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Oral Radiology > Sensor and Beam Technique Erros > Flashcards

Sensor and Beam Technique Erros Flashcards

1
Q

what are the sensor placement and beam positioning problems

A
  • image receptor
  • shadow casting princples
  • the human element
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2
Q

what are the 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 the shadow casting principles

A
  • beam angulation
  • receptor placement
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4
Q

what are the sources of problems with sensor placment abd beam positioning

A
  • technique problems
  • exposure problems
  • patient preparation problems
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5
Q

what are the technique problems

A
  • phalangiona
  • movement
  • sensor placement
  • beam angulation - horizontal
  • beam angulation - vertical
  • PID/BID alignemtn
  • sensor wire placement
  • sensor bending
  • sensor creasing
  • double exposure
  • reversed placement
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6
Q

what technique problems are related to PSP and film images

A
  • sensor bending
  • sensor creasing
  • double exposure
  • reversed placement
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7
Q

what is phalangioma

A

patients finger positioned in front of the sensor

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8
Q

what is the cause of movement

A

patient or x ray tube head moves during exposure

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9
Q

sensor placment is more critical with what type of sensors and why

A

solid state because there is a smaller active image capture area

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10
Q

describe the maxillary premolar PA

A
  • receptor parallels B and Li planes of premolars
  • receptor parallels long axis of premolars
  • anterior edge of receptor includes distal 1/2 canine, the premolars and some molars
  • horizontal angle directed through distal of canine/premolar, premolar/premolar and the 2nd premolar/molar contacts
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11
Q

where do you place the receptor for the lateral maxillary

A

lateral centered with open mesial contact

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12
Q

where do you place the receptor in canine premolar shot

A

canine 1st premolar centered with open contact

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13
Q

where do you place the receptor in the maxillary premolar shot

A

anterior receptor edge to middle of canine

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14
Q

where do you place the receptor in maxillary molar shot

A

anterior receptor edge to middle of second premolar

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15
Q

where do you place receptor for anterior bitewing

A

0 anteiror plate edge to middle of most anterior canine
- receptor must be parallel with teeth of interest

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16
Q

where do you palce receptro in posteior BW

A
  • vertical bitewing anterior receptor edge to mesial of mandibular first molar
  • receptor must be parallel with teeth of interes
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17
Q

describe the maxillary molar PA shot

A
  • receptor parallels B and Li planes of molar
  • receptor parallels long axis of molars
  • anterior edge of receptor includes distal 1/2 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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18
Q

describe the premolar BW

A
  • receptor parallels B and Li planes of premolars
  • receptor parallels long axis of premolars
  • anterior edge of receptor includes distal 1/2 of canine, the premolars and some of the molars
  • horizontal angle directed through the distal of canine/premolar, premolars and the 2nd premolar/1st molar contacts
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19
Q

where is the cotton roll placed

A

between biteblock and opposing teeth NOT between biteblock and imaged teeth

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20
Q

what would tell you you have incorrect placeemnt

A
  • absence of apical structures
  • dropped sensor corner
21
Q

what is the cause of absence of apical structures

A

sensor not positioned over the apical area in the mouth
- bite block not against occlusal/incisal edge; OR patient not biting down

22
Q

what is dropped film corner also called

A

tipping

23
Q

what is the cause of tipping/ dropped film corner

A

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

24
Q

what should the central ray be for the correct horizontal angle

A
  • should be directed between the interproximal contacts of interest
25
Q

for correct horizontal angulation the central ray has to be projected perpendicular to:

A

sensor

26
Q

what is the cause of incorrect horizontal angulation

A

central ray is not projected perpendicular to sensor

27
Q

what determines the correctness of beam angulation in horizontal direction

A
  • anterior and posterior bitewing placement
28
Q

what would be the issues with incorrect vertical angulation

A
  • foreshortened images
  • elongated images
29
Q

what is the cause of foreshortened images

A
  • excessive vertical angulation
  • beam is perpendicular to the sensor
30
Q

what is the cause of elongated imagees

A
  • insufficient vertical angulation
  • beam is perpendicular to the tooth/teeth
31
Q

what are the PID alignment problems

A

cone cuts
- with sensor holder
-without sensor holder

32
Q

what is the cause of cone cuts with sensor holder

A
  • PID is not properly aligned with the sensor holding device from
  • incorrect XCP assembly
    -poor alignment of PID with XCP
33
Q

what is the cause of cone cuts without sensor holder

A
  • PID not directed at center of film
34
Q

what are the exposure problems

A
  • overexposed
  • underexposed
  • no exposure
  • sensor wire superimposition
  • post exposure
35
Q

which exposure problems are less dramatic and why

A
  • overexposed, underexposed and no exposure
  • post- exposure image processing by software immediately corrects large exposure discrepancies
36
Q

what is overexposure caused by

A
  • excessive exposure to x-radiation from:
  • increased time
  • increased mA
  • increased kV
37
Q

what is the cause of underexposed images

A
  • insufficient exposure time, kVp, mA
38
Q

what is the main cause of underexposed image in SOD clinic

A

time

39
Q

for post exposure image processing what are the faulty program software image settings called

A

calibration files
+ gain
gamma
and - gain

40
Q

what are patient preparation problesm

A

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

41
Q

what are the examples of patient preparation problems

A

-gum
- candy
- piercings: face piercing
- eyeglass frames
-RPD

42
Q

what does not removing jewelry risk:

A

masking disease

43
Q

what is the cause of sensor bending

A

sensor is bending toward source because of impingement against palate

44
Q

what is the cause of sensor creasing/scratch marks

A

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

45
Q

creases are:

A

permanent

46
Q

what is the cause of double exposure

A
  • PSP sensor is accidentally exposed twice
  • not possible with CMOS
47
Q

what is the cause of reversed placement

A

sensor is placed back to front in sensor holder

48
Q

why is reversed placement not possible with CMOS

A

because of poor unstable fit in biteblock

49
Q
A

Oral Radiology (26 decks)

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