Demonstration of motion correction for PET-MR with PVA cryogel phantoms

Respiratory motion can degrade PET image quality and various correction approaches have been investigated. A novel method, applicable to simultaneous PET-MR is to measure the motion with the MR and correct the PET data with the known motion fields. This study investigates the effectiveness of motion correction for PET-MR acquisition with phantom studies. It incorporates the improved motion estimation or a simultaneously acquired MR with the realism of a respiratory driven motion and the deformability of the PVA cryogel phantom. PVA cryogel has been used for motion modeling because of its elastic properties. Motion is transferred with a hydraulic system to the MR room, inside the PET insert. The MR-compatible PET insert uses silicon photomultiplier photodetectors and acquisition is capable of being synchronized with the MRI. Spatial registration between PET and MR is essential for accurate motion correction using MRI derived motion fields. We have performed simultaneous PET and MR acquisition of a non-rigid continuously deformable phantom PET and MR visible phantom. Calibration procedures were used to ensure that PET and MR acquisitions were accurately aligned both spatially and temporally. The final step of this study is the motion correction by using known techniques such as Motion Compensated Image Reconstruction (MCIR) and Reconstruct-Transform-Average (RTA). We have demonstrated that the temporally and spatially correlated PET and MR datasels can be used to motion correct the PET acquisition.