Use of a personal computer to measure gamma camera spatial resolution.

Abstract

The intrinsic spatial resolution of a gamma camera is specified by the full width at half maximum (FWHM) of the line spread function (LSF), in the absence of a collimator, and is an important indicator of system performance. The standard method of determining the spatial resolution is to place a suitably collimated line source against the crystal face and to examine the amplitude spectrum from the camera. For a modern gamma camera with a field of view of 375 mm, the expected FWHM may be 4 mm; to measure this accurately would require a sampling frequency of 0.4 mm. Most nuclear medicine computers are able to acquire data with a maximum resolution of 256×256 pixels per frame, corresponding to a sampling frequency of about 1.5 mm, which is too coarse for measurement of the LSF. A low-cost 1024-channel multichannel analyser (MCA) for γ-ray spectrometry, interfaced to a personal computer, can be adapted to measure the LSF of the camera and calculate the FWHM with sufficient accuracy (sampling frequency better than 0.4 mm). The equipment to be described has been used on three gamma cameras in routine use.