The Feasibility of Fast, Four-Dimensional Computed Tomography-Based O-Ring Linac Plans for Stereotactic Body Radiotherapy in Patients with Poor Performance Status.

When compared to OARs both plans were acceptable per RTOG-0915 protocol, but significant differences were between Non-Gating and Gating plans. However, treatment delivery time of Non-Gating plans decreased by 47.9% than Gating plans. We verified the feasibility of fast 4DCT-based O-ring LINAC treatment for patients who cannot endure long treatment times due to poor performance status in lung 4D-SBRT. In further study, we will analyze dosimetric differences and treatment delivery efficiency considering tumor motion according to tumor location.