Radiation Safety Terms & Definitions for Medicine Students

Examples of cells most sensitive to radiation

- Epithelium

- Hematopoietic cells

- Cells lining small intestine

- Reproductive cells

- Fetus

Which cells are more resistant to radiation?

- Nerve and muscle cells

- Cells that don't actively divide

Example of somatic damage

Squamous cell carcinoma developing on the hand of an individual who received a high level of radiation exposure to the hand

Example of genetic damage

- Produces injury to the reproductive cells of the exposed individual

- Damage can result in birth defects in children born

Examples of immediate effects of radiation

Erythema of the skin following radiation therapy

Example of latent effects of radiation

Slowly developing cataracts in the eyes of a person with small but chronic exposure to radiation

Chronic exposure of individuals to low levels of radiation produces what effects?

1. Increase in the incidence of neoplasia

2. Specific increase in the incidence of squamous cell carcinoma

3. Increase in the frequency of occurrence of leukemia

4. Premature aging

What is the risk of an expectant mother being exposed to radiation?

Increased risk of leukemia and other cancers in the children

How much exposure can an embryo/fetus take during pregnancy?

Exposure cannot exceed 0.5 rem (500 millirems or 5 milli Sieverts mSv)

Once a woman declares her pregnancy, radiation exposure shouldn't exceed?

Should not exceed 0.05 rems (50 millirems) in any month

Where should monitoring device be worn?

- At the thyroid level on the collar outside the apron

- If fluoroscopy is done, an additional ring or wrist band must be worn

Most commonly used radiation monitoring devices?

Film and TLD (thermoluminescent dosimeters) badges

Goal of radiation safety?

To prevent injury from exposure to ionizing radiation

Annual/Yearly occupational dose equivalent limits

Whole body (total effective dose equivalent): 5 rems

Skin & extremities (shallow dose equivalents): 50 rems

Lens of the eye (eye dose equivalent): 15 rems

X-ray tube housing must be?

Diagnostic type

X-rays that extend beyond the area of clinical interest?

- Serve no useful function

- Increase scatter

- Must be eliminated by careful collimation

Why should there be an unexposed border on two opposing sides of the film?

To prove that the x-ray beam didn't exceed the size of the film cassette

Decreasing the amount of tissue exposed =?

- Amount of scatter radiation is reduced

- Also reducing the scatter radiation exposure to personnel

Reduction of the size of the x-ray beam =?

Improves the diagnostic quality of the film by lessening the amount of fog caused by scatter radiation

Diagnostic x-ray tubes use what as the filter material?

Aluminum or its equivalent

Amount of inherent filtration produced by most diagnostic x-ray tubes?

Ranges from 0.5-0.8 mm aluminum equivalent

Function of a filter

Absorbs the lower energy (long wavelengths) x-rays before they reach the patient

- To allow the higher energy (short wavelengths) x-rays to pass through

Exposure cord on the hand or foot switch should be how long?

No less than 6 feet in length

Exposure settings for evaluating aprons and gloves?

- 85 kVp

- 10 mAs

- 40 inch FFD

Gloves and aprons are designed to?

Protect the wearer from scatter radiation

Why should you use cassette holders when taking radiographs of large animals?

To reduce the assistant's exposure to radiation

A film/screen mismatch will result in?

- Image degradation and increased radiation exposure

- Example: blue-light-emitting screens shouldn't be used with green sensitive film and vice versa

Principal factors relating to the production of quality radiographs are:

1. Patient positioning

2. The body part of clinical interest should be centered on the film

3. Body part should be perpendicular to the central main x-ray beam and parallel to the film

4. Align the x-ray tube with the film (cassette)

5. Ensure correct focal film distance is correct (usually 40 inches)

6. Proper techniques selection

7. Precisely measure the body part for use with a technique chart

How should exposure protocols be adjusted when existing systems are updated to digital or computed radiography?

Adjusted to reflect 30-50% reduction in mAs or exposure time

Windowing

- Can alter the contrast and gray scale

- a point processing operation that changes the contrast and brightness of the image on the monitor

Developer and fixer tanks should be covered to?

To prevent oxidation

What happens to a film that has been overexposed and underdeveloped?

Film tends to lose most of its diagnostic quality = significant increase in exposure to the animal patient and radiographer

Optimum temperature and time for manual film developing

- 68-70 degrees F

- 5 minutes

Temperatures of developing solutions should never exceed and fall below?

- Exceed 75 F

- Fall below 65 F

How long do you keep films in fixer solution?

10 minutes

How long do you wash films in running water?

30 minutes

Main purpose in the control of radiation exposure

- To ensure that no exposure is unjustified in relation to its benefits

- Any necessary exposures are kept as low as is reasonably achievable (ALARA)

- Doses received to personnel are kept well below the allowable limits

Occupational exposure is recorded?

At least quarterly and preferably monthly

How many feet away should the operator or any individual stand from the animal patient?

At least 6 feet away

What does collimating device do?

Restricting the useful beam to the area of clinical interest

Total filtration required for equipment operating up to 70 kVp?

