Understanding Radiation Safety in a Veterinary Hospital

Posted on September 20, 2012 by Michael Q. Bailey, DVM, DACVR

I often receive questions about the safe use of X-ray equipment in veterinary hospitals. X-ray units, both the large general units and the smaller maneuverable dental units commonly found in veterinary hospitals, produce a diagnostic X-ray that, if not used properly, can also cause health risks for associates. The informed questions we need to ask are: where is the radiation produced, where does the radiation go, and how do we reduce exposure to non-diagnostic radiation?

The X-ray photon, not surprisingly, is produced in the X-ray tube located in the tube head. We all know this, but what is not well-known is that there are three radiation sources of concern: the primary beam (radiation of the diagnostic beam that exits the collimator); the secondary radiation that escapes the tube head by other than the collimator; and the scattered radiation that derives from the patient. In all cases, we want to use the guiding principles of “As Low As Reasonably Achievable” (ALARA). These should always be followed to minimize radiation exposure to the hospital team, the veterinary patient, as well as to the general public.

The three principles of ALARA are: distance, shielding and time.

Distance should always be optimized.

  • The operator of X-ray units must stand at least 6 feet (2 meters). (Please review your state requirements, which may be greater). By doubling the working distance from an irradiated patient from 3 feet (1 meter) to 6 feet (2 meters), the radiation to personnel is reduced roughly to only 25 percent. Every time you double the distance, radiation is reduced 75 percent: This is the inverse square law.
  • The X-ray beam must be angled so that neither personnel nor the general public are in the primary beam.
  • The primary beam should never be directed toward an entrance door or other non-protected areas.

Shielding: If the benefit of distance is not achievable, then utilization of shielding such as standing behind approved barriers or, if necessary, the use of personal protective devices such as aprons, gloves and thyroid shields is warranted.

  • “Scatter radiation” is produced inside of the irradiated patient. The more hydrogen present—such as water or fat—the more scattered radiation produced.
  • If using physical restraint, i.e., holding a pet in the X-ray suite, protective devices must be used to protect associates from the source of the scattered radiation (the patient).
  • It is important to remember that protective devices are designed to protect personnel from low energy scattered radiation, not from the primary beam.

Please note: The protective gear does not shield against the primary beam. When you see a white outline of a glove the image receptor (film or detector) is protected by three layers, two layers of glove and one layer of hand. Your hand is shielded but not protected by one layer!

Time: Always minimize time near an X-ray source by:

  • Using the shortest exposure time possible
  • Obtaining the fewest images needed for a diagnostic study by planning the best images
  • Utilizing accurate technique charts
  • Processing film using optimized time-temperature compensation methods and fresh chemistry
  • Using higher speed film
  • Asking questions if you are not sure so you get it right first time

For dental X-ray units: X-ray energies of greater than 60Kvp are agreed upon by European and U.S. regulatory bodies as the optimal operating potential for intraoral imaging, to maintain contrast while reducing radiation absorption by soft tissue and bone.

About Michael Q. Bailey, DVM, DACVR

Michael Q. Bailey, DVM, DACVR, joined Banfield as a radiologist in 2009. He is a graduate of Tuskegee University/ School of Veterinary Medicine, and completed his internship and residency at Michigan State University. He has taught at Tuskegee University, Michigan State University and was tenured faculty at The Ohio State University. Dr. Bailey is also the recipient of several teaching awards, including the Norden-Pfizer Distinguished Teaching Award. He and his wife Terri have two sons, and a yellow Labrador. View all posts by Michael Q. Bailey, DVM, DACVR →


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