Mosby's Radiation Safety Flashcards
1
Q
Somatic Effects
A
effects of radiation on the body being irradiated
2
Q
Primary Radiation
A
Radiation exiting the x-ray tube
3
Q
Attenuation
A
absorption and scatter (loss of intensity) of the x-ray beam as it passes through the patient
4
Q
Heterogeneous Beam
A
X-ray beam that contains photons of many different energies
5
Q
Gray
A
unit of absorbed dose measured in joules er kilogram 1Gy=1 J/kg
6
Q
Gray A and Gray T
A
Gray A measures radiation absorbed in air Gray T measures radiation absorbed in tissue
7
Q
Sievert
A
unit of effective and equivalent dose
8
Q
Becquerel
A
unit for radioactivity
9
Q
National Academy of Sciences/National Research Council Committee on the Biological Effects of Ionizing Radiation (NAS/NRC-BEIR)
A
Organization that studies biological effects and publishes resulting data
10
Q
International Commission on Radiologic Protection (ICRP
A
Organization that publishes international radiation protection guidelines
11
Q
Nuclear Regulatory Commission (NRC)
A
Organization that enforces radiation protection standards at the federal level related to use of radioactive material
12
Q
Air Kerma
A
Unit of measure is gray, acronym for kinetic energy released in matter
13
Q
How does the radiographer best protect the patient from unnecessary exposure?
A
- by avoiding repeats
- should use smallest amount of radiation that produces a diagnostic image
14
Q
What are the two general types of radiation damage
A
- somatic- damage to the exposed individual
- genetic- damage to the genetic code of the germ cell contained in the DNA that may be passed to the next generation
15
Q
Photoelectric Interaction
A
- Photon absorption interaction
- Incident electron interacts with an inner orbital K or L electron giving all of its energy to the electron ejecting it from orbit.
- The photon is absorbed
- The ejected electron passes on the atom with an energy equal to excess passed on by the photon.
- results in increased dose to the patient
- photoelectric interaction produces contrast in the radiograph because of the differential absorption of the incoming x-ray photons in the tissues
16
Q
Compton Effect
A
- Photon interacts with outer orbital electron, passing on some of its energy to the electron ejecting it from orbit.
- The ejected electron leaves the atom with an energy equal to the excess passed on by the photon.
- The photon continues on an altered path, scattered, with less energy (longer wavelength) than before the collision.
17
Q
Coherent Scatter
A
Also known as classical scatter
1. Produced by low energy x ray photons
2. Atomic electrons are not removed but vibrate because of the deposition of energy from the photon.
3. As the electrons vibrate, the emit energy equal to that of the original photon
4. This energy travels in a path slightly different from the path of the original photon
5. Ionization has not occurred, although the photon has scattered.
6. Does not affect image less than 70 kVp
7.May have negligible effect on fog greater than 70 kVp
18
Q
Pair production
A
Does not occur in radiography. Produced at photon energies greater than 1.02 million electron volts. Involves an interaction between the incoming photon and the atomic nucleus.
19
Q
Photodisintegration
A
Does not occur in diagnostic radiography
20
Q
Linear-threshold relationship
A
indicates that at lower doses of radiation exposure (to the left of the line intersecting the x-axis) no response is expected. When the threshold is exceeded the response id directly proportional to the amount of radiation received.
21
Q
Linear- nonthreshold relationship
A
Indicates that no level of radiation can be considered completely safe. A response occurs at every dose. The degree of response to exposure is directly proportional to the amount of radiation received.
22
Q
Nonlinear- threshold relationship
A
Indicated that at lower doses of radiation exposure (to the left of the curve intersecting the x axis, no response is expected. When the threshold dose is exceeded, the response is not directly proportional to the dose received and is increasingly effective per unit dose.
23
Q
Nonlinear- nonthreshold relationship
A
Indicates that no level of radiation in considered safe. A response occurs at every dose. The degree of response in not directly proportional to the dose received. The effect is large even with a small increase in dose.
24
Q
NCRP Report #116
A
Recommends balance between the risk and benefit of using radiation for diagnostic damage. States that occupational exposure annual equivalent dose limit is 50mSv. Annual dose limit to lens of the eye is 150mSv and localized areas of the skin, hands, and feet are 500 mSv.
