Comparison and Analysis of the Parameters of Clinical Whole-Body Spectrometers

The paper compares the parameters of four types of clinical whole-body spectrometers (eight-crystal spectrometer - four crystals above and four crystals under the patient; two-crystal spectrometer with linear scanning geometry; two-crystal spectrometer with spiral scanning geometry and with a possible termination and without any termination of the forward probe movement at the ends of the phantom) from the point of view of two basic characteristics required of such spectrometers: (1) The spectrometer should have uniform spatial sensitivity, i.e. pulse counts should be independent of isotope localization in the organism; (2) It should have maximum sensitivity relative to the number of detectors required for meeting the first requirement. An M-20 computer was used for calculating the efficiency of counting the primary gamma radiation from isotropic point sources of 125I, 141Ce, 51Cr, 131I, 137Cs, 60Co, and 40K placed at 13 points of each of the 18 sections (every 10 cm) of a water-filled elliptical cylinder 180 cm in length and with 36 cm and 20 cm axes, for the four above-mentioned measurement geometries. Results were obtained for different measurement geometries. The calculations were verified experimentally by an eight-crystal spectrometer.From an analysis of the results, the optimum measurement geometry for the four types of spectrometers was determined. It is shown that the uniformity of spatial sensitivity can be considerably improved if the entire spectrum of gamma radiation from the phantom is recorded. (author)