Principles of radiation safety

Biotechnology & Healthcare Radio Safety
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Radiation safety principles aim to limit exposure to ionising radiation for radiation therapy personnel, people affected by cancer and the general public. Wherever there is known risk of exposure to ionising radiation, health professionals must be guided by the ALARA (as low as reasonably achievable) principles of radiation safety for time, distance and shielding.8, 20 

Time

The less time spent near a radiation source, the less radiation absorbed. This is especially important for personnel such as radiation therapists and physicists preparing radioactive sources, and for nursing staff when caring for individuals who have a radioactive source in a body tissue or cavity. For inpatients, the nurse should restrict direct contact to 30 minutes per eight-hour shift.20

Distance

The inverse-square law states that radiation exposure and distance are inversely related. That means that as the distance from the source increases, the intensity of radiation decreases. To calculate exposure, the rule to use is that the amount of radiation exposure at one metre from the radioactive source equals the amount of radiation exposure at any distance from the source times the distance squared.21

Shielding

The type of shielding device used depends on the range of emission of the radioactive source. Standard shielding devices include lead aprons, thyroid shields, and eye shields. Rooms that house x-ray generating equipment are shielded using specified materials. Radioactive sources need to be transported by licensed personnel in lead containers.20 Brachytherapy procedures are undertaken in a specialised unit or ward with appropriate facilities, and individuals are generally isolated in a single room. 

Departments are designed with radiation protection and shielding at the forefront of planning. Radiation therapy workers are required to wear thermoluminescent dosimetry (TLD) badges, monitored by regulatory authorities to measure radiation exposure. Other radiation measurement devices such as Geiger counters are used to monitor areas where radioactive sources are used. Appropriate signage must be in place in the presence of any radioactive substance, and education and information provided to all individuals who may be impacted.8, 20

Spill management

In the event of a radiation incident, such as the loss of a source or a spill, appropriate procedures and notifications must be followed. These should be clearly outlined in the clinical environment as part of radiation safety and hospital policy. 

After ingestion of a radioactive substance, ‘spills’ generally refer to the loss of body fluid, either urine or vomit, and can be classified as major or minor. A significant amount of fluid loss (vomit or urine) within the first 24 hours would be defined as a major spill.22

Learning activities

Summarise how the ALARA principles are implemented in the care of individuals after the following treatments:

  • Iodine-131 swallow for thyroid cancer
  • Permanent seed implants in the prostate
  • Caesium-137 insert for cervical cancer using a remote afterloading device.
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