title: Alternate ascending/descending directional navigation approach for imaging magnetization transfer asymmetry.
abstract: 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.
authors.affiliation: Research Imaging Institute and Department of Radiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229, USA. parks6@uthscsa.edu
authors.forename: Sung-Hong
authors.initials: SH
authors.lastname: Park
authors.forename: Timothy Q
authors.initials: TQ
authors.lastname: Duong
mesh_terms: D001783:Blood Flow Velocity; D001931:Brain Mapping / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D011522:Protons; D012680:Sensitivity and Specificity
chemical_list: D011522:Protons