title: Whole shaft visibility and mechanical performance for active MR catheters using copper-nitinol braided polymer tubes.
abstract: BACKGROUND
  Catheter visualization and tracking remains a challenge in interventional MR.Active guidewires can be made conspicuous in "profile" along their whole shaft exploiting metallic core wire and hypotube components that are intrinsic to their mechanical performance. Polymer-based catheters, on the other hand, offer no conductive medium to carry radio frequency waves. We developed a new "active" catheter design for interventional MR with mechanical performance resembling braided X-ray devices. Our 75 cm long hybrid catheter shaft incorporates a wire lattice in a polymer matrix, and contains three distal loop coils in a flexible and torquable 7Fr device. We explored the impact of braid material designs on radiofrequency and mechanical performance.
  
  
  RESULTS
  The incorporation of copper wire into in a superelastic nitinol braided loopless antenna allowed good visualization of the whole shaft (70 cm) in vitro and in vivo in swine during real-time MR with 1.5 T scanner. Additional distal tip coils enhanced tip visibility. Increasing the copper:nitinol ratio in braiding configurations improved flexibility at the expense of torquability. We found a 16-wire braid of 1:1 copper:nitinol to have the optimum balance of mechanical (trackability, flexibility, torquability) and antenna (signal attenuation) properties. With this configuration, the temperature increase remained less than 2 degrees C during real-time MR within 10 cm horizontal from the isocenter. The design was conspicuous in vitro and in vivo.
  
  
  CONCLUSIONS
  We have engineered a new loopless antenna configuration that imparts interventional MR catheters with satisfactory mechanical and imaging characteristics. This compact loopless antenna design can be generalized to visualize the whole shaft of any general-purpose polymer catheter to perform safe interventional procedures.
authors.affiliation: Translational Medicine Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA. kocaturko@nhlbi.nih.gov
authors.forename: Ozgur
authors.initials: O
authors.lastname: Kocaturk
authors.forename: Christina E
authors.initials: CE
authors.lastname: Saikus
authors.forename: Michael A
authors.initials: MA
authors.lastname: Guttman
authors.forename: Anthony Z
authors.initials: AZ
authors.lastname: Faranesh
authors.forename: Kanishka
authors.initials: K
authors.lastname: Ratnayaka
authors.forename: Cengizhan
authors.initials: C
authors.lastname: Ozturk
authors.forename: Elliot R
authors.initials: ER
authors.lastname: McVeigh
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Lederman
mesh_terms: D000497:Alloys; D000818:Animals; D001011:Aorta / Q000033:anatomy & histology; D002406:Catheterization, Peripheral / Q000295:instrumentation*; D003300:Copper; D004867:Equipment Design; D005263:Femoral Artery / Q000033:anatomy & histology; D053783:Magnetic Resonance Imaging, Interventional / Q000295:instrumentation*; D008422:Materials Testing; D023421:Models, Animal; D019047:Phantoms, Imaging; D018583:Pliability; D011108:Polymers; D013348:Subclavian Artery / Q000033:anatomy & histology; D013552:Swine; D013696:Temperature; D019415:Torque
chemical_list: D000497:Alloys; D011108:Polymers; C013616:nitinol; D003300:Copper
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