CBCT Flashcards

1
Q

what does CBCT stand for

A

cone beam computed tomography

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2
Q

what type of radiation does CBCT involve

A

ionising radiation

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3
Q

how does a CBCT machine work

A

conical/pyramidal x-ray beam
square digital receptor rotate around the head
no more than 1 full rotation

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4
Q

how is the patient positioned for CBCT

A

machine specific
usually standing or sitting
frankfort plane parallel to floor
mid sagittal plane in the middle

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5
Q

what are the four benefits of CBCT over plain radiography

A

no superimposition
ability to view subject from any angle
no magnification/ distortion
allows for 3D reconstruction

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6
Q

what are four disadvantages of CBCT over plain radiography

A

increased radiation dose to patient
lower spatial resolution (not as sharp)
susceptible to artefacts
equipment more expensive

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7
Q

what are two benefits of CBCT vs Conventional CT

A

lower radiation dose
potential for sharper images

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8
Q

what are the benefits of conventional CT over CBCT

A

able to differentiate soft tissues better
larger field of view

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9
Q

name four main uses of CBCT in dentistry

A

relationship between impacted mandibular 8 and IAN canal
measuring alveolar bone dimensions in implant planning
visualising complex root canal morphology to aid endodontic treatment
assessing large cystic jaw lesions

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10
Q

what are the common orthogonal planes

A

axial
sagittal
coronal

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11
Q

what is the axial plane

A

looking up through base of skull

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12
Q

what is the sagittal plane

A

as if skull has been halved at sagittal suture

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13
Q

what is the coronal plane

A

as if skull has been cut at coronal suture (front view of the face)

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14
Q

what are the three examples of imaging factors/ variables

A

field of view
voxel size
acquisition time

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15
Q

how are imaging factors/ variables worked out

A

differs from patient to patient
takes into account ALARP principle

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16
Q

what is the field of view

A

size of captured volume of data

17
Q

what is voxel size

A

the image resolution
voxels = 3D pixels

18
Q

what does an increase in field of view cause

A

increase in radiation dose and increase in number of tissue irradiated and increase scatter

19
Q

what does a decrease voxel cause

A

increases radiation dose and increased scan time

20
Q

what are the range of options for voxel size

A

0.4 mm cubed to 0.085 mm cubed

21
Q

rate these x-rays by highest dose to lowest :
panoramic, CT, intraoral and CBCT

A

CT
CBCT
panoramic
intraoral

22
Q

what are the two main types of artefact

A

movement artefact
streak artefact

23
Q

name three contra-indications to CBCT

A

if plain radiographs are sufficient
high risk of debilitating artefacts
if there is pathology requiring soft tissue visualisation