Purpose. Intraoperative 2D virtual long-film (VLF) imaging is investigated for 3D guidance and confirmation of the surgical
product in spinal deformity correction. Multi-slot-scan geometry (rather than a single-slot “topogram”) is exploited
to produce parallax views of the scene for accurate 3D colocalization from a single radiograph.
Methods. The multi-slot approach uses additional angled collimator apertures to form fan-beams with disparate views
(parallax) of anatomy and instrumentation and to extend field-of-view beyond the linear motion limits. Combined with a
knowledge of surgical implants (pedicle screws and/or spinal rods modeled as “known components”), 3D-2D image registration
is used to solve for pose estimates via optimization of image gradient correlation. Experiments were conducted in
cadaver studies emulating the system geometry of the O-arm (Medtronic, Minneapolis MN).
Results. Experiments demonstrated feasibility of multi-slot VLF and quantified the geometric accuracy of 3D-2D registration
using VLF acquisitions. Registration of pedicle screws from a single VLF yielded mean target registration error of
(2.0±0.7) mm, comparable to the accuracy of surgical trackers and registration using multiple radiographs (e.g., AP and
LAT).
Conclusions. 3D-2D registration in a single VLF image offers a promising new solution for image guidance in spinal
deformity correction. The ability to accurately resolve pose from a single view absolves workflow challenges of multiple-view
registration and suggests application beyond spine surgery, such as reduction of long-bone fractures.
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