Radiation Basics (Ch 1-5) Flashcards
Ch 1- Radiation History Ch 2- Radiation Physics Ch 3- Radiation Characteristics Ch 4- Radiation Biology Ch 5- Radiation Protection (277 cards)
1
Q
What is the purpose of the control panel on the x-ray machine?
A
contains an on/off switch and indicator light, an exposure button and indicator light, and control devices (time, kilovoltage and milliamperage selectors) to regulate the x-ray beam
2
Q
What is the purpose of the extension arm on the x-ray machine?
A
to suspend and allow for movement and positioning of the tubehead and house the electrical wires that extend from the control panel to the tubehead
3
Q
What is the x-ray tubehead?
A
a tightly sealed, heavy metal housing that contains the x-ray tube that produces x-rays; includes the metal housing, insulating oil, tubehead seal, x-ray tube, transformers, aluminum discs, lead collimator, and the position-indicating device
4
Q
Define the term: absorption
A
the total transfer of energy from the x-ray photon to the atom of matter through which the x-ray beam passes
(Absorption depends on the energy of the x-ray beam and the composition of the absorbing matter or tissue)
5
Q
What is the ALARA concept?
A
a concept of radiation protection that states that all exposure to radiation must be kept to a minimum, or “as low as reasonably achieveable”
6
Q
Define the term: alpha particles
A
a type of particulate radiation emitted from the nuclei of heavy metals; contain two protons and two neutrons are are positively charged
7
Q
What are aluminum discs and what are they used for?
A
discs or sheets of aluminum, usually 0.5mm thick, that are placed in the path of x-ray beam to filter out the nonpenetrating, longer-wavelength x-rays
8
Q
Define the term: amperage
A
the number of electrons that pass through a conductor; the strength of an electrical current
9
Q
What is an ampere (A)?
A
the unit of measure used to describe the number of electrons passing through a conductor (electrical current strength)
10
Q
What is the anode?
A
the positive electrode in the x-ray tube that consists of a wafer-thin tungsten plate embedded in a solid copper rod and converts electrons into x-ray photons
11
Q
Define the term: atom
A
a tiny, invisible particle that is the fundamental unit of matter
12
Q
Define the term: neutral atom
A
an atom that contains an equal number of protons and electrons
13
Q
What is the autotransformer and what is it’s purpose?
A
a voltage compensator that corrects for minor fluctuations in the current flowing through the x-ray machine
14
Q
What is the beam alignment device and what is it’s purpose?
A
a device used to align the position-indicating device in relation to tooth and receptor that positions the intraoral receptor in the mouth and retains the receptor in position during exposure; helps stabilize the receptor in the mouth and reduce the chance of movement, thus reducing the patient’s exposure to x-radiation
15
Q
Define the term: beta particles
A
fast-moving electrons emitted from the nucleus of radioactive atoms
16
Q
What is the cathode and what is it’s purpose?
A
the negative electrode in the x-ray tube that consists of a tungsten wire filament in a molybdenum cup; supplies the electrons necessary to generate x-rays
17
Q
Define the term: cathode ray
A
a stream of high-speed electrons that originates from the cathode in an x-ray tube
18
Q
What is a cell?
A
the basic structural unit of living organisms
19
Q
Define the term: cell differentiation
A
individual characteristics of a cell that determine the response of the cell to radiation exposure
20
Q
Define the term: cell metabolism
A
the physical and chemical processes of a cell that determine the response of the cell to radation exposure
21
Q
What is a circuit?
A
a path of electrical current
22
Q
What is the filament current/low-voltage circuit and what setting is it controlled by?
A
the circuit that regulates the flow of electrical current to the filament of the x-ray tube; controlled by the milliampere settings
23
Q
What is the high-voltage circuit and what setting is it controlled by?
