Spatial Measurement of Tumor Interstitial Fluid Pressure: A Method to Measure the Interstitial Fluid Pressure

Interstitial Fluid Pressure or IFP is the force exerted by the fluid in the spaces between the cells in a tissue. First, anesthetize a tumor-bearing mouse with 2% isofluorane mixed with oxygen and immobilize it on the computed tomography or CT-IFP robot platform. Now, inject in the lateral tail vein of a mouse with liposomes encapsulated with a contrast agent to visualize the tumor. Return the animal to its cage and let it recover.

Between 48 to 72 hours post-injection, secure the anesthetized mouse on the CT-IFP platform and select a few evenly spaced positions on the tumor for measuring the IFP. Next, flush the IFP system needle with a heparin saline solution before insertion. Bring the needle on the selected position and insert it within the tumor tissue.

Now acquire images at all positions and measure the IFP using the software. The IFP in the tumor is usually high due to its dense nature, abnormal blood vessels, and defective lymphatic system. This may lead to the accumulation of liposomes in the tumor periphery. In the following protocol, we will demonstrate the technique to measure the IFP in a solid tumor.

To measure the IFP, tape the animal on the CT-IFP robot platform, su