An electromagnetic “Tracker-in-Table” configuration for X-ray fluoroscopy and cone-beam CT-guided surgery

  • J. Yoo
  • S. Schafer
  • A. Uneri
  • Y. Otake
  • A. J. Khanna
  • J. H. Siewerdsen
Original Article



A novel electromagnetic tracking configuration was characterized and implemented for image-guided surgery incorporating C-arm fluoroscopy and/or cone-beam CT (CBCT). The tracker employed a field generator (FG) with an open rectangular aperture and a frame enclosure with two essentially hollow sides, yielding a design that presents little or no X-ray attenuation across the C-arm orbit. The “Window” FG (WFG) was characterized in comparison with a conventional “Aurora” FG (AFG), and a configuration in which the WFG was incorporated directly into the operating table was investigated in preclinical phantom studies.


The geometric accuracy and field of view (FOV) of the WFG and AFG were evaluated in terms of target registration error (TRE) using an acrylic phantom on an (electromagnetic compatible) experimental bench. The WFG design was incorporated in a prototype operating table featuring a carbon fiber top beneath, which the FG could be translated for positioning under the patient. The X-ray compatibility was evaluated using a prototype mobile C-arm for fluoroscopy and CBCT in an anthropomorphic chest phantom. The susceptibility to EM field distortion associated with surgical tools (e.g., spine screws) and the C-arm itself was investigated in terms of TRE, and calibration methods were tested to provide robust image-world registration with minimal perturbation from the rotational C-arm.


The WFG demonstrated mean TRE of 1.28 ± 0.79 mm compared to 1.13 ± 0.72 mm for the AFG, with no statistically significant difference between the two (p = 0.32 and n = 250). The WFG exhibited a deeper field of view by ~10 cm providing an equivalent degree of geometric accuracy to a depth of z ~55 cm, compared to z ~45 cm for the AFG. Although the presence of a small number of spine screws did not degrade tracker accuracy, the mobile C-arm perturbed the electromagnetic field sufficiently to degrade TRE; however, a calibration method was identified to mitigate the effect. Specifically, the average calibration between posterior–anterior and lateral orientations of the C-arm was found to yield fairly robust registration for any C-arm pose with only a slight reduction in geometric accuracy (1.43 ± 0.31 mm in comparison with 1.28 ± 0.79 mm, p = 0.05). The WFG demonstrated reasonable X-ray compatibility, although the initial design of the window frame included suboptimal material and shape of the side bars that caused a level of streak artifacts in CBCT reconstructions. The streak artifacts were of sufficient magnitude to degrade soft-tissue visibility in CBCT but were negligible in the context of high-contrast imaging tasks (e.g., bone visualization).


The open frame of the WFG offers a potentially valuable configuration for electromagnetic trackers in image-guided surgery applications that are based on X-ray fluoroscopy and/or CBCT. The geometric accuracy and FOV are comparable to the conventional AFG and offers increased depth (z-direction) FOV. Incorporation directly within the operating table offers a streamlined implementation in which the tracker is in place but “invisible,” potentially simplifying tableside logistics, avoidance of the sterile field, and compatibility with X-ray imaging.


Surgical navigation Intraoperative imaging CBCT Spine surgery Electromagnetic tracking Tracking accuracy Image quality 


