Introduction
The development of computed tomography (CT) in the early 1970's revolutionized medical radiology. For the first time, physicians were able obtain high- quality tomographic (cross sectional) images of internal structures of the body. Over the next 10 years, 18 manufactures competed for the exploding world CT market. Technical sophistication increased dramatically, and even today, CT continues to mature, with new capabilities being researched and developed (Kak, Slaney, 1988).
Computed Tomography (CT) scanner is a desired device to create images of internal structure of unrecognized object. However, many criticisms have been addressed to the manner the CT technology developed. It is true that the development of CT devices have been extremely advanced. The system looks sophisticated, fast, but it tends to be more expensive, more complicated and lack of accuracy (Herman, 1980).
Physics
The general process of creating cross-sectional or tomographic images from projections (line integrals) of the object at multiple angles and using a computer for image reconstruction. If unmodified, the term CT generally implies images made from projections measured by transmission of x rays (X-ray computed tomography). However, the term could also include SPECT imaging and PET imaging and even some ultrasound techniques based on projection measurements.
In all forms of CT, the input projection data are line integrals or ray sums of some property, and the tomographic image is a representation of that property. In X-ray CT, the function imaged is the distribution of linear attenuation coefficient since, for monochromatic X-rays, the logarithm of the transmitted intensity is proportional to the integral of the attenuation coefficient along the path. In emission CT, the imaged property is the distribution of radionuclide concentration. Corrections for attenuation must be applied in order for the projections and the desired property, the distribution of radionuclide concentration, to have the proper relationship........
