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Term 2 : Dental Radiography > CHAPTER 4 : RADIATION BIOLOGY > Flashcards

CHAPTER 4 : RADIATION BIOLOGY Flashcards

1
Q

Radiation Biology

A

study of the effects of ionizing radiation on living tissues

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2
Q

Free radical formation occurs when an x-ray photon ionizes ________the primary component of living cells.

A

water

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3
Q

how does free radical formation occur

A

when a xray photon ionizes water

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4
Q

What is a free radical

A

An uncharged (neutral atom) or molecule that exists with a single unpaired electron in its outermost shell

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5
Q

what is the lifetime of a free radical ?

A

10 seconds

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6
Q

To achieve stability, free radicals :

A

recombine without causing changes in the molecule

combine with other free radicals and cause changes.

Combine with ordinary molecules to form a toxin

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7
Q

Two theories of how radiation damage biologic tissues

A
  1. Direct theory

2. Indirect Theory

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8
Q

Direct Theory

A

when ionizing radiation DIRECTLY hits critical areas and targets

(occurs infrequently)

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9
Q

Indirect theory

A

Xray photons are absorbed within the cell & cause formation of toxins (damages cell)

(occurs frequently b/c of high water content of cells)

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10
Q

Dose curve response

A

Used to correlate the damage of tissues with the dose of radiation received

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11
Q

Non-threshold dose response

A

No matter how small the amount of radiation , some biologic damage occurs.

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12
Q

Stochastic effects

A

Occurs as a direct function of dose

does not have a threshold radiation effects.

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13
Q

The main stochastic effects

A

Cancer and genetic mutations

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14
Q

Non schotastic effects (deterministic effects)

A

Have a threshold and increase in severity with increased absorbed dose,

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15
Q

What is non schotastic effects caused by

A

cell damage or cell death

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16
Q

examples of non schotastic effects

A

skin erythema, loss of hair, cataract formation.

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17
Q

Which effect requires a larger radiation dose to cause serious impairment in health ? Stochastic or non Stochatic?

A

Non stochastic

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18
Q

The three sequence of radiation injury

A
  1. Latent
  2. Period of Injury
  3. Recovery period
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19
Q

Latent period

A

the time that elapses between exposure to ionizing radiation and the appearance of observable clinical signs (symptoms)

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20
Q

Period of injury

A

include a variety of cellular injuries.

occurs after latent period

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21
Q

Recovery period

A

when damage caused by low-level radiation is repaired within the cells of the body

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22
Q

Cumulative effects of repeated radiation exposure can lead to _______

A

Health problems

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23
Q

Effects of radiation on bone marrow

A

leukemia

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24
Q

effects of radiation on reproductive cells

A

Genetic mutation

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25
Q

effects of radiation on salivary gland

A

carcinoma

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26
Q

effects of radiation on thyroid

A

carcinoma

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27
Q

effects of radiation on skin

A

Carcinoma

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28
Q

effects of radiation on eyes

A

cataracts

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29
Q

Total dose

A

Quantity of radiation received / total amount of radiation energy absorbed

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30
Q

Dose rate

A

Rate at which exposure to radiation occurs and absorption takes place.

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31
Q

Amount of tissue irradicated

A

Areas of the body exposed to radiation

32
Q

Cell sensitivity

A

More damage occurs in cells that are most sensitive to radiation

33
Q

Age

A

Children are more susceptible to damage than adults.

34
Q

Short term effects

A

Large amounts of radiation absrobed in a short time

35
Q

Long term effects

A

small amounts of radiation absorbed repeatedly in a long period of time

36
Q

Somatic cells

A

all the cells in the body except for reproductive cells

37
Q

genetic cells

A

The reproductive cells ( sperm ,ova)

38
Q

Somatic effects

A

seen in a person who has been irradicated. Major somatic effects includes induction to cancer such as leukemia.

39
Q

Genetic mutation

A

Does not effect the exposed individual but effects future generations

40
Q

Somatic mutations

A

Affects exposed individual but does not effect future generations.

