Abstract #3081

Apparent diffusion coefficient for molecular subtyping of non-Gadolinium-enhancing WHO grade II/III glioma

Laura Mancini^1,2, Sara Hassanein^2,3, Sotirios Bisdas^1,2, Jeremy H Rees^2,4, Harpreet Hyare^2,3, John A Maynard³, Sebastian Brandner⁵, Carmen Tur⁶, H Rolf Jager^1,2,3, Tarek Yousry^1,2,3, and Steffi C Thust^1,2,3

¹Lysholm Department of Neuroradiology, National Hospital for Neurology & Neurosurgery UCLH NHS FT, London, United Kingdom, ²Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, London, United Kingdom, ³Imaging Department, University College Hospital UCLH NHS FT, London, United Kingdom, ⁴Neurology Department, Natl Hosp for Neurology & Neurosurgery UCLH NHS FT, London, United Kingdom, ⁵Department of Neurodegenerative Disease, UCL Institute of Neurology and Division of Neuropathology, London, United Kingdom, ⁶Department of Neuroinflammation, Queen Square MS Centre, UCL Institute of Neurology, London, United Kingdom

A proportion of non-enhancing intrinsic presumed low-grade-gliomas(LGG), rapidly progresses. Hypothesis: ADC can predict glioma molecular subtypes of the revised 2016 World_Health_Organization brain tumours classification. Methods..44 non-Gadolinium-enhancing LGG divided in three molecular subgroups. 2D and 3D T2-derived tumour and normal-appearing-white-matter (NAWM) masks co-registered to ADC_maps(b=1000s/mm²). Linear-regression, ROC-analysis and logistic-regression compared ADC_values with tumour type. Results..ADCmean and ADCratio(tumour/NAWM) were lowest (p<0.001) in the most malignant tumour type (IDHwt). An ADCmean(ADCratio) threshold of 1201*10^-6mm²/s(1.65) identified IDHwt with sensitivity=83%(80%) and specificity=86%(92%) (AUC=0.9-0.94). Between-observers (2D-versus-3D) intraclass-correlation-coefficient=0.98(0.92). Conclusions..ADC measurements can support the distinction of non-enhancing glioma subtypes. 3D and 2D measurements were both accurate.

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