The invention relates to a medical system for use in interventional radiology, adapted to be coupled to a navigation system, comprising:a needle (1) to be inserted into a patient's body toward a target, said needle comprising a distal tip (10) and a proximal stop (110)；a needle guide (2), the needle (1) being able to slide within said guide (2) along a longitudinal axis thereof, said needle guide (2) comprising a tracker for navigating the needle guide (2) with respect to a 3D medical image of a patient ；a processor configured to detect a contact between the needle guide (2) and the proximal stop (110) and to determine, from navigation data of the needle guide when said needle guide (2) is in contact with the proximal stop (110) of the needle and from the length of said needle, a position of the distal needle tip (10) with respect to the 3D medical image； anda user interface coupled to said processor and configured to display, on at least one image (I) of the patient, a representation of the needle and a point on said representation of the needle to represent the needle tip (10) in said determined position.
