The quantitative evaluation of the correlation between the magnification and the visibility-contrast value

Talbot-Lau interferometer, which consists of a conventional x-ray tube, an x-ray detector, and three gratings arranged between them, is a new x-ray imaging system using phase-contrast method for excellent visualization of soft tissue. So, it is expected to be applied to an imaging method for soft tissue in the medical field, such as mammograms. The visibility-contrast image, which is one of the reconstruction images using Talbot-Lau interferometer, is known that the visibility-contrast reflects reduction of coherence that is caused from the x-ray small-angle scattering and the x-ray refraction due to the object’s structures. Both phenomena were not distinguished when we evaluated the visibility signal quantitatively before. However, we consider that we should distinguish both phenomena to evaluate it quantitatively. In this study, to evaluate how much the magnification affect the visibility signal, we investigated the variability rate of the visibility signal between the object-position in the height of 0 cm to 50 cm from the diffraction grating in each case of examining the scattering signal and the refraction signal. We measured the edge signal of glass sphere to examine the scattering signal and the internal signal of glass sphere and some kinds of sheet to examine the refraction signal. We can indicate the difference of the variability rate between the edge signal and the internal signal. We tried to propose the estimation method using magnification.