Use of Diffusion Weighted Imaging in Differentiating Between Maligant and Benign Meningiomas. A Multicenter Analysis

BACKGROUND: Meningioma is the most frequent intracranial tumor and is often an incidental finding on imaging. Some imaging-based scores were suggested for differentiating low- and high-grade meningiomas. The purpose of this work was to compare diffusion-weighted imaging findings of different meningiomas in a large multicenter study by using apparent diffusion coefficient (ADC) values for predicting tumor grade and proliferation potential. METHODS: Data from 7 radiologic departments were acquired retrospectively. Overall, 389 patients were collected. All meningiomas were investigated by magnetic resonance imaging (1.5-T scanner) by using diffusion-weighted imaging (b values of 0 and 1000 s/mm(2)). The comparison of ADC values was performed by Mann-Whitney U test. RESULTS: World Health Organization grade I was diagnosed in 271 cases (69.7%), grade II in 103 (26.5%), and grade III in 15 patients (3.9%). Grade I meningiomas showed statistically significant higher ADC values (1.05 +/- 0.39 x 10(-3) mm(2)s(-1)) in comparison with grade II (0.77 +/- 0.15 x 10(-3) mm(2)s(-1); P = 0.001) and grade III tumors (0.79 +/- 0.21 x 10(-3) mm(2)s(-1); P = 0.01). An ADC value of <0.85 x 10(-3) mm(2)s(-1) was determined as the threshold in differentiating between grade I and grade II/III meningiomas (sensitivity, 72.9%; specificity, 73.1%; accuracy, 73.0%). Ki67 was associated with ADC (r = -0.63, P < 0.001). The optimal threshold for the ADC was (less than) 0.85 x 10(-3) mm(2)s(-1) for detecting tumors with high proliferation potential (Ki67 >= 5%). CONCLUSIONS: The estimated threshold ADC value of 0.85 can differentiate grade I meningioma from grade II and III tumors. The same ADC value is helpful for detecting tumors with high proliferation potential.