Room: Exhibit Hall
Purpose: To simulate large deformation of breast tissue during HDR treatment of Accuboost (Advanced Radiation Therapy LLC, Billerica, MA). During the treatment, the patient's breast was compressed by the mammography system for accurate localization of the target region. A biomechanical model was established to solved by the finite element method. The displacement field result can be applied to obtain 3D dose distributions of the uncompressed breast.
Methods: A CIRS Stereotactic Needle Biopsy Training Phantom (CIRS, Norfolk VA) was scanned on a CT simulator. The phantom is made from a proprietary gel with a physical consistency similar to human tissue, and possesses solid masses which can be used for validation purposes. The CT images were then segmented and a surface mesh file was generated and imported into the finite element software FEBio (University of Utah). The breast tissue is modeled as the Hyperelastic Neo-Hookean material which is an extension of Hookeâ€™s law for the case of large deformation. The Youngâ€™s modulus and Poissonâ€™s ratio were assigned to a model based on literature. The boundary conditions were applied to solve the model. The resulted displacement field can then be used to map the dose on the breast from compressed status to uncompressed status. This way, the 3D dose distribution of the Accuboost breast treatment in uncompressed breast can be obtained.
Results: The breast phantom was modeled as homogenous material to simplify the modeling. A 40% of contraction in superior and inferior planes of the breast was produced as a result of breast compression. Further validation of the biomechanical model will be the next step in this research.
Conclusion: The biomechanical modeling is a feasible tool to map the deformation of breast. Different material properties and boundary conditions can be further studied to find a more accurate simulation.