Purpose: On these bases, the purpose of this study was to investigate patterns of water diffusion (isotropic vs. non-isotropic) in normal and cirrhotic livers. .
Methods and Materials: Ten cirrhotic patients and 10 controls underwent DW-MRI on a 1.5T-system. For each subject, a Single-shot Spin-Echo Echo-Planar sequence was acquired, using sequential unidirectional gradients along slice, read and phase directions, respectively. Apparent Diffusion Coefficients (ADCs) of the hepatic parenchyma were calculated for each direction using two different sets of b-values (0-400 and 0-800 sec/mm2), at two hepatic sites (hepatic dome and portal plane).
Results: No significant difference among slice-, read- and phase-liver ADCs was found within controls and cirrhotic patients, neither at hepatic dome, nor at portal plane (p<0.01;Kruskal-Wallis test). An exception was found at portal plane within controls, representing a casual, non-systematic effect (2.2±0.5 vs. 1.6±0.2 x10-3 mm2/sec for read vs. phase at b=800 sec/mm2). Additionally, no significant difference (p<0.01) in mean hepatic ADCs was found: (i) in comparing them at the same set of b-values and site of measurement within controls and cirrhotic patients (t-test); (ii) in comparing controls vs. cirrhotic patients at both sets of b-values of 0-400 sec/mm2 (1.9-2.7 vs. 1.9-2.2 x10-3 mm2/sec at hepatic dome, and 2.1-2.5 vs. 1.6-2.1 x10-3 mm2/sec at portal plane), and 0-800 sec/mm2 (1.6-2.0 vs. 1.4-1.8 x10-3 mm2/sec at hepatic dome, and 1.6-2.2 vs. 1.4-1.6 x10-3 mm2/sec at portal plane) (repeated-measures ANOVA).
Conclusion: Water diffusion in the liver, measured as parenchymal ADC, is isotropic both in controls and cirrhotics, regardless of the b-values used or anatomic sites of measurement. DW-MRI is unable to differentiate between cirrhotic and healthy livers.
