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Specialized Gen Rad > Week 9 CBCT > Flashcards

Week 9 CBCT Flashcards

1
Q

CBCT

A

cone beam computed tomography

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2
Q

CBCT used for

A

maxillofacial imaging (2D to 3D)

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3
Q

principle of CBCT

A
  • cone shaped x-ray beam
  • rotation center fixed in center of ROI
  • rotates 180 - 360 degrees to acquire multiple 2D images to construct 3D CBCT volume
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4
Q

what is added for back projection image reconstruction

A

attenuation profiles of each basis projection image created & stitched together

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5
Q

FOV

A

field of view

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6
Q

what is FOV

A

scan volume

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7
Q

what does collimation control

A

FOV size & radiation exposure

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8
Q

what does IR size determine

A

FOV capabilities

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9
Q

what is ROI for small FOV

A

< 5 cm size

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10
Q

purpose of small FOV

A

increased spatial resolution & endodontic purpose

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11
Q

use of small FOV

A

relation of impacted tooth w/ surrounding structures
- periodontal ligament spaces
- lamina dura
- root #
- periapical lesions
- root canal morphology

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12
Q

size of medium FOV

A

6 - 11 cm

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13
Q

use of medium FOV

A
  • image 1 or 2 dental arches
  • assess lesion extent / TMJ / implants
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14
Q

large FOV size

A

11 - 24 cm

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15
Q

use of large FOV

A

surgical planning from vertex of skull to inferior border of mandible

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16
Q

pixel vs voxel

A

pixel = 2D, voxel = 3D

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17
Q

decreased voxel size =

A

increased spatial resolution & dose

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18
Q

isotropic voxels are ___ in all dimensions

A

equal

19
Q

which voxel is used for diagnostic task

A

largest voxels

20
Q

MPR

A

multiplanar reconstruction

21
Q

what allows 3D data to be sectioned in any plane to produce 2D images

A

isotropic voxels

22
Q

orthogonal views

A

axial, coronal, sagittal

23
Q

non-orthogonal views

A

oblique
curved planar / panoramic reconstruction
cross-sectional

24
Q

oblique view used to

A

transect & evaluate specific structures

25
Q

serial cross section used to

A

evaluate teeth & alveolar bone width

26
Q

surface volume render used to

A

visualize & analyze craniofacial conditions

27
Q

MIP

A

maximum intensity projection

28
Q

MIP used for

A

impacted tooth
TMJ
#
craniofacial analysis
soft tissue calcification

29
Q

components of CBCT

A

head immobilizers
x-ray tube
handle
IR
chin rest & bite block

30
Q

CBCT indicators

A

implant planning
paranasal sinuses
evaluate: TC PET (trauma, craniofacial, pathology, endodontic, TMJ)
root resorption
assess 3rd molar in relation with IAC

31
Q

small FOV of develop dentition

A

localize unerupted / impacted tooth
assess cleft palate
assess excess resorption in relation to unerupted teeth

32
Q

medium FOV of develop dentition

A

assess cleft palate
planning complex orthodontic surgery of maxillofacial anomalies

33
Q

large FOV of develop dentition

A

planning complex orthodontic surgery of maxillofacial anomalies

34
Q

small FOV of restoring dentition

A
  • assess periodontal infra-bony defects & furcation lesions
  • assess teeth for root # / periapical disease
  • root canal anatomy
  • surgical endodontic planning
  • dental trauma due to alveolar #
35
Q

CBCT not indicated for

A
  • routine assessments = root canal anatomy, periapical disease, periodontal, orthodontic diagnosis
  • dental caries
  • planning temporary anchorage placements
36
Q

what does imaging protocol determine

A
  • exposure settings
  • voxel size
  • scan time
  • number of projections
  • scanning trajectories
  • FOV
37
Q

CBCT patient positioning

A
  1. patient erect / sitting upright
  2. bring machine to chin
  3. bite onto incisor bite block using upper & lower incisors
  4. hold onto stabilizing handles
  5. immobilize head via bite sticks, chin rests, posterior / lateral head supports
  6. alignment references: MSP, frankfurt, occlusal plane
38
Q

after exposure, what should u check before dismissing patient

A

CBCT volume sufficient for reconstruction

39
Q

what must CBCT request forms include

A
  • indication
  • ROI / FOV / Drawing
  • voxel size
  • mode
  • special instructions
40
Q

benefits of CBCT

A
  • fast, economical, comfortable
  • geometrically accurate
  • decreased dose
  • interactive display modes
  • MPR allows anatomy to be viewed in diff planes
  • 3D rendering
  • increased spatial resolution
  • compatible with implant & cephalometry planning software
41
Q

CBCT > CT factors

A

smaller & cheaper,
decreased dose & time taken
increased spatial resolution

42
Q

CBCT < CT factors

A

increased image nose, quantum mottle, electronic noise
poor soft tissue contrast

43
Q

what causes scatter in CBCT

A

cone beam

44
Q

what causes quantum mottle in CBCT

A

lack of homogenization of beam

Specialized Gen Rad (13 decks)

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