25
How do you find cumulative effective dose limit
Age*10mSv
26
What is the annual effective for students older than 18
50mSv
27
What is the annual effective dose for frequent exposure of the general public
1mSv
28
What the annual effective dose limit for infrequent exposure of the general public
5mSv
29
What is the total equivalent dose limit for gestation
5mSv
30
What is the equivalent dose limit per month for an embryo-fetus
0.5mSv
31
what is the level of negligible risk
0.01mSv
32
What are the three main parts of the cell
1. Nucleus
2. Cytoplasm
3. Cell membrane
33
What organelles does the cytoplasm contain
1. centrosomes- participate in cell division
2. ribosomes-synthesize protein
3. Lysosomes- Contain enzymes for intracellular digestive processes
4. Mitochondria- produce energy
5. Golgi apparatus- combines proteins with carbohydrates
6. Endoplasmic reticulum- acts as a transportation system to move food and molecules within the cell
34
What are the components of the cell?
proteins- 15%
carbohydrates-1%
Lipids- 2%
Nucleic Acid- 1%
Water- 80%
Acids, Bases, Salts(electrolytes)-1%
35
What are the phases of mitosis?
1. Prophase—nucleus enlarges
2. Metaphase—nucleus elongates
3. Anaphase—two complete sets of chromosomes
4. Telophase—separates the two sets of genetic material; division complete; 46 chromosomes in each new somatic cell
36
What happens during interphase in mitosis?
1. G1—pre-DNA synthesis
2. S—DNA synthesis
3. G2—post-DNA synthesis, preparation for mitosis
37
What are the phases of replication division in meiosis
1. G1
2. S
3. G2
4. M
38
What are the phases reduction division in meiosis
a. G1
b. No S phase
c. G2
d. M
39
Relative biologic effectiveness (RBE):
Ability to produce biological damage; varies with LET
40
What is radiation striking a cell depositing energy in DNA or RNA called
Direct effect
41
What is radiation striking a cell depositing energy in water called
Indirect effect
42
Why does most radiation pass through the body without making any interactions
Because atoms are composed mainly of empty space
43
What are some results of direct effect
1. No effect- most common
2. Disruption of chemical bonds causing alteration to sell structure and function
3. Cell Death
4. Cell line death- Death of tissues or organs that would have been produced from continued cell division had a cell survived. Can cause failure in a major organ or system to develop.
5. Faulty information passed on in the next cell division which can result in mutations, cancer, and abnormal formations.
44
Mutation
Erroneous information passed to subsequent generations via cell division that can be caused by direct effect.
45
Radiolysis of water
Occurs as radiation energy is deposited in the water of the cell resulting in an ion pair of a positively charged water molecule (HOH+) and a free electron
46
Free radicals
Highly reactive ions that have an unpaired electron in the outer shell
47
Can free radicals cause biological damage?
Yes, by transferring their excess energy to surrounding molecules or disrupting chemical reactions
48
What can free radicals chemically combine to form?
Hydrogen peroxide that causes further damage to the cell
49
What can the DNA in the cell be affected by
By free radicals or hydrogen peroxide
50
Indirect effect
1. more common than direct effect due to most of the body being water and free radicals being readily mobile in water.
2. The DNA itself is not struck by radiation.
3. Results from ionization or excitation of water molecules.
51
Target theory
States that each cell has a master molecule called DNA that directs cell activities. If DNA is inactivated the cell dies. DNA may be inactivated by direct or indirect effects. All photon-cell interactions occur by chance. Weather cell death occurred due to direct or indirect effect cannot be determined.
52
Law of Bergonié and Tribondeau
Cells are most sensitive to radiation when they are immature, undifferentiated, and rapidly dividing
53
oxygen enhancement ratio (OER)
If cells are more oxygenated, they are more susceptible to radiation damage
54
Blood Cells Radiosensitivity
A whole-body dose of 25rads depresses blood count. Lymphocytes are the most radiosensitive blood cells in the body. Stem cells in bone marrow are especially radiosensitive.
55
Is epithelial tissue radiosensitive?
Yes, It is highly radiosensitive because it divides rapidly and lines body tissue.
56
Is muscle radiosensitive?
It is relatively insensitive because of high specialization and lack of cell division
57
Are adult nerve tissues radiosensitive?
Adult nerve tissue requires doses beyond medical levels to cause damage. It is very specialized,and has no cell division.
