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Augmented Reality System for Ultrasound Guidance of Transcatheter Aortic Valve Implantation
Maria E. Currie, MD1, A. Jonathan McLeod2, John T. Moore3, Rajni Patel, PhD4, Bob Kiaii, MD1, Michael W. A. Chu, MD1, Terry M. Peters, PhD3.
1London Heath Sciences Centre, London, ON, Canada, 2Western University, London, ON, Canada, 3Robarts Research Institute, London, ON, Canada, 4Canadian Surgical Technologies & Advanced Robotics, London, ON, Canada.

OBJECTIVE: Transcatheter aortic valve implantation (TAVI) relies on fluoroscopy and nephrotoxic contrast medium for valve deployment. We propose an alternative guidance system using augmented reality and real-time transesophogeal echocardiography (TEE) to visualize the location of the tracked valve stent and intraoperatively defined cardiac anatomy.
The purpose of this study was to evaluate the targeting accuracy of transapical TAVI deployment using this augmented reality imaging platform in a model of the aortic root.
METHODS: Magnetic tracking sensors were integrated into the TAVI catheter and TEE probe, allowing these tools to be displayed in an augmented reality environment. The TAVI valve was deployed five times at a specified depth using a transapical approach. Once deployed, the difference between the intended depth of deployment and the operator’s depth of deployment as measured by the guidance system was recorded as the deployment error. The actual depth of deployment from the aortic valve annulus was measured using calipers. Finally, the difference between the actual depth of deployment and the depth recorded by the guidance system was also reported.
RESULTS: The deployment errors as measured by the guidance system ranged from -2.7mm to 2.2mm with a mean absolute value of 1.6mm and standard deviation (SD) 1.0mm. This error reflects the motion of the balloon catheter as the valve stent is deployed. The actual depth of deployment deviated from the target depth of 8mm by -4.2mm to 1.6mm with a mean absolute value of 1.7mm (SD 1.5mm). Finally, the difference between the actual depth of deployment and the depth recorded by the guidance system ranged from 0.5mm to 1.5mm with a mean of 1.0mm and (SD 0.4mm).
CONCLUSIONS: This study presents the feasibility of an image guidance system for TAVI placement to visualize both the TAVI stent and the critical aortic anatomy without exposure to contrast medium and ionizing radiation. The phantom and ex vivo studies indicate that clinically acceptable targeting errors on the order of 1.5 mm are achievable.


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