Digital Data

Question 1

Smallest element in a digital image
-discrete values

Answer 1

Pixel

Question 2

The process of associating the pixels with discrete values

Answer 2

Maximum contrast resolution

Question 3

What is the size of the pixel directly related to?

Answer 3

Spatial resolution or detail in the image

Question 4

T/F
Pixel size may change when the size of the matrix or FOV changes

Answer 4

True

Question 5

The amount of information that can be stored in the pixel (shades of grey that can be represented)

Answer 5

Pixel bit depth

Question 6

T/F
The number of grey tones that a pixel can produce is 2 to the power of the bit depth

Answer 6

True
See side 7

Question 7

What is the determining factor for contrast resolution?

Answer 7

Bit depth

Question 8

What is the bit depth in most digital imaging systems?

Answer 8

10-16

Question 9

The grey level will be a factor in determining what?

Answer 9

Image contrast resolution

Question 10

What are the typical matrix sizes?

Answer 10

512x512
1024x1024
2500x2500

Question 11

What is the relation in matrix and pixel size?

Answer 11

Large matrix - small pixel
Small matrix - large pixel

Question 12

Area imaged

Answer 12

Field of view (FOV)

The larger the FOV, the more area imaged

Question 13

T/F
Changes in FOV will not affect matrix size

Answer 13

True

Question 14

When a field of view gets smaller, what happens to the pixel size, and spatial resolution?

Answer 14

Smaller pixels

Increased spatial resolution

Question 15

T/F
Changes in matrix size does not affect contrast resolution

Answer 15

True
Pixel bit depth affects contrast resolution

Question 16

Will changing the matrix size, and or the files of view change the pixel size?

Answer 16

Yes

Question 17

What is the relationship between pixel size and FOV?

Answer 17

Direct

Increased FOV = increased pixel size

Question 18

What is the relation between pixel size and matrix size?

Answer 18

Inverse

Increased matrix size = decreased pixel size

Question 19

The amount of exposure received by the IR

Answer 19

Exposure index

Question 20

The images appearance on the display monitor of the computer

(The amount of light transmitted by the monitor as well as light reflected off the monitor can affect image appearance)

Answer 20

Brightness

Question 21

How can brightness be adjusted?

Answer 21

Adjusting window level

Question 22

Ability of the digital system to display subtle changes in the shade of grey
-directly related to pixel depth

Answer 22

Contrast resolution

Question 23

How can contrast resolution be adjusted?

Answer 23

Window width
(Control contrast towards a longer or shorter scale)

Question 24

T/F
If contrast is too low, it can be difficult to separate the image signal from noise and background

Answer 24

True

Question 25

The ability of the imaging system to demonstrate small details

Answer 25

Spatial resolution Digital radiography has a higher dynamic range: -can respond to a wider variety of levels of exposure -more tissue densities are seen, giving the appearance of more detail

Question 26

What is related to spatial resolution in computed radiography (PSP systems)?

Answer 26

-Phosphor layer thickness -pixel size

Question 27

What is related to spatial resolution in digital radiography?

Answer 27

Pixel size

Question 28

The ability of a system to record available spatial frequencies

Answer 28

Modulation transfer function (MTF)

Question 29

What would the MTF of a perfect system be?

Answer 29

1or 100%

Question 30

Anything that interferes with image formation

Answer 30

Noise

Question 31

Superimposition of body parts

Answer 31

Anatomic noise

Question 32

Noise that occurs during image acquisition

Answer 32

Radiographic noise

Question 33

Noise that occurs from detector elements Non uniform response

Answer 33

Equipment noise

Question 34

How much noise can be tolerated in an image

Answer 34

Signal to noise ratio (SNR) As SNR increases, noise decreases *different detectors will require different amounts of exposure to achieve the same SNR

Question 35

Range of exposure diagnostic image values the IR is able to produce

Answer 35

Exposure latitude Increased dynamic range = more values can be detected

Question 36

How efficiently a system converts the xray input signal into a useful output image A measurement of the percentage of X-rays absorbed when they hit the detector

Answer 36

Detective quantum efficiency

Question 37

What are some examples of analog?

Answer 37

-paintings -printed photographs -continuous images

Question 38

What are some examples of digital?

Answer 38

-numeric values -array of small elements

Question 39

Xray converted to light, and the light waves are recorded as single intensities

Answer 39

Analog

Question 40

Analog signals are converted to number to be recorded Digital images formed through multiple samplings of the signal

Answer 40

Digital

Question 41

When does analog to digital conversion occur in imaging?

Answer 41

-CR reader -digital imaging -film digitizers

Question 42

What are the 3 steps in analog to digital conversion? (ADC)

Answer 42

Sampling Quantification Binary coding

Question 43

The analog voltage values are measured at a chosen sampling frequency on the analog waveform

Answer 43

ADC: sampling

Question 44

Each sampled piece of analog data is the computed and assigned a discrete analog value

Answer 44

ADC: quantificstion

Question 45

Sampled values are converted to a binary digit (bit)

Answer 45

Binary coding

Question 46

When sampling a signal, the sampling frequency must be greater than twice the frequency of the input signal so that the reconstruction of the original image will be as close to the original signal as possible

Answer 46

Nyquist theorem

Question 47

Results in a wraparound image, which appears a two superimposed images that are slightly out of alignment, resulting in a moire effect

Answer 47

Aliasing