Magnetization transfer contrast with periodic pulsed saturation

Magnetic resonance imaging with magnetization transfer contrast (MTC) was implemented on a 0.5-T clinical system by using a stream of binomial radio-frequency pulses for the selective saturation of the bound protons in tissues. Images were obtained of an egg phantom and of the calf, head, and abdomen in healthy human volunteers. Nonspecific saturation resulting in diminished signal intensity was manifested in the plots of the ratio of MTC signal to control signal for egg yolk, raw egg white, cerebrospinal fluid, and bone marrow fat. This signal degradation resulted partly from the cumulative effects of T2 on the observed transverse magnetization during presaturation. MTC imaging is dependent on repetition time; this dependence arises from the dual but conflicting effect of the selective saturation on tissues rich in macromolecular constituents. Substantial changes in tissue contrast were observed with MTC presaturation. The effect was most marked in muscle, as expected from the high protein content of this tissue.