問題一覧
1
meaning as low as reasonably achievable
ALARA Principle
2
- controlling factor of x-ray quality
- Increasing this will also INCREASE the AMPLITUDE OF THE SPECTRUM.
mAs
3
____ & _____ supplied to the x-ray tube for formation of x-ray beam
Voltage and Current
4
where electrons are gathered
Filament
5
the process where electrons are ejected from filament to the anode
Thermionic Emission
6
this is called the area of target of what electrons hit
- area of the anode to which electrons hit
Focal Spot
7
produced as electrons interact with the target
X-rays
8
cloud of electrons, the one that makes it difficult for electrons
Space Charge
9
called when electrons have difficulty being emitted from the filament or when electrons have difficulty moving
Space Charge Effect
10
affect the spatial resolution of the radiographic image and heat produced in the anode, determined by filament size
Focal Spot Sizes
11
Used when better spatial resolution is required
Selected when 300 mA or less is used in the filament
size range from 0.1 to 1 mm
using this increases heat generated to a smaller area of the anode
Small focal spot
12
Used when larger parts are examined and when other techniques that produce high heat are required.
Selected when we use 400 mA and up in the filament
sizes range from 0.3 to 2 mm
Large Focal Spot
13
area on the anode that is EXPOSED TO ELECTRONS from the cathode side
Actual Focal Spot
14
Area projected to the patient
Size is controlled by the size of the actual focal spot.
Effective Focal Spot
15
Allows a large area for heating while maintaining a small focal spot.
The target is angled to a degree thus making the effective area of the target much smaller than the actual area of electron interaction.
When the target angle is made smaller, the effective focal spot size is also made smaller.
Line Focus Principle
16
Diagnostic x-ray tubes have target angles ranging from 5-20 degrees.
Advantage: improves spatial resolution and heat capacity.
results in an effective focal spot size much smaller than the actual focal spot size.
Line Focus Principle
17
An unfortunate consequence of using the line focus principle.
Radiation intensity on the cathode side of the x-ray beam is greater than that on the anode side
X-rays that constitute the useful beam emitted toward the anode side must traverse a greater thickness of the target material than that on the cathode side.
The smaller the anode angle, the larger the heel effect.
Anode Heel Effect
18
important in imaging anatomy with varying thickness.
The heel effect
19
useful part of the x-ray projected from the x-ray tube window and onto the patient
Primary Beam
20
imaginary line generated by the centermost part of the x-ray beam
Central Ray
21
- produced when some electrons bounce off the focal spot and then land on other areas of the target, it causes X-rays to be produced outside the focal spot.
- Can image patient tissue that was intended to be excluded by the collimators
- Undesirable because if extends the size of the focal spot which increases skin dose and reduce Image contrast
- X-ray tubes are designed so that the projectile electrons only interact with the target only at the focal spot
Off-focus Radiation
22
Measuring each energy of the useful beam
The number of x-rays emitted is plotted as a function of the energy of each individual x-ray
Data of the this is needed to understand how changes in kVp, mA and added filtration affects the image quality of an image.
The minimum wavelength of x-ray emission corresponds to the maximum x-ray energy, and the maximum x-ray energy is numerically equal to the kVp.
X-ray Emission Spectrum
23
The area below the amplitude is the _____ of x-ray photons measured.
The area going to the right is the _____ of the x-ray photons.
1. Quantity 2. Energy
24
Characteristic X-ray Spectrum.
Contains only specific values.
Discrete Spectrum
25
have precisely fixed energies.
Characteristic X-rays
26
Bremsstrahlung X-ray Spectrum.
A spectrum that contains all possible values.
If an energy peaks at 90 keV, the spectrum would show all values ranging from 0 to 90 keV.
Continuous Spectrum
27
When ___ is increased, the distribution of the emitted x-ray energy SHIFTS MORE TO THE RIGHT; to a HIGHER AVERAGE ENERGY.
kVp
28
kVp affects both the ____ and ____ of x-rays as to why it also affects both the amplitude and the position of the spectrum
Quality and Quantity
29
Increase in ______ will result in an INCREASE in the PRODUCTION of BREMSSTRAHLUNG X-RAYS and high-energy x-rays increases in number to a greater extent than lower energy x-rays
Atomic Number
30
- will absorb low energy x-rays than high energy x-rays; therefore the spectrum is reduced more on the left than on the right
- reduces contrast due to beam hardening caused by increased in high energy x-rays.
Filtration
31
Using power sources with less voltage ripple will result in a ____ increase in x-rays when using the same kVp
12%
32
- mainly controlled by mAs
- The quantity or number of x-rays in the x-ray beam.
- Measured in Roentgen or Gray.
- Also called Radiation Exposure.
X-ray Intensity
33
- affects the image optical density.
- PROPORTIONAL to the SQUARE OF RATIO of the kVp.
X-ray Quantity
34
is directly proportional to the mAs.
