Rodrigues D B, Stauffer P R, Colebeck E, Hood A Z, Salahi S, Maccarini P F, Topsakal E
Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Department of Electrical and Computer Engineering, Mississippi State University, Starkville, MS 39762, USA.
Biomed Phys Eng Express. 2016;2. doi: 10.1088/2057-1976/2/2/025005. Epub 2016 Mar 22.
Brown adipose tissue (BAT) plays an important role in whole body metabolism and with appropriate stimulus could potentially mediate weight gain and insulin sensitivity. Although imaging techniques are available to detect subsurface BAT, there are currently no viable methods for continuous acquisition of BAT energy expenditure. Microwave (MW) radiometry is an emerging technology that allows the quantification of tissue temperature variations at depths of several centimeters. Such temperature differentials may be correlated with variations in metabolic rate, thus providing a quantitative approach to monitor BAT metabolism. In order to optimize MW radiometry, numerical and experimental phantoms with accurate dielectric properties are required to develop and calibrate radiometric sensors. Thus, we present for the first time, the characterization of relative permittivity and electrical conductivity of brown (BAT) and white (WAT) adipose tissues in rats across the MW range 0.5-10GHz. Measurements were carried out and in six female rats of approximately 200g. A Cole-Cole model was used to fit the experimental data into a parametric model that describes the variation of dielectric properties as a function of frequency. Measurements confirm that the dielectric properties of BAT ( = 14.0-19.4, = 0.3-3.3S/m) are significantly higher than those of WAT ( = 9.1-11.9, = 0.1-1.9S/m), in accordance with the higher water content of BAT.
棕色脂肪组织（BAT）在全身新陈代谢中发挥着重要作用，在适当刺激下可能介导体重增加和胰岛素敏感性。尽管有成像技术可用于检测皮下棕色脂肪组织，但目前尚无可行的方法来持续获取棕色脂肪组织的能量消耗。微波辐射测量是一种新兴技术，可对几厘米深度处的组织温度变化进行量化。这种温度差异可能与代谢率变化相关，从而提供一种监测棕色脂肪组织代谢的定量方法。为了优化微波辐射测量，需要具有精确介电特性的数值和实验模型来开发和校准辐射传感器。因此，我们首次展示了大鼠棕色（BAT）和白色（WAT）脂肪组织在0.5 - 10GHz微波范围内的相对介电常数和电导率特性。对大约200克重的六只雌性大鼠进行了测量。使用Cole - Cole模型将实验数据拟合到一个参数模型中，该模型描述了介电特性随频率的变化。测量结果证实，棕色脂肪组织的介电特性（ε = 14.0 - 19.4，σ = 0.3 - 3.3S/m）显著高于白色脂肪组织（ε = 9.1 - 11.9，σ = 0.1 - 1.9S/m），这与棕色脂肪组织较高的含水量一致。
