Radiation can directly or indirectly damage DNA, the critical target in cells. Direct effects occur when radiation interacts with and damages DNA. Indirect effects happen when radiation breaks down water into radicals that then damage DNA. While some cells die after radiation exposure, others may lose the ability to divide or retain abnormal chromosomes that can be transmitted to daughter cells. Radiation safety aims to keep radiation exposure as low as reasonably achievable through maximizing time, distance, and shielding between sources of radiation and personnel.

1. Radiation Interactions
 Damage may or may not occur
 Deposition of energy is very rapid
 DNA is the critical target
 Biologic changes occur only after a latent period

2. When Cells Are Exposed to Radiation
 Some cells die.
 Some cells lose the ability to divide.
 Some cells retain abnormal sets of chromosomes.
 Some cells transmit mutated chromosomes.
 Some cells contain gene mutations.

3. Direct Effects of Radiation
 Radiation interacts with and is absorbed by DNA.
 The DNA is the critical target and becomes an
abnormal structure.
 Critical Consequence is the transfer of the incorrect
genetic code to one of the daughter cells.

4. Indirect Effects of Radiation
 Water is the main component of the body.
 Ionization of the water causes an effect on the
critical target.
 This in turn will damage the DNA.

5. Indirect Effect
 Radiolysis of water.
 When water is irradiated, it breaks down into other
molecules (H+ & OH).
 This leaves a free radical of oxygen unattached and
ready to bind to the nearest molecule.
 Example is hydrogen peroxide (H2O2).

6. Exposure Terminology
 All personnel need to understand the terminology to
understand exposure reports.
 How much of a dose they may have received.
 Keep track when changing jobs.
 REM (Roentgen Equivalent Man) is the dose
equivalent that results from an exposure to radiation.
 The National Council on Radiation Protection and
Measurements (NCRP) states that the MPD-whole
body should not exceed 5rem or 0.05 Sv (Sievert).

7. Radiation Safety—All About X-Rays
 There are two main principles to be aware of
whenever radiation is a factor:
1. ALARA—dose must be kept
As Low As Reasonably Achievable
2. The way to do this is through
Time, Distance, Shielding

8. Time
 Be prepared!
 Plan each exposure carefully beforehand.
 Know the area of study.
 Know the anatomy of your patient.
 Measure properly.
 Set machine properly.
 Position patient correctly.
 Use knowledge of anatomy, behavior and positioning principles
to increase chance of success the first take.
 REDUCE RETAKES!

9. Distance
 Maximize operator distance from the primary beam.
 The intensity of the beam diminishes by the square of the
relative distance.
 For example: if you triple the distance factor, you reduce
exposure to one-ninth of the original amount.
 No extra personnel in the x-ray room.
 Use sedation or anesthesia with positioning aides
whenever possible.
 Use cassette holders with large animals.

10. Human Safety
 Use positioning aids and be creative.
 Avoid manual restraint when the exposure is
being made.
 Create an illusion (with aids) that the animal is held.
 Have everything ready prior to taking the
exposure

11. Restraint/Positioning Aides
Items include foam wedges, sandbags,
tape, troughs and even rope.

12. 12
Shielding
 The most effective
shielding is lead.
 It can be the metal
itself or expressed
as lead equivalency.
 Leaded glass
typically has a lead
equivalency of 1.58
mm.

13. 13
Personnel Protection
 Leaded eye glasses protect the
lens of the eye from scatter
radiation.
 The dosimeter in veterinary
clinics is worn attached to the
thyroid collar outside the apron.
 The thyroid collar must cover the
thyroid (wide enough and long
enough).
 The leaded apron must have a
shoulder strap either tied or
Velcro.
 The apron must also be secured
at the waist.
 The gloves must cover the
hands during the radiation
exposure.

14. Reduce Scatter Radiation
 There are several ways to reduce scatter radiation:
1. Make the kV just high enough to penetrate the body
part and satisfy the requirements of the film or
digital receptor.
2. Filtration.
3. Collimation.
4. Use leaded masks to absorb scatter.
5. Use the correct grid ratio for the radiography unit
that you have installed.

15. 15
Filtration
is located
within the x-ray tube. It
includes:
• The glass envelope of the
tube
• The oil within the housing
• The glass window of the
housing
is external within the
x-ray tube window itself. It
includes:
• Collimator
• 2.5mm Aluminum filter

16. 16
Collimation
 The collimation of any
radiograph should
extend to the region of
interest on the patient
and not beyond that
area.
 “Every image should
have a silver lining.”