An ultrasonic medical system comprising a tracking probe and a catheter is used for tracking a target inside human body. The ultrasonic probe has additional ultrasound sensors embedded around its main transducer array. A catheter is built with ultrasound transmitters at its distal end and sends active sound signals during each probe scanning cycle. The probe sensors track the 3D position of the target catheter using triangulation principle. The target position is rendered in the 3D anatomic context defined by the ultrasound images.