In vivo measurement of T*2 and field inhomogeneity maps in the human heart at 1.5 T.

Cardiac echo-planar imaging suffers invariably from regions of severe distortion and T2 decay in the myocardium. The purpose of this work was to perform local measurements of T2 and field inhomogeneities in the myocardium and to identify the sources of focal signal loss and distortion. Field inhomogeneity maps and T2 were measured in five normal volunteers in short-axis slices spanning from base to apex. It was found that T2 ranged from 26 ms (SD = 7 ms, n = 5) to 41 ms (SD = 11 ms, n = 5) over most of the heart, and peak-to-peak field inhomogeneity differences were 71 Hz (SD = 14 Hz, n = 5). In all hearts, regions of severe signal loss were consistently adjacent to the posterior vein of the left ventricle; T*2 in these regions was 12 ms (SD = 2 ms, n = 5), and the difference in resonance frequency with the surrounding myocardium was 70-100 Hz. These effects may be caused by increased magnetic susceptibility from deoxygenated blood in these veins.