Respiratory motion correction reduces differences between immediate and delayed SPECT myocardial perfusion images

1659 Background: Current ASNC guidelines for SPECT myocardial perfusion imaging (MPI) recommend a 30-45 minute delay between radiotracer injection and image acquisition to reduce the impact of extra-cardiac interference. During acquisition, respiratory motion contributes significantly to motion-blurring of images and can increase extra-cardiac interference. This study assessed the extent by which differences between images acquired starting 5 minutes after injection (immediate) and at ~30-45 minutes post-injection (delayed) could be reduced by data-driven respiratory motion correction (RMC). Methods: SPECT MPI studies were retrospectively evaluated and processed using data-driven RMC software for a sample of 56 patients acquired using a pinhole cardiac camera. Immediate and delayed images without (NoMC) and with RMC were assessed using standard clinical software and the presence of extracardiac uptake was noted. Normalized myocardial perfusion value differences between delayed and immediate time-points were computed for each myocardial segment, based on a 17-segment left ventricle (LV) model. Using a Wilcoxon signed-rank test, perfusion value differences for NoMC data were evaluated in both stress and rest scans, as well as differences between immediate and delayed values derived from NoMC and RMC data. Results: Extracardiac activity was observed in g 70% of SPECT MPI studies, more than 60% of which had visually apparent differences between immediate and delayed images. With NoMC, differences between immediate and delayed images were significant in five basal segments (P l 0.001) and the five apical segments (P l 0.0001). RMC significantly reduced the difference between immediate and delayed images in some of the segments. For stress scans, significant decreases were noted in the mid anteroseptal (P l 0.001), apical lateral (P l 0.0001), and apex segments (P l 0.0001). For rest, there were significant decreases in the apical lateral (P =0.0004) and apical septal segments (P = 0.0001). Conclusions: A substantial number of SPECT MPI studies present with extracardiac activity which is often markedly reduced in delayed images compared to immediate images. In NoMC SPECT imaging, discrepancies between immediate and delayed image data are most significant in basal and apical segments. Current results demonstrate that RMC can reduce the change in measured myocardial uptake between immediate and delayed imaging in most apical segments.