5111820 System and method for magnetic resonance imaging of 3-dimensional heart wall motion with spatial modulation of magnetization

Abstract

Spatial Modulation of Magnetization (SPAMM) with two sets of tagging planes orthogonal to the image plane is used in accordance with known techniques to image two-dimensional heart wall motion with MRI. However, such techniques are modified in accordance with the invention to permit direct assessment of three-dimensional heart wall motion from two-dimensional images using a three-dimensional SPAMM technique and a phase shift SPAMM technique. The three-dimensional SPAMM technique uses a third set of tagging planes oblique to the image plane to separate within-plane motion from through-plane motion. In accordance with the 3-dimensional SPAMM technique, the displacement of the oblique magnetization lines relative to the displacement of the spatial modulation pattern in the imaging plane during a preimaging time interval is indicative of the displacement of a body portion such as a patient's heart wall through the imaging plane during the preimaging time interval. Preferably, the oblique angle is 45° so that the amount of stripe displacement is equal to the amount of through-plane-motion. On the other hand, the phase-shift SPAMM technique encodes through-plane velocity as a corresponding phase shift. An integral may then be taken of the resulting phase-sensitized images in order to determine the through-plane displacement corresponding to the phase shift. Both techniques in accordance with the invention allow three-dimensional images of internal body tissues such as the heart wall to be imaged with minimal image acquisition and interpolation time.