Magnetization transfer contrast

The authors have developed a new form of contrast (magnetization transfer contrast [MTC]) for H-1 MR imaging that is sensitive to the rate of magnetization exchange between water and macromolecules. The contrast obtained is intrinsic to tissue and does not depend on the addition of extrinsic compounds. Low-power (∼ 1 x 10- 5-T) RF preirradiation (300--1,000 msec) is applied ∼ 5--10 kHz off resonance during standard imaging sequences. Images obtained by this method were high contrast-to-noise and signal-to-noise ratios. Examination of images of brain, kidney, muscle, tumors, and fat shows that the contrast obtained by this method differs from that of pure T1- and T2-weighted images. The hypothesis that MTC is based on cross-relaxation between water and macromolecules is consistent with our studies of model systems (agarose gels and cholesterol-containing lipid bilayers). In tissues where cross-relaxation is a predominant relaxation mechanism, MTC images may resemble T1- or T2- weighted images. In other tissues, MTC will produce unique contrast