Midway through an afternoon fraction the linear accelerator drops the beam and shows an interlock that does not clear when it is reset. The patient is unharmed and still positioned on the couch, and department policy requires that the cause be established before treatments continue on that unit. Which action satisfies the required response to this equipment malfunction?

The required response is to have the physicist evaluate the unit, record the event in the patient chart, and file the equipment report. The physicist’s evaluation helps establish the cause before treatment resumes; the chart entry preserves information about the interrupted fraction and its handling, while the equipment report supports formal maintenance and safety follow-up. Having the physicist assess the interlock and document the event in the chart but omitting the equipment report leaves out that formal reporting pathway. Having the physicist assess the fault and file the equipment report but leaving the event out of the patient chart makes the clinical record incomplete. Documenting the event in the chart and filing the equipment report after a service engineer identifies the cause, without physicist assessment, omits the physicist’s evaluation of the unit and the fault’s clinical implications; service-engineer diagnosis does not replace that assessment. Exam caveat: an interlock that does not clear when reset is not proof that the fault is resolved, so follow department policy and establish the cause before treatments continue on that unit. Practical check: confirm the physicist has evaluated the unit and verify that both the patient-chart entry and equipment report are complete before treatments continue.