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4 Radiology > Cone beam computed tomography > Flashcards

Cone beam computed tomography Flashcards

1
Q

what is CT scanning?

A

Slices of tissue that can be stacked to produce a 3d image

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2
Q

compare the x-ray tube kV in dental machines to CT

A

much higher kV x-ray tube in CT than dental machines

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3
Q

what is the movement of a CT scan?

A

Axial movement -> spiral movement (hence called CAT scan)

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4
Q

in CT scanning the attenuation of the beam is measured by what?

A

detectors

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5
Q

in CT scanning
the patient is divided into ?

? assesses the radio-opacity of each one

A

Voxels
A computer

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6
Q

what is a voxel?

A

pixels with volume

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7
Q

what is used to give a quantitative measure of radio-density on CT scans?

A

Hounsfield scale

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8
Q

what Hounsfield number is given to air?

A

-1000

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9
Q

what Hounsfield number is given to water?

A

0

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10
Q

what Hounsfield number is given to cortical bone?

A

+1000

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11
Q

remember CT

A
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12
Q

uses of CT in the head and neck

A

Intracranial - bleed, infarction, tumour

Trauma

Evaluation of osseous lesion

Salivary glands

Neoplasia (benign/malignant) -
primary tumour / metastases

Orthognathic assessment and treatment planning

Implant planning

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13
Q

advantages of CT 3

A

No distortion/magnification like plain radiographs

Multiplanar - manipulate and reconstruct images

Quick like MRI

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14
Q

disadvantages of CT

A

High patient dose

Artefacts (metal objects e.g. amalgam)

May require IV contrast to distinguish tissues e.g. iodine - risk of reaction

Expensive

More difficult to interpret

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15
Q

this shows an amalgam artefact on CT

A
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16
Q

what is dentascan?

A

CT software available mainly for implants

17
Q

compare cone beam CT to traditional CT?

A

X-ray tube rotates around the head capturing data with a cone-shaped x-ray instead of slices

lower radiation dose than medical CT

Still gives 3D image

18
Q

what is taken prior to the CBCT scan to check the area of concern is in the field of view?

A

initial positioning view

19
Q

CBCT - how image is acquired

X-ray tube and receptor ?

X-ray beam is ? shaped

Rotates ?* round patient

? sends information to ?

Initially a ? type image will appear on the PC screen

?? determines how the view can be modified

A

opposite

cone

360*

receptor
computer

DPT

imaging software

20
Q

indications for CBCT use

A

developing dentition
- localisation of unerupted tooth
- Assessment of resorption from unerupted teeth
- Cleft palate patients
- Orthognathic surgery assessment

21
Q

indications CBCT use in restorative dentistry

A

Few indications

Assess periapical lesions, root canal anatomy and perforations

Dental trauma

Dental anomalies

22
Q

indications for CBCT use in surgery

A

Assessment of 3rd molars

Implant assessment

Jaw pathology assessment

TMJ bone surfaces

Facial fractures

23
Q

what is the effective dose for Bitewing or periapical?

A

0.0003 - 0.022 mSv

24
Q

what is the effective dose for DPT?

A

0.0027 - 0.038 mSv

25
Q

what is the effective dose for lateral cephalogram?

A

0.0022 - 0.0056 mSv

26
Q

what is the effective dose for upper occlusal radiographs?

A

0.008 mSv

27
Q

what is the effective dose for CT head?

A

1.4 mSv

28
Q

what is the effective dose for CT mandible and maxilla?

A

0.25 - 1.4 mSv

29
Q

what is the effective dose for dento-alveolar CBCT?

A

0.01 - 0.67 mSv

30
Q

what is the effective dose for craniofacial CBCT?

A

0.03 mSv

31
Q

what affects the dose of an x-ray?

A

Manufacturer

Scan times

Volume size - field of view

Type of equipment

Part of maxillofacial region being imaged

32
Q

advantages of CBCT

A

Multi-planar -> see image from all directions

Geometrically accurate images

Fast scanning times

Good spatial resolution

Lower radiation dose than medical CT

33
Q

disadvantages of CBCT

A

Patient must be still

Soft tissues not imaged well

Radio-dense materials such as restorations produce beam hardening artefacts - streak artefacts

Images can be difficult to interpret

34
Q

this is an I-CAT panoramic radiograph

A
35
Q

this shows an I-CAT radiograph

A
36
Q

remember
Additional training is required for CBCT

A
37
Q

remember

Refer to guidance from European Academy Dentomaxillofacial Radiology

  • Basic Principles for Basic Use of Dental Cone Beam CT
A

4 Radiology (19 decks)

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