58
At what dose does radiation increase chances of mutation in sperm cells
10rads or more
59
When does Ovarian radiosensitivity decrease
until middle age and then it increases again
60
What are Early tissue reactions (deterministic)
1. Erythema
2. Epilation (radiation damage to hair follicles
3. decreased blood count
4. Acute radiation syndrome
61
What are the levels of Acute Radiation Syndrome?
1. Hematopoietic Syndrome: Decrease in total number of all blood cells
2. GI Syndrome- Death from serious damage to the lining of the intestines
3. Central nervous system (cerebrovascular) syndrome- Causes complete failure of nervous system and results in death from increased fluid in the brain
62
What do late tissue reactions (deterministic) include
1. Cataractogenesis- causes cataracts to form
2. Thyroid- cancer or cessation of function
3. Effect on fertility
63
What do stochastic effects (probabilistic) include?
1. Carcinogenesis- radiation induced malignancy
2. Nonmalignant Radiodermatitis
3. Embryologic effects- Most sensitive during the first trimester of gestation
4. Genetic mutations
64
Doubling dose
Amount of radiation that causes the number of mutations in a population to double (is approximately 1.56 Sv for humans)
65
Collimator
1. Higher set of lead shutters is placed near the x-ray tube window to absorb off-stem (off-focus) radiation
2. Lower set of lead shutters is placed near the bottom of the collimator box to restrict the beam further as it exits
3. Collimators that automatically restrict the beam to the size of the image receptor have a feature called positive beam limitation (PBL), also called automatic collimation
66
Cylinder cones
1. Metal cylinders that attach to the bottom of the collimator
2. Used to restrict the beam tightly to a small circle
3. Cones may be used for exam of the os calcis, various skull projections, and cone-down views of vertebral bodies
4. hen cones are used, mAs must always be increased to make up for the rays attenuated by the cone
67
What are the two types of filtration
inherent and added
68
Inherent filtration
1. Glass envelope of the x-ray tube
2. Insulating oil around the tube
3. Diagonal mirror used for positioning light
69
Added filtration
1. Aluminum sheets placed in the path of the beam near the x-ray tube window
2. Mirror placed in the collimator head
70
Total filtration
1. Equals inherent plus added filtration
2. Must equal at least 2.5-mm aluminum equivalent for x-ray tubes operating at greater than 70 kVp
71
Half-value layer
Amount of filtration that reduces the intensity of the x-ray beam to half of its original value—measured at least annually by a qualified radiation physicist
72
What is the required Source-to-tabletop distance for fixed fluoroscopes
not less than 15 inches
73
What is the required Source-to-tabletop distance for portable fluoroscopes
not less than 12 inches
74
What is a dead man switch
Safety feature on fluoroscopic X-ray machines that prevents X-rays from being generated unless the operator is actively pressing a button or foot pedal
75
What should the dose at the tabletop be limited to?
To no more than 100 mGya per minute
76
What should high-level-control fluoroscopy (HLCF) during interventional procedures be limited to
To no more than 200 mGya per minute
77
Where should personnel stand during lateral or oblique fluoroscopy procedures?
On the image intensifier side of the C-arm
78
During fluoroscopy where should the radiographer wear the dosimeter?
outside of the lead apron at the level of the collar
79
Dose area product (DAP)
the total of air kerma striking the surface of the patient. It may be read on the DAP meter on the fluoroscopic monitor
and it is expressed as mGy-cm2.
80
Last image hold (LIH)
Safety feature that keeps the most recently acquired fluoroscopic image displayed on the monitor without continued radiation exposure to the patient
81
Automatic brightness control (ABC) or automatic exposure rate control (AERC)
. kVp and mA are automatically adjusted during fluoroscopy, which keeps image brightness level
82
Mean marrow dose (MMD)
Average dose to active bone marrow
83
What is the equivalent dose of most x-ray exams?
less than 0.01 mSv. Radiation doses of less than 0.01 mSv to the embryo or fetus are considered lower risk
84
Distance
Most effective protection from ionizing radiation
85
What is dose governed by
The inverse square law
86
How does inverse square law work?
