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Imaging Applications and Quality > Unit 3: Radiographic Image Artifacts > Flashcards

Unit 3: Radiographic Image Artifacts Flashcards

1
Q

What two types of analysis is involved in an outcome asessment?

A

1.Repeat analysis
2.Artifact analysis

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2
Q

What is the purpose of repeat analysis?

A

PRovides important information about equipment preformance, departmental procedures and the skill level of the technologist

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3
Q

What are the 3 benefits of repeat analysis?

A
  1. IMproved department efficiency
  2. Lower department costs
  3. Lower patient radiation dose
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4
Q

When collecting information for repeat data analysis, how often is it collected and how large is thee sample for analysis?

A

-Collected monthly
-Paitent spample of at least 250 patients

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5
Q

How do you calculate the causal repeat rate?

A

Causal repeat rate= # of repeats for a specific cause/total number of repeats x 100

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6
Q

What is causal repeat rate?

A

The percentage of repeats from a specific cause

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7
Q

What is the most common cause of repeats?

A

Positioning errors

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8
Q

In what two ways is causal repeat rate collected?

A
  1. Department staff enter the number manually and cause of repeat into RIS
  2. Automatically tabulated when images are ejected at the viewing monitor
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9
Q

How do you calculate total repeat rate?

A

Total repeat rate=Total # of repeat images/total # of images taken x 100

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10
Q

As per SC35, what should the repeat rate be?

A

Less than 5%

(may not be practical in all departments)

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11
Q

Is the benchmark repeat rate higher or lower than SC35 at most hospitals?

A

Benchmark is set lower, so if you go higher, you are still under SC35 regulations

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12
Q

T/F

Artifacts can be generated at any step of the CR imaging workflow

A

True

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13
Q

What are the two categories of repeats for artifacts with CR plates?

A
  1. Image acquisition based
  2. Image processing based
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14
Q

What are the types 10 of operator errors that contribute to image acquisition artifacts in CR?

(Don’t have to memorize list, just know what happens)

A
  1. Twin artifacts (double exposure)
  2. Improper collimation
  3. Delayed scanning
  4. Exposure through back of the cassette
  5. Inappropriate exposure factors
  6. Scatter
  7. Care and Handling
  8. Light bulb effect
  9. Improper Grid usage: Moire
  10. Improper grid usage: Grid lines

(good to read over)

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15
Q

At what point does the CR plate become subject to fading?

A

After 48 hours of not processing the CR plate

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16
Q

T/F

The central primary beam consists of high E photons, wheras the low E photons are in the periphery. Hence, fading starts from the central.

A

FALSE: The central primary beam consists of high E photons, wheras the low E photons are in the periphery. Hence, fading starts from the periphery.

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17
Q

What does an overexposure error result in for the image?

A

Irreversible darkening of image, obscuring the details

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18
Q

What does an underexposure appear as in an image?

A

Grainy appearance due to quantum mottle

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19
Q

T/F

Noise primarily masks anatomy that is simular shades of grey

A

True

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20
Q

What is one of the primary causes of artifiacts caused by operator errors?

A

Negligence of care and handling of CR plates

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21
Q

What does buckling of CR plates occur from?

A

Mishandling of imaging plates by techs during the cleaning processes

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22
Q

What does buckling of CR plates cause?

A

Kink artifacts at the sites where the imaging plate is bent

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23
Q

What is the risk of kind artifiacts?

A

Can imitate pathological conditions

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24
Q

What causes phantom images on CR plates?

A

The use of corrosive cleaning agents damges the PSP

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25
Q

What artifact is seen here?

A

Kink artifact due to buckling

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26
Q

What is this artifact a result of?

A

Artifact due to corrosive cleaning agents

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27
Q

What is the reason for the light bulb effect occuring?

A

Increased exposure for obese patients and uncollimated x-ray beam

This increased exposure is due to the wide dynamic range and high sensitivity of the imaging plate.

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28
Q

What artifact is seen here?

