Japanese Journal of Radiological Technology

The method of superimposition display with the chest scintigram and the perfusion scintigram has been described using the small computer system with 16K of core memory. The chest scintigram is obtained using ^<197>HgCl_2 or ^<67>Ga-citrate, and patient remaining in the same position is given ^<99m>Tc-MAA for perfusion imaging. These images are transferred from the core memory to the magnetic tape recorder. In order to improve the radioisotopic image quality, authors have used some correction techniques by the computer as follows. 1) Correction for a uniformity of the scintillation camera. 2) Two-dimensional filtering. 3) Background subtraction of the chest scintigram. The perfusion scintigram is superimposed to the chest scintigram. The superimposed image is displayed using the 4010 CRT display and the TV display. This processing was useful not only to improve anatomic information of the chest scintigram but also to make radioisotopic diagnosis of various lung diseases more reliable.

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A comparison of ability to detect minute calcifications was theoretically made with the geometric conditions varied. The results obtained by this study are summarized as follows : 1) Direct radiographic magnification with a microfocus X-ray tube will be useful detecting dot-like objects such as calcifications, especially with Mo-target tube by the reasons described below. 2) Magnification technique will produce revers effect on differential diagnosis, if it is achieved at the cost of total MTF by using excessively high speed screens. It requires high resolution to distinguish malignant from benign tumors, which is mainly determined by intensifying screens used. On the other hand, fine graininess is required for detecting calcifications, which is limited by mottle size of the film almost regardless of the screens used. This implies that visual performance done by dot-like patterns only might lead to an erroneous conclusion. 3) The MTFs of mammographic screen-film systems using rare-earth screens, which could be approximated by Gaussian distributions, show higher value at low spatial frequencies than those of convential fine screen-film systems approximated by exponential distributions. This makes it effective to use magnification technique because a certain spatial frequency is shifted to lower frequency region. 4) Contact mammography using a tungsten-anode tube with small focal spot, for instance 0.3 mm, could not produce images superior in visibility to those obtained by larger focus, as has been reported previously, because of being accompanied by the use of higher tube voltage. However, a Mo tube minimizes the beam hardning of the X-rays that use of small or microfocal spot will turn to be useful. The Sn-Mo composite filter, studied in the 1st report, will provide higher image contrast than a single Mo filter at higher tube voltage over 40kVp.

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Panoramic radiography (curved rotational tomography) has proved a superior diagnostic aid in many phases of dental and medical applications, often detecting lesions not only in the oral cavity but in the "head and neck" area. Tomorex, distributed by the Pennwalt Company in U.S.A. is the apparatus that is designed to permit panoramic radiography on the horizontally oriented patient in bed, and that provides curved layer tomography of cranial or maxillofacial structures at pre-selected levels, as well as conventional panoramic projections. The purpose of the present paper is to introduse the mechanism of Tomorex including the relationship between positioning and x-ray pictures, to describe the result in the clinical application.

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Minicomputers are now being applied to computerized radiation machine control. Using these in-house minicomputer and a mark card to paper tape converter, we could assemble a working information retrieval system for computed tomographic examination of the Brain configured to our studies.

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