SAR and temperature: Simulations and comparison to regulatory limits for MRI

Zhangwei Wang, James C. Lin, Weihua Mao, Wanzhan Liu, Michael B. Smith, Christopher M. Collins

Research output: Contribution to journalArticle

84 Citations (Scopus)

Abstract

Purpose: To present and discuss numerical calculations of the specific absorption rate (SAR) and temperature in comparison to regulatory limits. While it is possible to monitor whole-body or whole-head average SAR and/or core body temperature during MRI in practice, this is not generally true for local SAR values or local temperatures throughout the body. While methods of calculation for SAR and temperature are constantly being refined, methods for interpreting results of these calculations in light of regulatory limits also warrant discussion. Materials and Methods: Numerical calculations of SAR and temperature for the human head in a volume coil for MRI at several different frequencies are presented. Results: Just as the field pattern changes with the frequency, so do the temperature distribution and the ratio of maximum local SAR (in 1-g or 10-g regions) to whole-head average SAR. In all of the cases studied here this ratio is far greater than that in the regulatory limits, indicating that existing limits on local SAR will be exceeded before limits on whole-body or whole-head average SAR are reached. Conclusion: Calculations indicate that both SAR and temperature distributions vary greatly with B1 field frequency, that temperature distributions do not always correlate well with SAR distributions, and that regulatory limits on local temperature may not be exceeded as readily as those on local SAR.

Original languageEnglish (US)
Pages (from-to)437-441
Number of pages5
JournalJournal of Magnetic Resonance Imaging
Volume26
Issue number2
DOIs
StatePublished - Aug 2007

Fingerprint

Temperature
Head
Body Temperature

Keywords

  • MRI
  • SAR
  • Simulations
  • Temperature, safety

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology

Cite this

Wang, Z., Lin, J. C., Mao, W., Liu, W., Smith, M. B., & Collins, C. M. (2007). SAR and temperature: Simulations and comparison to regulatory limits for MRI. Journal of Magnetic Resonance Imaging, 26(2), 437-441. https://doi.org/10.1002/jmri.20977

SAR and temperature : Simulations and comparison to regulatory limits for MRI. / Wang, Zhangwei; Lin, James C.; Mao, Weihua; Liu, Wanzhan; Smith, Michael B.; Collins, Christopher M.

In: Journal of Magnetic Resonance Imaging, Vol. 26, No. 2, 08.2007, p. 437-441.

Research output: Contribution to journalArticle

Wang, Z, Lin, JC, Mao, W, Liu, W, Smith, MB & Collins, CM 2007, 'SAR and temperature: Simulations and comparison to regulatory limits for MRI', Journal of Magnetic Resonance Imaging, vol. 26, no. 2, pp. 437-441. https://doi.org/10.1002/jmri.20977
Wang, Zhangwei ; Lin, James C. ; Mao, Weihua ; Liu, Wanzhan ; Smith, Michael B. ; Collins, Christopher M. / SAR and temperature : Simulations and comparison to regulatory limits for MRI. In: Journal of Magnetic Resonance Imaging. 2007 ; Vol. 26, No. 2. pp. 437-441.
@article{ec88744b13ef471fa181ade56e1b4b8d,
title = "SAR and temperature: Simulations and comparison to regulatory limits for MRI",
abstract = "Purpose: To present and discuss numerical calculations of the specific absorption rate (SAR) and temperature in comparison to regulatory limits. While it is possible to monitor whole-body or whole-head average SAR and/or core body temperature during MRI in practice, this is not generally true for local SAR values or local temperatures throughout the body. While methods of calculation for SAR and temperature are constantly being refined, methods for interpreting results of these calculations in light of regulatory limits also warrant discussion. Materials and Methods: Numerical calculations of SAR and temperature for the human head in a volume coil for MRI at several different frequencies are presented. Results: Just as the field pattern changes with the frequency, so do the temperature distribution and the ratio of maximum local SAR (in 1-g or 10-g regions) to whole-head average SAR. In all of the cases studied here this ratio is far greater than that in the regulatory limits, indicating that existing limits on local SAR will be exceeded before limits on whole-body or whole-head average SAR are reached. Conclusion: Calculations indicate that both SAR and temperature distributions vary greatly with B1 field frequency, that temperature distributions do not always correlate well with SAR distributions, and that regulatory limits on local temperature may not be exceeded as readily as those on local SAR.",
keywords = "MRI, SAR, Simulations, Temperature, safety",
author = "Zhangwei Wang and Lin, {James C.} and Weihua Mao and Wanzhan Liu and Smith, {Michael B.} and Collins, {Christopher M.}",
year = "2007",
month = "8",
doi = "10.1002/jmri.20977",
language = "English (US)",
volume = "26",
pages = "437--441",
journal = "Journal of Magnetic Resonance Imaging",
issn = "1053-1807",
publisher = "John Wiley and Sons Inc.",
number = "2",

