“…Displaying the trajectory of the surgical tool in 2.5/3D was a useful aid to the surgeon even if the accuracy was not much better than a few millimetres. Today, CAS has become popular in a variety of surgical fields including cranio-and maxillo facial surgery, ENT (ear, nose and throat) surgery, orthopaedic surgery, cardiac surgery, laparoscopy, interventional radiology and several other surgical disciplines [2].…”