the invention relates to a method for reducing image noise in the context of capturing at least one radiation - based image of a region of interest using two different radiation spectra , in particular two different x - ray radiation spectra , comprising the following steps : capturing raw images of the region of interest using the two different radiation spectra with in each case mutually paired measured values ; and to separate different materials in the region of interest , applying to the captured raw images at least one inversion operator with integrated noise filtering , said operator describing a transition from a measured value pair to an assigned reconstruction value pair .