Unit 1 Flashcards
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1
Q
Discuss the “dual nature” of electromagnetic radiation.
A
This is a property of x-rays in that x-rays act like waves and like particles; waves because they have measurable wavelengths and frequency, however, they behave more like matter when they interact with matter.
2
Q
Explain the relationship between electromagnetic energy, frequency and wavelength.
A
Decreasing the wavelength/increasing the frequency increases the electromagnetic energy.
3
Q
Compare the velocity, frequency and wavelength of high energy x-rays with low energy x-rays.
A
X-rays have a constant velocity in a vacuum (the speed of light). The high energy x-rays have higher frequency/shorter wavelength, while the low energy x-rays have lower frequency and longer wavelength.
4
Q
When were x-rays discovered?
A
November 8, 1895
5
Q
In what year were some of the biologically damaging effects of x-rays discovered?
A
1898
6
Q
X-rays were discovered in experiments dealing with electricity and….
A
vacuum tubes
7
Q
X-rays were discovered with they caused a barium platinocyanide coated plate to…
A
fluoresce
8
Q
X-radiation is part of which spectrum?
A
Electromagnetic
9
Q
X-rays have a dual nature, which means that they behave like both…
A
waves and particles
10
Q
The wavelength and frequency of x-rays are ____ related.
A
inversely
11
Q
What electrical charge do x-rays have?
A
None
12
Q
What is the mass of x-rays?
A
They have no mass
13
Q
The x-ray beam used in diagnostic radiography can be described as being…
A
polyenergetic
14
Q
Define electromagnetic radiation
A
Radiation that has both electrical and magnetic properties
15
Q
Define fluorescence
A
Instantaneous production of light resulting from the interaction of some type of energy and some element or compound.
16
Q
Define frequency
A
The number of waves passing a given point per given unit of time.
17
Q
Define photon
A
A small discreet bundle of energy.
18
Q
Define quantum
A
A small discreet bundle of energy
19
Q
Define wavelength
A
The distance between two successive crests or troughs in a wave.
20
Q
The 14 characteristics of x-rays
A
invisible electrically neutral no mass travel speed of light in vacuum can't be optically focused form polyenergetic (heterogeneous) beam can be produced in a range of energies travel in straight lines can cause some substances to fluoresce cause chemical changes in radiographic film can penetrate human body can be absorbed or scattered in human body can produce secondary radiation can cause damage to living tissue
21
Q
Actual focal spot size
A
The size of the area on the anode target that is exposed to electrons from the tube current. Actual focal spot size depends on the size of the filament producing the electron stream.
22
Q
Added filtration
A
The filtration that is added to the port of the x-ray tube.
23
Q
Anode
A
A positively charged electrode within the x-ray tube composed of a tungsten alloy. It consists of a target and, in rotating anode tubes, a stator and rotor.
24
Q
Anode heel effect
A
The x-ray beam has greater intensity (# of x-rays) on the cathode side of the tube, with the intensity diminishing toward the anode side. The anode heel effect occurs because of the angle of the target.
25
Cathode
A negatively charged electrode (within the x-ray tube). It comprises a filament and a focusing cup.
26
Compensating filter
Special filters added to the primary beam to alter its intensity. These types of filters are used to image anatomic areas that aren't uniform in makeup and assist in producing more consistent exposure to the image receptor.
27
Dosimeter
A device that measures x-ray exposure.
28
Effective focal spot size
Focal spot size as measured directly under the anode target. It is affected by the angle of the anode.
29
Exposure time
The length of time that the x-ray tube produces x-rays. It is set by the radiographer & is measured in milliseconds as a fraction or decimal.
30
Filament
A coiled tungsten wire that is the source of electrons during x-ray production.
31
Filament current
Heats the tungsten filament. This heating of the filament causes thermionic emission to occur.
32
Focusing cup
Made of nickel and nearly surrounds the filament. It is open at one end to allow electrons to flow freely across the tube from cathode to anode. It has a negative charge, which keeps the cloud of electrons emitted from the filament from spreading apart. it focuses the stream of electrons.
33
Half-value layer
(HVL) The amount of filtration that reduces the intensity of the x-ray beam to one half its original value is considered the best method for describing x-ray quality. It is expressed in millimeters of aluminum.
