Abstract
Abstract Chest cavity monitoring by gamma spectrometry generally utilizes detectors of 12.7, 20.3, or 22.9 cm in diameter, which are positioned according to autopsy data, chest X-rays, or the operator's estimate of lung position. In this study, Monte Carlo techniques and a computer representation of a reference human figure were used to determine optimum detector size and positioning. Escape efficiency for uncollided photons of 16–185 keV was determined for chest, back and sides of the thorax. The effect of nonuniform source positioning was also studied. Given uniform particle distribution, two detectors of 12.7-cm diameter were found to register essentially the same number of photons as one detector of 22.9-cm diameter, even though the latter has nearly 60% more surface area. The optimum detector appears to be a rectangle of approx 16 × 16 cm. If a detector is to be placed over each lung, the center of each detector is most effectively positioned approx 20 cm below the top of the shoulder and 10 cm from the midline of the sternum.
Published Version
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