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Image Prod & Eval > Week 6 - Chapter 14 > Flashcards

Week 6 - Chapter 14 Flashcards

1
Q

What are the 3 formulas tied to geometrical qualities of the image?

A
  • Unsharpness Penumbra formula
  • Radiographic Sharpness formula
  • Magnification formula
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2
Q

What is geometrical integrity made up of?

A
  • Sharpness
  • Magnification
  • Shape Distortion
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3
Q

What is another name for geometric integrity?

A

Recognizability

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4
Q

Where is sharpness on a radiograph viewed from?

A

The edges of the object

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5
Q

What does sharpness measure?

A

The extent of blur at the edges of the object

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6
Q

What is the technical term for sharpness?

A

Spatial resolution

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7
Q

What is resolution?

A

The total amount of useful information in an image

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8
Q

What is spatial resolution?

A

The ability to distinguish two objects that are close in proximity to each other

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9
Q

What are two ways in which image resolution can be lost?

A

By blur or loss of contrast

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10
Q

What does a loss in image resolution result in?

A

Difficulty distinguishing details

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11
Q

What is blur?

A

The Unsharpness of an image

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12
Q

What is another name for blur?

A

Penumbra

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13
Q

What are the inner areas of an image without shadows called?

A

Umbra

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14
Q

What would a pure umbra image produce?

A

An image with perfectly sharp edges

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15
Q

Where is penumbra produced on an image?

A

At the edges of the object

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16
Q

What is magnification?

A

The difference between the size of the real object and the size of the projected image

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17
Q

What is magnification a type of?

A

Distortion that changes the size of the object

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18
Q

At what level should magnification be kept in an image?

A

At a minimum

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19
Q

Why is important to keep magnification to a minimum?

A

To make sure the physician sees the object as close to its true size

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20
Q

What is shape distortion?

A

The difference between the shape of the real object and shape of the projected image

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21
Q

What are the two forms of shape distortion?

A

Foreshortening and Elongation

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22
Q

What is Foreshortening?

A

When the object gets compressed in the image

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23
Q

How does Foreshortening occur?

A

When the object is not parallel to the IR or the IR is tilted

24
Q

What is Elongation?

A

When one portion of the object gets stretched out in the image

25
Q

What causes elongation?

A

The angle of the tube

26
Q

Which of the two shape distortions can be fixed?

A

Elongation

27
Q

How is shape distortion expressed in terms of length/width?

A

When the length or the width is changed by elongation/foreshortening, not both changed

28
Q

If all parts of an image is changed uniformly, what type of distortion does that represent?

A

Magnification

29
Q

What are the 3 things Unsharpness is controlled by?

A

SOD, OID and size of the focal spot in the tube

30
Q

What is the Unsharpness Penumbra formula?

A

Unsharpness = Penumbra = FS x OID/SOD

31
Q

What does the Unsharpness Penumbra formula measure?

A

The amount of unsharpness/penumbra that will be spread across a certain area

32
Q

What is the Radiographic Sharpness Formula?

A

Exposure B (SOD/OID) / Exposure A (SOD/OID)

33
Q

What does a higher radiographic number represent?

A

Higher relative sharpness

34
Q

What does the Radiographic Sharpness Formula measure?

A

The quantity of how much sharper one exposure is when compared to another

35
Q

What is a device used to measure sharpness?

A

A line pair tool

36
Q

What 5 factors affect the sharpness of a radiograph?

A
  • Motion
  • Geometry
  • Focal Spot size
  • Size of detector elements
  • Size of monitor picture elements (pixels)
37
Q

If motion could be controlled what would it lead to?

A

Increased image resolution

38
Q

What does motion cause on an image?

A

Blurriness

39
Q

In a magnified image, how are length and width different from the original image?

A

They are both measured larger

40
Q

On radiographs of bones, why is there always some inherent magnification?

A

Because of the soft tissue

41
Q

What is the magnification formula?

A

Image Size/object size = SID/OID

42
Q

What does the magnification formula calculate?

A

The projected size of an image

43
Q

What does SOD equal?

A

SID-OID

44
Q

What are the two factors of resolution (image quality)?

A
  • Visibility
  • Recognizability
45
Q

What are 3 factors of Visibility?

A
  • Brightness
  • Contrast
  • Noise
46
Q

What are 3 factors of Recognizability?

A
  • Sharpness
  • Magnification
  • Shape Distortion
47
Q

What is magnification affected by?

A

SID, OID and to an extent SOD

48
Q

What happens to magnification when the SID is lower?

A

Magnification increases

49
Q

What happens to spatial resolution when magnification increases?

A

It becomes worse

50
Q

What positive role does magnification play in imaging?

A

It can help identify smaller details that otherwise wouldn’t be visible on an actual sized object

51
Q

Which type of x-ray produces the most Foreshortening?

A

Portable x-rays

52
Q

How can you counteract unwanted OID?

A

By increasing SID

53
Q

How does SID relate to magnification?

A

As SID is decreased, magnification increases

54
Q

How is magnification related to sharpness?

A

As magnification is decreased, sharpness increases

55
Q

How does SID relate to sharpness?

A

As SID is increased, sharpness increases

Image Prod & Eval (10 decks)

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