Analytical considerations of photon attenuation and system response function in SPECT reconstruction
A unified framework for image reconstruction in single-photon emission computed tomography (SPECT) is proposed for modeling of the effects of photon attenuation and of the imaging-system point-spread function (PSF). This framework provides a basis for analysis of the mathematical properties of the SPECT reconstruction problem. We introduce an average-attenuation factor that is calculated along each projection line. Under certain conditions, a one-step correction method employing this average-attenuation factor compensates completely for the effects of both photon attenuation and PSF. In addition, a new hybrid approach is proposed that uses the one-step correction method at the initial step and shifts to a modified iterative Chang's method in the subsequent iterations. We implemented both the iterative Chang's method and our hybrid method in computer simulation studies. The results demonstrate that (a) our one-step correction method significantly improves the quality of reconstructed images over those with Chang's one-step method; (b) our hybrid approach converges faster than does the iterative Chang's method and produces reconstructed images of high quality.
Key wordsSingle-photon emission computed tomography photon attenuation point-spread function average-attenuation factor unified framework hybrid approach
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