Rad 260: Safety Flashcards
1
Q
What is ionizing radiation?
A
Radiation that possesses the ability to remove electrons from atoms by a process called ionization.
2
Q
What are somatic effects?
A
Effects of radiation on the body being irradiated.
3
Q
What are genetic effects?
A
Effects of radiation on the genetic code of a cell; affects the next generation.
4
Q
What is natural background radiation?
A
Radiation contained in the unpolluted environment.
5
Q
What is artificially produced radiation?
A
Also called man-made radiation (e.g., medical x-rays).
6
Q
What is primary radiation?
A
Radiation exiting the x-ray tube.
7
Q
What is exit radiation?
A
X-rays that emerge from the patient and strike the image receptor.
Also known as remnant radiation or image-producing radiation.
8
Q
What is attenuation?
A
Absorption and scatter (loss of intensity) of the x-ray beam as it passes through the patient.
9
Q
What is a heterogeneous beam?
A
X-ray beam that contains photons of many different energies.
10
Q
What is the photoelectric effect?
A
Absorption of x-ray photons in the atoms of the body.
11
Q
What is the Compton effect?
A
Scatter of x-ray photons from the atoms of the body.
12
Q
What is air kerma?
A
Unit of exposure.
13
Q
What is a gray?
A
Unit of absorbed dose, measured in joules per kilogram (J/kg); 1 Gy = 1 J/kg.
14
Q
What is graya?
A
Unit of radiation absorbed in air.
15
Q
What is grayt?
A
Unit of radiation absorbed in tissue.
16
Q
What is a sievert?
A
Unit of effective dose and equivalent dose.
17
Q
What is a becquerel?
A
Unit of activity.
18
Q
What is the NAS/NRC-BEIR?
A
Organization that studies biological effects of ionizing radiation and publishes resulting data.
19
Q
What is the ICRP?
A
Organization that publishes international radiation protection guidelines.
20
Q
What is the NCRP?
A
Organization that publishes radiation protection guidelines for the United States.
21
Q
What does the Nuclear Regulatory Commission (NRC) do?
A
Enforces radiation protection standards at the federal level related to use of radioactive material.
22
Q
What does NCRP Report #102 address?
A
Makes recommendations on equipment design and protection regarding lead shielding and fluoroscopic and mobile exposure rates.
23
Q
What does NCRP Report #116 define?
A
Defines annual exposure limits; makes recommendations pertaining to risk–benefit analysis of radiation exposure.
States that somatic and genetic effects should be kept to a minimum when radiation is used for diagnostic imaging.
24
Q
What is the effective dose limit?
A
Upper boundary dose that can be absorbed, either in a single exposure or annually, with a negligible risk of somatic or genetic damage to the individual.
25
What is the cumulative effective dose?
Lifetime occupational exposure must not exceed the radiographer’s age multiplied by 10 mSv.
26
What is equivalent dose?
Equal to the effective dose multiplied by the radiation weighting factor.
27
What does ALARA stand for?
As low as reasonably achievable; a concept of radiologic practice that encourages minimal radiation dose.
28
What are dose-response curves?
Graphs that illustrate the relationship between radiation dose and the response of the organism to exposure.
29
What are stochastic (probabilistic) effects?
Randomly occurring effects of radiation; the probability of such effects is proportional to the dose.
30
What are tissue reactions (deterministic)?
Effects of radiation that become more severe at high levels of radiation exposure and do not occur below a certain threshold dose.
31
What is linear energy transfer (LET)?
Amount of energy deposited by radiation per unit length of tissue.
32
What is relative biological effectiveness (RBE)?
Ability to produce biological damage; varies with the LET.
33
What is a direct effect of radiation?
Effect that occurs when radiation directly strikes DNA in the cellular nucleus.
34
What is an indirect effect of radiation?
Effect that occurs when radiation strikes the water molecules in the cytoplasm of the cell.
35
What is radiolysis of water?
Effect that occurs as radiation energy is deposited in the water of the cell; results in an ion pair in the cell: a positively charged water molecule (HOH+) and a free electron.
36
What is a mutation?
Erroneous information passed to subsequent generations via cell division.
37
What is the Law of Bergonié and Tribondeau?
Cells are most sensitive to radiation when they are immature, undifferentiated, and rapidly dividing.
38
What are early somatic effects of radiation?
Hematopoietic syndrome; gastrointestinal (GI) syndrome; central nervous system syndrome.
39
What are late somatic effects of radiation?
Carcinogenesis; cataractogenesis; embryologic effects; thyroid dysfunction; life span shortening.
40
What are the cardinal principles of radiation protection?
Distance, time, shielding.
41
What is the best protection against radiation exposure?
Distance.
42
What are personnel monitoring devices?
Optically stimulated luminescence (OSL) badge, thermoluminescent dosimeter (TLD), digital ionization dosimeter.
43
What is the mean marrow dose?
Average dose of radiation to the bone marrow.
44
45
What is the unit of absorbed dose?
Gray
46
What does Gray (Gya) measure?
Air kerma
47
What does Gray (Gyt) measure?
