Magnetization transfer contrast of body tissues in vivo in MR imaging

Magnetization transfer (MT) is a newly introduced, tissue-dependent characteristic caused by interactions between mobile water protons and molecularly bound protons. MT contrast reflects the concentration of macromolecules and the cross-relaxation rate in tissues, and it offers a unique form of MR image contrast. The authors of this paper studied 20 subjects using a 0.1-T device (Instrumentarium, Helsinki, Finland). The MT sequence consisted of an off-resonance radio-frequency pulse applied before a standard gradient-echo 1,000/30 pulse sequence to a 10-mm section. The off-resonance pulse had an amplitude of 0.25 G, a duration of 300 msec, and frequency offset of 8 kHz (specific absorption rate <1W/kg). A gradient-echo 1,000/30 sequence was applied at the same level in an interleaved manner. The authors measured the signal intensity of liver, spleen, skeletal muscle, and subcutaneous fat on MT contrast images (IMT) and gradient-encho images (IGE)