Quantitative measurement of brain perfusion with intravoxel incoherent motion MR imaging.
OBJECTIVE
To evaluate the sensitivity of the perfusion parameters derived from Intravoxel Incoherent Motion (IVIM) MR imaging to hypercapnia-induced vasodilatation and hyperoxygenation-induced vasoconstriction in the human brain.


METHODS
This study was approved by the local ethics committee and informed consent was obtained from all participants. Images were acquired with a standard pulsed-gradient spin-echo sequence (Stejskal-Tanner) in a clinical 3-T system by using 16 b values ranging from 0 to 900 sec/mm(2). Seven healthy volunteers were examined while they inhaled four different gas mixtures known to modify brain perfusion (pure oxygen, ambient air, 5% CO(2) in ambient air, and 8% CO(2) in ambient air). Diffusion coefficient (D), pseudodiffusion coefficient (D*), perfusion fraction (f), and blood flow-related parameter (fD*) maps were calculated on the basis of the IVIM biexponential model, and the parametric maps were compared among the four different gas mixtures. Paired, one-tailed Student t tests were performed to assess for statistically significant differences.


RESULTS
Signal decay curves were biexponential in the brain parenchyma of all volunteers. When compared with inhaled ambient air, the IVIM perfusion parameters D*, f, and fD* increased as the concentration of inhaled CO(2) was increased (for the entire brain, P = .01 for f, D*, and fD* for CO(2) 5%; P = .02 for f, and P = .01 for D* and fD* for CO(2) 8%), and a trend toward a reduction was observed when participants inhaled pure oxygen (although P > .05). D remained globally stable.


CONCLUSIONS
The IVIM perfusion parameters were reactive to hyperoxygenation-induced vasoconstriction and hypercapnia-induced vasodilatation. Accordingly, IVIM imaging was found to be a valid and promising method to quantify brain perfusion in humans.
Department of Diagnostic and Interventional Radiology, CHUV, University Hospital Center and University of Lausanne, Rue du Bugnon 46, 1011 Lausanne, Switzerland. christian.federau@chuv.ch
Christian
C
Federau
Philippe
P
Maeder
Kieran
K
O'Brien
Patrick
P
Browaeys
Reto
R
Meuli
Patric
P
Hagmann
D000328:Adult; D000388:Air; D001783:Blood Flow Velocity; D001921:Brain / Q000098:blood supply* / Q000378:metabolism; D001931:Brain Mapping / Q000379:methods*; D002245:Carbon Dioxide / Q000008:administration & dosage; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010100:Oxygen / Q000008:administration & dosage; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D014661:Vasoconstriction; D014664:Vasodilation
D002245:Carbon Dioxide; D010100:Oxygen