Apparent diffusion coefficient values and normalised apparent diffusion coefficient values in grading of glioma

Objectives: To evaluate the correlation between the grades of glioma and quantitative analysis of ADC (Apparent diffusion coefficient) values and normalised ADC values on DWI (Diffusion weighted imaging). Material and methods: Retrospective cross-sectional study including fifty adult patients with glioma, who underwent pre-operative DW-MRI followed by surgical intervention for biopsy or resection. Multiple ADC values measured in lesion and normalised ADC values calculated, were correlated with histopathology grading of the surgical specimen. Results: ADC_min, ADC_mean, nADC_min, nADC_mean were greater for low-grade tumors than high-grade tumors and this difference was statistically significant. ROC analysis showed that both ADC_min and ADC_mean are good measures to differentiate high and low-grade tumors with a ADC_min value below 0.85 x 10^-3 mm²/sec indicating high-grade tumor with an 85% sensitivity and 90% specificity and ADC_mean values below 0.93 x 10^-3 mm²/sec indicating high-grade tumor with a 85% sensitivity and 90% specificity. nADC_min and nADC_mean also differentiated high and low-grade tumors with a nADC_min value below 1.14 indicating a high-grade tumor with 90% sensitivity and 82.5% specificity and nADC_mean values below 1.4 indicating high-grade tumor with an 80% sensitivity and 85% specificity. Conclusion: This study concludes that ADC values are good measures to distinguish high-grade gliomas and low-grade gliomas. Normalised ADC values have similar sensitivity and specificity in differentiating high-grade gliomas and low-grade gliomas and can be used in indeterminate cases.