RF-related heating assessment of extracranial neurosurgical implants at 7T

Christina L. Sammet, Xiangyu Yang, Peter A. Wassenaar, Eric C. Bourekas, Brian A. Yuh, Frank Shellock, Steffen Sammet, Michael V. Knopp*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Scopus citations

Abstract

Purpose: The purpose was to evaluate radiofrequency (RF)-related heating of commonly used extracranial neurosurgical implants in 7-T magnetic resonance imaging (MRI). Materials and methods: Experiments were performed using a 7-T MR system equipped with a transmit/receive RF head coil. Four commonly used titanium neurosurgical implants were studied using a test procedure adapted from the American Society for Testing and Materials Standard F2182-11a. Implants (. n=. 4) were tested with an MRI turbo spin echo pulse sequence designed to achieve maximum RF exposure [specific absorption rate (SAR) level. =. 9.9. W/kg], which was further validated by performing calorimetry. Maximum temperature increases near each implant's surface were measured using fiberoptic temperature probes in a gelled-saline-filled phantom that mimicked the conductive properties of soft tissue. Measurement results were compared to literature data for patient safety. Results: The highest achievable phantom averaged SAR was determined by calorimetry to be 2.0. ±. 0.1. W/kg due to the highly conservative SAR estimation model used by this 7-T MR system. The maximum temperature increase at this SAR level was below 1.0. °C for all extracranial neurosurgical implants that underwent testing. Conclusion: The findings indicated that RF-related heating under the conditions used in this investigation is not a significant safety concern for patients with the particular extracranial neurosurgical implants evaluated in this study.

Original languageEnglish (US)
Pages (from-to)1029-1034
Number of pages6
JournalMagnetic Resonance Imaging
Volume31
Issue number6
DOIs
StatePublished - Jul 2013

Keywords

  • 7T
  • Heating
  • Implants
  • MRI safety
  • SAR
  • Ultra-high-field MRI

ASJC Scopus subject areas

  • Biophysics
  • Biomedical Engineering
  • Radiology Nuclear Medicine and imaging

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