Radiation Protection in Veterinary Medicine

The use of X-ray radiation in veterinary medicine started simultaneously with its spread in medical practice. Already in the 30s of the XX century, veterinarians could perform diagnosis using radiography, and for a long time this was the only radiation diagnostics technology available. Along with achievements of scientific and technological progress in veterinary medicine, other progressive methods of radiation diagnostics, such as computed tomography and radionuclide diagnostics, were introduced. The rapid development of the latest technologies using radiation sources over the past 15 years in all industries, including veterinary medicine, has led not only to the spread of radiation diagnostics, but also to the use of radiation therapy for cancer treatment of animals, interventional radiology, etc.

Changes in the society regarding the perception of animals played not the last role in the availability of radiation methods of diagnostics and treatment in veterinary medicine, as noted by N. Martinez and L. Van Bladel. Thus, today, cats, dogs and other four-legged pets are considered family members, and therefore we try to provide them with proper care. Animals are often of great breeding value, they are used as transport, labor, participate in sports competitions, entertainment. Therefore, they bring people a profit. Accordingly, they are taken care of, and, if necessary, treated, using sometimes very expensive and up-to-date technologies, including those associated with the use of radiation.

Thus, the issues of radiation safety and radiation protection in veterinary medicine have become as relevant as in medical practice. In this regard, national and international regulatory bodies started developing appropriate guidance documents. “Radiation Protection in Veterinary Medicine. Safety Guide” of the Australian Radiation Protection and Nuclear Safety Agency (2009) became one of the first such documents. The Association of Heads of the European Radiological Protection Competent Authorities (HERCA) adopted the “Guidelines on Radiation Protection Education and Training of Veterinary Professionals” in 2017. The world practice of using radiation in veterinary medicine was summarized by the International Atomic Energy Agency in published report “Radiation Protection and Safety in Veterinary Medicine” (2021)

According to the document, the feature of using radiation in veterinary medicine is that “Unlike the treatment of people, where in medical practice the use of radiation is limited to medical institutions, radiation in veterinary practice can be used beyond medical veterinary institutions.” This means that X-ray machines for the needs of veterinary medicine can be used not only in specially equipped premises of veterinary medicine institutions, but also, for example, on farms, stud farms, etc. This requires relevant knowledge and special training of a veterinarian. Sometimes such conditions require participation of animal owners or other persons in radiation diagnostics, as well as, of course, the use of special protective measures. Some Ukrainian veterinary clinics that conduct X-ray diagnostics also note that for its implementation, the presence of two people is required to immobilize the animal. This, in turn, requires optimal radiation protection of persons present with the animal during the procedure.

Another feature of using radiation in veterinary medicine is that the concept of “animals” is very broad and covers a large number of living beings, different in size, breed, species, temperament, etc. All this should be taken into account in assessing the received exposure dose, peculiarities of immobilization of the patient to obtain the most optimal and informative result.

To immobilize the animal and keep it in a certain position of the body necessary to obtain a high-quality image, sedatives, mechanical restraints are often used, or a veterinarian simply ask someone to hold the animal in the right position or control it so that it behaves calmly. This can be done either by the X-ray laboratory assistant (nurse), or by animal owner or person responsible for it. As a result, the dose load is applied to the upper limbs of these individuals. So, the use of protective gloves and proper collimation of the X-ray beam is required. Beam collimation precisely into the area under study avoids getting hands or other parts of the body of the person holding the animal under the X-ray beam. To keep the person safe also from scattered X-rays, the radiologist should indicate where it is safest to stand.

“Collimation is often neglected, but only due to the use of a collimator, the dose load can be significantly reduced. This should be taken into account by a veterinarian who has a permit to use X-ray and radiological equipment,” nuclear physicist, specialist in tomosynthesis, associate professor of the Department of Molecular Physics, Faculty of Physics, T. Shevchenko Kyiv National University, Serhii Senchurov advises.

To protect persons present during X-ray and radiological procedures for animals, special protective clothing is used. It should include vinyl lead aprons and/or gowns, gloves, thyroid protectors made of impermeable lead material, sometimes safety glasses with lead glass or lead plastic lenses and a hat.

