title: Warning navigation system using real-time safe region monitoring for otologic surgery.
abstract: OBJECTIVE
  We developed a surgical navigation system that warns the surgeon with auditory and visual feedback to protect the facial nerve with real-time monitoring of the safe region during drilling.
  
  
  METHODS
  Warning navigation modules were developed and integrated into a free open source software platform. To obtain high registration accuracy, we used a high-precision laser-sintered template of the patient's bone surface to register the computed tomography (CT) images. We calculated the closest distance between the drill tip and the surface of the facial nerve during drilling. When the drill tip entered the safe regions, the navigation system provided an auditory and visual signal which differed in each safe region. To evaluate the effectiveness of the system, we performed phantom experiments for maintaining a given safe margin from the facial nerve when drilling bone models, with and without the navigation system. The error of the safe margin was measured on postoperative CT images. In real surgery, we evaluated the feasibility of the system in comparison with conventional facial nerve monitoring.
  
  
  RESULTS
  The navigation accuracy was submillimeter for the target registration error. In the phantom study, the task with navigation ([Formula: see text] mm) was more successful with smaller error, than the task without navigation ([Formula: see text] mm, [Formula: see text]). The clinical feasibility of the system was confirmed in three real surgeries.
  
  
  CONCLUSIONS
  This system could assist surgeons in preserving the facial nerve and potentially contribute to enhanced patient safety in the surgery.
authors.affiliation: Department of Advanced medical Initiatives, Faculty of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Byunghyun
authors.initials: B
authors.lastname: Cho
authors.forename: Masamichi
authors.initials: M
authors.lastname: Oka
authors.forename: Nozomu
authors.initials: N
authors.lastname: Matsumoto
authors.forename: Riichi
authors.initials: R
authors.lastname: Ouchida
authors.forename: Jaesung
authors.initials: J
authors.lastname: Hong
authors.forename: Makoto
authors.initials: M
authors.lastname: Hashizume
mesh_terms: D000161:Acoustic Stimulation / Q000295:instrumentation; D020220:Facial Nerve Injuries / Q000209:etiology / Q000517:prevention & control; D005240:Feasibility Studies; D056228:Feedback, Sensory; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation*; D019300:Medical Errors / Q000517:prevention & control*; D008954:Models, Biological; D016343:Monitoring, Intraoperative / Q000295:instrumentation*; D013506:Otologic Surgical Procedures / Q000009:adverse effects / Q000295:instrumentation*; D019047:Phantoms, Imaging; D010775:Photic Stimulation / Q000295:instrumentation; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*