Compensation for Rigid-Body Patient Motion During Reconstruction and Respiratory Motion Post-Reconstruction in Phase-Binned Slices

In SPECT and PET, methods have been developed to track respiratory and patient motion. By acquiring list-mode emission data in synchrony with motion tracking, each type of motion can be corrected. The list-mode events can be binned into respiratory-gated projections by their relative temporal positions within the respiratory cycle. This is called phase-binning. Rigid-body motion can then be corrected during reconstruction using 3D Gaussian interpolation in the projector and backprojector. Finally, registration can be used to combine the phase-binned slices. To evaluate this approach for cardiac SPECT perfusion imaging, a SPECT list-mode acquisition a Tc-99m filled anthropomorphic phantom was performed in synchrony with motion tracking of the phantom using a Polaris IR motion tracking system. The phantom was placed on a board and manually moved with a cyclic axial motion of about 2 cm amplitude, and with additional rigid-body steps of ~2 cm followed by 4 cm during SPECT acquisition. An additional SPECT acquisition was performed with the phantom stationary for comparison. Images were obtained for the 4 cases: no motion; motion-present, no correction of the motion; motion-present, correction of the patient motion only; and motion-present, correction of both respiratory and patient motion. Results show that correction of both respiratory and patient motion greatly reduced artifact.