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±0.02m is found to provide a good compromise for acceptable sensitivity and reasonable counting efficiency. •Energy spectrum of a point source is acquired using a rectangular detector, at different scattering medium thicknesses.•The scatter fraction, solid angle, extrinsic sensitivity and counting efficiency are calculated.•A comparison of measurements with a flood source case is provided.•An optimum source-to-detector distance is suggested for acceptable sensitivity and counting efficiency.