title: Suppression of effects of gradient imperfections on imaging with alternate ascending/descending directional navigation.
abstract: Alternate ascending/descending directional navigation (ALADDIN) is a new imaging technique that provides interslice perfusion-weighted and magnetization transfer (MT) asymmetry images. In this article, we investigated the effects of gradient imperfections on ALADDIN MT asymmetry (MTA) signals. Subtraction artifacts increasing with readout offsets were detectable in ALADDIN MTA images from an agarose phantom but not from a water phantom. Slice-select offsets had no significant effect on the artifacts in MTA. The artifacts were suppressed by averaging signals over the readout gradient polarities independent of scan parameters. All these results suggested that the subtraction artifacts were induced by readout eddy currents. With suppression of the artifacts, ALADDIN signals in human brain and skeletal muscle varied less with scan conditions. Percent signal changes of MTA in human skeletal muscle (0.51 ± 0.11%, N = 3) were about 30% of those in white matter. The new averaging scheme will allow for more accurate MTA imaging with ALADDIN, especially at off-center positions.
authors.affiliation: Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA. sup6@pitt.edu
authors.forename: Sung-Hong
authors.initials: SH
authors.lastname: Park
authors.forename: Tiejun
authors.initials: T
authors.lastname: Zhao
authors.forename: Jung-Hwan
authors.initials: JH
authors.lastname: Kim
authors.forename: Fernando E
authors.initials: FE
authors.lastname: Boada
authors.forename: Kyongtae Ty
authors.initials: KT
authors.lastname: Bae
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000166:cytology; D001931:Brain Mapping / Q000379:methods; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D018482:Muscle, Skeletal / Q000166:cytology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity