1. A method for determining a property map of an object based on at least a first magnetic resonance (MR) image of the object, comprising: defining a structure of reference pairs, wherein each reference pair has at least first and second entries, wherein each of said first entries represents an unknown property value, and wherein each of said second entries represents a group of image points belonging together, which are extracted from said first MR image recorded by a scanner, wherein the group of image points includes at least one interesting image point which corresponds to one of the unknown property-values, wherein each unknown property value represents an attenuation value; providing a plurality of training pairs, wherein a structure of the training pairs corresponds to the structure of said reference pairs, and wherein first and second entries of the respective training pairs are known; and determining an assignment between the first entries and the second entries of the training pairs by machine learning, and predicting an attenuation value for an arbitrary image point which corresponds to the at least one interesting image point of the first MR image by applying the determined assignment to one of the second entries of the reference pairs including said arbitrary image point.