Fig. 1.

Procedural workflow and AR components. A Phantom in the CT gantry. Inset shows the 3D reference marker containing fiducial markers at all eight corners (red arrows). B CT scan DICOM images are sent to the AR software, and the 3D reference marker is transformed into CT coordinates. The targets (white arrow) and entry points (yellow arrow) are planned on the software, and the desired trajectories (arrowhead) are generated. The AR guidance is then transferred to the smartphone application. C Smartphone screen with an intentionally off-axis needle placement. A dropdown menu (white box, top left) allows selection of preplanned targets. The smartphone continuously transforms the virtual trajectory relative to the 3D reference marker as the phone is moved and superimposes the trajectory on the image. The AR needle virtual trajectory (green line), target (red dot), entry point (yellow dot), and depth marker (navy dot) are components of the smartphone overlay display. When the needle hub base (arrowhead) coincides with the virtual depth marker (navy dot), the needle has been inserted to its proper depth. Note that the yellow dot shown has been added to the image for illustrative purposes (C, D). While the dot was clearly visible within the AR software during use, it was difficult to discern in the screen capture shown. D Smartphone screen displaying a well-aligned needle. The needle is being advanced along its planned AR trajectory, as indicated by the alignment of the needle and AR trajectories. The inset shows a bull’s-eye view, in which the AR needle trajectory, target marker (red dot), and depth marker (navy dot) are all superimposed in the center of the needle hub (arrowhead)