A

Light bulb effect

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29
Q

How do you fix the light bulb effect?

A

Reducing backscatter by lowering the kilovoltage or by more precise collimation will limit the prevalence and impact of this artifact.

(not always possible)

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30
Q

What is the : Moire’ Pattern caused by in CR?

A

Caused when the grid lines on a low frequency stationary grid are parallel to the CR reader scan lines.

(Subtle)

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31
Q

What artifact is seen here?

A

Moire’ pattern

The moire´ pattern seen in this knee image was caused by using a grid with a frequency of 33 lines/cm, which was oriented with the grid lines parallel to the plate reader’s scan lines.

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32
Q

What is the Artefact remedy for the Moire’ pattern?

A
  1. Use grids with no less than 60 lines/cm.
  2. Grid lines should run perpendicular to the plate reader’s laser scan lines.
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33
Q

What artifact caused by error is this describing?

Failure of the grid to move during exposure, improper grid focusing distance, improper angulation of the central ray with respect to the grid lines, or improper centering of the tube.

A

Improper Grid Usage: Grid Lines

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34
Q

What artifact is seen here?

A

Grid Line Artifact

(very strong in terms of contrast)

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35
Q

What are the 2 subsections of Image Processing Artifacts?

A

Hardware- and software-induced artifacts.

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36
Q

What is the sampling frequency (Nyquist frequency)?

A

The number of these scanned lines per millimeter in the PSP scanner

37
Q

What does the Nyquist frequency determine?

A

Determines the spatial resolution of the images produced.

38
Q

What theorum is this describing?

Sampling rate (lp/mm) should be at least double the desired maximum spatial frequency to prevent aliasing.

A

Nyquist Theorem

39
Q

What artifact is seen here?

A

Moire’ Pattern due to Aliasing

40
Q

What is halo artifact and what causes it?

A

Appears as dark bands at the interface of structures that differ widely in brighness levels such as barium examnations or metal prosthesis.

41
Q

What is imaging plate artifact?

A

Cracks in the IR

42
Q

What is imaging plate artifacts-cracks caused by?

A

Mechanical stress in the form of cracks resulting from aging of the iamging plate and roller indued artifacts.

43
Q

What artifact is seen here?

A

Halo artifact

44
Q

Where do imaging plate artifact (cracks) initally appear?

A

Initally appear at the edges of the image plate where they tend not to hinder image interpretation.

As cracks progress they travel more central

45
Q

How long can a properly maintained imaging plate last before it needs to be replaced?

A

5 years before it needs to be replaced

46
Q

What artifact is seen here?

A

Imaging plate artifact; Cracks

47
Q

What does dust on an imaging plate appear as on a radiographic image?

A

Appears as focal radiopacities overlyin ghte soft tissues

(not really an issue with CR)

48
Q

Why is having dust on the imaging plate an issue?

A

It can mimic calcifaction or foreign bodies embedded in the soft tissue

49
Q

What is the proper substance to use to clean the imaging plates?

A

Ethyl alcohol

(paper towel and gause shouldnt be used because they can leave fibers on plate)

50
Q

T/F

Once weekly cleaning of the imaging plate is advisable

A

True

51
Q

What artifact is seen here?

A

Imaging plate artifact (Dust)

52
Q

What is the SC35 frequency requirement for CR plate cleaning?

A

Monthly

53
Q

What is a roller artifact (disparity artifact) due to?

A

Due to malfunctioning of rollers in the digitizer

54
Q

T/F

With roller disparity artifacts, parts of the plate is scanned longer by the lser, causing a greater fraction of stroed energy to be released, resulting in brighter image output.

A

True

55
Q

What artifact is seen here?

A

Roller artifact (disparity artifact)

56
Q

What are the four types of roller artifacts?

A
  1. Disparity artifact
  2. Roller damage artifact
  3. Dust
  4. Slipping of rollers
57
Q

What is a roller damage artifact caused by? How does it appear on a radiograph?

