Potential benefits of incorporating energy information when estimating attenuation from PET data

This study explores the advantages of using a different energy window for each individual annihilation photon when estimating attenuation from scattered PET data. Several studies have shown that scattered data can be used to reconstruct the density distribution of the object, although they are limited to simple phantoms and ideal energy measurements. We have incorporated a realistic photon detection probability model into our algorithm, as well as the dependence of attenuation on photon energy. In the proposed method each detector can assign a photon to either energy window. Preliminary results on point source simulations have shown that using a different window for each annihilation photon allows to derive spatial information on both attenuation and activity distribution, and to isolate subsets of scatter angles depending on the energy window pair used. XCAT simulations demonstrated that it is possible to yield an attenuation map from scattered PET data only and that MR information can increase reconstruction accuracy. This method can also compensate for errors typically introduced from the MRAC, such as truncation artifacts.