Question 1

Spatial frequency is used to describe the quality of spatial resolution in terms of _____________.

Accepted Answer

Spatial frequency relates to the number of line pairs in a given length, usually centimeters or milliliters.

Question 2

If a digital radiography imaging system has a spatial resolution of 10 lp/mm, what is the pixel size of that system?

Accepted Answer

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.

Question 3

If there were such thing as a perfect imaging system, the MTF would be equal to ________.

Accepted Answer

In a perfect system, the image size would equal the object size, and the MTF would therefore be equal to one.

Question 4

The two principal characteristics of a medical image are _______________________.

Accepted Answer

Spatial resolution and contrast resolution are the two principal characteristics of a medical image.

Question 5

The portion of useful image-forming x-rays is referred to as the ___________.

Accepted Answer

The portion of useful image-forming x-rays is referred to as the signal.

Question 6

As spatial frequency increases, the object size _____ and the spatial resolution _____.

Accepted Answer

As spatial frequency increases, the object size decreases and the spatial resolution increases.

Question 7

In digital imaging, spatial resolution is ultimately limited by ___________________.

Accepted Answer

A digital imaging system cannot resolve anything smaller than one pixel.

Question 8

Screen-film radiography has a dynamic range of __________.

Accepted Answer

Screen-film radiography has a dynamic range of 1000.

Question 9

Image detail is also called _______________________.

Accepted Answer

Image detail is also called spatial resolution.

Question 10

What is the spatial frequency of a digital system that can resolve 100 µm?

Accepted Answer

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.

Question 11

The number of gray shades that an imaging system can reproduce is called its ________________.

Accepted Answer

The number of gray shades that an imaging system can reproduce is called its dynamic range.

Question 12

The human visual system can distinguish ________ shades of gray.

Accepted Answer

The human visual system can distinguish no more than 30 shades of gray.

Question 13

The ________________ digital imaging system uses the highest dynamic range.

Accepted Answer

The mammography digital imaging system uses the highest dynamic range.

Question 14

Of all radiographic imaging systems, _____________ has the best contrast resolution.

Accepted Answer

CT has the best contrast resolution of all x-ray imaging systems because of x-ray beam collimation and the resultant reduction in scatter radiation.

Question 15

The use of two screens in imaging results in a higher _______.

Accepted Answer

The use of two screens increases the MTF because spatial resolution and spatial frequency are decreased. Pixel size is not affected by screens.

Question 16

If a digital system has a spatial resolution of 4 lp/mm, it can resolve an object as small as _____ mm.

Accepted Answer

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

Question 17

A _______________ test tool is used to acquire data for an MTF curve.

Accepted Answer

A bar pattern test tool is used to acquire data for an MTF curve.

Question 18

Recent studies have shown that denser breast tissue is best imaged with _____________________.

Accepted Answer

Recent studies have shown that denser breast tissue is best imaged with digital mammography.

Question 19

As mAs is increased the signal-to-noise ratio is ____________.

Accepted Answer

As mAs is increased the signal-to-noise ratio is increased.

Question 20

The bit capacity of each pixel identifies the ___________ of a digital imaging system.

Accepted Answer

The bit capacity of each pixel identifies the dynamic range of a digital imaging system.

Quiz 17: Digital Radiographic Technique