A non-sterile device intended to be used to position and immobilize a patient’s head for reproducible positioning during serial imaging studies, radiation treatment planning, or stereotactic radiotherapy (SRT) and stereotactic radiosurgery (SRS), on all parts of the brain, head, and neck. It is in the form of a custom-made bite assembly that can be used with an arch head frame or a thermoplastic mask. This is a reusable device intended for single-patient use.