Introduction of Computed Tomography

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Introduction of Computed Tomography

• James Chang

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History of CT

• Radon-Nikodym theory of Johann.Radon
• G.N.Huunsfeild invented CT in 1972
• Nobel Prize in Physiology or Medicine 1979

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The generation of CT

• Translate-Rotate
• 1st pencil beam X-ray and single detector
• 2stpencil beam X-ray and mutidector (30)
• Rotate-Rotate
• 3stfan beam X-ray and mutidector (300-800)
• Stationary-Rotate
• 4stfan beam X-ray and ring detector(1000-2400)
• 5st electronbeam (50ms)

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http//xic.cc/255-667-1.do
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4th Helical CT
http//www.virtualmedicalcentre.com
http//www.imaginis.com/ct-scan/how-does-ct-work
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CT from 1st to 4th generation

• Original axial CT image from the dedicated
  Siretom CT scanner circa 1975. This image is a
  coarse 128 x 128 matrix

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Data Acquisition
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Sinogram
A visual representation of the raw data obtained
in a computed axial tomography (CAT) scan.
http//www.physics.ubc.ca/mirg/home/tutorial/fbp_
recon.html
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Sinogram
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Filtered Back Projection
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Sinogram
1 2 15 2 1
3 15 3
1 2 15 2 1
3 15 3
1 1 1
1 13 1
1 1 1
1 2 15 2 1
3 15 3
1 2 15 2 1
3 15 3
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Filtered Back Projection
1 5 1
1 5 1
1 5 1
2 6 6
2 10 2
6 6 2
1 2 15 2 1
3 15 3
1 2 15 2 1
3 7 7
7 15 7
7 7 3
8 8 8
8 20 8
8 8 8
3 15 3
1 2 15 2 1
3 15 3
9 13 9
9 25 9
9 13 9
10 14 14
10 30 10
14 14 10
1 2 15 2 1
3 15 3
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Filtered Back Projection
11 15 15
15 35 15
15 15 11
16 16 16
16 40 16
16 16 16
1 2 15 2 1
3 15 3
1 2 15 2 1
3 15 3
Without filter Point object becomes widely spread
out
1 2 15 2 1
3 15 3
1 2 15 2 1
3 15 3
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Why do we Apply a Filter ?

• Another diagram that illustrates this concept

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From Sinogram to Image
Video http//www.youtube.com/watch?vkMMyvQF-CYQ
NR1
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Thank you