Diffusion-weighted MRI for differentiation of benign from malignant lesions in the gallbladder

AIM: To investigate the value of diffusion-weighted imaging (DWI) for differentiating benign from malignant gallbladder lesions. MATERIALS AND METHODS: One hundred and twenty-six patients who had undergone magnetic resonance imaging (MRI) with DWI, in whom the histopathological diagnosis of their gallbladder lesions was confirmed by biopsy or surgery were retrospectively analysed. Thirty-six malignant and 90 benign lesions were included. Two radiologists categorized gallbladder lesions into seven types on two imaging sets [T2-weighted imaging (WI) alone and combined T2WI and DWI (b = 800 s/mm(2))] according to the presence of wall thickening, layered patterns, morphology of the mass, and diffusion restriction. Disagreements were resolved in consensus. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of each imaging set for diagnosing gallbladder carcinoma were calculated. The diagnostic performance of each imaging set was calculated using receiver operating characteristic (ROC) curve analysis. Additionally, ADC values of malignant and benign gallbladder lesions were compared separately for 1.5 and 3 T MRI. RESULTS: The sensitivity, specificity, PPV, and NPV of diagnosis at T2WI were 97.2%, 86.7%, 74.5%, and 98.7%, respectively. The sensitivity, specificity, PPV, and NPV using combined T2WI and DWI were 97.2%, 92.2%, 83.3%, and 98.8%, respectively. Diagnostic accuracy for gallbladder carcinoma slightly improved after adding DWI, from 0.92 to 0.95 (p < 0.05). ADC values for gallbladder carcinoma were significantly lower than those for benign lesions. Mean ADC values of malignant and benign lesions were 0.97 +/- 0.25 x 10(-3) and 1.72 +/- 0.56 x 10(-3) mm(2)/s, respectively, at 1.5 T (p < 0.001), and 1.04 +/- 0.38 x 10(-3) and 2.2 +/- 0.72 x 10(-3) mm(2)/s, respectively, at 3 T (p < 0.001). CONCLUSION: DWI can improve diagnostic accuracy for differentiating benign from malignant gallbladder lesions. (C) 2013 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.