Broadband Dielectric Properties of Ex Vivo Bovine Liver Tissue Characterized at Ablative Temperatures.
Broadband Dielectric Properties of Ex Vivo Bovine Liver Tissue Characterized at Ablative Temperatures.
复制标题
在烧蚀温度下特征的离体牛肝组织的宽带介电特性。
DOI：
10.1109/tbme.2020.2996825
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发表时间：
2021-01
期刊：
影响因子：
--
通讯作者：
Prakash P
中科院分区：
文献类型：
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作者：
Fallahi H;Sebek J;Prakash P
为了研究在500 MHz至6 GHz、20℃至130℃温度范围内，离体肝组织的介电特性(相对介电常数和有效电导率)与温度和频率的关系，我们使用开放式同轴探针法(n=15)测量了新鲜离体牛肝组织的介电特性。利用数值优化技术得到了表征宽带介电性能随温度和热等效剂量变化的参数模型。研究了在6.4-16.9℃/min范围内加热组织的效果。测量的介电特性被用于模拟微波烧蚀，以评估与实验测量相比较的模拟天线回波损耗的变化。在所有频率范围内，相对介电常数和有效电导率都在-107℃温度范围内急剧下降。在91℃以下，有效电导率的斜率在较低频率(0.5-1.64 GHz)时为正值，在较高频率(1.64-6 GHz)时为负值。采用与温度和热剂量相关的介电参数时，测量和模拟得到的瞬时反射系数之间的最大相关值分别在0.83-0.89和0.68-0.91之间。我们提出了描述牛肝组织在消融温度下介电特性变化的实验测量和参数模型。所提出的介电特性模型将有助于在2.45 GHz以外的频率下工作的消融系统的发展，以及用于监测微波消融区生长的宽带技术。
To investigate the thermal and frequency dependence of dielectric properties of ex vivo liver tissue – relative permittivity and effective conductivity – over the frequency range of 500 MHz to 6 GHz and temperatures ranging from 20 to 130 °C. We measured the dielectric properties of fresh ex vivo bovine liver tissue using the open-ended coaxial probe method (n =15 samples). Numerical optimization techniques were utilized to obtain parametric models for characterizing changes in broadband dielectric properties as a function of temperature and thermal isoeffective dose. The effect of heating tissue at rates over the range 6.4–16.9 °C/min was studied. The measured dielectric properties were used in simulations of microwave ablation to assess changes in simulated antenna return loss compared to experimental measurements. Across all frequencies, both relative permittivity and effective conductivity dropped sharply over the temperature range 89 – 107 °C. Below 91 °C, the slope of the effective conductivity changes from positive values at lower frequencies (0.5–1.64 GHz) to negative values at higher frequencies (1.64–6 GHz). The maximum achieved correlation values between transient reflection coefficients from measurements and simulations ranged between 0.83 – 0.89 and 0.68 – 0.91, respectively, when using temperature-dependent and thermal-dose dependent dielectric property parameterizations. We have presented experimental measurements and parametric models for characterizing changes in dielectric properties of bovine liver tissue at ablative temperatures. The presented dielectric property models will contribute to the development of ablation systems operating at frequencies other than 2.45 GHz, as well as broadband techniques for monitoring growth of microwave ablation zones.