• R Wirestam, L Knutsson, J Risberg, S Börjesson, E-M Larsson, L Gustafson, U Passant, and F Ståhlberg.
• Department of Medical Radiation, Lund University, Lund, Sweden. ronnie.wirestam@med.lu.se
• Acta Radiol. 2007 Jun 1; 48 (5): 550-6.

BackgroundAttempts to retrieve absolute values of cerebral blood flow (CBF) by dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) have typically resulted in overestimations.PurposeTo 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.Material And Methods17 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).ResultsAverage 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).ConclusionCalibration 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.

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