期刊
MAGNETIC RESONANCE IMAGING
卷 31, 期 6, 页码 1029-1034出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/j.mri.2012.10.025
关键词
7 T; Ultra-high-field MRI; MRI safety; Implants; SAR; Heating
资金
- Wright Center of Innovation in Biomedical Imaging
- [ODOD AGMT TECH 03-051]
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 degrees 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. (C) 2013 Elsevier Inc. All rights reserved.
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