X-ray Quantity
35
Increasing ___ will INCREASE the NUMBER OF ELECTRONS striking the target, therefore doubling the x-rays emitted
mAs
36
If the kVp is doubled, x-ray intensity would ____ by a factor of 4.
increase
37
As the distance increases, x-ray intensity _____ by a factor of 4.
decreases
38
varies INVERSELY with the SQUARE OF DISTANCE from the x-ray tube target
X-ray Intensity
39
- Reduces low energy x-rays which contribute nothing in image production
- lowers patient dose
- will reduce beam intensity while increasing the average energy
Filtration
40
Ability of x-rays to penetrate deeper in tissue.
High energy x-rays penetrate deeper than low energy x-rays.
As the x-ray energy is increased, beam penetrability is also increased.
Factors affecting the x-ray quality also influences radiographic contrast.
Beam Penetrability
41
The thickness of the absorbing material necessary to reduce the x-ray intensity to half its original value.
It is the best method for specifying x-ray quality.
Half Value Layer
42
As the _____ increases, x-ray beam penetrability also increases, therefore HVL is also _________
1. kVp 2. Increased
43
- material of choice in filtration
efficient in removing low-energy x-rays through photoelectric effect and because it is readily available, inexpensive, and easily shaped
Aluminum
44
- Primary purpose is to remove low energy x-rays that have little chance of getting to the image receptor
- Secondary purpose is to reduce patient dose
Increasing this increases x-ray beam quality
Filtration
45
Located inside the x-ray tube
Glass or Metal enclosure of the x-ray tube
Usually made with Pyrex glass
Equivalent to 0.5 mm Al (General Radiography)
Equivalent to 0.1 mm Al (Beryllium material for Mammography)
Inherent Filtration
46
Thin sheet of Aluminum placed between the x-ray tube and collimator
Usually has two sources
1-2 mm Al: Permanently installed between the housing and the collimator
1 mm Al: Silver Surface of the mirror in the collimator
Added Filtration
47
Used when a body part with unequal thickness or tissue composition needs to be examined and produce an image with uniform intensity.
Compensating Filters
48
obtained as the voltage across the x-ray tube increases from zero to its peak value, x-ray intensity and energy increase SLOWLY at first, then RAPIDLY
Peak Voltage
49
Size of the Effective Focal Spot is controlled by?
Actual Focal Spot
50
Radiation intensity across the useful beam of an x-ray field can vary by as much as what percent
45%
51
must be positioned on the thicker part of the anatomy to provide a more uniform radiation exposure to the image receptor
Cathode side
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1
meaning as low as reasonably achievable
ALARA Principle
2
- controlling factor of x-ray quality
- Increasing this will also INCREASE the AMPLITUDE OF THE SPECTRUM.
mAs
3
____ & _____ supplied to the x-ray tube for formation of x-ray beam
Voltage and Current
4
where electrons are gathered
Filament
5
the process where electrons are ejected from filament to the anode
Thermionic Emission
6
this is called the area of target of what electrons hit
- area of the anode to which electrons hit
Focal Spot
7
produced as electrons interact with the target
X-rays
8
cloud of electrons, the one that makes it difficult for electrons
Space Charge
9
called when electrons have difficulty being emitted from the filament or when electrons have difficulty moving
Space Charge Effect
10
affect the spatial resolution of the radiographic image and heat produced in the anode, determined by filament size
Focal Spot Sizes
11
Used when better spatial resolution is required
Selected when 300 mA or less is used in the filament
size range from 0.1 to 1 mm
using this increases heat generated to a smaller area of the anode
Small focal spot
12
Used when larger parts are examined and when other techniques that produce high heat are required.
Selected when we use 400 mA and up in the filament
sizes range from 0.3 to 2 mm
Large Focal Spot
13
area on the anode that is EXPOSED TO ELECTRONS from the cathode side
Actual Focal Spot
14
Area projected to the patient
Size is controlled by the size of the actual focal spot.
Effective Focal Spot
15
Allows a large area for heating while maintaining a small focal spot.
The target is angled to a degree thus making the effective area of the target much smaller than the actual area of electron interaction.
When the target angle is made smaller, the effective focal spot size is also made smaller.
Line Focus Principle
16
Diagnostic x-ray tubes have target angles ranging from 5-20 degrees.
Advantage: improves spatial resolution and heat capacity.
results in an effective focal spot size much smaller than the actual focal spot size.
Line Focus Principle
17
An unfortunate consequence of using the line focus principle.
Radiation intensity on the cathode side of the x-ray beam is greater than that on the anode side
X-rays that constitute the useful beam emitted toward the anode side must traverse a greater thickness of the target material than that on the cathode side.
The smaller the anode angle, the larger the heel effect.
Anode Heel Effect
18
important in imaging anatomy with varying thickness.
The heel effect
19
useful part of the x-ray projected from the x-ray tube window and onto the patient
Primary Beam
20
imaginary line generated by the centermost part of the x-ray beam
Central Ray
21
- produced when some electrons bounce off the focal spot and then land on other areas of the target, it causes X-rays to be produced outside the focal spot.
