Dose correlation for thoracic motion in radiation therapy of breast cancer

This work investigates the dose correlation for deformed objects due to thoracic motion for radiotherapy treatment of breast cancer. An analytical model has been developed to reconstruct patient anatomy based on the assumption that the body will expand or compress proportionally during respiration. The patient geometry at any phase during a breathing pattern is reconstructed using the CT data taken at the inspiration and expiration phases and the breathing level which can be related to the measured chest wall motion. A correlation between the voxels in the inspiration (or expiration) geometry and the voxels in the reconstructed geometry at any phase of the breathing pattern is established so that the dose can be accumulated during a treatment. The method has been implemented for treatment planning dose calculation by interfacing with a Monte Carlo code. The patient geometry files for different phases of the breathing pattern are generated and the three-dimensional dose data are obtained from the Monte Carlo simulations. The final dose distribution is reconstructed from the dose data at different breathing phases based on patient’s breathing pattern associated with chest wall movements.