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

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.

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.

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.

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).

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).

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 Achievable2. The way to do this is through

Time, Distance, Shielding

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!

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.

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

Restraint/Positioning Aides

Items include foam wedges, sandbags, tape, troughs and even rope.

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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.

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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.

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.

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Filtration

• Inherent 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• Addition is external within the

x-ray tube window itself. It includes:

• Collimator• 2.5mm Aluminum filter

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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.”