Implementation and preliminary investigation of analytical methods for correction of distance-dependent resolution variation and uniform attenuation in 3D brain SPECT

Spatial resolution variation as a function of distance from collimator surface in single photon emission computed tomography (SPECT) is a major obstacle for quantitative imaging. This work investigated two analytical inversion methods for correcting the distance-dependent resolution variation, as well as uniform attenuation in brain SPECT studies. The first one utilizes an accurately measured resolution variation kernel, but derives an approximated inversion formula. The second one derives an accurate inversion formula, but approximates the resolution variation kernel. Reconstructed images using the first method showed a better resolution recovery at the periphery of field-of-view (FOV), consistent with the theory that the inversion formula is approximated for far-field regions. The second method restored resolution better at the central area of FOV, consistent with the approach that the resolution kernel is approximated for near-field regions. The second method is more sensitive to the approximation. The first one is more robust to the approximation and, therefore, can be a better choice for quantitative SPECT imaging.