Chapter 13 Digital Radiographic Technique-Bushong Test Bank

Chapter 13 Digital Radiographic Technique Bushong: Radiologic Science for
Technologists




MULTIPLE CHOICE
1. The two principal characteristics of a medical image are .
a. spatial resolution and noise
b. spatial resolution and contrast resolution
c. contrast resolution and modular transfer function
d. contrast resolution and dynamic range




ANS: B
Spatial resolution and contrast resolution are the two principal characteristics of a
medical image.
2. Spatial frequency is used to describe the quality of spatial resolution in terms of
.
a. pixel size
b. modular transfer function
c. line pairs
d. contrast resolution




ANS: C
Spatial frequency relates to the number of line pairs in a given length, usually
centimeters or milliliters.
3. In digital imaging, spatial resolution is ultimately limited by .
a. focal spot size
b. spatial frequency
c. contrast resolution

, d. pixel size




ANS: D
A digital imaging system cannot resolve anything smaller than one pixel.
4. What is the spatial frequency of a digital system that can resolve 100 µm? a. 5 lp/mm
b. 10 lp/mm
c. 50 lp/mm
d. 100 lp/mm




ANS: B
If a line is 100 µm, a line pair is 200 µm; therefore, 1 lp/200 µm = 1 lp/0.2 mm, which
equals 20 lp/mm.
5. If a digital system has a spatial resolution of 4 lp/mm, it can resolve an object as small
as mm.
a. 8
b. 4
c. 0.25
d. 0.125




ANS: D
A spatial resolution of 4 lp/mm resolves 8 objects per mm, each object being 1/8 mm,
or
0.125 mm.


6. As spatial frequency increases, the object size and the spatial resolution . a.
increases; increases

, b. decreases; decreases
c. decreases; increases
d. increases; decreases




ANS: C
As spatial frequency increases, the object size decreases and the spatial resolution
increases.
7. If a digital radiography imaging system has a spatial resolution of 10 lp/mm, what is the
pixel size of that system? a. 0.05 mm
b. 0.5 mm
c. 0.1 mm
d. 0.01 mm




ANS: A
A system with a spatial resolution of 10 lp/mm resolves 20 pixels/mm; therefore, each
pixel is 1/20 mm in size or 0.05 mm.
8. If there were such thing as a perfect imaging system, the MTF would be equal to . a.
five
b. one
c. two
d. four




ANS: B
In a perfect system, the image size would equal the object size, and the MTF would
therefore be equal to one.
9. A test tool is used to acquire data for an MTF curve. a. bar pattern