Abstract 2783: Myocardial Perfusion SPECT with CT Attenuation Correction: Role of Misregistration and Value of Reregistration
Objective: The accuracy of myocardial perfusion SPECT imaging is improved with attenuation correction (AC). Algorithms using X-ray from a hybrid SPECT/CT system have the potential for misregistration (MR) of emission and transmission scans because CT and SPECT are obtained sequentially. This MR can change regional radiotracer distribution and may reduce diagnostic accuracy. Therefore software tools for re-registration based on visual alignment of SPECT/CT fusion images have been developed. Our objective was to determine the role of misregistration and the performance of re-registration in cardiac SPECT/CT.
Methods: We included 105 patients who underwent clinical myocardial perfusion imaging on a hybrid SPECT/CT system. Images were quantitatively assessed for MR using fusion software. Results in mm were recorded in the x, y, and z axis. Regional tracer uptake in 6 segments (anterior, septal, inferior, lateral, anteroapical and inferoapical) for non-corrected (NC) and attenuation corrected images before (AC) and after reregistration (RR) was obtained from polar maps. To determine the relative influence of MR, individual differences between NC and AC as well as AC and RR images were correlated with MR in a multivariate analysis based on a mixed effects model including additional clinical variables such as gender and body weight.
Results: There was a significant difference between regional radiotracer uptake between NC and AC in all six segments, most pronounced in the inferior wall. On multivariate analysis, MR was a significant contributor to changes in radiotracer distribution in the anterior (p=0.038), septal (p=0.011), and inferior segments (p=0.006). The mean MR was 8.6 ± 3.6 mm. Reregistration of misalignment had a significant impact on regional radiotracer distribution in the segments shown to be influenced by MR.
Conclusion: When using a hybrid SPECT/CT system, MR may occur and influences regional tracer distribution in AC images. Reregistration of misaligned studies may be a useful tool for correction. The impact of this strategy on diagnostic and prognostic accuracy of hybrid imaging needs to be determined in future trials.