Ch. 6 Flashcards
The product of milliamperage and exposure time is _______ to the quantity of x-rays produced.
directly proportional
As mAs increases, the quantity of radiation reaching the IR
Increases
If you were to select 250 mA and 0.5s on the control panel, how much mAs would be created?
125 mAs
mA x time = mAs
The original exposure to the IR is 100mA at 125ms. Which of the following exposure techniques would decrease the IR exposure by about 1/2?
200 mA at 31ms
100 mA at 0.063.s
50 mA at 0.125 s
All the above
All the above
The original technique is 300 mA at 50ms. If the mA is increased to 500, what exposure time will maintain the same exposure to the IR?
0.030 s
0.30 s
3 ms
15 ms
0.030 s
The original technique is 50mA at 0.20s. Which of the following exposure techniques will maintain the same exposure to the IR?
100 mA at 0.10 s and 200 mA at 0.05 s
100 mA at 0.10 s and 400 mA at 25 ms
200 mA at 0.05 s and 400 mA at 25 m
All are correct
All are correct
Which of the following is correct regarding the effect mAs has on the displayed digital image?
A. Increases brightness.
B. Decreases brightness.
C. Does not control brightness.
D. Increases contrast
Does not control brightness
Increased quantum noise is seen in a digital image with:
severely lower-than-needed mAs
If the exposure indicator value indicates too little radiation reaching the IR and the image displays increased quantum noise, what technique change would be best?
increase kVp by 15% and double mAs
The numerical value that is displayed on the processed image to indicate the level of x-ray exposure received on the digital image receptor is the
Exposure indicator
Which of the following technical factors affects the exposure to the IR by altering the amount and penetrating ability of the x-ray beam?
a. kVp
b. mA
c. Seconds
d. SID
kVp
In order to reduce patient exposure, what exposure factors should be considered?
higher kVp, lower mAs
A high kVp results in:
A less variation in the x-ray intensities exiting the patient.
B decrease interactions from Compton scattering.
C high-contrast image.
A) less variation in the x-ray intensities exiting the patient.
How much change in kVp will change the radiation exposure to the IR by a factor of 2?
15%
The 15% rule states that increasing or decreasing the kVp by 15% has the same effect as doubling or halving the mAs
The original technique is 80kVp at 20 mAs. If the kVp is increased to 92, what change in mAs will maintain the exposure to the IR?
10 mAs
A 15% increase in kVp, requires ½ the mAs to maintain a similar exposure to the IR.
The original technique is 80 kVp at 20 mAs. If the kVp is decreased to 68, what change in mAs will maintain the exposure to the IR?
40 mAs
Double your mAs
During the selection of the focal spot size, the radiographer is really determining the:
Actual size of the filament used
The distance between the radiation source and the image receptor is the:
SID
The relationship between distance and x-ray beam intensity, specifically that the intensity of the x-ray beam is inversely proportional to the square of the distance from the source, is the:
Inverse square law
If a person stands 3 feet from the source of exposure, receives an exposure of 160 mR, and then moves to 6 feet from the source of exposure, what would be the new exposure according to the ISL?
40 mR
If a person stands 12 feet from the source of exposure, receives an exposure of 60 mR, and then moves to 3 feet from the source of exposure, what would be the new exposure according to the ISL?
960 mR
According to the inverse square law, decreasing the distance from the x-ray source from 12 to 3 feet (factor of four) will result in an increase of exposure from 60 to 960 mR.
The distance between the object being imaged and the IR is the:
OID
When the SID is divided by the SOD, what is the result called?
Magnification Factor
If the first image of a chest is done using 72 in and 12 mAs, and a second image is done using 40 in, how much mAs should be used to maintain exposure to the IR?
4 mAs
A quality radiographic image is done using 10 mAs, 70 kVp, and a 12:1 ratio grid. How much mAs is needed to produce an image with the same exposure to the IR when the grid is removed?
2 mAs
The original technique is 80 kVp at 20 mAs using an 8:1 grid ratio. What change is mAs is needed if changing to a 16:1 grid ratio?
