Skip to main content

B1 field-insensitive transformers for RF-safe transmission lines

Magnetic Resonance Materials in Physics, Biology and Medicine volume 19, pages 257–266 (2006)Cite this article

Abstract

Objective: Integration of transformers into transmission lines suppresses radiofrequency (RF)-induced heating. New figure-of-eight-shaped transformer coils are compared to conventional loop transformer coils to assess their signal transmission properties and safety profile.

Materials and methods: The transmission properties of figure-of-eight-shaped transformers were measured and compared to transformers with loop coils. Experiments to quantify the effect of decoupling from the B1 field of the MR system were conducted. Temperature measurements were performed to demonstrate the effective reduction of RF-induced heating. The transformers were investigated during active tracking experiments.

Results: Coupling to the B1 field was reduced by 18 dB over conventional loop-shaped transformer coils. MR images showed a significantly reduced artifact for the figure-of-eight- shaped coils generated by local flip-angle amplification. Comparable transmission properties were seen for both transformer types. Temperature measurements showed a maximal temperature increase of 30K/3.5 K for an unsegmented/ segmented cable. With a segmented transmission line a robotic assistance system could be successfully localized using active tracking.

Conclusion: The figure-of-eight-shaped transformer design reduces both RF field coupling with the MR system and artifact sizes. Anatomical structure close to the figure-of-eight-shaped transformer may be less obscured as with loop-shaped transformers if these transformers are integrated into e.g. intravascular catheters.

This is a preview of subscription content, access via your institution.

Access options

Buy single article

Instant access to the full article PDF.

43,34 €

Price includes VAT (Finland)
Tax calculation will be finalised during checkout.

References

  1. Duerk JL, Wong EY, Lewin JS, (2002) A brief review of hardware for catheter tracking in magnetic resonance imaging. Magn Reson Mater Phys 13:199–208

    Google Scholar 

  2. Rubin DL, Ratner AV, Young SW, (1990) Magnetic susceptibility effects and their application in the development of new ferromagnetic catheters for magnetic resonance imaging. Invest Radiol 25:1325–1332

    PubMed  CAS  Article  Google Scholar 

  3. Koechli VD, McKinnon GC, Hofmann E, von Schulthess GK, (1994) Vascular interventions guided by ultrafast MR imaging evaluation of different materials. Magn Reson Med 31:309–314

    Google Scholar 

  4. Bakker CJ, Hoogeven RM, Hurtak WF, van Vaals JJ, Viergever MA, Mali WP, (1997) MR-guided endovascular interventions: susceptibility-based catheter and near-real-time imaging technique. Radiology 202:273–276

    PubMed  CAS  Google Scholar 

  5. Unal O, Korosec FR, Frayne R, Strother CM, Mistretta CA, (1998) A rapid 2D time-resolved variable-rate k-space sampling MR technique for passive catheter tracking during endovascular procedures. Magn Reson Med 40:356–362

    PubMed  CAS  Google Scholar 

  6. Omary RA, Unal O, Koscielski DS, Frayne R, Korosec FR, Mistretta CA, Strother CM, Grist TM, (2000) Real-time MR imaging-guided passive catheter tracking with use of gadolinium-filled catheters. J Vasc Interv Radiol 11:1079–1085

    PubMed  CAS  Google Scholar 

  7. Ackerman JL, Offutt MC, Buxton RB, Brady TJ (1986) Rapid 3D tracking of small RF coils. In: Proceedings of the 5th annual meeting of the society for magnetic resonance in medicine. Montreal, Canada, p. 1131

  8. Dumoulin CL, Souza SP, Darrow RD, (1993) Real-time position monitoring of invasive devices using magnetic resonance. Magn Reson Med 29:411–415

    PubMed  CAS  Google Scholar 

  9. Zhang Q, Wendt M, Aschoff AJ, Zheng L, Lewin JS, Duerk J, (2001) A multielement RF coil for MRI guidance of interventional devices. J Magn Reson Imaging 14:56–62

    PubMed  CAS  Article  Google Scholar 

  10. Zuehlsdorff S, Umathum R, Volz S, et al. (2004) MR coil design for simultaneous tip tracking and curvature delineation of a catheter. Magn Reson Med 52:214–218