34
Heat unit
(HU) The amount of heat produced from any given exposure.
35
Inherent filtration
Filtration that is permanently in the path of the x-ray beam. Three things contribute to this: 1) the glass envelope, 2) the oil that surrounds the tube & 3) the glass envelope in the tube housing.
36
Kilovoltage
(kVp) Set by the radiographer and applied across the x-ray tube at the time the exposure is initiated, kVp determines the speed at which the electrons in the tube current move. It also affects the quantity of x-rays.
37
Leakage radiation
any x-rays, other than the primary beam, that escape the tube housing.
38
Line focus principle
Describes the relationship between the actual and effective focal spots in the x-ray tube. A smaller target angle produces a smaller effective focal spot.
39
Milliamperage
(mA) The unit used to measure the tube current.
40
Off-focus radiation
Occurs when projectile electrons are reflected and x-rays are produced outside the focal spot.
41
Rotor
A device in the x-ray tube that causes the target to rotate rapidly during x-ray production.
42
Space charge
The electrons liberated from the filament during thermionic emission that form a cloud around the filament.
43
Space charge effect
The tendency of the space charge not to allow more electrons to be boiled off of the filament.
44
Stator
An electric motor that turns the rotor at a very high speed during x-ray production.
45
Target
A metal that abruptly stops electrons in the tube current, allowing the production of x-rays.
46
Thermionic emission
The boiling off of electrons from the cathode filament.
47
Total filtration
The sum of the x-ray tube's added and inherent filtration.
48
Trough filter
A double-wedge compensating filter added to the primary beam to produce more consistent exposure to the image receptor.
49
Tube current
The flow of electrons from cathode to anode, measure in milliamperage (mA).
50
Voltage ripple
The amount of consistency in voltage waveforms during x-ray production.
51
Wedge filter
The most common type of compensating filter. The thicker part of the wedge filter is lined up with the thinner portion of the anatomic part that is being imaged, allowing fewer x-ray photons to reach that end of the part.
52
X-ray emission spectrum
The range and intensity of x-rays emitted.
53
What is the source of electrons during x-ray production?
The filament.
54
What is the part of the anode that is struck by the focused stream of electrons coming from the cathode, which stops the electrons and creates the production of x-rays?
The target.
55
What is the rotating anode made of? Why?
Tungsten. It has a high melting point and high atomic number.
56
What happens on the cathode and anode sides when the prep button is activated?
Cathode: Filament current heats filament, electrons are boiled off the filament (thermionic emission), the electrons gather together around the filament (space charge), the negatively charged focusing cup keeps the electron cloud focused together, the number of electrons in the space charge is limited (space charge effect).
Anode: The rotating target begins to turn rapidly, quickly reaching top speed.
57
After activation of the rotor, what happens on the cathode and anode sides when the exposure is initiated?
Cathode: High negative charge strongly repels electrons, these electrons stream away from the cathode and toward the anode (tube current).
Anode: High positive charge strongly attracts electrons in the tube current, the electrons strike the anode, x-rays are produced.
58
What direction do electrons flow in the x-ray tube?
From cathode to anode. This is called the tube current & is measured in milliamperes (mA).
59
How much of the kinetic energy is converted to heat and how much is converted to x-rays?
>99%
| <1%
60
If you increase the kilovoltage what happens to the speed of the electrons traveling from the cathode to the anode (tube current)?
It also increases.
61
As the milliamperes are increased what happens to the quantity of the x-rays produced?
It also increases.
62
What does the line focus principle describe?
It describes the relationship between the actual focal spot, where the electrons in the tube current hit the target and the effective focal spot, the same area as seen from directly below the tube.
63
How are heat units calculated?
HU=mA x time x kVp x generator factor
64
Electrons interact with what to produce x-rays and heat?
Target
65
The cloud of electrons that forms before x-ray production is referred to as what?
Space Charge
66
The burning or boiling off of electrons at the cathode is referred to as what?
Thermionic emission
67
Which primary exposure factor influences both the quality and quantity of x-ray photons?
kVp
68
The unit used to express tube current is what?
mA
69
what percentage of kinetic energy is converted to heat when moving electrons strike the anode target?
>99%
70
The intensity of the x-ray beam is greater on which side of the tube?
