Lowering of the Interstitial Fluid Pressure as a Result of Tissue Compliance Changes during High Intensity Focused Ultrasound Exposure: Insights from a Numerical ModelE. Sassaroli, B. O'Neill 
The Methodist Hospital Research Institute, Houston, TX, USA
Interstitial fluid pressure (IFP) is elevated in tumors. Owing to this elevated IFP, the interstitial fluid velocity (IFV) is negligible throughout the tumor but significant near the tumor margin. Any therapeutic strategy that can lower IFP will improve drug convection within the tumor and decrease convection of drugs from the tumor margin. High intensity focused ultrasound (HIFU) has been shown to reduce the IFP and to improve the penetration of therapeutics in tumors. A mathematical model is presented simulating the effect of HIFU on the IFP and IFV. A reduction of the IFP as a result of HIFU exposure facilitates fluid convection and macromolecule distribution within the exposed area and reduces fluid convection and macromolecule wash out at its margin.