Biologic Association Between Metabolic Magnetic Resonance-positron Emission Tomograph (MR-PET) and Tissue Measures of Glycolysis in Brain Tumors of Infiltrating Glioblastoma Cells

The investigator will identify multiple (2-5) 5-8mm diameter spherical targets on GI maps for use in stereotactic pH measurement and biopsy acquisition. All biopsies are acquired for standard of care and according to standard of care procedures. A 13-gauge biopsy needle and plastic cannula will be inserted into the region of interest identified on MRI and PET. The biopsy needle will be removed, and the Softcell® pH probe, consisting of a 1.8mm diameter high quality glass tip and 1.6m long wire, will be guided down the cannula and inserted at least 15mm into the tissue. Recordings will be made for 1 minute to stabilize the reading, then the pH probe will be removed from the region of interest and placed into a saline vial for the next biopsy target. After the pH probe is removed, the biopsy needle will be placed into the cannula and standard-of-care biopsy tissue will be obtained from the same area where pH measurements were recorded.