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  1. 1.
    Balachandran R, Fitzpatrick JM, Labadie RF (2008) Accuracy of image-guided surgical systems at the lateral skull base as clinically assessed using bone-anchored hearing aid posts as surgical targets. Otol Neurotol 29(8): 1050–1055PubMedCrossRefGoogle Scholar
  2. 2.
    Chan Y, Siewerdsen JH, Rafferty MA, Moseley DJ, Jaffray DA, Irish JC (2008) Cone-beam computed tomography on a mobile C-arm: novel intraoperative imaging technology for guidance of head and neck surgery. J Otolaryngol Head N 37(1): 81–90Google Scholar
  3. 3.
    Ishikawa Y, Kanemura T, Yoshida G, Ito Z, Muramoto A, Ohno S (2010) Clinical accuracy of three-dimensional fluoroscopy-based computer-assisted cervical pedicle screw placement: a retrospective comparative study of conventional versus computer-assisted cervical pedicle screw placement. J Neurosurg Spine 13(5): 606–611PubMedCrossRefGoogle Scholar
  4. 4.
    Hall WA, Truwit CL (2008) Intraoperative MR-guided neurosurgery. J Magn Reson Imaging 27(2): 368–375PubMedCrossRefGoogle Scholar
  5. 5.
    Holly LT, Foley KT (2003) Three-dimensional fluoroscopy-guided percutaneous thoracolumbar pedicle screw placement. Technical note. J Neurosurg 99(3 Suppl): 324–329PubMedGoogle Scholar
  6. 6.
    Holly LT, Foley KT (2007) Image guidance in spine surgery. Orthop Clin N Am 38(3): 451–461CrossRefGoogle Scholar
  7. 7.
    Khoury A, Siewerdsen JH, Whyne CM, Daly MJ, Kreder HJ, Moseley DJ, Jaffray DA (2007) Intraoperative cone-beam CT for image-guided tibial plateau fracture reduction. Comput Aided Surg 12(4): 195–207PubMedGoogle Scholar
  8. 8.
    Schafer S, Nithananiathan S, Mirota DJ, Uneri A, Stayman JW, Zbijewski W, Schmidgunst C, Kleinszig G, Khanna AJ, Siewerdsen JH (2011) Mobile C-arm cone-beam CT for guidance of spine surgery: image quality, radiation dose, and integration with interventional guidance. Med Phys 38(8): 4563–4575PubMedCrossRefGoogle Scholar
  9. 9.
    Schafer S, Otake Y, Uneri A, Mirota DJ, Nithiananthan S, Stayman JW, Zbijewski W, Kleinszig G, Graumann R, Sussman M, Siewerdsen JH (2012) High-performance C-arm cone-beam CT guidance of thoracic surgery. In: Holmes DR III, Wong KH (eds) SPIE medical imaging. SPIE, San Diego, pp 83113–83161Google Scholar
  10. 10.
    Peters T (2006) Image-guidance for surgical procedures. Phys Med Biol 51(14): R505PubMedCrossRefGoogle Scholar
  11. 11.
    Labadie RF, Davis BM, Fitzpatrick JM (2005) Image-guided surgery: what is the accuracy?. Curr Opin Otolaryngol Head Neck Surg 13(1): 27–31PubMedCrossRefGoogle Scholar
  12. 12.
    Rampersaud YR, Simon DA, Foley KT (2001) Accuracy requirements for image-guided spinal pedicle screw placement. Spine 26(4): 352–359PubMedCrossRefGoogle Scholar
  13. 13.
    Bo LE, Leira HO, Tangen GA, Hofstad EF, Amundsen T, Lango T (2012) Accuracy of electromagnetic tracking with a prototype field generator in an interventional OR setting. Med Phys 39(1): 399–406PubMedCrossRefGoogle Scholar
  14. 14.
    Frantz DD, Wiles AD, Leis SE, Kirsch SR (2003) Accuracy assessment protocols for electromagnetic tracking systems. Phys Med Biol 48(14): 2241PubMedCrossRefGoogle Scholar
  15. 15.
    Hummel J, Figl M, Birkfellner W, Bax MR, Shahidi R, C.R. Maurer J, Bergmann H (2006) Evaluation of a new electromagnetic tracking system using a standardized assessment protocol. Phys Med Biol 51(10): N205PubMedCrossRefGoogle Scholar
  16. 16.
    Nafis C, Jensen V, von Jako R (2008) Method for evaluating compatibility of commercial electromagnetic (EM) microsensor tracking systems with surgical and imaging tables. In: Miga MI, Cleary KR (eds) SPIE, San Diego, pp 691815–691820Google Scholar
  17. 17.
    Poulin F, Amiot LP (2002) Interference during the use of an electromagnetic tracking system under OR conditions. J Biomech 35(6): 733–737PubMedCrossRefGoogle Scholar
  18. 18.
    Schneider M, Stevens C (2007) Development and testing of a new magnetic-tracking device for image guidance. In: Cleary KR, Miga MI (eds) SPIE, San Diego, pp 65011–65090Google Scholar
  19. 19.
    Wilson E, Yaniv Z, Zhang H, Nafis C, Shen E, Shechter G, Wiles AD, Peters T, Lindisch D, Cleary K (2007) A hardware and software protocol for the evaluation of electromagnetic tracker accuracy in the clinical environment: a multi-center study. In: Cleary KR, Miga MI (eds) SPIE, San Diego, pp 65011–65092Google Scholar
