Abstract: A phantom for evaluating nondosimetric functions in radiation therapy installation having a patient couch and a gantry with a head thereon for generating a multi-leaf collimated beam, wherein the beam is directed toward the couch at an orientation dictated by relative orientations of the couch and gantry. The phantom comprises a base adapted for disposition on the couch, and a component mounted to the base for rotation in accordance with the relative orientations of the couch and gantry. The component incorporates a plurality of known geometrical structures corresponding in shape to the multi-leaf collimated beam. Upon imaging the component, nondosimetric functions may be evaluated by comparing the known geometrical structures with images of the structures and identifying discrepancies therebetween.