9/24: Sensor Placement & Beam Positioning Problems Flashcards
What are 3 things that sensor placement and beam positioning problems can be related to?
- Image receptor
- shadow casting principles
- human error
What are examples of image receptors?
Film
Phosphor storage plate (PSP)
Charge coupling device (CCD)
Complementary Metal oxide semiconductor (CMOS)
What are examples of shadow casting principles?
Beam angulation
receptor placement
What are types of miscellaneous technique problems?
- Phalangioma
- Movement
- Sensor placement
- beam angulation - horizontal
- beam angulation - vertical
- PID/BID alignment
- Sensor wire superimposition
What is the cause of a phalangioma?
Patient’s finger positioned in front of the sensor
What is the cause of a movement problem?
Patient or x-ray tube head moves during exposure
How are movement problems detected?
- sensor not where we put it
- blurring of image
- looks grainy
- don’t have sharp outlines
What patients do movement problems occur in?
Children because can’t sit still
Sensor placement is _________ critical with solid-state sensors?
MORE
Why is sensor placement more critical with solid state?
Smaller active image capture area so there is less room for error
What should the receptor parallel in a maxillary premolar PA?
- parallels buccal and lingual planes of premolars
- long axis of premolars
What does the anterior edge of a maxillary premolar PA include?
distal 1/2 canine, the premolars, and some molars
What is the horizontal angle of a maxillary premolar PA?
Directed through distal of canine/premolar, premolar/premolar and the 2nd premolar/molar contacts
What does the receptor parallel in a maxillary molar PA?
- buccal and lingual planes of molars
- long axis of molars
What does the anterior edge of the receptor include in a maxillary molar PA?
Distal 1/2 of 2nd premolar and as much of the molar as possible
Where is the horizontal angle directed for a maxillary molar PA?
Distal of 2nd premolar/1st molar and the intermolar contacts
What does the receptor parallel in a premolar bitewing?
- Buccal and lingual planes of premolars
- long axis of premolars
What does the anterior edge of a premolar BW include?
Mesial 1/2 of canine, the premolars, and some molars
Where is the horizontal angle directed in a premolar BW?
Through distal of canine/premolar, premolars and the 2nd premolar/1st molar contacts
Where is the cotton roll placed to keep the sensor in the right place?
Between biteblock and opposing teeth; NOT between biteblock and imaged teeth
Should you place the cotton roll on the arch you are imaging?
NO! Placed on the opposing arch
What are 2 indications of incorrect placement?
- 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
What are reasons for absence of apical structures in terms of inside the mouth?
Bite block not against occlusal/incisal edge; OR patient not biting down
What is tipping?
Dropped film corner
What is the cause of tipping?
Sensor not placed parallel with the occlusal/incisal surface of teeth
With what angulation are overlapped contacts reduced?
Correct horizontal angulation
When setting a horizontal angle, where should the central ray be directed?
Between the interproximal contacts of interest
Where should the central ray project in relation to the sensor?
Perpendicular
What is the cause of incorrect horizontal angulation?
Central ray is not projected perpendicular to sensor
Mesial to distal or distal to mesial?
Mesial to distal
KNOW HOW TO CHANGE ANGULATION TO DIRECT AND WHERE BEAM WAS COMING FROM
Mesial to distal or distal to mesial?
Distal to mesial
KNOW HOW TO CHANGE ANGULATION TO DIRECT AND WHERE BEAM WAS COMING FROM