“…Correlation-based tracking has been proposed [13], [32], [33], [31], [42], but has been limited by the lack of sensitivity to poor texturization. B-spline polynomial fitting [18], homography transformation [2], and radial basis functions [36], [38]- [40], [35] have been shown to be effective in capturing the low-order deformations of a small region of the beating heart at real-time speeds (50 Hz); however, higher order-deformation tracking using these methods becomes nontrivial and computationally expensive.…”