Angle images for measuring heart motion from tagged MRI

This paper introduces a new image processing technique for rapid analysis and visualization of tagged cardiac magnetic resonance (MR) images. The method is based on the use of isolated spectral peaks in SPAMM-tagged magnetic resonance images. The authors call the phase of an image corresponding to just one of these peaks an angle image, and show that except for a phase-wrapping artifact, an angle image is linearly related to a component of the three-dimensional motion. Using one or more angle images, the authors show how to synthesize conventional tag lines, reconstruct displacement fields for small motions, calculate the optical flow between successive temporal images, and calculate two-dimensional strain. The authors demonstrate the performance of this approach on both real and simulated tagged MR images.