Assessment of dynamic contrast-enhanced magnetic resonance imaging in the differentiation of malignant from benign orbital masses.

OBJECTIVE: Dynamic contrast enhanced MR imaging (DCE-MRI) allows imaging of the physiology of the microcirculation. The purpose of this study was to determine the diagnostic efficacy of time intensity curve (TIC) and DCE parameters for characterization of orbital masses.
METHODS: Fifty-nine patients with untreated orbital lesions underwent DCE-MRI before surgery. For each lesion, peak height (PH), maximum enhancement ratio (ERmax), time of peak enhancement (Tpeak) and maximum rise slope (Slopemax) were plotted and calculated. Receiver operator characteristics (ROC) analysis was conducted to assess the appropriate cut-off value.
RESULTS: All 26 lesions that demonstrated persistent pattern (type-I) TICs were benign. Most of the masses with the washout pattern (type-III) TIC were malignant (10/14), including lymphoma (n=6) and melanoma (n=4). The Slopemax of benign lesions was statistically lower than malignant ones, while the ERmax and Tpeak values of benign lesions were significantly higher. No statistical difference was found in PH (P=0.121). The AUC for ERmax, Tpeak and Slopemax in differentiating benign orbital lesions from malignant ones were 0.683, 0.837 and 0.738, respectively. In the three DCE parameters, Slopemax cut-off value of 1.10 provided the highest sensitivity of 93.8%; however, the corresponding specificity was low (58.1%). The ERmax cut-off value of 1.37 and Tpeak cut-off value of 35.14 respectively offered the best diagnostic performances.
CONCLUSION: DCE-MRI, especially the qualitative TIC pattern and quantitative value of Slopemax, ERmax and Tpeak, could be a complementary investigation in distinguishing malignant orbital tumor from benign ones.