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 μm(2)/sec minimum ADC value, 941±440 vs. 1310±440 μm(2)/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 min within solid portion and ADC av are helpful.