A radiographer that exhibits a long scale of contrast is one with what?
many shades of gray that have minimal differences
Which of the following will contribute to the production of a longer (low) scale of contrast?
-decrease in the grid ratio
-increase in kVp
-decrease in photon energy
increase in kVp
The available shades of gray in a digital imaging system is determined by the:
bit depth
Which of the following sets of exposure factors would produce the shortest (highest) scale of contrast?
-10 mAs, 70 kVp, 40 inch SID, 6 inch OID
-5 mAs, 90 kVp, 72 inch SID, 4 inch OID
-15 mAs, 80 kVp, 40 inch SID, 6 inch OID
-20 mAs, 100 kVp, 72 inch SID
10 mAs, 70 kVp, 40 inch SID, 6 inch OID
What is the primary function of contrast?
to make visible detail
If the field size is changed from an 8 X 10 to an 14 X 17 inch field size with no other changes in exposure factors, what would happen to contrast?
contrast would change to a longer scale of contrast
The reason contrast mediums result in a shorter scale of contrast in the body is:
the difference in atomic numbers between the contrast and tissue
What effect does increasing tube filtration have on the scale for contrast?
produces a longer scale of contrast
Increasing part thickness with compensation of exposure factors will:
increase Compton interactions and produce a longer scale of contrast
If a radiographic technique is originally 100 mA at 100 ms and then changed to 50 mA at 200 ms:
there will be no change in contrast
This is defined as the magnitude of the signal difference in the remnant beam as a result of the different absorption characteristics of the tissues and structures making up that part?
subject contrast
A term used to describe the mathematical formula used by the computer to reconstruct the image is referred to as:
algorithms
Which fo the following pixel bit depths would display a greater range of shades of gray to present anatomic tissues?
-10 bit
-12 bit
-14 bit
-16 bit
16 bit
If a radiographic technique designed for an 8:1 grid is changed to accommodate a 12:1 grid:
contrast will change to a shorter time
A 15% decrease in kVp accompanied by a 50% increase in mAs will result in a(an):
higher (shorter) scale of contrast
Which of the following would affect the production of scattered radiation?
-field size/collimation
-part thickness
-grids
-kVp
-field size/collimation
-grids
-kVp
Which of the following is (are) associated with subject contrast?
-tissue density
-kilovoltage (kVp)
-patient thickness
all 3 of them
Subject contrast varies by:
-tissue density
-tissue thickness
-atomic number
all 3
Decreasing part thickness with compensation of exposure factors will:
Decrease Compton interactions & produce a shorter scale of contrast
A 15% increase in kVp accompanied by a 50% decrease in mAs will result in a(n):
Longer (low) scale of contrast
A decrease from 90 to 77 kVp will result in:
shorter (high) scale of contrast
Radiographic contrast is the result of:
differential absorption
The reason contrast medias produce higher contrast (shorter scale) in the body is:
difference in atomic numbers between the contrast and tissue
Which combination will result in the most scattered radiation reaching the image receptor?
Using the same mAs and higher kVp
In which of the following ways can a shorter (high) scale of contrast be obtained?
by using a contrast medium
If the field size is changed from an 14x17 to a 8x10 inch field size, which statement about contrast is correct?
contrast would change to a shorter scale
If a radiographic technique designed for a 8:1 grid is changed to accommodate an 5:1 grid:
contrast would change to a long (low) scale of contrast
Remnant xrays are those that:
exit the patient and expose the image receptor
Beam limitation devices are used to help:
control the production of scattered radiation
This is defined as the visible difference between any two areas of brightness levels within the radiographic image:
contrast
The air-gap technique produces a shorter scale of contrast because:
the increased OID results in scattered radiation missing the IR
This is the magnitude of signal difference in the remnant beam due to various tissue characteristics:
subject contrast
As the amount of filtration is increased from 2.0 mm Al to 2.5 mm Al:
contrast would change to a lower contrast
Produced on an image when there is insufficient radiation hitting the image receptor
Quantum noise/mottle
Help to reduce the amount of scattered radiation reaching the IR
grids
As a general rule, grids are appropriate for anatomy ______ cm thick or more.
10 cm
What is the function of filtration?
remove low energy, long wavelength radiation
What type of bone is easier to penetrate?
Demineralized bone or healthy bone?
Demineralized bone, because it has less calcium and produces a longer/low scale of contrast. Healthy bone demonstrates a shorter/higher scale of contrast.
The use of contrast media increases contrast due to what in the body?
Photoelectric interaction