Last updated: 4/11/2017

Bioelectric navigation (BN) is a new technique for guiding intravascular devices without ionizing radiation. A set of electrodes on the tip of the device creates a small, weak electric field inside the blood vessel. Changes in the geometry of the vessel as the device moves cause measurable changes to the signal at the electrodes. That geometry-dependent signal can be mapped to a previously acquired 3D model of the vessel tree, enabling localization of the device.

• Student: Erin Sutton
• Mentors: Bernhard Fuerst, Nassir Navab, Noah Cowan

The state of the art for intravascular navigation is to first navigate a guidewire under fluoroscopy to the area of interest then advance a catheter over the guidewire. The current BN prototype uses a commercially available, non-irrigated 6F catheter, too large to be used as a guidewire. The goal of this project is to create a guidewire based on the BN technology.

If successful, the guidewire could have a significant impact on minimally invasive endovascular procedures. In the US, there are approximately 8 million endovascular procedures performed every year under fluoroscopic guidance [Schauer and Linton 2009]. Each procedure exposes the patient to the equivalent of 250-3500 chest x-rays [CDRH 2010], so pediatric and pregnant patients are usually unable to benefit from minimally invasive vascular surgery. While BN seems like a promising technology to reduce the dependence on x-ray guidance, its clinical utility is limited by the fact that our prototype is a catheter rather than a guidewire. Our clinical collaborator has specifically asked for a guide wire so that we can test the navigation capabilities of BN in vivo, and the success of this project is integral to the eventual adoption of the technology.

Bold typeface indicates incomplete deliverable.

• Minimum:
  1. Project Plan report and presentation
  2. Simulation of 3-electrode guidewire in single stenosis in COMSOL
  3. Repaired current sources
  4. Seminar presentation (article critique)
  5. Single CAD design of guidewire, including Bill of Materials
  6. Checkpoint presentation
  7. Working guidewire prototype
  8. Experiment design report prior to conducting experiments
  9. Results from experiment in acrylic phantom
  10. Final report

• Expected:
  1. Simulation of 3-electrode guidewire in the acrylic phantom’s main path
  2. Replacement current sources
  3. Several CAD designs of guidewire, with core 0.014” commercially available guidewire
  4. Final presentation to the LIMBS Laboratory

• Maximum:
  1. Simulation of guidewire with several electrode configurations
  2. New design for the constant current source in Eagle
  3. Results from experiment in gelatin phantom
  4. Experiment design for in vivo test, ready to submit to ACUC

First, I will research guidewire construction. I found an excellent article outlining how to construct custom guidewires. Next, I’ll simulate a three-electrode guidewire in COMSOL’s electric currents module. I’m interested in how the wire’s signal amplitude compares to the catheter’s. Next, I will design the guidewire. Working with the mentors, I will define the design constraints. I will fully develop at least three designs. The mentors and I will perform a decision analysis to pick the best design. I will improve the embodiment design based on their comments and create the bill of materials. Then I’ll order all of the parts and construct the prototype. Finally, I will test the guidewire in the acrylic phantom. I’ll measure the voltage as the guidewire passes through all six paths of the phantom, using video recordings as ground truth for the guidewire position. I will compare the results to the catheter’s performance in the same phantom. If time allows, I’ll conduct a similar study in a gelatin phantom with x-ray fluoroscopy for ground truth position measurement.

• Not sure how to solder stainless steel to platinum – ask Iulian and Noah
• May have trouble sourcing sufficiently small diameter heat shrink tubing – either don’t coat wire for this experiment or look into specialty polymer manufacturers
• I’m not supposed to use the C-arm, which is necessary for the gelatin experiment – Ravi and Manu have offered to operate the C-arm for me during the experiment

Updated Schedule: https://docs.google.com/spreadsheets/d/1kXa5gIvPE9EK6KhfSXYyZehCjqEUS1cbGhZMy385lno/edit?usp=sharing

• Project Plan
  • Project plan presentation
  • Project plan proposal
• Project Background Reading
  • See Bibliography below for links.
• Project Checkpoint
  • Project checkpoint presentation
• Paper Seminar Presentations
  • Project Seminar presentation
• Project Final Presentation to LIMBS
  • LIMBS Meeting Presentation
• Project Final Poster
  • PDF of Poster
• Project Final Report
  • Final Report
• Mentor Evaluation
  • Evaluation by Noah Cowan

• B. Fuerst*, E.E. Sutton*, R. Ghotbi, N.J. Cowan, and N. Navab. Bioelectric navigation: A new paradigm for intravascular device guidance. In Sébastien Ourselin, William Wells, Mert R. Sabuncu, Gözde Unal, and Leo Joskowicz, editors, Medical Image Computing and Computer-Assisted Intervention, volume 9902 of LNCS. Springer, 2016.
• D.A. Schauer and O.W. Linton. NCRP Report No. 160, Ionizing radiation exposure of the population of the United States, medical exposure–are we doing less with more, and is there a role for health physicists? Health Phys, 97(1):1–5, 2009.
• Center for Devices and Radiological Health. Initiative to reduce unnecessary radiation exposure from medical imaging. US Food and Drug Administration, Feb 2010.
• Condino, S., Ferrari, V., Freschi, C., Alberti, A., Berchiolli, R., Mosca, F., and Ferrari, M. (2012). Electromagnetic navigation platform for endovascular surgery: how to develop sensorized catheters and guidewires. J Med Robotics Comput Assist Surg, 49(2):344-356.
• Stamper, S., Roth, E., Cowan, N., and Fortune, E. (2012). Active sensing via movement shapes spatiotemporal patterns of sensory feedback. J Exp Biol, 215(9):1567-1574.
• UK Endovascular Trainees. [UKETS]. (2013, June 26). Cardiac Catheterisation Part 1 – Left Coronary. [video]. Retrieved from https://youtu.be/zF8jk_F9Beo.

• Experiment Design Report
• Prototype Bill of Materials