}

TY - JOUR

T1 - SAR and temperature

T2 - Simulations and comparison to regulatory limits for MRI

AU - Wang, Zhangwei

AU - Lin, James C.

AU - Mao, Weihua

AU - Liu, Wanzhan

AU - Smith, Michael B.

AU - Collins, Christopher M.

PY - 2007/8

Y1 - 2007/8

N2 - Purpose: To present and discuss numerical calculations of the specific absorption rate (SAR) and temperature in comparison to regulatory limits. While it is possible to monitor whole-body or whole-head average SAR and/or core body temperature during MRI in practice, this is not generally true for local SAR values or local temperatures throughout the body. While methods of calculation for SAR and temperature are constantly being refined, methods for interpreting results of these calculations in light of regulatory limits also warrant discussion. Materials and Methods: Numerical calculations of SAR and temperature for the human head in a volume coil for MRI at several different frequencies are presented. Results: Just as the field pattern changes with the frequency, so do the temperature distribution and the ratio of maximum local SAR (in 1-g or 10-g regions) to whole-head average SAR. In all of the cases studied here this ratio is far greater than that in the regulatory limits, indicating that existing limits on local SAR will be exceeded before limits on whole-body or whole-head average SAR are reached. Conclusion: Calculations indicate that both SAR and temperature distributions vary greatly with B1 field frequency, that temperature distributions do not always correlate well with SAR distributions, and that regulatory limits on local temperature may not be exceeded as readily as those on local SAR.

AB - Purpose: To present and discuss numerical calculations of the specific absorption rate (SAR) and temperature in comparison to regulatory limits. While it is possible to monitor whole-body or whole-head average SAR and/or core body temperature during MRI in practice, this is not generally true for local SAR values or local temperatures throughout the body. While methods of calculation for SAR and temperature are constantly being refined, methods for interpreting results of these calculations in light of regulatory limits also warrant discussion. Materials and Methods: Numerical calculations of SAR and temperature for the human head in a volume coil for MRI at several different frequencies are presented. Results: Just as the field pattern changes with the frequency, so do the temperature distribution and the ratio of maximum local SAR (in 1-g or 10-g regions) to whole-head average SAR. In all of the cases studied here this ratio is far greater than that in the regulatory limits, indicating that existing limits on local SAR will be exceeded before limits on whole-body or whole-head average SAR are reached. Conclusion: Calculations indicate that both SAR and temperature distributions vary greatly with B1 field frequency, that temperature distributions do not always correlate well with SAR distributions, and that regulatory limits on local temperature may not be exceeded as readily as those on local SAR.

KW - MRI

KW - SAR

KW - Simulations

KW - Temperature, safety

UR - http://www.scopus.com/inward/record.url?scp=34547890652&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34547890652&partnerID=8YFLogxK

U2 - 10.1002/jmri.20977

DO - 10.1002/jmri.20977

M3 - Article

C2 - 17654736

AN - SCOPUS:34547890652

VL - 26

SP - 437

EP - 441

JO - Journal of Magnetic Resonance Imaging

JF - Journal of Magnetic Resonance Imaging

SN - 1053-1807

IS - 2

ER -