Ch. 27 Contrast (Exp I) Flashcards
The recorded detail of a radiographic image is visible because of:
- Sufficient contrast
- Sufficient density
The difference between two adjacent densities is:
Radiographic contrast
A radiograph with few shades of gray exhibits:
High contrast
Which type of radiograph provides the most information?
Low contrast images
The principal controlling factor of contrast is:
kVp
A radiograph that demonstrates considerable differences between densities is called:
- Short scale
- High contrast
- Increased contrast
A radiograph that demonstrates minimal differences between densities is called:
- Long scale
- Low contrast
- Decreased contrast
A radiograph that demonstrates considerable differences between densities is called:
High contrast
A radiograph that demonstrates minimal differences between density shades is called:
Low contrast
Image receptor contrast is expressed as the _____ of the D log E curve.
Slope
Contrast decreases with:
- Excessive density
- Inadequate density
- A wider range of densities
As the slope of the D log E curve _____, contrast _____.
Increases; increases
As kVp ____, a ____ range of photon energies is produced.
Increases; wider
Contrast increases with all of the following EXCEPT:
a. Decreased kVp
b. Decreased field size
c. Decreased part thickness
d. Increased scatter
d. Increased scatter
High contrast is directly related to:
The number of photoelectric interactions
Which generator type results in the greatest decrease in contrast?
a. Single phase, 2 pulse
b. Three phase, 6 pulse
c. Three phase, 12 pulse
d. High frequency
d. High frequency
Which of the choices does not increase contrast?
a. Increasing grid ratio
b. Increasing the amount of irradiated tissue
c. Decreasing filtration
d. Decreasing kVp
b. Increasing the amount of irradiated tissue
The concept of contrast as it is displayed on a soft-copy monitor for digital images is described as:
Dynamic range
As kVp increases, the percentage of Compton interactions ____ and contrast _____.
Increases; decreases
When the tissue structure of the ankle joint is considered, the dramatic tissue differences between the muscles and bones of the ankle produce:
High subject contrast
A fluoroscopic examination that uses barium as a contrast material would typically produce images with:
Short scale contrast
The total amount of irradiated material is a function of:
Body part thickness and area of exposure
Depending upon the kVp range, a visible change in contrast will not be seen unless kVp is minimally changed:
4-12%
In order to reduce patient entrance skin exposure (ESE), higher kVp exposures are a consideration. It is important to remember that:
kVp values that are too high produce more scatter and reduce contrast
After completing a radiograph using 27 mAs at 90 kVp, the image demonstrates adequate overall density but an area that is underpenetrated. In order to produce an optimum image in terms of contrast and penetration, the repeat image should be taken at:
27 mAs at 100 kVp (15% rule)
kVp controls the proportional relationship of:
Compton and photoelectric interactions
What should you expect to occur with a decrease in kVp?
More photoelectric interactions
When digital imaging receptors are used,
a. kVp is not a consideration
b. Radiographic grids are not necessary
c. An exposure at 90 kVp would require a grid
d. Compton scatter is not a factor
c. An exposure at 90 kVp would require a grid
All of the following factors would affect radiographic contrast EXCEPT:
a. Field size
b. SID and OID
c. Receptor characteristics
d. Focal spot size
d. Focal spot size
An increase in x-ray beam filtration:
- Increases the number of Compton interactions
- Reduces contrast
- Increases the average photon energy
When choosing between two radiographic grids, the k factor is different. Choosing a grid with the higher K factor will produce an image with:
High contrast
With digital imaging systems, the primary factors affecting final image contrast are the:
Histogram and look-up-table (LUT)
