title: High spatial resolution brain functional MRI using submillimeter balanced steady-state free precession acquisition.
abstract: OBJECTIVE
  One of the technical advantages of functional magnetic resonance imaging (fMRI) is its precise localization of changes from neuronal activities. While current practice of fMRI acquisition at voxel size around 3 × 3 × 3 mm(3) achieves satisfactory results in studies of basic brain functions, higher spatial resolution is required in order to resolve finer cortical structures. This study investigated spatial resolution effects on brain fMRI experiments using balanced steady-state free precession (bSSFP) imaging with 0.37 mm(3) voxel volume at 3.0 T.
  
  
  METHODS
  In fMRI experiments, full and unilateral visual field 5 Hz flashing checkerboard stimulations were given to healthy subjects. The bSSFP imaging experiments were performed at three different frequency offsets to widen the coverage, with functional activations in the primary visual cortex analyzed using the general linear model. Variations of the spatial resolution were achieved by removing outer k-space data components.
  
  
  RESULTS
  Results show that a reduction in voxel volume from 3.44 × 3.44 × 2 mm(3) to 0.43 × 0.43 × 2 mm(3) has resulted in an increase of the functional activation signals from (7.7 ± 1.7)% to (20.9 ± 2.0)% at 3.0 T, despite of the threefold SNR decreases in the original images, leading to nearly invariant functional contrast-to-noise ratios (fCNR) even at high spatial resolution. Activation signals aligning nicely with gray matter sulci at high spatial resolution would, on the other hand, have possibly been mistaken as noise at low spatial resolution.
  
  
  CONCLUSIONS
  It is concluded that the bSSFP sequence is a plausible technique for fMRI investigations at submillimeter voxel widths without compromising fCNR. The reduction of partial volume averaging with nonactivated brain tissues to retain fCNR is uniquely suitable for high spatial resolution applications such as the resolving of columnar organization in the brain.
authors: Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan.
authors: Pei-Hsin
authors: PH
authors: Wu
authors: Ping-Huei
authors: PH
authors: Tsai
authors: Ming-Long
authors: ML
authors: Wu
authors: Tzu-Chao
authors: TC
authors: Chuang
authors: Yi-Yu
authors: YY
authors: Shih
authors: Hsiao-Wen
authors: HW
authors: Chung
authors: Teng-Yi
authors: TY
authors: Huang
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D059629:Signal-To-Noise Ratio