Machine learning for automated 3-dimensional segmentation of the spine and suggested placement of pedicle screws based on intraoperative cone-beam computer tomography

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The goal of this study was to develop and validate a system for automatic segmentation of the spine, pedicle identification, and screw path suggestion for use with an intraoperative 3D surgical navigation system.


Cone-beam CT (CBCT) images of the spines of 21 cadavers were obtained. An automated model-based approach was used for segmentation. Using machine learning methodology, the algorithm was trained and validated on the image data sets. For measuring accuracy, surface area errors of the automatic segmentation were compared to the manually outlined reference surface on CBCT. To further test both technical and clinical accuracy, the algorithm was applied to a set of 20 clinical cases. The authors evaluated the system’s accuracy in pedicle identification by measuring the distance between the user-defined midpoint of each pedicle and the automatically segmented midpoint. Finally, 2 independent surgeons performed a qualitative evaluation of the segmentation to judge whether it was adequate to guide surgical navigation and whether it would have resulted in a clinically acceptable pedicle screw placement.


The clinically relevant pedicle identification and automatic pedicle screw planning accuracy was 86.1%. By excluding patients with severe spinal deformities (i.e., Cobb angle > 75° and severe spinal degeneration) and previous surgeries, a success rate of 95.4% was achieved. The mean time (± SD) for automatic segmentation and screw planning in 5 vertebrae was 11 ± 4 seconds.


The technology investigated has the potential to aid surgeons in navigational planning and improve surgical navigation workflow while maintaining patient safety.

ABBREVIATIONS CBCT = cone-beam CT; IQR = interquartile range; MaxDist = maximum distance; OR = operating room; RMSDist = root-mean-squared distance.

Article Information

Correspondence Gustav Burström: Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.

INCLUDE WHEN CITING Published online March 22, 2019; DOI: 10.3171/2018.12.SPINE181397.

Disclosures C.B., J.H., R.N., C.L., D.B., R.H., and M.G. are employed by Philips Research and/or Philips Healthcare, which has a vested interest in the product in this manuscript. The authors report that Karolinska University Hospital and Philips Healthcare have a major collaboration agreement. Dr. Racadio reports that Cincinnati Children’s Hospital Medical Center Department of Radiology has a Master Research Agreement with Philips Medical.

© AANS, except where prohibited by US copyright law.



  • View in gallery

    A visualization of how the software identifies the vertebrae by a 3-step process, showing the application of the generalized Hough transform (A), the parametric adaptation improving the global alignment (B), and the deformable adaptation finalizing the local alignment (C). Figure is available in color online only.

  • View in gallery

    Visualization of the automatic pedicle identification and screw placement suggestion in axial (A) and sagittal (B) views and the visualization of the segmented vertebral section including screw suggestion (C). Figure is available in color online only.

  • View in gallery

    Illustration of midpoint measurements. The distance (in red) from the midpoint of each pedicle (in brown) to the midpoint of the corresponding segmented 3D reconstruction of the pedicle (in blue) in the same coronal plane was measured for all segmented pedicles. Figure is available in color online only.

  • View in gallery

    The number of segmented pedicles in each patient separated by correct or incorrect identification. Patients with any of the exclusion criteria present are indicated by pound signs (#). Figure is available in color online only.

  • View in gallery

    Distribution of distances between the algorithm-suggested pedicle midpoint and the actual manually defined pedicle midpoint. Deviation distances are stratified by correct or incorrect pedicle identification and median (solid vertical line) and quartiles (dashed vertical lines) are highlighted. Figure is available in color online only.


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