Imaging properties of a half-inch sodium iodide gamma camera

Because of the interest in low-cost instrumentation for imaging positron emitters and because of the low detection efficiency of conventional 3/8" NaI(Tl) gamma cameras for 511 keV photons, basic imaging characteristics have been evaluated on a SPECT system with 1/2" NaI(Tl) detectors. Intrinsic spatial resolution was measured at 70, 140, and 511 keV to be 6.3 mm, 4.3 mm, and 3.2 mm FWHM, respectively. Counting efficiency at 511 keV increased 55% over a similar 3/8" system. Other parameters relevant to collimated and coincidence imaging were evaluated, including spatial linearity, spatial resolution vs. incidence angle, and energy resolution. Performance was considered to be acceptable for conventional applications, and significantly improved for 511 keV applications.