Introduction of Computed Tomography

James Chang

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

The generation of CT

Translate-Rotate 1st : pencil beam X-ray and single detector 2st:pencil beam X-ray and mutidector (30)Rotate-Rotate 3st:fan beam X-ray and mutidector (300-

800)Stationary-Rotate 4st:fan beam X-ray and ring

detector(1000-2400) 5st electronbeam (50ms)

http://xic.cc/255-667-1.do

4th Helical CT

http://www.virtualmedicalcentre.com

http://www.imaginis.com/ct-scan/how-does-ct-work

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

Data Acquisition

Sinogram

http://www.physics.ubc.ca/~mirg/home/tutorial/fbp_recon.html

A visual representation of the raw data obtained in a computed axial tomography (CAT) scan.

Sinogram

Filtered Back Projection

Sinogram

1 1 1

1 13 1

1 1 1

3 15 3

1 2 15 2 1

3 15 3

3 15 3

3 15 3

1 2 15 2 1

1 2 15 2 1

1 2 15 2 1

Filtered Back Projection

1 5 1

1 5 1

1 5 13 15 3

1 2 15 2 1

3 15 3

3 15 3

3 15 3

1 2 15 2 1

1 2 15 2 1

1 2 15 2 12 6 6

2 10 2

6 6 2

3 7 7

7 15 7

7 7 3

8 8 8

8 20 8

8 8 8

9 13 9

9 25 9

9 13 9

10 14 14

10 30 10

14 14 10

Filtered Back Projection11 15 15

15 35 15

15 15 113 15 3

1 2 15 2 1

3 15 3

3 15 3

3 15 3

1 2 15 2 1

1 2 15 2 1

1 2 15 2 116 16 16

16 40 16

16 16 16

Without filter

Point object becomes widely spread out

Why do we Apply a Filter ? Another

diagram that illustrates this concept

From Sinogram to Image

Video: http://www.youtube.com/watch?v=kMMyvQF-CYQ&NR=1

Thank you