Characterizing Temporal B0 Field Changes in the Rat Heart
Dortch R, Does M
Quantitative NMR measurements in the rat heart are made difficult by the presence of substantial background field gradients caused by the susceptibility difference that occurs at the lung-myocardium interface. In order to characterize these field gradients, field maps were measured at several points in the cardiac cycle. The highest off-resonance values found corresponded to areas near the lung-myocardium interface. Also, B0 was found to change throughout the cardiac cycle. To assess the effect of time-varying field gradients on quantitative NMR measurements, transverse relaxation rates were measured. As expected, time-varying field gradients had a larger effect on R2* than R2.