A medical data processing method of determining anatomical structure subset data describing a subset of a graphical representation of an anatomical structure of a patient's body to be displayed simultaneously with a medical image of an anatomical body part, the method being constituted to be executed by a computer and comprising the following steps: a) acquiring predetermined anatomical structure representation data describing a graphical representation of the anatomical structure and its position in the patient's body; b) acquiring anatomical body part image data describing an image of an anatomical body part of the patient imaged by an optical imaging apparatus for display by a display apparatus; c) acquiring optical parameter data describing a value of an optical parameter serving as a basis for displaying the anatomical body part image data; d) determining, based on the anatomical structure representation data and the anatomical body part image data and the optical parameter data, anatomical structure subset data describing a subset of the anatomical structure representation data, which subset describes a graphical representation of a structure subset of the anatomical structure to be displayed simultaneously with the image of the anatomical body part, wherein the anatomical structure subset data is determined based on a size of parts of the anatomical structure contained in the structure subset; e) acquiring optical parameter interval data describing a predetermined interval of values for the optical parameter in which the anatomical structure subset data can be determined; f) determining, based on the optical parameter data and the optical parameter interval data, whether the value of the optical parameter lies in the interval, wherein the anatomical structure subset data is determined if it is determined that the value of the optical parameter lies in the interval, characterized by g) determining, if it is determined that the value of the optical parameter lies in the interval, interval indication data describing information to be output to a user indicating whether the optical parameter lies in the interval. a) acquiring predetermined anatomical structure representation data describing a graphical representation of the anatomical structure and its position in the patient's body; b) acquiring anatomical body part image data describing an image of an anatomical body part of the patient imaged by an optical imaging apparatus for display by a display apparatus; c) acquiring optical parameter data describing a value of an optical parameter serving as a basis for displaying the anatomical body part image data; d) determining, based on the anatomical structure representation data and the anatomical body part image data and the optical parameter data, anatomical structure subset data describing a subset of the anatomical structure representation data, which subset describes a graphical representation of a structure subset of the anatomical structure to be displayed simultaneously with the image of the anatomical body part, wherein the anatomical structure subset data is determined based on a size of parts of the anatomical structure contained in the structure subset; e) acquiring optical parameter interval data describing a predetermined interval of values for the optical parameter in which the anatomical structure subset data can be determined; f) determining, based on the optical parameter data and the optical parameter interval data, whether the value of the optical parameter lies in the interval, g) determining, if it is determined that the value of the optical parameter lies in the interval, interval indication data describing information to be output to a user indicating whether the optical parameter lies in the interval.