Diffusion-weighted imaging of the liver:: Optimizing b value for the detection and characterization of benign and malignant hepatic lesions

Purpose: To determine the optimal b values required for diffusion-weighted (DW) imaging of the liver in the detection and characterization of benign and malignant hepatic lesions. Materials and Methods: MR images obtained in 76 patients including 28 malignant hepatic lesions (21 hepatocellular carcinomas and 7 metastases) and 27 benign lesions (12 hemangiomas and 15 cysts) were reviewed. DW-echo planner images (EPIs: b values with 100, 200, 400, and 800 s/mm(2)) were reviewed solely first, and then with T2-weighted EPIs (b = 0 s/mm(2)). Results: Sensitivity for malignant lesions (74%) was highest on DW-EPIs with b value of 100 s/mm(2) and T2-weighted EPIs combined (P < 0.05), and sensitivity for benign lesions (87%) was highest on DW-EPIs with b value of 800 s/mm(2) and T2-weighted EPIs (P < 0.05). Specificities were comparably high for all sequences. The Az values for malignant lesions were 0.94, 0.90, 0.87, and 0.89, and those for benign lesions were 0.91, 0.89, 0.87, and 0.94 on DW-EPIs with b values of 100, 200, 400, and 800 and T2-weighted EPIs combined. respectively. Hepatic cysts were clearly distinguished with the cutoff ADC value of 2.5 x 10(-3) mm(2)/s using a b value of 400 s/mm2 or greater. Conclusion: DW-EPIs with middle b values were not required in the detection and characterization of benign and malignant hepatic lesions.