The cathode side
71
According to the line focus principle, as the target angle decreases what happens?
The effective focal spot decreases
72
How much mAs is produced when the radiographer sets 70 kVp, 600 mA and 50 ms?
30 mAs
73
Increasing the kVp results in what?
x-rays with higher energy and more x-rays
74
Total filtration in the x-ray beam includes what?
inherent filtration and added filtration
75
How many heat units result from an exposure made on a single phase x-ray unit using 400 mA, 0.2 second and 70 kVp?
5600 HU
76
Describe the relationship kilovoltage has on the x-ray beam.
Higher kilovoltage (kVp) increases the speed of the electron beam, which increases the penetrability of the x-ray beam. The lower the kVp, the slower the electron beam and the less penetrable the x-ray beam.
77
Describe the relationship milliamperage has on the x-ray beam.
The more the milliamperage, the higher number of electrons in the tube current and the more x-rays are produced. The lower the mA, the fewer the electrons in the tube current and the fewer x-rays produced.
78
Describe the relationship exposure time has on the x-ray beam.
Exposure time is the number of seconds (or milliseconds) that the tube can produce x-rays. The longer the exposure time, the higher the number of x-rays produced. The shorter the exposure time, the lower the number of x-rays produced.
79
Describe the relationship mAs has on the x-ray beam.
If the mAs (milliamperage x seconds) is higher, the number of x-rays produced is higher. If the mAs is lower, the number of x-rays produced is lower.
80
Absorption
As the energy of the primary x-ray beam is deposited within the atoms comprising the tissue, some x-ray photons are completely absorbed. Complete absorption of the x-ray photon occurs when it has enough energy to remove an inner-shell electron. (photoelectric interaction)
81
Active layer
The radiation-sensitive and light-sensitive layer of the film.
82
Artifact
Any unwanted image on the radiograph
83
Attenuation
Reduction in the energy or # of the primary x-ray beam as it passes through anatomic tissue
84
Brightness
The amount of luminance (light emission) of a display monitor
85
Coherent scattering
An interaction that occurs with low-energy x-rays, typically below the diagnostic range. The incoming photon interacts with the atom causing it to become excited. The x-ray does not lose energy but changes direction.
86
Compton effect
The loss of energy of the incoming photon when it ejects and outer-shell electron from the atom. The remaining low-energy x-ray photon changes direction and may leave the anatomic part.
87
Compton electron
The ejected electron resulting from the Compton effect interaction
88
Contrast resolution
The ability of the image receptor to distinguish between objects having similar subject contrast.
89
Densitometer
A device used to determine numerically the amount of blackness on the radiograph
90
Density
The amount of overall blackness of the processed image
91
Diagnostic densities
The appropriate range of optical densities
92
Differential absorption
A process whereby some of the x-ray beam is absorbed in the tissue, and some passes through (transmits) the anatomic part
93
Distortion
Results from the radiographic misrepresentation of either the size (magnification) or the shape of the anatomic part
94
Dynamic range
Refers to the range of exposure intensities an image receptor can accurately detect
95
Elongation
Refers to images of objects that appear longer than the true objects
96
Emulsion
The radiation-sensitive and light-sensitive layer of the film
97
Exit radiation
When the attenuated x-ray beam leaves the patient, the remaining x-ray beam is composed of both transmitted and scattered radiation
98
Exposure intensity
The amount and energy of the x-rays reaching an area of the image receptor
99
Fog
Scatter exit radiation (Compton interactions) that reaches the image receptor and creates unwanted exposure on the radiographic image
100
Foreshortening
Refers to images that appear shorter than the true objects
101
Grayscale
The number of different shades of gray that can be stored and displayed by a computer screen
102
High contrast
A radiograph with few densities but great differences among them is said to have high contrast
103
Image receptor
(IR) A device that receives the radiation leaving the patient
104
Intensity of radiation exposure
The quantity of x-rays reaching an area of the image receptor
105
Ionization
The ability to remove (eject) electrons; a property of x-rays
106
Latent image
The invisible image that exists on film after the film has been exposed but before it has been processed
107
Long-scale contrast
(Low contrast) A radiograph with a large number of densities but little differences among them is said to have long-scale or low contrast.