Absorbed dose in tissue
48
What is the unit of effective and equivalent dose?
Sievert (Sv)
49
What is the unit of radioactivity?
Becquerel (Bq)
50
What is ionizing radiation?
Ionizing radiation is able to remove electrons from atoms; the process is called ionization.
51
What are the potential effects of ionization?
It may cause unstable atoms, free electrons, or formation of new molecules harmful to the cell.
52
What types of cell damage can occur from ionizing radiation?
Somatic (damage to the cell itself) or genetic (damage to the cell’s genetic code).
53
What is the greatest source of natural background radiation exposure to humans?
Radon
54
What accounts for the largest increase in total dose to the population?
CT
55
How has the total radiation dose to the U.S. population changed since the 1980s?
It has doubled.
56
What does attenuation describe?
Changes in the intensity of the x-ray beam as it traverses the patient.
57
What are the two primary photon-tissue interactions significant in diagnostic x-ray procedures?
Photoelectric and Compton interactions.
58
What is the result of a photoelectric interaction?
Complete absorption of an incoming x-ray photon, producing contrast in the radiographic image.
59
What happens during a Compton interaction?
Scattering of the incoming x-ray photon occurs.
60
What is the source of exposure to the radiographer or radiologist during fluoroscopy?
Compton scatter.
61
Who publishes annual dose limits?
NCRP
62
What is the effective dose limit?
The upper boundary dose that can be absorbed with negligible risk for somatic or genetic damage.
63
What does the ALARA principle stand for?
As low as reasonably achievable.
64
What does the linear-nonthreshold relationship state?
No level of radiation can be considered completely safe; response is proportional to the amount of radiation received.
65
What are stochastic effects?
Randomly occurring effects of radiation; probability is proportional to the dose.
66
What are tissue reactions?
Deterministic effects that become more severe at high levels of radiation exposure but do not occur below a certain threshold dose.
67
What does NCRP Report #116 contain?
Recommendations for annual dose limits.
68
What is the annual effective dose limit for occupational exposure?
50 mSv
69
How is the cumulative effective dose limit calculated?
Age (in years) × 10 mSv
70
What is the annual effective dose limit for the general public?
1 mSv for frequent exposure and 5 mSv for infrequent exposure.
71
What is the effective dose limit for the embryo or fetus for all of gestation?
5.0 mSv
72
73
What are the main parts of the cell?
The main parts of the cell are the cell membrane, cytoplasm, and nucleus.
74
What does the nucleus contain?
The nucleus contains DNA.
75
What does the cytoplasm contain?
The cytoplasm contains the organelles and water.
76
What is interphase?
Interphase is the portion of the cellular life cycle that occurs before mitosis.
77
What is mitosis?
Mitosis is somatic cell division that includes four phases: prophase, metaphase, anaphase, and telophase.
78
How many chromosomes does each new cell contain after mitosis?
Each new cell contains 46 chromosomes after mitosis.
79
What is meiosis?
Meiosis is germ cell division that halves the number of chromosomes in each cell.
80
What is LET?
LET stands for the amount of energy deposited per unit length of travel of radiation passing through matter.
81
What happens to biological damage with an increase in LET?
An increase in LET results in an increase in the potential for biological damage.
82
What does RBE stand for?
RBE stands for the ability of radiation to produce biological damage; it varies with LET.
83
What is a direct effect of radiation?
A direct effect occurs when radiation transfers its energy directly to the DNA or RNA.
84
What is a mutation?
A mutation is erroneous information passed to subsequent generations via cell division.
85
What is an indirect effect of radiation?
An indirect effect occurs when radiation transfers its energy to the water in the cytoplasm, which may cause radiolysis and produce free radicals or H2O2.
86
What is the Law of Bergonié and Tribondeau?
The Law states that cells are most sensitive to radiation when they are immature, undifferentiated, and rapidly dividing.
87
What is OER?
OER stands for oxygen enhancement ratio; if cells are more oxygenated, they are more susceptible to radiation damage.
88
How does cell maturity affect radiation sensitivity?
As cells mature and become specialized, they are less sensitive to radiation.
89
Which blood cells are the most radiosensitive?
Lymphocytes are the most radiosensitive blood cells in the body.
90
Which cells in the bone marrow are especially radiosensitive?
Stem cells in bone marrow are especially radiosensitive.
91
What type of tissue is highly radiosensitive?
Epithelial tissue is highly radiosensitive.
92
Which tissue is relatively insensitive to radiation?
Muscle tissue is relatively insensitive to radiation.
93
How does adult nerve tissue respond to radiation?
Adult nerve tissue requires very high doses of radiation to cause damage and is relatively insensitive to radiation.
94
What is the radiosensitivity of immature sperm cells?
Immature sperm cells are very radiosensitive.
95
What is the radiosensitivity of ova in female fetuses and children?
Ova in female fetuses and children are very radiosensitive.
96
How does the radiosensitivity of ova change with age?
Ova radiosensitivity decreases until near middle age, then increases again.
97
What are somatic effects?
Somatic effects manifest in the individual being exposed.
