Sensor Placement Beam Align Flashcards
MISCELLANEOUS TECHNIQUE
PROBLEMS
(11)
- Phalangioma
- Movement
- Sensor placement
- Beam angulation - Horizontal
- Beam angulation - Vertical
- PID/BID alignment
- Sensor wire placement
- Sensor bending
- Sensor Creasing
- Double exposure
- Reversed placement
- Sensor bending
- Sensor Creasing
- Double exposure
- Reversed placement
#8 - #11 relate to (2) images
PSP and film
- Phalangioma
– Cause:
Patient’s finger positioned in front of the sensor
- Movement
– Cause:
Patient or x-
ray tube head moves
during exposure
Sensor placement is MORE critical with
solid-state sensors
There is a smaller active image capture area
Maxillary Premolar PA
(4)
- 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
Maxillary Molar PA
(4)
- 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
Premolar Bitewing (BW)
(4)
- Receptor parallels B and Li planes of premolars
- Receptor parallels long axis of premolars
- 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
Incorrect Placement
*Cotton roll placement
Between biteblock and opposing teeth;
NOT between biteblock and imaged teeth
Incorrect Sensor Placement
Absence of apical structures
(2)
– Cause: Sensor not positioned over the apical
area in the mouth
– Bite block not against occlusal/incisal edge;
OR patient not biting down
ncorrect Sensor Placement
“Tipping”
i.e., Dropped film corner
– Cause:
Sensor not
placed parallel with the
occlusal / incisal
surface of teeth
Set the Horizontal Angle
* The Central Ray should
be directed
between
the interproximal
contacts of interest
- Horizontal Angulation
* Central ray has to
be projected
perpendicular to
sensor
Incorrect Horizontal
Angulation
* Cause:
Central ray
is not projected
perpendicular to
sensor
Incorrect Vertical Angulation
Foreshortened images
(2)
– Cause: Excessive
vertical angulation
– Beam is
perpendicular to the
sensor
Incorrect Vertical Angulation
Foreshortened images
– With smaller active area,
parts of image are missed
Incorrect Vertical Angulation
Elongated images
(2)
– Cause: Insufficient
vertical angulation
– Beam is
perpendicular to the
tooth/teeth
- PID ALIGNMENT
PROBLEMS
Cone cuts with sensor holder
– Cause:
PID not properly aligned
with the sensor holding device
from;
- incorrect XCP Assembly
- poor alignment of PID with XCP
- PID ALIGNMENT PROBLEMS
* Cone cuts without
sensor holder
– Cause:
PID not
directed at center of
film
II. EXPOSURE PROBLEMS
(5)
- Overexposed
- Underexposed
- No exposure
- Sensor wire superimposition
- Post exposure
- Overexposed
- Underexposed
- No exposure
- Sensor wire superimposition
- Post exposure
PROBLEMS 1, 2, & 3 are less dramatic
because
post-exposure image processing by
the software immediately corrects large
exposure discrepancies.
HIGH DENSITY Image
1. Overexposed
(3)
a. Increased time
b. Increased mA
c. Increased kV
EXPOSURE PROBLEMS
Overexposed images
– Cause:
Excessive
exposure to x-
radiation from
excess time, kVp,
mA, or any
combination of
these
TIME AND EXPOSURE FACTOR
PROBLEMS
* Underexposed image
(2)
– Cause: Insufficient
exposure time, kVp, mA,
or any combination of
these;
– in SoD Radiology Clinic,
time is the main cause
Underexposed
(3)
- Insufficient time
- Insufficient mA
- Insufficient kVp
- Excessive tube-receptor distance;
related to
inverse square law
I. EXPOSURE PROBLEMS
5. Post Exposure Image Processing
(2)
Faulty program software image settings: calibration files
Faulty program software image settings: + gain, gamma, - gain
III. Patient Preparation PROBLEMS
(2)
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
I. MISCELLANEOUS TECHNIQUE
PROBLEMS
8. Sensor Bending
– Cause:
Sensor is bending
toward source because of
impingement against palate
I. MISCELLANEOUS TECHNIQUE
PROBLEMS
8. Sensor Creasing/scratch marks
– Cause:
damage to storage
phosphors so there is no signal to
the area with damaged pixels
. MISCELLANEOUS TECHNIQUE
PROBLEMS
10. Double exposure
(2)
– Cause: Sensor is
accidentally exposed
twice
– Not possible with
contemporary CMOS
capture software
I. MISCELLANEOUS TECHNIQUE
PROBLEMS
11. Reversed Placement
– Cause:
Sensor is placed
back to front in sensor
holder
. MISCELLANEOUS TECHNIQUE
PROBLEMS
11. Reversed Placement
– Not possible with contemporary CMOS sensors
because of
poor unstable fit in biteblock
