Radiofrequency heating studies on anesthetized swine using fractionated dipole antennas at 10.5 T

Magn Reson Med. 2018 Jan;79(1):479-488. doi: 10.1002/mrm.26688. Epub 2017 Mar 31.

Abstract

Purpose: To validate electromagnetic and thermal simulations with in vivo temperature measurements, and to demonstrate a framework that can be used to predict temperature increase caused by radiofrequency (RF) excitation with dipole transmitter arrays.

Methods: Dipole arrays were used to deliver RF energy in the back/neck region of the swine using different RF excitation patterns (n = 2-4 per swine) for heating. The temperature in anesthetized swine (n = 3) was measured using fluoroscopic probes (n = 12) and compared against thermal modeling from animal-specific electromagnetic simulations.

Results: Simulated temperature curves were in agreement with the measured data. The root mean square error between simulated and measured temperature rise at all locations (at the end of each RF excitation) is calculated as 0.37°C. The mean experimental temperature rise at the maximum temperature rise locations (averaged over all experiments) is calculated as 2.89°C. The root mean square error between simulated and measured temperature at the maximum temperature rise location is calculated as 0.57°C. (Error values are averaged over all experiments.) CONCLUSIONS: Electromagnetic and thermal simulations were validated with experiments. Thermal effects of RF excitation at 10.5 Tesla with dipoles were investigated. Magn Reson Med 79:479-488, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Keywords: 10.5 T; SAR; dipole arrays; radiofrequency (RF); temperature.

MeSH terms

  • Animals
  • Calibration
  • Computer Simulation
  • Electromagnetic Fields
  • Electromagnetic Radiation
  • Equipment Design*
  • Hot Temperature*
  • Hyperthermia, Induced / instrumentation*
  • Magnetic Resonance Imaging
  • Magnetic Resonance Spectroscopy
  • Models, Anatomic
  • Phantoms, Imaging
  • Radio Waves*
  • Swine
  • Tomography, X-Ray Computed