CBCT - Amar Flashcards

(57 cards)

1
Q

Can CBCT see soft tissues?

A

Nein

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2
Q

Estimated scanning time of CBCT

A

1-10

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3
Q

Compare the radiation dose of OPG vs CBCT

A

1 small CBCT = 1 pan
1 large CBCT (ortho) = around 10 OPG

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4
Q

What is the issue with these cbct machines

A

Takes up a lot of space

$$$

High radiation dose

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5
Q

pros of this machine (3)

A

Cheaper Occupies

less space

Lower dose

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6
Q

Required characteristics for ideal diagnostic cbct (5)

A

Good density and contrast

Sharpness

Good resolution

Accuracy in measurements

Free of artifacts

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7
Q

What are some advantages of CBCT (5)

A
  • 3D
  • Good image accuracy and resolution
  • Rapid scan time
  • Allows for selective FoV
  • No magnification
  • Low radiation dose compared to Med CT
    *
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8
Q

How does CBCT radiation differ from med CT

A

CBCT - 0.052 – 1.025 mSv

Med CT - 1.4 - 2.1 mSv

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9
Q

Disadvantages of CBCT

A
  • Artifacts
  • Motion artifacts due to increased scan time compared to med ct
  • Poor contrast resolution (no soft tissue observation)
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10
Q

Limitations of Panoramic imaging (5)

A
  • 2D
  • Horizontal and vertical magnification
  • Distortion
  • Superimposition
    • Positioning errors
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11
Q

What are the 4 components of CBCT image acquisition

A
  1. XRay generation
  2. Image formation / detection
  3. Image reconstruction
  4. Image display
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12
Q

Describe how the xray generator works in CBCT (4)

A

During rotation, many exposures are made at fixed intervals, each offset from one another - called basis images

150-600 basis images produced

Complete series of basis images called projection data // (step called image acquisition)

Projection data then reconstructed in 3 planes (axial, sagittal and coronal) using complicated algorithm

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13
Q
A

Sagittal, axial, coronal

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14
Q

What is CBCT FoV and how can it change?

A

Visible Field of View

  • Can be adjustable
  • Full FoV = nearly full skull (used for ortho)
  • Medium / standard = both arches and TMJ
  • Small FoV = one arch or quadrant

Want to limit the field size to the smallest volume that can accomodate the region of interest

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15
Q

What is CBCT frame rate? Pros (1) and cons (2) of high frame rate?

A

Speed at which images are acquired

Higher frame rates = more pics = increased primary reconstruction time

Higher frame rate = higher radiation dose

Higher frame rate reduces metallic artifacts

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16
Q

2 types of image detectors for CBCT

A

Image intensifier tube / CCD / CMOS

Flat panel detector

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17
Q

What are these two cbct image detectors

A
  1. CCD / CMOS
  2. Flat panel detector
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18
Q

Pixel vs Voxel

A

Pixel = digital equivalent of silver halide crystal in conventional. Smallest controllable element of a picture on screen

Voxel = volumetric pixels, cubic in nature (CBCT is 3D

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19
Q

CBCT vs CT voxels

A

CBCT = isotropic voxel

  • Perfect cube 0.1 - 0.7 mm

CT = anisotropic voxel

  • Brick shaped
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20
Q

What is a “tomographic plane”

A

Single slice of the area interest in a CBCT shown by a line

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21
Q

What are the 3 image types that can be produced by Multiplanar Reformatting (MPR)

A

Axial images with computer generated superimposed curve of alveolar process

Cross sectional Images

Panoramic like images

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22
Q

What are the two types of radiograph resolution?

A

Spatial resolution - differentiate btw two objects of different radio density

Contrast resolution - differentiate two objects of the same color type

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24
Q
A

Lingual foramen

  • careful when placing implant
25
What should you do medico-legally when you take a full-volume / full size CBCT
Refer to dento-maxillofacial radiologist for proper reporting of radiograph * May not need to refer for small section CBCT
26
Arrows - eustachian tube
27
mental foramen
28
What is the dotted line and what happens if it gets blocked
Sinus ostium If blocked - Mucocele AES - anterior ethmoidal sinus MNC - middle nasal concha INC - inferior nasal concha
29
Purposes of CBCT in endodontics (3)
Diagnosis of treatment failure (missed canals) Identifying root fractures Assessment of endo tx **complications** (ex. broken file, extrusion of material into IAC) Evaluation of anatomy / complex morphology (dens invaginatus) Root canal morphology
30
When should CBCT NOT be used for Endo
1. Assessing outcome when there were no difficulties 2. To determine working length
31
What type of CBCT should be taken for endo purposes
Small volume CBCT
32
indications for CBCT in OMFS
1. Investigate exact **location of jaw pathologies** 2. Assess **impacted and supernumary teeth** and proximity to vital structures 3. Consideration of **resorption** of adjacent tooth 4. pre-post surgical assessment of **bone graft** sites 5. **paranasal sinus** pathology 6. planning **orthognathic surgery**
33
nasopalatine cyst
34
retention pseudocyst of maxillary sinus Should NOT have taken CBCT - unnecessary
35
What diseases of the maxillary sinus warrant a CBCT?
Mucocele - painful expanding lesion A. Polyp B. Retention pseudocyst C. Mucocele
36
What should be advised
CBCT to see effect on IAC “Breach in continuity of lingual cortical plate”
37
Uses of CBCT in implantology (6)
Determine presence of disease at site Measure available jaw bone to see if its feasible Determine quality and quantity of bone Nerve mapping / determine proximity to critical structures Determine implant orientation Select the right size of implant for optimal stability
38
What is the required distance between implant and any vital structure
at least 2mm
39
What 2 important structures must you be aware of when placing an implant in the mx anterior region
Incisal foramen Nasopalatine canal
40
Accessory mental foramen Very rare
41
What must you do before placing mandibular posterior implant
CBCT nerve mapping - manually, not automatic * Choose best panoramic-like slice that shows good nerve anatomy * Start at mental foramen * Trace it all the way back
42
Bifid mandibular canal
43
Bifid mandibular canal
44
Orthodontic applications of CBCT
Plus: orthognathic surgery tx planning Accurate estimation for space requirement for unerupted/impacted teeth Assessment of ortho induced RR Post treatment TMD
45
Transposition of 12/13
46
Why is CBCT effective for TMJ assessment
Ability to accurately define the true position of condyle in the fossa
47
Degenerative joint disease “birds beak condyle”
48
What is the ALARA principle
As Low As Reasonable Achievable * take conserative xrays/CBCT, based on diagnostic yield expected
49
Dentoalveolar trauma
50
Is CBCT suitable for internal/external root resorption?
Yes - could potentially be hiding palatally/lingually * Use small volume CBCT
51
External/internal RR * Couldnt see clinically bc subgingival
52
Is CBCT indicated for caries?
No
53
Is cbct indicated for perio?
Not for determining perio bone levels However can be used for infra-bony defects and furcations
54
Perio furcation involvement
55
Is cbct indicated for soft tissue assessment / oral malignancy?
No - should do medical CT or MRI instead HOWEVER, if cancer involves bone - CBCT indicated
56
Benefits of CBCT over med CT
Faster Smaller Safer (lower dose) Less expensive More convenient Specific to dentistry
57
Compare CT with CBCT
Update scan time: CBCT 5-10s Med CT - \<10s