Use of MRI Apparent Diffusion Coefficient to Noninvasively Differentiate between the Histologic Grades of Meningioma.

ABSTRACT

It is well known in the literature that Apparent Diffusion Coefficient (ADC) obtained during diffusion-weighted MRI of brain is sensitive in detecting and differentiating low-grade and aggressive meningiomas. However, other studies establish no correlation between mean-ADC and ultimate classification as benign, atypical or malignant. We wanted to assess the correlation between, A. mean of MRI Apparent Diffusion Coefficient (mean-ADC) and B. meningioma biomarker Ki-67 proliferation index, in cases of both low-grade and aggressive meningioma. We also wanted to assess the sensitivity of mean-ADC for diagnosing an aggressive meningioma.METHODSWe analysed 66 surgically treated meningioma patients with complete histopathology report (HPR) in Government Medical College, Kozhikode during the period of study (Nov-2017-Oct-2018), also having a pre-operative mean-ADC value during Diffusion Weighted Imaging (DWI) investigation at the same centre. For the latter, a standard MRI brain protocol including diffusion imaging was conducted and ADC map was generated. Regions of interest (ROIs) were manually drawn within the tumour on ADC map and mean-ADC values were measured.RESULTSUsing Pearson correlation coefficient, we found a significant negative correlation between Ki-67 proliferation index and mean-ADC in meningioma cases. We also calculate 0.79 x 10-3 mm2/s being a reasonable mean-ADC cut-off value due to its sensitivity of 84% and specificity of 77% in differentiating between typical and atypical meningiomas.CONCLUSIONSThe non-invasive calculation of mean-ADC is a valid diagnostic tool. Further, mean ADC can be used as a good test to differentiate typical and atypical meningiomas. The latter is a particularly valid conclusion, since there were few results from conventional MRI studies to differentiate between various typical and atypical meningiomas.