CBCT Flashcards
Where is CBCT used?
dental hospitals and private
what is CBCT commonly known as?
CAT scanning
Who developed CT?
Sir Geoffrey Newbold Hounsfield
how many HU is air water and cortical bone?
air -1000HU
water 0 HU
cortical bone +1000HU
What kV is a CT tube?
120kV
What is a voxel?
volume of pixel
what are the uses of CT ?
- Intercranial bleed, infarct, tumour.
- Trauma
- Evaluation of osseous lesions
- Salivary glands
- Neoplasia (benign/ malignant) – primary tumour, metastases
- Orthognathic assessment and treatment planning.
- Implant planning
what are advantages of CT?
- Not subject to the same magnification and distortion as plain radiographs.
- Multi-planar (manipulate, reconstruct images) – avoids superimposition.
- Images bone and soft tissue (head injury, see bone and brain)
- Speed (cf MRI)
- Both CT and MRI are still expensive pieces of equipment.
What are the disadvantages of CT?
- Patient dose
- Artefacts (metallic objects, amalgam in head and neck)
- May require intravenous contrast to distinguish tissues (iodine based, risk of reaction)
- Expensive in comparison with plain radiography.
- Interpretation more difficult.
What is the software available mainly for implant planning?
dentascan
when was first NHS scanner used?
1971
When was the first body scanner used?
1975
when was DPT created?
1960s
what happens prior to a CBCT scan?
initial positioning view is taken
how is patient positioned for CBCT scan?
seated or supine
what directions do xray tube and receptor rotate?
opposite each other same direction around patient
what sends the information to the computer?
receptor
what shape is x-ray beam in CBCT?
cone shaped
what are indications in developing dentition for CBCT?
- Localisation of unerupted tooth e.g., maxillary canine
- Assessment of any resorption from unerupted tooth
- Cleft palate patients
- Orthognathic surgery assessment.
What are the indications in restorative dentistry for CBCT?
- If conventional radiographs are unhelpful
- Assess periapical lesions, root canal anatomy, perforations.
- Dental trauma
- Dental anomalies.
What are the indications in surgery for CBCT?
- Assessment of lower third molars to the inferior dental canal
- Assessment of the morphology of all third molars
- Implant assessment
- Assessment of pathology involving the jaws
- Assessment of the TMJ bone surfaces
- Facial fractures – especially if unclear on plain views.
What are factors affecting dose?
- Scan times can vary.
- Volume size – FOV
- Type of equipment
- Part of maxillofacial region being imaged.
what are advantages of CBCT?
- Multi-planar reformatting (MPR) allows image to be viewed from all directions.
- Geometrically accurate images
- Fast scanning time
- Compatible with other software
- Good spatial resolution
- Lower radiation dose than medical CT
what are disadvantages of CBCT?
- Patient must be still to avoid movement artefacts.
- Soft tissues are not imaged well.
- Radio-dense materials such as restorations and RF material produce beam hardening artefacts – streak artefacts
- Images can be difficult to interpret particularly if a large FOV is used.