Sensor Placement and Beam Positioning Problems Flashcards
Sensor Placement and Beam
Positioning Problems related to:
- image receptor
- shadow casting principles
- human element
Types of Sensor Placement and Beam
Positioning Problems
I. Miscellaneous Technique PROBLEMS
II. Exposure PROBLEMS
III. Patient Preparation PROBLEMS
certain ones for Pspp?
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 relate to PSP and film images
Phalangioma
Cause: Patient’s finger positioned in front of the sensor
appears on image
error?
phalangioma
movement problem
– Cause: Patient or x-ray tube head moves during exposure creating larger pnuembra (fuzzy image)
cause?
pt or tube movement
what happened?
movement
sensor placement with solid state sensors?
Sensor placement is MORE critical with solid-state sensors
There is a smaller active image capture area than with film/PSPP
error?
poor sensor placement
Maxillary Premolar PA
* Receptor parallels?
* Anterior edge of receptor includes?
* Horizontal angle directed through which contacts?
- 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
how should BW contacts be ?
OPEN
Maxillary Molar PA
* Receptor parallels?
* Anterior edge of receptor includes?
* Horizontal angle directed through what contacts?
- 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
max canine PA must have what centered?
must have canine centered
premolar BW
* Receptor parallels?
* Anterior edge of receptor includes?
* Horizontal angle directed through which contacts?
- 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
cotton rolls and incorrect placement
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
proper cotton roll placement
Between biteblock and opposing teeth;
NOT between biteblock and imaged teeth
absence of apical image and dropped sensor corners can be due to?
improper sensor placement
Absence of apical structures
– Cause?
– Bite block?
– 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
error?
sensor placement- apical strucutures missing
error?
absent apical structures
tipping/dropped film corner cause
Cause: Sensor not placed parallel with the occlusal / incisal surface of teeth
error?
tipping
error?
tipping
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
setting the horizontal angle
The Central Ray should
be directed between
the interproximal
contacts of interest
central ray and sensor
must be perpindicular
Incorrect Horizontal
Angulation
* Cause?
- Cause: Central ray is not projected perpendicular to sensor
- creates overlapped contacts
Mesial to distal or distal to mesial HA
Mesial to distal
Mesial to distal or distal to mesial HA
distal to mesial
BEAM VERTICAL ANGULATION ISSUES
- Foreshortened images
- Elongated images
Foreshortened images
– Cause?
– Beam is perpendicular to?
– Cause: Excessive vertical angulation
– Beam is perpendicular to the sensor but object not parallel to receptor
error?
foreshortening
error?
foreshortening
cusp heights and foreshortening
foreshortening can cause greater discrepencies btwn functional and non functional cusp height
error?
foreshortening
Elongated images
– Cause?
– Beam is perpendicular to?
– Cause: Insufficient vertical angulation
– Beam is perpendicular to the tooth/teeth
error?
elongation
PID ALIGNMENT PROBLEMS
cone cuts with/without sensor holder
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
error?
cone cut
error?
cone cut
Cone cuts without sensor holder
– Cause?
– Cause: PID not directed at center of film
can cone cuts occur with or without sensor holder?
can occur in both cases
what else could cause a cone cut?
pt movement
error?.
cone cut
thyroid collar in images
possible if near receptor, would ressemble cone cut but you may see stitching of collar
error?
thyroid collar
Sensor Wire
Superimposition may occur with
CCD/CMOS
error?
sensor wire superimposition
II. EXPOSURE PROBLEMS
- Overexposed
- Underexposed
- No exposure
- Sensor wire superimposition
- Post exposure
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.
error?
oerexposure
errors leading to overexposure
a. Increased time (MAIN)
b. Increased mA
c. Increased kV
or any combo of these
error?
overexposure
error?
underexposure
underexpsoure causes
– Cause: Insufficient exposure time, kVp, mA, or any combination of
these;
– in SoD Radiology Clinic, time is the main cause
additional cause of underexposure, due to that law?
Excessive tube-receptor distance; related to inverse square law
exposure problems and sensor wire
can superimpose image if not kept out of way
errors in post expsoure image processing
Faulty program software image settings: calibration files and +gain, gamma, -gain
what is happening here?
software missed a row of pixels, must be recalibrated
what has happened here?
faulty software:+ gain, gamma, - gain
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
error?
eyeglasses
RPD left in pts mouth
gum: right
candy: left
mose peircing
not remving jewelry may?
mask disease
Sensor Bending
– Cause:
Sensor is bending toward source because of impingement against palate
sensor bending
sensor bending
- Sensor Creasing/scratch marks
– Cause:
– Cause: damage to storage phosphors so there is no signal to the area with damaged pixels
sensor creasing
sensor creasing
are sensor creases permanent?
yes
Double exposure
– Cause?
– Not possible with?
– Cause: Sensor is accidentally exposed twice
– Not possible with contemporary CMOS capture software
double exposure
double exposure
Reversed Placement
– Cause:
– Cause: Sensor is placed back to front in sensor holder
creates reverse image
can there be reversed placement with CMOS
– Not possible with contemporary CMOS sensors because of poor unstable fit in biteblock
errors pertaining only to PSPP/film
- Sensor bending
- Sensor Creasing
- Double exposure
- Reversed placement