4D dynamic simulation of patients undergoing radiotherapy

Recently with the advent of linear accelerators equipped with on-board x-ray imagers and advanced medical imaging technologies, image-guided radiotherapy (IGRT) has been routinely used in the radiotherapeutic management of cancers worldwide. However, as ionizing radiation is involved, the radiation exposures from the medical imaging procedures are of major concerns to the cancer patients undergoing radiation therapy. In this work, we propose to develop a realistic yet flexible 4D digital phantom based on patient CT anatomy and time-tagged CT information for dynamic estimation of organ doses due to external ionizing radiation. All the external ionizing radiation involved in the radiotherapy of cancer patients will be modeled consistently and systematically with Monte Carlo multiple source models. Our studies indicated that it is feasible to build a 4D patient-specific digital phantom suitable for Monte Carlo radiation transport simulation. With a digital phantom for each patient, an accurate estimation of the organ doses in 4D will be made possible, which will contribute to a better tumor control due to the detailed knowledge of dose distributions in patient anatomy not only spatially but also temporally. The proposed 4D phantom will also allow for deformable dose registration for adaptive radiotherapy.