Differentiation of malignant from benign soft tissue tumours: use of additive qualitative and quantitative diffusion-weighted MR imaging to standard MR imaging at 3.0 T

Objectives: To determine the added value of diffusion-weighted imaging (DWI) to standard magnetic resonance imaging (MRI) to differentiate malignant from benign soft tissue tumours at 3.0 T. Methods: 3.0 T MR images including DWI in 63 patients who underwent surgery for soft tissue tumours were retrospectively analyzed. Two readers independently interpreted MRI for the presence of malignancy in two steps: standard MRI alone, standard MRI and DWI with qualitative and quantitative analysis combined. Results: There were 34 malignant and 29 non-malignant soft tissue tumours. In qualitative analysis, hyperintensity relative to skeletal muscle was more frequent in malignant than benign tumours on DWI (P=0.003). In quantitative analysis, ADCs of malignant tumours were significantly lower than those of non-malignant tumours (P≤0.002): 759±385 vs. 1188±423 μm²/sec minimum ADC value, 941±440 vs. 1310±440 μm²/sec average ADC value. The mean sensitivity, specificity and accuracy of both readers were 96 %, 72 %, and 85 % on standard MRI alone and 97 %, 90 %, and 94 % on standard MRI with DWI. Conclusions: The addition of DWI to standard MRI improves the diagnostic accuracy for differentiation of malignant from benign soft tissue tumours at 3.0 T. Key Points: • DWI has added value for differentiating malignant from benign soft tissue tumours. • Addition of DWI to standard MRI at 3.0 T improves the diagnostic accuracy. • Measurements of both ADC_minwithin solid portion and ADC_avare helpful.