A multi-purpose object for calibrating, monitoring and/or tracking a patient in a treatment system and/or a treatment planning system is described, the multi-purpose object being made of transparent material and defining an internal space having one or more targets, wherein an upper surface is coated so as to define a pattern of transparent markings. The interior of the multi-purpose object can be back lit to present a high contrast surface image for a patient treatment, tracking or monitoring system.
