CBCT Imaging Flashcards
Define cone beam CT.
Form of cross-sectional imaging suitable for assessing radiodense structures.
Describe in basic terms how cone beam CT works.
- Ionising radiation.
- Uses conical x-ray beam and square digital detector.
- Rotates around patient’s head.
- With no more than 1 full rotation.
- Captures many 2D images which are constructed into 3D.
How should a patient’s head be positioned in CBCT ?
Horizontally - Frankfort plane level with ground.
Vertically - midsagittal plane.
What are the benefits of CBCT vs. plain film radiography ?
No superimposition.
Ability to view from any angle.
No magnification/distortion.
Allows for 3D reconstruction.
What are the problems of CBCT vs. plain film radiography ?
Increased radiation dose.
Lower spatial resolution.
Susceptible to artefacts.
Expensive equipment.
More complicated to interpret.
Requires additional training.
What are the main benefits of CBCT vs. CT ?
Lower radiation dose.
Higher resolution.
Cheaper.
Smaller footprint.
What are the main benefits of CT vs. CBCT ?
Differentiate soft tissues better.
Larger field of view possible.
What are some common used for CBCT in dentistry ?
- OS - proximity of M3Ms to IAC and cysts.
- Implants - placement and planning.
- Endo - complex root canal morphology.
- Rest - investigating external RR.
What are the three most common planes in CBCT ?
Axial.
Sagittal.
Coronal.
What are the three imaging variables ?
Field of view.
Voxel size.
Acquisition time.
What is a voxel ?
3D pixel.
How much greater is dosage of CBCT vs. OPT ?
2-3x dose.
What are the two main artefacts found on CBCT ?
Streak artefacts.
Movement artefacts.
How can movement artefacts be reduced ?
Using fixation aids - chin rest, head strap.
What are contraindications for CBCT ?
- If plain radiographs are sufficient.
- Requires soft tissue visualisation - infection/malignancy.
- High risk of debilitating artefacts i.e. unable to stay still, able to fit in machine, heavily restored dentition.
