 These studies will be a novel investigation in the use of brain microdialysis to measure TMZ concentration in the post-operative setting with combinational administration of Regadenoson and temozolomide. To minimize risks post-surgical resection or biopsy, patients will only receive temozolomide 150mgm2 twice, which is less than half the standard 5 day course administered during maintenance therapy for malignant glioma post radiation therapy. In addition, therapy will be given for only two days in the ICU setting, with minimal tumor toxicity anticipated with a suboptimal treatment dose over a short duration. The procedures involved with the insertion and removal of the dialysis probe can be performed with minimal injury at the time of surgery.18,19 Although insertion of the microdialysis probe could conceivably disrupt the BBB, this has not proven to be problematic, as demonstrated by rapid normalization of the BBB after placement, allowing for equilibration and minimization of artifact.20-22 Although it can be safely performed, microdialysis is nevertheless an invasive surgical procedure with a small risk of bleeding at the site of insertion and discomfort for the patient. The previous study which evaluated brain interstitium concentrations of TMZ evaluated dialysate samples from seven patients. All of the patients tolerated placement of the catheters and collection of the dialysate samples well, yet 1 patient developed several grade 3 and 4 neurologic adverse events whose etiologies remain unclear. All of the neurologic deficits improved without completely resolving. 