SURGERY SPINE Volume 38, Number 5, pp E306–E312 ©2013, Lippincott Williams & Wilkins E306 www.spinejournal.com March 2013 Estimating the Effective Radiation Dose Imparted to Patients by Intraoperative Cone-Beam Computed Tomography in Thoracolumbar Spinal Surgery Jeffrey Lange, MD,* Andrew Karellas, PhD,† John Street, MD, PhD,‡ Jason C. Eck, DO,MS,* Anthony Lapinsky, MD,* Patrick J. Connolly, MD,* and Christian P. DiPaola, MD* Study Design. Observational. Objective. To estimate the radiation dose imparted to patients during typical thoracolumbar spinal surgical scenarios. Summary of Background Data. Minimally invasive techniques continue to become more common in spine surgery. Computer- assisted navigation systems coupled with intraoperative cone-beam computed tomography (CT) represent one such method used to aid in instrumented spinal procedures. Some studies indicate that cone- beam CT technology delivers a relatively low dose of radiation to patients compared with other x-ray–based imaging modalities. The goal of this study was to estimate the radiation exposure to the patient imparted during typical posterior thoracolumbar instrumented spinal procedures, using intraoperative cone-beam CT and to place these values in the context of standard CT doses. Methods. Cone-beam CT scans were obtained using Medtronic O-arm (Medtronic, Minneapolis, MN). Thermoluminescence dosimeters were placed in a linear array on a foam-plastic thoracolumbar spine model centered above the radiation source for O-arm presets of lumbar scans for small or large patients. In- air dosimeter measurements were converted to skin surface measurements, using published conversion factors. Dose-length product was calculated from these values. Effective dose was estimated using published effective dose to dose-length product conversion factors. Results. Calculated dosages for many full-length procedures using the small-patient setting fell within the range of published effective M inimally invasive techniques continue to become more common in spine surgery. These approaches have the theoretical advantages of limited soft- tissue dissection, relatively little blood loss, maintenance of soft-tissue integrity, and therefore closer-to-normal postop- erative spine biomechanics. 1 In addition, minimally invasive approaches may have the disadvantages of limited exposure, steep learning curves, and the potential for increased surgical time. 1 Some minimally invasive approaches in spine surgery have been coupled to 3-dimensional image-guided technolo- gies in an effort to improve the accuracy of instrumentation placement. Multiple studies have reported that relatively high rates of accuracy of pedicle screw placement can be achieved by using 3-dimensional image-guided technology in posterior spinal instrumentation procedures. 2 –6 For instance, Smith et al 2 demonstrated a pedicle breach rate of 8% (2/24 lumbar or SI screws placed) using 3-dimensional image-guided fluoros- copy versus a pedicle breach rate of 33% (8/24 pedicles) using traditional fluoroscopy Bledsoe et al 3 demonstrated a pedicle breach rate of 7% (10/150 screws placed) in upper thoracic pedicles using 3-dimensional image guidance. Nottmeier From the Departments of *Orthopedic Surgery and †Radiology, University of Massachusetts Medical School, Worcester, MA; and ‡Department of Orthopedic Surgery, University of British Columbia, Vancouver, British Columbia, Canada. Acknowledgment date: July 29, 2011. Revision date: October 2, 2012. Acceptance date: December 6, 2012. The device(s)/drug(s) is/are FDA-approved or approved by corresponding national agency for this indication. Research support was received from Medtronic. The Department of Orthopedics, University of Massachusetts Medical School, has received research grants from K2M and Apatech. Relevant financial activities outside the submitted work: consultancy. Address correspondence and reprint requests to Jeffrey Lange, MD, Department of Orthopedic Surgery, University of Massachusetts Medical School, 55 Lake Ave N, Worcester, MA 01655; E-mail: jeffrey.lange2@umassmemorial.org doses of abdominal CT scans (1–31 mSv). Calculated dosages for many full-length procedures using the large-patient setting fell within the range of published effective doses of abdominal CT scans when the number of scans did not exceed 3. Conclusion. We have demonstrated that single cone-beam CT scans and most full-length posterior instrumented spinal procedures using O-arm in standard mode would likely impart a radiation dose within the range of those imparted by a single standard CT scan of the abdomen. Radiation dose increases with patient size, and the radiation dose received by larger patients as a result of more than 3 O-arm scans in standard mode may exceed the dose received during standard CT of the abdomen. Understanding radiation imparted to patients by cone-beam CT is important for assessing risks and benefits of this technology, especially when spinal surgical procedures require multiple intraoperative scans. Key words: radiation exposure, cone-beam CT, intraoperative CT, surgical navigation. Spine 2013;38:E306–E312 DOI: 10.1097/BRS.0b013e318281d70b Copyright © 2013 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.