NIMG-01ADVANCED MR PERFUSION AND DIFFUSION MEASURES DISTINGUISH BETWEEN GLIOMA SUBTYPES

Abstract

BACKGROUND: Advanced MR imaging provides invaluable information on brain tumor biology and behavior, making it an important complement to standard histopathology. In light of mounting molecular evidence against the existence of true mixed gliomas, we present the use of relative cerebral blood volume (rCBV) to classify gliomas as a function of glioma tumor type and grade. METHODS: Histopathological findings of 145 tissue specimens from 42 consented adult patients were studied. Histopathological diagnosis for each tissue specimen was obtained from the neurosurgical pathology report and according to the WHO brain tumor grading system. Preoperative (≤ 3 months) DSC-MRI and T1 + C images were co-registered to MR Imaging uploaded for surgical navigation. Guided by intraoperative screenshots from a StealthStation® S7™ surgical navigation unit, a 6-mm spherical region of interest (ROI) was drawn manually for each distinct tissue sampling site. Median Apparent Diffusion Coefficient (ADC) and standardized leakage-corrected rCBV values (sRCBV) were determined using the same ROIs. Only positive non-zero values were included in the analysis. Statistical sample independence for both sRCBV and ADC was confirmed before conducting statistical analyses. RESULTS: The sRCBV measures for grade 2 gliomas were comparable across type, yet the ADC values demonstrate a significant distinction of astrocytomas from oligodendrogliomas (p < 0.01) and mixed oligoastrocytomas (p < 0.001). Grade 3 astrocytomas also exhibited significantly different sRCBV and ADC values from oligodendrogliomas (p < 0.05) and oligoastrocytomas (p < 0.001). Similarly, the sRCBV and ADC values were significantly different between pure grade 4 astrocytomas (GBM) and GBMs with oligodendroglial component (p < 0.001). No significant differences were noted between oligodendrogliomas and oligoastrocytomas. CONCLUSION: Significant differences in perfusion and diffusion measures highlight the biologically distinct character of astrocytomas and oligodendrogliomas. Mixed gliomas share more similarities with oligodendrogliomas than with astrocytomas on advanced MR imaging, supporting the hypothesis that mixed gliomas may not represent a separate glioma subtype.