Dosimetric Impact of Intrafraction Motion During RapidArc Stereotactic Vertebral Radiation Therapy Using Flattened and Flattening Filter-Free Beams

Even short-duration intrafraction shifts can cause significant dosimetric deviations during vertebral SBRT delivery, especially when using very high dose rate FFF beams and when the shift occurs in that part of the arc delivering high doses and steep gradients. The impact is greatest on the spinal cord and its planning-at-risk volume. Accurate and stable patient positioning is therefore required for vertebral SBRT.