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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
horizontal beam angulation for molars and PM
dif angulations due to the curve of the arch, beam must be directed perpindicular to B/L surfaces
26
setting the horizontal angle
The Central Ray should be directed between the interproximal contacts of interest
27
central ray and sensor
must be perpindicular
28
Incorrect Horizontal Angulation * Cause?
* Cause: Central ray is not projected perpendicular to sensor * creates overlapped contacts
29
Mesial to distal or distal to mesial HA
Mesial to distal
30
Mesial to distal or distal to mesial HA
distal to mesial
31
BEAM VERTICAL ANGULATION ISSUES
* Foreshortened images * Elongated images
32
Foreshortened images – Cause? – Beam is perpendicular to?
– Cause: Excessive vertical angulation – Beam is perpendicular to the sensor but object not parallel to receptor
33
error?
foreshortening
34
error?
foreshortening
35
cusp heights and foreshortening
foreshortening can cause greater discrepencies btwn functional and non functional cusp height
36
error?
foreshortening
37
Elongated images – Cause? – Beam is perpendicular to?
– Cause: Insufficient vertical angulation – Beam is perpendicular to the tooth/teeth
38
error?
elongation
39
PID ALIGNMENT PROBLEMS
cone cuts with/without sensor holder
40
Cone cuts with sensor holder Cause?
Cause: PID not properly aligned with the sensor holding device from; - incorrect XCP Assembly - poor alignment of PID with XCP
41
error?
cone cut
42
error?
cone cut
43
Cone cuts without sensor holder – Cause?
– Cause: PID not directed at center of film
44
can cone cuts occur with or without sensor holder?
can occur in both cases
45
what else could cause a cone cut?
pt movement
46
error?.
cone cut
47
thyroid collar in images
possible if near receptor, would ressemble cone cut but you may see stitching of collar
48
error?
thyroid collar
49
Sensor Wire Superimposition may occur with
CCD/CMOS
50
error?
sensor wire superimposition
51
II. EXPOSURE PROBLEMS
1. Overexposed 2. Underexposed 3. No exposure 4. Sensor wire superimposition 5. Post exposure
52
how can no exposure, underexposre and over exposure be less dramatic now days
less dramatic because post-exposure image processing by the software immediately corrects large exposure discrepancies.
53
error?
oerexposure
54
errors leading to overexposure
a. Increased time (MAIN) b. Increased mA c. Increased kV or any combo of these
55
error?
overexposure
56
error?
underexposure
57
underexpsoure causes
– Cause: Insufficient exposure time, kVp, mA, or any combination of these; – in SoD Radiology Clinic, time is the main cause
58
additional cause of underexposure, due to that law?
Excessive tube-receptor distance; related to inverse square law
59
exposure problems and sensor wire
can superimpose image if not kept out of way
60
errors in post expsoure image processing
Faulty program software image settings: calibration files and +gain, gamma, -gain
61
what is happening here?
software missed a row of pixels, must be recalibrated
62
what has happened here?
faulty software:+ gain, gamma, - gain
63
III. Patient Preparation PROBLEMS
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
error?
eyeglasses
65
RPD left in pts mouth
66
gum: right candy: left
67
mose peircing
68
not remving jewelry may?
mask disease
69
Sensor Bending – Cause:
Sensor is bending toward source because of impingement against palate
70
sensor bending
71
sensor bending
72
8. Sensor Creasing/scratch marks – Cause:
– Cause: damage to storage phosphors so there is no signal to the area with damaged pixels
73
sensor creasing
74
sensor creasing
75
are sensor creases permanent?
yes
76
Double exposure – Cause? – Not possible with?
– Cause: Sensor is accidentally exposed twice – Not possible with contemporary CMOS capture software
77
double exposure
78
double exposure
79
Reversed Placement – Cause:
– Cause: Sensor is placed back to front in sensor holder creates reverse image
80
can there be reversed placement with CMOS
– Not possible with contemporary CMOS sensors because of poor unstable fit in biteblock
81
errors pertaining only to PSPP/film
8. Sensor bending 9. Sensor Creasing 10. Double exposure 11. Reversed placement

oral radiology (22 decks)

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