Alternate ascending/descending directional navigation approach for imaging magnetization transfer asymmetry

A new method for imaging magnetization transfer (MT) asymmetry with no separate saturation pulse is proposed in this article. MT effects were generated from sequential two‐dimensional balanced steady‐state free precession imaging, where interslice MT asymmetry was separated from interslice blood flow and magnetic field inhomogeneity with alternate ascending/descending directional navigation (ALADDIN). Alternate ascending/descending directional navigation provided high‐resolution multislice MT asymmetry images within a reasonable imaging time of ～3 min. MT asymmetry signals measured with alternate ascending/descending directional navigation were 1–2% of baseline signals (N = 6), in agreement with those from the conventional methods. About 70% of MT asymmetry signals were determined by the first prior slice. The frequency offset ranges in this study were >8 ppm from the water resonance frequency, implying that the MT effects were mostly associated with solid‐like macromolecules. Potential methods to make alternate ascending/descending directional navigation feasible for imaging amide proton transfer (～3.5 ppm offset from the water resonance frequency) were discussed. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.