Analysis of myocardial motion in tagged MR images using nonrigid image registration

Tagged magnetic resonance imaging (MRI) is unique in its ability to non-invasively image the motion and deformation of the heart in-vivo, but one of the fundamental reasons limiting its use in the clinical environment is the absence of automated tools to derive clinically useful information from tagged MR images. In this paper we present a novel and fully automated technique based on nonrigid image registration using multi-level free-form deformations (MFFDs) for the analysis of myocardial motion using tagged MRI. The novel aspect of our technique is its integrated nature for tag localization and deformation field reconstruction. To extract the motion field within the myocardium during systole we register a sequence of images taken during systole to a set of reference images taken at end-diastole, maximizing the mutual information between images. We use both short-axis and long-axis images of the heart to estimate the full four-dimensional motion field within the myocardium. We have validated our method using a cardiac motion simulator and we also present quantitative comparisons of cardiac motion from nine volunteers.