title: Voltage-based device tracking in a 1.5 Tesla MRI during imaging: initial validation in swine models.
abstract: OBJECTIVE
  Voltage-based device-tracking (VDT) systems are commonly used for tracking invasive devices in electrophysiological cardiac-arrhythmia therapy. During electrophysiological procedures, electro-anatomic mapping workstations provide guidance by integrating VDT location and intracardiac electrocardiogram information with X-ray, computerized tomography, ultrasound, and MR images. MR assists navigation, mapping, and radiofrequency ablation. Multimodality interventions require multiple patient transfers between an MRI and the X-ray/ultrasound electrophysiological suite, increasing the likelihood of patient-motion and image misregistration. An MRI-compatible VDT system may increase efficiency, as there is currently no single method to track devices both inside and outside the MRI scanner.
  
  
  METHODS
  An MRI-compatible VDT system was constructed by modifying a commercial system. Hardware was added to reduce MRI gradient-ramp and radiofrequency unblanking pulse interference. VDT patches and cables were modified to reduce heating. Five swine cardiac VDT electro-anatomic mapping interventions were performed, navigating inside and thereafter outside the MRI.
  
  
  RESULTS
  Three-catheter VDT interventions were performed at >12 frames per second both inside and outside the MRI scanner with <3 mm error. Catheters were followed on VDT- and MRI-derived maps. Simultaneous VDT and imaging was possible in repetition time >32 ms sequences with <0.5 mm errors, and <5% MRI signal-to-noise ratio (SNR) loss. At shorter repetition times, only intracardiac electrocardiogram was reliable. Radiofrequency heating was <1.5°C.
  
  
  CONCLUSIONS
  An MRI-compatible VDT system is feasible.
authors.affiliation: Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts, USA.
authors.forename: Ehud J
authors.initials: EJ
authors.lastname: Schmidt
authors.forename: Zion T H
authors.initials: ZT
authors.lastname: Tse
authors.forename: Tobias R
authors.initials: TR
authors.lastname: Reichlin
authors.forename: Gregory F
authors.initials: GF
authors.lastname: Michaud
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Watkins
authors.forename: Kim
authors.initials: K
authors.lastname: Butts-Pauly
authors.forename: Raymond Y
authors.initials: RY
authors.lastname: Kwong
authors.forename: William
authors.initials: W
authors.lastname: Stevenson
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Schweitzer
authors.forename: Israel
authors.initials: I
authors.lastname: Byrd
authors.forename: Charles L
authors.initials: CL
authors.lastname: Dumoulin
mesh_terms: D000818:Animals; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation*; D010865:Pilot Projects; D010992:Plethysmography, Impedance / Q000295:instrumentation*; D019736:Prostheses and Implants; D013552:Swine; D059015:Wireless Technology / Q000295:instrumentation*