A medical data processing method for determining the position of an artifact in patient image data describing a set of tomographic slice images of an anatomical structure of a patient, the method comprising executing, on at least one processor of at least one computer, steps of: a) acquiring the patient image data describing the set of tomographic slice images of the anatomical structure, wherein the images are described by color values; b) determining, based on the patient image data and for a plurality of pairs of adjacent ones of the slice images, color value difference data describing differences in color values for image elements in adjacent slice images by subtracting a color value of an element of a first one of a pair of adjacent slice images from a color value of an element of a second one of the pair of adjacent slice images; c) determining, based on the color value difference data, at least one of positive difference data, describing a subset of the differences and consisting of differences having a positive value, or negative difference data, describing a subset of the differences and consisting of differences having a negative value; d) determining, based on the at least one of the positive difference data or the negative difference data, smoothed difference data describing a smoothing of the differences contained in the at least one of the positive difference data or the negative difference data; e) determining, based on the at least one of the positive difference data or the negative difference data and the smoothed difference data, artifact position data describing the position of an artifact in the patient image data, characterized in that determining the artifact position data comprises comparing the at least one of the positive difference data or the negative difference data to the smoothed difference data by establishing a difference between the at least one of the positive difference data or the negative difference data and the smoothed difference data. a) acquiring the patient image data describing the set of tomographic slice images of the anatomical structure, wherein the images are described by color values; b) determining, based on the patient image data and for a plurality of pairs of adjacent ones of the slice images, color value difference data describing differences in color values for image elements in adjacent slice images by subtracting a color value of an element of a first one of a pair of adjacent slice images from a color value of an element of a second one of the pair of adjacent slice images; c) determining, based on the color value difference data, at least one of positive difference data, describing a subset of the differences and consisting of differences having a positive value, or negative difference data, describing a subset of the differences and consisting of differences having a negative value; d) determining, based on the at least one of the positive difference data or the negative difference data, smoothed difference data describing a smoothing of the differences contained in the at least one of the positive difference data or the negative difference data; e) determining, based on the at least one of the positive difference data or the negative difference data and the smoothed difference data, artifact position data describing the position of an artifact in the patient image data, characterized in that