title: Real-time computed tomography-based augmented reality for natural orifice transluminal endoscopic surgery navigation.
abstract: BACKGROUND
  Natural orifice transluminal endoscopic surgery (NOTES) is technically challenging owing to endoscopic short-sighted visualization, excessive scope flexibility and lack of adequate instrumentation. Augmented reality may overcome these difficulties. This study tested whether an image registration system for NOTES procedures (IR-NOTES) can facilitate navigation.
  
  
  METHODS
  In three human cadavers 15 intra-abdominal organs were targeted endoscopically with and without IR-NOTES via both transgastric and transcolonic routes, by three endoscopists with different levels of expertise. Ease of navigation was evaluated objectively by kinematic analysis, and navigation complexity was determined by creating an organ access complexity score based on the same data.
  
  
  RESULTS
  Without IR-NOTES, 21 (11·7 per cent) of 180 targets were not reached (expert endoscopist 3, advanced 7, intermediate 11), compared with one (1 per cent) of 90 with IR-NOTES (intermediate endoscopist) (P = 0·002). Endoscope movements were significantly less complex in eight of the 15 listed organs when using IR-NOTES. The most complex areas to access were the pelvis and left upper quadrant, independently of the access route. The most difficult organs to access were the spleen (5 failed attempts; 3 of 7 kinematic variables significantly improved) and rectum (4 failed attempts; 5 of 7 kinematic variables significantly improved). The time needed to access the rectum through a transgastric approach was 206·3 s without and 54·9 s with IR-NOTES (P = 0·027).
  
  
  CONCLUSIONS
  The IR-NOTES system enhanced both navigation efficacy and ease of intra-abdominal NOTES exploration for operators of all levels. The system rendered some organs accessible to non-expert operators, thereby reducing one impediment to NOTES procedures.
authors.affiliation: Minimally Invasive and Bariatric Surgery, Department of Surgery, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: D E
authors.initials: DE
authors.lastname: Azagury
authors.forename: M
authors.initials: M
authors.lastname: Ryou
authors.forename: S N
authors.initials: SN
authors.lastname: Shaikh
authors.forename: R
authors.initials: R
authors.lastname: San José Estépar
authors.forename: B I
authors.initials: BI
authors.lastname: Lengyel
authors.forename: J
authors.initials: J
authors.lastname: Jagadeesan
authors.forename: K G
authors.initials: KG
authors.lastname: Vosburgh
authors.forename: C C
authors.initials: CC
authors.lastname: Thompson
mesh_terms: D034861:Abdominal Wall / Q000033:anatomy & histology; D000328:Adult; D002102:Cadaver; D003198:Computer Simulation; D003199:Computer Systems; D004064:Digestive System / Q000033:anatomy & histology; D005260:Female; D006801:Humans; D008297:Male; D057605:Natural Orifice Endoscopic Surgery / Q000379:methods* / Q000592:standards; D017773:Pelvic Floor / Q000033:anatomy & histology; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000592:standards