Proceedings Article | 17 February 2012
S. Reaungamornrat, Y. Otake, A. Uneri, S. Schafer, D. Mirota, S. Nithiananthan, J. W. Stayman, A. J. Khanna, D. Reh, G. Gallia, R. Taylor, J. Siewerdsen
Proc. SPIE. 8316, Medical Imaging 2012: Image-Guided Procedures, Robotic Interventions, and Modeling
KEYWORDS: X-ray computed tomography, Visualization, Surgery, Video, X-rays, Radiography, Image registration, Optical tracking, Fluoroscopy, Spine
Conventional surgical tracking configurations carry a variety of limitations in line-of-sight, geometric accuracy, and
mismatch with the surgeon's perspective (for video augmentation). With increasing utilization of mobile C-arms,
particularly those allowing cone-beam CT (CBCT), there is opportunity to better integrate surgical trackers at bedside to
address such limitations. This paper describes a tracker configuration in which the tracker is mounted directly on the Carm.
To maintain registration within a dynamic coordinate system, a reference marker visible across the full C-arm
rotation is implemented, and the "Tracker-on-C" configuration is shown to provide improved target registration error
(TRE) over a conventional in-room setup - (0.9±0.4) mm vs (1.9±0.7) mm, respectively. The system also can generate
digitally reconstructed radiographs (DRRs) from the perspective of a tracked tool ("x-ray flashlight"), the tracker, or the
C-arm ("virtual fluoroscopy"), with geometric accuracy in virtual fluoroscopy of (0.4±0.2) mm. Using a video-based
tracker, planning data and DRRs can be superimposed on the video scene from a natural perspective over the surgical
field, with geometric accuracy (0.8±0.3) pixels for planning data overlay and (0.6±0.4) pixels for DRR overlay across all
C-arm angles. The field-of-view of fluoroscopy or CBCT can also be overlaid on real-time video ("Virtual Field Light")
to assist C-arm positioning. The fixed transformation between the x-ray image and tracker facilitated quick, accurate
intraoperative registration. The workflow and precision associated with a variety of realistic surgical tasks were
significantly improved using the Tracker-on-C - for example, nearly a factor of 2 reduction in time required for C-arm
positioning, reduction or elimination of dose in "hunting" for a specific fluoroscopic view, and confident placement of
the x-ray FOV on the surgical target. The proposed configuration streamlines the integration of C-arm CBCT with realtime
tracking and demonstrated utility in a spectrum of image-guided interventions (e.g., spine surgery) benefiting from
improved accuracy, enhanced visualization, and reduced radiation exposure.
