Safety Flashcards
(120 cards)
1
Q
Define 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 that damages the cell itself
3
Q
Define attenuation
A
the loss of intensity in an x-ray beam as it passes through matter.
4
Q
What is the unit of exposure?
A
Air kerma or coulombs/kilogram (air kerma preferred)
5
Q
What is the unit of absorbed dose?
A
Gray
6
Q
energy absorption per kilogram of tissue irradiated
A
Joules per kilogram (1Gy= 1 J/kg)
7
Q
Gyt is what unit of measurement?
A
Gray(tissue) = unit of radiation absorbed in tissue
8
Q
Gya is what unit of measurement?
A
Gray(air) = unit of radiation absorbed in air
9
Q
What is the unit of effective dose?
A
Sievert
10
Q
Define effective dose
A
the relative risk to humans of exposure to ionizing radiation
11
Q
Define equivalent dose
A
(occupational exposure) Product of absorbed dose times the radiation weighting factor
12
Q
Define absorbed dose
A
Quantifies the biologic effects of radiation on humans and animals
13
Q
What describes patient dose?
A
absorbed dose
14
Q
What is the SI equivalent for RAD?
A
Gray (Gy)
15
Q
What is the SI equivalent for Rem?
A
Sievert (Sv)
16
Q
What is the SI unit for Roentgen (R)?
A
Coulomb per kilogram (C/kg)
17
Q
What is the SI unit for Curie?
A
Becquerel (Bq)
18
Q
Define Radioactivity
A
used to measure quantity of radioactive material (not the amount of radiation emitted but atoms decaying per second)
19
Q
SI unit for radioactivity?
A
Becquerel (Bq)
20
Q
Define stochastic effects
A
randomly occurring effects of radiation
- probability of occurrence is related to the dose of radiation
(increase dose = increase probability)
21
Q
Define deterministic effects
A
Effects become more severe based on dose
- has a threshold dose
22
Q
Define LET
A
Linear energy transfer:
The amount of energy deposited by radiation per unit length of tissue
23
Q
Define RBE
A
Relative biological effectiveness:
ability to produce biological damage (varies w/LET)
24
Q
What is direct effect?
A
radiation directly interacts with DNA in the cellular nucleus
25
What is indirect effect?
radiation interacts with water molecules in the cytoplasm of the cell
26
define radiolysis of water
radiation energy is deposited in the water of the cell resulting in an ion pair (positively charged water molecule and a free electron)
27
Law of Bergonie and Tribondeau
cells are most sensitive to radiation when they are immature, undifferentiated and rapidly dividing
28
What are the early somatic effects of radiation?
-Hematopoietic syndrome
- gastrointestinal syndrome (GI)
- Central nervous system
29
What are the late somatic effects of radiation?
-carcinogenesis
- cataractogenesis
- embryologic effects
- thyroid disfunction
- life span shortening
30
cardinal principles of radiation protection
time, distance, shielding
31
Define mean marrow dose
average dose of radiation to bone marrow
32
Unit of measurement for air kerma
gray (air) Gya
33
Calculate dose equivalent
(absorbed dose) x (radiation weighting factor)
Equation: (Sv) = (Gy) x (Wr)
34
What is Radiation weighting factor?
considers the biological impact of the type and energy of the the radiation used
35
What is the radiation weighting factor for x-rays/gamma rays?
Wr=1
36
What is tissue weighting factor?
considers the relative radiosensitivity of the organ or body part being irradiated
37
Unit of measurement for effective dose?
Sievert (Sv)
38
Unit of measurement of equivalent dose?
