A medical data processing method of determining a virtual image (2) of a part of a patient's body (4), the method being constituted to be executed by a computer and comprising the following steps: a) acquiring (S1) patient image data describing at least two two-dimensional patient images (1) of anatomical body parts (3) of the patient's body (4)； b) acquiring (S2) atlas data describing a general structure (5) of at least part of the patient's body comprising correspondence parts corresponding to the anatomical body parts (3)； c) acquiring correspondence part position data describing the positions of the correspondence parts in the general structure (5)； determining (S4.1, S4.2, S4.3), based on the patient image data and the atlas data and the correspondence part position data, virtual image data describing a two-dimensional virtual image (2) of a part (21, 22) of the general structure (5) having a position in the general structure (5) which lies between the positions of the correspondence parts.
