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Research Papers

# Steerable Guidewire for Magnetic Resonance Guided Endovascular Interventions

[+] Author and Article Information
H. C. M. Clogenson

Department of Biomechanical Engineering,
Delft University of Technology,
Mekelweg 2,
Delft 2628 CD, The Netherlands
e-mail: H.C.Clogenson@tudelft.nl

J. Dankelman, J. J. van den Dobbelsteen

Department of Biomechanical Engineering,
Delft University of Technology,
Mekelweg 2,
Delft 2628 CD, The Netherlands

Manuscript received June 12, 2013; final manuscript received January 17, 2014; published online March 7, 2014. Assoc. Editor: Carl A. Nelson.

J. Med. Devices 8(2), 021002 (Mar 07, 2014) (7 pages) Paper No: MED-13-1156; doi: 10.1115/1.4026560 History: Received June 12, 2013; Revised January 17, 2014

## Abstract

In endovascular interventions, thin, flexible instruments are inserted through the skin into the blood vessels to diagnose and treat various diseases of the vascular system. One drawback is that the instruments are difficult to maneuver in the desired direction due to limitations in shape and flexibility. Another disadvantage is that the interventions are performed under intermittent fluoroscopy/angiography imaging. Magnetic resonance imaging (MRI) may offer advantages over X-ray guidance. It presents a good soft tissue contrast without the use of nephrotoxic media or ionizing radiation. The aim of this study is to develop a guidewire that is compatible with MRI and includes a steerable segment at the tip. This added degree-of-freedom may improve the maneuverability of the devices thereby the efficiently and safety of the navigation. A 1.6 m (5 ft, 3 in.) long and 0.035 in. diameter guidewire that consists of MR compatible materials and has a flexible tip was designed. The only metallic part was a nitinol rod that was implemented at the distal flexible tip. To limit the risk of heating in the MRI, this rod was kept shorter than 30 mm. The tip could be deflected in one direction by pulling on a Dyneema wire that was placed in the lumen of the shaft of the guidewire. To drive the steerable tip, a handle that could be easily attached/detached from the instrument was designed and implemented. Using the handle, the tip of the 1.60 m long guidewire prototype could be actuated to reach angles from 30 deg to 250 deg. The handle could easily be placed on and removed from the guidewire, so conventional 0.035 in.–compatible catheters could slide over from the proximal end. However, in order to make the guidewire more efficient to enter a bifurcation, the stiffness of the tip should progressively increase from its proximal to its distal end. The guidewire was imaged in a 1.5T MRI using real-time imaging without producing artifacts that would have shaded the anatomy. It was possible to assemble a guidewire with a steerable segment in the required size, using MR compatible materials. Therefore, the current design is a promising proof of concept and allowed us to clearly identify the features that need to be improved in order to come to a clinically applicable instrument.

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## Figures

Fig. 1

Design of the steerable guidewire

Fig. 2

Handle and tip of the steerable guidewire (top) and exploded view of the handle (bottom)

Fig. 3

Front view of the clamp of the guidewire shaft in the opened and closed position. The shaft of the guidewire is placed and held inside the lumen of the clamp.

Fig. 4

Side and front view of the clamp of the wire: when placed, the clamp restrains the PEEK cylinder that is connected to the pulling wire

Fig. 9

MRI scan (fGRE RT, slice thickness 12 mm (0.047 in.), 1 fps) of the steerable guidewire in a vascular model (transcatheter valve simulator heart model, Elastrat, Geneva Switzerland) with pulsatile flow. The two passive markers (white arrows) indicated the localization of the steerable tip that was lying in the thoracic artery, above the celiac trunk.

Fig. 8

Assembly of the guidewire on the handle: place the slider in front position and open the front clamp (top), align the PEEK cylinder with the shaft and place the distal part of the guidewire inside the lumen of the handle (middle), and place the Dyneema wire and the PEEK cylinder into the clamp, fasten the shaft (bottom)

Fig. 7

Inhomogeneous bending of the tip for a 180 deg angle. A sharp bend was observed at its base (red circle), and the proximal and distal part of the tip presented two radii of curvatures (white arcs of circle drawn over the tip).

Fig. 6

Shape of the steerable guidewire tip compared to the calculated results for a 28 mm (1.1 in.) long tip. (a) Measured and calculated vessel diameter Dν. (b) Difference between the calculated and measured results ΔDν.

Fig. 5

Measurements setup: the base of the deflectable segment was taped to the board and the tip was actuated; each position of the tip was measured (overlay of three pictures with three distinct positions of the steerable tip)

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