According to the practicing medical physicist Oleksandr Novikov from the Mykolayiv Regional Center of Oncology, “in terms of radiation safety, from the viewpoint of our legislation, there is no difference for veterinary clinics. Diagnostic devices have the same characteristics, maybe slightly lower kilovoltage, amperage,” and personnel is protected in accordance with the requirements of the State Health and Safety Rules and Standards “Health-Based Requirements for Design and Operation of X-ray Rooms and X-ray Procedures” approved by Order of the Ministry of Health of Ukraine No. 294 of 4 June 2007, registered in the Ministry of Justice of Ukraine on 7 November 2007 under No. 1256/14523, Basic Health and Radiation Safety Rules of Ukraine approved by Order of the Ministry of Health of Ukraine No. 54 of 2 February 2005, registered in the Ministry of Justice of Ukraine on 20 May 2005 under No. 552/10832 and Radiation Safety Standards of Ukraine (NRBU 97) approved by Order of the Ministry of Health of Ukraine No. 208 of 14 July 1997.

Thus, in the use of radiological diagnostics for animals, radiologists are guided by radiation safety requirements established by these documents, i.e. radiological equipment in veterinary clinics, as well as in health care facilities, should be used in specially equipped rooms.

The access to the room for X-ray and radiological examinations should be restricted for unauthorized persons. The room should have relevant biological protection (in accordance with apparatus capacity, requirements for the basic characteristics of the building are established: area, wall thickness, layer of barium plaster, lead material, etc.; a doctor or laboratory assistant should control the X-ray machine from a separate room protected by a screen, and the glass in the window for observation should have a special composition). It is also obligatory to provide individual dose monitoring of personnel involved in X-ray and radiological procedures. All these measures are necessary to ensure safety of veterinary personnel and visitors.

In general, the limit of the dose received by personnel involved in X-ray and radiological procedures using radiation sources in veterinary medicine, according to document “Radiation Protection and Safety in Veterinary Medicine” and in accordance with the requirements established by Radiation Safety Standards of Ukraine (NRBU- 97) should not exceed 20 mSv per year, and the absorbed exposure dose rate in rooms near X-ray rooms and in areas adjacent to veterinary clinics should not exceed the established permissible levels.

It should be noted that the requirements for radiation source management applied in veterinary practice are the same as for those used in other areas.

A feature of X-ray equipment used in veterinary medicine, as already noted, is the possibility of using it outside clinics, as the animals can be so large that it is impossible to examine them by stationary equipment in the clinic. Therefore, in the case of examination of horses, cattle, etc., X-ray diagnosis can be performed in stables, cowsheds or in the open air with the help of portable (mobile) X-ray equipment.

 “The portable X-ray is a battery-powered generator and flat panel detector. It is possible to arrive, take pictures and leave. Even in the field, at least anywhere,” explains Serhii Senchurov.

However, it should be noted that carrying out X-ray diagnostics under such conditions also requires relevant radiation protection measures by establishing temporary zones of controlled access for unauthorized persons and protective measures for persons holding animals (owners, workers, grooms).

Thus, the temporary controlled access zone should be marked with signal cones, tape or portable signs. As in an equipped X-ray room, the distance and direction of the X-ray beam should be taken into account. For high-quality localization and collimation, an appropriate level of illumination should be provided to visualize the area of ​​the light localizer. The IAEA report describes in detail what this might look like in practice: “A controlled access area could be, for example, a stable in which the beam is directed at a brick supporting wall, the corridor should be blocked, and the light should be turned off. If the stable is wooden, access to the wall from the other side should also be controlled.”

Radiation protection of citizens under such conditions of radiography application is provided by a combination of three components: distance, installation of portable or mobile shielding and careful control of X-ray beam direction.

During X-ray diagnostic study in the open air, a place should be selected with enough space to provide a controlled access zone and to protect against unauthorized persons entering it. To reduce the risk of accidental exposure during the use of horizontal beams, lead screens are placed behind the X-ray photoplates (detectors).

