Complex adnexal masses: detection and characterization with MR imaging--multivariate analysis

PURPOSE: To evaluate the accuracy of magnetic resonance (MR) imaging in the detection and characterization of complex adnexal masses, with particular reference to the findings predictive of malignancy, role of gadolinium-enhanced contrast material, and observer variability. MATERIALS AND METHODS: Preoperative MR imaging of the pelvis was performed in 128 consecutive patients with clinically or ultrasonographically detected complex adnexal masses. Histopathologic examination demonstrated 187 masses, 96 of which were malignant. MR imaging studies were prospectively and independently reviewed by two radiologists, one of whom reevaluated the studies after a 6-month interval. The predictive value of MR imaging findings was determined with multivariate logistic regression analysis. The value of gadolinium enhancement was assessed by using receiver operating characteristic analysis. Inter- and intraobserver variabilities were assessed by using weighted K statistics. RESULTS: Gadolinium-enhanced MR imaging depicted 176 (94%) of 187 adnexal masses, with an overall accuracy for the diagnosis of malignancy of 93%. The MR imaging findings that were most predictive of malignancy were necrosis in a solid lesion (odds ratio, 107) and vegetations in a cystic lesion (odds ratio, 40). Use of gadolinium-based contrast material contributed significantly to lesion characterization. Interobserver (K, 0.79-0.85) and intraobserver (K, 0.84-0.86) agreement were excellent. CONCLUSION: Gadolinium-enhanced MR imaging is highly accurate in the detection and characterization of complex adnexal masses, with excellent inter- and intraobserver agreement.