A Whole-Body Counter for Clinical Measurements Utilizing the `Shadow Shield' Technique

Abstract

Two 4 in. sodium iodide crystals are mounted one above and the other below a motorized couch. The detectors view a field 20 in. across and either 6 or 12 in. along the couch, further lead protection being provided to eliminate direct background radiation. As the total weight is only 4½ tons, installation within the hospital has been possible and the equipment is now in routine use for clinical measurement of uptake of 58Co and 59Fe. The ` traverse count ', obtained as the couch drives between the detectors, varied by not more than ±8% with position of a small source in a body phantom, and by not more than 3% with variation of distribution of activity in any one patient. Good agreement has been demonstrated between percentage retention derived from whole-body counts and from measurement of faecal activity. The average ratio obtained was 1·01±0·12.