TMIC-12. MODELING AND ESTIMATION OF TUMOR INTERSTITIAL FLUID PRESSURE AND NORMAL TISSUE COMPRESSION USING HYPERFOAM THEORY AND FINITE ELEMENT TECHNIQUE Narsollah Goudarzi1, Reza Faghihi1, James Ewing2, Brent Griffith2, David Nathanson2, Ali Arbab3, and Hassan Bagher-Ebadian2,4; Shiraz University, Shiraz, Fars, Iran; Henry Ford Hospital, Detroit, MI, USA; Georgia Regents University, Atlanta, GA, USA; Oakland University, Rochester, MI, USA Recent studies have shown that mechanical stresses and interstitial fluid pressure (IFP) gradients of solid and embedded tumors directly contribute to their aggressiveness and response to therapy. Thus, studying and modeling these parameters play an important role in diagnosis and therapy of solid tumors. In this study, a mathematical benchmark was developed based on the IF flow, conservation laws for mass and momentum, and hyperfoam theory to model a physiological system containing a solid tumor surrounded by normal tissue. Using a finite element technique, IFP and tissue compression weremodeled fora solid tumor with diameterof 20 mmsurroundedbynormal tissue with thickness of 20 mm. It was hypothesized that the normal tissue can experience elastic and plastic phases during the compression. Hyperelastic parameters of white-matter were recruited in the hyperfoam strain energy function for modeling the distribution of tumor pressure load to its surrounded normal tissue, tumor, and normal IF velocities as well as displacement, stress, strain, and Young modulus of the normal tissue. Results imply that the IFP is highest and almost uniform inside the tumor and due to the small IFP gradient inside the tumor, the IF velocity is almost zero inside the tumor but high in its adjacent normal tissue while it drops abruptly in the normal tissue. Normal tissue displacement is high close to the boundary of the tumor and deceases with distant from tumor boundary. Stress distribution and Young’smodulus in normal tissue arealmostuniform while the hydrostatic strain is highclose to the boundaryof the tumorand decreases smoothly with distant from tumor boundary. This pilot study provides a practical benchmark for characterizing the mechanical properties of embedded tumors and their surrounded normal tissues that are considered as useful information in studying the embedded tumors in research and clinic. Neuro-Oncology 17:v221–v225, 2015. doi:10.1093/neuonc/nov236.12 Published by Oxford University Press on behalf of the Society for Neuro-Oncology 2015.