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Radiologic Exposures > Final Review: Spacial Resolution and Distortion > Flashcards

Final Review: Spacial Resolution and Distortion Flashcards

1
Q

Two geometric properties:

A

-spacial resolution
-distortion

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2
Q

Spacial resolution is referred to several terms:

A

-definition
-sharpness
-recorded detail

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3
Q

A misrepresentation in an image of an objects size or shape is called

A

distortion

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4
Q

what happens to recorded detail when there is less distortion

A

recorded detail increases

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5
Q

what happens to the recorded detail as the magnification increases

A

recorded detail decreases

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6
Q

what are the two types of distortion

A

size and shape distortion

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7
Q

size distortion is also called:

A

magnification

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8
Q

is called elongation when a structure appears longer in an image than the structure really is, and foreshortened when the structure appears shorter

A

Shape distortion

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9
Q

How can magnification be kept minimal?

A

increase in SID and decrease in OID

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10
Q

what law describes how the xray beam diverges, the principle that accounts for magnification and unsharpness

A

Divergence or penumbra law

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11
Q

what is kept minimized as possible to reduce magnification

A

OID

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12
Q

increases the OID about 4in and increases the magnification of the image

A

use of a grid

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13
Q

What kind pf distortion is present on every radiograph?

A

Magnification- because there will always be OID

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14
Q

Ability of imaging system to image structures as separate and distinct

A

Spacial Resolution

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15
Q

Dependent on matrix size, pixel size, and grayscale bit depth

A

Spacial Resolution

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16
Q

what happens to spacial resolution when there is an increases matrix and decreased pixel size

A

increased spacial resolution

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17
Q

what wavelength is high spacial frequency

A

short wavelength

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18
Q

what wavelength is low spacial frequency

A

long wavelength

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19
Q

what represents your rows and columns

A

matrix

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20
Q

what represents your individual squares

A

pixels

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21
Q

Compare digital and film to dynamic range

A

Digital has more dynamic range and film has less dynamic range

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22
Q

unit of resolution

A

lp/mm

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23
Q

Penumbra

A

-unsharpness or blur

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24
Q

high spacial resolutions is expressed as

A

high frequency

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25
Q

More shades of gray, better spacial resolution(more detail)

A

Gray Scale

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26
Q

noise

A

Unwanted on image

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27
Q

Assessing Recorded Detail

A

Spacial Resolution
Spacial Frequency
Noise

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28
Q

-Ability of imaging system to accurately display objects in two dimensions
-penumbra vs. umbra

A

Spacial Resolution

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29
Q

-High frequency signal
-determined by measuring distance between pairs of lines distinct from one another

A

spacial frequency

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30
Q

what happens to signal when noise is decreased

A

increases

31
Q

umbra

A

sharpness

32
Q

Measures accuracy of image to actual image
-range from 0-1
- 1 represents “perfect”
reproduction of original

A

MTF

33
Q

As higher spacial frequencies occurs what happens to MTF

A

falls dramatically

34
Q

Bit Depth

A

how many shades of gray that pixel can hold

35
Q

Ability to capture and display subtle energy differences in area of interest
-responsible for low energy, shades of gray on image

A

Low Contrast Resolution (LCR)

36
Q

Background information received by image receptor

A

noise

37
Q

Types of Noise:

A

System Noise
Ambient Noise
Quantum Noise

38
Q

Best Spacial Resolution

A

small focal spot
increased SID
decreased OID

39
Q

Resolution as a function of exposure time and dynamic motion of body part

A

Temporal Resolution
Extremely low exposure times optimize TR

**I dont think we went over this but just put it in here just in case lolll

40
Q

-artifact if sampling frequency inst working
-occurs when Nyquist criterion not met

A

Aliasing(moire pattern)

41
Q

Factors affecting recorded detail

A

Eliminate motion
reduce oid
reduce focal spot size
use detector with smallest detector element (DEL)
reduce intensifying screen phosphor size and concentration (film)
increase SID

