Basic research study
Stereotactic endovascular aortic navigation with a novel ultrasonic-based three-dimensional localization system

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Background

Endovascular aortic procedures have been developed to treat many aortic diseases effectively. However, these procedures are also becoming increasingly complex given the development of branched or fenestrated endografts. Part of the difficulty lies in the limitations of current imaging paradigms. A more intuitive, three-dimensional (3D) mode of intraoperative imaging is desirable to accommodate the future progression of endovascular techniques. This article describes a novel endovascular catheter tracking device that uses ultrasonic signals, not ultrasound imaging. The tracking device displays real-time in vivo location on previously acquired 3D computed tomography (CT) images in an intuitive, endoluminal view. This system was tested in two swine and validated against fluoroscopy and by delivering stent grafts.

Methods

The ultrasonic-based localization system (ULS) provides real-time location information of a modified endovascular catheter and displays this location on preoperative 3D CT images. The 9F endovascular catheter has a small ultrasonic transmitter attached to its tip to signal its location to the ULS. Subsequent endovascular deployment of an aortic stent was carried out using only the ULS to target the stent placement position in the aorta of Yorkshire swine. System accuracy was measured against concurrent angiography as well as to deployed stents in situ.

Results

We successfully displayed the endovascular catheter tip location in real time along the registered CT aortic images, providing virtual endoluminal tracking. The relative accuracy of the ULS as compared with angiography for catheter movements in the abdominal aorta was found to have a mean error less than 1 mm. The ULS coordinates tracked within the lumen of the aortic image 98% of the time, as defined by the proportion of points within one radius distance of the aortic image centerline. Finally, three aortic stents were deployed using the ULS virtual image display to locate the target position in the aorta for stent deployment. Errors between target position and actual stent position ranged from −5.0 to +7.9 mm.

Conclusions

This study demonstrates the feasibility of virtual image-guided endovascular aortic navigation using a ULS. This provides a 3D platform for virtual navigation on preoperative CT scan images during endovascular procedures that could assist in stent deployment as well as minimize or eliminate the need for procedural ionizing radiation and iodinated contrast. Future work will focus on miniaturization and refinements in accuracy that will be required to translate this technology into clinical application in endovascular procedures.

Clinical Relevance

Ionizing radiation exposure is a concern for patients with aortic pathology who require serial computed tomography scans and angiography for treatment. This patient population has a high incidence of renal dysfunction, which may be aggravated by iodinated contrast. Ionizing radiation and contrast exposure will only increase with the increasing complexity of aortic endovascular procedures. Furthermore, endovascular aortic procedures are limited by the two-dimensional imaging capabilities of fluoroscopy and angiography. A real-time three-dimensional catheter localization system can help integrate high-fidelity preoperative computed tomography images with the intraoperative workflow. Combined with three-dimensional surface rendering of the vasculature, the system can display the catheter's location and movement on an intuitive, virtual endoluminal view. This system relies on ultrasonic signaling, thereby eliminating the issues with metal interference that occur with electromagnetic-based localization systems currently in use for skull-based and spine surgery.

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In-kind support was provided by Smithers Medical Products. Equipment support was provided in part by NIH R01CA116379-01A1. J.C.M. was supported by the Alfred Mann Institute Innovation Fellowship and the NSF GK-12 Fellowship.

Author conflict of interest: none.

Additional material for this article may be found online at www.jvascsurg.org.

The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest.