title: Comparison of 2D and 3D single-shot ASL perfusion fMRI sequences.
abstract: Arterial spin labeling (ASL) can be implemented by combining different labeling schemes and readout sequences. In this study, the performance of 2D and 3D single-shot pulsed-continuous ASL (pCASL) sequences was assessed in a group of young healthy volunteers undergoing a baseline perfusion and a functional study with a sensory-motor activation paradigm. The evaluated sequences were 2D echo-planar imaging (2D EPI), 3D single-shot fast spin-echo with in-plane spiral readout (3D FSE spiral), and 3D single-shot gradient-and-spin-echo (3D GRASE). The 3D sequences were implemented with and without the addition of an optimized background suppression (BS) scheme. Labeling efficiency, signal-to-noise ratio (SNR), and gray matter (GM) to white matter (WM) contrast ratio were assessed in baseline perfusion measurements. 3D acquisitions without BS yielded 2-fold increments in spatial SNR, but no change in temporal SNR. The addition of BS to the 3D sequences yielded a 3-fold temporal SNR increase compared to the unsuppressed sequences. 2D EPI provided better GM-to-WM contrast ratio than the 3D sequences. The analysis of functional data at the subject level showed a 3-fold increase in statistical power for the BS 3D sequences, although the improvement was attenuated at the group level. 3D without BS did not increase the maximum t-values, however, it yielded larger activation clusters than 2D. These results demonstrate that BS 3D single-shot imaging sequences improve the performance of pCASL in baseline and activation studies, particularly for individual subject analyses where the improvement in temporal SNR translates into markedly enhanced power for task activation detection.
authors.affiliation: Neuroimaging Laboratory, Division of Neuroscience, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Vidorreta
authors.affiliation: Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Ze
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Chemical Physics II, Faculty of Pharmacy, UCM, Madrid, Spain; CIBER of Respiratory Diseases, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Rodríguez
authors.affiliation: Neuroimaging Laboratory, Division of Neuroscience, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain.
authors.forename: María A
authors.initials: MA
authors.lastname: Pastor
authors.affiliation: Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA; Deparment of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Detre
authors.affiliation: Neuroimaging Laboratory, Division of Neuroscience, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain. Electronic address: mfseara@unav.es.
authors.forename: María A
authors.initials: MA
authors.lastname: Fernández-Seara
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D013113:Spin Labels
chemical_list: D013113:Spin Labels
keywords: 3D GRASE; Arterial spin labeling; Background suppression; EPI; Readout sequence; Spiral imaging