Effects of MR-invisible objects and object attenuation on PET quantification in small animal PET/MR imaging

PET Attenuation Correction (AC) in small animal imaging is generally performed via transmission (TX) scans. In simultaneous PET/MR scanners, no transmission source is available, and MR-based AC (MRAC) or AC from emission data is necessary. However, MR-invisible objects such as the bed and the MR coils cannot be corrected from MR data. We quantified the effects of a Medres warming bed and a local brain coil on AC for small animal PET/MR imaging using a dedicated Inveon PET tomograph. Additionally, the effect of segmentation-based MRAC of rats in brain regions was evaluated using MR images separately acquired on a preclinical 7T MRI system.