Simonis Frank F J, Petersen Esben T, Lagendijk Jan J W, van den Berg Cornelis A T
Department of Radiotherapy, Imaging Division, University Medical Center Utrecht, Utrecht, the Netherlands.
Magn Reson Med. 2016 Apr;75(4):1743-51. doi: 10.1002/mrm.25710. Epub 2015 May 14.
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.
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.
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).
This study represents a first exploration of measuring thermoregulation, which will become essential when new safety guidelines are based on thermal dose.
磁共振成像（MR）中的主要安全问题之一是射频（RF）暴露导致受检者发热。最近的研究表明，局部峰值温度可能达到危险值，而准确估计温度的最显著参数是体温调节。因此，本研究的目的是测试使用MR方法在体内测量体温调节的可行性。
对13名志愿者的小腿进行3特斯拉的扫描。采用质子共振频率偏移法测量温度。分别使用动脉自旋标记和相位对比扫描测量灌注和血流。在极端RF暴露（20 W/kg，16分钟）期间和体育锻炼后对小腿进行监测。
由于RF吸收导致的温度升高（所有志愿者第90百分位数范围：1.1 - 2.5°C）与参考皮肤温度变化相符。全腿灌注和血流增加，并以基线进行归一化。由于RF加热，灌注显示出显著增加（与基线相比的比值：1.28±0.37；P < 0.05），然而，运动的影响更大（2.97±2.45，P < 0.01）。
本研究首次探索了测量体温调节，当新的安全指南基于热剂量时，这将变得至关重要。
