Improved spatial and temporal resolution of gated myocardial perfusion PET using post reconstruction dual respiratory and cardiac motion compensation

The current work was based on a previously developed 4D image reconstruction method for myocardial perfusion (MP) PET where dual respiratory motion (RM) and cardiac motion (CM) compensation were performed post reconstruction. We implemented and extended the work on patient data from a commercial PET system and demonstrated further image quality improvement. We divided the PET events into 6 equal-count respiratory gates based on heart center-of-mass movement estimated from the list-mode PET data. For each respiratory gate, the list-mode data was sorted and rebinned into 8 and 16 cardiac gates in addition to the conventional 8 cardiac gates. The vendor provided list-mode based time-of-flight reconstruction was used in all image reconstruction with and without the TOF information to provide high quality 3D PET images before the RM and CM compensation. For each cardiac gate, the RM vector fields (RMVF) were derived from the respiratory gated reconstructed images, and were applied to the dual gated images to obtain RM free images. The CM vector fields (CMVF) were estimated from the cardiac gated RM free images; the CM compensated image at each cardiac gate was the sum of the original image and images transformed from the other cardiac gates based on the CMVF. Dual RM and CM compensation were shown to improve spatial resolution by reducing RM blur through RM compensation and suppressing image noise through CM compensation as compared to those without CM compensation. The 16-frame cardiac gated images provided much higher temporal resolution for revealing subtle regional motion than the 8-frame cardiac gated images and showed similar noise level per frame. In conclusion, dual RM and CM compensation improves spatial resolution and allows higher number of cardiac gated frames in 4D gated MP PET with improved temporal resolution without compromise in image noise.