Differentiation of malignant from benign focal splenic lesions: added value of diffusion-weighted MRI.

OBJECTIVE The objective of our study was to evaluate the added value of diffusion-weighted imaging (DWI) for distinguishing between malignant and benign focal splenic lesions. MATERIALS AND METHODS This study included 53 patients with 11 malignant and 42 benign splenic lesions who underwent gadoxetic acid-enhanced MRI and DWI. Qualitative and quantitative analyses were conducted for splenic lesions. Two blinded observers evaluated the two image sets--that is, the conventional MR images alone versus the combined conventional MR and DW images--and scored their confidence for malignancy of splenic lesions. The Fisher exact test and Mann-Whitney U test were performed, and diagnostic performance values (ROC curve analysis) were evaluated. RESULTS All malignant lesions showed a progressive hypovascular enhancement pattern, whereas the hypervascular enhancement patterns were shown in only benign lesions (n = 20, 47.6%) (p < 0.05). The mean apparent diffusion coefficient (ADC) of the malignant lesions (0.73 × 10(-3) mm(2)/s) was significantly lower than that of the benign lesions (1.21 × 10(-3) mm(2)/s) (p < 0.001). The addition of DW images to conventional MR images showed a significant improvement for predicting malignant splenic lesions (area under ROC curve [Az] without DW images vs with DW images: 0.774 vs 0.983 for observer 1 and 0.742 vs 0.986 for observer 2) (p < 0.001). In addition, the diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of combined conventional MR and DW images were higher than those of conventional MR images alone. CONCLUSION The addition of DWI to conventional MRI improves differentiation of malignant from benign splenic lesions.