Data in X-ray images of a medical device is processed in order to reduce vibration artifacts in differential phase contrast imaging. A proportionality factor between an object induced phase shift for a first x-ray energy bin and an object induced phase shift for a second x-ray energy bin is provided. At least one of a dark field signal and an object induced phase shift is determined from a detected intensity value of a pixel for the first energy bin and a detected intensity value of the pixel for the second energy bin using the proportionality factor.