Pulsed saturation of the standard two-pool model for magnetization transfer. Part I: The steady state

A general framework for magnetization transfer (MT) of a two-pool system with linear exchange for arbitrary saturation by periodic radio-frequency pulses was derived. It is based on a novel parameterization adapted to the time evolution of saturation recovery. The conditions in tissue permit a description in analogy to partial saturation of a homogeneous liquid. In this approximation, the direct saturation of bulk water is amplified by MT. Rapid transfer equilibrates the saturation of the pools in the early phase of free evolution. This kinetic "pre-equilibrium" relaxes slowly with a common relaxation rate. (C) 2004 Wiley Periodicals, Inc.