1. Radiation Safety Lavin: Chapter 16 CTVT: 566-570 Angus’ Paw
Test Monday morning – Must pass with an 80% to be able to participate in labs
Angus’ Paw

2. Learning Objectives: Chapter 16
Understand radiation risks
Define maximum permissible dose (MPD)
Understand the types of personal exposure dosimeters
List practical methods personnel can use to reduce exposure
Describe and understand the importance of personal protective equipment (PPE)

3. ALARA: As Low As Reasonably Achievable
NOT a set number but a general guideline
The workplace program developed to ensure that radiation dosages are kept as low as possible **
Governs everything we do
Setting exposure factors
Protecting ourselves and patients
National Council on Radiation Protection & Measurements – Governmental body that sets standards for radiation safety **
“All ionizing radiation is harmful, and data is not available to indicate if there is a threshold below which no harmful effects will occur.”
IRL:
It’s easy to become lax
Peer pressure
Norms and habits in a clinic may not be optimal
Not trying to scare you
Want you to understand
Respect the danger & importance of protection
Same as chemo drugs, fractious cats, MRSA, etc
** From VTNE Prep Question

4. What are the dangers? Amounts potentially damaging but random
Human body = 80% water
Liquid is a conductor of electricity
Radiation targets DNA
Especially rapidly growing/dividing cells
Most vulnerable
Young people
Unborn babies
Some tissues/organs are more susceptible – Rapidly dividing cells of the intestinal lining, neoplastic cells, reproductive cells **
Radiation is nonselective – affects where it hits
Radiation damage is random:
Delivered intermittently
Over long time
Young patients live longer
** From VTNE Prep Question

5. Radiation targets DNA…
3 things can occur:
No immediate effect - damage can show up later
Cell is damaged – repairable or not
Cell death
Main concern is “latent” effects
No recorded cases of death from diagnostic x-ray exposure
Biggest risk to personnel: Stochastic (random probability)
Malignancy
Genetic effects
DNA
Genetic code for development and functioning of all known living organisms and many viruses.
One of 3 major macromolecules essential for all known forms of life
With proteins & RNA
Double helix held together by hydrogen bonds
Latent effects = ones you can’t see

6. Primary vs Secondary Radiation
2 causes of radiation danger:
Primary – Direct exposure without protection
Secondary –
Scattered radiation:
Photons still have energy after penetrating patient
Produce radiation from atoms in the patient
“Scattered” photons emitted from patient
Most important impact on healthcare workers
What can increase the amount of scattered radiation?
Why is scattered radiation more of a danger than primary?
Photons –
Elementary particle of electromagnetic radiation
Force carrier for the electromagnetic force
What can increase the amount of scattered radiation?
Failure to narrow the beam via collimation
Using too high a kVp – nowhere for photons to go
Failing to use a grid for animals over 10 cm
Why is scattered radiation more of a danger?
Uncontrolled
Invisible rays
Caused by unseen mechanism

8. Tissue Damage from Radiation
Two types of tissue damage:
Somatic – Occurring within the life of the individual
Genetic – Occurring in future generations
Organ systems most sensitive:
Reproductive organs
Hematopoietic cells
Lymphocytes
Thyroid gland
Intestinal epithelium
Lens of the eye
Developing fetus
Tissue damage:
Somatic – Non-reproductive cells
Radiation sickness
Effects:
Loss of hair Ulceration
Fibrosis of the lungs Holes in tissue
Lymphocytopenia – lower WBC’s
Cataracts in the eyes
Genetic – Future generations/reproduction
Birth defects
Organ systems most sensitive:
Reproductive organs – infertility, decreased hormone production, mutations
Hematopoietic cells/Lymphocytes
Lowered resistance to infection
Clotting disorders
Thyroid gland – X-rays are causative agent, gland unprotected
Intestinal epithelium
Lens of the eye
Developing fetus –
1st 9 days most dangerous for death
10 days-6 wks for organs

9. Radioactivity Radioactive disintegration or decay –
The way an unstable atom achieves stability
The nucleus spontaneously emits particles & energy and transforms into a form more stable
Radionuclides – Atoms that are going through radioactive decay
Isotopes – Variants of an atom that have differing numbers of neutrons
Radioisotopes are radioactive

10. Radiation Intensity All radiation has the ability to penetrate tissue
Linear energy transfer – The rate at which energy is transferred from ionizing radiation into soft tissue
Higher LET: (Includes scattered radiation)
Greater energy transferred per interaction
Less ability to penetrate since energy decreases rapidly
Increased potential damage because of amount of energy absorbed
Lower LET: (Includes X-rays)
Can travel easily through matter but deliver less radiation per intereraction
Greater penetrability to tissue
Fewer immediate effects on tissue

11. Legal Prohibitions: Exposure
Prohibited from participating in radiographic procedures:
Individuals under age 18 **
“Declared” pregnant women
Our Radiation Safety Officer: Ms. Huff
If any concerns or questions about x-ray exposure: Please let me or Ms. Huff know…
Texas Department of State Health Services
Radiation Safety Officer:
Staff training
Protection of employees, patient, and public
Test equipment at least every 2 years
Act as an advisor
Monitoring dosage for personnel & patients
X-ray signage
Remember: If you are pregnant, or may be pregnant, see me ASAP!
** From VTNE Prep Question

