title: Attempts to improve absolute quantification of cerebral blood flow in dynamic susceptibility contrast magnetic resonance imaging: a simplified T1-weighted steady-state cerebral blood volume approach.
abstract: BACKGROUND
  Attempts to retrieve absolute values of cerebral blood flow (CBF) by dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) have typically resulted in overestimations.
  
  
  OBJECTIVE
  To improve DSC-MRI CBF estimates by calibrating the DSC-MRI-based cerebral blood volume (CBV) with a corresponding T1-weighted (T1W) steady-state (ss) CBV estimate.
  
  
  METHODS
  17 volunteers were investigated by DSC-MRI and 133Xe SPECT. Steady-state CBV calculation, assuming no water exchange, was accomplished using signal values from blood and tissue, before and after contrast agent, obtained by T1W spin-echo imaging. Using steady-state and DSC-MRI CBV estimates, a calibration factor K = CBV(ss)/CBV(DSC) was obtained for each individual. Average whole-brain CBF(DSC) was calculated, and the corrected MRI-based CBF estimate was given by CBF(ss) = K x CBF(DSC).
  
  
  RESULTS
  Average whole-brain SPECT CBF was 40.1+/-6.9 ml/min x 100 g, while the corresponding uncorrected DSC-MRI-based value was 69.2+/-13.8 ml/min x 100 g. After correction with the calibration factor, a CBF(ss) of 42.7+/-14.0 ml/min x 100 g was obtained. The linear fit to CBF(ss)-versus-CBF(SPECT) data was close to proportionality (R = 0.52).
  
  
  CONCLUSIONS
  Calibration by steady-state CBV reduced the population average CBF to a reasonable level, and a modest linear correlation with the reference 133Xe SPECT technique was observed. Possible explanations for the limited accuracy are, for example, large-vessel partial-volume effects, low post-contrast signal enhancement in T1W images, and water-exchange effects.
authors.affiliation: Department of Medical Radiation, Lund University, Lund, Sweden. ronnie.wirestam@med.lu.se
authors.forename: R
authors.initials: R
authors.lastname: Wirestam
authors.forename: L
authors.initials: L
authors.lastname: Knutsson
authors.forename: J
authors.initials: J
authors.lastname: Risberg
authors.forename: S
authors.initials: S
authors.lastname: Börjesson
authors.forename: E-M
authors.initials: EM
authors.lastname: Larsson
authors.forename: L
authors.initials: L
authors.lastname: Gustafson
authors.forename: U
authors.initials: U
authors.lastname: Passant
authors.forename: F
authors.initials: F
authors.lastname: Ståhlberg
mesh_terms: D000328:Adult; D000368:Aged; D001810:Blood Volume; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D015899:Tomography, Emission-Computed, Single-Photon; D014980:Xenon Radioisotopes
chemical_list: D014980:Xenon Radioisotopes