Limitations of the use of the geometric mean to obtain depth independence in scanning and whole body counting

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Abstract
Discusses making measurements of the activity in an organ more accurately by using detectors on opposed sides of the body. Any dependence of counting rate upon source position arising from geometrical considerations is then minimized. Although effects of attenuation variations are also reduced, they are not eliminated if the response of the two detectors is simply added. The authors found that the geometric mean gave greater independence of count rate with depth than the arithmetic mean in profile scanning, where sensitivity varies inversely as the distance of the source from the detector. This finding held for small sources over a wide range of energy, and also for different sizes sources at one particular energy.