1. A method for generating a selective magnetic resonance (MR) image, comprising: providing a processor with a first MR image comprising raw data acquired at a first echo time after at least one excitation pulse in a magnetic resonance data acquisition unit; providing said processor with a second MR image comprising raw data acquired at a second echo time after each excitation pulse in said magnetic resonance data acquisition unit from which raw data were acquired at said first echo time; in said processor, for each image point of said first and second MR images, calculating a time constant that corresponds to tissue imaged at the respective image point, dependent on respective intensity values of corresponding image points in said first and second MR images; in said processor, comparing each calculated time constant with at least one threshold, to obtain a comparison result; in said processor, dependent on said comparison result, associating a weighting factor with each image point; and generating a selective MR image by processing the respective intensity values of the image points of at least one of said first MR image and said second MR image with the respective, associated weighting factors.