12. Maximum Permissible Dose (MPD)
Defined as:
The dose the NRC has determined should not harm the person receiving it over their lifetime
The maximum permissible dose for whole-body radiation per year that is allowed by law
MPD = .05 sv/year ** or 5 rem/year **
Sievert (sv) =
Unit of equivalent dosage (replaced rem)
Dose equivalent = Quantity of radiation per unit of mass, taking into consideration the biologic effect on specific tissue types **
Dose of radiation equivalent to the absorbed dose in tissue **
1 sv = 100 rem (Roentgen equivalent man) **
MPD –
A quality factor to determine a dose
A framework for a conversation
Wilhelm Röntgen:
German physicist who discovered x-rays and developed x-ray photography
Won Nobel Prize.
Higher for non-radiation workers because radiation workers wear PPE
** From VTNE Prep Question

13. MPD (cont.) Other radiation dosage units: **
Gray (gy) – Unit of absorbed dose
Amount of radiation needed to deposit 1 joule of energy into 1 kg of matter
Roentgen equivalent man (rem) – Traditional unit of equivalent dosage
Replaced by Sv
Radiation absorbed dose (rad) – outdated measurement **
How much is too much?
No one really knows
Dose limits for non-radiation workers > radiation workers
Radiation worker: An individual who could be exposed to radiation from man-made sources during their work
** From VTNE Prep Question

14. ALARA ≠ MPD ALARA: As Low As Reasonably Achievable
NOT a set number but a general guideline
No set safe amount is known
A universal principle
“Keep exposure as low as possible”
MPD: Maximum Permissible Dose
Amount of ionizing radiation a person may be exposed to supposedly without being harmed
Is a set number
Assumed to be safe, but no one knows for sure

15. Minimizing Exposure 3 cardinal rules of protection: **
Time – Minimize time spent near radiation sources
Distance – Maximum practical distance from radiation source
Shielding – Placing a shield between the subject and source
Digital radiography exposes twice the amount of film radiography
But fewer retakes
** From VTNE Prep Question

16. Pregnancy & Radiation
Severity of response to the fetus is directly related to both dose and time
Most critical time is 2nd to 10th week: period of organogenesis
NO SAFE LIMIT HAS BEEN ESTABLISHED.

17. Minimizing Exposure: Time
Reducing time is an important factor
Use the shortest exposure time possible
Use the fastest film-screen combination
Proper darkroom practices
Use a customized technique chart
Digital radiography reduces repeats
Collimate the beam down to the area of interest
Dosimeters must be worn by anyone working with or in the vicinity of an x-ray machine **
Measures radiation dose for one person in one location over time…
** From VTNE Prep Question

18. Personal Radiation Dosimeters
Also called: “film badges”
Three types:
Whole body dosimeters
Worn above the waist but below the head
Monitors exposure of the thyroid and lenses of the eye **
Outside other protective equipment
Extremity dosimeters
Fetal dosimeters
Worn in conjunction with other gear
Worn on the belly under other equipment
** From VTNE Prep Question

19. Dosimeters Thermoluscent dosimetry:
Registers a charge over time if exposed to radiation
Rules of usage:
Must not be taken home
Store away from radiation
Store away from heat, sunlight
Wear only at that site
Attach outside thyroid collar
Never wear on jacket or lab coat – Why?
Must never be shared
Do not leave in x-ray room **
Employed at more than one site: wear a different one at each
Facility will post results periodically
Most technicians average .04 rem per year
vs 5rem MPD
** From VTNE Prep Question

20. Dosimetry Report
Dosages reported in mrem (millirem’s) or 1/000 rem

21. Minimizing Exposure: Distance
Determines the intensity of radiation at a given distance?
Maximizing distance:
Maximize distance from the source **
Lean/turn away from the beam
Exit the room, if possible
Sandbags or non-manual restraint
Sedate where possible
Inverse square law:
The intensity of radiation is inversely proportional to the square of the distance of the object from the source
Why matters? Farther = less intense but more spread out
Maximizing distance:
Turn or lean away
Look away
Not a social occasion
Tape or wooden spoons to hold/move
** From VTNE Prep Question

22. Minimizing Exposure: Shielding
Positioning a barrier between you and the radiation source greatly reduces the level of radiation exposure.
What you can do:
Wear aprons, gloves, glasses, thyroid shield, etc.
Wearing gloves provides no protection from primary x-ray beam **
What material is used in most shielding and why?
Lead
High atomic mass so shields most rays
How might an apron or gloves not help you?
Not properly maintained
Cracks or creases
Primary beam!
Wearing PPE is not fun, but it is necessary
The room has shielding, as well
Must have appropriate signage
** From VTNE Prep Question

23. Personal Protective Equipment (PPE)
Made of thin sheets of lead layered together
The lead can crack and break without proper care
Minimum safe lead thickness is 0.79 mm (book)
VTNE Prep materials say 0.5mm **
Use & care of PPE:
Hang aprons up by the shoulders
No folding or creasing
If cracks are present, they appear black when radiographed **
Clean regularly - warm water/mild soap
Should fit correctly
Treat thyroid collars with the same respect
Rotate non-radiation workers
Other helpful ways to reduce risk:
Immobilization
Foam blocks
Cloth restraints
Tie-downs
Wooden spoons
** From VTNE Prep Question

24. Other Methods To Minimize Exposure
Restrain using gear/equipment
Lay gloves across quiet patient
Wooden spoons, etc.
Immobilize patient
Cloth restraints & tie-downs
Sedation
Collimate carefully
Avoid retakes!
Against the rules – Cannot x-ray personnel

25. Vet Nerd Stuff…

26. Atlas-Axial Luxation

27. GDV

28. Crossbow through the skull

29. Hydrocephalus
Hydrocephalus

30. Megacolon

31. HBC Aussie

32. Puppies