Clinical Assignment 7 Physics Question 3

All staff who are involved in the treatment of patients with radiation should have an understanding of procedures to be undertaken should a radiation incident or accident occur.

Mr. Brown has been prescribed a single fraction of 9 Gy to the prostate using HDR brachytherapy. His treatment has just been completed and you are asked to remove the implant. As the radiation therapist enters the HDR treatment room, he notices that the reading on the hand held radiation monitor is high and asks you:

“Do you think the source is back in the safe? What shall we do?”

In temporal sequence, describe the immediate actions to be taken to ensure patient and staff safety.

Notes to the trainee: You will find it useful to discuss the described scenario with a medical physicist (or the designated radiation safety officer) in your department. You should consider which equipment you would expect to have available in the treatment room for such emergencies.

The 'notes to the trainee' section was really helpful here. Find your brachytherapy safety officer, if your site has one, and ask him what they do. This question was a bit unlikely in Canberra as we have two detectors built into the room: One attached to the HDR afterloader unit and the other completely independent. So unless both were malfunctioning…

At Canberra, the steps are:

  1. Confirm the presence of the source outside of the safe on the other radiation detectors. If both are reading negative, confirm the accuracy of the survey meter (eg. try it outside the room first)
    • This helps staff radiation by confirming the presence of radiation inside the bunker before stepping into it.
    • AAM - remember that you can't just shut the door and call some one. The patient is in there and being potentially irradiated, so you have to sort this ASAP.
  2. If malfunction of the HDR afterloader is confirmed, hit the emergency button on the staff console
    • This is important for both staff and patient safety. Staff are protected by remaining out of the bunker. The patient is protected by prompt removal of the source. Patient protection is very similar for each of the steps involved (eg. remove source from patient).
    • AAM - this is important, minimal staff in the room, get the patient out ASAP without the source. This might end up being painful for the patient but unavoidable.
  3. If the source remains inside the patient, staff will need to enter the room.
    • At Canberra the radiation therapist times staff within the room. No more than two minutes are permitted.
    • Whilst in the room, staff utilise the ALARA principle of distance when dealing with the source.
    • AAM - one issue here is that there needs to be very clear communication between the time keeper and the people in the room, as well as some one providing instructions on what to do (same as an arrest); distance ALARA is likely to be irrelevant in that the removal of the apparatus is a hands on affair.
  4. Hit the emergency button on the HDR afterloader
    • This has a similar function to the control button, but in the event of the signal from the control room malfunctioning (everything else seems to be in this scenario!)
    • AAM - should this be the second thing after confirming radiation exposure?
  5. If unsuccessful, staff can wind the source back into the safe manually by using one of the cranks on the HDR unit
    • The ranks are manually wound handles. They keep staff away from the source.
    • AAM - they can stand on the other side of the safe; should you try and wind the source or remove the patient first?
  6. If the source is unretractable, then the HDR applicator must be removed and placed in a lead pot
    • The lead pot is kept inside the brachytherapy bunker at all times. It can be closed with a lid.
    • Removal of the applicator is the responsibility of the radiation oncologist (or the registrar!) - why?
    • The applicator / source form a closed system and removal of the applicator will remove the source in almost any conceivable scenario.
  7. If the source STILL remains in the patient, then it must be surgically removed as an emergency.
    • This is the final step.
    • It must be done as quickly as possible to reduce the dose received by the patient
    • Surgeons, anaethetists and other theatre staff will be exposed to significant levels of radiation, which is why this is the last step taken.
    • AAM - good, but remember that the pellet could be in the vagina or the uterus, one can be removed without theatre (just a speculum and long forceps).
    • AAM - what will you be telling the O&G/anaesthetist/nurses who blanch and refuse to be exposed to radiation????

Given that this question asks for 'immediate action' I presume it doesn't want to know about other actions taken, such as reporting to the radiation safety officer or (in Canberra) an electronic risk summary. AAM - certainly the RSO has to be made aware as soon as the incident starts.

How do other departments handle brachytherapy incidents?

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