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Radiofrequency induced heating around aneurysm clips using a generic birdcage head coil at 7 Tesla under consideration of the minimum distance to decouple multiple aneurysm clips.

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Title: Radiofrequency induced heating around aneurysm clips using a generic birdcage head coil at 7 Tesla under consideration of the minimum distance to decouple multiple aneurysm clips.
Authors: Noureddine, Yacine1,2 (AUTHOR) yacine.noureddine@gmail.com, Kraff, Oliver1 (AUTHOR), Ladd, Mark E.1,3,4 (AUTHOR), Wrede, Karsten1,5 (AUTHOR), Chen, Bixia1,5 (AUTHOR), Quick, Harald H.1,6 (AUTHOR), Schaefers, Gregor2,7 (AUTHOR), Bitz, Andreas K.3,8 (AUTHOR)
Source: Magnetic Resonance in Medicine. Nov2019, Vol. 82 Issue 5, p1859-1875. 17p.
Subjects: Radio frequency, Aneurysms, Birdcages, Distances, Head
Abstract: Purpose: To evaluate radiofrequency (RF) induced tissue heating around aneurysm clips during a 7T head MR examination and to determine the decoupling distance between multiple implanted clips. Methods: A total of 120 RF exposure scenarios of clinical relevance were studied using specific absorption rate and temperature simulations. Variations between scenarios included 2 clips (18.8 and 51.5 mm length), 2 MR‐operating modes, 2 head models, and 3 thermoregulation models. Furthermore, a conservative approach was developed to allow for safe scans of patients with aneurysm clips even if detailed information on the implanted clip is unknown. A dedicated simulation‐based approach was applied to determine the decoupling distance between multiple implanted clips. Results: For all 60 clinical scenarios with the 18.8‐mm‐long clip, the absolute tissue temperature remained below regulatory limits. For 15 of 60 scenarios with the 51.5‐mm‐long clip, limits were slightly exceeded (less than 1°C). The conservative approach led to a maximum time‐averaged input power of the RF coil of 3.3W. The corresponding B1+ is 1.32 µT. A decoupling distance of 35 mm allows the aneurysm clips to be treated as uncoupled from one other. Conclusion: Safe scanning conditions with respect to RF‐induced heating can be applied for single or decoupled aneurysm clips in a 7T ultra‐high field MRI setting. Multiple aneurysm clips separated by less than 35 mm need further investigations. [ABSTRACT FROM AUTHOR]
Copyright of Magnetic Resonance in Medicine is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Radiofrequency induced heating around aneurysm clips using a generic birdcage head coil at 7 Tesla under consideration of the minimum distance to decouple multiple aneurysm clips.
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  Data: <searchLink fieldCode="AR" term="%22Noureddine%2C+Yacine%22">Noureddine, Yacine</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<i> yacine.noureddine@gmail.com</i><br /><searchLink fieldCode="AR" term="%22Kraff%2C+Oliver%22">Kraff, Oliver</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Ladd%2C+Mark+E%2E%22">Ladd, Mark E.</searchLink><relatesTo>1,3,4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Wrede%2C+Karsten%22">Wrede, Karsten</searchLink><relatesTo>1,5</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Chen%2C+Bixia%22">Chen, Bixia</searchLink><relatesTo>1,5</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Quick%2C+Harald+H%2E%22">Quick, Harald H.</searchLink><relatesTo>1,6</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Schaefers%2C+Gregor%22">Schaefers, Gregor</searchLink><relatesTo>2,7</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Bitz%2C+Andreas+K%2E%22">Bitz, Andreas K.</searchLink><relatesTo>3,8</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22Magnetic+Resonance+in+Medicine%22">Magnetic Resonance in Medicine</searchLink>. Nov2019, Vol. 82 Issue 5, p1859-1875. 17p.
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  Data: <searchLink fieldCode="DE" term="%22Radio+frequency%22">Radio frequency</searchLink><br /><searchLink fieldCode="DE" term="%22Aneurysms%22">Aneurysms</searchLink><br /><searchLink fieldCode="DE" term="%22Birdcages%22">Birdcages</searchLink><br /><searchLink fieldCode="DE" term="%22Distances%22">Distances</searchLink><br /><searchLink fieldCode="DE" term="%22Head%22">Head</searchLink>
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  Label: Abstract
  Group: Ab
  Data: Purpose: To evaluate radiofrequency (RF) induced tissue heating around aneurysm clips during a 7T head MR examination and to determine the decoupling distance between multiple implanted clips. Methods: A total of 120 RF exposure scenarios of clinical relevance were studied using specific absorption rate and temperature simulations. Variations between scenarios included 2 clips (18.8 and 51.5 mm length), 2 MR‐operating modes, 2 head models, and 3 thermoregulation models. Furthermore, a conservative approach was developed to allow for safe scans of patients with aneurysm clips even if detailed information on the implanted clip is unknown. A dedicated simulation‐based approach was applied to determine the decoupling distance between multiple implanted clips. Results: For all 60 clinical scenarios with the 18.8‐mm‐long clip, the absolute tissue temperature remained below regulatory limits. For 15 of 60 scenarios with the 51.5‐mm‐long clip, limits were slightly exceeded (less than 1°C). The conservative approach led to a maximum time‐averaged input power of the RF coil of 3.3W. The corresponding B1+ is 1.32 µT. A decoupling distance of 35 mm allows the aneurysm clips to be treated as uncoupled from one other. Conclusion: Safe scanning conditions with respect to RF‐induced heating can be applied for single or decoupled aneurysm clips in a 7T ultra‐high field MRI setting. Multiple aneurysm clips separated by less than 35 mm need further investigations. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Magnetic Resonance in Medicine is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.1002/mrm.27835
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        Text: English
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      – SubjectFull: Radio frequency
        Type: general
      – SubjectFull: Aneurysms
        Type: general
      – SubjectFull: Birdcages
        Type: general
      – SubjectFull: Distances
        Type: general
      – SubjectFull: Head
        Type: general
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      – TitleFull: Radiofrequency induced heating around aneurysm clips using a generic birdcage head coil at 7 Tesla under consideration of the minimum distance to decouple multiple aneurysm clips.
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            NameFull: Noureddine, Yacine
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              M: 11
              Text: Nov2019
              Type: published
              Y: 2019
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