An investigation of the resolution characteristics of a rotating parallel hole collimator for use in a medium energy SPECT system

The rotating parallel hole collimator is designed to image data produced by medium energy isotopes. This collimator has thick septa and differs from a conventional medium energy collimator by having the ability to rotate so that data will not have shadows from the septa. With these improvements, it is possible to obtain higher resolutions. However, possible misalignments in the rotation of the collimator could cause the projection data to have degraded resolutions. Comparisons of resolutions are made between the projection data and SPECT images both with and without summing of the projections. A line source filled with 0.4-1.3 mCi of /sup 131/I was imaged on a SPECT system. The rotating hole collimator and a medium energy collimator were placed on adjacent heads of the camera. Results indicate that with proper rotation, there will be no degradation of the SPECT image from the rotating collimator. For the case of a 9 cm radius of rotation, the rotating parallel hole collimator's full width at half maximum was measured to be 5.2-5.8 mm. The conventional collimator had a full width at half maximum of 9.3-9.8 mm.