Evaluating Image Registration Using NIREP

This paper describes the functionality and use of the Nonrigid Image Registration Evaluation Program (NIREP) that was developed to make qualitative and quantitative performance comparisons between one or more image registration algorithms. Registration performance is evaluated using common evaluation databases. An evaluation database consists of groups of registered medical images (e.g., one or more MRI modalities, CT, etc.) and annotations (e.g., segmentations, landmarks, contours, etc.) identified by their common image coordinate system. Prior to analysis with NIREP, each algorithm is used to generate pair-wise correspondence maps/transformations between image coordinate systems. NIREP has a highly customizable graphical user interface for displaying images, transformations, segmentations, overlays, differences between images, and differences between transformations. Evaluation statistics built into NIREP are used to compute quantitative algorithm performance reports that include region of interest overlap, intensity variance of images mapped to a reference coordinate system, inverse consistency error and transitivity error.