A tool navigation system employing an ultrasound probe (20), an ultrasound scanner (60), an interventional tool (30) (e.g., a needle or a catheter), a plurality of ultrasound transducers (21, 31), a tool tracker (70) and an image navigator. In operation, the ultrasound probe (20) generates an acoustic image plane for scanning an anatomical region, and the ultrasound scanner (60) generates an ultrasound image of the anatomical region from a scan of the anatomical region. During the scan, the interventional tool (30) is navigated within the anatomical region relative to the acoustic image plane, and the ultrasound transducers (21, 31) facilitate a tracks by the tool tracker (70) of a position of the interventional tool (30) relative to the acoustic image plane. The image navigator displays a graphical icon within the ultrasound image of the anatomical region as generated by the ultrasound scanner (60) for illustrating a tracking by the tool tracker (70) of a distance of the interventional tool (30) relative to the acoustic image plane. One or more aspects of the graphical icon are modulated by the image navigator responsive to the tracked distance of the interventional tool (30) relative to the acoustic image plane as the interventional tool (30) is navigated within the anatomical region.