Coupled B-snake grids and constrained thin-plate splines for analysis of 2-D tissue deformations from tagged MRI

Abstract

Magnetic resonance imaging (MRI) is unique in its ability to noninvasively and selectively alter tissue magnetization and create tagged patterns within a deforming body such as the heart muscle. The resulting patterns define a time-varying curvilinear coordinate system on the tissue, which we track with coupled B-snake grids. B-spline bases provide local control of shape, compact representation, and parametric continuity. Efficient spline warps are proposed which warp an area in the plane such that two embedded snake grids obtained from two tagged frames are brought into registration, interpolating a dense displacement vector field. The reconstructed vector field adheres to the known displacement information at the intersections, forces corresponding snakes to be warped into one another, and for all other points in the plane, where no information is available, a C1 continuous vector field is interpolated. The implementation proposed in this paper improves on our previous variational-based implementation and generalizes warp methods to include biologically relevant contiguous open curves, in addition to standard landmark points. The methods are validated with a cardiac motion simulator, in addition to in-vivo tagging data sets.

Imaging longitudinal cardiac strain on short‐axis images using strain‐encoded MRI

“…There are many proposed methods for measuring the inplane components of myocardial strain using MR tagging (15,21,22). All require acquisition of short-axis images, sometimes a single image with grid tags and sometimes a pair of one-dimensionally tagged images.…”

Four-dimensional B-spline based motion analysis of tagged MR images: introduction andin vivovalidation

“…In the first approach of Amini et al (1998) tags were segmented using a two-dimensional coupled B-snake grid, but no parametric motion field was constructed for the material points. In that study, to get the displacement information at any other image point a thin-plate spline based finite difference method has been proposed.…”

Automatic 3D tracking of cardiac material markers using slice-following and harmonic-phase MRI

“…In comparison to existing tag-based point tracking techniques [18,20,21,23,24,34], our method provides direct and fast measurements of 3-D motion with minimal (or no) user interaction. In phase-contrast tracking techniques [3,4], the integration of the velocity data introduces high timeresolution demands to achieve a good estimation of the 3-D motion trajectory.…”