Effect of Diffusion Time on Liver DWI

2) along phase encoding (L-R) direction were acquired in one axial slice covering a large portion of the liver while avoiding inclusion of the lung with respiration-gated single shot stimulated-echo-EPI sequence. DW experiments were repeated with Δ= 15, 45 and 200ms. Imaging parameters were TR/TE=~2000/20ms, δ=3.1ms, slice thickness= 3mm, FOV=51×51mm 2 , acquisition matrix=51×51, NEX=11. Data analysis: A large ROI excluding large blood vessels was drawn on liver parenchyma encompassing a large homogeneous liver region. Apparent diffusion coefficient (ADC) was obtained by fitting the equation: SIb/SI0=exp(-b×ADC) with the ROI measurements of SIb/SI0 at all five b values (0, 200, 400, 800, 1000 s/mm 2 ) using a least-square nonlinear fitting in Matlab. Blood pseudo-diffusion coefficient (DPseudo) was calculated by from equation: SIb/SI0=exp(-b×DPseudo) using b=0 and 200 s/mm 2 . True diffusion coefficient (DTrue) was estimated by fitting the signal decay in the ROI on the images of three large b values (400, 800 and 1000 s/mm 2 ) to the equation: SIb/SI0=(1-f)×exp(-b×DTrue). One-way ANOVA with Turkey’s multiple comparison tests was employed to compare ADC, DPseudo and DTrue measurements of liver between different Δ, and p< 0.05 was considered as statistical significant.