Correction for photon attenuation in SPECT: analytical framework, average attenuation factors, and a new hybrid approach.
We provide a unified framework for the investigation of convergence properties of the iterative algorithms for photon attenuation correction in SPECT, including the iterative Chang method--a commonly used approach in which an average attenuation factor calculated over all projection angles is employed in a pointwise correction scheme. A new average attenuation factor calculated along the projection line is introduced, which can compensate exactly for the attenuation effect in the case of a uniform activity distribution. We propose a new hybrid approach in which we use this new average attenuation factor initially and then shift to the iterative Chang method in later iterations. This hybrid approach was evaluated in a simulation study by use of a computer-generated phantom with both non-uniform activity and non-uniform attenuation distributions. The results demonstrate that this hybrid approach improves the convergence speed of the iterative Chang method and produces reconstructed images of high quality.
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Frank Center for Image Analysis/FMI, Department of Radiology, University of Chicago, IL 60637.
Wong
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WH
Chen
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CT
Liu
J
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D000465:Algorithms; D007091:Image Processing, Computer-Assisted; D008961:Models, Structural; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*