Study of contrast and modulation mechanisms in X-ray/photon transverse axial transmission tomography.

The ultimate capabibity and a detailed study of contrast and modulation in the context of photon transmission tomography (or computerized transverse axial tomography (CTAT)) is presented. Quantitative evaluation of atomic number, density and electron density of compound materials were made by X-ray fluorescence and combustion analysis, and the attenuation coefficients of photoelectric and Compton effect were measured with high resolution Ge(Li) and Si(Li) detectors. This study provides a guide to an understanding of the high resolution of the currently existing X-ray transmission CTAT scanner (EMI scanner) and to the future development of high resolution scanners.