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

Abstract

In this study the exchange between ¹H magnetization in “free” water (¹H_f) and that in a pool with restricted motion (¹H_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 ¹H_f with radiofrequency irradiation of ¹H_r. The pseudo-first-order rate constant for the movement of magnetization from ¹H_fto ¹H_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 ¹H_f and ¹H_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 ¹H in vivo. © 1989 Academic Press. Inc.