A medical system comprises an instrument, a position acquisition apparatus, a data processing and image generating apparatus and an image display and control unit. The position acquisition apparatus is configured to acquire a position and orientation of the instrument in relation to a reference coordinate system. The data processing and image generating apparatus is configured to generate an image of a body part from currently recorded or stored data representing a body part, which image reproduces a view of the body part together with a representation of the position, and preferably also the orientation of the instrument so that an observer can gather the position and orientation of the instrument in the body part from the image of the body part.