title: Functional perfusion imaging using pseudocontinuous arterial spin labeling with low-flip-angle segmented 3D spiral readouts.
abstract: Arterial spin labeling (ASL) provides quantitative and reproducible measurements of regional cerebral blood flow, and is therefore an attractive method for functional MRI. However, most existing ASL functional MRI protocols are based on either two-dimensional (2D) multislice or 3D spin-echo and suffer from very low image signal-to-noise ratio or through-plane blurring. 3D ASL with multishot (segmented) readouts can improve the signal-to-noise ratio efficiency relative to 2D multislice and does not suffer from T(2)-blurring. However, segmented readouts require lower imaging flip-angles and may increase the susceptibility to temporal signal fluctuations (e.g., due to physiology) relative to 2D multislice. In this article, we characterize the temporal signal-to-noise ratio of a segmented 3D spiral ASL sequence, and investigate the effects of radiofrequency phase cycling scheme and flip-angle schedule on image properties. We show that radiofrequency-spoiling is essential in segmented 3D spiral ASL, and that 3D ASL can improve temporal signal-to-noise ratio 2-fold relative to 2D multislice when using a simple polynomial (cubic) flip-angle schedule. Functional MRI results using the proposed optimized segmented 3D spiral ASL protocol show excellent activation in the visual cortex.
authors.affiliation: Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA. jfnielse@umich.edu
authors.forename: Jon-Fredrik
authors.initials: JF
authors.lastname: Nielsen
authors.forename: Luis
authors.initials: L
authors.lastname: Hernandez-Garcia
mesh_terms: D000465:Algorithms; D001931:Brain Mapping / Q000379:methods*; D002560:Cerebrovascular Circulation / Q000502:physiology; D005074:Evoked Potentials, Visual / Q000502:physiology; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013113:Spin Labels; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*
chemical_list: D013113:Spin Labels