S19-098 Quality Assurance (QA) Phantom for off-axis spatial accuracy for frameless single-isocenter Multitarget Stereotactic Radiosurgery Stanford researchers have developed and validated a quality assurance (QA) phantom that will facilitate the translation of a frameless volumetric modulated arc therapy radiosurgery technique. Shu-Jung YU Lawrie Skinner Piotr Dubrowski Dante Capaldi