Correction of motion-induced artifacts in clinical cardiac SPECT studies using a stereo-motion-tracking system

Patient body motion is inevitable in cardiac SPECT due to the lengthy interval of time patients are imaged (∼23 min with transmission scan) and even respiratory patterns can change over that period. The use of external tracking devices provides additional information which is expected to result in a more robust correction than using just the emission data. We have been investigating the use of stereo-motion-tracking of retro-reflective markers on stretchy bands wrapped about the chest and abdomen of patients to provide 6 degree-of-freedom (DOF) tracking of the patient during cardiac SPECT. Recently we have introduced a visual-tracking-system (VTS) which utilizes 5 near-infrared (NIR) cameras to track markers from both ends of the clinic. This system is robust enough to compensate for multiple cameras being blocked from viewing all the markers due to the patient anatomy or viewing geometry restrictions imposed by the SPECT system. Initial studies have shown that the temporal and spatial accuracy of this motion-tracking system are well within the precision needed to correct for motion artifacts that can occur during cardiac SPECT. Clinical trials have been initiated for list-mode cardiac SPECT studies using bands of markers on the chest and abdomen, and so far we have been able to consistently track the markers. We have begun volunteer studies with IRB approval and informed consent where patients were asked to stay for a second cardiac-rest study with no additional radioactivity. Patients were asked to perform specific movements and we were able to correct for the rigid-body motion during SPECT reconstruction with our software as well as the standard clinical tool for comparison.