Ch. 2: Summary

Question 1

What are the two types of images in radiography?

Answer 1

Analog and digital

Question 2

What does analog capture measure?

Answer 2

A continuously changing signal

Question 3

What does digital image capture record?

Answer 3

A finite number of bits of information

Question 4

In analog systems, how is x-ray energy recorded?

Answer 4

It is converted to light and recorded on film

Question 5

What do digital systems obtain for image capture?

Answer 5

Multiple signal samples

Question 6

How do digital images begin in radiography?

Answer 6

As analog signals that are recorded and turned into electrical signals, which are then digitized

Question 7

What are digital images made up of?

Answer 7

Pixels of different sizes and shades of gray

Question 8

What happens when pixel size decreases?

Answer 8

More pixels can be used for an image, increasing depth and shades of gray that can be recorded

Question 9

How are pixels arranged in a digital image?

Answer 9

In columns and rows called a matrix

Question 10

How does matrix size relate to pixel size?

Answer 10

The larger the matrix, the smaller the pixels

Question 11

What is field of view (FOV) in digital imaging?

Answer 11

The amount of patient tissue included in the image

Question 12

How does changing matrix size affect FOV?

Answer 12

Matrix size can change without affecting FOV, but changing either affects pixel size

Question 13

What is brightness in digital imaging?

Answer 13

The image appearance on the display monitor

Question 14

What factors can affect brightness on the monitor?

Answer 14

Reflected (illuminance) and transmitted (luminance) light, especially on monochromatic monitors

Question 15

What is contrast resolution?

Answer 15

The digital system’s ability to demonstrate subtle gray shade differences, especially in adjacent structures

Question 16

What determines contrast resolution in a digital image?

Answer 16

Pixel bit depth

Question 17

How do kVp and mAs relate to contrast resolution?

Answer 17

Higher kVp and lower mAs values are possible with better contrast resolution

Question 18

Why is scatter control critical in digital imaging?

Answer 18

Because digital image receptors are very sensitive to scatter radiation

Question 19

What is spatial resolution?

Answer 19

The ability to distinguish small structures from background and noise

Question 20

What is spatial resolution directly related to?

Answer 20

Pixel size

Question 21

What is modulation transfer function (MTF)?

Answer 21

The ability of system components to accurately reproduce structural details of an object within the image

Question 22

What limits image resolution according to MTF?

Answer 22

The component in the system that produces the least resolution

Question 23

What are two types of noise that can affect digital images?

Answer 23

Anatomic noise and equipment noise

Question 24

Who can control anatomic noise?

Answer 24

The radiographer

Question 25

Can equipment noise usually be controlled?

Answer 25

No, equipment noise usually cannot be controlled

Question 26

What is latitude in digital imaging?

Answer 26

The range of exposures a digital detector can respond to

Question 27

What does image latitude depend on?

Answer 27

The detector and the available contrast resolution

Question 28

What does detective quantum efficiency (DQE) measure?

Answer 28

The efficiency of a system to convert the x-ray input signal into a useful output image