Contrast (quiz questions)
Q: Which kVp setting will provide the most kinetic energy to filament electrons?
100
Q: A ______% increase in kVp has the same effect on optical density as doubling the mAs.
15
Q: At least a _______% change in mAs is necessary to produce a visible change in optical density.
30
Q: Which kVp is capable of producing the lowest contrast?
80; higher kVp = lower contrast
Q: A radiograph taken using 65@ 10 is too light. Which technique would double the optical density while producing a wider scale of contrast? A. 75@10 B. 75@20 C. 55@20 D. 55@40
A. 75@10; mAs stays the same; increase kVp = wider scale
Q: Collimation acts to reduce scatter and its resultant image fog primarily by which of the following? A. Reducing beam energy B. limiting area of exposure C. increasing number of photons D. does not affect image fog
B
Q: A radiograph is taken using 75@ 20. Which change in technique would increase contrast but maintain the same density? A. 85@10 B. 85@ 40 C. 65@20 D. 65@40
D
Q: An abdomen image is done using 66 kVp and 40 mAs. Image density is appropriate but the image has too high (short scale) contrast. Which of these exposure factors would be the best to change to make? A. 56 and 60 B. 66 and 20 C. 76 and 40 D. 76 and 20
D. 76 kVp and 20 mAs increase kVp by 15% and decrease mAs by 1/2
Q: Which technique would give the highest patient does? A. 90/200 mA @ .02 sec 4 mAs B. 87/400 mA @ .02 sec 8 mAs C. 74/400 mA @ .04 sec 16 mAs D. 65/300 mA @ .1 sec 30 mAs
D; highest mAs = highest patient dose
Q: why is scatter radiation exposure undesirable?
Decreases contrast
Q: A positive contrast media will have what effect on radiographic contrast?
Increase
Q: __________ is defined as the ability to image two separate objects and visually detect one from the other.
Resolution
Q: If mAs is increased from 20 mAs to 40 mAs, the patient dose will ________.
be doubled
Q: Patient thickness should be measured with the ______.
caliper
Q: The use of _______ improves contrast and reduces patient dose.
collimation
Q: Which medical condition requires a lower technique?
emphysema
Q: Scatter radiation increases as ______ increases
field size
Q: An image with low contrast appears
gray
Q: A radiograph with few densities but great differences among them is
high contrast short scale
Q: Compton scatter contributes to
image noise
Q: Reducing the area of exposure (increasing collimation) ________ image contrast.
increases
Q: Lowering kVp _______ patient dose and _______ image contrast.
increases, increases
Q: Added filtration has the effect of _______ beam quality and ________ patient dose.
increasing, reducing
Q: Beam penetrability is increased if ______ is increased.
kVp
Q: Beam penetrability is increased if _______ is increased.
kVp
Q: Technologist primarily controls radiographic contrast by varying the _______
kVp
Q: What is the primary controller of image contrast?
kVp
Q: Beam quality is improved when the _____ is increased, but _______ has no effect on beam quality.
kVp, mA
Q: What are the four primary exposure factors?
kVp, mAs, time and SID
Q: Photoelectric interactions increase when ______ is decreased.
kVp; photoelectric interaction = absorption cause scatter
Q: What is X-ray absorbing material in grids?
lead
Q: There is a direct relationship between the quantity of x-rays and the __________.
mA
Q: Optical density is primarily controlled by changing the _____
mAs
Q: When only the optical density needs to be changed, only the ______ should be adjusted.
mAs
Q: And increase in mAs causes _______ in beam quality and ________ in beam quantity.
no change, and increase
Q: With automatic exposure control the exposure is terminated when the optimum ______ is reached.
optical density
Q: Decreasing the kVp will increase
patient dose
Q: Image forming x rays include those which have been
scattered through Compton interaction and absorbed through photoelectric interaction
Q: The x-rays that are transmitted through the patient without interaction contribute to _____ __________.
useful information
Q: The most commonly used beam restricting device is the __________.
variable collimator
