title: Augmented reality visualization with image overlay for MRI-guided intervention: accuracy for lumbar spinal procedures with a 1.5-T MRI system.
abstract: OBJECTIVE
  The purpose of this study was to prospectively evaluate the accuracy of an augmented reality image overlay system in MRI-guided spinal injection procedures.
  
  
  METHODS
  An augmented reality prototype was used in conjunction with a 1.5-T MRI system. A human lumbar spine phantom was used in which 62 targets were punctured to assess the accuracy of the system. Sixty anatomic targets (facet joint, disk space, and spinal canal) were punctured to assess how the accuracy of the system translated into practice. A visualization software interface was used to compare planned needle paths and final needle locations on coregistered CT images (standard of reference). Outcome variables included entry error, angle error, depth error, target error, successful access of anatomic targets, number of needle adjustments, and time requirements.
  
  
  RESULTS
  Accuracy assessments showed entry error of 1.6 ± 0.8 mm, angle error of 1.6° ± 1.0°, depth error of 0.7 ± 0.5 mm, and target error of 1.9 ± 0.9 mm. All anatomic targets (60 of 60 insertions) were successfully punctured, including all 20 facet joints, all 20 disks, and all 20 spinal canals. Four needle adjustments (6.7%) were required. Planning of a single needle path required an average of 55 seconds. A single needle insertion required an average of 1 minute 27 seconds.
  
  
  CONCLUSIONS
  The augmented reality image overlay system evaluated facilitated accurate MRI guidance for successful spinal procedures in a lumbar spine model. It exhibited potential for simplifying the current practice of MRI-guided lumbar spinal injection procedures.
authors.affiliation: Musculoskeletal Division, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, 601 N Caroline St, JHOC 5165, Baltimore, MD 21287, USA.
authors.forename: Jan
authors.initials: J
authors.lastname: Fritz
authors.forename: Paweena
authors.initials: P
authors.lastname: U-Thainual
authors.forename: Tamas
authors.initials: T
authors.lastname: Ungi
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Flammang
authors.forename: Nathan B
authors.initials: NB
authors.lastname: Cho
authors.forename: Gabor
authors.initials: G
authors.lastname: Fichtinger
authors.forename: Iulian I
authors.initials: II
authors.lastname: Iordachita
authors.forename: John A
authors.initials: JA
authors.lastname: Carrino
mesh_terms: D000465:Algorithms; D000704:Analysis of Variance; D002138:Calibration; D004867:Equipment Design; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007278:Injections, Spinal / Q000379:methods*; D016014:Linear Models; D050866:Liquid Crystals; D008159:Lumbar Vertebrae; D053783:Magnetic Resonance Imaging, Interventional / Q000379:methods*; D019047:Phantoms, Imaging; D011446:Prospective Studies; D012984:Software; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D014584:User-Computer Interface