GB/T 29034-2012Non-destructive testing - Guide for industrial computed tomography (CT) imaging (English PDF)

4.1 Objective

This standard describes the definition and system performance parameters and system performance of industrial CT imaging and the basic principles of CT system performance parameters

The relationship between indicators. Users determine the applicability of the CT system, you can refer to the present time to predict system performance or to develop new scanning method standard.

Since CT technology in the development, the application scope expanding, the application is very complex, and therefore, this standard does not discuss specific subject

Measurement techniques, such as scanning parameters selection, implementation, and data analysis methods, the scanning process.

4.2 CT principle

CT is a radiation detection method, the resulting image is a distribution diagram of the linear attenuation coefficient of the object. Linear attenuation coefficient described

Ray instantaneous rate of change of attenuation. Ray attenuation is due to the interaction of radiation and the object caused. Ray energy is below the peak

1.02MeV CT systems, the main interaction is the photoelectric effect and Compton scattering. Photoelectric effect depends on the absorbing medium

The atomic number and density, play a major role in low-energy Compton scattering depends on the electron density of the material, from the main high energy effect.

Linear attenuation coefficient and the ratio between the density of the material is able to reflect the physical basis of the CT image density distribution of the object. But the linear attenuation

Coefficient is also related with the energy ray, this feature can sometimes obscure the density difference between CT images, but sometimes reinforced with similar density

The contrast of different materials.

Figure 1 shows the difference between CT and conventional radiography. As it can be seen from Figure 1, the conventional radiographic detection object properties

The presence of superimposed images, can not determine the spatial position of the measured object. CT images from different angles to detect objects, can be more

Accurate location information. Conventional radiography, the information slice plane "P" on the projector in a straight line "AA '", and CT images can be […]