Resolution of pinhole collimators used with gamma cameras

The line spread function (LSF) of an imaging system incorporating a pinhole of 0.275 cm radius and a scintillation camera has been measured and its full width at half maximum (FWHM) compared to the values predicted by an expression based on the resolution index of Anger. In most cases, the actual resolution of the system is approximately 20% superior to that predicted by the above expression. However, good agreement is observed between our measured LSFs and those computed using a frequency domain method. Based on these computed LSFs, an empirical expression relating the FWHM of the total system to pinhole and camera parameters with an accuracy of +/- 3% is presented. This expression is applicable to most pinhole imaging systems in use today.