The dependence of radiofrequency induced pacemaker lead tip heating on the electrical conductivity of the medium at the lead tip

Authors

  • Deborah A. Langman,

    Corresponding author
    1. Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, California, USA
    2. Biomedical Physics Interdepartmental Program, University of California, Los Angeles, California, USA
    • 10945 Le Conte Avenue, Ueberroth Building Suite 1417, Los Angeles, California 90095
    Search for more papers by this author
  • Ira B. Goldberg,

    1. Department of Electrical Engineering, University of California, Los Angeles, California, USA
    Search for more papers by this author
  • Jack Judy,

    1. Department of Electrical Engineering, University of California, Los Angeles, California, USA
    Search for more papers by this author
  • J. Paul Finn,

    1. Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, California, USA
    2. Biomedical Physics Interdepartmental Program, University of California, Los Angeles, California, USA
    Search for more papers by this author
  • Daniel B. Ennis

    1. Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, California, USA
    2. Biomedical Physics Interdepartmental Program, University of California, Los Angeles, California, USA
    Search for more papers by this author

Abstract

Radiofrequency induced pacemaker lead tip heating is one of the main reasons magnetic resonance imaging (MRI) is contraindicated for patients with pacemakers. The objective of this work was to evaluate the dependence of pacemaker lead tip heating during MRI scanning on the electrical conductivity of the medium surrounding the pacemaker lead tip. The effect of conductivity was measured using hydroxyethyl cellulose, polyacrylic acid, and saline with conductivities ranging from 0 to 3 S/m which spans the range of human tissue conductivity. The maximum lead tip heating observed in polyacrylic acid was 50.4°C at 0.28 S/m, in hydroxyethyl cellulose the maximum was 36.8°C at 0.52 S/m, and in saline the maximum was 12.5°C at 0.51 S/m. The maximum power transfer theorem was used to calculate the relative power deposited in the solution based on the characteristic impedance of the pacemaker lead and test solution impedance. The results demonstrate a strong correlation between the relative power deposited and pacemaker lead tip heating for hydroxyethyl cellulose and saline solutions. Maximum power deposition occurred when the impedance of the solution matched the pacemaker lead impedance. Pacemaker lead tip heating is dependent upon the electrical conductivity of the solution at the lead tip and should be considered when planning in vitro gel or saline experiments. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.

Ancillary