The influence of stents on the performance of an ultrasonic navigation system for endovascular procedures.

OBJECTIVE

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 or radiofrequency triangulation to determine an instrument location relative to a preoperative image and has been primarily used in head and neck procedures. 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 navigation system for tracking an endovascular catheter when different stents and graft materials have been deployed in an in vitro system.

METHODS

Stent and graft materials commonly used in endovascular procedures were used for this study in combination with a custom three-head ultrasonic transducer navigation system. The stents evaluated were composed of Dacron/nitinol, polytetrafluoroethylene (PTFE)/nitinol, and bare nitinol. They were deployed into excised porcine tissue cannulized with a rotary drill, and a catheter with a custom microtransducer probe was inserted. The distance from each ultrasonic tracking module to a probe mounted on an endovascular catheter was measured using time of flight techniques, and the catheter position in three-dimensions was calculated using triangulation.

RESULTS

The measured position was compared to the actual catheter position determined by a precision translation stage. The PTFE/nitinol, bare nitinol, and Dacron/nitinol stent materials were evaluated and resulted in a maximum error of 1.7, 3.0, and 3.6 mm and an SD of 0.7, 1.2, and 1.4 mm, respectively. A reduction in signal intensity of up to 6x was observed during passage of the endovascular probe through the stent materials, but no reduction in the accuracy of the ultrasonic navigation system was evident.

CONCLUSION

The use of an ultrasonic-based navigation system is feasible in endovascular procedures, even in the presence of common stent materials. It may have promise as a navigational tool for endovascular procedures.