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Radiation Physics And Safety > Final Exam > Flashcards

Final Exam Flashcards

1
Q

What are the two ways of measuring radiation?

A

Old school units and SI Units

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2
Q

What are old school units (4)?

A

Roentgen (R)
Rad
REM
Curie

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3
Q

What are SI units (4)?

A

Coulombs per kilogram (C/kg)
Gray (Gy)
Sievert (Sv)
Becquerel

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4
Q

Roentgen (R) is equal to

A

Coulombs per kilogram (C/kg)

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6
Q

What is the conversion rates of old school (e.g. rad) to SI unites (e.g. Gy)?

A

1 old school = 0.01 SI unit
100 old school = 1 SI unit

E.g. 1 rad = 0.01 Gy; 1 REM = 0.01 Sv; 1 curie = 0.01 becquerel

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7
Q

Quality factor (QF) is derived from what measurement?

A

Relative Biological Effectiveness (RBE)

  • it varies with different types of radiation
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8
Q

What is the quality factor for X-ray photons

A

1

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9
Q

What is the quality factor for gamma photons

A

1

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10
Q

What is the quality factor for beta particles

A

5

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11
Q

What is the quality factor for thermal neutrons

A

5

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12
Q

What is the quality factor for fast neutrons

A

20

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13
Q

What is the quality factor for alpha particles

A

20

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14
Q

What are the Laws of Bergonie and Tribondeau (4)?

A

Cell sensitivity depends on:

  • Age (young more sensitive)
  • Differentiation (simple cells more sensitive)
  • Mitotic rate (rapidly dividing cells more sensitive)
  • Metabolic rate ( cells that use lots of energy are more sensitive)
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15
Q

Define “absorbed dose”

A

Energy absorbed per unit mass at a given point

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16
Q

Define “organ dose”

A

The probability of stochastic effects (mainly cancer creation) as the absorbed dose averaged over an organ

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17
Q

Define “equivalent dose”

A

The organ dose corrected by a radio action weighting factor that takes account of the relative biological effectiveness of the incident radiation in producing stochastic effects

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18
Q

Define “effective dose”

A

A weighted sum of equivalent doses to all relevant tissues and organ with the purpose “to indicate the combination of different doses to several different tissues in a way thatislikelyto correlate well with the total of the stochastic effects”

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19
Q

What does kerma stand for?

A

Kinetic energy released per unit mass

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20
Q

Define “Kerma”

A

Sum of kinetic energy of all charged particles liberated per unit mass

1 Kerma is ~ rad at low energies
SI unit of Kerma = Gy

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21
Q

What kind of effects can be either somatic or genetic?

A

Stochastic

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22
Q

What is the 10-day rule?

A

Direct pelvic radiation to fertile females should be done only during the first 10 days of menstrual cycle EXCEPT in emergencies

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23
Q

What is stochastic?

A

Probabilistic, random.

The probability of experiencing the effect is proportional to the exposure volume, but the severity of the effect is not really affected.

“randomly determined; having a random probability distribution or pattern that may be analyzed statistically but may not be predicted precisely.”

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24
Q

What might be the results of a “severe stochastic effect” of exposure to radiography (3)?

A

Cancer
Leukemia
Mutagenesis (genetic effects)

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25
Q

Stochastic effects can be either _____ or ______ while nonstochastic effects are limited to ____

