Comparison of Techniques for Whole-Body Counting of γ-Ray Emitting Nuclides with NaI(Tl) Detectors I: Point Sources in Phantoms

Abstract

A two-part study is presented on the efficiency and accuracy with which γ-ray emitting radionuclides in man can be assayed by various whole-body counting procedures. The comparison includes measurement geometries of three types (scan, arc, and chair); NaI(Tl) detectors of four sizes; radionuclides that are variously distributed in the body, and emit γ-rays covering a wide range of energy; spectral analysis based on counts in either the photopeak or the full pulse-height spectrum; and investigations on both phantoms and man. In this paper the experimental and theoretical methods are described and then applied to point sources of radionuclides in phantoms in order to isolate and to clarify underlying processes which collectively affect measurements on dispersed sources in man. Numerical results are given for a wide range of measurement conditions.