Optimized collimator designs for small animal SPECT imaging with a compact gamma camera

The aim of this study to design optimized pinhole and parallel-hole collimators for the development of a high-resolution microSPECT system using a compact pixelleted scintillation detector. The detector has a field-of-view of 11 cm with pixellated crystal elements of 1.0 mm pixel size and 1.12 mm pixel pitch. The relative resolution and sensitivity advantages of pinhole and parallel-hole collimators for mice and rats imaging were investigated using analytic formulations and Monte Carlo simulations. The optimized collimator designs were obtained by maximizing the system detection efficiency for a given object resolution. The collimator designs were optimized for 140 keV incident gamma photons. Our results indicate that this small field-of-view compact detector fitted with a conventional high-resolution parallel-hole collimator with 4 cm hole-length and 1.2 mm hex hole-size could not provide better than 2 mm resolution for mice and rats imaging. However, a pinhole collimator with 10 cm focal length and 1.0 mm aperture size with keel-edge design of 0.5 mm channel-height can provide the desired resolutions for imaging mice and rats. The relative efficiency is about 2 times higher than that of the parallel-hole collimator for imaging mice at the distance of 3 cm from the collimator. In conclusion, pinhole collimator is superior to parallel-hole collimator and requires sophisticated optimal designs with high-resolution compact gamma camera for small animal imaging.