Visual qualitative evaluation of diffusion-weighted imaging, apparent diffusion coefficient quantification and Ki-67 proliferation index for predicting atypia in surgical meningiomas

Object. The goal in this study was to investigate the efficiency of qualitative evaluation using DW imaging, ADC quantification, and Ki-67 proliferation labeling index in grading intracranial meningiomas compared to our reference standard histopathology. Methods. From our database, we enrolled 35 consecutive patients with pathologic report of a meningioma, conventional MR imaging, contrast-enhanced MR imaging, DW imaging and ADC maps. Results. Eight patients (23%) had atypical meningioma (5 women and 3 men; mean age: 57.1±15.8 years); 27 (77%) had low-grade-typical (19 women, 8 men; mean age: 54.3±14.0 years). The most frequent histological subtype was the meningothelial type in both low-grade (37%) and atypical meningiomas (59%). The mean Ki-67 proliferation index for low-grade and atypical meningiomas were 2.31±1.44% (range: 1-5) and 7.37 ± 2.72% (range: 3-10), respectively. Meningiomas with Ki-67 proliferation index higher than 4% (except one) were atypical (p<0.001). In visual qualitative evaluation; diffusion restriction was significantly more common in atypical meningiomas (p<0.05). In quantitative evaluation, benign and atypical tumor groups had no significant difference in mean ADC values (p=0.471). Conclusion. We suggest that visual qualitative evaluation of DW imaging may be helpful to predict atypia and the risk of recurrence in patients with surgically treated meningiomas