Breakaway safety feature for an intra-oral cone system

With an increasing number of high energy accelerators in operation, intra-oral electron radiotherapy is likely to become a more widely-used modality in the treatment of lesions of the oral cavity. However, there is one potential problem associated with this modality which concerns patient safety. There must never be any uncontrolled movement of the couch or gantry while the cone is in the patient's mouth, otherwise serious consequences could occur. In an effort to overcome this problem, a set of cones previously constructed by us for use in intra-oral electron radiotherapy has been modified to include a breakaway safety feature. This modification consists of separating the plate into which each of the treatment cones screws, into two pieces, the dividing line being in the shape of a cone frustum flaring out in the upward direction. A set of four spring plungers projecting into a notch on the inner ring prevents the cone from being pushed upwards without the application of an upward force. The amount of force required to push the cone upwards can be changed by adjusting the pressure of the spring plungers.