98
What are early tissue effects of radiation exposure?
Early tissue effects include hematopoietic syndrome, GI syndrome, central nervous system syndrome, erythema, epilation, and decreased blood count.
99
What are late tissue effects of radiation exposure?
Late tissue effects include cataractogenesis and embryologic effects.
100
What are stochastic effects?
Stochastic effects include carcinogenesis and genetic effects.
101
What are genetic effects?
Genetic effects manifest in the next generation due to DNA damage and follow a linear-nonthreshold curve.
102
What is the doubling dose?
The doubling dose is the amount of radiation that causes the number of mutations in a population to double; estimated to be 1.56 Sv for humans.
103
What does ALARA stand for?
ALARA stands for 'As Low As Reasonably Achievable' principle in radiation protection.
104
What are beam limiters?
Beam limiters include collimators, cylinder cones, and aperture diaphragms.
105
What is PBL?
PBL stands for Positive Beam Limitation, or automatic collimation.
106
What does beam filtration do?
Beam filtration removes long-wavelength rays; total filtration must be at least 2.5-mm aluminum equivalent.
107
What are exposure factors?
Exposure factors include using optimum kVp for the part and the lowest practical mAs.
108
What do grids do in radiography?
Grids remove scatter radiation from the exit beam but increase total dose to the patient due to increased mAs needed.
109
What is the minimum source-to-skin distance for portable radiography?
The minimum source-to-skin distance for portable radiography is 12 inches.
110
What should be done during fluoroscopy?
Use intermittent fluoroscopy.
111
What is the minimum source-to-tabletop distance for fixed fluoroscopes?
The minimum source-to-tabletop distance for fixed fluoroscopes is 15 inches.
112
What is the minimum source-to-tabletop distance for portable fluoroscopes?
The minimum source-to-tabletop distance for portable fluoroscopes is 12 inches (15 inches preferred).
113
What should be monitored during fluoroscopy?
Monitor the fluoroscopy timer that must sound an alarm after 5 minutes (300 seconds) of beam-on time.
114
What type of foot switch is required for fluoroscopy?
The fluoroscopy foot switch must be of the dead-man type.
115
What is the limit for fluoroscopy dose at the tabletop?
Fluoroscopy dose at the tabletop is limited to no more than 100 mGya per minute.
116
What does MMD stand for?
MMD stands for the average dose to active bone marrow.
117
What are the cardinal principles of radiation protection?
The cardinal principles of radiation protection are time, distance, and shielding; distance is the best protection.
118
What governs dose in radiation exposure?
Dose is governed by the inverse square law.
119
What is the minimum lead equivalent for a lead apron?
A lead apron must be at least 0.25-mm lead equivalent; 0.5-mm is preferred.
120
What should radiographers avoid?
Radiographers must never be exposed to the primary beam.
121
What is the source of radiation exposure to radiographers?
The source of radiation exposure is scatter radiation produced by Compton interactions in the patient.
122
What is the intensity of scattered beam at a distance of 1 m from the patient?
Scattered beam intensity is about 1/1000 of the intensity of the primary beam at a 90-degree angle.
123
What does beam collimation do?
Beam collimation helps reduce the incidence of Compton interactions, resulting in decreased scatter from the patient.
124
What are primary protective barriers?
Primary protective barriers must be at least 1/16-inch lead equivalent and extend from the floor to a height of 7 feet.
125
What are secondary protective barriers?
Secondary protective barriers must be at least 1/32-inch lead equivalent and extend from the primary protective barrier to the ceiling with a ½-inch overlap.
126
What are the determinants of barrier thickness?
Determinants of barrier thickness include distance, occupancy, workload, and use.
127
What is an uncontrolled area?
An uncontrolled area is a general public area such as waiting rooms and stairways.
128
What is a controlled area?
A controlled area is occupied by persons trained in radiation safety and wearing personnel monitoring devices.
129
What is the limit for x-ray tube leakage?
X-ray tube leakage may not exceed 1 mGya per hour at a distance of 1 m from the housing.
130
What is the minimum lead equivalent for a fluoroscopic protective curtain?
The minimum lead equivalent for a fluoroscopic protective curtain is 0.25-mm.
131
What is the minimum lead equivalent for a Bucky slot shield?
The minimum lead equivalent for a Bucky slot shield is 0.25-mm.
132
What is required for a portable x-ray machine exposure switch?
The exposure switch must be on a cord at least 6 feet long.
133
What are OSL dosimeters?
OSL dosimeters have an aluminum oxide layer that stores energy released when exposed to a laser; they provide readings as low as 10 μGya.
134
What are TLDs?
TLDs store energy in lithium fluoride crystals released when heated; they provide readings as low as 50 μGya.
135
What does a digital ionization dosimeter measure?
A digital ionization dosimeter measures exposures as low as 50 μGya.
136
What is a handheld ionization chamber used for?
A handheld ionization chamber is used to measure radiation in an area; it measures doses of 10 μGya per hour.
137
What is a Geiger-Mueller detector used for?
A Geiger-Mueller detector is used to detect radioactive particles; the meter reads in counts per minute.
