A new nonrigid registration approach for motion correction of cardiac first-pass perfusion MRI
Accurate registration of cardiac first-pass magnetic resonance imaging (FP-MRI) is fundamental for precise analysis of myocardial perfusion. In this paper, we introduce and validate a new framework for accurate registration of the segmented left ventricle (LV) wall on cardiac FP-MRI. Due to the continuous physiological motion of the heart that causes the LV wall to change shape significantly and to move within and through the image plane, we developed a new methodology for 2D FP-MRI nonrigid registration that includes: (i) global target-to-reference frame-to-frame alignment based on the maximization of the normalized mutual information (NMI); (ii) local alignment based on using a B-splines transformation model that maximizes a similarity function that accounts for 1st- and 2nd-order NMI between the globally aligned frames followed by (iii) a refinement step that is based on deforming each pixel of the target wall over evolving closed equi-spaced contours (iso-contours) to closely match the reference wall. Respective iso-contours in both reference and target frames are matched based on solving the Laplace equation. We have tested our framework on both synthetic phantoms and 20 in-vivo data sets that have been collected from patients with ischemic damage from heart attacks, who are undergoing a novel myoregeneration therapy.