Caveat of measuring perfusion indexes using intravoxel incoherent motion magnetic resonance imaging in the human brain.

Abstract

ObjectivesTo numerically and experimentally investigate the robustness of intravoxel incoherent motion (IVIM) magnetic resonance imaging in measuring perfusion indexes in the human brain.MethodsEighteen healthy volunteers were imaged on a 3 T clinical system. Data of IVIM imaging (12 b-values ranging from 0 to 1000 s/mm2, 12 repetitions) were fitted with a bi-exponential model to extract blood volume fraction (f) and pseudo-diffusion coefficient (D*). The robustness of measurement was assessed by bootstrapping. Dynamic susceptibility contrast (DSC) imaging and arterial spin-labelling (ASL) imaging were performed for cross-modal comparison. Numerical simulations were performed to assess the accuracy and precision of f and D* estimates at varied signal-to-noise ratio (SNRb1000).ResultsBased on our experimental setting (SNRb1000 ~ 30), the average error/variability is ~5 %/25 % for f and ~100 %/30 % for D* in gray matter, and ~10 %/50 % for f and ~300 %/60 % for D* in white matter. Correlation was found between f and DSC-derived cerebral blood volume in gray matter (r = 0.29 – 0.48 across subjects, p < 10-5), but not in white matter. No correlation was found between f-D* product and ASL-derived cerebral blood flow.Conclusionsf may provide noninvasive measurement of cerebral blood volume, particularly in gray matter. D* has limited robustness and should be interpreted with caution.Key Points• A minimum SNR b1000 of 30 is recommended for reliable IVIM imaging.• f may provide noninvasive measurement of cerebral blood volume.• f correlates with CBV DSC in gray matter.• There is no correlation between fD* and CBF ASL.• D* has limited robustness and should be interpreted with caution.