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D2 Fall - Radiology > 9/24: Sensor Placement & Beam Positioning Problems > Flashcards

9/24: Sensor Placement & Beam Positioning Problems Flashcards

1
Q

What are 3 things that sensor placement and beam positioning problems can be related to?

A
  1. Image receptor
  2. shadow casting principles
  3. human error
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2
Q

What are examples of image receptors?

A

Film
Phosphor storage plate (PSP)
Charge coupling device (CCD)
Complementary Metal oxide semiconductor (CMOS)

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3
Q

What are examples of shadow casting principles?

A

Beam angulation
receptor placement

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4
Q

What are types of miscellaneous technique problems?

A
  1. Phalangioma
  2. Movement
  3. Sensor placement
  4. beam angulation - horizontal
  5. beam angulation - vertical
  6. PID/BID alignment
  7. Sensor wire superimposition
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5
Q

What is the cause of a phalangioma?

A

Patient’s finger positioned in front of the sensor

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6
Q

What is the cause of a movement problem?

A

Patient or x-ray tube head moves during exposure

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7
Q

How are movement problems detected?

A
  • sensor not where we put it
  • blurring of image
  • looks grainy
  • don’t have sharp outlines
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8
Q

What patients do movement problems occur in?

A

Children because can’t sit still

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9
Q

Sensor placement is _________ critical with solid-state sensors?

A

MORE

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10
Q

Why is sensor placement more critical with solid state?

A

Smaller active image capture area so there is less room for error

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11
Q

What should the receptor parallel in a maxillary premolar PA?

A
  • parallels buccal and lingual planes of premolars
  • long axis of premolars
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12
Q

What does the anterior edge of a maxillary premolar PA include?

A

distal 1/2 canine, the premolars, and some molars

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13
Q

What is the horizontal angle of a maxillary premolar PA?

A

Directed through distal of canine/premolar, premolar/premolar and the 2nd premolar/molar contacts

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14
Q

What does the receptor parallel in a maxillary molar PA?

A
  • buccal and lingual planes of molars
  • long axis of molars
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15
Q

What does the anterior edge of the receptor include in a maxillary molar PA?

A

Distal 1/2 of 2nd premolar and as much of the molar as possible

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16
Q

Where is the horizontal angle directed for a maxillary molar PA?

A

Distal of 2nd premolar/1st molar and the intermolar contacts

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17
Q

What does the receptor parallel in a premolar bitewing?

A
  • Buccal and lingual planes of premolars
  • long axis of premolars
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18
Q

What does the anterior edge of a premolar BW include?

A

Mesial 1/2 of canine, the premolars, and some molars

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19
Q

Where is the horizontal angle directed in a premolar BW?

A

Through distal of canine/premolar, premolars and the 2nd premolar/1st molar contacts

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20
Q

Where is the cotton roll placed to keep the sensor in the right place?

A

Between biteblock and opposing teeth; NOT between biteblock and imaged teeth

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21
Q

Should you place the cotton roll on the arch you are imaging?

A

NO! Placed on the opposing arch

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22
Q

What are 2 indications of incorrect placement?

A
  1. Absence of apical structures
  2. Dropped sensor corner
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23
Q

What is the cause of absence of apical structures?

A

Sensor not positioned over the apical area in the mouth

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24
Q

What are reasons for absence of apical structures in terms of inside the mouth?

A

Bite block not against occlusal/incisal edge; OR patient not biting down

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25
Q

What is tipping?

A

Dropped film corner

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26
Q

What is the cause of tipping?

A

Sensor not placed parallel with the occlusal/incisal surface of teeth

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27
Q

With what angulation are overlapped contacts reduced?

A

Correct horizontal angulation

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28
Q

When setting a horizontal angle, where should the central ray be directed?

A

Between the interproximal contacts of interest

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29
Q

Where should the central ray project in relation to the sensor?

A

Perpendicular

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30
Q

What is the cause of incorrect horizontal angulation?

A

Central ray is not projected perpendicular to sensor

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31
Q

Mesial to distal or distal to mesial?

A

Mesial to distal

KNOW HOW TO CHANGE ANGULATION TO DIRECT AND WHERE BEAM WAS COMING FROM

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32
Q

Mesial to distal or distal to mesial?

A

Distal to mesial

KNOW HOW TO CHANGE ANGULATION TO DIRECT AND WHERE BEAM WAS COMING FROM

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33
Q

Mesial to distal or distal to mesial?

