X-ray Emission Spectrum Ch 7 Flashcards
The primary beam is characterized by…
Quantity and Quality
What is the quantity of the beam?
The number of x-rays in the beam
What is the quality of the beam?
The penetrability of the beam
Quantity is also known as…
Intensity and radiation exposure
What is quantity measured in?
Roentgens or milliroentgens
Quantity is ______ proportional to mAs.
Directly
What is the ratio of x-ray quantity and mAs?
I1 = mAs 1
_________
I2= mAs2
If you double the mAs, what happens to the intensity?
You double the intensity
What is the ratio of x-ray quantity and kVp?
I1= (kVp1)2
_________
I2 = (kVp2)2
Quantity is proportional to the _____ of the ratio of the kVp.
Square
What is used to determine how kVp affects the quantity?
15% rule
What is the 15% rule?
If you increase the kVp by 15% you will double the mAs/ density on the image
What would happen to the density if you decrease the kVp by 15%?
You would half the mAs/ density
Quantity varies _____ as the square of the distance from the target.
Inversely
What is the square law?
mAs1 = (SID1)2
____________
mAs2 = (SID2)2
To maintain a constant exposure to the image receptor when SID changes, _____ must be increased by the SID2.
mAs
What are factors that affect quantity?
- mAs
- kVp
- Distance
- Filtration
What does filtration do to x-rays?
The quantity is reduced by removing low energy x-rays.
Why would you want to remove low energy photons?
Because they only increase pt. dose
What factors affect quality?
- kVp
2. Filtration
Factors that affect x-ray beam quality also influence radiographic ________.
Contrast
______ and mAs do not affect quality.
Distance
In radiography the quality of x-rays are measured in _____.
HVL
The HVL of an x-ray beam is the thickness of absorbing material necessary to reduce the x-ray _____ to 1/2 of its original value
Intensity
A diagnostic x-ray beam usually has an HVL in the range of _____ AL or 3-6 cm of soft tissue
3-5mm
Quality is increased as ___ is increased.
kVp
An increase in ______ will effect the x-ray emission spectrum to shift to the high energy side (to the right of the curve) indicating an increase in the effective energy of the beam.
kVp
An increase in kVp also causes an increase in ____.
HVL
Quality is increased with increased _______.
Filtration
What is the primary purpose of filtration?
To remove low energy photons
Why is aluminum primarily used?
- Efficiency- Photoelectric effect
- Availability
- Cost
What are the types of filtration?
- Inherent filtration
- Added filtration
- Compensating filters
- Total filtration
What is inherent filtration?
Glass or metal enclosure of the tube
The tube starts with ____ AL equivalent filtration.
.5mm
Inherent filtration will increase with age due to…
Sunburning
What is added filtration?
Something that is placed between the tube and the collimator (usually AL)
What are compensating filters?
Used to produce a uniform intensity on the image receptor when imaging body parts of varying thicknesses
How is total filtration found?
By adding the thicknesses of the filters in the tube, collimator housing and compensating filters
What is the most common compensating filter?
Wedge
