1. A method for three-dimensional presentation of an examination region of a patient as a 3D reconstruction image, comprising the steps of: employing a preoperatively acquired 3D image dataset of an examination region; acquiring a plurality of 2D ultrasound images of said examination region contemporaneously with a medical procedure involving said examination region; updating the preoperatively acquired 3D image dataset using said 2D ultrasound images, thereby obtaining an updated 3D image dataset; and reconstructing a 3D reconstruction image from said updated 3D image dataset and using said 3D reconstruction image in said medical procedure.