Sievert (Sv)
39
Calculate the effective dose
(absorbed dose) x (radiation weighting factor) x (tissue weighting factor)
Sv = (Gy) x (Wr) x (Wt)
40
What is the best protection against radiation exposure?
distance
41
Define Primary radiation
radiation exiting the x-ray tube
42
define exit radiation
xrays that emerge from the patient and strike the image receptor
(consists of primary and scattered photons)
43
Define heterogeneous beam
x-ray beam that has photons with different energies
44
Describe Photoelectric interaction
incident photon interacts with an inner orbital (K or L shell) electron. All energy is deposited into electron and is ejected from orbit able to ionize other atoms
*photon is "absorbed"*
45
Describe photoelectric effect
- The ejected electron from the inner shell leaves a vacancy
- electrons from the adjacent orbit drops down to fill the void
- as electron drops, excess energy is shed and released as a secondary photon
46
How are characteristic photons made?
through the photoelectric effect
47
Are Characteristic photons high or low energy
low energy
48
Describe Compton interaction
- incoming x-ray photon strikes an outer shell electron
- partial energy transfer to the electron
- electron is ejected from orbit
49
What is the compton electron?
The outer shell electron that is ejected during compton interaction
50
In the compton effect, what happens to the photon after the interaction with an outershell electron?
The photon continues on an alternate path with less energy causing the wavelength of the photon to be longer.
51
Coherent scatter is also known as?
classical scatter
52
Coherent scatter is produced by what type of photons?
low energy x-ray photons
53
Describe coherent scatter
- low energy x-ray photons do not remove but vibrate electrons
- through the vibration energy equal to original photon is emitted
- no ionization occurs
- may cause fog on images if kVp is higher than 70
54
What kVp does coherent scatter have no effect on?
<70 kvp
55
Describe Pair production
- involves an interaction between the incoming photon and the atomic nucleus
- must be high energy photon
- does not occur in radiography
56
What are the two primary photon - tissue interactions in diagnostic x-ray?
photoelectric and compton
57
What dose response relationship indicates the following:
- no level of radiation is completely safe
- a response occurs at every dose
- degree of response to exposure is directly proportional to amount of radiation recieved
Linear - non threshold relationship
58
Describe Linear - threshold relationship
- lower doses (below threshold) are expected to provide no response
- if threshold exceeded, response is directly proportional to dose received
59
What dose response relationship indicates the following:
- lower doses (below threshold) are expected to provide no response
- if threshold is exceeded the response is not directly proportional to the dose received and is increasingly effective per unit dose
nonlinear - nonthreshold relationship
60
Descrive nonlinear-nonthreshold relationship
- no level of radiation can be considered completely safe
- response occurs at every dose
- degree of response is not directly proportional to the dose recieved
- the effect is large even with a small increase of dose
61
What is the annual effective dose limit for occupational workers?
50 mSv
62
What is the annual equivalent dose limit for occupational workers lens of eye
150 mSv
63
What is the annual equivalent dose limit for occupational workers skin, hands and feet
500 mSv
64
Equation for Cumulative effective dose limit?
Age (in yrs) X 10 mSv
65
What is the annual effective dose for general public?
5 mSv
66
What is the maximum total equivalent dose for the gestation period?
5 mSv
67
What is the equivalent dose limit per month of an embryo-fetus?
0.5 mSv
68
What does RBE stand for?
Relative biologic effectiveness
69
Define RBE
The ability to produce biological damage (varies with LET)
70
Define somatic cells
not germ or reproductive cells
71
Somatic cells have what type of division process?
Mitosis
72
Define Germ cells
reproductive cells (sperm or ovum)
73
What type of division process is for germ cells?
meiosis
74
Exposure to somatic cells may result in what?
disruption in the ability of the organism to function
75
Exposure to germ cells may result in?
mutations that can be passed on to further generations
76
What is direct effect?
Radiation transfers its energy directly to the DNA or RNA
77
What are the results of direct effect?
- no effect (most common)
- alternation of cell structure and function
- cell death
- cell line death (failure of organ development)
- mutations, cancer, abnormal formations
78
What is indirect effect?
- Radiation energy interacting with water molecule
- resulting in a positively charged whater molecule (HOH+) and a free electron
- free radicals cause biological damage
79
What are the results of indirect effect?
