Temporal regularization in fully 5D reconstruction of cardiac gated dynamic SPECT images

Recently we developed two image reconstruction approaches aimed to unify gated imaging and dynamic imaging in nuclear cardiac imaging, the goal being to obtain an image sequence from a single acquisition which shows both cardiac motion and tracer distribution change over the course of imaging. While both approaches exploit the similarity among the different cardiac gate intervals, they differ in the form of temporal regularization imposed during reconstruction. In this work, we provide a quantitative comparison of these two approaches in terms of reconstruction accuracy of the myocardium using several quantitative measures, including signal-to-noise ratio, time activity curves, and ability for perfusion defect detection. In our experiments, we simulated gated cardiac imaging with the NURBS-based cardiac-torso phantom and Tc99m-Teboroxime as the imaging agent. The results show that both approaches could yield similar overall accuracy in the myocardium, and the B-spline approach could achieve slightly better estimation of the time activities compared to the dynamic EM approach.