Introduction of a Well-type germanium/lithium semiconductor detector in nuclear medicine

Abstract

Semi-in-vivo diagnostic procedures in nuclear medicine are commonly carried out using conventional scintillation detectors. Modern semiconductor detectors have rarely been applied in this field until now. A particular example of this group is the Well-type germanium/lithium detector, a semiconductor detector which combines a high energy resolution with a high efficiency for gamma-radiation. The latter, combined with an excellent signal-to-background ratio, allows accurate detection of even very low activities. Patient doses can therefore be reduced considerably, as was demonstrated in erythrocyte survival studies, platelet survival studies and the Schilling test. The effective dose equivalent associated with erythrocyte survival studies, using the recommended 51Cr method, could be reduced from 780 to 2 μSv. The effective dose equivalent in platelet survival studies, using the recommended 111In method, could be reduced from 1400 to 14 μSv. For both procedures, the reliability was demonstrated by the results obtained with healthy controls. In the Schilling test, using 57Co, the effective dose equivalent could be reduced from 54 to 9 μSv. In addition, the high resolution of Ge-detectors enables selective and accurate determination of individual components in mixtures of isotopes. Therefore, with such detectors, low-level double-labeling procedures can be introduced in semi-in-vivo nuclear medicine, thus creating the possibility of studying certain unanswered but clinically relevant questions.