The cross-sectional images represent the local density of the material by reconstruction operation from many multidirection transmission data. Local density of object can be measured exactly because the quality of transmission data get well in comparison with radiography.

Although the major objects of tomographic evaluation are defect detection of object, density measuring is thought after this to become importance. The density resolution of CT system is high because of reconstructed image computed by many multidirection recording attenuation data.

We employed a linear accelerator as high energy X-ray sources for this CT system. Photon's energy emitted from the linear accelerator are maximum 0.95 MeV. This X-ray can penetrate in aluminum to 35 mm and measure the density from the cross- sectional image of object. An experiment is performed to sintered aluminum powder (diameter 43 mm) and microporosities are included inside. Density resolution of this CT system was ± 1% according to experimental results.

Based on the fundamental experiment results, this CT system can be used to analyze the composition of object made of aluminum casting.

This system is applied to quantitative analysis of micro porosities in aluminum, because the reconstructed images give the distribution of the linear attenuation coefficient which corresponds to the density of the object.