Evaluation of RF Heating on Humerus Implant in Phantoms during 1.5T MR Imaging and Comparisons with Electromagnetic Simulation

URI http://harp.lib.hiroshima-u.ac.jp/hirokoku-u/metadata/7275
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Title
Evaluation of RF Heating on Humerus Implant in Phantoms during 1.5T MR Imaging and Comparisons with Electromagnetic Simulation
Author
氏名 村中 博幸
ヨミ ムラナカ ヒロユキ
別名 Muranaka Hiroyuki
氏名 堀口 隆良
ヨミ ホリグチ タカヨシ
別名 Horiguchi Takayoshi
氏名 笛吹 修治
ヨミ ウスイ シュウジ
別名 Usui Shuji
氏名 上田 善武
ヨミ ウエダ ヨシタケ
別名 Ueda Yoshitake
氏名 中村 修
ヨミ ナカムラ オサム
別名 Nakamura Osamu
氏名 池田 文昭
ヨミ イケダ フミアキ
別名 Ikeda Fumiaki
氏名 岩倉 健
ヨミ イワクラ ケン
別名 Iwakura Ken
氏名 中谷 儀一郎
ヨミ ナカヤ ギイチロウ
別名 Nakaya Giichirou
Subject
magnetic resonance imaging
metallic implant
RF heating
electromagnetic simulation
MRI safety
Abstract

Purpose: To evaluate the effect of radiofrequency (RF) heating on a metallic implant during magnetic resonance imaging (MRI), temperatures at several positions of an implant were measured, and results are compared with electromagnetic simulations using a finite element method.
Methods: A humerus nail implant made of stainless steel was embedded at various depths of tissue-equivalent gel-phantoms with loop (loop phantom) and partially cut loop (loop-cut phantom), and the phantoms were placed parallel to the static magnetic field of a 1.5T MRI device. Scans were conducted at maximum RF for 15 min, and temperatures were recorded with 2 RF-transparent fiberoptic sensors. Finally, electromagnetic-field analysis was performed.
Results: Temperatures increased at both ends of the implants at various depths, and temperature increase was suppressed with increasing depth. The maximum temperature rise was 12.3°C at the tip of the implant and decreased for the loop-cut phantom. These tendencies resembled the results of electromagnetic simulations.
Conclusion: RF heating was verified even in a nonmagnetizing metal implant in a case of excessive RF irradiation. Particularly, rapid temperature rise was observed at both ends of the implant having large curvatures. The difference in temperature increase by depth was found to reflect the skin-depth effect of RF intensity. Electromagnetic simulation was extremely useful for visualizing the eddy currents within the loop and loop-cut phantoms and for evaluating RF heating of a metallic implant for MRI safety.

Journal Title
Magnetic resonance in medical sciences : MRMS
Volume
5
Issue
2
Spage
79
Epage
88
Published Date
2006
Publisher
日本磁気共鳴医学会
ISSN
1347-3182
NCID
AA11648770
Language
eng
NIIType
Journal Article
Text Version
出版社版
Rights
本論文の著作権は日本磁気共鳴医学会に属する
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hirokoku-u