Effect on lesion detectability of proximity to anatomical boundaries in emission tomography

In emission tomography (ET) comprising PET and SPECT, anatomical information derived from intra-patient coregistered CT or MR scans can be incorporated into the ET reconstruction. The increasing availability of PET-CT and SPECT-CT has engendered renewed interest in anatomical priors. Our interest is in exploring the efficacy of such side information for lesion detectability. In simulation studies we used an idealized model of anatomical side information incorporated into a SPECT MAP (maximum a posteriori) reconstruction, and a channelized Hotelling observer (CHO) whose performance emulates that of humans in such detection tasks. We observed that detectability appears to vary little with or without anatomical side information unless the lesion is tightly constrained by anatomical boundaries. Our preliminary studies thus imply a limited utility for anatomical side information for this task.