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Dental Radiography > DENT 1050 Test #1, Chapters 4 and 5 > Flashcards

DENT 1050 Test #1, Chapters 4 and 5 Flashcards

1
Q

Radiation injury; All radiation is:

A

harmful and produces biologic changes in living tissue

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2
Q

Radiation injury; Free radical formation:

A

i. Primary form of damage x-radiation causes
ii. Occurs when an x-ray ionizes water
1. Results in hydrogen and hydroxyl free radicals

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3
Q

Free radical

A

an uncharged (neutral) atom or molecule that exists w/a single, unpaired electron in its outermost shell; highly reactive and unstable

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4
Q

To achieve stability, free radicals do 1 or 3 things:

A

a. Recombine w/o causing changes in the molecule
b. Combine w/ other free radicals and cause changes
c. Combine w/ ordinary molecules to form a toxin - damaging

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5
Q

Direct Theory of radiation injury

A

Cell damage results when ionizing radiation directly hits critical areas within the cell (DNA) - occurs infrequently

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6
Q

Indirect Theory of radiation injury

A

X-ray photons are absorbed w/in the cell and cause the formation of toxins which in turn damage the cell via free radicals;

i. greater chance of free radical formation because cells are 70-80% water
ii. actual damage done is BY the free radicals, ions and toxins, NOT the actual x-ray

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7
Q

Dose-Response Curve

A

used to correlate the “response” or damage of tissues w/the dose or amount of radiation received

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8
Q

Linear relationship of dose-response curve

A

response of the tissues - damage - is directly proportional to the dose

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9
Q

Nonthreshold relationship of dose-response curve

A

a threshold dose level for damage doesn’t exist; do not need a certain dose for damage to occur; NO absolute SAFE amount of radiation exposure

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10
Q

Radiation Injury Sequence, Repair & Accumulation

A

Latent period, period of injury, recovery period, cumulative effects

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11
Q

Latent Period of radiation injury

A

the time that elapses between exposure to ionizing radiation and the appearance of observable clinical signs; the more radiation received and the faster the dose rate -> the shorter the latent period

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12
Q

Period of injury of radiation injury

A

follows the latent period when cells show damage

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13
Q

Recovery period of radiation injury

A

depending on a number of factors, cells can repair the damage caused by radiation (if allowed time to repair)

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14
Q

Cumulative effects of radiation injury

A

the effects of radiation exposure are additive and damage that remains unrepaired accumulates in the tissue

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15
Q

Determining factors for radiation injury

A

Total dose, dose rate, amount of tissue irradiated, cell sensitivity, age

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16
Q

Determining factors: Total dose

A

quantity of radiation received

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17
Q

Determining factors: Dose rate

A

dose/time; more damage takes place with high dose rates b/c a rapid delivery of radiation doesn’t allow time for the cellular damage to be repaired

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18
Q

Determining factors: Amount of tissue irradiated

A

extensive radiation injury occurs when large areas of the body are exposed because of the damage that occurs to the blood-forming tissues (nuclear energy disaster)

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19
Q

Determining factors: Cell sensitivity

A

rapidly dividing, young cells are more adversely affected

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20
Q

Determining factors: Age

A

children are more susceptible to radiation damage than adults

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21
Q

Radiation effects: Short-term

A

a. seen within minutes, days or weeks
b. large amounts of radiation absorbed in a short amount of time
c. Acute Radiation Syndrome (ARS)
d. rarely seen in dentistry

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22
Q

Acute Radiation Syndrome (ARS)

A

includes nausea, vomiting, diarrhea, hair loss, hemorrhage

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23
Q

Radiation effects: Long-term

A

a. appear after years, decades or generations
b. Associated w/small amounts of radiation absorbed repeatedly over a long period of time
c. linked to induction of cancer, birth abnormalities and genetic defects

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24
Q

Radiation effects: Somatic effects, somatic cells

A
  • ALL THE CELLS IN THE BODY EXCEPT REPRODUCTIVE CELLS
    i. somatic effects; seen in the person irradiated
    ii. cell changes are NOT transmitted to future generations
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25
Q

Radiation effects: Genetic effects, genetic cells

A
  • REPRODUCTIVE CELLS: OVA & SPERM
    i. genetic effects: NOT seen in the person irradiated, but are passed on to future generations
    ii. genetic damage can NOT be repaired
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26
Q

Radiation effects on cells: Cancer cells

A

rapidly divide and are less differentiated - that’s why radiation therapy can be successful in the treatment of cancer

27
Q

Radiation effects on tissues and organs: Critical organs

A

organ that if damaged diminishes the quality of a person’s life
i. critical organs exposed during dental radiographs: skin, thyroid, lens of the eye, bone marrow

28
Q

Radiation measurements: Units of measurement

A

units are used to define: exposure, dose, dose equivalent; two systems: Traditional and Systeme Internationale

29
Q

Radiation measurements: Traditional system

A

a. Roentgen (R)
b. Radiation absorbed dose (rad)
c. Roentgen equivalent (in) man (rem)

30
Q

Radiation measurements: Systeme Internationale

*QF, quality factor; J, joule

A

a. Coulombs per kilogram (C/kg)
b. Gray (Gy)
c. Sievert (Sv)

31
Q

Coulomb (C)

A

unit of electrical charge; the quantity of electrical charge transferred by 1 ampere in 1 second

