©2015 MFMER | slide-1 How Does Patient Radiation Exposure Compare with Low Dose O-Arm vs. Fluoroscopy for Pedicle Screw Placement? a,b Alvin W. Su, MD, PhD; a,c Amy L. McIntosh, MD a Anthony A. Stans, MD; a A. Noelle Larson, MD a Dept. Orthopedic Surgery, Mayo Clinic, Rochester, MN b School of Medicine, National Yang-Ming University, Taipei, Taiwan c Dept. Orthopedic Surgery, Texas Scottish Rite Hospital for Children, Dallas, TX International Congress on Early Onset Scoliosis November 19 & 20, 2015

©2015 MFMER | slide-2 Background: Pedicle Screw Instrumentation I.O-arm (intra-OP CT scan) A.reported to improve screw accuracy [1-2] B.“pediatric protocol” minimizes radiation dose [3-4] II.C-arm (intra-OP fluoroscopy) A.well-established B.radiation dose has high variability [5-7] 1 Ledonio+ JBJS-Am 2011; 2 Larson+ JPO 2012; 3 Abul-Kasim+ J Spinal Disord Tech 2012; 4 Su+ JPO 2015; 5 Nelson+ Spine J 2013,;o+ JNS-Spine 2014; 7 Kuhne+ SOMOS 2014

©2015 MFMER | slide-3 Hypothesis Patient radiation exposure with C-arm technique is comparable to low-dose O-arm for pedicle screw placement Motivation 1.Does O-arm really generate more radiation? 2.Is O-arm safe for the young patients?

©2015 MFMER | slide-4 Matched-control cohorts: O-arm vs. C-arm year 2014 O-armC-armp value n14 n/a Diagnosis AIS (12), JIS (2) n/a Age (years) 13 (11-18)14 (12-18)0.09 B.W. (kg)57 (48-80)58 (43-86)0.60 Imaged levels 11 (6-15)11 (5-13)0.57 data: medium (range); t-test Aim: Compare total effective dose ( E Sum ) btw. O-arm vs. C-arm two centers, both IRB approved

©2015 MFMER | slide-5 O-arm® (Stealth, Medtronic) 1 Abul-Kasim+ J Spinal Disord Tech 2012; 2 Su+ JPO 2015; 3 ICRP ; O-arm effective dose = 0.65 mSv / scan Chest PA: 0.02−0.10 mSv [3] 80 kV, 20 mA, 80 mAs [1,2] 1x 7x Peds low-dose Default protocol Effective Dose

©2015 MFMER | slide-6 C-arm total effective dose by ratio of T:L, AP:LAT 1 Abul-Kasim+ J Spinal Disord Tech 2012; 2 ICRP GE OEC 9900 Elite® mobile C-arm Phantom: T7 & L3, AP & LAT Thoracic 9 levels Lumbar 2 levels Ex: If we image T4−L2 total image time  partitioned to T & L spine  converted to effective dose [1-2]

©2015 MFMER | slide-7 Results: Fluoroscopy time is variable total 26 O-arm scans two scans (n=10) one scan (n=4) 1 spin / 6 levels C-arm imaging time 35 ± 24 sec (7.9−75.0) ~19 sec / 6 levels

©2015 MFMER | slide-8 Results O-arm resulted in higher (4X) total effective dose than C-arm Chest PA X-ray mSv

©2015 MFMER | slide-9 Limitations: C-arm dose was approximated intra-OP radiographs not included ~ 0.2 (AP) & 0.7 (LAT) mSv [1] 1 Luo+ Spine Deformity 2015; 2 Brown+ Pediatr Radiol Nawfel+ Radiology 2000; 4 Perisinakis+ Radiology 2004 used phantom for C-arm dose: well recognized method for radiation dosimetry [2,3] our conversion factors ~ literature reports [4] AP+LAT 1 set Effective Dose

©2015 MFMER | slide-10 Discussion: C-arm dose has high variability Varies with patient characteristics, C-arm device type/settings / preferences Depends on surgical technique/fluoroscopy times Effective dose reported as high as 2.92 mSv [1] (3x low-dose O-arm) Total fluoroscopy time can range from sec [1,2] (35 sec in our study) 1 Perisinakis+ Spine 2004; 2 Slomczykowski+ Spine 1999

©2015 MFMER | slide-11 C-arm & pediatric O-arm are both “low dose” medical radiation exposure associated with cancer 100 mSv cumulative [4] 2.7x breast cancer death ICRP recommended occupational exposure < 50 mSv / year < 100 mSv / 5 years 1 Measurements NCoRP 2014; 2 Ul Haque+ Spine 2006; 3 Rampersaud+ Spine 2000; 4 Doody+ Spine 2000

©2015 MFMER | slide-12 Significance Pediatric orthopedic surgeons must be informed about radiation imparted to patients and surgical team One low dose O-arm = 85 s of C-arm spine fluoroscopy Total dose of C-arm depends on fluoroscopy time Both systems impart < 1 year annual background radiation to patient