title: Use of internal coils for independent and direct MR imaging-guided endovascular device tracking.
abstract: OBJECTIVE
  To test the hypotheses that a single internal guide wire coil (i) permits independent and direct depiction of guide wires and catheters and (ii) improves catheter-tracking accuracy and depiction compared to external receiver coils.
  
  
  METHODS
  Standard 5-6-F angiographic catheters were filled with dilute 4% gadolinium chelate. A single 0.030-inch-diameter internal guide wire coil was placed inside the catheter. True fast imaging with steady-state precession was used to directly visualize the guide wire. Inversion recovery-prepared fast low-angle shot technique was used to track catheters over a thick slice. In phantom experiments, we compared catheter signal-to-noise ratios (SNRs) with the internal coil and a phased-array surface coil with use of the Wilcoxon signed-rank test. Tip-tracking accuracy was assessed with use of linear regression. In pigs (n = 7), catheters and guide wires were independently tracked in real time.
  
  
  RESULTS
  In phantoms, catheter SNR with the internal coil (12.0) was significantly greater than that with the surface coil (4.0; P =.001). Tip-tracking accuracy was also improved with use of the internal coil (R(2) = 0.94 vs 0.50). In swine vasculature, catheters and guide wires could be directly and independently tracked at 1.7-2.0 frames per second. Catheters were clearly visualized with use of the internal coil, with a typical catheter background contrast-to-noise ratio of 6.6. Catheters were not visible with use of the external coil because of the small catheter size compared to the slice thickness.
  
  
  CONCLUSIONS
  Internal guide wire coils permit independent and direct depiction of guide wires and catheters in vivo for MR imaging-guided endovascular interventions. They also improve catheter tracking accuracy and depiction compared to external coils.
authors.affiliation: Department of Radiology, Northwestern University Medical School, 676 North St. Clair, Suite 800, Chicago, Illinois 60611, USA. romary@radiology.northwestern.edu
authors.forename: Reed A
authors.initials: RA
authors.lastname: Omary
authors.forename: Jordin D
authors.initials: JD
authors.lastname: Green
authors.forename: Wayne S
authors.initials: WS
authors.lastname: Fang
authors.forename: Ingmar
authors.initials: I
authors.lastname: Viohl
authors.forename: J Paul
authors.initials: JP
authors.lastname: Finn
authors.forename: Debiao
authors.initials: D
authors.lastname: Li
mesh_terms: D000818:Animals; D002404:Catheterization; D003287:Contrast Media; D005682:Gadolinium; D008279:Magnetic Resonance Imaging; D019047:Phantoms, Imaging; D013552:Swine
chemical_list: D003287:Contrast Media; D005682:Gadolinium