EMERGENCY SWITCHES

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Emergency switches are designed for safety purposes. They control both the beam and the mechanical systems in the treatment room. They should always be functional. All Linac operators should know the location of emergency switches and how and when to activate them.

Locations of the emergency switches in a linear accelerator room:

  • On each side of the stand
  • On each side of the treatment couch
  • On each wall of the bunker
  • On the entry to the maze
  • On the machine console in the control room
  • On the power supply to the linear accelerator (in the control room).
  • Emergency switches in a linear accelerator room are activated when:
  • There is a power failure.
  • There is fire outbreak.
  • The treatment beam fails to terminate.

Equipment malfunction.

  • The linear accelerator produces external radiation that is higher than the pre-set level.
  • There is someone in the treatment room when the linear accelerator is active.
  • There is a danger to the patient and has to be removed out of the treatment room immediately, that is:
  • If the patient has an acute medical event.
  • If there is a dangerous substance within the bunker.
  • If the gantry or treatment head is about to collide with the patient.

Procedures to follow when the above incidences happen:

Power failure

  • Terminate the beam and record the reading on the backup counter at the time of power failure.
  • Remove the patient out of the treatment room.
  • Calculate the remaining dosage (in monitor units) to complete the treatment by subtracting the backup counter reading from the prescribed dose.
  • Once the power is back, perform the daily checkout procedure to verify proper operation of the equipment.
  • Return the patient to the treatment room to resume treatment.
  • A medical physicist should verify the remaining dose to be delivered.

Fire outbreak

  • Press the Emergency button.
  • Turn off the main circuit breaker and call the emergency team.
  • Remove the patient from the treatment room.
  • If the fire occurs when the beam is on, record the following: the prescribed dosage and the backup counter reading at the time of failure.
  • Calculate the remaining dosage by subtracting the backup counter reading from the prescribed dose.

Treatment beam failing to terminate

  • Press the beam off button and switch the enable/disable key to disable mode.
  • If the beam is still ON press the emergency button near the console and turn off the circuit breaker.
  • Remove the patient from the treatment room.
  • Record the backup counter reading and calculate the remaining dose.
  • Call a physicist or an engineer to inspect the equipment
  • The accelerator should not be used for treatment until the problem has been solved.

Equipment Malfunction

  • Terminate beam and record the backup counter reading at the time of failure.
  • Remove the patient from the treatment room.
  • Call the engineer to rectify the problem
  • Calculate the remaining dose and call the medical physicist to verify.

Accidental Radiation Exposure

In case the linear accelerator starts emitting higher radiation than the pre-set values, a medical physicist or a Radiation Safety Officer should be informed immediately. 

References

LSUHSC-Shreveport Radiation Oncology. Linear Accelerator Emergency and Safety Procedures. 

OzRadOnc. Emergency Shut-Off. Retrieved from www.ozradonc.wikidot.com on16/1/2019.

Home > Radiation Protection and Quality Assurance > Equipment Use & Quality Assurance > Quality Control Procedures > Emergency Switches

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