title: Variable-density spiral-in/out functional magnetic resonance imaging.
abstract: A variable-density spiral k-space trajectory is introduced for brain functional magnetic resonance imaging. The proposed spiral trajectory consists of an Archimedean spiral from the k-space origin to an arbitrary fraction r of the maximum k-space radius, extending beyond this point with a variable-density spiral in which the sampling density decreases as the k-space radius increases. It, therefore, permits a reduction in readout time at the expense of undersampling only the high spatial frequencies, in which the energy in T(2)*-weighted brain images is low. The trajectory was implemented in a two-dimensional spiral-in/out sequence, and single-shot high-resolution (1.72 × 1.72 mm(2) in-plane) functional magnetic resonance imaging data were acquired from human volunteers. Compared with a two-shot fully Archimedean spiral sequence with the same spatial coverage and total scan time, the variable-density sequence yielded greater activation magnitudes with improved temporal efficiency and minor artifacts.
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California, USA. catie@stanford.edu
authors.forename: Catie
authors.initials: C
authors.lastname: Chang
authors.forename: Gary H
authors.initials: GH
authors.lastname: Glover
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001931:Brain Mapping / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D013997:Time Factors