Diffusion-weighted imaging for differentiating malignant from benign mediastinal lymphadenopathy
Introduction. Mediastinal lymphadenopathy can be caused by a wide range of benign and malignant states. Determination of the genesis of lymphadenopathy is crucial for treatment planning and prognosis of the disease. The purpose of the study was to evaluate the diagnostic accuracy of diffusion weighted imaging (DWI) with apparent diffusion coefficient (ADC) measurements in differentiating malignant versus benign mediastinal lymphadenopathy. Material and Methods. 48 consecutive patients with at least one enlarged mediastinal lymph node revealed on CT-scans were examined on 1,5 T MR-machine with conventional images and respiratory-triggered DWI. In all patients one of the biggest solid lymph nodes was selected for ADC measurements and mean ADCs of each node were recorded. ADCs were correlated with the results of complete diagnostic work-up (including histopathological diagnosis in 41 patients) and follow-up CT. Statistics included Student's t-test, Mann-Whitney U-test and ROC-curve analysis. Results. 27 lymph nodes were classified as malignant (metastases, lymphoma) and 21 lymph nodes were classified as benign (sarcoidosis, reactive hyperplasia, tuberculosis). Mean ADC of malignant lymph nodes (1,02 ± 0,29*10<sup>-3</sup> mm<sup>2</sup>/s) was significantly lower than that of benign lymph nodes (1,57 ± 0,32*10<sup>-3</sup> mm<sup>2</sup>/s), p<0,0001. The cut-off value of <1,3x10<sup>-3</sup>mm<sup>2</sup>/s for ADC indicated the malignancy with a sensitivity of 81,5 % and a specificity of 85,7%. The area under the ROC-curve was 0,89 (95 % confidence interval: 0,77, 0,96), p<0,0001. Conclusion. DWI is a promising technique in chest pathology. DWI with ADC measurements could be used as a good complementary tool in the diagnostic work-up of patients with mediastinal lymphadenopathy.