Evaluation of rigid body motion compensation in cardiac perfusion SPECT employing polar map quantification

Rigid body motion tracking, estimation and compensation in cardiac perfusion SPECT have recently been developed and tested in our laboratory. The objective of this study was to proceed with the evaluation in patients of the effectiveness of rigid body motion compensation. Patient volunteers (n=50, with an average age and body mass index of 60 and 33 respectively) with written consent were asked to execute some predefined body motion during an additional second stress perfusion acquisition. Acquisitions were done on a BrightView gamma camera equipped with a low dose cone beam CT (Philips, Cleveland, OH) using the standard clinical protocol with 64 projections acquired through 180 degrees, the two heads in 90-degree configuration stepping 2.81 degrees between projections. All data were reconstructed with an ordered subsets expectation maximization (OSEM) algorithm incorporating a 3-dimensional Gaussian rotator using 4 projections per subset and 5 iterations. During reconstruction, all physical degradation factors were addressed (attenuation, scatter, and distance dependent resolution). Second stress acquisitions were reconstructed with and without motion compensation, while the clinical stress was only reconstructed with motion compensation and used as baseline. Polar map quantification was employed to evaluate compensation techniques. Results indicate that rigid body motion compensation was successfully applied in a large number of the patients evaluated, however technical and practical difficulties lead to failure in some.