title: Comparison of spiral-in/out and spiral-out BOLD fMRI at 1.5 and 3 T.
abstract: Spiral-in/out functional magnetic resonance imaging (fMRI) methods acquire one image before the echo time (TE) and a second image after TE during each scan. Weighted combination of the two images provides a time series with reduced susceptibility dropout in frontal and medial temporal regions as well as increased signal-to-noise ratio (SNR) in regions of uniform cortex. In this study, task activation with the spiral-in/out method was compared to that with conventional spiral-out acquisitions at two field strengths (1.5 and 3.0 T) using episodic memory encoding, verbal working memory, and affective processing tasks in eight human volunteers. With the conventional spiral-out sequence, greater signal dropout is observed in lateral and medial prefrontal, amygdalar, and medial temporal regions at 3 T relative to 1.5 T, whereas such dropout at 3 T is reduced or mitigated with the spiral-in/out method. Similarly, activation volumes for frontal, amygdalar, and medial temporal regions are reduced for spiral-out acquisitions relative to spiral-in/out, and this difference is more apparent at 3 T than at 1.5 T. In addition, significant regionally specific increases in Z scores are obtained with the spiral-in/out sequence relative to spiral-out acquisitions at both field strengths. It is concluded the spiral-in/out sequence may provide significant advantages over conventional spiral methods, especially at 3 T.
authors.affiliation: Department of Psychology, Stanford University, Stanford, CA 94305, USA.
authors.forename: Alison R
authors.initials: AR
authors.lastname: Preston
authors.forename: Moriah E
authors.initials: ME
authors.lastname: Thomason
authors.forename: Kevin N
authors.initials: KN
authors.lastname: Ochsner
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Cooper
authors.forename: Gary H
authors.initials: GH
authors.lastname: Glover
mesh_terms: D000328:Adult; D000339:Affect / Q000502:physiology; D000679:Amygdala / Q000502:physiology*; D016477:Artifacts; D001288:Attention / Q000502:physiology; D001931:Brain Mapping; D003118:Color Perception / Q000502:physiology; D004193:Discrimination Learning / Q000502:physiology; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D009415:Nerve Net / Q000502:physiology; D010100:Oxygen / Q000097:blood*; D010364:Pattern Recognition, Visual / Q000502:physiology; D017397:Prefrontal Cortex / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology*; D014706:Verbal Learning / Q000502:physiology
chemical_list: D010100:Oxygen