  20. 20.
    Yaniv Z, Wilson E, Lindisch D, Cleary K (2009) Electromagnetic tracking in the clinical environment. Med Phys 36(3): 876–892PubMedCrossRefGoogle Scholar
  21. 21.
    Hummel J, Figl M, Kollmann C, Bergmann H, Birkfellner W (2002) Evaluation of a miniature electromagnetic position tracker. Med Phys 29(10): 2205–2212PubMedCrossRefGoogle Scholar
  22. 22.
    Arun KS, Huang TS, Blostein SD (1987) Least-squares fitting of two 3-D point sets. IEEE Trans Pattern Anal Mach Intell 9(5): 698–700PubMedCrossRefGoogle Scholar
  23. 23.
    Fitzpatrick JM, West JB, Maurer CR Jr (1998) Predicting error in rigid-body point-based registration. IEEE Trans Med Imaging 17(5): 694–702PubMedCrossRefGoogle Scholar
  24. 24.
    Siewerdsen JH, Moseley DJ, Burch S, Bisland SK, Bogaards A, Wilson BC, Jaffray DA (2005) Volume CT with a flat-panel detector on a mobile, isocentric C-arm: pre-clinical investigation in guidance of minimally invasive surgery. Med Phys 32(1): 241–254PubMedCrossRefGoogle Scholar
  25. 25.
    Siewerdsen JH, Daly MJ, Chan H, Nithiananthan S, Hamming N, Brock KK, Irish JC (2009) High-performance intraoperative cone-beam CT on a mobile C-arm: an integrated system for guidance of head and neck surgery. In: Miga MI, Wong KH (eds) SPIE, Lake Buena Vista, pp 72610–72618Google Scholar
  26. 26.
    Siewerdsen JH, Shkumat NA, Dhanantwari AC, Williams DB, Richard S, Daly MJ, Paul NS, Moseley DJ, Jaffray DA, Yorkston J, Metter RV (2006) High-performance dual-energy imaging with a flat-panel detector: imaging physics from blackboard to benchtop to bedside. In: Michael JF, Jiang H (eds) Proceedings of SPIE physics of medical imaging. SPIE, p 61421EGoogle Scholar
  27. 27.
    Ritter D, Orman J, Schmidgunst C, Graumann R (2007) 3D soft tissue imaging with a mobile C-arm. Comput Med Imag Grap 31(2): 91–102CrossRefGoogle Scholar
  28. 28.
    Bachar G, Barker E, Nithiananthan S, Chan H, Daly MJ, Irish JC, Siewerdsen JH (2009) Three-dimensional tomosynthesis and cone-beam computed tomography: an experimental study for fast, low-dose intraoperative imaging technology for guidance of sinus and skull base surgery. Laryngoscope 119(3): 434–441PubMedCrossRefGoogle Scholar
  29. 29.
    Bachar G, Siewerdsen JH, Daly MJ, Jaffray DA, Irish JC (2007) Image quality and localization accuracy in C-arm tomosynthesis-guided head and neck surgery. Med Phys 34(12): 4664–4677PubMedCrossRefGoogle Scholar
  30. 30.
    Barker E, Trimble K, Chan H, Ramsden J, Nithiananthan S, James A, Bachar G, Daly M, Irish J, Siewerdsen J (2009) Intraoperative use of cone-beam computed tomography in a cadaveric ossified cochlea model. Otolaryng Head Neck 140(5): 697–702CrossRefGoogle Scholar
  31. 31.
    Al-Halabi H, Portelance L, Duclos M, Reniers B, Bahoric B, Souhami L (2010) Cone beam CT-based three-dimensional planning in high-dose-rate brachytherapy for cervical cancer. Int J Radiat Oncol Biol Phys 77(4): 1092–1097PubMedCrossRefGoogle Scholar
  32. 32.
    Jaffray DA, Siewerdsen JH, Edmundson GK, Wong JW, Martinez AA (2002) Flat-panel cone-beam CT on a mobile isocentric C-arm for image-guided brachytherapy. In: Antonuk LE, Yaffe MJ (eds) SPIE, San Diego, pp 209–217Google Scholar
  33. 33.
    Lauritsch G, Boese J, Wigstrom L, Kemeth H, Fahrig R (2006) Towards cardiac C-arm computed tomography. IEEE Trans Med Imaging 25(7): 922–934PubMedCrossRefGoogle Scholar
  34. 34.
    Watanabe Y (1999) Derivation of linear attenuation coefficients from CT numbers for low-energy photons. Phys Med Biol 44(9): 2201PubMedCrossRefGoogle Scholar
  35. 35.
    Feldkamp LA, Davis LC, Kress JW (1984) Practical cone-beam algorithm. J Opt Soc Am A 1(6): 612–619CrossRefGoogle Scholar

Copyright information

© CARS 2012

Authors and Affiliations

  • J. Yoo
    • 1
  • S. Schafer
    • 1
  • A. Uneri
    • 2
  • Y. Otake
    • 2
  • A. J. Khanna
    • 1
    • 3
  • J. H. Siewerdsen
    • 1
    • 2
  1. 1.Department of Biomedical EngineeringThe Johns Hopkins UniversityBaltimoreUSA
  2. 2.Department of Computer ScienceThe Johns Hopkins UniversityBaltimoreUSA
  3. 3.Department of Orthopaedic SurgeryThe Johns Hopkins UniversityBaltimoreUSA

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