DIFFUSION-WEIGHTED MRI IN EVALUATING LIVER FIBROSIS: A FEASIBILITY STUDY IN CIRRHOTIC PATIENTS

Purpose. This study was designed to establish whether the measurement of apparent diffusion coefficients (ADCs) is clinically accurate in diagnosing liver fibrosis in a selected series of cirrhotic patients. Materials and methods. Twenty-eight cirrhotic patients (mean age 58.1 years) with histologically proven liver fibrosis and 29 healthy controls (mean age 43.8 yeas) underwent liver diffusion-weighted magnetic resonance (MR) using a 1.5-Tesla (T) magnet equipped with a phased-array coil. Diffusion studies with parallel imaging [generalized autocalibrating partially parallel acquisitions (GRAPPA)] were performed within a single breath-hold using a single-shot spin-echo echo-planar sequence (TE 74 ms) using four b values: b=0, 150, 250 and 400 s/mm2. A unidirectional diffusion gradient was applied. ADCs were measured on ADC maps. Results. Mean ADC was significantly lower in cirrhotic livers than in controls (1.11±0.16 vs. 1.54±0.12×10-3mm2/s) (p<0.0001). Receiver operating characteristic (ROC) analysis showed an area under the curve (AUC) of 0.96 [confidence interval (CI) 95%:(0.87; 0.94)], demonstrating higher sensitivity and specificity (92.9% and 100%, respectively) for an ADC cutoff of 1.31×10-3mm2/s. Positive predictive value (PPV), negative predictive value (NPV) and overall accuracy were 100%, 99.9% and 96.4%, respectively. Conclusions. Diffusion-weighted MRI is an accurate tool in evaluating advanced liver fibrosis if an optimised single-shot spinecho echo-planar sequence with maximum intermediate b value is used. The ADC threshold for liver fibrosis was 1.31×10-3mm2/s.