title: Steerable catheter microcoils for interventional MRI reducing resistive heating.
abstract: OBJECTIVE
  The aims of this study were to assess resistive heating of microwires used for remote catheter steering in interventional magnetic resonance imaging and to investigate the use of alumina to facilitate heat transfer to saline flowing in the catheter lumen.
  
  
  METHODS
  A microcoil was fabricated using a laser lathe onto polyimide-tipped or alumina-tipped endovascular catheters. In vitro testing was performed on a 1.5-T magnetic resonance system using a vessel phantom, body radiofrequency coil, and steady-state pulse sequence. Resistive heating was measured with water flowing over a polyimide-tip catheter or saline flowing through the lumen of an alumina-tip catheter. Preliminary in vivo testing in porcine common carotid arteries was conducted with normal blood flow or after arterial ligation when current was applied to an alumina-tip catheter for up to 5 minutes.
  
  
  RESULTS
  After application of up to 1 W of direct current power, clinically significant temperature increases were noted with the polyimide-tip catheter: 23°C/W at zero flow, 13°C/W at 0.28 cm(3)/s, and 7.9°C/W at 1 cm(3)/s. Using the alumina-tip catheter, the effluent temperature rise using the lowest flow rate (0.12 cm(3)/s) was 2.3°C/W. In vivo testing demonstrated no thermal injury to vessel walls at normal and zero arterial flow.
  
  
  CONCLUSIONS
  Resistive heating in current carrying wire pairs can be dissipated by saline coolant flowing within the lumen of a catheter tip composed of material that facilitates heat transfer.
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, CA, USA.
authors.forename: Anthony
authors.initials: A
authors.lastname: Bernhardt
authors.forename: Mark W
authors.initials: MW
authors.lastname: Wilson
authors.forename: Fabio
authors.initials: F
authors.lastname: Settecase
authors.forename: Leland
authors.initials: L
authors.lastname: Evans
authors.forename: Vincent
authors.initials: V
authors.lastname: Malba
authors.forename: Alastair J
authors.initials: AJ
authors.lastname: Martin
authors.forename: Maythem
authors.initials: M
authors.lastname: Saeed
authors.forename: Timothy P L
authors.initials: TP
authors.lastname: Roberts
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Arenson
authors.forename: Steven W
authors.initials: SW
authors.lastname: Hetts
mesh_terms: D002058:Burns, Electric / Q000209:etiology / Q000517:prevention & control; D002406:Catheterization, Peripheral / Q000009:adverse effects / Q000295:instrumentation*; D057785:Catheters; D017097:Electric Impedance; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006358:Hot Temperature; D006801:Humans; D053783:Magnetic Resonance Imaging, Interventional / Q000009:adverse effects / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation*; D025321:Surgery, Computer-Assisted / Q000009:adverse effects / Q000295:instrumentation*