Patients undergoing a planned neurosurgical resection of diseased brain parenchyma.

Patients will undergo intra-operative microperfusion using Joanneum Research's cerebral open flow microperfusion (OFM) catheters, push and pull tubing, and MPP102-II pump. This process utilizes a probe (catheter) inserted into the parenchyma to collect analytes of any size and polarity from the microenvironment. The microperfusion pump peristaltically pushes and pulls perfusate with no net fluid-exchange when the pump heads are set at equal flow rates. As perfusate enters the tip of the microperfusion catheter, analytes are exchanged based on a gradient between the interstitial fluid and the perfusate. The sample is then recovered via the "pull" portion of the peristaltatic microperfusion pump, enabling constant sampling volumes and preventing loss of the perfusate into the tissue.

The duration is 60-80 minutes (dependent on the speed of progress resecting portions of the tumor without catheters)

Number of patients who develop persistent adverse events deemed related (possibly, probably, definitely) to the insertion or use of microperfusate catheters. Adverse events will be measured by CTCAE 5.0.

Number of patients for whom at least 1 specimen containing > 10 μL microperfusate is successfully collected from 2 or more locations.