CEA, DSV, I2BM, NeuroSpin, LRMN, Gif-sur-Yvette, France.
J Magn Reson Imaging. 2012 Jun;35(6):1312-21. doi: 10.1002/jmri.23542. Epub 2012 Jan 12.
To investigate, via numerical simulations, the compliance of the specific absorption rate (SAR) versus temperature guidelines for the human head in magnetic resonance imaging procedures utilizing parallel transmission at high field.
A combination of finite element and finite-difference time-domain methods was used to calculate the evolution of the temperature distribution in the human head for a large number of parallel transmission scenarios. The computations were performed on a new model containing 20 anatomical structures.
Among all the radiofrequency field exposure schemes simulated, the recommended 39°C maximum local temperature was never exceeded when the local 10-g average SAR threshold was reached. On the other hand, the maximum temperature barely complied with its guideline when the global SAR reached 3.2 W/kg. The maximal temperature in the eye could very well rise by more than 1°C in both cases.
Considering parallel transmission, the recommended values of local 10-g SAR may remain a relevant metric to ensure that the local temperature inside the human head never exceeds 39°C, although it can lead to rises larger than 1°C in the eye. Monitoring temperature instead of SAR can provide increased flexibility in pulse design for parallel transmission.
通过数值模拟研究在高场磁共振成像中利用并行传输时，特定吸收率（SAR）与温度指南对人体头部的顺应性。
采用有限元与有限差分时域方法的组合，针对大量并行传输情况计算了人体头部温度分布的演变。计算是在包含 20 个解剖结构的新模型上进行的。
在所模拟的所有射频场暴露方案中，当达到局部 10-g 平均 SAR 阈值时，从未超过推荐的 39°C 最大局部温度。另一方面，当全局 SAR 达到 3.2 W/kg 时，最大温度几乎符合其指南。在这两种情况下，眼睛的最高温度都很可能上升超过 1°C。
考虑到并行传输，局部 10-g SAR 的推荐值仍然是一个相关指标，可以确保人体头部内部的局部温度永远不会超过 39°C，尽管这可能导致眼睛温度上升超过 1°C。与 SAR 相比，温度监测可为并行传输的脉冲设计提供更大的灵活性。
