The count rate performance of a multiwire gamma camera measured by a decaying source method with 9.3-minute tantalum-178.

Abstract

The multiwire gamma camera (MWGC) operates at high count rates with radionuclides of low energy and short half-life. We evaluate the count rate performance of the MWGC with tantalum-178 (178Ta) by a decaying source method. Data acquired dynamically by the camera from a 178Ta source in the NEMA Standards scatter phantom were corrected for deadtime loss by a trial paralyzing deadtime and converted to their natural logarithms. The trial deadtime, tau, was adjusted iteratively after curve fittings until a straight line was achieved. The paralyzing deadtime determined by this method was 0.41 microsecond. Therefore, the camera can be operated up to 850,000 cps with 178Ta without exceeding 50% data loss. This rate is 10 times greater than the performance of the typical scintillation camera. Moreover, high count rates are achieved without significant loss of spatial resolution.