A new system of radiation protection for angiographers was developed and its effect evaluated. The system consists of two components for radiation protection : one to protect the abdominal area and the other to protect the head and neck area. The first is composed of a lead curtain attached beneath the tissue table and a movable lead barrier next to the patient's trunk. The second is brim-shaped leaded rubber attached to the image intensifier. In abdominal angiography, the radiation protection system reduced X-ray scatter to 1% of the non-protective condition for the angiographer's abdominal area and to 50% for the head and neck area. This new system reduced X-ray scatter from the patient and enhanced the safety of the angiographer.

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^99mTc-Hexakis-2-Methoxy Isobutyl Isonitrile(MIBI)redistribution and washout in myocardium were studied in 28 patients with angina pectories(AP group)and 18 patients with myocardial infarctions(MI group). Single photon emission computed tomography(SPECT)was carried out 1 hour and 3 hour after the injection of 600MBq(10MBq/kg)of MIBI at rest. SPECT images were divided into 12 segments and quantitative analyzed by normalized washout rate(NWR). NWR=(RWR-mWR)/σ……(1) RWR : regional washout rate, mWR : mean washout rate, σ : standard deviation NWR<-1 indicates redistribution, NWR>1 indicates washout Segment analysis=(NS/TNS)×100(%)……(2) NS : Number of segments with NWR<-1 or NWR>1, TNS : Total number of segments Patient's analysis=(NP/TNP)×100(%)……(3) NP : Number of patients having segments with NWR<-1 or NWR>1, TNP : Total number of patients In the AP group, MIBI redistribution was observed at a higher frequency than in the MI group. (segment analysis=10.4% in the AP group, 5.5% in the MI group. patient's analysis=79% in the AP group, 56% in the MI group.) In the MI group, MIBI washout was observed higher frequency than the AP group. (segment analysis=10.2% in the MI group, 8.0% in the AP group. patient's analysis=89% in the MI group, 71% in the AP group.) These data showed MIBI redistribution and washout in myocardium may reflect myocardial risk for ischemia.

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Three-dimensional CT angiography(3D-CTA)of the cerebral vascular region is highly evaluated among radiologists and physicians. Due to the introduction of helical CT scanners, 3D-CTA is now widely used for the accurate examination of cerebral aneurysms. The shape reappearance of vessels depends greatly on the contrast enhancement technique, the effect of contrast enhancement on the patients, and the scanning technique. To determine how these factors affect the shape reappearance of vessels, experiments were carried out using a hand-made phantom that was similar to an actual human head. The results showed that better shape reappearance of the cerebral vascular region could be obtained through the following scan and contrast enhancement techniques : higher CT value of blood vessels and lower image noise, as far as possible.

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The relationship between gantry angle and the interval length of the scanning plane in computed tomography(CT)was studied with a simple geometrical calculation and the evaluation of clinical images obtained with a human phantom. The change in patient dose was also evaluated under various conditions of gantry angle. When the same table feeding distance was used, it was theoretically and experimentally demonstrated that the interval length of the scanning plane was significantly decreased as the gantry angle increased(e.g.about 10% at twenty-five degrees). Integrated patient dose during the sequence could be changed by various combinations of gantry angle and table feeding distance, and was decreased by setting an optimal interval length of scanning plane according to the gantry angle. We concluded that gantry angle had obvious effects on the interval length of the scanning plane and patient dose, and the new method of increasing the table feeding distance according to the gantry angle might be useful for the improvement of image reproduction and the reduction of patient dose.

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Lead power and oxygenated lead are widely used as materials in conventional protective aprons. However, the use of lead alone limits weight reduction in an apron. Because the amount of lead can not be decreased without reducing X-ray absorption rate. In this study, we report the efficiency of a new X-ray protective apron with a composite protective sheet. The X-ray absorption rate of the composite sheet was 4.5 percent less than that of the lead sheet. However, the effective protective efficiency of the composite sheet was the same as that of the lead sheet. The uniformity of the new X-ray protective apron was good, and the differences among products were small. The new X-ray protective apron was about 30 percent lighter than a lead apron with a 0.25mm lead equivalent. The new lighter aprons are more comfortable for the radiology staff. Therefore, the use of a composite protective apron provides the advantages of weight reduction and increased comfort without reducing X-ray absorption rate.

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