Japanese Journal of Radiological Technology

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Recent progress in radiopharmaceuticals have developed many useful ^99mTc labeled compounds. To minimize body irradiation through the labeling procedures and to produce uniform compounds, development of instant labeling kit is quite desirable. Various factors concerning with development of ^99mTc albumin kit have been investigated. Besides ^99mTc albumin, the labeled compound might contain free pertechnetate and colloidal components. The quality of the material was checked by Sephadex gel filtration and paper chromatography. Finally established procedures were as follows : into 50mg albumin solution 0.05 mg ofacidic stannous chloride was added, pH was adjusted to 2.5〜3.0,after 15 min. pH was brought back to neutral, passed through 0.22μ Millipor filter, then gassed by nitrogen before and after lyophilization, stoppered and kept refrigerated until use. When needed, labeling was effectively completed within 2 min. of mixing with ^99mTc pertechnetate. Using 1mg of tin, more than 33mg of albumin was found necessary to minimize contamination of colloid and pertechnetate. Against 50mg of albumin, increasing amount of tin resulted in increasing formation of colloid, and labeling efficiencies of higher than 90% could be achived by 0.05mg of stannous chloride. As to the duration of storage, gassation and lyophilization were found important. Freezed samples without gassation were not good enough after 1 week and gassed and freezed samples were useful for 2 weeks, but gassed and lyophilized samples provided excellent products even after 9 weeks.

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In recent years, thermoluminescent dosimeter has been studied as the medical dosimetry. Especially it has become to be used widely for personal monitoring. Though there are so many reports about TLD in our conutry, almost all of them are concerned with LiF. This study was tried to detect some fundamental characteristics of Mg_2SiO_4 : Tb and MgB_4O_7 : Tb. The results indicated the followings. 1. Directional dependency of Mg_2SiO_4 : Tb was not observed for 15 MV and 200 kVp X-rays in water, and was negligible for 200 kVp X-rays in air, but for diagnostic X-rays it was about 50% in air. 2. The fading of Mg_2SiO_4 : Tb in the room temperature was not observed at least within 13 days after irradiations. 3. The average of Coefficinet of Variation (CV) of thirty Mg_2SiO_4 : Tb rods, when irradiated in the range of 16.7 mR to 71.45R was nearly 5%. While MgB_4O_7 : Tb, when irradiated in the range of 7.5R to 1,294.5 R was nearly 16%. As a result, it was concluded that MgB_4O_7 : Tb is not so reliable as dosimeter.

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To examine the reduction of X-rays scattered from the patient's body, a single absorption plate (thin metal) was put on the film. This method was useful when the X-ray grid method or Groedel method was not subjected. The X-ray energy measured no front of the film by spectrometry showed that scattered X-rays were more absorbed in the lower energy component. This result can be shown in table 1. Using the copper plate of 0.1mm or more thick the result was more effective. The exposure dose of 60〜65 kV X-rays required in this method will be equal to that of the X-ray grid of the ratio 5.

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Our assessments of medical X-ray dose and of radiologic practice in Hiroshima and Nagasaki revealed numerous deficiencies in radiologic procedures which, if eradicated, would greatly reduce doses to patients and their examiners. The urgent reasons for improving these areas are stressed, for example, by results of recent laboratory investigations and by the late effects resulting from exposure to the ionizing radiation of the atomic bombs. Some of these studies indicate that radiation effects can be anticipated from much lower doses than was previously thought. Guidelines and cautionary measures by which doses to patients and their examiners can be effectively reduced are cited.

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