A
the circuit that provides the high voltage required to accelerate electrons and to generate x-rays in the x-ray tube; controlled by the kilovoltage settings
24
Q
Define the term: coherent scatter/unmodified scatter
A
one of the interactions of x-radiation with matter in which the path of a low-energy x-ray photon interacts with an outer-shell electron; no change in the atom occurs and an x-ray photon of scattered radiation is produced
25
What is collimation?
the restriction of the size and shape of the x-ray beam in order to reduce patient exposure
26
What is the collimator/collimating device and what is it's purpose?
a diaphragm, usually made of lead, used to restrict the size and shape of the x-ray beam
27
Define the term: compton electron
an outer-shell electron that is ejected from the its orbit during Compton scatter; carries a negative charge
28
What is Compton scatter?
one of the interactions of x-radiation with matter in which the x-ray photon collides with a loosely bound, outer-shell electron and gives up part of its energy and continues in a different direction at a lower energy level
29
Define the term: contrast
how sharply dark and light areas are differentiated on an image; the difference in the degrees of densities between adjacent areas on a dental radiograph
30
What are the control devices on an x-ray machine?
the components of the control panel of the x-ray machine that regulate the x-ray beam, including the timer, kilovoltage an milliamperage selectors
31
What is the control panel?
a part of the x-ray machine that contains an on/off switch, an indicator light, and exposure button and control devices to regulate the x-ray beam
32
What is the copper stem and what is it's purpose?
a portion of the anode that dissipates heat away from the tungsten target
33
Define the term: coulomb (C)
a unit of electrical charge; the quantity of electrical charge transferred by 1 ampere in 1 second
34
What is a critical organ and what are some examples?
an organ that, if damaged, diminishes the quality of an individual's life (skin, thyroid gland, lens of the eye, bone marrow)
35
What are cumulative effects of radiation?
the additive effects of repeated radiation exposure
36
What is an alternating current (AC)?
a current in which electrons flow in opposite directions
37
What is a direct current (DC)?
a current in which electrons flow in one direction
38
Define the term: density
the overall darkness of an image
39
What is the direct theory of radiation?
a theory that suggest that cell damage results when ionizing radiation hits critical areas directly within the cell
40
Define the term: dose
the amount of energy absorbed by tissue
41
Define the term: total dose
the quantity of radiation received or the total amount of radiation energy absorbed
42
What is dose equivalent used for?
a measurement used to compare the biologic effects of different types of radiation
43
Define the term: dose rate
the rate at which exposure radiation occurs and absorption takes place (dose rate = dose/time)
44
What is the dose-response curve?
a curve that can be used to correlate the "response," or damage of tissues with the "dose," or amount of radiation received
45
Define the term: electrical current
the flow of electrons through a conductor used to produce x-rays
46
Define the term: electricity
the energy used as a source of power to make x-rays
47
Define the term: electromagnetic radiation
propagation of wavelike energy (without mass) through space or matter
48
Define the term: electron
a tiny negatively charged particle found outside of the nucleus in the atom
49
Define the term: energy
what occurs when matter is altered
50
What is exposure a measure of?
a measure of ionization produced in air by x-radiation or gamma radiation
51
What is exposure time?
the interval during which x-rays are produced
52
What is the extension arm?
a part of the dental x-ray machine that suspends the x-ray tubehead and houses the electrical wires that extend from the control panel to the tubehead
53
What is a radiation film badge and what is it's purpose?
a device used to measure and monitor radiation exposure; worn by persons frequently exposed to radiation
54
What is filtration?
the use of absorbing materials (aluminum) for removing the low-energy x-rays from the primary beam
55
What is added filtration?
aluminum discs inserted into the x-ray tubehead seal and collimator to absorb low-energy x-rays
56
What is inherent filtration?
occurs when the primary beam passes through the glass window of the x-ray tube, the insulating oil, and the tubehead seal
57
What is total filtration?
the combination of the inherent filtration and added filtration in an x-ray machine
58
Define the term: frequency
the number of wavelengths that pass a given point in a certain amount of time and indicates the energy of radiation
59
What are genetic cells and what are some examples?
cells that contain genes; reproductive cells (ova, sperm)
60
What are genetic effects of radiation?
effects of radiation that are not seen in the person irradiated but are passed on to future generations through genetic cells
61
Define the term: gray (Gy)
the unit for measuring absorbed dose
62
What is half-value layer (HVL)?
