Novel Optical Surface Image Guidance System for Beam-Gated Online Adaptive SBRT Delivery in Mobile Lower Lung and Upper Abdominal Malignancies

Motion during radiation therapy can be categorized as inter-fraction (changes in anatomy that occur between treatment days) and intra-fraction (changes that occur during the "beam on" window of treatment delivery). Inter-fraction motion is managed by adaptive radiotherapy (ART), the process of making changes in the treatment plan while the patient remains on the treatment table. This is now a standard-of-care therapy within Washington University's clinic. Intra-fraction motion is managed by gated and non-gated delivery techniques. Varian Medical Systems has integrated the necessary components into a CT-guided radiotherapy device (ETHOS). In the ETHOS, Varian has built a device that integrates on-board cone beam CT imaging capable of delineating target and organ-at-risk positions and a dedicated artificial intelligence-driven treatment planning system for inter-fraction motion management as well as a paired optical surface image guidance system for intra-fraction motion management. Although online ART is a standard-of-care practice in the clinic and has previously been shown to be feasible, use of surface-guidance for intra-fraction gating of abdominal and thoracic SBRT on ETHOS is novel. Therefore, in this study, the investigators propose to evaluate the feasibility and safety of using a novel surface guidance beam-gating system, incorporated with a CBCT-guided adaptive radiotherapy platform, to manage respiratory motion during delivery of CT-guided stereotactic radiotherapy. To best assess the utility of this technology to manage respiratory motion, the investigators will focus on disease sites that are highly affected by respiratory motion: upper abdominal or lower thoracic malignancies.