Three-dimensional geometric point response correction in rotating slant-hole (RSH) SPECT

The quality and quantitative accuracy of SPECT images are degraded by effects of attenuation, scatter, noise, geometric response, septal penetration and intrinsic crystal resolution. The geometric response has a significant degrading effect on spatial resolution, and can introduce spatial distortions because it is non-stationary. In this study the authors have characterized the geometric response function for RSH collimators and implemented depth dependent correction for this effect. The GRF for RSH was found to be asymmetric and shift invariant for a given depth. An analytical model for the GRF was developed and implemented into the projector and backprojector of an iterative reconstruction algorithm. GRF compensation was applied to a cardiac phantom simulation and was found to improve the resolution. This work successfully demonstrates that iterative compensation for resolution degradation in RSH SPECT can be performed.