32
Q

Ampere (A)

A

unit of electrical current strength; current yielded by 1 volt against 1 ohm of resistance

33
Q

Erg (erg)

A

unit of energy equivalent to 1.0 x 10^-7 joules or to 2.4 x 10^-8 calories

34
Q

Joule (J)

A

SI unit of energy equivalent to the work done by the force of 1 newton acting over the distance of 1 meter

35
Q

SI

A

International System of Units

36
Q

Newton (N)

A

SI unit of force; the force that, when acting continuously on a mass of 1 kilogram, will impart to it an acceleration of 1 meter per second squared (m/sec^2)

37
Q

Kilogram (kg)

A

Unit of mass equivalent to 1000 grams or 2.205 pounds

38
Q

both Roentgen and Coulombs are measured in:

A

1 cc of air and 1 kg of air

39
Q

Roentgen (R)

A

Definition: 1 R = 87 erg/g
Conversion: 1 R = 2.58 x 10^-10 C/kg

40
Q

Radiation absorbed dose (rad)

A

Definition: 1 rad = 100 erg/g
Conversion: 1 rad = 0.01 Gy

41
Q

Roentgen equivalent (in) man (rem)

A

Definition: 1 rem = rads x QF
Conversion: 1 rem = 0.01 Sv

*QF, quality factor

42
Q

Coulombs per kilogram (C/kg)

A

Definition: —
Conversion: 1 C/kg = 3880 R

43
Q

Gray (Gy)

  • starred conversion
A

Definition: 1 Gy = 0.01 J/kg
Conversion: 1 Gy = 100 rads

44
Q

Sievert (Sv)

  • starred conversion
A

Definition: 1 Sv = Gy x QF
Conversion: 1 Sv = 100 rems

*QF, quality factor

45
Q

Radiation risks: In the U.S. the average dose of background radiation (BR) per year is:

A

150-300 mrads

46
Q

Radiation risks: risk and risk estimates

A
  1. Risk: likelihood of adverse effects or death resulting from exposure to a hazard
  2. Risk of dental radiography inducing a fatal cancer: approx. 3/1,000,000
  3. Risk of spontaneous cancer: 3,300/1,000,000
  4. Death is more likely to occur from common activities than from dental radiography
47
Q

Radiation risks: dental radiation and exposure risks; Thyroid gland

A

estimated dose of 6,000 mrads is necessary to produce cancer - dental radio dose is usually 6 mrads

48
Q

Radiation risks: dental radiation and exposure risks; Bone marrow

A

mand./max make up 1% of the body’s total bone marrow; Leukemia (directly associated with the amount of blood-producing tissues irradiated and the dose) is induced most likely at doses of 5,0000 mrads - avg bone marrow dose: 1-3 mrads from periapical

49
Q

Radiation risks: dental radiation and exposure risks; Skin

A

250 rads in 14-day period causes erythema - would have to have more than 500 dental films in 14-day period

50
Q

Radiation risks: dental radiation and exposure risks; Eyes

A

more than 200,000 mrads are necessary to induce cataracts - avg surface dose to cornea of the eye is approx. 60 mrads

51
Q

Collimation

A

Definition: restriction of the size and shape of the x-ray beam in order to reduce patient exposure;
Reduces 60-70%

52
Q

Risk vs Benefit of dental radiographs

A

the benefit of disease detection far outweighs the risk of damage from x-radiation

53
Q

Patient protection: Pregnancy

A

i. the recommendations don’t have to be altered
ii. FMS (18 films) w/ lead apron receives 1 mrem to uterus
iii. Background radiation in 9 mo. receives 225 mrem to uterus
iv. avoid it unless absolutely necessary (weigh risk to benefit

54
Q

Proper equipment: Filtration

A

added filtration: aluminum disks placed in the path of the x-ray between the collimator & the tubehead seal; used to filter out the longer wavelength, low-energy x-rays; added in 0.5 mm increments

55
Q

Proper equipment: Position-Indicating Device (PID); which is more effective but what is its disadvantage

A

rectangular is more effective than the round at reducing patient exposure; disadvantage is that it’s easier to “cone”-cut

56
Q

Thyroid collar

A

NOT recommended for use w/ extraoral films (panoramic) (results in non-diagnostic films - obscures information

57
Q

Fast Film

A

Single most effective method in reducing a pt’s exposure to x-radiation

58
Q

E-speed (Ektaspeed)

A

fastest intraoral film available; compared to D-speed film, it requires 1/2 exposure time

59
Q

Operator protection

A

THE DENTAL RADIOGRAPHER MUST AVOID THE PRIMARY BEAM. Dental radiographer should stand at a position perpendicular to the primary beam (90-135 degrees)

60
Q

Radiation exposure guidelines

A

Radiation Control for Health and Safety Act: enacted 1968

Consumer-Patient Radiation Health and Safety Act: enacted 1981

61
Q

Maximum Accumulated Dose (MAD)

A

occupationally exposed workers must not exceed an accumulated lifetime radiation dose - dose can and should be “0”

62
Q

Maximum Accumulated Dose (MAD)

A

determined by worker’s age (minimum age requirement is 18 years)

63
Q

ALARA concept

A

all exposure to radiation must be kept to a minimum or “AS LOW AS REASONABLY ACHIEVABLE”

Dental Radiography (14 decks)

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