1. A method for graphically assisting navigation of a medical instrument in a magnetic resonance device within a medical procedure region in a patient in the magnetic resonance device comprising the steps of: operating the magnetic resonance device with the patient therein to obtain a high-contrast image data set representing said procedure region; supplying said high-contrast image data set to a computerized processor and, in said computerized processor, automatically determining, from said high-contrast image data set, coordinates of a target, selected from the group consisting of a target position and a target region, to be reached by the instrument in said procedure region; operating said magnetic resonance device to repeatedly acquire low-contrast image data representing said instrument during movement of said instrument in said procedure region towards said target; calibrating a position determination device to bring position determination algorithms implemented in the position determination device into registration with a coordinate system associated with the magnetic resonance device; supplying said low-contrast image data to said computerized position determination device and, in said position determination device, implementing said position determination algorithm to identify a position and orientation of said instrument relative to the coordinate system of the magnetic resonance device during said movement; and at a display device in communication with said computerized processor and said computerized position determination device, representing at least a relative position and orientation of said instrument relative to said target, using said coordinates of said target and at least one of said low-contrast image data and said position and orientation of said instrument.