    Google Scholar 

  11. Maier SE, Wildermuth S, Darrow RD, Watkins RD, Debatin JF, Dumoulin CL (1995) Safety of MR tracking catheters. In: Proceedings of the 12th annual joint meeting of SMR/ESMRMB, Nice, France p. 497

  12. Ladd ME, Quick HH, Debatin JF, von Schulthess GK, McKinnon GC (1998) Resonant heating of intravascular RF coils. In: Proceedings of the 6th annual meeting of ISMRM, Sydney, Australia p. 473

  13. Konings MK, Bartels LW, Smits HFM, Bakker CJG, (2000) Heating around intravascular guidewires by resonating RF waves. J Magn Reson Imaging 12:79–85

    PubMed  CAS  Article  Google Scholar 

  14. Nitz WR, Oppelt A, Renz W, Manke C, Lenhart M, Link J, (2001) On the heating of linear conductive structures as guide wires and catheters in interventional MRI. J Magn Reson Imaging 13:105–114

    PubMed  CAS  Article  Google Scholar 

  15. Atalar E, (1998) Safe coaxial cables for MRI. Radiology 209(Suppl):431–432

    Google Scholar 

  16. Ladd ME, Quick HH, (2000) Reduction of resonant RF heating in intravascular catheters using coaxial chokes. Magn Reson Med 43:615–619

    PubMed  CAS  Article  Google Scholar 

  17. Weiss S, Vernickel P, Schaeffter T, Schulz V, Gleich B, (2005) Transmission line for improved RF safety of interventional devices. Magn Reson Med 54:182–189

    PubMed  Article  Google Scholar 

  18. Vernickel P, Schulz V, Weiss S, Gleich B, (2005) A safe transmission line for MRI. IEEE Trans BME 52:1094–1102

    Google Scholar 

  19. Bock M, Melzer A, Bardenheuer H, Ghaderi H, Gutmann B, Zimmermann H, Semmler W (2005) MR-guided percutaneous interventions using a robotic assistance system: initial experiences in a pig model. In: Proceedings of the 13th annual meeting of ISMRM, Miami Beach, USA p. 511

  20. ASTM F2182–02. Standard test method for measurement of radio frequency induced heating near passive implants during magnetic resonance imaging. ASTM International.

  21. Mueller S, Semmler W, Bock M (2006) Dual echo tip tracking with orthogonal dephaser gradients. In: Proceedings of the 14th annual meeting of ISMRM, Seattle, USA p. 637

  22. Wong EY, Zhang Q, Duerk JL, Lewin JS, Wendt M, (2000) An optical system for wireless detuning of parallel resonant circuits. J Magn Reson Imaging 12:632–638

    PubMed  CAS  Article  Google Scholar 

  23. Weiss S, Kuehne T, Brinkert F, Krombach G, Katoh M, Schaeffter T, Guenther RW, Buecker A, (2004) In~vivo safe catheter visualization and slice tracking using an optically detonable resonant marker. Magn Reson Med 52:860–868

    PubMed  Article  Google Scholar 

  24. Bock M, Umathum R, Sikora J, Brenner S, Aguor EN, Semmler W, (2006) A Faraday effect position sensor for interventional magnetic resonance imaging. Phys Med Biol 51:999–1009

    PubMed  CAS  Article  Google Scholar 

Download references

Author information

Affiliations

  1. Deutsches Krebsforschungszentrum (dkfz), Abt. Medizinische Physik in der Radiologie (E020), Im Neuenheimer Feld 280, 69120, Heidelberg, Germany

    Axel Krafft, Sven Müller, Reiner Umathum, Wolfhard Semmler & Michael Bock

Authors
  1. Axel Krafft
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Sven Müller
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Reiner Umathum
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Wolfhard Semmler
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Michael Bock
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Michael Bock.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Krafft, A., Müller, S., Umathum, R. et al. B1 field-insensitive transformers for RF-safe transmission lines. Magn Reson Mater Phy 19, 257–266 (2006). https://doi.org/10.1007/s10334-006-0055-x

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s10334-006-0055-x

Keywords

  • RF safety
  • RF heating
  • Active device tracking
  • B1 field coupling
  • Interventional MRI