BIOM-87. SODIUM (23NA) MRI AND CHEMICAL EXCHANGE SATURATION TRANSFER (CEST) IMAGING IN TYPICALLY DEVELOPING CHILDREN AND IN PEDIATRIC BRAIN TUMORS

Abstract In contrast to conventional 1H MRI, which primarily reveals water molecule distribution, with only indirect association with the physico-chemical microenvironment, 23Na (sodium) MRI and chemical exchange saturation transfer (CEST) have a more direct physiological interpretation, reflecting biochemical and physiologic changes in the cells of tissues, e.g. cell integrity and tissue viability allowing for direct assessment of cell membrane sodium ion channel function. Sodium concentrations are measurable by 23Na MRI and mobile proteins are measured with CEST [Amide Proton Transfer (APT) signal intensity]; when these are elevated, they have shown to be markers of tumors and proliferation. In this study, we acquired 23Na MRIs and APT in children with central nervous system (CNS) tumors and typically-developing (TD) pediatric controls. Sodium concentrations and APT signal were analyzed in regions of normal brain (brainstem, cerebellum, cerebral cortical grey matter, cerebral white matter, basal ganglia, hippocampus, thalamus) of TD controls and in pediatric brain tumors. The sodium concentration and APT in tumors were compared to homologous regions of the brains of TD controls. We hypothesized that sodium concentrations and APT signal will be greater in tumors compared to healthy brain in TD controls. We also analyzed the repeatability of subjects that received 23Na MRIs and CEST at two timepoints. Preliminary data demonstrates elevated sodium concentrations and APT signal in pediatric brain tumors (n = 5) compared to TD controls (n = 3). There was repeatability at two timepoints with consistent sodium concentrations and APT signal in TD controls (n = 3) and in pediatric brain tumors (n = 4). In conclusion, performing 23Na-MRI and CEST is feasible in pediatric patients with brain tumors. Future work will help answer the complex questions in monitoring treatment of pediatric patients with brain tumors: is there residual or recurrent tumor and differentiating tumor progression versus pseudoprogression.