Required target margins for image-guided lung SBRT: Assessment of target position intrafraction and correction residuals

IFV is dependent on several factors: immobilization device, treatment time, pulmonary function, and bodyweight. These factors are responsible for a significant portion of target margins with a mean IFV vector of 3 mm. Target margins of 6 mm or greater are required to encompass IFV in all dimensions when using four-dimensional CT with CBCT without respiratory gating or compression.