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 B(1) 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. (c) 2007 Wiley-Liss, Inc.
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 B(1) 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. (c) 2007 Wiley-Liss, Inc.
Authors: Uyen D Nguyen; J Steven Brown; Isaac A Chang; Joseph Krycia; Mark S Mirotznik Journal: IEEE Trans Biomed Eng Date: 2004-08 Impact factor: 4.538
Authors: Gregor Adriany; Pierre-Francois Van de Moortele; Florian Wiesinger; Steen Moeller; John P Strupp; Peter Andersen; Carl Snyder; Xiaoliang Zhang; Wei Chen; Klaas P Pruessmann; Peter Boesiger; Tommy Vaughan; Kāmil Uğurbil Journal: Magn Reson Med Date: 2005-02 Impact factor: 4.668
Authors: Yusuf A Bhagat; Chamith S Rajapakse; Jeremy F Magland; James H Love; Alexander C Wright; Michael J Wald; Hee Kwon Song; Felix W Wehrli Journal: J Magn Reson Imaging Date: 2011-02 Impact factor: 4.813
Authors: Johannes B Erhardt; Thomas Lottner; Jessica Martinez; Ali C Özen; Martin Schuettler; Thomas Stieglitz; Daniel B Ennis; Michael Bock Journal: Neuroimage Date: 2019-03-29 Impact factor: 6.556
Authors: Shizhe Li; Yan Zhang; Shumin Wang; Maria Ferraris Araneta; Christopher S Johnson; Yun Xiang; Robert B Innis; Jun Shen Journal: NMR Biomed Date: 2010-10 Impact factor: 4.044
Authors: Sukhoon Oh; Yeun-Chul Ryu; Giuseppe Carluccio; Christopher T Sica; Christopher M Collins Journal: Magn Reson Med Date: 2013-06-26 Impact factor: 4.668
Authors: Napapon Sailasuta; Larry W Robertson; Kent C Harris; Andrea L Gropman; Peter S Allen; Brian D Ross Journal: J Magn Reson Date: 2008-09-17 Impact factor: 2.229