MEDLINE/PubMed Journal Browser Search

Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

Title: [Sensing volume of tissue dielectric property measurement with open-ended coaxial probe].
Author: Liu Y, Huang Y, Xin X, Yu X.
Journal: Nan Fang Yi Ke Da Xue Xue Bao; 2020 Jul 30; 40(7):1036-1043. PubMed ID: 32895168.
Abstract:
OBJECTIVE: To investigate the sensing volume of open-ended coaxial probe technique for measurement of dielectric characteristics. METHODS: A measurement model combining macro- measurement device with a layer model of dielectric properties parameters was established for evaluating the sensing volume of open-ended coaxial probe technique. We defined sensing depth and sensing diameter to describe the distance that could be detected in vertical and horizontal direction. Using a variety of materials with different dielectric properties (Teflon, deionized water, ethanol, and gradient concentration sodium chloride solution), a layered model of dielectric properties differentiation was established. The total combined uncertainties (TCU) were calculated for different output power, and the output power was controlled to increase from -50 dBm to 15 dBm to calibrate the error range of the dielectric properties measurement system. The optimal output power range was determined based on the results of TCU test. In sensing volume measurement experiment, we set the control groups based on measurement parameters that potentially affect the sensing volume including output power (-10, -5, 0, 3, 6, and 9 dBm), frequency (1-500 MHz), Teflon, deionized water, and ethanol to form a dielectric constant difference between high and low contrast groups. Different concentrations of sodium chloride solution and Teflon were used to generate a conductivity difference between high and low contrast groups. These groups were tested in the sensing depth and sensing diameter measurement experiments. RESULTS: The result of TCU test indicated that accurate and stable measurement results could be obtained when the output power was greater or equal to-10 dBm (TCU < 2%). Sensing volume measurement experiment revealed a positive correlation between the sensing depth and output power (P < 0.05). As the measured power increased, the sensing depth gradually increased in deionized water and ethanol, and the difference reached 70 μm. The sensing depth was negatively correlated frequency (P < 0.05). As the concentration of sodium chloride solution increased, the corresponding sensing depth gradually decreased, with a difference reaching 270 μm. The sensing depth of high dielectric materials was greater than that pf low dielectric materials. The results of sensing diameter measurement were not obviously affected by the measurement parameters, and the sensing diameter was stable in a fixed range (1.0 to 1.8 mm) between the diameter of the inner conductor and the diameter of the insulation layer, and was less than the diameter of the probe. CONCLUSIONS: The sensing volume of open-ended coaxial probe technique is affected by measurement parameters and dielectric properties of materials, which significantly affect the sensing depth. 目的: 研究开端同轴探头法测量介电特性参数的感应范围。方法: 利用介电特性参数分层模型结合微距测量装置的方式建立开端同轴探头法感应范围的测量模型，以感应深度表示垂直方向感应范围，以感应直径表示水平方向感应范围。利用介电特性参数存在差异的多种材料（特氟龙、去离子水、乙醇、梯度浓度氯化钠溶液），设置了介电特性差异化分层模型。为标定不同输出功率下介电特性测量系统的误差范围，我们测定了不同输出功率环境下的合成不确定度（TCU），确定测量实验最佳可变功率范围。感应范围测量实验中，根据可能对感应范围造成影响的测量参数设置对照组，包括功率（-10、-5、0、3、6、9 dBm）、频率（1~500 MHz）、特氟龙与去离子水、乙醇形成介电常数[ε]差异高低对比组、特氟龙与不同浓度氯化钠溶液形成电导率[σ]差异高低对比组，上述分组均被设置在感应深度与感应直径测量实验中。结果: 合成不确定度测量结果表明测量功率大于-10 dBm（0.10 mW）可以得到相对准确的测量结果（TCU < 2%）。感应深度测量结果表明感应深度与功率正相关（P < 0.05）随着测量功率上升感应深度在去离子水与乙醇溶液中逐渐增大，差异达到70 μm；感应深度与被测物电导率负相关（P < 0.05），随着氯化钠溶液浓度的上升，对应感应深度逐渐下降，差异达到270 μm；高介电常数的去离子水测量组感应深度在不同测量参数环境下均大于低介电常数的乙醇测量组。测量参数变化对感应直径影响不显著，不同测量参数环境下感应直径稳定在固定范围内（1.0~ 1.8 mm），介于在探头内导体直径与绝缘层直径之间，小于探头直径。结论: 开端同轴探头法测量介电特性感应范围受测量参数与被测物介电特性参数共同影响，其中感应深度受影响较大。

[Abstract] [Full Text] [Related] [New Search]