42
Q

-line focus principle
-creates a penumbra and inherent loss of sharpness due to focal spot geometry and distance -a major factor in spacial resolution

A

Focal Spot Size

43
Q

-some degree of image unsharpness occurs due to shape and size of patient anatomy
-related to beam divergence and incongruence with anatomical structures

A

Attenuation/Absorption Unsharpness

44
Q

Image processing system limits recorded detail dependent on:

A

-matrix(large)
-pixel (small)
-bit depth (large)

45
Q

Motion

A

-voluntary (communication)
-Involuntary motion( exposure time reduction and immobilization)
-equipment motion

46
Q

how to reduce voluntary motion

A

best reduced through effective communication

47
Q

how to reduce involuntary motion

A

-best reduced through short exposure time
-immobilization

48
Q

Anatomic details must be recorded accurately and with the greatest amount of sharpness

A

Recorded Detail

49
Q

Refers to the distinctness or sharpness of the structural lines that make up the recorded film image

A

Recorded Detail

50
Q

What affects distortion?

A

CR alignment of the tube, part, and image receptor

51
Q

Radiographic misrepresentation of either the size or shape of the anatomic part

A

Distortion

52
Q

an increase in the objects image size compared to its true or actual size
-SID and OID affect magnification

A

Size distortion

53
Q

A misrepresentation of an objects image shape
-elongation and foreshortening

A

Shape Distortion

54
Q

Radiographic distances

A

-controlled by SID and OID
-Magnification only

55
Q

electronic magnification/minification

A

post processing can resize image

56
Q

SID is a major factor for magnification

longer SID yields less magnification

Longer SID’s advocated by experts

Decreases entrance skin exposure

A

SID

57
Q

OID is a critical distance for magnification and spacial resolution

OID should be minimized, whenever possible, to minimize magnification and improve resolution

A

OID

58
Q

Unwanted exposure to the image receptor resulting in fog
-a result of Compton
interactions
-provides no useful
information
-scatter of fog decreases
image contrast

A

Scatter

59
Q

in medical radiography, image size is always larger than object size
O=I/M

A

O=object size
I=image size
M=magnification factor

60
Q

M= SID/SOD

A

magnification factor

61
Q

Role of central ray

A

Alignment
-central ray
-anatomical part
-Image Receptor

Angulation
-Degree
-Direction

62
Q

if an angle is needed, what is better to angle for better spacial resolution

A

better spacial resolution is achieved by angling body part rather than angling central ray

63
Q

what is an example of purposeful distortion

A

Radiographic positioning

64
Q

SOD=

A

SID-OID

65
Q

As the primary beam passes through the patient it will lose some of its orginal energy. This reduction in the energy of the primary beam is known as :

A

Beam Attenuation

66
Q

To maintain exposure to IR:

A

increase mA and proportionally decrease time

increase time and proportionally decrease mA

increase kvp 15% and decrease mAs by a half

Decrease kvp 15% and increase mAs by two times

67
Q

To increase or decrease exposure to IR what do you do to mA, exposure time or kVp

A

Increase:
increase mA, exposure time or kVp

Decrease:
decrease mA, exposure time and lVp

68
Q

increases penetration and decreases absorption

A

increasing kvp

69
Q

decreases penetration and increases absorption

A

decreasing kVp

70
Q

what type of wavelength is there when the kvp is higher

A

shorter the wavelength

and lower the kvp, longer the wavelength

71
Q

Doing what to the OID will increase the exposure to the IR, decrease contrast and magnification, and increase recorded detail/ spacial resolution

A

Decreasing OID

72
Q

Distance between the anatomic part and IR will affect:

A

-radiation intensity reaching the ir
-amount of scatter radiation reaching the ir
-magnification
-recorded detail/spacial resolution

73
Q

Practice:
penumbra equation
magnification factor

A

Radiologic Exposures (11 decks)

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