the thickness of material that when placed in the path of the x-ray beam, reduces the exposure by one-half
63
Define the term: impulse
a measure of exposure time (60 impulses occur in 1 second)
64
What is the indirect theory of radiation?
a theory suggesting that cell damage results from x-ray photons being absorbed with the cell, causing the formation of toxins, which, in turn, damage the cell
65
What is the insulating oil?
oil that surrounds the x-ray tube and transformers inside the tubehead
66
Define the term: ion
an electrically unbalanced particle; an atom that gains or loses an electron
67
Define the term: ionizing radiation
radiation that is capable of producing ions by removing or adding an electron to an atom; classified into two groups: particulate radiation and electromagnetic radiation
68
Define the term: kilovolt (kV)
the unit of measurement for voltage
69
Define the term: kilovoltage
in radiography, the x-ray tube peak voltage used during an exposure; measured in kilovolts
70
Define the term: kilovoltage peak (kVp)
the maximum voltage that is used during an x-ray exposure
71
Define the term: kinetic energy
energy of motion
72
What is a lead apron and what is it's purpose?
a flexible lead shield used to protect the patient's reproductive and blood-forming tissues from scatter radiation
73
What is the lead collimator and what is it's purpose?
a lead diaphragm or tubular device used to restrict the size and shape of the x-ray beam
74
What is the leaded-glass housing and what is it's purpose?
leaded-glass vacuum tube that prevents x-rays from escaping in all directions
75
What are the long-term effects of radiation?
effects of radiation that appear years, decades, or generations after exposure and are associated with small amounts of radiation absorbed repeatedly over a long period
76
Define the term: mass
weight; the physical volume or bulk of a solid body
77
Define the term: matter
anything that occupies space and has mass
78
What is the maximum accumulated dose (MAD)?
the maximum accumulated lifetime radiation dose that may be received by persons who are occupationally exposed to radiation
79
What is the maximum permissible dose (MPD)?
maximum dose equivalent that a body is permitted to receive in a specific period with little to no injury
80
What is the metal housing?
the metal body of the dental x-ray tubehead that surrounds the x-ray tube and transformers
81
Define the term: milliamperage
in radiography, the quantity of x-rays emitted from the tubehead; measured in milliamperes
82
Define the term: milliampere (mA)
a unit of measurement used to describe the intensity of an electrical current (1/1000 of an ampere)
83
What is a milliampere-second (mAs)?
a unit of radiographic exposure equal to the product of milliamperage and exposure time
84
Define the term: mitotic activity
the process of cell division that determines the response of a cell to radiation exposure
85
What is the molybdenum cup and what is it's purpose?
a portion of the cathode in the x-ray tube that focuses electrons into a narrow beam and directs the beam across the tube toward the tungsten target in the anode
86
What is a nanometer?
a measurement used for wavelength
87
Define the term: neutral atom
an atom that contains an equal number of protons and electrons
88
Define the term: neutron
an electrically neutral or uncharged particle
89
Define the term: nucleon
part of an atomic nucleus (protons, neutrons)
90
Define the term: nucleus
the central, positively charged core of an atom, composed of protons and neutrons
91
Define the term: particulate radiations
tiny particles of matter that possess mass and travel in straight lines at high speeds
92
What is the period of injury of radiation?
occurs after the latent period following exposure to radiation and can include a variety of cellular injuries
93
What is the photoelectric effect?
one of the interactions of x-radiation with matter, where the x-ray photon collides with a tightly bound, inner-shell electron and gives up all its energy to eject the electron from its orbit
94
Define the term: photon
a bundle of energy with no mass or weight that travels as a wave at the speed of light and moves through space in a straight line
95
What is the position-indication device (PID) and what is it's purpose?
an open-ended, lead-lined cylinder extending from the opening of the metal housing of the tubehead, used to aim and shape the beam
96
What is a protective barrier and what is an example?
a barrier of radiation-absorbing material used to protect the operator from the primary and scatter radiation (a wall)
97
Define the term: proton
a positively charged particle with a mass of 1
98
What is the quality of an x-ray beam and what is it controlled by?
the mean energy or penetrating ability of the x-ray beam that is controlled by the kilovoltage
99
What is quality factor (QF)?
