The amount of filtration required to reduce the exposure of the beam to half of its original intensity is defined as:
What is filtration's relationship with density?
Setting identical exposure factors, which type of x-ray unit will produce the greatest heat?
What causes the anode heel effect to occur?
The angle of the target
Total filtration in the x-ray beam includes:
B and C
Which element is added filtration usually made of?
Which of the following constitute inherent filtration? Choose all that apply
Select one or more:
Oil surrounding the tube
Mirror inside the collimator
Due to the anode heel effect, the differences in intensities between the ends of the x-ray field can be as much as:
The amount the voltage varies during an x-ray exposure is known as:
____________ will extend x-ray tube life.
Warming up the tube after 2 hours of nonuse
An exposure of 100 kVp, 800 mA, and 0.1 seconds is a safe expsoure.
What is the MAIN purpose of filtration?
Decrease patient dose
Which of the following types of filtration produce a more uniform exposure to the image receptor?
What is the most common type of generator used today?
Effective compensation for the anode heel effect would involve positioning:
the thinnest portion of the part under the anode
Why are instantaneous load tube rating charts used?
An instantaneous load tube rating chart is used to determine whether a particular exposure would be safe to make and to determine what limits on kVp, mA, and exposure time must be made to make a safe exposure. (p.37)
X-ray tubes operating above 70 kVp must have total filtration of at least _________ of aluminum, or its equivalent.
Which of the following practices will extend the life of the x-ray tube?
1. Use low mA and longer exposure time.
2. Warm up the tube as appropriate.
3. Hold down the rotor button for a long time, to keep the tube warmed up.
1 & 2 only
Low energy photons are desirable in the x-ray beam because they contribute to image quality.
How many heat units (in HU) will result from an exposure made on a single phase x-ray unit using 400 mA, 0.2 seconds, and 70 kVp?
What is the formula for heat units?
mA x exposure time x kVp x generator factor
An exposure of 80 kVp, 1000 mA, and 0.01 seconds is a safe expsoure.
What is filtration's relationship with contrast?
The intensity of the x-ray beam is greater on the
The differences in intensities on the anode and cathode sides can be as much as?
Define "half-value layer"
"Half-value layer" is the amount of filtration that reduces the intensity of the beam to one-half its original value.
Filtration of the x-ray beam results in:
Increased beam quality
As collimation decreases, exposure to the IR increases.
Significant collimation requires an increase of _____________ of the mAs.
30 to 50%
What effect does increasing the kVp have on scatter radiation?
Technologist should always be aware of limiting the x-ray field size for which 2 reasons?
Select one or more:
What occurs when scatter radiation strikes the film?
Radiographic contrast decreases.
What effect does body part size have on scatter radiation?
The thicker the part, the more scatter
Which of the following beam restricting devices is best at limiting unsharpness surrounding the radiographic image?
The purpose of the mirror inside the collimator is to:
Project a light field onto the patient
What shape is the unrestricted x-ray beam?
As collimation decreases, density:
A beam restricting device that has 2 or 3 sets of lead shutters is a(n):
Decreasing collimation results in:
A larger field size
When using a digital flat-panel detector:
The radiographer must adjust the collimator to the area of interest.
What is the MAIN purpose for automatic collimators?
reduce patient exposure
BRIEFLY explain 2 general problems with the collimator light.
The two general problems with a collimator light is that the light can go out and the light field can be misaligned depending on the angle of the mirror.
Which exposure factor should you change to compensate for increasing collimation?
An aperture diaphragm with an attached elongated tube is a(n):
Increasing collimation results in reduced patient exposure, increased field size, and reduced scatter production.
The smaller the volume of tissue irradiated, the:
Less the amount of scatter produced
As collimation increases, contrast:
Name 3 types of beam restriction devices.
Three types of beam restricting devices are: aperture diaphragms, cones and cylinders, and collimators.
Which beam restriction device can be cut to the size needed?
An aperture diaphragm
What effect does increasing collimation have on patient dose?
What does PBL stand for?
positive beam limitation
What is the best type of beam restriction device?
What purpose does positive beam limitation serve?
To reduce patient exposure by limiting the exposure field to the same size as the image receptor in the Bucky tray
What is another name for PBL?
Why is scatter radiation bad?
Decreases image quality
Which of the following 2 factors would you use to help determine if you will use a grid for a particular exam?
>60 kVp and >10 cm thick body part
In a grid, what are the 2 types of orientation of the lead lines in relationship to one another? (Choose all that apply)
Select one or more:
What is focal range and why does it matter?
Focal range is the recommended SID range that the beam should be from a focused grid. Focused grids are made with specific angles that can absorb and restrict the beam if placed at the wrong distance. This may make the image undiagnostic.
A grid whose lead strips run perpendicular to the long axis of the grid is called a(n):
Short dimension grid
The recommended SIDs that can be used with a focused grid describes the:
Which of the following statements is true?
As grid ratio increases, the removal of scatter increases.
What is the most common type of grid cutoff error?
Why is Aluminum used at interspace material in grids?
