title: Electromagnetic navigation for thoracic aortic stent-graft deployment: a pilot study in swine.
abstract: OBJECTIVE
  To determine the feasibility of electromagnetic tracking as a method to augment conventional imaging guidance for the safe delivery, precise positioning, and accurate deployment of thoracic aortic endografts.
  
  
  METHODS
  Custom guide wires were fabricated, and the delivery catheters for thoracic aortic endoprostheses were retrofitted with integrated electromagnetic coil sensors to enable real-time endovascular tracking. Preprocedure thoracic computed tomographic (CT) angiograms were obtained after the placement of fiducial skin patches on the chest wall of three anesthetized swine, enabling automatic registration. The stent-graft deployment location target near the subclavian artery was selected on the preprocedure CT angiogram. Two steps were analyzed: advancing a tracked glidewire to the aortic arch and positioning the tracked stent-graft assembly by using electromagnetic guidance alone. Multiple CT scans were obtained to evaluate the accuracy of the electromagnetic tracking system by measuring the target registration error, which compared the actual position of the tracked devices to the displayed "virtual" electromagnetic-tracked position. Postdeployment CT angiography and necropsy helped confirm stent-graft position and subclavian artery patency.
  
  
  RESULTS
  A stent-graft was successfully delivered and deployed in each of the three animals by using real-time electromagnetic tracking alone. The mean fiducial registration error with autoregistration was 1.5 mm. Sixteen comparative scans were obtained to determine the target registration error, which was 4.3 mm +/- 0.97 (range, 3.0-6.0 mm) for the glidewire sensor coil. The mean target registration error for the stent-graft delivery catheter sensor coil was 2.6 mm +/- 0.7 (range, 1.9-3.8 mm). The mean deployment error for the stent-graft, defined as deployment deviation from the target, was 2.6 mm +/- 3.0.
  
  
  CONCLUSIONS
  Delivery and deployment of customized thoracic stent-grafts with use of electromagnetic tracking alone is feasible and accurate in swine. Combining endovascular electromagnetic tracking with conventional fluoroscopy may further improve accuracy and be a more realistic multimodality approach.
authors.affiliation: Department of Radiology and Imaging Sciences, National Institutes of Health, Rm 1C365 MSC 1182 10 Center Dr, 9000 Rockville Pike, Bethesda, MD 20890, USA. naj@mail.nih.gov
authors.forename: Nadine
authors.initials: N
authors.lastname: Abi-Jaoudeh
authors.forename: Neil
authors.initials: N
authors.lastname: Glossop
authors.forename: Michael
authors.initials: M
authors.lastname: Dake
authors.forename: William F
authors.initials: WF
authors.lastname: Pritchard
authors.forename: Alberto
authors.initials: A
authors.lastname: Chiesa
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Dreher
authors.forename: Thomas
authors.initials: T
authors.lastname: Tang
authors.forename: John W
authors.initials: JW
authors.lastname: Karanian
authors.forename: Bradford J
authors.initials: BJ
authors.lastname: Wood
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000601:surgery*; D001807:Blood Vessel Prosthesis; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008280:Magnetics / Q000295:instrumentation*; D010865:Pilot Projects; D019919:Prosthesis Implantation / Q000295:instrumentation*; D015607:Stents; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*; D013552:Swine
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