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Keywords:

  • MRI safety;
  • heating;
  • electromagnetic modeling;
  • medical implants

Abstract

Purpose:

To use numerical modeling to predict the worst-case of magnetic resonance imaging (MRI)-induced heating of an orthopedic implant of different sizes under 1.5-T/64-MHz and 3-T/128-MHz conditions and to apply the experimental test to validate the numerical results for worst-case heating.

Materials and Methods:

Investigations of specific absorption rate (SAR) and the temperature rise of an orthopedic implant of different sizes within a standard phantom were accomplished by numerical finite-difference time-domain modeling and experimental measurements. MRI-related heating experiments were performed using standardized techniques at 1.5-T/64-MHz and 3-T/128-MHz.

Results:

The numerical modeling results indicated that the induced energy deposition is almost linearly related to the dimension of the orthopedic implant when it is less than 100 mm for 1.5-T/64-MHz and 3-T/128-MHz conditions. At 3-T/128-MHz, when the dimension is greater than 100 mm, the linear relation does not exist, which suggests a wavelength effect at higher frequency. Higher temperature rises occurred at 1.5-T/64-MHz MRI than at 3-T/128-MHz for both numerical modeling and experimental studies.

Conclusion:

The numerical technique predicted which device size had maximum heating and its location. Temperature rise data agreed well with thermal simulation results. The presented method proved to be suitable to assess MRI-induced heating of complex medical implants. J. Magn. Reson. Imaging 2013;37:491–497. © 2012 Wiley Periodicals, Inc.