Module 5: Chapters 3 (Radiation Biology), 4 (Radiation Protection), & 12 (Dental Images and the Dental Radiographer)

1. The indirect theory proposes that
a) toxins are created from the formation of free radicals.
b) ionizing radiation strikes critical areas within cells.
c) direct injuries occur more frequently than indirect injuries.
d) changes occur to the deoxyribonucleic acid (DNA) of a cell.

a) toxins are created from the formation of free radicals.
b) ionizing radiation strikes critical areas within cells.
c) direct injuries occur more frequently than indirect injuries.
d) changes occur to the deoxyribonucleic acid (DNA) of a cell.

2. Which of the following is an example of stochastic effects?
a) Erythema
b) Cancer
c) Hair loss
d) Radiation sickness

a) Erythema
b) Cancer
c) Hair loss
d) Radiation sickness

3. Which of the following cells would be the most sensitive to x-rays?
a) Nerve
b) Bone
c) Muscle
d) Blood

a) Nerve
b) Bone
c) Muscle
d) Blood

4. According to the current recommendations of the National Council on Radiation Protection and Measurements, the current MPD for occupationally exposed persons is ___________/year.
a) 5.0 mSv
b) 50 mSv
c) 500 mSv
d) 5000 mSv

a) 5.0 mSv
b) 50 mSv
c) 500 mSv
d) 5000 mSv

The ALARA concept states that all radiation must be kept
a) as long as readily achievable.
b) as low as reasonably allowable.
c) as low as reasonably achievable.
d) as long as reliably achievable.

a) as long as readily achievable.
b) as low as reasonably allowable.
c) as low as reasonably achievable.
d) as long as reliably achievable.

6. You are 36 years old. What is your cumulative occupational dose recommended by the National Council on Radiation Protection and Measurements (NCRP)?
a) 360 millirems
b) 360 mSv
c) 180 millirems
d) 180 mSv

a) 360 millirems
b) 360 mSv
c) 180 millirems
d) 180 mSv

7. Which term describes the dose of radiation that the body can endure with little or no chance of injury?
a) radiation limit
b) maximum permissible dose
c) occupationally exposed dose
d) ALARA

a) radiation limit
b) maximum permissible dose
c) occupationally exposed dose
d) ALARA

8. Which device restricts the size and shape of the x-ray beam?
a) filter
b) collimator
c) barrier
d) film badge

a) filter
b) collimator
c) barrier
d) film badge

9. Which describes the function of filtration?
a) increases scatter radiation
b) increase divergent rays
c) increases long wavelengths
d) reduces low-energy waves

a) increases scatter radiation
b) increase divergent rays
c) increases long wavelengths
d) reduces low-energy waves

10. The latent period in radiation biology is the time between
a) initial injury and repair
b) subsequent doses and repair
c) cell rest and cell mitosis
d) exposure to x-radiation and clinical symptoms

a) initial injury and repair
b) subsequent doses and repair
c) cell rest and cell mitosis
d) exposure to x-radiation and clinical symptoms

11. The traditional unit for measuring x-ray exposure in the air is termed
a) rem
b) gray
c) roentgen
d) rad

a) rem
b) gray
c) roentgen
d) rad

12. Which of the following would a dental radiographer need in order to perform efficient, accurate dental imaging procedures on a patient?
a) Sufficient knowledge
b) Technical skills
c) Sufficient knowledge and technical skills
d) Neither sufficient knowledge nor technical skills

a) Sufficient knowledge
b) Technical skills
c) Sufficient knowledge and technical skills
d) Neither sufficient knowledge nor technical skills

13. Assigned responsibilities of dental auxiliaries in regard to dental imaging may include
a) diagnosing disease on dental images.
b) prescribing dental images.
c) education of patients about dental imaging.
d) creating a treatment plan based on the findings of dental images.

a) diagnosing disease on dental images.
b) prescribing dental images.
c) education of patients about dental imaging.
d) creating a treatment plan based on the findings of dental images.

