The Influence of Stents on the Performance of an Ultrasonic Navigational System for Endovascular Procedures

OBJECTIVES:
Image guided surgery provides a mechanism to accurately and quickly assess the location of surgical tools relative to a preoperative image. Traditional image guided surgery relies on infrared imaging and passive sensors to determine the instruments location relative to a pre-operative image, and has been primarily used in the head and neck anatomy. Advances in ultrasonic tracking devices, designed for tracking catheters within vessels, may provide an opportunity for image guided endovascular procedures. This study evaluates the positional accuracy of an ultrasonic navigational system for tracking an endovascular catheter when stents and graft material have been deployed in an in vitro system.

METHODS:
Stents and graft material commonly used in endovascular procedures were used for this study in combination with a custom triple head ultrasonic transducer navigational system. The stents evaluated were composed of Dacron/nitinol, polytetrafluoroethylene (PTFE)/nitinol, and bare nitinol. They were deployed into cannualized excised porcine tissue, and a catheter with a custom microtransducer was inserted. Measurements of catheter position and signal quality were then recorded.

RESULTS:
The positional accuracy was not affected by any of the stent materials. Figure 1 shows an example of the measured vs. actual position of a catheter while traversing the transition region of a PTFE/nitinol stent. The maximum error was 1.7mm with a standard deviation of 0.7mm.


CONCLUSIONS:
The use of ultrasonic based navigational systems is feasible in endovascular procedures, even in the presence of common stent materials, and has significant promise as a tool for endovascular procedures.