Shapiro E M, Borthakur A, Reddy R
Departments of Chemistry and Radiology, MMRRCC, B1 Stellar Chance Laboratory, University of Pennsylvania, 422 Curie Blvd., Philadelphia, PA 19104, USA.
MAGMA. 2000 Jun;10(2):114-21. doi: 10.1007/BF02601846.
In this paper, we present the first description of a technique to visualize and quantitate radiofrequency (RF) heating of a tissue phantom during a magnetic resonance imaging (MRI) procedure. We evaluated the heating patterns of four 10 cm diameter transmit/receive surface coils with differing degrees of distributed capacitance. The tissue phantom was a 6% agarose gel doped with 40 mM Na(4)HTm[DOTP], and possesses a conductivity intermediate to human muscle and fat. Heating was discerned via phase difference mapping using the large temperature dependent chemical shift coefficient for 23Na in Na(4)HTm[DOTP]. This coefficient is -0.5 ppm/ degrees C. Heating was highest where the phantom was closest to the surface coils, dropping off towards the center of the coil. No significant difference was observed in the heating patterns between the different surface coils. For the experimental setups used in this study, electric field 'hot spots' at the areas corresponding to the placement of the capacitor gaps were not observed.
在本文中，我们首次描述了一种在磁共振成像（MRI）过程中可视化和定量组织模型射频（RF）加热的技术。我们评估了四个直径为10厘米、具有不同分布电容程度的发射/接收表面线圈的加热模式。组织模型是掺杂有40 mM Na(4)HTm[DOTP]的6%琼脂糖凝胶，其电导率介于人体肌肉和脂肪之间。利用Na(4)HTm[DOTP]中23Na的大温度依赖性化学位移系数，通过相位差映射来识别加热情况。该系数为-0.5 ppm/℃。在模型最靠近表面线圈的地方加热最高，朝着线圈中心下降。不同表面线圈之间的加热模式未观察到显著差异。对于本研究中使用的实验设置，在与电容器间隙放置相对应的区域未观察到电场“热点”。
