Sensitivity measurement in x-ray phase-contrast imaging using cascaded grating interferometers

It is known that the sensitivity of X-ray phase-contrast grating interferometry with regard to electron density variations present in the sample is related to the minimum detectable refraction angle. In this article an X-ray phase template is developed that allows for a realistic and quantitative determination of the sensitivity in X-ray phase-contrast imaging using cascaded grating interferometers. The template is designed as a periodic structure composed of different inclination angles and fabricated on a PMMA substrate. Fourier analysis of the moiré fringe patterns generated by the interferometer is used to obtain the phase-contrast image of the template. Experimental results show that the sensitivity, i.e. the minimum detectable refraction angle of this interferometer, is between 0.1 μrad and 0.2 μrad for the template with structure period of 4 mm. This work will help to evaluate and optimize existing cascaded grating interferometers for x-ray differential phase-contrast imaging.