A

-It is the damage of the imaging plate by the rollers
-Roller damage appears as radiopacities at different points along the plate in a line

58
Q

What artifact is seen here?

A

Roller Damage Artifact

59
Q

How does dust on the rollers appear in a radiographic image?

A

Appears as a hazy white line across the entire imaging plate

60
Q

What artifact is seen here?

A

Roller artifact: Dust

61
Q

What does slipping of the rollers result in?

A

Results in only part of the image being read.

62
Q

What artifact is the black arrow pointing to?

A

Roller artifact: Slipping of rollers

63
Q

What is the purpose of the light guide in a processer?

A

The light guide collects light emmitted from the beam deflector when it is scanned by the laser and is sent to the PMT for amplication.

64
Q

How does dirt on the light guide appear on a radiographic image?

A

Dirt over the light guide is seen as a linear radio dense line

(clearer than dust on the rollers)

65
Q

What artifact is the white arrow pointing to?

A

Dirt on the light guide

66
Q

What is the purpose of having lead foil on the back of the cassette?

A

Prevents scattered radiation

67
Q

What artifact is this describing?

Artifact is caused by cracks in lead foil in the back of the cassette

A

Cassette related artifact; cassette integrity

68
Q

How does a cassette related artifact (cassette integrity) appear on a radiograph?

A

Vertical linear radiolucent line over certain area of anatomy

69
Q

What artifact is the white arrow pointing to?

A

Cassette related artifact; cassette integrity

70
Q

What are the 3 types of patient related artifacts?

A
  1. Patient artifact
  2. Motion artifact
  3. Image compositing artifact
71
Q

What is patient artifact caused by?

A

Caused by items that can be either on or within the patient when a diagnostic procedure is performed.

Examples: Buttons, snaps, necklaces, hairpins, wet hair, thick hair (dreads), body piercing etc.

72
Q

What are three ways that motion artifact can be reduced?

A

Short exposure times, immobilization and proper patient instructions.

73
Q

What is another name for Image Compositing?

A

image stitching/image pasting.

74
Q

How is Image Compositing Artifact prevented?

A

Images are acquired by pivoting the x-ray tube at the location of the focal spot, angled to match the location of the detector for each exposure.

75
Q

What artifact is seen here?

A

Image Compositing Artifact

76
Q

What is this describing

The rapid acquisition of images resulting in latent signal from one exposure lingering into the readout of subsequent exposures, producing what appears to be an incomplete erasure of the previous image

A

Image lag

77
Q

Read over detector image lag-Slideshow

A

Important information-Will most likely be tested on this

78
Q

What artifact is shown here?

A

Detector Image Lag

79
Q

When do the chances of detector image lag increase?

A

If you are scanning lower contrast areas just prior to exposing areas of high contrast

80
Q

What are the 3 ways in which image lag (ghosting) can be prevented?

A
  1. Reduction of exposure level or collimating
  2. Increasing the time interval between exposures or decrease the amount of time between readout events (2nd not an option for us to control)
  3. Allowing time for signal decay before the next patient examination begins
81
Q

Why is sheilding on the back of the detector often comprimised? What can this result in?

A

To minimize weight of the detector. Can result in backscatter artifacts.

82
Q

When is back scatter most commonly seen?

A

When using a high exposure on large patients

83
Q

What artifact is seen here?

A

Back scatter-Seeing electronics in the detector

84
Q

What is the temporary fix for backscatter?

A

Reduce overexposure, collimate tightly

85
Q

What is the long term fix for back scatter?

A

More shielding attached to the back of the detector by vendor

86
Q

When does the speckle artifact occur?

A

Occurs after detector drop

87
Q

How is speckle artifact resolved?

A

By re-calibration

88
Q

How can you tell the difference between speckle artifact and dust on the IR?

A

Dust cannot be seen on the IR, and speckle artifact is only seen with IRs silly

89
Q

What artifact is seen here?

A

Speckle artifact

Imaging Applications and Quality (9 decks)

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