Abstract
The prompt gamma-ray analysis of 14 biologically interesting elements was performed using a relatively weak reactor neutron flux 3 x 104 n.cm-2.s-1. Sample irradiations were performed in air and in a water phantom, to obtain sensitivity limits of the elements prior to possible use in in-vivo neutron activation analysis. A comparison was performed between prompt gamma-ray measurement by a Nal(Tl) and Ge(Li) detector, and also between high and low-energy regions. Only Cd, Cl and Hg samples yielded minimum detection limits less than 100mg for irradiations in air, and only Cd remained in this category following irradiation in the water phantom. Preliminary studies were performed of irradiated sample depth measurement, in the water phantom, in order to provide a tissue attenuation correction factor. A comparison was made between the double gamma-ray and scatter-to-peak (SPR) depth measurement techniques. A formula was developed for a point source measured by a parallel collimated gamma-camera and minicomputer system, which describes the variation of SPR with depth in a scattering medium. The particular measurement system described permits the utilization of data which is normally rejected in the course of quantitative scintigraphy, hence a tissue attenuation may be obtained without additional patient scanning. The validity of the SPR formula was tested experimentally using a 198Au source in a water phantom, and a good agreement was found. Clinical trials were performed with patients undergoing 197HgCl2 renal uptake measurements. The effect of kidney thickness was measured by the use of 197Hg volume sources. A good correlation was obtained between the SPR method and the routine, statistical formula method, of kidney depth measurement, for 13 subjects.