Augmented reality system for MRI-guided interventions: a cadaver study

Implementation of MRI guidance in place of CT or X-ray would reduce ionizing radiation exposure and provide better soft tissue contrast in a wide range of musculoskeletal targets in children. We developed an augmented reality guidance system for MRI-guided interventions. The purpose of this study was to evaluate the feasibility of using this system to target shoulder, hip, sacroiliac joints and liver in a cadaver. The LUMENA AR system is designed to operate in an interventional MRI suite. Specially designed fiducial markers placed on the skin surface and needle hub are used to track needle position in real-time during advancement. T1-weighted images acquired after fiducial placement allow interventional radiologists to plan optimal needle paths to selected targets by choosing skin entry and target points on an in-room planning console. Two interventional radiologists placed 12 needles along planned trajectories by following the guidance plan projected onto the skin by the optical head. Each MRI scan required approximately 2 min, and each insertion was completed within 1 minute. "User error" was defined as the distance between final needle tip location and selected target after insertion. "Overall error" was calculated as the distance between the selected target and postinsertion MRI-derived needle tip locations. All errors were reported as average ± standard deviation across all locations. Overall, 12 locations were targeted (3 shoulder, 4 hip, 1 liver, and 4 SI joint). The system operated as expected and all needles were placed successfully. User error was 2.4±1.1 mm (range: 0.8 – 4.2 mm). Overall targeting error was 2.6±0.6 mm (range: 1.5 – 3.6 mm). The study demonstrates feasibility of using augmented reality to place needles under MRI guidance in a cadaver. The system was subjectively judged to be easy to use and to fit within the established clinical workflow of image-guided needle-based interventions.