Evaluation of noncirrhotic hepatic parenchyma with and without significant portal vein stenosis using diffusion-weighted echo-planar MR on the basis of multiple-perfusion-components theory.

To determine whether diffusion-weighted echo-planar MR images are sensitive to liver perfusion difference. Noncirrhotic livers of 71 patients (43 males, 28 females; age range, 22-87 years; mean, 61 years) without (n=51) and with (n=20) significant (>70%) portal vein stenosis (accompanying proximal hepatic arterial stenosis and/or biliary tract obstruction in 10) by tumors were examined with diffusion-weighted echo-planar sequences (modified for b factors of 1, 28, 66, 288 and 600 s/mm²). On the basis of multiple-perfusion-components theory, i.e., assuming logarithm of signal intensity for liver perfusion is linearly attenuated versus logarithm of a smaller b factor, we defined the slope of the line as the perfusion-related D' value. The D' values of these livers were calculated from images with b factors of 1, 28, and 66 s/mm². The livers' apparent diffusion coefficient values for diffusion (ADC(d) values) were calculated from images with b factors of 288 and 600 s/mm². The livers with significant portal vein stenosis had statistically lower mean D' values than the livers without portal vein stenosis (P<.001 on the Mann-Whitney U test). However, there was no significant difference in ADC(d) values between these liver types (P>.05). The D' value calculated from diffusion-weighted echo-planar sequences with plural smaller b factors may be sensitive to liver perfusion difference.