Sensor and Beam Technique Erros Flashcards
what are the sensor placement and beam positioning problems
- image receptor
- shadow casting princples
- the human element
what are the image receptors
- film
- phosphor storage plate (PSP)
- charge coupling device (CCD)
- Complementary metal oxide semiconductor (CMOS)
what are the shadow casting principles
- beam angulation
- receptor placement
what are the sources of problems with sensor placment abd beam positioning
- technique problems
- exposure problems
- patient preparation problems
what are the technique problems
- phalangiona
- movement
- sensor placement
- beam angulation - horizontal
- beam angulation - vertical
- PID/BID alignemtn
- sensor wire placement
- sensor bending
- sensor creasing
- double exposure
- reversed placement
what technique problems are related to PSP and film images
- sensor bending
- sensor creasing
- double exposure
- reversed placement
what is phalangioma
patients finger positioned in front of the sensor
what is the cause of movement
patient or x ray tube head moves during exposure
sensor placment is more critical with what type of sensors and why
solid state because there is a smaller active image capture area
describe the maxillary premolar PA
- 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
where do you place the receptor for the lateral maxillary
lateral centered with open mesial contact
where do you place the receptor in canine premolar shot
canine 1st premolar centered with open contact
where do you place the receptor in the maxillary premolar shot
anterior receptor edge to middle of canine
where do you place the receptor in maxillary molar shot
anterior receptor edge to middle of second premolar
where do you place receptor for anterior bitewing
0 anteiror plate edge to middle of most anterior canine
- receptor must be parallel with teeth of interest
where do you palce receptro in posteior BW
- vertical bitewing anterior receptor edge to mesial of mandibular first molar
- receptor must be parallel with teeth of interes
describe the maxillary molar PA shot
- 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
describe the premolar BW
- 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
where is the cotton roll placed
between biteblock and opposing teeth NOT between biteblock and imaged teeth
what would tell you you have incorrect placeemnt
- absence of apical structures
- dropped sensor corner
what is the cause of absence of apical structures
sensor not positioned over the apical area in the mouth
- bite block not against occlusal/incisal edge; OR patient not biting down
what is dropped film corner also called
tipping
what is the cause of tipping/ dropped film corner
sensor not placed parallel with the occlusal/incisal surface of teeth
what should the central ray be for the correct horizontal angle
- should be directed between the interproximal contacts of interest
for correct horizontal angulation the central ray has to be projected perpendicular to:
sensor
what is the cause of incorrect horizontal angulation
central ray is not projected perpendicular to sensor
what determines the correctness of beam angulation in horizontal direction
- anterior and posterior bitewing placement
what would be the issues with incorrect vertical angulation
- foreshortened images
- elongated images
what is the cause of foreshortened images
- excessive vertical angulation
- beam is perpendicular to the sensor
what is the cause of elongated imagees
- insufficient vertical angulation
- beam is perpendicular to the tooth/teeth
what are the PID alignment problems
cone cuts
- with sensor holder
-without sensor holder
what is the cause of cone cuts with sensor holder
- PID is not properly aligned with the sensor holding device from
- incorrect XCP assembly
-poor alignment of PID with XCP
what is the cause of cone cuts without sensor holder
- PID not directed at center of film
what are the exposure problems
- overexposed
- underexposed
- no exposure
- sensor wire superimposition
- post exposure
which exposure problems are less dramatic and why
- overexposed, underexposed and no exposure
- post- exposure image processing by software immediately corrects large exposure discrepancies
what is overexposure caused by
- excessive exposure to x-radiation from:
- increased time
- increased mA
- increased kV
what is the cause of underexposed images
- insufficient exposure time, kVp, mA
what is the main cause of underexposed image in SOD clinic
time
for post exposure image processing what are the faulty program software image settings called
calibration files
+ gain
gamma
and - gain
what are patient preparation problesm
failure to remove a non-fixed item from patient that may be in path of the primary x ray beam
what are the examples of patient preparation problems
-gum
- candy
- piercings: face piercing
- eyeglass frames
-RPD
what does not removing jewelry risk:
masking disease
what is the cause of sensor bending
sensor is bending toward source because of impingement against palate
what is the cause of sensor creasing/scratch marks
damage to storage phosphors so there is no signal to the area with damaged pixels
creases are:
permanent
what is the cause of double exposure
- PSP sensor is accidentally exposed twice
- not possible with CMOS
what is the cause of reversed placement
sensor is placed back to front in sensor holder
why is reversed placement not possible with CMOS
because of poor unstable fit in biteblock
