A system includes presentation of a view of portions of structures that would be intercepted by a path of radiation during radiation treatment from a perspective of a location. The radiation enters an entry surface of a radiation-focusing lens, exits an exit surface of the radiation-focusing lens, and is substantially focused on a focal area. The location is located such that a plane perpendicular to an axis of the path, intercepting the exit surface, and positioned between the entry surface and the focal area would be located between the location and the lens.