Magnetization transfer contrast (MTC) and tissue water proton relaxation in vivo

Abstract

In this study the exchange between 1 H magnetization in “free” water (1 H f) and that in a pool with restricted motion (1 H r) was observed in tissues in vivo using NMR saturation transfer methods. Exchange between these two pools was demonstrated by a decrease in the steady‐state magnetization and relaxation times of 1 H f with radiofrequency irradiation of 1 H r. The pseudo‐first‐order rate constant for the movement of magnetization from 1 H f to 1 H r was ∼ Is−1 in kidney and ∼3s−1 in skeletal muscle in vivo. Proton NMR imaging demonstrated that this exchange was tissue specific and generated a novel form of NMR image contrast. The extent of exchange between 1 H f and 1 H r as well as the topological correlation ofthe exchange with relaxation weighted images suggests that this pathway is a major determinant of the observed relaxation properties of water 1 H in vivo. © 1989 Academic Press. Inc.