a factor used for radiation protection purposes that accounts for the exposure effects of different types of radiation (QF = 1)
100
What is the quantity of an x-ray beam and what is it controlled by?
the number of x-rays produced in a the dental x-ray unit and is controlled by milliamperage
101
Define the term: radiation
a form of energy carried by waves or a stream of particles
102
What is background radiation and what are some examples?
a form of ionizing radiation that ubiquitous in the environment (cosmic and terrestrial radiation)
103
What is characteristic radiation?
a form of radiation that occurs when a high-speed electron dislodges from an inner-shell electron from an atom, causing ionization of the atom
104
What is electromagnetic radiation and what are some examples?
the propagation of wavelike energy through space or matter, accompanied by electric and magnetic fields (cosmic rays, gamma rays, x-rays, ultraviolet rays, visible light, infrared light, radar waves, microwaves, radio waves)
105
What is general radiation/bremstrahlung/braking radiation?
a form of radiation that occurs when speeding electrons slow down because of their interactions with the tungsten target in the anode
106
What is ionizing radiation?
radiation capable of producing ions (particulate or electromagnetic radiation)
107
What is the primary radiation/primary beam/useful beam?
the penetrating x-ray beam produced at the target of the anode and the exits the tubehead
108
Define the term: radiation leakage
any radiation, with the exception of the primary beam, that is emitted from the dental tubehead
109
Define the term: particulate radiation
tiny particles of matter that possess mass and travel in straight lines at high speeds (electrons, protons, neutrons)
110
Define the term: scatter radiation
a form of secondary radiation the results from an x-ray beam that has been deflected from its path by the interaction with matter
111
Define the term: secondary radiation
radiation created when the primary beam interacts with matter; less penetrating that primary radiation
112
What is radiation absorbed dose (rad)?
a unit for measuring absorbed dose; the traditional unit of dose equivalent to the gray (Gy)
113
Define the term: radiation biology
the study of the effects of ionizing radiation on living tissues
114
Define the term: radioactivity
the process by which certain unstable atoms or elements undergo spontaneous disintegration or decay, in an effort to attain a more balanced nuclear state
115
Define the term: radiograph
a two-dimensional representation of a three-dimensional object
116
Who is a dental radiographer?
any person who positions, exposes, and processes dental x-ray image receptors
117
Define the term: radiography
the art and science of making radiographs by the exposure of film to x-rays
118
Define the term: radiology
the science or study of radiation as used in medicine, dealing with the use of x-rays, radioactive substances, and other forms of radiant energy in the diagnosis and treatment of disease
119
What is a radioresistant cell and what are some examples?
a cell that is resistant to radiation (bone, muscle, nerve cells)
120
Define the term: rectification
the conversion of alternating current to direct current
121
Define the term: risk
the likelihood of adverse effects or death resulting from an exposure to a hazard
122
Define the term: Roentgen (R)
the traditional unit of exposure for x-rays
123
What is the Roentgen equivalent in man (rem)?
the traditional unit of the dose equivalent; the product of absorbed dose (rad) and a quality factor (QF) specific for the type of radiation
124
What are short-term effects of radiation?
effects of radiation that appear within minutes, days, or weeks and are associated with large amounts of radiation absorbed in a short time
125
Define the term: Sievert (Sv)
a unit of measurement equivalent to the rem
126
Define the term: somatic cells
all the cells in the body, with the exception of the reproductive cells
127
What are somatic effects of radiation and what are some examples?
radiation injuries that produce changes in somatic cells and produce poor health in the irradiated individual (cancer, leukemia, cataracts)
128
What are stochastic effects of radiation?
biologic effects from radiation that occur as a direct function of dose; the probability of occurrence increases with increasing absorbed dose, however, the severity of effects does not depend on the magnitude of absorbed dose
129
What is thermionic emission?
the release of electrons from the tungsten filament when the electrical current passes through it and heats the filament
130
What is the thyroid collar and what is it's purpose?
a flexible lead shield used to protect the thyroid from scatter radiation
131
What is a transformer?
a device used to increase or decrease the voltage of incoming electricity
132
What is the step-down transformer?
