Room-temperature semiconductor detectors for in vivo monitoring of internal contamination

In vivo monitoring of low-energy X- and γ-ray emitters has always been a difficult task, primarily because of lack of accuracy and the high detection limits of classical techniques. Various types of PIN diodes (diodes with a large intrinsic zone) were tested in the Radiation Protection Department of the Studie Centrum voor Kernenergie, Centre d'etude de l'Energie Nucleaire (Mol, Belgium) in the measurement of radioactive body burden by direct methods. Current research is oriented toward the use of room-temperature diodes for the detection of low-energy photons escaping the body. In this paper, a new counting technique that involves a portable jacket containing the diodes is described. The system uses silicon diodes and is used out of a shielding room in order to be near the contamination. With this method rapid analysis and long counting times are possible, stress is reduced, and medical treatment can be optimized. CdZnTe detectors were also evaluated for this measurement technique but this type of detector is better adapted for counting inside a shielding room. The improvement of the accuracy of the measurement, taking into account the effect of the ribs, is described here, as well as the associated electronics necessary for this type of counting.