ISSN 2398-2985      

Radiography: radiation safety

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  • The basic principles of radiation safety must be observed when dealing with exotics despite the apparent low dose of radiation used and the difficult manipulation, positioning and immobilization of many of these patients.
  • Following rigid safety guidelines is essential when dealing with radiation which:
    • Is invisible.
    • Is painless.
    • Has cumulative effects.
    • Has latent effects, which may manifest later.
    • X-rays pose a safety hazard due to their biological effects on tissue (DNA damage).

Effects of ionizing radiation

  • Somatic effects - the direct effect seen on tissue immediately after exposure to a high dose (dose dependent) of radiation.
  • Rapidly dividing cells are most sensitive, and signs reflect body system affected, eg skin reddening or gastrointestinal disturbance.
  • Carcinogenic effect - tumors may be induced decades after the radiation exposure.
  • Genetic effects - mutations occurring in the chromosomes of germ cells in the ovaries or testes may cause effects in the offspring.
  • There is no threshold dose before cancer induction occurs and any dose of radiation carries some risks.
  • Safety is governed by The Ionizing Radiation Regulations 2017 (IRR17), which replaces the IRR1999.
  • Radiation safety governs risk to:
    • Radiographer.
    • Public.
    • Patient.

Sources of radiation

  • The radiographer may be exposed to radiation from a number of sources during exposure.

The primary beam

  • Contains high-energy radiation.
  • When positioning small patients, the hands are very close to the primary beam and subjected to a dose of radiations many times higher to that to which the body is exposed.
  • Methods of protection:
    • Collimate the beam tightly to the area of interest.
    • The light beam diaphragm should show the area of the primary beam, but this must be checked regularly to ensure it is accurate.
    • Avoid manual restraint and position the patient under sedation or general anesthesia.
    • If there is a clinical reason for avoidance of sedation or anesthesia, the individual restraining the animal has to ensure that no part of their body (not even hands with lead gloves) is in the primary beam.
    • The holder’s hands must be protected from scattered radiation (from above and below) by lead gloves.
    • When taking horizontal beam radiography, remember that the primary beam is harder to define and may pass through walls or windows. A cassette stand or another device to stabilize the radiographic cassette in a vertical position are required.
NEVER allow any part of the radiographer to be within the primary beam.

Scattered radiation

  • Lower energy radiation.
  • Easily attenuated and absorbed by the human body.
  • Produced when primary beam intercepts an object.
  • During an x-ray, the patient is the most significant source of scatter radiation.
  • Radiation safety aims at limiting exposure to radiations scattered by the patient.
  • May be travelling in any direction.
  • Methods of protection:
    • Minimize production of scatter radiation, eg use the lowest exposure setting to obtain a given mAs.
    • Radiographer should stand as far away from patient as possible (a long exposure cable permits this). Wear protective lead clothing, eg gloves, gowns and thyroid shields. This will nearly eliminate the absorption of scattered x-rays but will not attenuate high-energy photons in the primary beam.
    • Reduce number of radiographic examinations to a minimum.
  • The tube head:
    • Cracks in the lead lining may allow radiation escape in any direction.
  • Methods of protection:
    • Check integrity of lead shield regularly by taping x-ray film in envelope to tube head, making a few exposures and then exposing film (presence of blackened areas of film indicates radiation leakage).
    • Radiographer should stand as far from the tube head as possible.

The x-ray room

  • In most practices a room is designated as the x-ray room.
  • This room should be self-contained and have brick walls.
  • Ideally personnel in the room should be able to stand more than 2 m from the tube head during exposure.
  • If this is not possible a lead screen should be placed within the room.
  • Special considerations should be made if there is a room beneath the designated room!

Controlled area

  • The area around the primary beam where the average dose rate of exposure exceeds a limit set by regulations.
  • Defined by Radiation Protection advisor (RPA).
  • Usually 2 m radius from primary beam.
  • Controlled area must be demarcated and defined so practically easier to define x-ray room as controlled area.
  • If the x-ray machine is disconnected from its power source the room reverts to a normal room.
  • Warnings must be visible outside the controlled area in the form of lights or notices which are only displayed when the x-ray machine is in use.
  • Radiography should be performed on a lead covered table to:
    • Prevent penetration of the primary beam through the table.
    • To absorb scattered radiation.
The x-ray table must be at least as big as the area of the primary beam. For horizontal beam radiographs, enough distance should also exist between the radiograph tube (must be capable of 90° rotation) and the end of the x-ray table to allow radiographic exposure.

Protective clothing

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Patient restraint

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Radiation legislation

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Further Reading


Refereed Papers

Other sources of information

  • Health and Safety Executive (2018) Working with Ionising Radiation. Ionising Radiation Regulation 2017. Approved Code of Practice and Guidance. Website:
  • Reese V & Hein J (2011) Small Mammals. In: Diagnostic Imaging of Exotic Pets. Eds: Krautwald-Junghanns M E, Pees M, Reese S & Tully T. Schlϋtersche, Germany. pp 143-149.
  • Krautwald-Junghanns M E, Schroff S & Bartels T (2011) Radiographic investigation. In: Diagnostic Imaging of Exotic Pets. Eds: Krautwald-Junghanns M E, Pees M, Reese S & Tully T. Schlϋtersche, Germany. pp 2-35.
  • Widmer W R (2008) Radiation safety. In: Clinical Radiology of Exotic Companion Mammals. Wiley-Blackwell, USA. pp 2-16. 
  • Health and Safety Executive (online) Radiation. Website:

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