[Value of diffusion-weighted imaging in differentiating sellar malignant germ cell tumors from raniopharyngioma]

Objective: To investigate the diagnostic value of diffusion-weighted imaging (DWI) and apparent diffusion coefficient(ADC) values in the differentiation of sellar malignant germ cell tumors and raniopharyngioma. Methods: This retrospective study included 36 patients(14 cases of malignant germ cell tumor and 22 patients with raniopharyngioma) with histopathologically-confirmed sellar tumors from January 2013 to April 2017 in the First Affiliated Hospital of Zhengzhou University.All patients underwent conventional MRI and DWI before the treatment. ADC maps were reconstructed, and ADC values of the sellar lesions were calculated and compared between the groups. Diagnostic value of ADC was evaluated by receiver operating characteristic(ROC) curves. Results: The mean ADC values of malignant germ cell tumors were significantly lower than that in raniopharyngioma[(0.93±0.23)×10(-3) mm(2)/s vs (1.69±0.21)×10(-3) mm(2)/s, t=-10.19, P<0.01]. The area under the ROC curves of ADC values diagnosing malignant germ cell tumors and raniopharyngioma was 0.987. The optimal cutoff values of ADC for differential diagnosis of malignant germ cell tumors and raniopharyngioma was 1.52×10(-3) mm(2)/s, the sensitivity, specificity and accuracy was 81.2%, 100%, 88.9%, respectively. ADC value had a high consistency with pathological results (Kappa value was 0.887). Conclusion: Malignant germ cell tumors and raniopharyngioma have different ADC value, which can improve the diagnostic accuracy.