Geometrical parameters and scattered radiation effects on the extrinsic sensitivity and counting efficiency of a rectangular gamma camera

A point source is used to investigate the effect of water phantom thickness and source-to-detector distance (SDD) on the sensitivity and counting efficiency of a rectangular detector gamma camera. The increase in water thickness resulted in an increase in scatter fraction, a decrease in sensitivity, and counting efficiency. The increase in SDD resulted in a decrease in sensitivity and an increase in counting efficiency. An SDD of 0.79±0.02 m is found to provide a good compromise for acceptable sensitivity and reasonable counting efficiency.