Whole-body motion correction in cardiac PET/CT using Positron Emission Tracking: A phantom validation study

A whole-body motion correction algorithm that is based on positron emission tracking (PeTrack) of fiducial markers has been validated using phantom studies in PET/CT. Patient motion during medical imaging procedures is an inevitable source of artifact and image quality reduction. A motion correction algorithm has been designed to reduce the adverse effects of misalignment artifacts between the CT attenuation map and PET data as well as reduction of spatial resolution associated with motion blurring. A phantom with a left-ventricular cardiac insert was imaged for 5 minutes in list-mode format on a GE Discovery 690 PET/CT scanner. Four acquisitions were completed in total: one without motion and three with motion in the superior-inferior and lateral directions. The list-mode data were processed offline using the PeTrack algorithm to generate 3D motion traces of a 30 kBq Na-22 fiducial marker placed on the anterior surface of the phantom. Whole-body motion triggers were created when a change in marker position, relative to t = 0, exceeded a voxel length in any direction. Motion data were used to rigidly align CT and raw emission data prior to reconstruction as well as align reconstructed PET motion frames. Images with and without motion correction were compared to the static reference image to evaluate changes in apparent left-ventricular (LV) wallthicknesses, signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR). With respect to the Reference image, Non-Corrected images exhibited average increases in LV wallthickness in the range of 9-55%, SNR reductions from 31-63% and CNR reductions of 27-80%. Motion corrected images exhibited average changes in LV wall-thickness of -0.2-6%, SNR reductions of 4-10% and CNR reductions of 13-35%. The authors concluded that motion tracking data acquired using PeTrack can be incorporated into the reconstruction algorithm to correct for rigid motion and significantly reduce the degrading factors of whole-body motion in PET/CT.