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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
effects of radiation on salivary gland
carcinoma
26
effects of radiation on thyroid
carcinoma
27
effects of radiation on skin
Carcinoma
28
effects of radiation on eyes
cataracts
29
Total dose
Quantity of radiation received / total amount of radiation energy absorbed
30
Dose rate
Rate at which exposure to radiation occurs and absorption takes place.
31
Amount of tissue irradicated
Areas of the body exposed to radiation
32
Cell sensitivity
More damage occurs in cells that are most sensitive to radiation
33
Age
Children are more susceptible to damage than adults.
34
Short term effects
Large amounts of radiation absrobed in a short time
35
Long term effects
small amounts of radiation absorbed repeatedly in a long period of time
36
Somatic cells
all the cells in the body except for reproductive cells
37
genetic cells
The reproductive cells ( sperm ,ova)
38
Somatic effects
seen in a person who has been irradicated. Major somatic effects includes induction to cancer such as leukemia.
39
Genetic mutation
Does not effect the exposed individual but effects future generations
40
Somatic mutations
Affects exposed individual but does not effect future generations.
41
Radiosensitive
Cells that are sensitive to radiation
42
radioresistant
cell that is resistant to radiation
43
Mitotic activity
Cells that divide frequently are more sensitice to radiation
44
Cell differentation
cells that are immature or not highly specialized are more sensitive to radiation
45
Cell metabolism
cells that have higher metabolism are more sensitive to radiation.
46
Which is the most RADIOSENSITIVE cell
small lymphocyte
47
examples of radiosensitive cells
blood cells immature reproductive cells young bone cell
48
radiosensitive tissues and its sensitivity
``` lymphocyte - high bone marrow - high reproductive cells- high intestinal mucosa- high skin - fairly high lens of eye - fairly high oral mucosa - fairly high ```
49
Radioresistant tissues or organs and its resistant levels
``` 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
what is a critical organ ?
An organ that if damage dimishes a persons quality of life
51
critical organs exposed in dental imaging
thyroid bone marrow skin lens of eyes
52
ICRU
International commision on radiation units and measurements.
53
what were the special units for measurement that ICRU established ?
1. exposure. 2. Dose 3. Dose equivalent.
54
the two systems used to define radiation measurements
1. Traditional System | 2. SI system
55
Traditional units of radiation
Roentgen ( R) Radiation Absorbed Dose ( RAD) Roentgen equivalent (IN) Man (rem)
56
SI units of radiation
coulombs/ kilogram c/Kg Gray (Gy) Sievert (SV)
57
exposure
measurement of ionization in air produced by xrays
58
what is the traditional unit of exposure for xrays ?
Roentgen (R)
59
Dose
Amount of energy absorbed by a tissue
60
Radiation absorbed dose ( RAD)
Traditional unit of dose | not restricted to air and can be applied to all forms of radiation
61
1 RAD = ____ Gy (gray)
0.01
62
1 Gy= ________ RAD
100
63
Dose equivalent
compares the biologic effects of different types of radiation
64
Natural (background radiation) examples
uranium, radium, thorium, cosmic rays, radioactive potassium in food and water, radioactive material found in human body
65
Radon gas
Single greatest source of background radiation in the USA
66
The average person is exposed to how much mSv of background radiation?
3.1 msv
67
how much human made radiation is an average person exposed to ?
3.1 mSv
68
Examples of human made radiation
``` luminous wrist watches tv computer screens weapons production fallout of atomic weapons medical radiation ```
69
which radiation is the greatest contributor of human made radiation?
medical radiation | dental imaging, Ct scan, floursocopy, radiation therapy
70
What is the total radiation per year that an average human is exposed to ?
6.2 msV
71
Risk
The likelyhood of adverse effects or death resulting from exposure to a hazard
72
what is the potential risk of dental imaging causing fatal cancer?
3 in one million
73
6000 mrad/ 0.06 Gy exposure to the thyroid gland can produce _____
cancer
74
5000 mrad (0.05 Gy) exposure of the bone marrow can induce _______
leukemia
75
250 rad (25 Gy) exposure of the skin can cause
erythema or skin reddening
76
200 000 mrad (2 Gy) exposure of the eyes can induce __________
cataract formation
77
ways to protect patients from exposure to radiation
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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