During X-ray imaging procedures for horses, mounting plates are commonly used to calibrate the equine leg radiographs. They can also be used as plate holders for photoplates. To maximize the distance from the radiation source to the person holding the photoplate, plate holders with long handles should be used. During X-rays of the spine and chest, the IAEA recommends to use tripods, which eliminates the need to hold the photoplate by a person and protects him/her against high exposure doses applied in these examinations.

At the same time, in addition to radiation protection, participants of X-ray examinations should not forget about their own physical protection. For example, according to IAEA observations, during X-ray of the kneepan of the horse’s hind leg, the use of a plate holder for photoplates increases the likelihood of an anxious reaction of the animal. It will be safer to hold a photoplate by hand in a leaded glove and collimate the beam.

In general, the following conclusions can be made upon IAEA recommendations on radiation protection during radiological diagnostics in veterinary medicine:

1. Persons involved in X-ray procedures should be as far as possible from the primary X-ray beam and from the exposed animal to avoid exposure to scattering radiation. Avoid body parts getting under the primary beam.
2. Plate holders for photoplates with extensions or with handles, which will allow the person holding the plate to be farther than the primary beam during the procedure.
3. People within controlled access areas should wear protective clothing: lead aprons, thyroid protectors, lead gloves and glasses depending on the situation, etc.
4. Portable and mobile X-ray devices should be mounted on tripods and not held by hand; exceptions are regulated by national regulations.
5. If possible, mobile screens should be used, taking into account the associated hazards of close screen location to the animal under examination (the animal may be frightened and react).
6. The X-ray beam should be directed away from people and doors.
7. Unauthorized persons should be verbally warned before the X-ray diagnostic procedure.
8. Workers performing X-ray diagnostic procedures should have individual dosimeters; owners who hold the animal or help during the exposure usually do not need personal dosimeters.
9. Pregnant women are not allowed to participate in X-ray and radiological procedures.
10. All present should be informed about exposure and associated hazards before the procedure.

With regard to the use of radiation therapy, these procedures are carried out only in specialized clinics of veterinary medicine, and radiation protection measures for personnel during such procedures are generally similar to those used in oncological healthcare institutions.

In Ukraine, neither radionuclide diagnostics nor radiation therapy is used in veterinary medicine, although such cases are not unique in the world veterinary practice.

So far, Ukrainian veterinary medicine offers only X-ray diagnostic services using X-ray machines and computed tomographs. Moreover, veterinary CT examinations are carried out in a very small number of domestic clinics, because tomographs are expensive equipment for both state and private veterinary institutions.

Radiation diagnostics in veterinary medicine in Ukraine has system weakness that directly or indirectly affect radiation safety of personnel in veterinary clinics.

SNRIU has limited authorities to control the quality of diagnostic equipment for veterinarians. The confirmation of service quality: health and safety certificate for operation of X-ray room, training of personnel, including radiation protection measures is provided on a voluntary basis. Therefore, there are many clinics that provide not very high-quality services in radiation diagnostics.

There is an insufficiently responsible attitude towards personal dose monitoring and protection. If protective aprons are used mainly systematically, then protective gloves are not worn as often as they should.

Serhii Senchurov draws attention to another problem common in domestic veterinary practice. Since most animals have a relatively short lifespan (dogs 12-15 years, cats – up to 25), there is less likelihood to manifest long-term negative effects of exposure during their life. Accordingly, veterinarians tend to give high exposure doses to get clearer pictures. This means that personnel of veterinary clinics can receive higher doses. This is especially true taking into account the neglect of protective equipment and personal dose monitoring, which can take place.

In addition, often in veterinary clinics, the area of rooms for radiological diagnostics is limited. If the area is less than 30 m², i.e. it is impossible to ensure one of the radiation protection principles – distance.

And finally, it is necessary to remind that science does not stand still, therefore, radiation imaging and therapy methods will inevitably develop and find application not only in the public health system, but also in veterinary practice. As the IAEA report suggests, “the access of pet owners to the latest treatment and diagnostics methods, such as CT, scintigraphy, positive emission tomography, radiation therapy will increase,” but the desire to help the animal should in no way pose a risk for human health.

Uatom.org Editorial Board