14. When should you avoid taking retakes?
a) Whenever it is convenient because the dose is so low
b) Only if the patient is uncomfortable with exposure
c) Only if older (pre-1975) equipment is used
d) At all times

a) Whenever it is convenient because the dose is so low
b) Only if the patient is uncomfortable with exposure
c) Only if older (pre-1975) equipment is used
d) At all times

15. In order to avoid the primary beam while taking dental images, you should stand at a ____-degree to ____-degree angle to the beam.
a) 0; 45
b) 45; 90
c) 90; 135
d) 135; 180

a) 0; 45
b) 45; 90
c) 90; 135
d) 135; 180

16. Radiation monitoring can be used to protect the dental radiographer and includes monitoring of
a) equipment but not personnel.
b) personnel but not equipment.
c) both equipment and personnel.
d) drywall for residual radiation.

a) equipment but not personnel.
b) personnel but not equipment.
c) both equipment and personnel.
d) drywall for residual radiation.

17. __________ refers to the total amount of radiation that is received or absorbed.
a) Total dose
b) Dose rate
c) Amount of tissue irradiated
d) Cell sensitivity

a) Total dose
b) Dose rate
c) Amount of tissue irradiated
d) Cell sensitivity

18. Which of the following is the least sensitive to x-rays?
a) Bone marrow
b) Salivary glands
c) Lymphoid tissue
d) Intestines

a) Bone marrow
b) Salivary glands
c) Lymphoid tissue
d) Intestines

19. Your patient is concerned about being exposed to dental x-rays. Which of the following could you tell your patient to alleviate her fears?
a) We take x-rays once a year, it is safe, and that is all your insurance will pay for.
b) Your risk of getting cancer from dental x-rays is only 2 times greater than getting cancer spontaneously.
c) The risks from dental imaging are not significantly greater than the risks of other everyday activities in modern life.
d) Three fourths of the radiation exposure you will have throughout your life will come from background radiation.

a) We take x-rays once a year, it is safe, and that is all your insurance will pay for.
b) Your risk of getting cancer from dental x-rays is only 2 times greater than getting cancer spontaneously.
c) The risks from dental imaging are not significantly greater than the risks of other everyday activities in modern life.
d) Three fourths of the radiation exposure you will have throughout your life will come from background radiation.

20. All are radioresistant except
a) Lens of the eye
b) Kidney
c) Nerve Tissue
d) Muscle Tissue

a) Lens of the eye
b) Kidney
c) Nerve Tissue
d) Muscle Tissue

Kahoot
1. The unit for measuring the absorption of x-rays is termed
a) rad
b) roentgen
c) rem
d) sievert

a) rad
b) roentgen
c) rem
d) sievert

Kahoot
2. Direct radiation injury occurs when:
a) free radical cells combine to form toxins
b) x-ray photons pass through the cell
c) x-ray photons hit critical targets within a cell
d) free radicals combine to form toxins

a) free radical cells combine to form toxins
b) x-ray photons pass through the cell
c) x-ray photons hit critical targets within a cell
d) free radicals combine to form toxins

Kahoot
3. Indirect radiation injury occurs when:
a) x-ray photons hit critical targets within a cell
b) x-ray photons are absorbed and form toxins
c) x-ray photons pass through the cell
d) x-ray photons hit the DNA of a cell

a) x-ray photons hit critical targets within a cell
b) x-ray photons are absorbed and form toxins
c) x-ray photons pass through the cell
d) x-ray photons hit the DNA of a cell