30 mAs
The misrepresentation of the size of an object is:
Magnification
In order to image a structure that is located anteriorly in the body, it is best radiographed to minimize magnification by doing a(n) _______ projection
posterior-anterior (PA)
Magnification is affected by:
SID
If the image size measures 4.6 in, and the magnification factor is 1.42, what is the size of the object?
3.24 in
image size divided by magnification factor
SID OVER SOD
Shape distortion can be created by:
decreasing SOD angling the central ray
The SOD can be determined by:
subtracting the OID from SID
What effect will increasing SID have on spatial resolution?
increasing spatial resolution
For every ______ of part thickness, the radiographer should adjust the mAs by a factor of two.
4-5 cm
If the first radiograph of a foot is done using 4 mAs at 40 in, and a second radiograph is done using 50 in, how much mAs should be used to maintain exposure to the IR?
6 mAs
(New SID)² = 50²
(Old SID)² = 40²
New mAs = (50²/40²) * 4 mAs = 6.4 mAs
Assuming all produce appropriate diagnostic images, which of the following would be the best exposure technique choice when performing a chest radiograph on an infant?
A. Use 40 ms exposure time.
B. Use 60 ms exposure time.
C. Use 200 ms exposure time.
D. Use at least 80 kVp.
A. Use 40 ms exposure time.
Shortest possible exposure time
With all other factors remaining the same, a patient with which body habitus would require the highest exposure factors?
hypersthenic
The property of the x-ray beam that impacts the unsharpness on the image is the beam:
divergence
Once the part has been penetrated, a doubling of the mAs results in _______ the exposure to the IR.
two times
Which of the following mA and exposure time combinations does not produce 12 mAs?
A. 200 mA at 0.06 s
B. 400 mA at 0.03 s
C. 600 mA at 20 ms
D. 800 mA at 0.15 s
D. 800 mA at 0.15 s
mA x time
800 mA at 0.15 s results in 120 mAs
If lower than needed kVp is selected, the digital image will have:
higher subject contrast and increased quantum noise
Using twice as much mAs as needed will result in
adequate image brightness and unnecessary patient radiation exposure
Knowing that 6 mAs is appropriate for a knee examination done at 40 in SID, how much mAs should be used at 56 in SID?
12 mS
Which of the following is not affected by a change in SID?
A. Spatial resolution
B. Image contrast
C. Amount of radiation reaching the IR
D. Magnification
Image contrast
The radiographic grid is located
between the patient and the IR
Decreasing collimation results in:
A. increased fog and lower image contrast
B. increased fog and increased patient exposure
C. lower image contrast and increased patient exposure
D. all options are correct
ALL
Decreasing collimation results in
increased fog, lower image contrast, increased patient exposure
Increasing tube filtration results in an x-ray beam with:
fewer photons and higher energy
As compared to a patient with a 24 cm thick abdomen, imaging a patient with a 20 cm thick abdomen will result in:
A. less scatter and increased spatial resolution
B. less scatter and higher contrast
C. increased spatial resolution and higher contrast
D. all options are correct
D. all options are correct
Increasing part thickness decreases image contrast:
true or false?
True
Kilovoltage does not affect the quantity of exit radiation until adequate penetration is reached
T or F
True
The amount of mAs used controls image brightness
T or F
False
mAs does not control brightness!
Changes in kVp do not affect the exposure indicator value
T or F
False
Any increase in magnification results in a decrease in spatial resolution
T or F
True
When choosing a grid for an examination, the grid with the highest grid ratio should always be selected in order to most improve image contrast.
T or F
False
As compared to a three-phase x-ray unit, a single-phase unit requires higher exposure techniques to produce a comparable image.
T or F
True
The same mAs and kVp should be used for an AP lumbar spine and a lateral lumbar spine.
T or F
False
To reduce patient radiation exposure, is it best to use a lower kVp and higher mAs.
False
You want to use high kVp and low mAs!
OID affects magnification, spatial resolution, contrast, and exposure to the IR.
True
KNOW GRID CONVERSIONS
no grid, conversion?
1
5:1 grid conversion?
2
6:1 gird conversion is?
3
8:1 grid conversion?
4
12:1 grid conversion?
5
16:1 grid conversion?
6
