title: Endovascular catheter for magnetic navigation under MR imaging guidance: evaluation of safety in vivo at 1.5T.
abstract: OBJECTIVE
  Endovascular navigation under MR imaging guidance can be facilitated by a catheter with steerable microcoils on the tip. Not only do microcoils create visible artifacts allowing catheter tracking, but also they create a small magnetic moment permitting remote-controlled catheter tip deflection. A side product of catheter tip electrical currents, however, is the heat that might damage blood vessels. We sought to determine the upper boundary of electrical currents safely usable at 1.5T in a coil-tipped microcatheter system.
  
  
  METHODS
  Alumina tubes with solenoid copper coils were attached to neurovascular microcatheters with heat shrink-wrap. Catheters were tested in carotid arteries of 8 pigs. The catheters were advanced under x-ray fluoroscopy and MR imaging. Currents from 0 mA to 700 mA were applied to test heating and potential vascular damage. Postmortem histologic analysis was the primary endpoint.
  
  
  RESULTS
  Several heat-mitigation strategies demonstrated negligible vascular damage compared with control arteries. Coil currents ≤300 mA resulted in no damage (0/58 samples) compared with 9 (25%) of 36 samples for > 300-mA activations (P = .0001). Tip coil activation ≤1 minute and a proximal carotid guide catheter saline drip > 2 mL/minute also had a nonsignificantly lower likelihood of vascular damage. For catheter tip coil activations ≤300 mA for ≤1 minute in normal carotid flow, 0 of 43 samples had tissue damage.
  
  
  CONCLUSIONS
  Activations of copper coils at the tip of microcatheters at low currents in 1.5T MR scanners can be achieved without significant damage to blood vessel walls in a controlled experimental setting. Further optimization of catheter design and procedure protocols is necessary for safe remote control magnetic catheter guidance.
authors.affiliation: Departments of Radiology and Biomedical Imaging.
authors.forename: S W
authors.initials: SW
authors.lastname: Hetts
authors.forename: M
authors.initials: M
authors.lastname: Saeed
authors.forename: A J
authors.initials: AJ
authors.lastname: Martin
authors.forename: L
authors.initials: L
authors.lastname: Evans
authors.forename: A F
authors.initials: AF
authors.lastname: Bernhardt
authors.forename: V
authors.initials: V
authors.lastname: Malba
authors.forename: F
authors.initials: F
authors.lastname: Settecase
authors.forename: L
authors.initials: L
authors.lastname: Do
authors.forename: E J
authors.initials: EJ
authors.lastname: Yee
authors.forename: A
authors.initials: A
authors.lastname: Losey
authors.forename: R
authors.initials: R
authors.lastname: Sincic
authors.forename: P
authors.initials: P
authors.lastname: Lillaney
authors.forename: S
authors.initials: S
authors.lastname: Roy
authors.forename: R L
authors.initials: RL
authors.lastname: Arenson
authors.forename: M W
authors.initials: MW
authors.lastname: Wilson
mesh_terms: D000818:Animals; D002058:Burns, Electric / Q000175:diagnosis / Q000209:etiology*; D002339:Carotid Arteries / Q000473:pathology* / Q000601:surgery*; D020212:Carotid Artery Injuries / Q000209:etiology* / Q000473:pathology / Q000517:prevention & control; D002404:Catheterization / Q000009:adverse effects / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D004869:Equipment Safety; D053783:Magnetic Resonance Imaging, Interventional / Q000009:adverse effects* / Q000295:instrumentation*; D013552:Swine