AN EVALUATION OF THE SENSITIVITY OF THE INTRAVOXEL INCOHERENT MOTION (IVIM) METHOD OF BLOOD-FLOW MEASUREMENT TO CHANGES IN CEREBRAL BLOOD-FLOW

To evaluate the sensitivity of the intravoxel incoherent motion (IVIM) technique to changes in cerebral blood flow, we made measurements of IVIM parameters in rat brain under conditions of altered arterial pCO( 2). The arterial pCO(2) was varied over a range which would be expecte d to change cerebral blood flow from roughly 50 to 500 ml/(100 g.min). The IVIM measurements were made with suppression of extravascular wat er signal. The parameters f' (the apparent fraction of spins which hav e ''fast'' pseudodiffusion), D-1() (the ''fast-pseudodiffusion'' coef ficient), and D-2() (the ''slow-pseudodiffusion'' coefficient) all sh owed statistically significant positive linear correlations with arter ial pCO(2). These results suggest that the IVIM method, when used with suppression of extravascular water signal, is sensitive to changes in blood flow.