Kahoot
4. The traditional unit for measuring x-ray exposure in the air is:
a) rem
b) roentgen
c) rad
d) gray

a) rem
b) roentgen
c) rad
d) gray

Kahoot
5. Radiation effects that are seen within minutes, days, or weeks are called:
a) somatic effects
b) genetic effects
c) long-term effect
d) short-term effects

a) somatic effects
b) genetic effects
c) long-term effect
d) short-term effects

Kahoot
6. Which tissue/organ is radioresistant?45sec
a) nerve tissue
b) reproductive cells
c) skin
d) bone marrow

a) nerve tissue
b) reproductive cells
c) skin
d) bone marrow

Kahoot
7. Adults are more susceptible to radiation damage than children.
a) True
b) False

a) True
b) False

Kahoot
8. The dose of radiation that the body can endure with little or no chance of injury is called:
a) ALARA
b) occupational exposed dose
c) maximum permissible dose
d) radiation limit

a) ALARA
b) occupational exposed dose
c) maximum permissible dose
d) radiation limit

Kahoot
9. Which tissue/organ is NOT radiosensitive?
a) lens of the eye
b) salivary gland
c) intestines
d) oral mucosa

a) lens of the eye
b) salivary gland
c) intestines
d) oral mucosa

Kahoot
10. Which is NOT an example of artificial radiation?
Which is NOT an example of artificial radiation?
a) medical radiation
b) radon
c) consumer products
d) nuclear medicine

a) medical radiation
b) radon
c) consumer products
d) nuclear medicine

Kahoot
11. An 8-inch PID is more effective than a 16-in PID in reducing radiation exposure of the patient.
a) True
b) False

a) True
b) False

Kahoot
12. The acronym ALARA stands for:
a) as low as reasonably acceptable
b) as little as reasonably acceptable
c) as little as reasonably allowed
d) as low as reasonably achievable

a) as low as reasonably acceptable
b) as little as reasonably acceptable
c) as little as reasonably allowed
d) as low as reasonably achievable

Kahoot
13. Which device restricts the size and shape of the x-ray beam?
a) collimator
b) filter
c) tubehead
d) receptor

a) collimator
b) filter
c) tubehead
d) receptor

Kahoot
14. Which best describes the function of a filter in a dental x-ray tubehead?
a) It reduces the size and shape of the beam.
b) It removes low energy x-rays
c) It decreases the mean energy of the beam.
d) It removes the dose of radiation to the thyroid gland.

a) It reduces the size and shape of the beam.
b) It removes low energy x-rays
c) It decreases the mean energy of the beam.
d) It removes the dose of radiation to the thyroid gland.

Kahoot
15. What is the maximum permissible dose for occupationally exposed person?
a) 1 mSV/year
b) 0.5 mSV/year
c) 50 mSV/year
d) 100 rem/year

a) 1 mSV/year
b) 0.5 mSV/year
c) 50 mSV/year
d) 100 rem/year

Kahoot
16. To avoid the primary x-ray beam, the dental radiographer should stand at which angle during exposure?
a) 20-45 degree angle
b) 70-90 degree angle
c) 45-70 degree angle
d) 90-135 degree angle

a) 20-45 degree angle
b) 70-90 degree angle
c) 45-70 degree angle
d) 90-135 degree angle

Kahoot
17. A rectangular collimator exposes 60% less tissue than a circular collimator.
a) True
b) False

a) True
b) False

Kahoot
18. Patient and operator protection must be primary concerns of the dental radiographer.
a) True
b) False

a) True
b) False

Kahoot
19. Which example does NOT promote operator efficiency?
a) properly positioning the PID
b) retaking a dental image
c) carefully placing the image receptor
d) using correct exposure settings

a) properly positioning the PID
b) retaking a dental image
c) carefully placing the image receptor
d) using correct exposure settings

Kahoot
20. The benefits of disease detection with images outweighs the risk associated with the small doses of radiation exposure.
a) True
b) False

a) True
b) False

2 Possible Mechanisms of Radiation Injury

Some x-rays are absorbed by the patient’s tissues, which produces chemical changes that cause biological damage.