- Can image patient tissue that was intended to be excluded by the collimators
- Undesirable because if extends the size of the focal spot which increases skin dose and reduce Image contrast
- X-ray tubes are designed so that the projectile electrons only interact with the target only at the focal spot
Off-focus Radiation
22
Measuring each energy of the useful beam
The number of x-rays emitted is plotted as a function of the energy of each individual x-ray
Data of the this is needed to understand how changes in kVp, mA and added filtration affects the image quality of an image.
The minimum wavelength of x-ray emission corresponds to the maximum x-ray energy, and the maximum x-ray energy is numerically equal to the kVp.
X-ray Emission Spectrum
23
The area below the amplitude is the _____ of x-ray photons measured.
The area going to the right is the _____ of the x-ray photons.
1. Quantity 2. Energy
24
Characteristic X-ray Spectrum.
Contains only specific values.
Discrete Spectrum
25
have precisely fixed energies.
Characteristic X-rays
26
Bremsstrahlung X-ray Spectrum.
A spectrum that contains all possible values.
If an energy peaks at 90 keV, the spectrum would show all values ranging from 0 to 90 keV.
Continuous Spectrum
27
When ___ is increased, the distribution of the emitted x-ray energy SHIFTS MORE TO THE RIGHT; to a HIGHER AVERAGE ENERGY.
kVp
28
kVp affects both the ____ and ____ of x-rays as to why it also affects both the amplitude and the position of the spectrum
Quality and Quantity
29
Increase in ______ will result in an INCREASE in the PRODUCTION of BREMSSTRAHLUNG X-RAYS and high-energy x-rays increases in number to a greater extent than lower energy x-rays
Atomic Number
30
- will absorb low energy x-rays than high energy x-rays; therefore the spectrum is reduced more on the left than on the right
- reduces contrast due to beam hardening caused by increased in high energy x-rays.
Filtration
31
Using power sources with less voltage ripple will result in a ____ increase in x-rays when using the same kVp
12%
32
- mainly controlled by mAs
- The quantity or number of x-rays in the x-ray beam.
- Measured in Roentgen or Gray.
- Also called Radiation Exposure.
X-ray Intensity
33
- affects the image optical density.
- PROPORTIONAL to the SQUARE OF RATIO of the kVp.
X-ray Quantity
34
is directly proportional to the mAs.
X-ray Quantity
35
Increasing ___ will INCREASE the NUMBER OF ELECTRONS striking the target, therefore doubling the x-rays emitted
mAs
36
If the kVp is doubled, x-ray intensity would ____ by a factor of 4.
increase
37
As the distance increases, x-ray intensity _____ by a factor of 4.
decreases
38
varies INVERSELY with the SQUARE OF DISTANCE from the x-ray tube target
X-ray Intensity
39
- Reduces low energy x-rays which contribute nothing in image production
- lowers patient dose
- will reduce beam intensity while increasing the average energy
Filtration
40
Ability of x-rays to penetrate deeper in tissue.
High energy x-rays penetrate deeper than low energy x-rays.
As the x-ray energy is increased, beam penetrability is also increased.
Factors affecting the x-ray quality also influences radiographic contrast.
Beam Penetrability
41
The thickness of the absorbing material necessary to reduce the x-ray intensity to half its original value.
It is the best method for specifying x-ray quality.
Half Value Layer
42
As the _____ increases, x-ray beam penetrability also increases, therefore HVL is also _________
1. kVp 2. Increased
43
- material of choice in filtration
efficient in removing low-energy x-rays through photoelectric effect and because it is readily available, inexpensive, and easily shaped
Aluminum
44
- Primary purpose is to remove low energy x-rays that have little chance of getting to the image receptor
- Secondary purpose is to reduce patient dose
Increasing this increases x-ray beam quality
Filtration
45
Located inside the x-ray tube
Glass or Metal enclosure of the x-ray tube
Usually made with Pyrex glass
Equivalent to 0.5 mm Al (General Radiography)
Equivalent to 0.1 mm Al (Beryllium material for Mammography)
Inherent Filtration
46
Thin sheet of Aluminum placed between the x-ray tube and collimator
Usually has two sources
1-2 mm Al: Permanently installed between the housing and the collimator
1 mm Al: Silver Surface of the mirror in the collimator
Added Filtration
47
Used when a body part with unequal thickness or tissue composition needs to be examined and produce an image with uniform intensity.
Compensating Filters
48
obtained as the voltage across the x-ray tube increases from zero to its peak value, x-ray intensity and energy increase SLOWLY at first, then RAPIDLY
Peak Voltage
49
Size of the Effective Focal Spot is controlled by?
Actual Focal Spot
50
Radiation intensity across the useful beam of an x-ray field can vary by as much as what percent
45%
51
must be positioned on the thicker part of the anatomy to provide a more uniform radiation exposure to the image receptor
Cathode side