CBCT

Question 1

Where is CBCT used?

Answer 1

dental hospitals and private

Question 2

what is CBCT commonly known as?

Answer 2

CAT scanning

Question 3

Who developed CT?

Answer 3

Sir Geoffrey Newbold Hounsfield

Question 4

how many HU is air water and cortical bone?

Answer 4

air -1000HU
water 0 HU
cortical bone +1000HU

Question 5

What kV is a CT tube?

Answer 5

120kV

Question 6

What is a voxel?

Answer 6

volume of pixel

Question 7

what are the uses of CT ?

Answer 7

• Intercranial bleed, infarct, tumour.
• Trauma
• Evaluation of osseous lesions
• Salivary glands
• Neoplasia (benign/ malignant) – primary tumour, metastases
• Orthognathic assessment and treatment planning.
• Implant planning

Question 8

what are advantages of CT?

Answer 8

• 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.

Question 9

What are the disadvantages of CT?

Answer 9

• 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.

Question 10

What is the software available mainly for implant planning?

Answer 10

dentascan

Question 11

when was first NHS scanner used?

Answer 11

1971

Question 12

When was the first body scanner used?

Answer 12

1975

Question 13

when was DPT created?

Answer 13

1960s

Question 14

what happens prior to a CBCT scan?

Answer 14

initial positioning view is taken

Question 15

how is patient positioned for CBCT scan?

Answer 15

seated or supine

Question 16

what directions do xray tube and receptor rotate?

Answer 16

opposite each other same direction around patient

Question 17

what sends the information to the computer?

Answer 17

receptor

Question 18

what shape is x-ray beam in CBCT?

Answer 18

cone shaped

Question 19

what are indications in developing dentition for CBCT?

Answer 19

• Localisation of unerupted tooth e.g., maxillary canine
• Assessment of any resorption from unerupted tooth
• Cleft palate patients
• Orthognathic surgery assessment.

Question 20

What are the indications in restorative dentistry for CBCT?

Answer 20

• If conventional radiographs are unhelpful
• Assess periapical lesions, root canal anatomy, perforations.
• Dental trauma
• Dental anomalies.

Question 21

What are the indications in surgery for CBCT?

Answer 21

• 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.

Question 22

What are factors affecting dose?

Answer 22

• Scan times can vary.
• Volume size – FOV
• Type of equipment
• Part of maxillofacial region being imaged.

Question 23

what are advantages of CBCT?

Answer 23

• 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

Question 24

what are disadvantages of CBCT?

Answer 24

• 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.