1.5 mm of aluminum-equivalent

Total filtration required for equipment operating over 70 kVp?

2.0 mm of aluminum-equivalent

What helps provide inherent filtration?

The window's glass covering on the x-ray tube

Exposure switch should be?

Dead-man type

A report of change needs to be reported in how many days?

Within 30 days of change in registrant's name, address, location of installation, receipt, sale, transfer, disposal, or discontinuance of use of x-ray machine

How should aprons be stored?

Hung without creases to prevent cracking

How should gloves be stored?

Should be stored so that liners can dry

How much does a 0.25 mm lead-equivalent apron reduce the exposure of a primary x-ray beam of 100 kVp?

60%

How much does a 0.50 mm lead-equivalent apron reduce the exposure of a primary x-ray beam of 100 kVp?

Attenuates the beam by 85%

Veterinary radiographers are responsible for adhering to all the following radiation safety procedures:

1. Increase or maximize the distance between the operator and source of radiation

2. Use chemical and mechanical restraint whenever possible to eliminate the need for holding a patient during radiographic exposure

3. Use general anesthesia when total immobility and complete relaxation of the animal patient is required for accurate positioning

4. Use appropriate protective devices, such as gloves, aprons, and protective goggles, as well as fixed or mobile barriers such as walls or movable leaded Plexiglas shields

5. Reduce the duration and amount of exposure

6. Plan radiographic procedures carefully and avoid unnecessary retakes

How much would an operator's exposure be reduced when increasing their distance from radiation exposure by a factor of two?

Their exposure would be reduced to 1/4th of the original amount (4 being the square of 2)

How much would an operator's exposure be reduced when tripling their distance factor from radiation exposure?

Exposure would be reduced to 1/9th of the original amount (9 being the square of 30

What happens when the distance between the operator and the source of radiation increases?

The intensity of primary x-ray beam, scatter radiation, and leakage from x-ray tube diminishes rapidly

Mechanical restraining devices help to?

1. Reduce radiation exposure

2. Help to improve radiographic quality by preventing patient motion

Mechanical restraining devices examples?

1. Vinyl or foam covered sandbags

2. Foam wedges

3. Plastic or foam troughs

4. Plastic head braces and mouth specula

5. Rope

6. Gauze

7. Tape

8. Velcro straps

Lead glass goggles offer?

Protection to the lens of the eye

How much do rare earth screens reduce patient dose and exposure to personnel?

- Between 2-5x, without any loss of image quality

- Compared to the older Acalcium tungstate screens

Low-absorption cassette fronts offer?

Minimum filtration of the x-rays passing through the cassette & can aid in keeping patient dose at a minimum

mAs determines?

- Determines the amount of x-radiation

- Quantity

kVp determines?

- Determines penetrating ability

- Quality

Using high kVp techniques that are appropriate, permits the veterinary radiographer to?

Lower the mAs settings and decrease radiation levels

Do digital radiography systems have the same x-ray energy responses as film screen ssytems?

- No, they may have different x-ray energy responses

- So the technical exposure factors should be different for that used for film screen ssytems

One of the biggest causes of excessive and unnecessary radiation exposure to veterinary radiographers?

- Retakes

- Every examination that has to be repeated = results in doubling the radiation received by the patient and by personnel

Counter tops and feed trays should be cleaned how often?

Daily

How often should screen cleaner by used?

On a regular basis, not less than monthly

- As recommended by the screen manufacturer

Darkroom safe lights should be?

Equipped with an appropriate filter and bulb combination

An x-ray film should never be _______ in order to shorten developing time?

Overexposed

64-66 degrees F = how many minutes for developing?

7 minutes

72-76 degrees F = how many minutes for developing?

4 minutes

Who do you report to when there's any overexposure of x-ray personnel?

RHB (Radiologic Health Branch)

If manual restraint is to be sued, the individual holds the animal patient how far away?

- At arms length with the body positioned as far away from the animal patient as possible

- Head and body may not be bent over the animal patient

Where can label stating the lead equivalent be found?

- Hem of the apron

- Cuff of the glove

What are gloves and aprons made of?

- Lead impregnated leather

- Vinyl

What does digital cassette have that film does not?

Reusable phosphor plate

Reusable phosphor plates

- Sensitive to x-rays, not light

- More expensive, but can be reused several thousand times

- More X-ray sensitive than film = allows a slightly lower radiation dose to be used

Advantages of digital over film

- Elimination of expensive film

- Absence of toxic developing chemicals

- Speed - within 30 seconds image is visible

Screens should be cleaned to?

Remove artifacts

Films should be handled carefully to prevent?

Artifacts due to static electricity or fingerprints

Which months are the embryo/fetus most sensitive to radiation?

First 3 months of pregnancy

Should women be concerned about sterility or loss of ability to bar children from occupational exposure?

No

Occupational dose equivalent limits for people under 18 years of age

May receive 10% of the adult occupational dose limits

Most x-ray tubes are surrounded by?

By oil for electrical insulation and keeping the tube cool