Experimental Visualization of Vascular Structures with Microsoft Hololens – Set-Up for Navigated Contrast Agent and Radiation-Sparing Endovascular Procedures (NAV-CARS EVAR)

Introduction - Over the last two decades, endovascular therapy has become an integral part of vascular surgery. One of the most difficulty in learning and performing this minimally invasive therapy is the fact, the vascular surgeon has to mentally overlay the three-dimensional vascular tree with the two-dimensional angiographic scene. While endovascular techniques are improving, the imaging during the procedure is still dependent on contrast agents and X-Rays with their known disadvantages. Looking at actual development trends towards radiation free localization of endovascular tools, the visualization and proper integration of this spatial information will become a key technology.
Methods - We report the development of a real-time navigation software, which allows a three-dimensional view of the vascular system without any need of radiation. We used a vascular phantom model (Blue phantom FAST Trauma Full Torso Ultrasound Training Model) and an augmented reality (AR) headset (Microsoft HoloLens) to display the vascular structures in the field of view of the surgeon. Using simple landmark-based surface registration of a CT scan and marching cubes segmentation of the vessel tree, it is straightforward to visualize both the surface and the vessels in the AR display. Using a magnetic tracking system (i.e. AURORA, Northern Digital Inc.) it is possible to also display the position and orientation of a catheter inside the vessels.
Results - Our preliminary results of the virtual real time navigation in endovascular procedures are promising. The presented technique allows a three-dimensional holographic view of the vascular system without any need of radiation. Using extrinsic landmark-based calibrations, the virtual objects are precisely aligned with the real world, resulting in a convincing holographic illusion. The prototype also offers the possibility of intervention planning and simulation, which in turn will lead to a reduced learning curve and therefore increased patient safety.
Conclusion - The “virtual angioscope” may improve intraoperative visualization, placement of guide-wires and stents. It may reduce the amount of contrast agents and exposure to X-rays.