Computed Tomography Outline X-RAY Computed Tomography Artifacts - - PowerPoint PPT Presentation

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Computed Tomography Outline X-RAY Computed Tomography Artifacts - - PowerPoint PPT Presentation

Mar 14, 2024 453 likes •833 views

Computed Tomography Outline X-RAY Computed Tomography Artifacts and Sources of Error Imaging studies Bone Cartilage Other Outline X-RAY Computed Tomography Artifacts and Sources of Error Imaging studies

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SLIDE 1

Computed Tomography

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SLIDE 2

Outline

  • X-RAY
  • Computed Tomography
  • Artifacts and Sources of Error
  • Imaging studies
  • Bone
  • Cartilage
  • Other
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SLIDE 3

Outline

  • X-RAY
  • Computed Tomography
  • Artifacts and Sources of Error
  • Imaging studies
  • Bone
  • Cartilage
  • Other
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SLIDE 4

X-rays are ionizing, invisible and highly penetrating electromagnetic radiation X-RAY: radiation type

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SLIDE 5

X-RAY: how to generate?

Heated filament emits electrons by thermionic emission

X-RAY produced when high speed electrons hit metal target

Electrons are accelerated by a high voltage

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SLIDE 6

X-RAY: attenuation

  • Attenuation depends on:
  • Thickness
  • Density
  • Effective atomic number
  • Energy of the X-RAY

beam

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SLIDE 7

X-RAY

  • Projection:
  • Projections over 180o
  • Reconstruct to 3D
  • Fast
  • Non-destructive
  • Direct 3D calculations
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SLIDE 8

Outline

  • X-RAY
  • Computed Tomography
  • Artifacts and Sources of Error
  • Imaging studies
  • Bone
  • Cartilage
  • Other
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SLIDE 9

CT – Back Projection

  • In standard back-projection, images are taken for a number of angles

positions and then smeared back to form the section

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SLIDE 10

CT – Back Projection

Original Shadow Back projection

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SLIDE 11

Outline

  • X-RAY
  • Computed Tomography
  • Artifacts and Sources of Error
  • Imaging studies
  • Bone
  • Cartilage
  • Other
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SLIDE 12

7 6 5 4 3 2 1 0.0 10.0 20.0 30.0 40.0 50.0

Total exposure in mGy Scan resolution (microns)

Artifacts and Sources of Error

  • Radiation dose

in mice:

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SLIDE 13

Artifacts and Sources of Error

  • Beam hardening:
  • Theoretical model: beam with only high energy photons

35% 35% 60% 20% 20% 50% High energy photons Low energy photons

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SLIDE 14

Artifacts and Sources of Error

  • Beam hardening:
  • Theoretical model: beam with only high energy photons
  • Beam hardening:
  • True model:

mixed beam

35%  75% error 35% 60%  20% error

35% 35% 60% 20% 20% 50%

High energy photons Low energy photons

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SLIDE 15

Artifacts and Sources of Error

  • Rat femur with titanium implant:
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SLIDE 16

Artifacts and Sources of Error

  • Beam hardening,

correction via:

  • Physical filter

(aluminum)

  • Correction

afterwards using software

Unfiltered Filtered

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SLIDE 17

Artifacts and Sources of Error

  • Ring artifacts:

due to drift and nonlinearities in the response of individual elements in the detector

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SLIDE 18

Artifacts and Sources of Error

  • Alignment error:
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SLIDE 19

Outline

  • X-RAY
  • Computed Tomography
  • Artifacts and Sources of Error
  • Imaging studies
  • Bone
  • Cartilage
  • Other
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SLIDE 20

Lateral Medial Trabecular bone Epiphysis Cross-section

Micro-CT analysis

  • 3D-models:
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SLIDE 21

Control Osteoarthritis induced

Bone

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SLIDE 22

Bone

  • Architectural bone changes validated with histology

New bone Resorbed bone

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SLIDE 23

Bone

  • Femur defect
  • Filled with

porous titanium structure

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SLIDE 24

Outline

  • X-RAY
  • Computed Tomography
  • Artifacts and Sources of Error
  • Imaging studies
  • Bone
  • Cartilage
  • Other
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SLIDE 25

Cartilage Synovial fluid

uCTa: microCT-arthrography

Bone

Healthy microCT

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SLIDE 26

Cartilage Synovial fluid

uCTa: microCT-arthrography

Bone

Healthy microCT

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SLIDE 27

Cartilage Synovial fluid

uCTa: microCT-arthrography

Bone

OA microCT

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SLIDE 28

Contrast-enhanced microCT

Low attenuation (high GAG) High attenuation (low GAG)

Healthy control OA-induced / mono-iodoacetate

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SLIDE 29

Micro-CT analysis

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SLIDE 30

Outline

  • X-RAY
  • Computed Tomography
  • Artifacts and Sources of Error
  • Imaging studies
  • Bone
  • Cartilage
  • Other
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SLIDE 31

Contrast-enhanced microCT

  • Mouse lung

sample

  • With contrast

agent

  • 5.7μm pixel

size

Source: http://www.skyscan.be/applications/biomedical/biomed002.htm

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SLIDE 32

Contrast-enhanced microCT

  • Mouse kidney sample
  • With contrast

agent

  • 80μm pixel size

Source: http://www.scanco.ch/applications/biomedical.html

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SLIDE 33

Contrast-enhanced microCT

  • Rat vascular system
  • With contrast

agent

  • 75μm pixel size
  • vivaCT

Source: http://www.scanco.ch/applications/biomedical.html

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SLIDE 34

Cardiac function

Cranial Caudal Diastole Systole

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SLIDE 35

Contrast-enhanced microCT

  • Mouse (in-vivo)
  • NO contrast agent
  • 160μm pixel size

Source: http://www.skyscan.be/applications/biomedical/biomed006.htm

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SLIDE 36

Contrast-enhanced microCT

  • Mouse (in-vivo)
  • WITH contrast agent
  • 160μm pixel size
  • Real-time radiography
  • f heart activity and contrast

propagation

Source: http://www.skyscan.be/applications/biomedical/biomed006.htm