1. Basic Principles of Computed Tomography
Dr. Kazuhiko HAMAMOTO
Dept. of Infor. Media Tech.
Tokai University

2. What is the CT? Mathematical transform to the measured data.
Reconstruct n dimension function (image) => projection data of n – 1 dimension
Radon Transform (1917) “Two dimension and three dimension object can be reconstructed from the infinite set of projection data”.
The First CT: 1973 in the U.S.　 　　　　　　4 minutes scan, thickness of 10mm

3. Concept of CT CT Algorithm
・Getting the shape by back projection of the projection data.
・For example, outward view is the quadrangle => it is the cylinder CT
Algorithm

4. Basic principle of CT -Reconstruction of 2 dimensional image-
Projection Data
curvilinear integral of absorption coefficient regarding Y X y y
X-ray detector array Y X x
object x X
Blur
X-ray
tube
Data Acquisition field
Reconstruction field
Simple Backprojection

5. Basic principle of CT -Reconstruction of 2 dimensional image-
Projection Data x y x X ＊
Filtered Projection data
Reconstruction Filter x ω or x
Multidirectional
Backprojection
Filtered Backprojection

6. Reconstruction process

7. Reconstruction process
Data acquisition at angle : 0 – 180 degree
Obtain F(u,v) and then 2D IFFT -> reconstruction
Radon Transform is equivalent to Filtered backprojection !

8. Simple Backprojection
Example of Simulation
Model Image
Simple Backprojection
Filtered
Backprojection