Do template-based partial volume effect corrections inherently presume homogeneous uptakes?

The application of the template-based correction for partial volume effect (PVE) may be challenging in clinical situations where a non-homogeneous region of interest (ROI) is surrounded by a non-homogeneous background. In this paper, we examine the performance of our iterative PVE correction (itPVEC) under such circumstances. We simulated a number of oncology SPECT scans where four tumour-like targets were adjacent to the tissues with different activity concentrations. We considered three types of activity distributions inside ROIs (1) the cone-shaped non-uniformity where an inner elliptical core had higher concentration than the outer shell; (2) the concave-shaped non-uniformity where an inner elliptical core had lower concentration than the outer shell; (3) locally uniform distribution where the target was composed of two parts with different but uniform activity concentrations. We simulated a typical oncology SPECT scan with an acquisition matrix of 128 × 128 × 128 and pixel size of 4.4 mm. We assumed that the boundaries of our targets were available from the high-resolution anatomical image with a matrix 512 × 512 × 512 and voxel size of 1.1 mm. The template-based partial volume effect correction demonstrates the best performance when the true activity is uniformly distributed throughout ROI. However, this approach is worth to apply even in situations with non-uniform activity distributions (inhomogeneous tumours). Based on our analysis of the PVEC applied to three models with four different tumour-like homogeneous and inhomogeneous targets, we conclude that template-based method improves (i) total activity (errors did not exceed 6%) and (ii) distribution near tumour boundaries. Especially, it can substantially improve imaging of non-compact tumours.