a device used to decrease the incoming voltage from 110 or 220 volts to the low voltage required (usually 3 to 5 volts)
133
What is the step- up transformer?
a device used to increase the incoming line voltage from 110 or 220 volts to the high voltage required (usually 65,000 to 100,000 volts)
134
What is the tubehead?
the tightly sealed metal housing that contains the dental x-ray tube; includes the metal housing, insulating oil, tubehead seal, x-ray tube, transformers, aluminum discs, lead collimator, and position-indicating device; also contains a filament used to produce electrons and a target used to produce x-rays
135
What is the tubehead seal and what is it's purpose?
the aluminum or leaded-glass covering of the tubehead that permits the exit of x-rays from the tubehead, seals the oil in the tubehead, and filters the x-ray beam
136
What is the tungsten filament?
a coiled wire of tungsten in the cathode in the x-ray tube that produces electrons when heated
137
What is the tungsten target?
a portion of the anode in the x-ray tube that serves as a focal spot and converts bombarding electrons into x-ray photons
138
Define the term: velocity
speed; in dental radiography, the speed of a wave
139
Define the term: volt (V)
unit of measure for voltage
140
Define the term: voltage
the measurement of force that refers to the potential difference between two electrical charges
141
Define the term: wavelength
the distance between the crest of one wave to the crest of the next wave; determines the energy and penetrating power of the radiation
142
Define the term: x-radiation
a high-energy radiation produced by the collusion of a beam of electrons with a metal target in an x-ray tube
143
Define the term: x-rays
a beam of energy that has the power to penetrate substances and record image shadows on photographic film or digital sensors
144
What is the x-ray tube?
a component part of the x-ray tubehead that generate x-rays, including a leaded-glass vacuum tube, cathode, and anode
145
What occurs when matter is altered?
energy
146
What are the two ways that molecules can be formed?
1) by the transfer of electrons
2) by the sharing of electrons between the outermost shells of atoms
147
In dentistry, is radiation or radioactivity used?
radiation
148
What are the two categories of ionizing radiation?
1) particulate radiation
2) electromagnetic radiation
149
What is the difference in energy between particulate radiation and electromagnetic radiation?
In particulate radiation, energy travels in straight lines at high speed. In electromagnetic radiation, energy travels in waves
150
What are the two classifications of electrons?
1) beta particles
2) cathode rays
151
What are some examples of electromagnetic radiation?
cosmic rays, gamma rays, x-rays, ultraviolet rays, visible light, infrared light, radar waves, microwaves, and radio waves
152
What are the two concepts of electromagnetic radiation?
1) wave concept
2) particle concept
153
What is the difference between velocity, wavelength, and frequency in electromagnetic radiation?
1) velocity measures the speed of the wave
2) wavelength measures the distance between the crest of one wave and another
3) frequency measures the number of wavelengths
154
Frequency and wavelength are inversely related, which means that if the frequency of the wave is high, then the wavelength will be ____
short
155
What are the two different measurable energies of electromagnetic radiation?
frequencies and wavelengths
156
From the following particles, which originates in the x-ray tube?
Alpha particles, beta particles, cathode rays, protons, or neutrons?
cathode rays
157
What is the appearance of x-rays?
X-rays are invisible and cannot be detected by any of the senses
158
What is the mass of x-rays?
X-rays have no mass or weight
159
What is the charge of x-rays?
X-rays have no charge
160
What is the speed of x-rays?
X-rays travel at the speed of light
161
What is the wavelength property of x-rays?
X-rays travel in waves and have short wavelengths with a high frequency
162
What is the path of travel for x-rays?
X-rays travel in straight lines and can be deflected/scattered
163
What is the focusing capability of x-rays?
X-rays cannot be focused to a point and always diverge from a point
164
What is the penetrating power of x-rays?
X-rays can penetrate liquids, solids, and gases. the composition of the substance determines whether x-rays penetrate or pass through or are absorbed
165
What is the absorption property of x-rays?
X-rays are absorbed by matter; the absorption depends on the atomic structure of matter and the wavelength of the x-ray
166
What is the fluorescence capability of x-rays?