1. Ionization: results when x-rays strike patient tissue; produced through photoelectric effect or Compton scatter; results in the formation of a positive atom and a dislodged negative electron

   • dislodged electron interacts with other atoms in the tissues and causes further biologic damage

2. Free Radical Formation: PRIMARY way damage occurs; an x-ray photon ionizes water to produce hydrogen and hydroxyl free radicals which either recombine without causing changes, combine with other free radicals and cause changes, or combine with ordinary molecules to produce toxins (like H2O2)

   • free radicals: uncharged atoms or molecules that exist with a single, unpaired electron in its outermost shell; are highly unstable and reactive

2 Theories of Radiation Injury

1. Direct Theory: ionizing radiation DIRECTLY HITS CRITICAL AREAS OF THE CELL (ex: DNA) and is absorbed; occurs infrequently

2. Indirect Theory: x-ray photons are ABSORBED BY WATER within a cell which FORMS A FREE RADICAL which forms toxins; causes cellular dysfunction and biological damage; occurs most frequently bc of high water content in cells

Dose-Response Curve

dose-response curve: a way to plot the dose of radiation administered and the damage produced; correlates the response (damage) with the dose

• linear relationship — response of tissues is directly proportional to the dose

• Nonthreshold relationship: a threshold dose level for damage does not exist; no matter how small the radiation received, some biologic damage occurs

Stochastic VS Non-stochastic Effects

Stochastic Effects: occurs as a direct function of the dose; NO identifiable dose-threshold; occurs because of the effects of ionizing radiation on chromosomes that cause genetic mutations

• PROBABILITY of damage increases with increased dose

• severity of effects does NOT depend on the magnitude of the absorbed dose

• ex: radiation-induced cancer, genetic mutations, tumors

Non-stochastic effects (deterministic effects): has an identifiable dose-threshold; caused by significant cell damage

• effects increase in SEVERITY with an increased absorbed dose

• ex: erythema, hair loss, cataracts, decreased fertility

Sequence of Radiation Injury

Sequence of Radiation Injury

1. Latent Period: time that elapses between exposure to ionizing radiation and the appearance of observable clinical signs; depends on the TOTAL DOSE and DOSE RATE

2. Period of Injury

3. Recovery Period: cells can repair the damage caused (depending on several factors)

4. Cumulative Effects: the effects of radiation exposure are additive; unrepaired damage accumulates in tissues

Effects of Radiation

• determining factors

• types of effects

• radioresistant/radiosensitive cells, tissues, & organs

Determining Factors for radiation injury:

• total dose (higher dose = more damage)

• dose rate (higher rate = more damage bc a rapid delivery of radiation leaves less time for cells to repair)

• amount of tissue irradiated (larger areas with blood-forming tissues exposed = more extensive damage)

• cell sensitivity (ex: rapidly dividing cells, young cells)

• age (children are more susceptible to damage than adults)

Types of Effects:

• Short-Term Effects: associated with LARGE TOTAL DOSE and HIGH DOSE RATE; causes ARS (Acute Radiation Syndrome; nausea, vomiting, diarrhea, hair loss, hemorrhage)

• Long-Term Effects: associated with SMALL DOSES absorbed REPEATEDLY over a LONG PERIOD OF TIME; effects seen after years, decades, or in later generations; ex: cancer, birth anomalies, genetic defects

• Somatic Effects: occurs in SOMATIC cells; seen in the person irradiated but not in future generations; damage can be repaired

• Genetic Effects: occurs in GENETIC cells; seen in FUTURE GENERATIONS but not the person irradiated; damage can NOT be repaired

Radiosensitive: sensitive cells are highly mitotic, highly metabolic, and are immature (undifferentiated); sensitive tissues, organs, and cells include blood cells, immature reproductive cells, young bone cells, small lymphocyte, lymphoid tissue, bone marrow, testes, intestines, oral mucosa, reproductive cells

• critical organ: an organ that, if damaged, diminishes the quality of a person’s life (ex: thyroid gland, bone marrow, skin, lens of eye)

