The primary purpose of this study is to determine if it is effective to take samples of fluid from the patient's brain tumor with a microdialysis catheter for Torisel measurement. The investigators are also doing it to learn if it is safe to do so. The investigators will use these samples to measure how much Torisel reaches the patient's brain tumor. The use of the microdialysis catheter to collect brain fluid is an FDA approved method. This catheter is already being used in patients who have sustained severe brain trauma from head injuries. The catheter itself is smaller in size than the standard needle that will be used to take the patient's biopsy. To obtain additional information Torisel will also be measured at the same time in the patient's cerebral spinal fluid by taking it from a catheter placed in the patient's cerebral spinal fluid producing spaces in their brain and in their blood from a catheter in one of their vessels.