Radiation shielding must be taken into consideration in all circumstances
Due to changing imaging environments and situations, attention must be paid to the operating premises and quality of operations.
Structural shielding of examination facilities
The imaging of small animals is usually done in a separate radiation-shielded examination room. In these examinations, the radiation beam is almost always directed downwards. In this arrangement, sufficient radiation shielding for the walls, doors and observation windows and their frames is usually created by a width of building material that corresponds with the radiation shielding of 1 mm lead, 10 cm concrete or 13 cm brick (concrete density 2.35 g/cm3, brick density 1.80 g/cm3). If there are facilities in the direction of the primary radiation beam that will be occupied by people during examinations, shielding that corresponds with a 2 mm layer of lead or 15 cm layer of concrete is usually sufficient.
When imaging large animals, such as horses and their limbs, the radiation beam is usually horizontal. When imaging indoors, such as in a stable, the radiation shielding of the walls between the space in the immediate direction of the radiation beam and the examination room must correspond, at a minimum, with the protection of a 2 mm layer of lead or 15 cm layer of concrete, if it is not possible to ensure that there are no persons in the room during the examination. The examination room must have sufficient space and a suitable shape to enable X-ray operations.
The calculation formula for the radiation shielding of X-ray examination rooms are presented in Guide ST 1.10.
X-ray examinations in open spaces
When imaging is carried out in an open space, such as a horse race track, and moveable shielding walls are not available, there must be dozens of metres of unoccupied empty space in the direction of the radiation beam. Whenever possible, a cassette holder with a long arm or a separate cassette stand must be used for imaging. A fabric pocket that is attached around the animal behind the imaging site can be used in place of a cassette stand. If the X-ray equipment is portable, it must not be held in hands or lap during the imaging but must be placed on a suitable stand.
If the imaging voltage is over 100 kV or if the equipment is used for fluoroscopy examinations, the need for shielding may be greater than described above. More precise requirements are placed when the safety licence is issued.