- no effect (most common)
- formation of free radicals
- formation of (H2O2) hydrogen peroxide
80
What are free radicals?
highly reactive ions that have an unpaired electron in the outer shell
81
Most radiation induced damage to the body is a result of indirect or direct effect?
indirect - body is mostly water
82
What does OER stand for?
Oxygen enhancement ratio
83
Define OER?
cells that are more oxygenated are more susceptible to radiation damage
84
At what whole body dose dose the blood cell count begin to diminish?
25 rads
85
What is the most radiosensitive blood cell in the body?
lymphocytes
86
What is the radiosensitivity of epithelial tissue?
highly radiosensitive, divides rapidly
87
What is the radiosensitivity of muscle?
relatively insensitive, specialized cell (lacks division)
88
What is the radiosensitivity for adult nerve tissue
requires very high doses for damage response
89
What is the radiosensitivity of reproductive cells?
immature sperm cells = highly radiosensitive
ova and fetus = highly radiosensitive
90
Early deterministic effects
- erythema (skin reddening)
- epilation (hair loss)
- decreased blood count
91
What can occur from acute radiation syndrome?
- hematopoietic syndrome
- GI syndrome
- central nervous system (cerebrovascular syndrome)
92
Define Hematopoietic syndrome
decrease in total number of all blood cells
93
Define GI syndrome
death from serious damage to the lining of the intestines
94
Define Cerebrovascular syndrome
complete failure of nervous system and results in death from increased fluid in the brain
95
Late deterministic effects
-cataractogenesis (cataracts to form)
- thyroid problems (cancer or disfunction)
- fertility problems
96
Probabilistic effects is the same as?
Stochastic effects
97
Stochastic effects include?
- carcinogenesis
- nonmalignant radiodermatitis
- embryologic effects (most sensitive during 1st trimester)
- genetic mutation
98
Methods for beam limitation
- collimator
- cylinder cones
- aperture diaphragm
99
True or false: low energy xrays contribute to the diagnostic image?
False: low energy xrays only contribute to patient dose
100
What is beam hardening?
the removal of low energy rays resulting in a predominantly short wavelength, high energy beam.
101
More filtration does what to patient dose?
added filtration = lower patient dose
102
What are the two types of filtration?
added and inherent
103
What are examples of inherent filtration?
- glass envelope of the x-ray tube
- insulating oil around the tube
- diagonal mirror used for positioning light
104
What are examples of added filtration?
- aluminum sheets placed in the path of the beam near the xray tube window
- mirror placed in the collimator head
105
What is total filtration?
the overall total of inherent plus added filtration
106
what must be the total filtration aluminum equivalent for xray tubes?
2.5 mm aluminum equivalent
107
Define half-value layer
The amount of filtration that reduces the intensity of the xray beam to half its original value
108
The use of a grid increases what?
increase in patient dose due to a required increase of mAs
109
What is DAP
Dose area product :
the total of air kerma striking the surface of the patient
110
What is LIH
used in fluoroscopic procedures to display the most recently acquired image on the monitor
111
What is ABC or AERC?
Automatic brightness control
Automatic exposure rate control
(both are specific to fluoro)
112
What is the inverse square law?
as distance increases radiation dose decreases
113
What is the lead equivalent for a lead apron?
at least 0.25 mm lead equivalent
114
what is the lead equivalent for a thyroid shield
0.5 mm lead equivalent
115
How to reduce compton interactions?
increase collimation
116
What is the lead equivalent of a primary protective barrier?
1/16 inch lead equivalent
117
What is OSL?
Optically stimulated luminescence dosimeters
- use aluminum oxide
- unaffected by heat and humidity
- most radiosensitive
118
What is TLD's
Thermoluminescent Dosimeters
- use lithium fluoride crystals
- medium radiosensitivity
119
What is a digital ionication dosimeter?
- has small ionization chamber
- stores electrical charge from radiation
- unaffected by environment
120