X-rays can cause certain substances to fluoresce or emit radiation in longer wavelengths (visible light or ultraviolet light)
167
What is the x-rays effect on film?
X-rays can produce an image on film
168
What is x-rays effect on living tissues?
X-rays cause biologic changes in living cells
169
What is considered the "heart" of the x-ray generating system?
the x-ray tube
170
What are the two components of the cathode in the x-ray tube?
1) tungsten filament
2) molybdenum cup
171
What are the two components of the anode in the x-ray tube?
1) tungsten target
2) copper stem
172
Is the cathode in the x-ray tube a positive or negative electrode?
negative
173
Is the anode in the x-ray tube a positive or negative electrode?
positive
174
What component of the x-ray tube supplies the electrons needed to produce x-rays?
cathode
175
What component of the x-ray tube converts electrons into x-ray photons?
anode
176
In the cathode, the ____ produces electrons when heated, and the _____ focuses those electrons into a narrow beam and directs that beam toward the ______ in the anode.
tungsten filament, molybdenum cup, tungsten target
177
What are the two classifications of electrical current?
1) direct current (DC)
2) alternating current (AC)
178
What is the difference between direct electrical currents and alternating electrical currents?
Direct current occurs when the electrons flow in one direction; alternating current occurs when the electrons flow in two, opposite directions
179
Rectification is the conversion of alternating to direct electrical currents. However, what acts as a self-rectifier in dental radiology?
the x-ray tube
180
What control setting would be adjusted to increase or decrease the number of electrons passing through the cathode?
milliampereage (mA)
181
What control setting would be adjusted to increase or decrease the current passing from the cathode to the anode?
kilovoltage peak (kVp)
182
What are the two types of electrical circuits used in the production of x-rays?
1) low-voltage/filament circuit
2) high-voltage circuit
183
How many volts are used in a low-voltage/filament circuit?
3-5 volts
184
How many volts are used in a high-voltage circuit?
65,000-100,000 volts
185
Which type of circuit is controlled by the milliampere settings?
low-voltage/filament circuit
186
Which type of circuit is controlled by the kilovoltage settings?
high-voltage
187
In the production of dental x-rays, what are the three types of transformers used to adjust the electrical circuits?
1) step-down transformer
2) step-up transformer
3) autotransformer
188
A step-down transformer is used to decrease the incoming voltage from 110- or 220-line voltage to the __ -___ volts used by the filament circuit.
3-5 volts
189
A step-up transformer is used to increase the incoming voltage from 110- to 220-line voltage to the ___-___volts used by the high-voltage circuit.
65,000-100,000 volts
190
What occurs when the electrons are released from the tungsten filament and the electrical current passes through it and heats the filament?
thermionic emission
191
What part of the x-ray tube is the first to be activated when the exposure button is pushed?
the high-voltage circuit
192
When the electrons strike the tungsten target, creating kinetic energy, how much of that energy is converted to x-rays, and how much is lost as heat?
Less than 1% is converted to x-rays, the remaining 99% is lost as heat
193
What part of the x-ray tube filters out the longer wavelengths x-rays from the beam?
the aluminum disks
194
What are the two mechanisms of radiation that the kinetic energy of the electrons is converted to x-ray photons?
1) general/braking radiation (bremsstrahlung)
2) characteristic radiation
195
Approximately how much of the x-ray energy produced at the anode is classified as general/braking radiation?
70%
196
Is general/braking radiation or characteristic radiation most common in dental x-rays?
general/braking radiation
197
What are the three classifications of x-radiation?
1) primary radiation
2) secondary radiation
3) scatter radiation
198
Which type of x-radiation is more penetrating?
Primary radiation or secondary radiation
primary radiation
199
Once x-rays exit the tubehead and arrive at the patient, what are the three events that can occur with that patient?
1) x-rays can pass through the patient without any interaction
2) x-ray photons can be completely absorbed by the patient
3) x-ray photons can be scattered
200
What are the four possibilities that can occur when an x-ray photon interacts with matter?
1) no interaction
2) absorption or photoelectric effect
3) Compton scatter
4) coherent scatter
201
What percent of the interactions with matter from the dental x-ray beam accounts for the photoelectric effect?
