Simultaneous reconstruction of emission activity and attenuation coefficient distribution from TOF data, acquired with rotating external line source

The simultaneous PET data reconstruction of emission activity and attenuation coefficient distribution is under investigation, where the attenuation image is constrained by exploiting an external transmission source. Data are acquired in TOF mode, allowing in principle for separation of emission and transmission data. Nevertheless, here all data are reconstructed at once, eliminating the need to trace the position of the transmission source in sinogram space. Contamination of emission data by the transmission source and vice versa is naturally modeled. Attenuated emission activity data also provide additional information about object attenuation coefficient values. The algorithm alternates between attenuation and emission activity image updates. We also proposed a method of estimation of spatial scatter distribution from the transmission source by incorporating knowledge about the expected range of attenuation map values. The reconstruction of experimental data from the mCT scanner suggests that simultaneous reconstruction improves attenuation map image quality, as compared to when data are separated. On the other hand, the use of transmission data stabilizes attenuation coefficient distribution reconstruction from TOF emission data alone.