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oral radiology > Sensor Placement and Beam Positioning Problems > Flashcards

Sensor Placement and Beam Positioning Problems Flashcards

1
Q

Sensor Placement and Beam
Positioning Problems related to:

A
  1. image receptor
  2. shadow casting principles
  3. human element
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2
Q

Types of Sensor Placement and Beam
Positioning Problems

A

I. Miscellaneous Technique PROBLEMS
II. Exposure PROBLEMS
III. Patient Preparation PROBLEMS

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3
Q

certain ones for Pspp?

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 placement
  8. Sensor bending
  9. Sensor Creasing
  10. Double exposure
  11. Reversed placement
    #8 - #11 relate to PSP and film images
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4
Q

Phalangioma

A

Cause: Patient’s finger positioned in front of the sensor

appears on image

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5
Q

error?

A

phalangioma

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6
Q

movement problem

A

– Cause: Patient or x-ray tube head moves during exposure creating larger pnuembra (fuzzy image)

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7
Q

cause?

A

pt or tube movement

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8
Q

what happened?

A

movement

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9
Q

sensor placement with solid state sensors?

A

Sensor placement is MORE critical with solid-state sensors
There is a smaller active image capture area than with film/PSPP

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10
Q

error?

A

poor sensor placement

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11
Q

Maxillary Premolar PA
* Receptor parallels?
* Anterior edge of receptor includes?
* Horizontal angle directed through which contacts?

A
  • Receptor parallels B and Li planes of premolars
  • Receptor parallels long axis of premolars
  • Anterior edge of receptor includes distal ½ of canine, the premolars and some of molars
  • Horizontal angle directed through distal of canine/premolar, premolar/premolar and the 2nd premolar/ molar contacts
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12
Q

how should BW contacts be ?

A

OPEN

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13
Q

Maxillary Molar PA
* Receptor parallels?
* Anterior edge of receptor includes?
* Horizontal angle directed through what contacts?

A
  • Receptor parallels B and Li planes of molars
  • Receptor parallels long axis of molars
  • Anterior edge of receptor includes distal ½ of 2nd
    premolar and as much of the molars as possible
  • Horizontal angle directed through distal of 2nd premolar/1st molar and the intermolar contacts
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14
Q

max canine PA must have what centered?

A

must have canine centered

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15
Q

premolar BW
* Receptor parallels?
* Anterior edge of receptor includes?
* Horizontal angle directed through which contacts?

A
  • Receptor parallels B and Li planes of premolars
  • Receptor parallels long axis of premolars
  • Anterior edge of receptor includes distal ½ of canine, the premolars and some of molars
  • Horizontal angle directed through distal of canine/premolar, premolars and the 2nd premolar/ 1st molar contacts
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16
Q

cotton rolls and incorrect placement

A

use of cotton roll whenpts bite on sensor holder, can releive pain but also displace sensor
roll must be placed against arch not being imaged

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17
Q

proper cotton roll placement

A

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

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18
Q

absence of apical image and dropped sensor corners can be due to?

A

improper sensor placement

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19
Q

Absence of apical structures
– Cause?
– Bite block?

A

– Cause: Sensor not positioned over the apical area in the mouth
– Bite block not against occlusal/incisal edge; OR patient not biting down, either can be due to pt pain

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20
Q

error?

A

sensor placement- apical strucutures missing

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21
Q

error?

A

absent apical structures

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22
Q

tipping/dropped film corner cause

A

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

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23
Q

error?

A

tipping

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24
Q

error?

A

tipping

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25
Q

horizontal beam angulation for molars and PM

A

dif angulations due to the curve of the arch, beam must be directed perpindicular to B/L surfaces

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26
Q

setting the horizontal angle

A

The Central Ray should
be directed between
the interproximal
contacts of interest

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27
Q

central ray and sensor

A

must be perpindicular

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28
Q

Incorrect Horizontal
Angulation
* Cause?

A
  • Cause: Central ray is not projected perpendicular to sensor
  • creates overlapped contacts
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29
Q

Mesial to distal or distal to mesial HA

A

Mesial to distal

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30
Q

Mesial to distal or distal to mesial HA

A

distal to mesial

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31
Q

BEAM VERTICAL ANGULATION ISSUES

A
  • Foreshortened images
  • Elongated images
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32
Q

Foreshortened images
– Cause?
– Beam is perpendicular to?

