Research| Computational Radiation Treatment Planning
Respiratory motions have a profound impact on the radiation treatment planning of cancer in the lung and adjacent tissues. In external beam radiation treatment, a lethal radiation dose is delivered through precisely conformed radiation to the target. The current radiation treatment paradigm, however, is largely based on an assumption that both tumor location and shape are well known and remain unchanged during the course of radiation delivery. Such a favorable rigid-body relationship does not exist in anatomical sites such as the thoracic cavity and the abdomen, owing predominantly to respiratory motions.
Previous approach to account for respiration caused target movement is to consider a larger planning target volume which covers a composite of 3D volumes of the moving target defined by the entire respiratory cycle. A relatively new approach is based on an image-guided technique which aligns and delivers the radiation according to a gated time and position or follows the tumor's trajectory during the respiratory cycle, to allow for a smaller and more conformal treatment volume. Hence, it is important to be able to predict the pattern of the lung motion as part of radiation therapy and know the tumor location.
Modeling Respiratory Motion for Cancer Radiation Therapy Based on Patient-specific 4DCT Data: Prediction of respiratory motion has the potential to substantially improve cancer radiation therapy. A nonlinear finite element (FE) model of respiratory motion during full breathing cycle has been developed based on patient specific pressure-volume relationship and 4D Computed Tomography (CT) data. For geometric modeling of lungs and ribcage we have constructed intermediate CAD surface which avoids multiple geometric smoothing procedures. For physiologically relevant respiratory motion modeling we have used pressure-volume (PV) relationship to apply pressure loading on the surface of the model. A hyperelastic soft tissue model, developed from experimental observations, has been used. Additionally, pleural sliding has been considered which results in accurate deformations in the superior-inferior (SI) direction.
Sponsors: NIH/NLM 5R01LM009362: 4D Visible Human Modeling for Radiation Dosimetry (2007-2011)
George Xu, PhD
Suvranu De, DSc.
Chengyu Shi, PhD
Jaesung Eom, PhD