NIMG-30. DEUTERIUM METABOLIC IMAGING (DMI) SHOWS A STRONG RELATION BETWEEN TUMOR GRADE AND GLUCOSE METABOLISM IN PRIMARY BRAIN TUMORS

Abstract BACKGROUND Metabolic imaging using FDG-PET is a key component of disease management in many cancers outside of the brain, but in brain tumors, it often shows low tumor-to-brain contrast because of high background signal from normal brain. Deuterium metabolic imaging (DMI) is a new 2H magnetic resonance spectroscopic imaging-based technique that when combined with administration of 2H-labeled glucose can provide high tumor-to-brain image contrast because it can detect downstream metabolism instead of only glucose uptake. In this observational study, DMI of glucose metabolism was performed in 22 patients with primary brain tumors of different grades, and at different disease stages. METHODS DMI data were acquired using a 4 tesla MRI scanner after oral administration of 0.75g/kg of [6,6’-2H2]-glucose in water. Metabolic maps were generated of 2H-labeled glucose, glutamate+glutamine (Glx), lactate (Lac), and Lac/(Lac+Glx), a proxy for the metabolic shift observed in many cancers known as the Warburg effect. Volumes of interest (VOI) based on contrast-enhancing and non-enhancing tumor regions were created using clinical MRIs and combined with DMI maps to generate tumor-specific values for Lac/(Lac+Glx). Eta-squared was calculated using tumor grade and Lac/(Lac+Glx) as independent and dependent variables; data are reported as mean±SD. Results – Tumor-to-brain image contrast for Lac/(Lac+Glx) was 2.57±0.93 for grade 4 (n=14), 1.74±0.75 for grade 3 (n=6) and 0.94±0.28 for grade 2 lesions (n=3). Lac/(Lac+Glx) was 0.36±0.13 for grade 4; 0.19±0.049 for grade 3; 0.09±0.042 for grade 2 lesions; and 0.14±0.043 for normal brain. Eta-squared between tumor grade and Lac/(Lac+Glx) was 0.52. CONCLUSIONS VOI-based analysis showed a high dependence of metabolism-specific image contrast to tumor grade. The apparent relation between lesion grade and Lac/(Lac+Glx) indicates the potential of DMI to complement anatomical MRI and possibly provide a valuable biomarker indicating active tumor tissue and could improve evaluating disease progression.