PSPP Sensor Placement and Beam Positioning Problems Flashcards
Sensor placement and beam positioning problems can be caused by…
- image receptor
a. Film
b. Photostimulable Phosphor Plate (i.e., PSPP)
c. Charge Coupling Device (i.e., CCD)
d. Complimentary Metal Oxide Semiconductor (i.e., CMOS) - shadow casting principles
a. beam angulation
b. receptor placement - The “Human” element
a. clinician
b. patient
What are the miscellaneous technique problems?
- Phalangioma
- Movement
- Sensor placement
- Beam angulation - Horizontal
- Beam angulation - Vertical
- PID/BID alignment
- Sensor wire placement
- Sensor bending
- Sensor Creasing
- Double exposure
- Reversed placement
(8-11 PSP and film only)
What is phalangioma?
Patient’s finger positioned in front of the sensor
What is wrong with this image?
phalangioma
What is wrong with this image?
phalangioma
What is the problem with movement during x-rays?
Patient or x-ray tube head moves
during exposure
What is wrong with this image?
movement
Sensor placement is _____ critical with solid-state sensors
MORE
Why is sensor placement more critical with solid-state sensors?
smaller active image capture area
Where do you place the receptor for a maxillary premolar PA?
- 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
Where do you place the receptor for a maxillary molar PA?
- 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
What type of x-ray is this?
maxillary molar PA
What type of x-ray is this?
maxillary premolar PA
Where do you place the receptor for a premolar bitewing?
- Anterior edge of receptor includes mesial 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
What type of x-ray is this?
premolar bitewing
Where do you put the cotton roll for x-rays?
Between biteblock and opposing teeth
T/F: put the cotton roll between biteblock and imaged teeth
False!
- Between biteblock and opposing teeth
What are ways you can have incorrect placement?
- Absence of apical structures
- Dropped sensor corner
What can cause an absence of apical structures from an x-ray?
- Sensor not positioned over the apical area in the mouth
- Bite block not against occlusal/incisal edge; OR patient not biting down
What is wrong with this image?
- Incorrect Sensor Placement
- Absence of apical structures
What is the cause of the “tipping”/dropped film corner?
Sensor not placed parallel with the occlusal / incisal surface of teeth
How do you set the horizontal angle?
The Central Ray should be directed between the interproximal contacts of interest
Central ray has to be projected _______________ to sensor
perpendicular
Is this incorrect horizontal angulation mesial to distal or distal to mesial?
Mesial to distal
Is this incorrect horizontal angulation mesial to distal or distal to mesial?
distal to mesial
What can issues with beam angulation vertical cause?
- Foreshortened images
- Elongated images
What is the cause of foreshortened images?
- Excessive vertical angulation
- Beam is perpendicular to the sensor (but object not parallel to receptor?- haley)
What is the issue with this image?
foreshortened image
What is the issue with this image?
foreshortened image
When you foreshorten an image with smaller active area what happens?
parts of the image are missed
What is wrong with the image on right compared to the “good” one of the left
foreshortened image
With a smaller active image capture area AND long roots _____________ is encouraged
foreshortening
What causes elongated images?
- Insufficient vertical angulation
– Beam is perpendicular to the tooth/teeth
What is the issue with this image?
elongated images
What is the issue with this image?
elongated images
What does BID/PID alignment problems cause?
- Cone cuts
– With sensor holder
– Without sensor holder
What is BID/PID?
beam indicating device
position indicator device
What is the cause of cone cuts with sensor holder?
PID not properly aligned with the sensor holding device from
- incorrect XCP Assembly
- poor alignment of PID with XCP
What is the issue with this image?
PID ALIGNMENT PROBLEMS
What is the issue with this image?
PID ALIGNMENT PROBLEMS
What causes cone cuts without sensor holder (XCP)?
PID not directed at center of film
What is wrong with this image?
sensor wire
What is wrong with this image?
sensor wire
What are exposure problems?
- Overexposed
- Underexposed
- No exposure
- Sensor wire superimposition
- Post exposure
Why are overexposed and underexposed images not as big of a deal?
post-exposure image processing by the software immediately corrects large exposure discrepancies
What causes overexposed images?
________ time
________ mA
________ kV
increased time
increased mA
increased kV
An overexposed image has ____ density
high
What causes overexposed images?
Excessive exposure to x-radiation from excess time, kVp, mA, or any combination of these
What is wrong with this image?
overexposed
What is wrong with this image?
overexposed
What is wrong with this image?
underexposed
What causes an underexposed image?
Insufficient exposure time, kVp, mA, or any combination of these
What causes underexposed images?
________ time
________ mA
________ kVp
insufficient time
insufficient mA
insufficient kVp
Excessive tube-receptor distance is related to…
inverse square law
What is post exposure image processing issues?
- Faulty program software image settings: calibration files
+ gain, gamma, - gain
What is gain for image processing?
Adjusts the bright tones and brings more information into the highlights of an image.
What is gamma correction for image processing?
Adjusts the midtones of an image by adjusting each pixel value in an image. It is usually performed automatically on a PC monitor, but the precision is adjustable
What is wrong with this image?
Post Exposure Image Processing
What are examples of failure to remove a non-fixed item from patient that may be in path of the primary x-ray beam?
gum, candy, piercings, eyeglass frames, et cetera
What causes sensor bending?
Sensor is bending toward source because of impingement against palate
What causes sensor creasing/scratch marks?
damage to storage phosphors so there is no signal to the area with damaged pixels
What is wrong with this image?
sensor creasing/scratch marks
What is wrong with this image?
sensor bending
What is a double exposure?
- Sensor is accidentally exposed
twice
– Not possible with contemporary CMOS capture software
What is wrong with this image?
double exposure
What is wrong with this image?
double exposure
What is the cause of reversed placement?
Sensor is placed back to front in sensor holder
– Unlikely with contemporary CMOS sensors because of poor unstable fit in biteblock
What is wrong with this image?
Reversed Placement
