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

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

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

6. Reconstruction process

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

8. Example of Simulation Model ImageSimple Backprojection Filtered Backprojection