A quantitative assessment of patient motion and its effect on myocardial perfusion SPECT images

Patient motion during image acquisition is a frequent cause of SPECT perfusion image artifacts. We sought to determine the relationship between patient motion and the resultant image artifact. The effect of patient motion on 201Tl SPECT scintigrams was assessed with computer simulation to create 66 new image sets with artifactual vertical, horizontal and combined patient motion introduced over a broad range in six normal studies. Visual analysis of regional radioactivity in these simulated images, as well as quantitative analysis of the resultant polar coordinate display was performed. The presence and extent of "motion" artifacts varied with the number and location of the projection images affected, as well as the extent of their displacement. Although the extent of the defect varied with the frames affected, they were not necessarily more extensive when related to vertical displacement in the center of the orbit. The location of induced defects varied with direction of displacement and the location of frames affected. Vertical and horizontal motion created additive defects. Defect size grew with incremental vertical displacement but subsequently decreased with yet increasing displacement. Both the irregular, "lumpy" distribution of radioactivity, often with opposing "defects", as well as curvilinear extraventricular radioactivity, were visual clues suggesting SPECT defects related to motion artifact. A clinical case review revealed that approximately 25% of studies demonstrate such motion during acquisition but only 5% contribute to visible image deterioration. While detection is important, postacquisition attempts to correct such artifacts are incomplete and optimally, they must be prevented.