Emily Her
BTech (Hons)
Medical Physicist
Clinical Physics
Medical Engineering and Physics
Royal Perth Hospital Bentley Group
Background
Mini C-arm fluoroscopy is used to assist the surgeon to implant metallic wires and plates when re-setting broken bones. It’s mostly used for repairing bones in the extremities of the body. The doctor can view what he/she is doing during the operation by fluoroscopic X-ray imaging.
Staff are protected from the main primary beam passing through the patient. But there is a measurable radiation exposure scattered in all other directions around the patient. Staff close to the patient during the surgical procedure will receive some of this ‘scattered radiation’ during the fluoroscopic X-ray exposure.
Staff radiation safety concerns
One of the Royal Perth Hospital nursing staff , involved in these C-arm fluoroscopic procedures, had read an article which claimed nurses and doctors had received harmful levels of X-ray to their eyes from carrying out these procedures. To obtain some expert advice on how safe mini C-arm fluoroscopy was, the nurse consulted the hospital’s medical physics group.
Medical physics radiation safety experts
The medical physicists at Royal Perth Hospital have the responsibility to ensure that patients and staff have adequate radiation protection for all forms of ionising radiation used in hospitals.
This includes safety aspects such as:
- Design and testing of radiation shielding;
- regular performance tests of all radiographic equipment; and
- advising and training staff proper radiation safe practice and levels of danger.
What was the radiation risk?
To obtain quantitative measurements and to demonstrate the level of risk of X-ray eye damage to staff involved in the mini C-arm fluoroscopic procedures, the medical physicists positioned a tissue-equivalent phantom on the operating couch and measured the scattered X-ray radiation. They recorded the dose rate at positions where the surgeon and assistant normally stood.
To simulate what increased affect scattered dose from metal implants may have, an aluminium plate was inserted in the phantom and the measurements repeated. The difference in scattered radiation was insignificant.
From many world publications, the International Commission on Radiological Protection[1] has recommended a maximum annual dose that would avoid radiation damage to the eyes.
To simplify the ICRP annual dose limit prescribed for this case, the estimated dose rate to the surgeon’s eyes and assistant close would be equivalent to 210 working hours or 2500 five-minute procedures in one year of work.
What was the outcome for the staff?
The fluoroscopy staff agreed that:
- their X-ray exposure workload was far less than 2500 five-minute procedures;
- the level of dose rate they received, would not cause eye damage; and
- there was no reason for concern.
The staff received a formal report. Their concerns were put to rest.
Concluding remarks
This example highlights the importance of hospital staff having ready access to medical physics expertise for advice.
There are a wide variety of radiation safety issues that occur in a big hospital complex. As the Hospital’s ‘Radiation Safety Officer’, the medical physicist is the ‘friendly policeman’ of radiation safety. They are there to find unsafe radiation situations and fix them, provide learned advice and apply their specialist radiation physics expertise in the hospital environment.
Above all, the medical physicist is expected to effectively communicate to hospital staff, clearly describe procedures of best practice and explain the associated occupational radiation risks. The goal is to keep radiation levels to a minimum and maintain adequate staff interaction to avoid unnecessary fear of radiation.
Emily Her, 24 January 2020
Acknowledgement: My thanks to Dr John Burrage for his input during this project.
[1] ICRP Publication 103. Ann ICRP 2012
