Non-invasive techniques for assessing the dynamic behavior of the human heart can be invaluable in the diagnosis of heart disease, as abnormalities in the myocardial motion sensitively reflect deficits in blood perfusion. In this paper, we discuss our approach to measurement of motion from tagged MR images.
Leon Axel developed the SPAMM technique in which a grid of intersecting planes of altered magnetization is placed within the myocardial tissue [2]. During heart contractions, the grid patterns move, allowing for visual tracking of the grid intersections over time. In this paper, we describe techniques suitable for measuring mechanical strain from SPAMM tagged MR images, methods for reconstructing a dense motion field from these images, and new indices of myocardial deformation from the reconstructed motion fields.
An alternate tagging method described by Zerhouni and co-workers applies a radial array of thin striped tags over a short axis view of the heart [8]. Again, with star-burst tags, motion of the tissue leads to deformation of the pattern, and allows for visual tracking of the tag line over time. In this paper, we describe a new B-spline snake algorithm for tracking star-burst tagged images. In constructing the energy field for spline optimization physics of MR imaging is utilized.