title: Automatic localization of target vertebrae in spine surgery: clinical evaluation of the LevelCheck registration algorithm.
abstract: METHODS
  A 3-dimensional-2-dimensional (3D-2D) image registration algorithm, "LevelCheck," was used to automatically label vertebrae in intraoperative mobile radiographs obtained during spine surgery. Accuracy, computation time, and potential failure modes were evaluated in a retrospective study of 20 patients.
  
  
  OBJECTIVE
  To measure the performance of the LevelCheck algorithm using clinical images acquired during spine surgery.
  
  
  BACKGROUND
  In spine surgery, the potential for wrong level surgery is significant due to the difficulty of localizing target vertebrae based solely on visual impression, palpation, and fluoroscopy. To remedy this difficulty and reduce the risk of wrong-level surgery, our team introduced a program (dubbed LevelCheck) to automatically localize target vertebrae in mobile radiographs using robust 3D-2D image registration to preoperative computed tomographic (CT) scan.
  
  
  METHODS
  Twenty consecutive patients undergoing thoracolumbar spine surgery, for whom both a preoperative CT scan and an intraoperative mobile radiograph were available, were retrospectively analyzed. A board-certified neuroradiologist determined the "true" vertebra levels in each radiograph. Registration of the preoperative CT scan to the intraoperative radiograph was calculated via LevelCheck, and projection distance errors were analyzed. Five hundred random initializations were performed for each patient, and algorithm settings (viz, the number of robust multistarts, ranging 50-200) were varied to evaluate the trade-off between registration error and computation time. Failure mode analysis was performed by individually analyzing unsuccessful registrations (>5 mm distance error) observed with 50 multistarts.
  
  
  RESULTS
  At 200 robust multistarts (computation time of ∼26 s), the registration accuracy was 100% across all 10,000 trials. As the number of multistarts (and computation time) decreased, the registration remained fairly robust, down to 99.3% registration accuracy at 50 multistarts (computation time ∼7 s).
  
  
  CONCLUSIONS
  The LevelCheck algorithm correctly identified target vertebrae in intraoperative mobile radiographs of the thoracolumbar spine, demonstrating acceptable computation time, compatibility with routinely obtained preoperative CT scans, and warranting investigation in prospective studies.
  
  
  METHODS
  N/A.
authors: *Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, MD †Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD ‡Siemens Healthcare, Erlangen, Germany; and §The Russell H. Morgan Department of Radiology, Johns Hopkins University, Baltimore, MD.
authors: Sheng-Fu L
authors: SF
authors: Lo
authors: Yoshito
authors: Y
authors: Otake
authors: Varun
authors: V
authors: Puvanesarajah
authors: Adam S
authors: AS
authors: Wang
authors: Ali
authors: A
authors: Uneri
authors: Tharindu
authors: T
authors: De Silva
authors: Sebastian
authors: S
authors: Vogt
authors: Gerhard
authors: G
authors: Kleinszig
authors: Benjamin D
authors: BD
authors: Elder
authors: C Rory
authors: CR
authors: Goodwin
authors: Thomas A
authors: TA
authors: Kosztowski
authors: Jason A
authors: JA
authors: Liauw
authors: Mari
authors: M
authors: Groves
authors: Ali
authors: A
authors: Bydon
authors: Daniel M
authors: DM
authors: Sciubba
authors: Timothy F
authors: TF
authors: Witham
authors: Jean-Paul
authors: JP
authors: Wolinsky
authors: Nafi
authors: N
authors: Aygun
authors: Ziya L
authors: ZL
authors: Gokaslan
authors: Jeffrey H
authors: JH
authors: Siewerdsen
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001331:Automation; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007430:Intraoperative Care; D008159:Lumbar Vertebrae; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013131:Spine / Q000000981:diagnostic imaging* / Q000601:surgery*; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013904:Thoracic Vertebrae; D014057:Tomography, X-Ray Computed
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