HoloLens augmented reality system for transperineal free-hand prostate procedures

An augmented reality (AR) system was developed to facilitate free-hand real-time needle guidance for transperineal prostate (TP) procedures and to overcome the limitations of a traditional guidance grid.

The HoloLens AR system enables the superimposition of annotated anatomy derived from preprocedural volumetric images onto a patient and addresses the most challenging part of free-hand TP procedures by providing real-time needle tip localization and needle depth visualization during insertion. The AR system accuracy, or the image overlay accuracy ( $n=56$ ), and needle targeting accuracy ( $n=24$ ) were evaluated within a 3D-printed phantom. Three operators each used a planned-path guidance method ( $n=4$ ) and free-hand guidance ( $n=4$ ) to guide needles into targets in a gel phantom. Placement error was recorded. The feasibility of the system was further evaluated by delivering soft tissue markers into tumors of an anthropomorphic pelvic phantom via the perineum.

The image overlay error was $1.29\pm 0.57\mathrm{mm}$ , and needle targeting error was $2.13\pm 0.52\mathrm{mm}$ . The planned-path guidance placements showed similar error compared to the free-hand guidance ( $4.14\pm 1.08\mathrm{mm}$ versus $4.20\pm 1.08\mathrm{mm}$ , $p=0.90$ ). The markers were successfully implanted either into or in close proximity to the target lesion.

The HoloLens AR system can provide accurate needle guidance for TP interventions. AR support for free-hand lesion targeting is feasible and may provide more flexibility than grid-based methods, due to the real-time 3D and immersive experience during free-hand TP procedures.