If the exposure is 5 mGya at a distance of 3 feet, stepping back to a distance of 6 feet causes the exposure to decrease to 1.25 mGya
87
What lead apron should be worn during fluoroscopy
A lead apron of at least 0.25-mm lead equivalent must be worn (0.5-mm lead equivalent should be worn) during exposure to scatter radiation
88
What thyroid shield should be worn during fluoroscopy
a thyroid shield of at least 0.5-mm lead equivalent should be worn for fluoroscopy
89
What is the source of radiation exposure to radiographer
scatter radiation produced by Compton interactions in the patient
90
The greatest exposure to the radiographer occurs during what
fluoroscopy, portable radiography, and surgical radiography
91
What is the scattered beam intensity of the primary beam at a 90 degree angle at a distance of 1m from the patient
Scattered beam intensity is about 1⁄1000 the intensity of the primary beam at a 90-degree angle at a distance of 1 m from the patient
92
Do high speed image receptors reduce the amount of scatter
Yes, due to decreased quantity of radiation needed for exposure
93
Primary protective barriers
1. Consist of 1⁄16 -inch lead equivalent
2. Located where primary beam may strike the wall or floor
3. If in the wall, extend from the floor to a height of 7 feet
94
Secondary protective barriers
1. Consist of 1/32-inch lead equivalent
2. Extend from where primary protective barrier ends to the ceiling, with ½-inch overlap
3. Located wherever leakage or scatter radiation may strike
95
X-ray control booth
1. is a secondary protective barrier
2. Exposure switch must have a cord short enough that the radiographer has to be behind the secondary protective barrier to operate the switch
3. Lead window by control booth is usually 1.5-mm lead equivalent
96
What are the determinants of barrier thickness
Distance, occupancy, workload, and use factor
97
What is the minimum leakage an x-ray tube housing can have?
Leakage radiation may not exceed 1 mGya per hour at a distance of 1 m from the housing
98
What is the minimum lead equivalent required for the protective curtain in fluoroscopy?
0.25-mm lead equivalent
99
What is the minimum lead equivalent required for the bucky slot shield in fluoroscopy?
0.25-mm lead equivalent
100
Portable Equipment
1. Exposure switch must be on a cord at least 6 feet long
2. Lead aprons must be worn if mobile barriers are unavailable
3. Least scatter is at a 90-degree angle from patient
4. Apply the inverse square law to reduce dose by using exposure cord at full length
101
Optically stimulated luminescence (OSL) dosimeters
1. Use aluminum oxide to record dose
2. Radiation absorbed causes electrons to be trapped
3. Aluminum oxide layer is stimulated by a laser beam after wear period
4. Electrons release energy as visible light
5. Light is in direct proportion to the amount of radiation received
6. Measures exposures as low as 10 μGya
7. Relatively unaffected by temperature and humidity
8. Can be worn 3 months at a time
9. Can be reanalyzed multiple times, if necessary
10. Exposures below 10 μGya are reported as minimal
102
Thermoluminescent dosimeters (TLDs)
1. Use lithium fluoride crystals to record dose
2. Electrons of crystals are excited by radiation exposure and release this energy on heating
3. Energy released is visible light, which is measured by a photomultiplier tube
4. Light is in direct proportion to the amount of radiation received
5. TLDs are used mainly in ring badges worn by nuclear medicine technologists
6. Measure exposures as low as 50 μGya
7. Relatively unaffected by temperature and humidity
8. Can be worn for up to 3 months
9. TLDs and equipment used to read them are expensive
10. Exposures below 50 μGya are reported as minimal
103
Digital ionization dosimeter
1. Houses a small ionization chamber
2. Stores the electrical charge resulting from radiation exposure
3. Measure exposures as low as 50 μGya
4. Transfers the dose readout via physical or wireless connection to a computer
5. Provides instant dose information
6. Lightweight
7. Very little chance of damage if mishandled
8. Unaffected by environmental conditions
104
Handheld ionization chamber
1. Used to measure radiation in an area, storage areas for radioisotopes, doses traveling through barriers, and patients who have radioactive sources within them
2. Not used to monitor short exposure times
3. Measures exposure rates as low as 10 μGya per hour
4. Operates with internal gas being ionized when struck by radiation
105
Geiger-Mueller detector
1. Used to detect radioactive particles in nuclear medicine facilities
2. Sounds audible alarm when struck by radiation, with sound increasing as radiation becomes more intense
3. Meter reads in counts per minute