Radioresistant: tissues/organs composed of radioresistant cells include salivary glands, kidneys, liver, nerve tissue, muscle tissue

Units of Radiation Measurement

2 Systems to Define Radiation Measurements:

1. Traditional: Roentgen (R), radiation absorbed dose (rad), Roentgen equivalent man (rem)

2. SI: Coulombs/kilogram (C/kg), Gray (Gy), Sievert (Sv)

Types of Measurements:

• exposure measurement

  • traditional: Roentgen (R); measures radiation by determining the amount of ionization that occurs in air (does NOT describe the amount absorbed)

  • SI equivalent: none exists; measured in Coulombs/kilogram (C/kg)

• dose measurement: amount of energy absorbed by tissue

  • traditional: rad (radiation absorbed dose)

  • SI equivalent: the gray (1 Gy = 100 rad)

• dose equivalent measurement: used to compare biologic effects of DIFFERENT KINDS of radiation; uses a quality factor (QF) to place exposure effects of different kinds of radiation on a common scale

  • traditional: rem (roentgen equivalent man)

  • SI equivalent: the Sievert (1 Sv = 100 rem); takes into account the absorbed dose AND the radiosensitivity of certain tissues

NOTE:

• Gy = Sv

• R=rad=rem

• dental imaging uses such small doses of radiation that measurements are expressed in milli/micro

Radiation Risks

Sources of Radiation Exposure:

• Natural background radiation: form of ionizing radiation found in the environment (includes cosmic radiation from the stars and sun and terrestrial radiation from radioactive materials in the earth and air)

• Artificial (humanmade) radiation: form of radiation resulting from modern technology (consumer products, fallout from atomic weapons, nuclear fuel cycle, medical radiation)

Risk Estimates: the potential risk of dental imaging inducing a fatal cancer in an individual has been estimated to be 3 in 1 million; the risk of a person developing cancer spontaneously is much higher at 3300 in 1 million

Dental images should be prescribed for a patient only when the benefit of disease detection outweighs the risk of biologic damage.

Patient Protection

• proper prescription: professional judgment is used to determine the number, type, and frequency of dental images

• proper equipment: use equipment that complies with state and federal radiation guidelines to minimize radiation exposure

  • filtration of low-energy beams (inherent + added filtration of aluminum disks = total filtration)

  • collimation

  • long, rectangular, 16-in PID (long PID = less divergence of x-rays)

• film speed: use the fastest speed film possible (digital sensors reduce exposure time by 50-90% compared with the use of film)

• collimation: a rectangular collimator reduces the absorbed dose by 60-70% compared with round collimators

• technique: ensures diagnostic images; retakes must be avoided at all times

• increasing the target-receptor distance reduces skin dose

• thyroid collar (protects thyroid), lead apron (protects reproductive organs and blood-forming tissues)

• use of beam alignment device

• selection of proper exposure factors

• proper receptor handling and proper film processing/image retrieval

Operator Protection

Avoid the Primary Beam

• distance: 6ft from tubehead

• position: 90-135 degrees from primary beam

• shielding: dental office design includes walls or protective barriers to protect the operator from primary and scatter radiation

Radiation Monitoring

• Equipment monitoring: x-ray machines must be monitored for leakage radiation

• Personnel monitoring: a radiation monitoring badge can be used

Radiation Exposure Guidelines

Radiation Safety Legislation: Radiation Control for Health and Safety Act (1986) and Consumer-Patient Radiation Health and Safety Act (1981)

Maximum Permissible Dose (MPD):

• occupationally exposed persons: 50 mSv/year

• nonoccupationally exposed persons: 1 mSv/year

• occupationally exposed pregnant women: 0.5 mSv/month

Cumulative Occupational Dose: should not exceed the worker’s age multiplied by 10 mSv

ALARA Concept: “as low as reasonably achievable”; every possible method of reducing exposure to radiation should be employed