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Radiographic Physics
Physics 11-2, X-ray Quality and Half-Value Layer
31
Medical
Not Applicable
10/27/2005

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Term
Which of the following is the most appropriate measure of x-ray beam quality?
Definition
HVL
Term
HVL definition
Definition
That thickness of an absorber that will reduce the x-ray intensity to one half its original value.
Term
The quality of an x-ray beam is principally a function of which of the following?
Definition
kVp
Term
The HVL is affected principally by a change in which of the following?
Definition
kVp
Term
When filtration is added to an x-ray tube, which of the following increases?
Definition
Radiation quality
Term
Which of the following is the probable HVL of a radiographic x-ray beam at 70 kVp?
Definition
5.0 cm soft tissue
Term
As filtration is added to an x-ray beam:
Definition
Low energy x-rays are removed more readily than high
Term
An increase in mAs will increase which of the following?
Definition
X-ray quantity
Term
It is often stated that mAs controls quantity and kVp controls:
Definition
Quality
Term
However, it should be clear that mAs controls quantity and kVp controls:
Definition
Quality and quantity
Term
If the mA during fluoroscopy is increased by 25%:
Definition
The scatter exposure to the operator is increased by 25%
Term
A minimum HVL is required for diagnostic x-ray beams because:
Definition
A lower HVL would result in an increased absorbed dose to the patient with no improvement in image quality
Term
An x-ray beam can be made to have higher effective energy if which of the following occurs?
Definition
Filtration is added
Term
Filtration will increase:
Definition
X-ray beam quality
Term
Reducing kVP will:
Definition
Soften the x-ray beam
Term
Adding filtration to an x-ray beam will:
Definition
Increase x-ray quality
Term
A radiographic tube has 0.5 mm Al inherent filtration, 1.0 mm Al added filtration, and 1.0 mm Al filtration in the light-localing collimator, Therefore, the total filtration is:
Definition
2.5 mm Al
Term
A representative radiographic tube has 0.5 mm Al inherent filtration and 2.0 mm Al added filtration. An additional 1.0 mm Al filtration will:
Definition
Harden the x-ray beam
Term
Which of the folllowing is the softest radiation?
Diagnostic x-rays, Grenz rays, Megavoltage x-rays, Orthovoltage x-rays, or Supervoltage x-rays
Definition
Grenz rays
Term
The HVL is defined as:
Definition
A thickness of attenuator that will halve x-ray quantity
Term
To measure HVL, which of the following is required?
Definition
A collimator and Aluminum abosrbers
Term
As the HVL of a beam increases, its penetrability:
Definition
Increases
Term
If increasing the kVp increases the HVL, x-ray quantity will:
Definition
Increase by kVp2
Term
If the HVL is increased by the addition of 1 mm Al, x-ray quantity will:
Definition
Decrease
Term
At 70 kVp, the x-ray beam is atttenuated in soft tissue approximately:
Definition
5% /cm
Term
There is a 75% chance that an x-ray will be attenuated by 2 mm lead. The HVL is:
Definition
1.5 mm Pb
Term
What occurs when the small rather than the large cathode coil is energized?
Definition
smaller effective focal spot
Term
Added filtration affects the x-rays beam in what way?
Definition
Increased beam hardening
Term
An aluminum filter:
Definition
Decreases the intensity of all energies of the x-ray beam
Term
If patient thickness is 6 HVLs, what is the approximate intensity at the midline of the patient?
Definition
12%
Term
A diagnostic x-ray beam has an HVL of approximately 3 cm soft tissue. What percentage of the beam is absorbed by a 21 cm abcomen?
Definition
Greater than 90
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