Tagged magnetic resonance (MR) imaging is used to modulate the brightness patterns of heart tissues by selectively, and temporarily, modifying their magnetization properties. As the heart beats, these tag patterns distort with the deformation of the underlying tissues, and an MR image sequence can be acquired to reveal the time evolution of tag pattern deformation. These image sequences can be analyzed according to the principles of phase-based optical flow, and motion parameters such as displacement and strain can be automatically calculated. This overall process, called harmonic phase (HARP) MR imaging, is being developed by members of the center. HARP has been used to improve imaging speed on an MR scanner as well as to calculate novel diagnostic parameters. The image sequence depicted shows the circumferential Eulerian strain within the left ventricle of a normal human heart. The blue color indicates shortening of the myocardium in the circumferential direction, a sign of a healthy heart during the systolic phase. This methodology is being further developed for real-time application in cardiac stress testing, for analysis of three-dimensional motion in heart failure patients, and for imaging the motion of the tongue during speech and swallowing.