A

– Cause: Excessive vertical angulation
– Beam is perpendicular to the sensor but object not parallel to receptor

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33
Q

error?

A

foreshortening

34
Q

error?

A

foreshortening

35
Q

cusp heights and foreshortening

A

foreshortening can cause greater discrepencies btwn functional and non functional cusp height

36
Q

error?

A

foreshortening

37
Q

Elongated images
– Cause?
– Beam is perpendicular to?

A

– Cause: Insufficient vertical angulation
– Beam is perpendicular to the tooth/teeth

38
Q

error?

A

elongation

39
Q

PID ALIGNMENT PROBLEMS

A

cone cuts with/without sensor holder

40
Q

Cone cuts with sensor holder
Cause?

A

Cause: PID not properly aligned with the sensor holding device from;
- incorrect XCP Assembly
- poor alignment of PID with XCP

41
Q

error?

A

cone cut

42
Q

error?

A

cone cut

43
Q

Cone cuts without sensor holder
– Cause?

A

– Cause: PID not directed at center of film

44
Q

can cone cuts occur with or without sensor holder?

A

can occur in both cases

45
Q

what else could cause a cone cut?

A

pt movement

46
Q

error?.

A

cone cut

47
Q

thyroid collar in images

A

possible if near receptor, would ressemble cone cut but you may see stitching of collar

48
Q

error?

A

thyroid collar

49
Q

Sensor Wire
Superimposition may occur with

A

CCD/CMOS

50
Q

error?

A

sensor wire superimposition

51
Q

II. EXPOSURE PROBLEMS

A
  1. Overexposed
  2. Underexposed
  3. No exposure
  4. Sensor wire superimposition
  5. Post exposure
52
Q

how can no exposure, underexposre and over exposure be less dramatic now days

A

less dramatic because post-exposure image processing by the software immediately corrects large exposure discrepancies.

53
Q

error?

A

oerexposure

54
Q

errors leading to overexposure

A

a. Increased time (MAIN)
b. Increased mA
c. Increased kV
or any combo of these

55
Q

error?

A

overexposure

56
Q

error?

A

underexposure

57
Q

underexpsoure causes

A

– Cause: Insufficient exposure time, kVp, mA, or any combination of
these;
– in SoD Radiology Clinic, time is the main cause

58
Q

additional cause of underexposure, due to that law?

A

Excessive tube-receptor distance; related to inverse square law

59
Q

exposure problems and sensor wire

A

can superimpose image if not kept out of way

60
Q

errors in post expsoure image processing

A

Faulty program software image settings: calibration files and +gain, gamma, -gain

61
Q

what is happening here?

A

software missed a row of pixels, must be recalibrated

62
Q

what has happened here?

A

faulty software:+ gain, gamma, - gain

63
Q

III. Patient Preparation PROBLEMS

A

Failure to remove a non-fixed item from patient that may be in path of the primary x-ray beam

examples: gum, candy, piercings,
eyeglass frames, et cetera

64
Q

error?

A

eyeglasses

65
Q
A

RPD left in pts mouth

66
Q
A

gum: right
candy: left

67
Q
A

mose peircing

68
Q

not remving jewelry may?

A

mask disease

69
Q

Sensor Bending
– Cause:

A

Sensor is bending toward source because of impingement against palate

70
Q
A

sensor bending

71
Q
A

sensor bending

72
Q
  1. Sensor Creasing/scratch marks
    – Cause:
A

– Cause: damage to storage phosphors so there is no signal to the area with damaged pixels

73
Q
A

sensor creasing

74
Q
A

sensor creasing

75
Q

are sensor creases permanent?

A

yes

76
Q

Double exposure
– Cause?
– Not possible with?

A

– Cause: Sensor is accidentally exposed twice
– Not possible with contemporary CMOS capture software

77
Q
A

double exposure

78
Q
A

double exposure

79
Q

Reversed Placement
– Cause:

A

– Cause: Sensor is placed back to front in sensor holder
creates reverse image

80
Q

can there be reversed placement with CMOS

A

– Not possible with contemporary CMOS sensors because of poor unstable fit in biteblock

81
Q

errors pertaining only to PSPP/film

A
  1. Sensor bending
  2. Sensor Creasing
  3. Double exposure
  4. Reversed placement

oral radiology (22 decks)

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