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Feasibility of measuring thermoregulation during RF heating of the human calf muscle using MR based methods
Author(s) -
Simonis Frank F.J.,
Petersen Esben T.,
Lagendijk Jan J.W.,
den Berg Cornelis A.T.
Publication year - 2016
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.25710
Subject(s) - thermoregulation , perfusion , nuclear medicine , dielectric heating , specific absorption rate , percentile , biomedical engineering , skin temperature , radio frequency , materials science , nuclear magnetic resonance , medicine , chemistry , cardiology , mathematics , physics , computer science , telecommunications , statistics , antenna (radio) , optoelectronics , dielectric
Purpose One of the main safety concerns in MR is heating of the subject due to radiofrequency (RF) exposure. Recently was shown that local peak temperatures can reach dangerous values and the most prominent parameter for accurate temperature estimations is thermoregulation. Therefore, the goal of this research is testing the feasibility of measuring thermoregulation in vivo using MR methods. Theory and Methods The calves of 13 volunteers were scanned at 3 tesla. A Proton Resonance Frequency Shift method was used for temperature measurement. Arterial Spin Labeling and phase contrast scans were used for perfusion and flow measurements respectively. The calves were monitored during extreme RF exposure (20 W/kg, 16 min) and after physical exercise. Results Temperature increases due to RF absorption (range of the 90th percentile of all volunteers: 1.1–2.5°C) matched with the reference skin temperature changes. Increases in perfusion and flow were defined on the whole leg and normalized to baseline. Perfusion showed a significant increase due to RF heating (ratio compared with baseline: 1.28 ± 0.37; P < 0.05), the influence of exercise was much greater, however (2.97 ± 2.45, P < 0.01). Conclusion This study represents a first exploration of measuring thermoregulation, which will become essential when new safety guidelines are based on thermal dose. Magn Reson Med 75:1743–1751, 2016. © 2015 Wiley Periodicals, Inc.