimum width in which two lines were distinguished wasread. The minimum width of two lines in which they were clearly recognized was 0.3 mm inboth cameras, and two lines with width 0.25 mm or less were not distinguished by Canoncamera. In the case of Odelca camera, two lines with width 0.25 mm were not clearly butrecognized as two lines. In the third experiment, test chart enacted in the Japanese IndustrialStandard shown in Fig. 3 was used. Charts were set on nine different spots shown in Fig. 2, and the number of dials in which two lines were clearly distinguished was read. The results were shown in Fig. 8. The resolving power was highest in the central part, and becamelower in the peripheral part. The resolving power in the central part was nearly equal inboth cameras, but the decrease of resolving power in the peripheral part was more marked inthe case of Canon camera than that of Odelca camera. In the case of Odelca camera, betterresults were obtained by using Fuji film than by using Gevaert film in all parts of the fluorescent screen, and in the case of Canon camera, better results were obtained by using Gevaertfilm in the central part, and no difference of resolving power by the film was observed in themiddle and the peripheral parts. Metal net of hexagonal shape shown in Fig. 4 was set on the focus side of the screen, andmeasurement of distorsion was made along the diagonal. The ratio of length of hexagon inthe longitudinal and horizontal direction in the center to those in the different spots wascalculated, and the results were presented in Fig. 9. The distorsion of picture by Canoncamera in the peripheral part was more marked than that by Odelca camera. The results mentioned above show that the optical ability of Odelca 70 mm camera was slightly but clearly superior to that of Canon 70 mm mirror camera.
一般社団法人日本結核病学会の論文

COMPARATIVE STUDY ON THE DIAGNOSTIC VALUE OF 70 MM RADIO PHOTOGRAM BY ODELCA CAMERA AND CANON MIRROR CAMERA:Report I. The Results of Basic Experiments

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