Question 1

What is the uses of CT in the head and neck?

Accepted Answer

- Intracranial - bleed, infarct, tumour - trauma - evaluation of osseous lesions - salivary glands - neoplasia (benign/malignant) - primary tumour/metastases - orthognathic assessment and treatment planning - implant planning

Question 2

What are the advantages of CT?

Accepted Answer

- Not subject to the same magnification and distortion as plain radiographs - multi-planar (manipulate, reconstruct images) - avoids superimposition - images bone and soft tissue - differentiate different tissues - you can see the bone and brain for head injuries - speed (very quick like an MRI)

Question 3

Disadvantages of CT?

Accepted Answer

- Patients 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 - both CT and MRI are still expensive - interpretation more difficult

Question 4

what is dentascan?

Accepted Answer

software that is available mainly for implant planning

Question 5

Why use CBCT?

Accepted Answer

- CBCR is a variation on traditional computed tomography (CT) - In CBCT an X-ray tube and detector panel rotate around the patient capturing data with a cone-shaped X-ray instead of slices - it has a much lower radiation dose than medical grade CT - overcomes the issues of 2d imaging - CBCT can give you 3d images - conventional CT images may not give the whole information required for diagnosis & treatment planning - should only be used if the information gained has an impact on patient care - some machines have a large field of view (FOV) and are usually within hospital departments

Question 6

CBCT - how the image is acquired?

Accepted Answer

- patient positioned either seated or lying supine, depending on the machine - the x-ray tube and the flat panel receptor are opposite each other and rotate around the patient in the same direction at the same time - the receptor sends the information to the computer where an image will appear on the screen

Question 7

How is the image displayed?

Accepted Answer

- A DPT type image is usually the first image displayed on the PC screen - the imaging software used will determine how the view can be modified - if multi-planar imaging is available then three slices will be displayed - axial, coronal and sagittal - some software will allow these planes to viewed obliquely - which is very useful if you want to slice through the dental arch - 3D reconstruction can also available

Question 8

Indications for CBCT - the developing dentition?

Accepted Answer

- Localization of unerupted tooth e.g. maxillary canine - Assessment of any resorption from unerupted tooth - cleft palate patients - orthognathic surgery assessment

Question 9

Restorative dentistry and CBCT

Accepted Answer

- Few indications - only if conventional radiographs are unhelpful - can be used to assess periapical lesions, root canal anatomy, perforations - dental trauma - dental anomalies

Question 10

CBCT and surgery

Accepted Answer

· Assessment of the 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.

Question 11

Trauma and Pathology: - How CBCT helps with diagnosis and treatment planning.

Accepted Answer

Patient with Facial Trauma · Clinically thought to have a fractured condyle. · Not seen clearly on plain radiographs – DPT and PA mandible · Referred for a CBCT. · Next slide show the 3D reconstruction with some anatomy removed. · Fractured condylar head is seen to be displaced medially.

Question 12

football injury

Accepted Answer

· Patient a black eye left side · Complaining of some double vision · Plain radiographs Occipito Mental 10- & 30-degree films · Left maxillary sinus is opaque (cloudy) · Left infra-orbital margin uneven. · CBCT requested for further information.

Question 13

What affects the dose?

Accepted Answer

· Some exposure factures are set by the manufacturer – kV, time & mA. · Scan times can be varied. · Volume size – FOV · Type of equipment used. · Part of maxillofacial region being imaged.

Question 14

Advantages of CBCT

Accepted Answer

 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 15

Disadvantages of CBCT

Accepted Answer

· 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.

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CBCT - Cone beam computed tomography Flashcards

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