108
Low contrast
(Long-scale contrast) A radiograph with a large number of densities but little differences among them is said to have long-scale or low contrast.
109
Magnification
An increase in the image size of the object compared with its true or actual size. Aka: size distortion
110
Manifest image
(Visible image) The visible image after processing
111
Matrix
A digital image is displayed as a combination of rows and columns (array) of small, usually square, "picture elements" called pixels
112
Optical density
(OD) A numeric calculation that compares the intensity of light transmitted through an area on the film to the amount of light originally striking (incident) the area. Aka: radiographic or film density.
113
Photoelectric effect
Complete absorption of the incoming x-ray photon occurs when it has enough energy to remove( eject) an inner-shell electron. The ionized atom has a vacancy, or electron hole, in it's inner shell, and an electron from an outer shell drops down to fill the vacancy
114
Photoelectron
The ejected electron resulting from ionization during the photoelectric effect
115
Pixel density
The number of pixels per unit area
116
Pixel pitch
The pixel spacing or distance measured from the center of a pixel to an adjacent pixel
117
Pixels
The smallest component of the matrix. Aka: picture elements
118
Quantum noise
Visible as brightness or density fluctuations on the image as a result of too few photons reaching the image receptor to form the image. Quantum mottle is the term typically used when referring to noise on a film image.
119
Recorded detail
The distinctness or sharpness of the structural lines that make up the recorded image. This is the term that is used in film-screen imaging
120
Remnant radiation
When the attenuated x-ray beam leaves the patient, the remaining x-ray beam is composed of both transmitted and scattered radiation. Aka, exit radiation
121
Scale of contrast
The range of densities visible in a film image
122
Scattering
Some incoming photons are not absorbed but instead lose energy during interactions with atoms comprising tissue and are thrown off direction
123
Secondary electron
The ejected electron resulting from the Compton effect interaction. Aka: Compton electron
124
Short-scale contrast
A film radiograph with few densities but great differences among them is said to have high contrast
125
Size distortion
(Magnification) Refers to an increase in the image size of an object compared with its true, or actual, size
126
Spatial resolution
The smallest detail that can be detected in an image; the term typically used in digital imaging
127
Subject contrast
A result of the absorption characteristics of the anatomic tissue radiographed along with the quality of the x-ray beam
128
Tissue density
Matter per unit volume or the compactness of the anatomic particles comprising the anatomic part
129
Transmission
The incoming x-ray photon passes through the anatomic part without any interaction with the anatomic structures
130
The process whereby a radiographic image is created by variations in absorption and transmission of the exiting x-ray beam is known as:
Differential absorption
131
Which of the following processes occur during the x-ray beam interactions with tissue:
- -Absorption
- -Photon transmission
- -Scattering
All three
132
The ability of an x-ray photon to remove an atom's electron is a characteristic known as:
Ionization
133
the x-ray interaction responsible for absorption is:
Photoelectric interaction
134
The x-ray interaction responsible for scattering is:
Compton interaction
135
Remnant radiation is composed of which of the following:
- -Transmitted radiation
- -Absorbed radiation
- -Scattered radiation
1 and 3 only
136
What interaction creates unwanted exposure to the image, known as fog?
Compton interaction
137
Which of the following factors would affect beam attenuation?
- -Tissue atomic number
- -Beam quality
- -Fog
1 and 2 only
138
The low-optical density or high brightness areas on a radiographic image are created by:
Absorbed (attenuated) radiation
139
An anatomic part that transmits the incoming x-ray photon would create an area of ____ on the radiographic image.
High optical density or low brightness
140
The process of creating a radiographic image by differential absorption varies fro film-screen and digital imaging? (true or false)
False
141
An attribute (or attributes) of a radiographic image the affects the visibility of sharpness is:
Contrast and density
142
A radiographic film image with many densities but little differences among them is said to have:
Low contrast
143
What is defined as the range of exposure intensities an image receptor can accurately detect:
Dynamic range
144
which of the following would improved digital image quality?
- -Small matrix/large pixel size
- -Decreased pixel density/increased pixel pitch
- -Large matrix/large pixel size
- -Large matrix/increased pixel density
Large matrix and increased pixel density
145
When the percentage of light transmitted decreases on the image, the optical density does what?
