Fast magnetization transfer and apparent T1 imaging using a short saturation pulse with and without inversion preparation

Abstract

Purpose Measurements of magnetization transfer (MT) metrics, such as the steady-state (SS) MT ratio and apparent longitudinal relaxation rate require multiple MT irradiation durations and a long experimental time. To overcome these problems, we propose a novel method using a short MT off-resonance pulse with and without on-resonance inversion preparation pulse. Theory and Methods Computer simulations were performed to examine the accuracy of the proposed method and to find the optimal off-resonance irradiation pulse duration (T irad) and power level (ω1). Our approach, with echo planar imaging data acquisition, was applied to animals at 9.4 T and humans at 3 T with ω1/2π = 100 Hz and 177 Hz, respectively. Steady-state MT ratio and relaxation rate were obtained from a pair of MT images at a Tirad, with and without inversion. Results For Tirad ≥ 0.4 s, steady-state MT ratio, and relaxation rate measured at any single Tirad agreed well with those of the conventional fitting method that uses multiple Tirad. Our simulation indicates that a higher ω1 can use a shorter Tirad. Conclusion Steady-state MT ratio and relaxation rate can be determined from MT data with only one, short T irad by incorporation of an inversion prepulse. This MT imaging approach is simple, fast, and easily implementable. © 2013 Wiley Periodicals, Inc.