title: Quantitative mapping of cerebral metabolic rate of oxygen (CMRO2 ) using quantitative susceptibility mapping (QSM).
abstract: OBJECTIVE
  To quantitatively map cerebral metabolic rate of oxygen ( CMRO2) and oxygen extraction fraction ( OEF) in human brains using quantitative susceptibility mapping (QSM) and arterial spin labeling-measured cerebral blood flow (CBF) before and after caffeine vasoconstriction.
  
  
  METHODS
  Using the multiecho, three-dimensional gradient echo sequence and an oral bolus of 200 mg caffeine, whole brain CMRO2 and OEF were mapped at 3-mm isotropic resolution on 13 healthy subjects. The QSM-based CMRO2 was compared with an R2*-based CMRO2 to analyze the regional consistency within cortical gray matter (CGM) with the scaling in the R2* method set to provide same total CMRO2 as the QSM method for each subject.
  
  
  RESULTS
  Compared to precaffeine, susceptibility increased (5.1 ± 1.1 ppb; P < 0.01) and CBF decreased (-23.6 ± 6.7 ml/100 g/min; P < 0.01) at 25-min postcaffeine in CGM. This corresponded to a CMRO2 of 153.0 ± 26.4 μmol/100 g/min with an OEF of 33.9 ± 9.6% and 54.5 ± 13.2% (P < 0.01) pre- and postcaffeine, respectively, at CGM, and a CMRO2 of 58.0 ± 26.6 μmol/100 g/min at white matter. CMRO2 from both QSM- and R2*-based methods showed good regional consistency (P > 0.05), but quantitation of R2*-based CMRO2 required an additional scaling factor.
  
  
  CONCLUSIONS
  QSM can be used with perfusion measurements pre- and postcaffeine vascoconstriction to map CMRO2 and OEF.
authors.affiliation: Department of Biomedical Engineering, Cornell University, Ithaca, NY, USA.|Department of Radiology, Weill Cornell Medical College, New York, NY, USA.
authors.forename: Jingwei
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Medimagemetric, LLC, New York, NY, USA.
authors.forename: Tian
authors.initials: T
authors.lastname: Liu
authors.affiliation: Department of Radiology, Weill Cornell Medical College, New York, NY, USA.
authors.forename: Ajay
authors.initials: A
authors.lastname: Gupta
authors.affiliation: Department of Radiology, Weill Cornell Medical College, New York, NY, USA.
authors.forename: Pascal
authors.initials: P
authors.lastname: Spincemaille
authors.affiliation: Department of Radiology, Weill Cornell Medical College, New York, NY, USA.
authors.forename: Thanh D
authors.initials: TD
authors.lastname: Nguyen
authors.affiliation: Department of Biomedical Engineering, Cornell University, Ithaca, NY, USA.|Department of Radiology, Weill Cornell Medical College, New York, NY, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply / Q000187:drug effects / Q000378:metabolism*; D001931:Brain Mapping / Q000379:methods*; D002110:Caffeine / Q000494:pharmacology; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology*
chemical_list: D002110:Caffeine; D010100:Oxygen
keywords: OEF; QSM; quantitative CMRO2