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

• Published in: Magnetic resonance in medicine Vol. 79; no. 1; pp. 479 - 488
• Main Authors: Eryaman, Yiğitcan, Lagore, Russell L., Ertürk, M. Arcan, Utecht, Lynn, Zhang, Patrick, Torrado‐Carvajal, Angel, Türk, Esra Abaci, DelaBarre, Lance, Metzger, Gregory J., Adriany, Gregor, Uğurbil, Kâmil, Vaughan, J. Thomas
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01-01-2018
• Subjects: 10.5 T; Animals; Calibration; Computer Simulation; Dipole antennas; dipole arrays; Dipoles; Electromagnetic Fields; Electromagnetic Radiation; Equipment Design; Error analysis; Errors; Excitation; Experiments; Fluoroscopy; Heating; Hot Temperature; Hyperthermia, Induced - instrumentation; Livestock; Magnetic resonance; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Mathematical models; Mean square errors; Models, Anatomic; Phantoms, Imaging; Radio frequency; Radio Waves; radiofrequency (RF); Root-mean-square errors; SAR; Simulation; Swine; temperature; Temperature effects; Thermal analysis; Tomography, X-Ray Computed; temperature; SAR; 10.5 T; dipole arrays; radiofrequency (RF)
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.26688

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.