A

Stochastic: Somatic or Genetic

NONstochastic: somatic and seen in larger exposure quantities

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26
Low dose exposure effects fall into what category?
Stochastic
27
What does nonstochastic mean?
Deterministic, predictable The severity of the effect is proportional to the exposure volume. There is a threshold beneath which effects generally aren’t seen
28
What falls under the category of nonstochastic short-term effects (3)?
GI syndrome Hematopoietic syndrome CNS syndrome
29
What falls under the category of nonstochastic long term effects (5)?
``` Cataract formation Fibrosis Organ atrophy Loss of parenchymal cells Reduced fertility, sterility ```
30
Radiation exposure in the first 14 days of pregnancy increase risk of:
Spontaneous abortion
31
Radiation exposure in days 15-50 of pregnancy increase risk of
Organ/organ system mutations = birth defects
32
Radiation exposure in days 50-280 increase risk of
Growth retardation and development of cancers early in life
33
Describe threshold vs non-threshold exposure/effect models
Threshold — below x-threshold NO negative effect occurs Non-threshold — there is not threshold. Any exposure = train wreck.
34
Explain linear versus non-linear exposure model once effects begin to occur
Linear — risk rate increases in linear way Non-linear — risk rate changes depending on how much dose is delivered
35
What is the hypothesis about radiation hormesis?
Radiation can be good for you in small doses
36
Hormesis model is a variant of what model?
Threshold model
37
Man-made radiation exposure rose to ______ of annual radiation dose per capita in 2006. What advanced imaging technique accounts for most of this increase?
1/2; CT scanning | The rise is mostly due to diagnostic imaging dose per capita which worse about 6 times the amount from 1980s
38
What is ALARA principle?
As Low As Reasonably Achievable
39
What is a personnel dosimeter?
A device for monitory individual occupationally exposed workers
40
What is the more commonly used dosimeter by occupationally exposed individuals?
OSLs (optically stimulated luminescence)
41
Exposing a fetus to _______ mGy (____ rad) adds about _____ cases per 1,000 deliveries to the risk of spontaneous abortion, major malformation, mental retardation, and childhood malignancy.
50 mGy / 5 rad | 0.17 cases OR 1 case per 6K deliveries
42
Below _________ exposure to fetus, there is little chance above baseline that miscarriage can be attributed to radiation exposure Full disclaimer: this sentence confuses me
100 mGy (10 rads)
43
What is the chance an exposed fetus will NOT develop childhood cancer or leukemia with a fetal radiation dose of 0.05 Gy (5 rads)?
99%
44
Low dose is now considered to be an exposure to ionizing radiation of:
0-20 rem 3-5 are normal in chiropractic x-ray studies which is well within the low dose levels of exposure Helical CTs are capable of reaching dose levels outside of this
45
T/F pregnancy CANNOT occur during any part of a cycle
FALSE.
46
Pregnancy tests are better indicators than patients. Pregnancy tests require ________ before they can be administered.
Informed consent
47
The maximum allowed exposure per year for a non-pregnant radiation worker is
50 mGy (5 rem)
48
The maximum allowed exposure per year for a pregnant radiation worker is: The maximum allowed exposure per year for a people under 18 yo who is occupationally exposed is: HINT: its the same for these groups of people
5 mGy (0.5 rem)
49
Who owns radiographs?
The facility/practitioner who took them
50
People who are occupationally exposed to radiation may need to be monitored. Why?
If the state thinks it is possible that they receive at or above 25% of annual maximum permissible dose E.g. if you are pregnant or under 18 yo your max is 5 mGy. If they think you are getting more than 1.25 mGy they can monitor you.
51
What does a positive correction factor mean?
Th machine is under-producing x-rays compared to the average or benchmark machine
52
What does negative correction factor mean?
The machine is over-producing as compared to average or benchmark machine
53
Once the TCF and part measurement are in the calculator... you can (Um, what is TCF?)
choose any kVp and the calculator will show you the correct mAs for that kVp
54
What 3 things could you do that would require you to re-calculate the machine correction factor?
- install new X-ray tube - install new auto processor - replace radiographic screens in x-ray cassettes
55
Image critique: every film should have
3 visible margins of collimation
56
Image critique: a mildly over-penetrated (too dark) image will require ____ (a percent) _____ [reduction/increase} in mAs to correct for density
30% reduction in mAs Restating the same thing: Too dark/over penetrated = reduce mAs 30%
57
Q stem1/3. If contrast is too high, the bones will be white but the soft tissues will be nearly invisible. What is the problem?
Contrast
58
Q stem 2/3. If contrast is too high, the bones will be white but the soft tissues will be nearly invisible. If this were a low density problem (ok, so now you know it’s not) what would the image look like (bones and soft tissue)
White bones accompanied by very prominent soft tissue visibility
59
Q stem 3/3. If contrast is too high, the bones will be white but the soft tissues will be nearly invisible. How would you correct this problem of too high contrast and what will it do?
Increase kVp 15%, half the mAs It creates higher energy beam
60
Image critique: Conditions that cause fluid accumulation in the lungs will require more
mAs to penetrate normal technique
61
Image critique: Conditions that cause fluid accumulation in the lungs will require how much more mAs?
50%
62
How many vertebra do you need to get in a lateral cervical spine film?
the entire C7 vertebral body must be visible.
63
Having a random probability distribution or pattern that may be analyzed statistically but may not be predicted precisely. The probability of experiencing the effect of radiation is proportional to the exposure volume, but the severity of the effect is not affected.
Stochastic effects
64
What are the characteristics of stochastic effects of radiation?
``` Random Unpredictable Low dose effects Latent period from years to decades May be somatic or genetic May cross generations Operate on non-threshold model of risk estimation ```
65
What are examples of stochastic effects of radiation?
Stochastic effects can be either somatic or genetic Ex: cancer, leukemia, genetic effects/mutagenesis
66
When are stochastic effects seen with radiation?
After low dose exposure
67
Radiation effect in which the severity of the effect is proportional to the exposure volume. There is a threshold beneath which effects generally aren’t seen
Nonstochastic
68
When are non-stochastic effects of radiation seen?
After large dose exposure in short period of time
69
What are examples of non-stochastic effects of radiation?
Effects are limited to somatic: ``` Short-term effects… - GI Syndrome - Hematopoietic syndrome - CNS syndrome Later effects can also occur: - Cataract formation - Fibrosis - Organ atrophy - Loss of parenchymal cells - Reduced fertility, sterility ```
70
What are characteristics of non-stochastic radiation effects?
Deterministic Predictable Seen with higher dose exposure Operate on threshold model of risk estimation
71
What are the 4 viable models of risk estimation (relation between exposure and effect)?
Linear non-threshold Non-linear non-threshold Linear threshold Non-linear threshold
72
What is the prevailing model for risk estimation?
Linear non-threshold model
73
What is the difference between a linear vs. non-linear exposure models of risk estimation?
Linear suggests the rate of risk is proportional and linear to dose Non-linear suggests that the rate of risk changes depending on dose delivered
74
What is the difference between threshold and non-threshold exposure/effect models?
Threshold suggests that there is a dose below which there is no negative effect Non-threshold suggests that there is no safe dose - all exposure is deleterious
75
What is radiation Hormesis
The hypothesis that radiation can be good for you at small doses (1-50 mSv). The hormesis model of risk estimation is a variant of non-linear threshold model for radiation exposure
76
What has accounted for most of the increase in per capita radiation exposure since the 1980’s?
CT scanning

Radiation Physics And Safety (8 decks)

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