Apparent Diffusion Coefficient of Diffusion Weighted Imaging have Strong Correlation with the Malignancy Grading of Intracranial Tumor

Background and purpose: Accurate imaging diagnosis before surgery is fundamental to determine whether a tumor is benign or malignant. Diagnosis only from structural MRI is not specific. However, the diffusivity of the benign and malignant lesion is different and could be measured by ADC. The Apparent Diffusion Coefficient (ADC) values are calculated automatically by application software and displayed as a parametric map that reflects the degree of diffusion of water molecules through different tissues. The purpose of this study was to analyze the correlation between Diffusion-Weighted Magnetic Resonance Imaging (DWI) and Apparent Diffusion Coefficient (ADC) values with histopathology grading of brain tumors.

Material and methods: Pathology reports of intracranial tumor material were correlated with diffusivity of the tumor, and the ADC values, performed within 2 years of post-operative histopathology study. A freehand closed ROI out-lined the whole visible tumor on the most representative slice of ADC maps defined as the slice with the maximum diameter of the solid neoplastic component. ADC values were taken from 2 averages of 2 ROIs. Spearman Correlation test was used to assess the correlation between ADC values with the malignancy grading of the tumor.

Result: Low-grade malignant tumors show facilitated diffusion with high ADC values, and high-grade malignant tumors show restricted diffusion with low ADC values. The mean ADC value of Grade I tumor is 1.0799 ± 0.2356 x 10⁻³ mm²/sec and the mean ADC value of Grade IV tumor is 0.6798 ± 0.23729 x 10⁻³ mm²/sec. The Spearman correlation test between ADC value and histopathology result shown r = -0.536 and p=0.000 and the test result for ADC value and DWI shown r=-0.706 and p=0.000 (Sig. 0.05).

Conclusion: There was strong correlation between DWI and ADC values with histopathology grading of intracranial tumors.