COUPLED B-SNAKE GRIDS AND CONSTRAINED THIN-PLATE SPLINES FOR ANALYSISOF 2-D TISSUE DEFORMATIONS FROM TAGGED MRI

Magnetic resonance imaging (MRI) is unique in its ability to noninvasi vely and selectively alter tissue magnetization and create tagged patt erns within a deforming body such as the heart muscle, The resulting p atterns define a time-varying curvilinear coordinate system on the tis sue, which we track with coupled B-snake grids, B-spline bases provide local control of shape, compact representation, and parametric contin uity, Efficient spline warps are proposed which warp an area in the pl ane such that two embedded snake grids obtained from two tagged frames are brought into registration, interpolating a dense displacement vec tor field. The reconstructed vector field adheres to the known displac ement information at the intersections, forces corresponding snakes to be warped into one another, and for all other paints in the plane, wh ere no information is available, a C-1 continuous vector field is inte rpolated, The implementation proposed in this paper in-reproves on our previous variational-based implementation and generalizes warp method s 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.