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RT 212 > 5. Digital Radiographic Image Processing and Manipulation > Flashcards

5. Digital Radiographic Image Processing and Manipulation Flashcards

1
Q

The images are processed to mimic the appearance of

A

screen-film images

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2
Q

DIGITAL PROCESSING WILL ALSO

ADJUST FOR TECHNICAL ERRORS:

A

• allow for a wider range of subject contrast
• enhance the spatial frequency of certain tissues
or regions of interest
• allow the radiologist to highlight certain areas of
interest, often with special processing functions

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3
Q

2 STEPS IN IMAGE PROCESSING

A
  1. Preprocessing

2. Postprocessing

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4
Q

Occurs prior to the image being displayed

A

Preprocessing

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5
Q

algorithms determine the image histogram

A

Preprocessing

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6
Q

detector defects are removed

A

Preprocessing

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7
Q

noise corrections are performed

A

Preprocessing

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8
Q

Done by technologist to prepare the image for the

radiologist through various user functions

A

Postprocessing

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9
Q

May also be performed by radiologist to produce
specialized images to aid the radiologist in a
diagnosis

A

Postprocessing

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10
Q

is a graph of the number of pixels in the entire
image or part of the image having the same gray levels (density
values), plotted as a function of the gray levels

A

Image Histogram

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11
Q

y-axis

A

Number of Pixels or Frequency of occurrence of various gray levels

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12
Q

x-axis

A

Pixel Intensity

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13
Q

gray value
representing the
strength of the
acquired signal

A

Horizontal Axis

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14
Q

Pixel intensity

A

Horizontal Axis

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15
Q

Number of pixels in

each tone

A

Vertical Axis

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16
Q

____ of the graph represent black areas (greater acquired signal)

A

One End

Example: Air

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17
Q

shade of gray, representing medium tones

A

Middle Area

Example: Soft tissue, muscle

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18
Q

represents white (no acquired signal)

A

Extreme Opposite Area

Example: Bone

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19
Q

This graphic representation appears as a pattern of peaks and valleys
that varies for each body part

A

Image Histogram

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20
Q

creates a wider histogram

A

Low energy (low kVp)

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21
Q

long scale of contrast

A

Low energy (low kVp)

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22
Q

creates a narrow histogram

A

High energy (high kVp)

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23
Q

short scale of contrast

A

High energy (high kVp)

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24
Q

Analysis of the histogram is very

A

complex

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25
Q

The shape of the histogram is ____ specific

A

anatomy

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26
Q

It is important to choose the correct _____ on the

menu for the body part exposed

A

anatomic region

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27
Q

Digital Radiography Signal Sampling

A
  1. The Nyquist Theorem
  2. Aliasing
  3. Rescaling
  4. Look-up Table
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28
Q

described a way to convert analog signals into digital

signal that would more accurately transmit over telephone lines

A

1928 – Harry Nyquist

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29
Q

Sampling

A

Nyquist Theorem

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30
Q

states that when sampling a signal (ADC)
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

A

Nyquist Theorem

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31
Q 
In digital imaging, at 
least \_\_\_\_ the 
number of pixels 
needed to form the 
image must be 
sampled
A

twice

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32
Q

If too few pixels are sampled, the result will be a

A

lack of resolution

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33
Q

when the spatial frequency is greater than the Nyquist frequency & the sampling occurs less than twice per cycle, information is lost and a
fluctuating signal is produced

A

Aliasing

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34
Q

Undersampling

A

Aliasing

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35
Q

when the (fluctuating) signal is reproduced, frequencies above the Nyquist frequency causes

A

Aliasing (Foldover or Biasing)

36
Q

causes mirroring

of the signal at ¼ the frequency

A

Aliasing (Foldover or Biasing)

37
Q

a wraparound image is produced, which
appears as two superimposed images
that are slightly out of alignment, resulting in a

A

Moire effect

38
Q

when exposure is greater or less than what is needed to produce an image, it occurs in an effort to display the pixels for the area of interest

A

Automatic Rescaling

39
Q

means that images are produced with uniform brightness and contrast,
regardless of the amount of exposure used to acquire the image

A

Automatic Rescaling

40
Q

Histogram of the luminance values derived during image

acquisition

A

Look-up Table

41
Q

Used as a reference to evaluate the raw information & correct the
luminance values

A

Look-up Table

42
Q

This is a mapping function in which all pixels (each with its own
specific gray value) are changed to a new gray value

A

Look-up Table

43
Q

are data stored in the computer that is used to

substitute new values for each pixel during the processing

A

Look-up Table (LUT)