Aluminum is used because it is strong enough to support the grid but is also easily penetrated by photons.
Grid frequencies can range from:
25 to 80 lines per centimeter
An adult's knee measuring 14 cm should be done without a grid.
Increasing grid ratio has what effect on density?
Who invented radiographic grids?
What is the MOST effective means for limiting scatter that hits the IR?
Patient dose increases when:
1. Changing from a higher to a lower grid ratio
2. Changing from a lower to a higher grid ratio
3. A grid is used
2 & 3 only
If you have a good technique at 5 mAs with a 5:1 grid, what technique would you need to use when switching to a 16:1 grid? (Units in mAs)
Which grid design is manufactured to match the divergence of the x-ray beam?
The focused grid
What occurs when the x-ray beam is not properly aligned with the grid strips?
Briefly expain why scatter radation is bad.
Scatter adds unwanted density without adding to patient information. Scatter ruins image quality.
Increasing grid ratio has what effect on contrast?
The only type of grid cutoff that occurs with both focused and parallel grids is due to:
Which type of grid pattern is the MOST popular?
If you have a good technique at 10 mAs without a grid, what mAs would you need to use when switching to a 6:1 grid? (Units in mAs)
What is the focal range for a parallel grid?
parallel grids have no focal range
Explain how the air gap technique works in terms of scatter radiation.
When OID is increased, scatter from the patient is less likely to reach the IR. The greater the gap, the greater the reduction on scatter reaching the IR. The smaller the gap, the greater chance scatter has to reach the IR to contaminate the image. mAs needs to be manipulated depending on OID to retain image density.
Grids that move during the exposure:
A and C
Due to increased potential grid cutoff, which would be the most challenging grid to use?
Which of the following is not a way to reduce the production of scatter radiation?
Increase the grid ratio.
Changing from an 8:1 grid to a 12:1 grid, along with making the appropriate adjustments, will result in:
1. Increased patient dose
2. An image with increased contrast
3. Using more mAs
1, 2, & 3
If the height of the grid strip is 16 mm, the distance between the strips is 2 mm, and the strip is 0.3 mm thick, what is the grid ratio?
What type of grid error results in appropriate exposure to the middle of the IR and marked underexposure along the sides of the IR?
Upside-down focused grid
What is grid ratio?
ratio of the height of the lead strips to the distance between them
Off-focus grid cutoff only occurs when the SID exceeds the focal range.
What is grid frequency?
number of lead lines per unit of length
What is the grid conversion factor for a 12:1 ratio grid?
An optimal AP abdomen radiograph can be produced using 40 mAs, 75 kVp, and a 12:1 grid. How much mAs would be needed if the only grid available is a 6:1 ratio grid? (Units in mAs)
Which of the following influences the amount of scatter radiation striking the image receptor but not the production of scatter radiation?
Increase the grid ratio.
Which type of grid cutoff error is shown in this image?
Which type of grid error is shown in this radiograph?
If an excellent knee radiograph is produced using 10 mAs and an 8:1 ratio grid, how much mAs will be needed if no grid is available?
Which of the following statements is true?
If the height of the lead strips increases and the space between the grid strips decreases, the grid will be more effective at scatter removal.
Oil around tube
Inherent filtration + Added filtration
The amount of filtration that reduces the intensity of the beam to 1/2 its original value.
Indirect measure of total filtration.
Hardening the beam
What are the three types of generators?
Single-phase (voltage ripple = 100%)
Three-phase ( 6 phase = 13%, 12 phase = 4%)
High frequency (<1%)
Process whereby the average energy of a heterogeneous radiation beam in increased by passing it through an absorber.
What are the two purposes of beam restriction?
limit patient exposure
What are 2 problems with the collimator light?
light goes out
light field (mirror) is misaligned
When were grids invented?
The number of lead lines per unit of length.
Range = 25 to 45 lines/cm, or 60 to 110 lines/inch.
The ratio of the height of the lead strips over the distance between them.
GR = h/D.
Grid ratio ranges:
Linear (lead lines run in one direction, most popular, allows tube angulation)
Crossed (crossed-hatched, lead lines run in 2 directions, removes more scatter, doesn't allow angulation)
Refers to the orientation of the lead lines to one another.
Parallel or non-focused grid - mostly use in fluoro and mobile imaging.
Focused grid - allows more photons to hit IR.
Imaginary line drawn from each of the lead lines.
Points of convergence connected along the length of a linear focused grid.
distance between the grid and the convergent line or point.
recommended range of SIDs that can be used with a focused grid.
Focal range at 40" focal distance?
36" to 42"
Focal range at 72" focal distance?
66" to 74"
matches size of cassette, placed on top of IR, usually taped.
IR with a permanently built-in grid mounted to its surface.
Permanently mounted grid that allows an IR to slide in behind it.
A short dimension grid has lead strips running perpendicular to the long axis of the grid.
A long dimension grid has lead strips running parallel to the long axis of the grid.
a decrease in the number of transmitted photons that reach the image receptor because of some misalignment of the grid.