Assessment of soft tissue tumours of the extremities with diffusion echoplanar MR imaging

Abstract

This study assessed soft tissue tumours of the extremities with diffusion echo-planar magnetic resonance (MR) imaging. We carried out a retrospective study of 37 patients (22 male, 15 female; age range 4-68 years; mean age 41 years) with a soft tissue mass. Diffusion-weighted magnetic resonance (MR) imaging was done using echo-planar imaging (EPI) with b factor of 0.500 and 1,000 mm2/s. The apparent diffusion coefficient (ADC) map was reconstructed with calculation of the ADC values of the mass. The mean ADC value of the malignant tumours was 1.02±0.03×10(-3)mm(2)/s and that of benign masses 1.54±0.03×10(-3)mm(2)/s. There was a significant difference in the ADC values between malignant soft tissue tumours and benign masses (p<0.001) and within different grades of malignancy (p<0.02). Selection of 1.34×10(-3) mm(2)/s as a threshold ADC value for differentiating malignant soft tissue tumours from benign masses resulted in an accuracy of 91%, sensitivity of 94%, specificity of 88% and area under the curve of 0.869. There was a significant difference in the ADC value between well- and poorly differentiated malignancies (p=0.001). Diffusion-weighted echo-planar MR imaging is a promising noninvasive modality that may be helpful in differentiating malignant soft tissue tumours from benign masses as well as in grading malignancy.