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

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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 4 1/2 tons, installation within the hospital has been possible and the equipment is now routine use for clinical measurement of uptake of Co58 and Fe59. The ''traverse count'', obtained as the couch drives between the detectors, varied by not more than [plus or minus] 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 fecal activity. The average ratio obtained was 1. 01 [plus or minus] 0. 12.