Technical studies of angiotomography for good demonstration of the vessels in the basal ganglia were described using a Princeps 50 unit. From analyses of image quality and blurring effect of interfering shadows in multilayer tomography, the following technical factors were obtained for good demonstration of the vessels : five simultaneous cuts at 2mm interval and swing angle of 30〜40 degrees in lateral projection, and five simultaneous cuts at 5 or 10mm interval and swing angle of 10〜20 degrees in frontal projection. Combination with photographic subtraction was particularly useful for good visualization of intracerebral avascular area.

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As for attenuation of X and γ-ray intensity which varies with source distance, inverse squares law is applied. But it is not satisfied for actual case because of extended sources and absorption by air. Therefore intensity is shifted from inverse squares law, so we calculated shifting ratio from the law based on X and γ-ray spectra. As a result, the ratio varies with the size of the source and distance from it, and X-ray intensity in diagnosis, in case of standard value at 1 meter, is shifted within ±5%, ±8% for dose and fluence respectively.

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A preliminary approach was made for the development of satisfactory breast phantoms for evaluating mammography techniques. The initial effort was made to select the test object materials which simulate the breart tissues. A physical comparison of the test objects with breast tissues was made by obtaining the image contrast theoretically and experimentally. A good agreement of the results obtained by the two methods made it possible to expect roentgenographic detail at a visual threshold where the image contrast would not be measured. The results obtained by this study are summarized as follows : 1) Lucite absorber was more absorbent than the average breast by 25%, which corresponds to a 5 cm thick water-polystyrene composite absorber in which polystyrene comprised 36% in thickness (nearly equal to that by weight) at 30kVp, and the percentage varies from 35% to 40% in the range of 40〜20kVp. This implies the possibility of making a solid absorber by combining plastic plates, i. e., 4cm Lucite plus 1 cm polystyrene as a substitute for an average breast containing 50% fatty tissue, and 2cm Lucite plus 3cm polystyrene for an atrophic breast containing 70% fatty tissue, polystyrene being very nearly fat equivalent. 2) A high Z material like aluminum offers a negligible scattering medium compared with plastic absorbers. An aluminum test piece placed in direct contact with the film yields a higher image contrast than that placed further from the film so that it should be positioned 5 mm above the film when minimizing a geometrical effect. 3) Mammary carcinoma and blood vessels were theoretically simulated by a solution containing 1% cupric sulfate by weight in distilled water. Roentgenographic evaluation proved that the solution filled in cylinders is a satisfactory substitute for blood vessels. Water columns were less opaque. X-ray absorption of microcalcifications in the paraffin tissue block was the same as the one of quartz glass because they can be assumed to contain 50% tricalcium phosphate. 4) A reduction in the percentage of polystyrene from the composite absorber markedly decreased the image contrast of low Z materials. It is believed that fat involution in the breast is a very important factor for detecting a small carcinoma or fine blood vessels but not so much for calcifications. 5) Minimum perceptible contrast of cylindrical objects was presumed to be 0.008 to 0.01,the corresponding diameteer of which was 1 mm for water and 0.6mm for 1% cupric sulfate solution. Calcification required a rather high contrast of 0.06 for its detection and this implies that visibility of such minute flecks would be limited by the grain of the film. A tentative drawing of the phantom consisting of two parts was made. One represents the contour of the breast by a sloped Lucite block, and the other, positioned at the bottom, is made of 1 cm thick Lucite slab of 8×12cm in size. A number of tapped holes filled with a diluted solution of cupric sulfate, and microbeads of quartz glass enbedded in areas of 5×5 cm each in the slab are used to nullify the heel effect. This slab can be detached and placed at any level of the plastic blocks of uniform thickness for evaluation of changes in the object-to-film distance.

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To improve the film graininess, we have tried the reversal development method. As the larger silver grains, which are more sensitive than smaller ones, are removed more than smaller ones from the emulsion of film in the process of bleaching, the graininess of the reversally developed film is much better than that of the original negative film. Film graininess is improved especially at the part of higher density of negative X-ray film. We investigated the modulation transfer function, autocorrelation function and Wiener spectra as to reversal and negative films. The results show that MTF of reversal and negative X-ray films are almost same and so depend only on the sensitivity of intensifying screens.

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Metastasis to bone of malignancy can not be recognized on the skeletal radiographs until 30 to 50% of decalcification is attained by direct bone destruction and accompanying bone absorption. This would require a sufficiently long time, and delay an early recognition of the lesion. The initial lodgement of tumor cell occurs in the active marrow, and the tumor would evade the cells of the reticuloendothelial system as it grows and invades the surrounding tissue. This is expected to be recognized on the bone marrow scintigrams earlier than the radiographs, and hopefully bone scans when appropriate radiocolloids are employed. The present investigations were undertaken in order to know the best preparation kit of ^99mTc sulfur colloid commercially available at the moment, and to explore the possibility of early diagnosis of bone metastasis by bone marrow scinitigraphy employing that colloid. (a) Marrow scintigrams depicted the metastatic bone lesions at the time of positive bone radiographs, and (b) they were indicative of lesions even when the bone scans and radiographs were negative. These results indicate that the bone marrow imaging would permit diagnosis of bone metastasis earlier than the bone scans and radiographs.

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The following results were obtained by the 4 sheet used-screen (front)+2mm Al of inserted filters for the chest high voltage radiography. 1. Wide diagnosis and dosage were attained by employ reduction 4 sheet used-screen (front)+2mm Al as inserted filter in 140 kVp. 2. Satisfactory results were obtained in both lateral and oblique radiography in 140 kVp. 3. Favorable results were observed by employing 6 sheet used-screen+2mm Al as inserted filter for taking a photograph of corpulent patients those who have marked difference in density especially for the investigation of mediastinal position.

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