30%
202
What type of x-radiation effect occurs mostly from scatter radiation?
Compton scatter
203
What percent of the interactions with matter from the dental x-ray beam accounts for Compton scatter?
62%
204
What percent of the interactions with matter from the dental x-ray beam accounts for coherent scatter?
8%
205
When voltage is increased, the speed of electrons is _____; then the electrons strike the target with greater force and energy, resulting in a penetrating x-ray beam with a ___ wavelength.
increased; short
206
A ___ kilovoltage should be used when the area to be examined is dense or thick.
higher
207
Increasing ____ results in a higher energy x-ray beam with increased penetrating ability.
kilovoltage peak (kVp)
208
How is density affected by increasing only the kilovoltage peak settings?
the image appears darker from an increased density
209
How is density affected by decreasing only the kilovoltage peak settings?
the image appears lighter from a decreased density
210
How is contrast affected by increasing only the kilovoltage peak settings?
the image has low contrast, meaning many shades of gray, instead of black and white
211
How is contrast affected by decreasing only the kilovoltage peak settings?
the image has high contrast, meaning many black and white areas and few shades of gray
212
What type of contrast is preferred for the detection of caries?
high contrast
213
What type of contrast is preferred for the detection of periodontal or periapical disease?
low contrast
214
When kilovoltage peak is increased by 15, exposure time should be decreased by ___.
half
215
When kilovoltage peak is decreased by 15, exposure time should be ___.
doubled
216
Why should the milliamperage setting not exceed 15 mA?
because of the excessive heat produced in the x-ray tube as a result
217
Kilovoltage peak controls ___ and milliamperage controls ____
kilovoltage = quality/wavelength/penetrating ability of the x-ray beam
milliamperage = quantity/the number of x-rays produced
218
An increase in the number of electrons that strike the anode ____ the number of x-rays emitted from the x-ray tube.
increased
219
What two settings have a direct influence on the number of electrons produced by the cathode filament?
milliamperes and exposure time
220
When milliamperage is increased, exposure time must be ____.
decreased
221
When milliamperage is decreased, exposure time must be ___.
increased
222
How is density affected by increasing only the milliamperage settings?
the image appears darker from an increased density
223
How is density affected by decreasing only the milliamperage settings?
the image appears lighter from a decreased density
224
The quality and quantity of x-rays are described together using what term?
intensity
225
Higher kilovoltage levels ____ the intensity of the x-ray beam.
increase
226
Higher milliamperage levels ___ the intensity of the x-ray beam.
increase
227
An increase in exposure time ____ the intensity of the x-ray beam.
increases
228
What is target-surface distance?
the distance from the source of radiation to the patient's skin
229
What is target-object distance?
the distance from the source of radiation to the tooth
230
What is target-receptor distance?
the distance from the source of radiation to the receptor
231
When x-rays travel away from their source of origin, does the intensity of the beam increase or decrease?
decrease
232
Is an x-ray beam more intense when it is exiting from an 8-inch position-indicating device or a 16-inch?
8-inch
233
What is used to:
-reduce the intensity of the x-ray beam
-remove the low-energy, less penetrating, longer-wavelength x-rays
-increase the mean penetrating capability of the x-ray beam
aluminum filters
234
Is all ionizing radiation harmful?
yes
235
Does all ionizing radiation produce biologic changes in living tissue?
yes
236
When x-rays are absorbed by patient's tissue, what are the two possible mechanisms of radiation injury?
- ionization
-free radical formation
237
What are the two theories of radiation injury?
-direct theory
-indirect theory
238
Which theory of radiation injury is more likely to occur and why?
indirect theory, because of the high water content of cells
239
Can radiation damage occur from dental x-rays?
Yes, although the radiation doses are extremely low
240
What are the two types of biologic effects of radiation?
-stochasitc
-nonstochastic
241
What are some examples of stochastic effects of radiation?
cancer/tumors, genetic mutations
242
What are some examples of nonstochastic effects of radiation?
erythema, loss of hair, cataract formation, decreased fertility
243
Which type of biologic effect of radiation requires larger radiation doses in order to cause serious health impairments?
nonstochastic effects
244
Following radiation exposure, what are the next three periods of radiation injury?
