A method is for processing a first image data set including a first image value tuple associated with a volume element of a region of an object to be imaged. In an embodiment, a second image data set is generated based upon the first image data set, including a second image value tuple associated with the volume element, a base material decomposition being capable of being carried based upon the second image data set and based upon a base material set; a starting area and a target area are selected as a function of the base material set, the first image value tuple being located in the starting area; the second image value tuple is ascertained based upon the first image value tuple, the second image value tuple being associated with the first image value tuple via image value tuple imaging and being located in the target area.