title: Low-Dose Radiation 3D Intraoperative Imaging: How Low Can We Go? An O-Arm, CT Scan, Cadaveric Study.
abstract: MINI: The objective of this study was to evaluate the accuracy and reliability of pedicle screw placement using O-Arm at dosages below the manufactured recommended dose. O-Arm at reduced dose showed a 90% accuracy when compared with computed tomography; however, about 30% medial breaches were misclassified.
  
  
  METHODS
  Cadaveric study.
  
  
  OBJECTIVE
  The objective was to evaluate O-Arm's ability at low-dose (LD) settings to assess intraoperative screw placement.
  
  
  BACKGROUND
  Accurate placement of pedicle screws is crucial because of proximity to vital structures. Malposition of screws may result in significant morbidity and potential mortality. O-arm provides real-time, intraoperative imaging of patient's anatomy and provides higher accuracy in scoliosis surgeries, avoiding risk to vital structures. We hypothesize using LD or ultra-low doses (ULDs) to obtain intraoperative images allow for accurate assessment of screw placement, both minimizing radiation exposure and preventing screw misplacement.
  
  
  METHODS
  Eight cadavers were instrumented with pedicle screws bilaterally from T1 to S1. Screws were randomly placed using O-arm navigation into three positions: contained within the bone, OUT-anterior/lateral, and OUT-medial. O-arm images were obtained at three dosage settings: LD (kVp120/mAs125-lowest manufacturer recommended), very-low dose (VLD) (kVp120/mAs63), and ULD (kVp120/mAs39). Computed tomography (CT) scan was performed using institution's LD protocol (kVp100/mAs50) and gross dissection to identify screw positions.
  
  
  RESULTS
  LD, VLD, ULD, and CT for identifying "IN" screws relative to gross dissection had, a mean (standard deviation) sensitivity of 84.2% (±5.7), specificity of 76.1% (±9.3), and accuracy of 79.9% (±3.1) from all three observers. Across the three observers, the interobserver agreement was 0.67 (0.61-0.72) for LD, 0.74 (0.69-0.79) for VLD, 0.61 (0.56-0.66) for ULD, and 0.79 (0.74-0.84) for CT. Effective doses of radiation (mSV) for LD O-arm scan was 2.16, VLD 1.08, ULD 0.68, and our LD CT protocol was 1.05.
  
  
  CONCLUSIONS
  Accuracy of pedicle screw placement is similar for O-arm at all doses and CT compared to gross dissection. Interobserver reliability was substantial for VLD and CT. Approximately 30% of medial screw breaches are, however, misclassified. ULD and VLDs can be used for intraoperative navigation and evaluation purposes within these limitations.
  
  
  METHODS
  N/A.
authors.affiliation: Department of Pediatric Orthopedics, Cohen Children's Medical Center, Northwell Health System, New Hyde Park, NY.
authors.forename: Vishal
authors.initials: V
authors.lastname: Sarwahi
authors.affiliation: Orthopedic Surgery Program, Nicklaus Children's Hospital, Miami Children's Health Network, Miami, FL.
authors.forename: Monica
authors.initials: M
authors.lastname: Payares
authors.affiliation: Department of Pediatric Orthopedics, Cohen Children's Medical Center, Northwell Health System, New Hyde Park, NY.
authors.forename: Stephen
authors.initials: S
authors.lastname: Wendolowski
authors.affiliation: Department of Orthopaedic Surgery, Montefiore Medical Center, Bronx, NY.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Maguire
authors.affiliation: Department of Radiology, Montefiore Medical Center, Bronx, NY.
authors.forename: Beverly
authors.initials: B
authors.lastname: Thornhill
authors.affiliation: Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, NY.
authors.forename: Yungtai
authors.initials: Y
authors.lastname: Lo
authors.affiliation: Department of Pediatric Orthopedics, Cohen Children's Medical Center, Northwell Health System, New Hyde Park, NY.
authors.forename: Terry D
authors.initials: TD
authors.lastname: Amaral
mesh_terms: D002102:Cadaver; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods / Q000592:standards*; D008297:Male; D016343:Monitoring, Intraoperative / Q000295:instrumentation / Q000379:methods / Q000592:standards*; D065289:Pedicle Screws / Q000009:adverse effects / Q000592:standards*; D000069079:Radiation Exposure / Q000009:adverse effects / Q000592:standards*; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods / Q000592:standards*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods / Q000592:standards*