The invention relates to a system for planning the introduction of a needle in a patient's body, comprising:a needle guide (3) intended to be coupled to a needle (2)；a navigation system configured for tracking the needle guide (3) with respect to a 3D medical image of the patient；a processor configured for determining a virtual position and orientation of the needle (2) with respect to the 3D image (1) using navigation data of the needle guide (3), for detecting at least one inserted needle (2′； 2a′, 2b′, 2c′) as a trace in the 3D medical image (1) and for computing a distance between the virtual needle (2) and the detected needle (2′； 2a′, 2b′, 2c′)；a display coupled to the processor for displaying a representation of the virtual needle (2) and a representation of the computed distance between the virtual needle and the at least one detected needle (2′； 2a′, 2b′, 2c′).
