Statistical estimation of the directional dependency of subject in visibility-contrast imaging with the x-ray Talbot-Lau interferometer

Abstract

Conventional x-ray image is formed by absorption contrast due to attenuation of x-ray intensity. In recent years, the phase-contrast method has highlighted, in which image contrast is decided according to phase shift of x-rays transmitted through an object. The phase-contrast method is excellent for visualization of soft tissue, which is difficult to visualize using conventional x-ray imaging. The Talbot-Lau interferometer using phase-contrast method was developed by Konica Minolta, Inc. There are images of three types can be obtained in the Talbot-Lau interferometer, i.e. absorption image, differential phase-contrast image, and visibility-contrast image. Visibility-contrast image reflects reduction of coherence due to the object’s structures. Its well-known feature is the contrast due to the x-ray small-angle scattering. In addition, in the visibility-contrast image, the relationship between the signal intensity and the direction of the subject’s structure has been analyzed. Talbot-Lau interferometer only detected the phase shift along the periodic direction of grating due to use the one-dimensional grating. In this study, we focused on how the signal intensity was affected by the direction of the subject structure, and analyzed the edge signal of the subject. We imaged acrylic, glass and aluminum cylinder with the Talbot-Lau interferometer by rotating from 0 degree to 90 degrees with respect to the periodic direction of the grating, and measured their edge signal. Moreover, we statistically estimated the angular function from edge signals of cylinder and compared with our previous study’s method. They correspond with high accuracy and this study warrant accuracy of our previous study’s method.