title: Vascular space occupancy-dependent functional MRI by tissue suppression.
abstract: OBJECTIVE
  To measure the cerebral blood volume (CBV) dynamics during neural activation, a novel technique named vascular space occupancy (VASO)-based functional MRI (fMRI) was recently introduced for noninvasive CBV detection. However, its application is limited because of its low contrast-to-noise ratio (CNR) due to small signal change from the inverted blood.
  
  
  METHODS
  In this study a new approach-VASO with tissue suppression (VAST)-is proposed to enhance CNR. This technique is compared with VASO and blood oxygenation level-dependent (BOLD) fMRI in block-design and event-related visual experiments.
  
  
  RESULTS
  Based on acquired T(1) maps, 75.3% of the activated pixels detected by VAST are located in the cortical gray matter. Temporal characteristics of functional responses obtained by VAST were consistent with that of VASO. Although the baseline signal was decreased by the tissue suppression, the CNR of VAST was about 43% higher than VASO.
  
  
  CONCLUSIONS
  With the improved sensitivity, VAST fMRI provides a useful alternative for mapping the spatial/temporal features of regional CBV changes during brain activation. However, the technical imperfectness of VAST, such as the nonideal inversion efficiency and physiological contaminations, limits its application to precise CBV quantification.
authors.affiliation: Interdisciplinary MRI/MRS Lab, Department of Electrical Engineering, National Taiwan University, Section 4 No. 1 Roosevelt Road, Taipei, Taiwan.
authors.forename: Changwei W
authors.initials: CW
authors.lastname: Wu
authors.forename: Kai-Hsiang
authors.initials: KH
authors.lastname: Chuang
authors.forename: Yau-Yau
authors.initials: YY
authors.lastname: Wai
authors.forename: Yung-Liang
authors.initials: YL
authors.lastname: Wan
authors.forename: Jyh-Horng
authors.initials: JH
authors.lastname: Chen
authors.forename: Ho-Ling
authors.initials: HL
authors.lastname: Liu
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male