Performance of a large-area whole-body counter

The design and performance of a cheap but sensitive whole-body counter which incorporates a large area organic scintillator in the form of a movable detector are described. The performance and sensitivity of the counter are shown to be adequate for a large number of clinical investigations using amounts of administered radioactivity well below the maximum body burdens recommended by the International Commission on Radiological Protection. An investigation of the sensitivity of the counting efficiency to the source-detector geometry has led to the adoption of a counting technique which is relatively independent of the location of a point source within the trunk region of a subject. Use of this method permits the measurement of the natural 40 K content of a standard man to 3% accuracy of counting statistics in a counting time of 1000 sec. For cheapness, a chalk shield has been used and the cost of materials for a counter based on this design, but using an efficient liquid scintillator, could be as low as £300, excluding the cost of electronic units.