Compensation for nonstationary detector response in analytical varying focal-length fan-beam SPECT reconstruction

In this study, a nonstationary filtering technique was developed to compensate for spatially variant detector response in varying focal-length fan-beam (VFF) collimated SPECT. First a collimator coordinate system was introduced in order to derive the geometric transfer function and the frequency-distance relation for the VFF collimator from its parallel-beam and fan-beam counterparts, and then the Fourier transform of the detector response was computed and used to construct a Wiener filter. The filter was applied to the blurred projection data before image reconstruction. Experimental results demonstrated improved resolution in reconstructed images after nonstationary filtering.