Fig 3. Schematic drawing of the real-time needle guidance with the MPT system.

Two perpendicular imaging planes were aligned along the needle trajectory and centered at the needle tip. The additional graphical overlay contains information about the 3D distance $d_{3D}=\sqrt{\Delta x^2+\Delta y^2+\Delta z^2}$ between the needle tip and the predefined target as well as the 2D distance of $d_{2D}=\sqrt{\Delta x^2+\Delta z^2}$.