The image above is a graphic representation taken from actual magnetic resonance image (MRI) acquisitions of the left ventricle of a heart.
The entire sequence is available in MPEG format (99k). (For those truly brave souls, a full-size MPEG (298k) is even available.)
The red area represents the inner wall, or endocardium, of the heart and the light green area represents the outer wall, or epicardium, of the heart. The wireframe cubes connect points on both walls of the heart and are tracked over multiple frames to provide a notion of strain present in the left ventricle. This data will allow researchers to more fully understand the regional function of the left ventricle and assist in treating cardiac dysfunction due to infarction.
(To see the above image in 24-bit color, grab it and display it with your own external viewer. It's much nicer!)