A new approach in patient motion correction for cardiac SPECT: A simulation study

Patient motion artifacts created in cardiac SPECT imaging can lead to misinterpretation of the images, resulting in false diagnoses. This simulation study proposes a new technique for patient motion correction (MC), where we utilize a modified template projection/reconstruction (TPR) algorithm to perform a voxel-by-voxel correction to the original image. Using NCAT, we developed two female phantoms with large breasts containing a non-beating heart (heart: background = 5:1). Phantom 1 had a healthy heart, and phantom 2 had a heart with a small (10%) perfusion defect in the lateral wall (severity = 50%). The SimSET code was used to perform simulations for both phantoms modeling cardiac SPECT acquisitions with Tc-99m, 128 × 128 matrix, and 60 camera stops. In addition to two standard (no motion) acquisitions (ST) for each phantom, seven acquisitions with different degrees of phantom motion were created by manually shifting a selected number of projections in a given direction (motion ranged from 8 to 22 mm). MC images (MCI) were created using a modified TPR, where the projected template was adjusted to match the motion detected in the experimental projections by aligning the center of mass in each projection. All reconstructions were performed using OSEM with resolution recovery and attenuation correction. For all simulated movements, the MCI images exhibited improvements in both standard deviation (SD) and mean accuracy relative to the uncorrected experimental reconstructions (ER). On average, the accuracies calculated for ER, MCI and the ST reconstructions were 68%, 77%, and 76%, respectively. The average SD for ER, MCI and the ST reconstructions were 5.2, 4.0, and 4.0, respectively. Our proposed technique offers a voxel-by-voxel motion correction, which provides improved image accuracy and standard deviation of counts relative to the uncorrected images and, in many cases, the images created without patient motion.