A

Mesial to distal
KNOW HOW TO CHANGE ANGULATION TO DIRECT AND WHERE BEAM WAS COMING FROM

34
Q
A

Mesial to distal

KNOW HOW TO CHANGE ANGULATION TO DIRECT AND WHERE BEAM WAS COMING FROM

35
Q

What can vertical beam angulation problems result in?

A
  1. foreshortened image
  2. elongated images
36
Q

What is the cause of foreshortened image?

A

Excessive vertical angulation

37
Q

Where is the beam located to cause foreshortened image?

A

Perpendicular to the sensor

38
Q
A

Foreshortened image

39
Q

What occurs in foreshortened images that have a smaller active area?

A

Parts of image are missed

40
Q
A

Foreshortened images

41
Q
A

Foreshortened images
- crown is more than 1/3 the size of the tooth

42
Q

When is foreshortening encouraged?

A

With a smaller active image capture area AND long roots
- because otherwise we wont capture apices

43
Q

What is the cause of elongated images?

A

Insufficient vertical angulation

44
Q

Where is the beam located to create an elongated image?

A

Perpendicular to the tooth/teeth

45
Q
A

Elongated
because cusps are separating and stretching out

46
Q
A

elongation

47
Q

What are indications of BID/PID alignment problems?

A

Cone cuts
- with/without sensor holder

48
Q

What is the cause of cone cuts with sensor holder?

A

PID not properly aligned with the sensor holding device from
- incorrect SCP assembly
- poor alignment of PID with XCP

49
Q
A

Cone cut

50
Q
A

No cone cutting here because its a bite block

51
Q

What are the causes of cone cuts without sensor holder (XCP)?

A

PID not directed at center of film

52
Q
A

U thought cone cut?
NOPE!
This is a thyroid collar.
- can tell by reverse curvature and thread holes on the bottom right

53
Q
A

Sensor wire

54
Q

What are examples of exposure problems?

A
  1. Overexposed
  2. Under exposed
  3. No exposure (don’t press button at all)
  4. Wire superimposition
  5. post exposure
55
Q

What exposure problems are less dramatic and why?

A

Overexposed and underexposed because with software it can correct discrepencies

56
Q
A

Overexposed

57
Q

What are causes of overexposed images?

A

Excessive exposure to x-radiation from excess time, kVp, mA, or any combination

58
Q

What is the main cause of overexposed/underexposed images at SOD?

A

TIME because we can’t adjust kVp or mA

59
Q
A

Underexposed

60
Q

What is the cause of underexposure?

A

Insufficient exposure time, kVp, mA, or any combo

61
Q

What is excessive tube-receptor distance related to?

A

Inverse square law
- further away you move = less intense photo which can’t be fixed with software

62
Q
A

Post exposure image processeing

63
Q

What are post exposure image processing problems due to?

A

Faulty program software image settings: Calibration files

64
Q

How does ‘gain’ fix faulty images?

A

Adjusts the bright tones and brings more information into the highlights of the image

65
Q

How does ‘gamma correction’ fix faulty images?

A

Adjusts the midtones of an image by adjusting each pixel value in an image
- usually performed automatically on a PC monitor, but precision is adjustable

66
Q

What is the cause of patient preparation problems?

A

Failure to remove a non-fixed item from patient that may be i path of the primary xray beam

67
Q

What are examples of patient preparation problems

A

Gum, candy, piercings, eyeglass frames

68
Q
A

Eyeglass frame

69
Q
A

RPD left

70
Q
A

Gum or candy

71
Q

Not removing jewelery risks ____________

A

masking disease

72
Q

What is the cause of sensor bending?

A

Sensor is bending toward source because of impingement against palate

73
Q

What is the cause of sensor creasing?

A

Damage to storage phosphors so there is no signal to the area with damaged pixels

74
Q
A

Sensor creasing

75
Q

Creases are _____________

A

permanent

76
Q

What is the cause of double exposure?

A

PSP is accidentally exposed twice

77
Q

What is double exposure not possible with?

A

Contemporary CMOS capture software because of poor unstable fit in bite block

78
Q
A

Double exposure

79
Q

What is the cause of reversed placement?

A

Sensor is placed back to front in sensor holder

80
Q
A

Reversed placement

D2 Fall - Radiology (22 decks)

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