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Feasibility of 3D tracking of surgical tools using 2D single plane x-ray projections

Fluoroscopy is widely used for intra-procedure image guidance, however its planar images provide limited information about the location of the surgical tools or targets in three-dimensional space. An iterative method based on the projection-Procrustes technique can determine the three-dimensional positions and orientations of known sparse objects from a single, perspective projection. We assess the feasibility of applying this technique to track surgical tools by measuring its accuracy and precision through in vitro experiments. Two phantoms were fabricated to perform this assessment: a grid plate phantom with numerous point-targets at regular distances from each other; and a sparse object used as a surgical tool phantom. Two-dimensional projections of the phantoms were acquired using an image intensifier-based C-arm x-ray unit. The locations of the markers projected onto the images were identified and measured using an automated algorithm. The three-dimensional location of the phantom tool tip was identified from these images using the projection-Procrustes technique. The accuracy and precision of the tip localization were used to assess our technique. The average three-dimensional root-mean-square target registration error of the phantom tool tip was 1.8 mm. The average three-dimensional root-mean-square precision of localizing the tool tip was 0.5 mm.