Increases
146
Increasing the exposure intensity to the film-screen image receptor will do what to the optical density?
Increase it
147
What is the relationship between kV and transmission?
Transmission is when the x-ray photon passes through the body part without any interaction with tissue cells. When the kV is higher, the photon increases in penetrability and more of the photon is transmitted. It is a direct relationship.
148
List the factors that affect attenuation.
Tissue density
Tissue thickness
Atomic number of tissue
kVp selected
149
What is differential attenuation?
It is what permits an image to show the different body structures. Bone, with more density, attenuates more radiation where air allows more transmission. This gives increased and decreased brightness, respectively.
150
What are other terms for differential attenuation?
```
Differential absorption
Subject contrast (not the same as radiographic contrast)
Signal difference (digital term)
```
151
Why is filtration added to the tube?
So that patient dose can be minimized by eliminating the diagnostically unimportant, low-energy x-ray beams. 2.5 mm aluminum equivalent required for 70 kV and above.
152
Compare the size of the effective focal spot with the actual focal spot when the anode angle is less than 45 degrees.
Based on the line focus principle, when the anode is at an angle less than 45 degrees, the effective focal spot is always smaller than the actual focal spot.
153
What is the difference between exit radiation and transmitted radiation?
Transmitted radiation goes through the anatomic part without interacting with it. Exit radiation includes both this as well as scattered radiation.
154
What is attenuation and how does it affect film density?
Attenuation is where there is a reduction in # and/or energy of the primary x-ray beam as it interacts with anatomic tissue through absorption and scattering. Increased attenuation increases the brightness/decreases the density of an x-ray image.
155
Is radiographic contrast the same as subject contrast?
No
156
A PA chest x-ray would be an example of high or low contrast?
High contrast
157
An AP abdominal x-ray would be an example of high or low contrast?
Low contrast
158
Scatter noise is created on the image by:
Compton interaction
159
Does fog decrease sharpness?
No
160
As distance from the x-ray source increases, what happens to the tech's risk of exposure?
It decreases by the inverse square (1=1, 2=1/4, 3=1/9)
161
kVp determines what with current?
The speed of the photons in the tube current
162
As attenuation increases, what happens to radiographic density and brightness?
Radiographic density decreases and brightness increases.
163
Two more names for quantity of x-rays
Exposure or intensity
164
Describe reciprocity
The beam intensity is controlled by the product of mA x s.
165
What is the difference between high subject contrast and low subject contrast?
When tissues attenuate with greater difference, you get high subject contrast - more black/white. When tissues attenuate similarly, you get low subject contrast - more shades of grey.
166
What is an analog image receptor?
Film
167
What are two types of digital image receptors?
CR (Computed Radiography)
| DR (Direct Digital Radiography)
168
Compare how analog images and digital images are displayed and stored
Analog images: displayed on a viewbox, stored in a physical archive.
Digital images displayed on a computer monitor, stored in a Photo Archive Communication System
169
Compare the effect of overexposure on a digital image with an analog image
With a digital image, the computer will correct the overexposure. With an analog image, there is no way to correct it. With either, you are subjecting the patient to a higher dose of radiation than is ALARA.
170
What kind of imaging does fluoroscopy provide? What does fluoroscopy demonstrate?
It is dynamic live imaging. It demonstrates the movements within the body, such as in vascular or digestive systems.
171
What is the image receptor unit used for fluoroscopy?
Image intensifier
172
What device is used to display fluoroscopy images?
A closed-circuit television monitor
173
How many rems of radiation is the max dose per year?
5 rems
174
How many rems of radiation is the max dose for the gestational period of a declared pregnant worker?
0.5 rems
175
What is the traditional unit for exposure?
Roentgens
176
What is the traditional and the SI unit for absorbed dose?
Traditional: RAD (radiation absorbed dose)
SI: Grey
177
What is the traditional unit and SI unit for equivalent or effective dose?
Traditional: REM (radiation equivalent man)
SI: Sv (Sievert)
178
What is the lifetime maximum dose of radiation?
age x 1 rem
179
According to the anode heel effect, the x-ray beam is more intense on the anode side of the tube compared to the cathode side. (True or False)
False.
It is more intense on the cathode side of the tube.
