Magnetic resonance imaging with T1 dispersion contrast

Prepolarized MRI uses pulsed magnetic fields to produce MR images by polarizing the sample at one field strength (∼0.5 T) before imaging at a much lower field (∼50 mT). Contrast reflecting the T1 of the sample at an intermediate field strength is achieved by polarizing the sample and then allowing the magnetization to decay at a chosen “evolution” field before imaging. For tissues whose T1 varies with field strength (T1 dispersion), the difference between two images collected with different evolution fields yields an image with contrast reflecting the slope of the T1 dispersion curve between those fields. Tissues with high protein content, such as muscle, exhibit rapid changes in their T1 dispersion curves at 49 and 65 mT due to cross‐relaxation with nitrogen nuclei in protein backbones. Tissues without protein, such as fat, have fairly constant T1 over this range; subtracting images with two different evolution fields eliminates signal from flat T1 dispersion species. T1 dispersion protein‐content images of the human wrist and foot are presented, showing clear differentiation between muscle and fat. This technique may prove useful for delineating regions of muscle tissue in the extremities of patients with diseases affecting muscle viability, such as diabetic neuropathy, and for visualizing the protein content of tissues in vivo. Magn Reson Med 2006. © 2006 Wiley‐Liss, Inc.