Because any exposure to ionising
radiation can be harmful, the potential hazards of radiation must be considered
against the benefits derived. The objectives of radiation protection for
workers in the field are:
1. To prevent
clinically significant radiation-induced effects by adhering to dose limits
.
2. To limit
the risk of cancers and heritable effects .
In order to achieve these objectives,
two principles have been devised:
1.
ALARA – limiting exposure of radiation workers to a level As Low As Reasonably
Achievable
2. MPD (maximum
permissible dose) – this refers to the maximum amount of absorbed radiation
that can be delivered to an individual as a whole-body dose or as a dose
to a specific organ and still be considered safe. The term safe in this
context means that there is no evidence that individuals receiving the
MPD will suffer harmful immediate or long-term effects to the body as a
whole or to any individual organ or structure of the body. The maximum
permissible dose is cumulative throughout an individuals lifetime.
ALARA objectives are achieved
by sensible adherence to the following practical considerations:
1. Minimise
the duration of exposure by good radiograpic technique.
2. Use chemical
restraint, positioning and restraining devices to control animals
and to avoid the use of personnel.
3. Confining
the area irradiated to the region of interest avoids excess scattered radiation
4. Increase
the distance of the individual from the radiation source (see
inverse square law), remembering that 
protective
barriers only guard against scatter radiation, not the effects of the primary
beam.
5: When
radiographing large animals with a horizontal x-ray beam, particular care
must be taken to confine the beam to the x-ray cassette and ensure that
there is no-one in line with the main x-ray beam-especially in adjacent
areas or rooms.
6. Use cassette
holders for the x-ray film when radiographing large animals.(above)
7. Shielding:
use protective barriers, lead gloves and aprons(left) between the individual
and the radiation source,and always wear a film badge under the
protective apron, at body level, to monitor the radiation dose.(right)