41
Q

Radiosensitive

A

Cells that are sensitive to radiation

42
Q

radioresistant

A

cell that is resistant to radiation

43
Q

Mitotic activity

A

Cells that divide frequently are more sensitice to radiation

44
Q

Cell differentation

A

cells that are immature or not highly specialized are more sensitive to radiation

45
Q

Cell metabolism

A

cells that have higher metabolism are more sensitive to radiation.

46
Q

Which is the most RADIOSENSITIVE cell

A

small lymphocyte

47
Q

examples of radiosensitive cells

A

blood cells
immature reproductive cells
young bone cell

48
Q

radiosensitive tissues and its sensitivity

A 
lymphocyte - high 
bone marrow - high 
reproductive cells- high 
intestinal mucosa- high 
skin - fairly high 
lens of eye - fairly high 
oral mucosa - fairly high
49
Q

Radioresistant tissues or organs and its resistant levels

A 
Muscle tissue - Low
Nerve tissue - Low
Mature bone & cartilage - fairly low 
salivary gland - fairly low 
thyroid gland - fairly low 
kidney - fairly low 
liver - Fairly low.
50
Q

what is a critical organ ?

A

An organ that if damage dimishes a persons quality of life

51
Q

critical organs exposed in dental imaging

A

thyroid
bone marrow
skin
lens of eyes

52
Q

ICRU

A

International commision on radiation units and measurements.

53
Q

what were the special units for measurement that ICRU established ?

A
  1. exposure.
  2. Dose
  3. Dose equivalent.
54
Q

the two systems used to define radiation measurements

A
  1. Traditional System

2. SI system

55
Q

Traditional units of radiation

A

Roentgen ( R)
Radiation Absorbed Dose ( RAD)
Roentgen equivalent (IN) Man (rem)

56
Q

SI units of radiation

A

coulombs/ kilogram c/Kg
Gray (Gy)
Sievert (SV)

57
Q

exposure

A

measurement of ionization in air produced by xrays

58
Q

what is the traditional unit of exposure for xrays ?

A

Roentgen (R)

59
Q

Dose

A

Amount of energy absorbed by a tissue

60
Q

Radiation absorbed dose ( RAD)

A

Traditional unit of dose

not restricted to air and can be applied to all forms of radiation

61
Q

1 RAD = ____ Gy (gray)

A

0.01

62
Q

1 Gy= ________ RAD

A

100

63
Q

Dose equivalent

A

compares the biologic effects of different types of radiation

64
Q

Natural (background radiation) examples

A

uranium, radium, thorium, cosmic rays, radioactive potassium in food and water, radioactive material found in human body

65
Q

Radon gas

A

Single greatest source of background radiation in the USA

66
Q

The average person is exposed to how much mSv of background radiation?

A

3.1 msv

67
Q

how much human made radiation is an average person exposed to ?

A

3.1 mSv

68
Q

Examples of human made radiation

A 
luminous wrist watches
tv 
computer screens
weapons production 
fallout of atomic weapons
medical radiation
69
Q

which radiation is the greatest contributor of human made radiation?

A

medical radiation

dental imaging, Ct scan, floursocopy, radiation therapy

70
Q

What is the total radiation per year that an average human is exposed to ?

A

6.2 msV

71
Q

Risk

A

The likelyhood of adverse effects or death resulting from exposure to a hazard

72
Q

what is the potential risk of dental imaging causing fatal cancer?

A

3 in one million

73
Q

6000 mrad/ 0.06 Gy exposure to the thyroid gland can produce _____

A

cancer

74
Q

5000 mrad (0.05 Gy) exposure of the bone marrow can induce _______

A

leukemia

75
Q

250 rad (25 Gy) exposure of the skin can cause

A

erythema or skin reddening

76
Q

200 000 mrad (2 Gy) exposure of the eyes can induce __________

A

cataract formation

77
Q

ways to protect patients from exposure to radiation

A

receptor choice (use of sensors - F speed film) reduces by 60%

collimation ( rectangle collimator ) reduces 60-70 %

technique ( limited exposure by increasing target receptor and using paralleling technique)

Term 2 : Dental Radiography (29 decks)

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