Author: Owen Thomas Dillon, Andrew Kanawati, Tess Reynolds 👨🔬
Affiliation: Westmead Hospital, Image X Institute, Faculty of Medicine and Health, The University of Sydney 🌍
Purpose: Metal artefacts from implanted hardware and surgical tools remain a limitation for widespread adoption of intraoperative CBCT imaging. Gantry-based non-circular imaging trajectories have emerged as a promising solution to reduce metal artifacts by increasing sampling completeness around implanted hardware/surgical tools. However, to implement non-circular trajectories on clinical systems additional real-time control hardware is required and image reconstruction can take hours. Here, we consider table-based non-circular imaging trajectories using only in-built acquisition protocols and tools available on a clinical robotic C-arm system to deliver rapid metal artifact reduction around pedicle screws implanted in the spine.
Methods: Three thoracic (T1,T2,T9) and one lumbar (L4) vertebra, derived from human cadavers were 3D-printed with solid and custom gyroid infills and implanted with 5.5 mm diameter pedicle screws. To assist with image quality quantification radial line-pairs were 3D-printed from PLA and placed next to the vertebra as well as individual pedicle screws. Conventional circular acquisitions of the vertebrae were acquired on a clinical robotic C-arm system with the table at cranial/caudal tilts of 0° (conventional), -5° and +10°. Immediately following acquisition, the -5° and +10° table-tilted volumes were rigidly aligned and fused together using the system’s workstation to generate the final volume (<10s). Image quality was quantified via visual inspection and linear pixel profiles across the line-pairs.
Results: The table-tilt acquisition reduced the artefacts surrounding the pedicle screws, providing improved visualization of the gyroid infills and position of the pedicle screws within each vertebra, while also enabling all 13 spokes of the line-pair target to be individually resolved next to a pedicle screw with an average increase in intensity amplitude of 1.7 times compared to the conventional acquisition.
Conclusion: Rapid metal artifact reduction is achievable using twin table-tilt imaging on a clinical robotic C-arm system with no additional real-time control hardware or external post-processing.