A patient with dementia becomes agitated during setup, tries to sit up, and grabs at the couch rails. To keep her still for the beam, a therapist buckles a soft belt across her chest and thighs and the fraction is finished. The department later reviews the event under its patient safety policy. Which classification applies to what the therapist placed on this patient?

Purpose decides the label here, not the material or how snug the strap is. A restraint is any device or method that limits a patient's freedom of movement in order to manage behavior, and facility policy then calls for authorization, assessment, monitoring, and careful documentation before and while it is used. An immobilization device serves the prescription instead: it belongs to the plan and exists to reproduce the treatment position accurately at every fraction. The immobilization reasoning fails because it looks at the object rather than at why it was applied; this belt was buckled to control agitation, not to reproduce a setup. The implied-consent reasoning fails because agreeing to be treated is not agreeing to be strapped down, and physical control without authority can raise an assault or battery question. The safety-support reasoning fails because ordinary repositioning never justifies a restrictive device, and one log note does not satisfy the assessment, authorization, and monitoring that restraint use demands. Exam caveat: facilities define these terms operationally, so check whether the device is part of the prescribed setup or a response to behavior. Practical check: ask whether the strap holds her for accuracy or for control, and if it is control, follow restraint policy first.