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Learn about the mathematical transformation, Radon Transform, and the CT reconstruction process. Explore the history of CT imaging and the principles of back projection and filtered backprojection. Discover how 2-dimensional images are reconstructed from projection data.
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Basic Principles of Computed Tomography Dr. Kazuhiko HAMAMOTO Dept. of Infor. Media Tech. Tokai University
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
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
X Blur Basic principle of CT-Reconstruction of 2 dimensional image- Projection Data curvilinear integral of absorption coefficient regarding Y y y X-ray detector array Y X x x object X X-ray tube Reconstruction field Data Acquisition field Simple Backprojection
y x X x ω or x Basic principle of CT -Reconstruction of 2 dimensional image- Projection Data x * Filtered Projection data Reconstruction Filter Multidirectional Backprojection Filtered Backprojection
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 !
Example of Simulation Model Image SimpleBackprojection Filtered Backprojection