Article

An Ounce of Prevention: Minimizing Exposure to Occupational Dose

In the course of a career in radiology, diagnostic imaging professionals run the risk of low-level exposure to ionizing radiation. Such exposure may increase the risk of developing cancer or cataracts. While cancer detection and treatment are standard fares in this field, the frequency of such diagnoses emphasizes the need for radiology department workers to take extra precautions in reducing occupational exposure.

What is the risk?

Energy in the form of ionizing radiation is released when atoms in electromagnetic waves disintegrate in reaction to unstable elements called radionuclides. There are more than 601 know radioactive materials found naturally in air, water, rocks, and soil. They account for normal background exposure as we inhale and ingest their radionuclides.

Additional exposure may be inherent in fields such as nuclear power generation. However, the most common source of human-made ionizing radiation today is in use of medical devices and techniques including X-ray, computed tomography (CT) scans, and fluoroscopic procedures.

Low doses of radiation, even when delivered over a long period of time, carry less risk than catastrophic exposure (such as a hazmat situation), because of the body’s ability to repair the damage. That is why the value of radiation exposure to the patient is offset by its usefulness in diagnostic evaluation or treatment.

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However, long-term effects – which can occur years after exposure – include increased risk of cancer. “Scatter radiation” describes secondary radiation to which personnel are exposed as the useful beam is directed at the patient. Scatter poses the greatest hazard to the technologist or others in (typically) a six-foot vicinity of the procedure.

Effective dose or ED is a yardstick of an organ or whole-body radiation exposure. It is measured in millisieverts or mSv. For the adult patient, the risk of fatal malignancy increases by about 0.05% per 10 mSv of exposure.2 The International Commission on Radiological Protection (ICRP) recommends a 20 mSv per year occupational effective dose limit (up to 50 mSv per year so long as the average over five years does not exceed 20 mSv).3 By comparison, the average occupational dose for radiation workers in the United States is less than 10 mSv per year.

Cardiologists rank the highest among physicians. Based on a 2014 report in EP Europace3, cardiologists are subjected to an annual personal ED approximately three times higher than nuclear physicians or radiologists. Fortunately, there are a number of steps the facility and the individual can take to minimize occupational dose, while still performing tasks effectively and efficiently.

Who is exposed?

The “As Low As Reasonably Achievable” (ALARA) principle ensures the patient gets the least amount of exposure possible. However, without the proper precautions in the occupational field, exposure can extend to any member of the medical team or volunteers who may happen to pass through the radiology department. This potential risk includes non-employee workers such as maintenance or construction.

That said, occupational exposure is primarily a concern for the technologist responsible for positioning the patient and creating the images, and radiation therapy technicians providing oncology treatment. Due to the continuous X-ray technique of fluoroscopy, exposure is significantly higher for staff handling those procedures.

How can occupational dose be minimized?

According to the World Health Organization1, “Medical use of radiation accounts for 98% of the population dose contribution from all artificial sources and represents 20% of the total population exposure. Annually worldwide, more than 3600 million diagnostic radiology examinations are performed, 37 million nuclear medicine procedures are carried out, and 7.5 million radiotherapy treatments are given.”

How can healthcare workers be protected from stochastic and deterministic risk in the face of those staggering numbers? With five essential actions:

  • Operator training – This encompasses familiarity with equipment controls and image processing selections, as well as departmental notification. The operator must utilize warning systems prior to the activation of radiation-producing equipment.
  • Time – As well as ALARA, it is important for healthcare personnel to limit time spent in proximity to the radiation source to avoid scatter.
  • Distance – A good rule of thumb is to double the usual distance between your body and the source of radiation. Avoid direct beam exposure. Whenever possible, do not manually hold a patient in position during the radiographic study. When manual support is necessary, the employee should wear a protective apron and gloves. In no case should any part of the healthcare worker be directly within the primary beam. In fluoroscopic procedures, they must be on the image intensifier side of the unit when it is in operation.
  • Shielding – The purpose of shielding is to reduce attenuation – amplitude of radiation. Shielding may be in the form of structural barriers (ideally a control booth) or mobile rigid shields. Aprons, vests, skirts, thyroid collars, and gloves should be worn by personnel. Face shields and leaded safety glasses with side shields reduce the risk of lens exposure and cataracts.
  • Awareness – Two personal dosimeters should be worn by personnel to monitor dose throughout. For cath lab workers, the International Commission on Radiological Protection2 recommends one worn at waist height under protective shielding. A second worn outside the apron at neck level indicates exposure to brain and eyes. Hand or ring dosimeters may also be worn to gauge finger dose.

Preventing exposure will continue

The New England Journal of Medicine named imaging among the top 11 medical developments of the past millennium. The Fellows and Members of the Royal College of Physicians of Edinburgh ranked imaging third in the Top 20 Most Important Medical Developments of the Last 50 Years.4 The benefits of radiography in diagnosis and treatment are undisputed, and the use of these techniques will likely continue to escalate. As more personnel enter the field, it becomes increasingly critical to protect their wellbeing for the viability of this important advance in medicine.

References:

  1. Ionizing radiation, health effects and protective measures. World Health Organization. https://www.who.int/news-room/fact-sheets/detail/ionizing-radiation-health-effects-and-protective-measures. July 1, 2019.
  2. Practical ways to reduce radiation dose for patients and staff during device implantations and electrophysiological procedures. Oxford Academic. https://academic.oup.com/europace/article/16/7/946/481012. July 1, 2019.
  3. Answer to Question #10031 Submitted to "Ask the Experts.” https://hps.org/publicinformation/ate/q10031.html# July 1, 2019.
  4. The Future of Medical Imaging. Hospital and Healthcare. https://www.hospitalhealth.com.au/content/clinical-services/article/the-future-of-medical-imaging-302384695#axzz5sRQdYy9O July 2, 2019.