Fourier correction for spatially variant collimator blurring in non-circular orbit SPECT

A filtering method based on the Fourier transform has been designed to improve the effective resolution of a parallel hole collimator having a given sensitivity, by compensating for the spatial variant blurring prior to reconstruction. The original algorithm of R.M. Lewitt et al. (Proc. SPIE, vol.1092, p.232-43, 1989) is generalized by extending its applicability to noncircular orbit geometry so that the geometrical deformation can be corrected at the same time as the spatial resolution is modified. This depth-dependent Fourier filtering approach is different from conventional Fourier filtering methods, which are depth-independent and assume a uniform blurring corresponding to the blurring at center of rotation. Simulated experiments on projection data from an elliptical orbit have demonstrated correction of the radial deformation in the reconstructed image caused by the noncircular orbital geometry