180
mAs affects only the quantity of x-rays produced; it has no effect on the quality of x-rays. (True or False)
True
181
An increase in kV will increase both beam quality and quantity. (True or False)
True
182
The negative electrode of the x-ray tube is the anode. (True or False)
False.
The negative electrode of the x-ray tube is the cathode.
183
Low energy photons travel slower than high energy photons. (True or False)
False
Both low- and high-energy photons travel at a constant velocity/speed.
184
If the anode angle is 17 degrees, the actual focal spot size will be smaller than the projected or effective focal spot. (True or False)
False
The effective/projected focal spot would be smaller than the actual focal spot size.
185
As kV increases, wavelength decreases and frequency increases. (True or False)
True
186
Intensity refers to the energy of the x-ray beam. (True or False)
False
Intensity refers to the quantity of x-rays in the beam. Quality refers to the energy of the x-ray beam.
187
Total required filtration reduces patient skin dose without any effect on radiographic images. (True or False)
True
188
When the radiographer presses the prep button, a kilovoltage is applied to both ends of the x-ray tube. (True or False)
False
When the prep button is pushed an electrical current goes to the filament of the tube. When the exposure button is pushed an electrical current goes to both the anode and cathode ends of the tube.
189
During fluoroscopy where is the x-ray tube typically positioned in relation to the patient?
Generally it is under the table/under the patient.
190
Compare the appearance on a fluoroscopy television monitor of anatomical structures with high attenuation properties to structures with low attenuation properties.
Anatomical structures with high attenuation will appear more radiographically dense (darker), while structures with low attenuation will appear brighter. This is the opposite of regular radiography.
191
```
When tissue thickness increases, what happens to:
Attenuation?
Transmission?
Exposure to IR?
Optical image density?
Image brightness?
```
```
Attenuation increases
Transmission decreases
Exposure to IR decreases
Image density decreases
Brightness increases
```
192
```
When tissue density increases, what happens to:
Attenuation?
Transmission?
Exposure to IR?
Optical image density?
Image brightness?
```
```
Attenuation increases
Transmission decreases
Exposure to IR decreases
Image density decreases
Brightness increases
```
193
```
When the effective atomic number of tissue increases, what happens to:
Attenuation?
Transmission?
Exposure to IR?
Optical image density?
Image brightness?
```
```
Attenuation increases
Transmission decreases
Exposure to IR decreases
Image density decreases
Brightness increases
```
194
```
When kVp increases, what happens to:
Attenuation?
Transmission?
Exposure to IR?
Optical image density?
Image brightness?
```
```
Attenuation decreases
Transmission increases
Exposure to IR increases
Image density increases
Brightness decreases
```
195
```
When tissue thickness decreases, what happens to:
Attenuation?
Transmission?
Exposure to IR?
Optical image density?
Image brightness?
```
```
Attenuation decreases
Transmission increases
Exposure to IR increases
Image density increases
Brightness decreases
```
196
```
When tissue density decreases, what happens to:
Attenuation?
Transmission?
Exposure to IR?
Optical image density?
Image brightness?
```
```
Attenuation decreases
Transmission increases
Exposure to IR increases
Image density increases
Brightness decreases
```
197
```
When the effective atomic number of tissue decreases, what happens to:
Attenuation?
Transmission?
Exposure to IR?
Optical image density?
Image brightness?
```
```
Attenuation decreases
Transmission increases
Exposure to IR increases
Image density increases
Brightness decreases
```
198
```
When kVp decreases, what happens to:
Attenuation?
Transmission?
Exposure to IR?
Optical image density?
Image brightness?
```
```
Attenuation increases
Transmission decreases
Exposure to IR decreases
Image density decreases
Brightness increases
```
199
```
What happens to the electrons inside the tube when this is increased?
mA
s
mAs
kVp
```
mA: Filament current is hotter resulting in more electrons in the space charge
s: Filament current runs longer resulting in more electrons in the tube
mAs: More electrons in tube current
kVp: Electrons increase speed in tube current (higher energy)
200
```
What happens to the x-ray beam (quality and intensity) when this factor is increased?
mA
s
mAs
kVp
```
mA: More intensity
s: More intensity
mAs: More intensity
kVp: Higher quality and intensity
