Basic Principles of Computed Tomography

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Basic Principles of Computed Tomography

• Dr. Kazuhiko HAMAMOTO
• Dept. of Infor. Media Tech.
• Tokai University

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What is the CT?

• Mathematical transform to the measured data.
• Reconstruct n dimension function (image) gt
  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

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Concept of CT
Getting the shape by back projection of the
projection data. For example, outward view is
the quadrangle gt it is the cylinder
CT Algorithm
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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
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Basic principle of CT -Reconstruction of 2
dimensional image-
Projection Data
x

Filtered Projection data
Reconstruction Filter
Multidirectional Backprojection
Filtered Backprojection
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Reconstruction process
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Reconstruction process
Data acquisition at angle 0 180 degree
Obtain F(u,v) and then 2D IFFT -gt reconstruction
Radon Transform is equivalent to Filtered
backprojection !
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Example of Simulation
Model Image
SimpleBackprojection
Filtered Backprojection