Modified triexponential analysis of intravoxel incoherent motion for brain perfusion and diffusion

Background To noninvasively obtain more detailed information on brain perfusion and diffusion using modified triexponential analysis. Methods On a 3.0 Tesla MRI, diffusion‐weighted imaging of the brain with multiple b‐values was performed in healthy volunteers (n = 12). We derived perfusion‐related, fast‐free, and slow‐restricted diffusion coefficients ( D p , D f , and D s , respectively) and fractions ( F p , F f , and F s , respectively) in the frontal and occipital white matter, caudate nucleus, and putamen calculated from triexponential function by a two‐step approach. D s was initially determined using monoexponential function in b‐values over 1000 s/mm 2 and was applied to triexponential function. Additionally, the literature value of the diffusion coefficient of free water at 37 °C was assigned to D f . Finally, D p and fractions were derived using all b‐values. Moreover, biexponential analysis was performed and compared with triexponential analysis. We also determined regional cerebral blood flow ( rCBF ) using arterial spin labeling and assessed its relation with each diffusion parameter. Results Significant positive correlations between D p and rCBF were found in the caudate nucleus (R = 0.84; P  = 0.01) and putamen (R = 0.86; P  = 0.01), whereas no diffusion parameters were significantly correlated with rCBF on biexponential analysis ( P  > 0.05 for all). Conclusion Diffusion analysis with triexponential function enables noninvasive gathering of more detailed information on brain perfusion and diffusion. J. Magn. Reson. Imaging 2016;43:818–823