44
Q

The resultant image will have the appropriate appearance in

brightness and contrast

A

Look-up Table (LUT)

45
Q

There is a ___ for every

anatomic part

A

LUT

46
Q

The LUT can be graphed by plotting the original values ranging from ____ on the horizontal axis and the new values (0-255) on the vertical axis

A

0 to 225

47
Q

displayed as black

A

< 50

48
Q

displayed as white

A

> 250

49
Q

displayed as shades of

gray

A

50-150

50
Q

Quality Control
Workstation Functions

Image Processing Parameters

A
  1. Contrast Manipulation
  2. Spatial Frequency Resolution
  3. Spatial Frequency Filtering
51
Q

Spatial Frequency Filtering

A
  1. Edge Enhancement

2. Smoothing

52
Q

Converting the digital input data to an image with appropriate
brightness and contrast using contrast enhancement
parameters

A

Contrast Manipulation

53
Q

No amount of adjustment can take the place of ____ technical
factors selection

A

proper

54
Q

Ability of an imaging system to differentiate between two near-by objects

A

Spatial Frequency Resolution

55
Q

The detail or sharpness of

an image

A

Spatial Frequency Resolution

56
Q

A large pixel size will be
unable to resolve two near-by structures as compared
to a small pixel size

A

Spatial Frequency Resolution

57
Q

Measured in lp/mm

A

Spatial Frequency Resolution

58
Q

high-pass filtering

A

Edge Enhancement

59
Q 
Occurs when fewer 
pixels in the 
neighborhood are 
included in the signal 
average
A

Edge Enhancement

60
Q

useful for enhancing large structures such as organs and soft tissue, but it can be noisy

A

Edge Enhancement

61
Q

low-pass filtering

A

Smoothing

62
Q

Occurs by averaging each pixel’s frequency with surrounding

pixel values to remove high-frequency noise

A

Smoothing

63
Q

Useful for viewing small structures such as fine bone tissues

A

Smoothing

64
Q

Basic Functions of the
Processing System

Post-Processing Image Manipulation

A
  1. Window Level & Window Width
  2. Background Removal or Shuttering
  3. Image Stitching
  4. Image Annotation
  5. Magnification
65
Q

Most common image post-processing parameters are those for _____ and _____

A

brightness, contrast (Window Width & Level)

66
Q

controls how bright or dark the screen image is.

A

Window Level

67
Q

controls the ratio of the black and white, or contrast

A

Window Width

68
Q

The higher the level is, the ____ the image will be, and the wider the
window width, the ____ the contrast

A

darker (higher),

lower (wider)

69
Q

excess light

A

Veil Glare

70
Q

is used to blacken out the white collimation borders,

effectively eliminating veil glare

A

Automatic shuttering

71
Q

unexposed borders around
the collimation edges
allows excess light to enter
the eye

A

Veil Glare

72
Q

causes oversensitization of
a chemical within the eye
called _____

A

Veil Glare,

rhodopsin

73
Q

results in temporary white

light blindness

A

Veil Glare

74
Q

Removing the white unexposed borders results in an overall smaller number of pixels & ____ the amount
of information to be stored

A

reduces

75
Q

refers to the way anatomy
is oriented on the imaging
plate

A

Image Orientation

76
Q

The image is displayed
exactly as it was read
unless the reader is
informed differently

A

Image Orientation

77
Q

When anatomy or the area of interest is too large to fit on one
cassette, multiple images can be “_____” together using specialized
software programs

A

stitched (Image Stitching)

78
Q

allows selection of preset terms and/or manual text input & can
be particularly useful when such additional information is necessary

A

Image Annotation

79
Q

a box placed over a small segment of anatomy on the main image
shows a magnified version of the underlying anatomy

A

Magnification

80
Q

Magnification of the entire image

A

pan navigation

81
Q

Image Management

A
  1. Patient Demographic Input
  2. Manual Send
  3. Archive Query
82
Q

Proper identification of the patient is even more critical with digital images than with conventional hard copy film/screen
images

A

Patient Demographic Input

83
Q

Patient Demographic Input Includes:

A
  • patient name
  • health-care facility
  • patient identification number
  • date of birth
  • examination date
84
Q

arise if the patient name is entered differently from visit to visit or examination to examination

A

Problems

85
Q

This function allows the QC technologist to select one or more local computers to receive images

A

Manual Send

86
Q

Most QC workstations are set to automatically send a completed
image to the appropriate destinations

A

Manual Send

87
Q

function that allows retrieval of images from the PACS based on
date of examination, patient name or number, examination number,
pathologic condition or anatomic area

A

Archive Query

RT 212 (10 decks)

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