-latent period
-period of injury
-recovery period
245
How is the latent period of radiation injury affected by increased radiation dose?
the latent period is shorter
246
How is the latent period of radiation injury affected by decreased radiation dose?
the latent period is longer
247
Are all cellular radiation injuries permanent?
no
248
List the 5 factors that determine the degree of radiation injury
-total dose of radiation
-dose rate
-amount of tissue irradiated
-cell sensitivity
-age
249
Are children or adults more susceptible to radiation damage?
children
250
What type of radiation effects are seen within minutes, days or weeks after exposure?
short-term effects
251
What type of radiation effects are seen after years, decades or generations after exposure?
long-term effects
252
Which type of radiation effects are not seen in dentistry?
short-term effects
253
What are the two classifications of cells in the human body?
-somatic
-genetic
254
Which type of biologic effect of radiation cannot be passed on to future generations?
somatic effects
255
Which type of biologic effect of radiation does not effect the person irradiated, but instead is passed on to future generations?
genetic effects
256
List some examples of radiosensitive cells
-small lymphocyte
-bone marrow
-reproductive cells
-intestinal mucosa
-skin
-lens of the eye
-oral mucosa
257
List some examples of radioresistant cells.
-muscle tissue
-nerve tissue
-mature bone/cartilage
-salivary gland
-thyroid gland
-kidney
-liver
258
List some examples of critical organs that are affected by dental radiographs.
-skin
-thyroid gland
-lens of the eye
-bone marrow
259
What are the three factors that determine the response of a cell to radiation exposure?
-miotic activity
-cell differentiation
-cell metabolism
260
What are the three units of measurement in radiation?
-exposure
-dose
-dose equivilant
261
What are the two systems used to define radiation measurements, and which is the system used in current dental radiology?
-Traditional/Standard System
-SI System/International System of Units
The SI System is currently used
262
What are the three units of radiation measurement in the SI System?
-Coulombs/kilogram (C/kg)
-Gray (Gy)
-Sievert (Sv)
263
What are the three units of radiation measurement in the Traditional/Standard System?
-Roentgen (R)
-Radiation absorbed dose (rad)
-Roentgen equivalent (in) man (rem)
264
What is the exposure measurement of radiation for the Traditional/Standard System and the SI System?
-Traditional/Standard System = roentgen (R)
-SI System = coulomb (C)
265
What is the dose measurement of radiation for the Traditional/Standard System and the SI System?
-Traditional/Standard System = radiation absorbed dose (rad)
-SI System = gray (Gy)
266
What is the dose equivilent measurement of radiation for the Traditional/Standard System and the SI System?
-Traditional/Standard System = roentgen equivalent (in) man (rem)
-SI System = sievert (Sv)
267
What is the estimated potential risk of dental radiography inducing a fatal cancer in an individual?
approximately 3 in 1 million
268
Who is the person responsible for prescribing dental radiographs?
the dentist
269
What are the two organizations responsible for the dental radiograph procedures?
-American Dental Association (ADA)
-U.S. Food and Drug Administration (FDA)
270
What are the two basic types of position indicating devices currently used?
-rectangular
-round
271
Why is a conical-shaped position indicating device no longer used?
the pointed cone shape caused the x-rays to penetrate the plastic and produce scatter radiation
272
Which type of position indicating device is most effective in reducing a patient's exposure to radiation?
rectangular shaped
273
During radiation exposure, what must the dental radiographer avoid most to ensure the highest level of operator protection?
the primary beam
274
What is the most effective way a dental radiographer can limit x-radiation exposure?
maintaining a distance of at least 6 feet from the x-ray tubehead during exposure
275
To avoid the primary beam during exposure, how should the dental radiographer position themself in relation to the primary beam?
perpendicular to the beam
276
If the patient is having a hard time staying still during the x-ray exposure, should the dental radiographer hold the sensor in place for the patient?
no
277
What organization dictates the maximum permissible dose that an individual can receive?
National Council on Radiation Protection and Measurements (NCRP)
