蒸馏水和NaCl溶液复介电常数的测量及修正

分别测量2450MHz频率下蒸馏水和不同浓度NaCl溶液的复介电常数,并对测量数据进行统计分析和修正,这对于研究利用微扰法测量高损耗生物组织的复介电常数,具有十分重要的意义。     

不同灌注介质对射频消融病灶大小影响体外研究

目的探讨在离体状态下，采用不同种类及浓度的离子溶液作为灌注介质对射频消融灶大小的影响。方法在新鲜猪肝内进行射频消融。按灌注介质不同，分为质量浓度25％乙酸溶液、质量浓度10％NaCl溶液、质量浓度5％NaCl溶液、质量浓度0．9％NaCl溶液、体积分数95％乙醇溶液及蒸馏水6组进行实验。每组实验重复8次。射频结束后将其剖开测量并比较消融灶的形态及体积。结果共得到48个消融灶。不同灌注介质所形成的消融灶体积按从大到小依次排列如下：质量浓度25％乙酸溶液组〉质量浓度10％NaCl溶液组〉质量浓度5％NaCl溶液组〉质量浓度0．9％NaCl溶液组〉蒸馏水组〉体积分数95％乙醇溶液组。结论采用高浓度的离子溶液作为灌注介质在体外条件下有助于形成较大的射频消融灶。     

空气与填充同轴探头测量生物组织高频介电特性差异性研究

本文基于等效电路模型，对空气探头与填充探头测量生物组织高频介电特性的差异开展研究，为生物组织介电特性高频测量方法学提供参考。在100 MHz～2 GHz频段采用两种类型探头对不同浓度NaCl溶液进行测量。结果显示：由于测量时液体容易侵入探头内腔，空气探头测量计算结果的准确性与可靠性要低于填充探头，特别是被测物的介电系数，且NaCl溶液浓度越高误差越高。通过对探头终端进行覆膜可以阻止液体侵入，在一定程度上可提高测量准确度。但随着频率的降低，膜对测量的影响增大，测量准确性也随之降低。研究结果表明：空气探头尽管尺寸设计简单且容易定标，但在实际测量中与传统等效电路模型存在差异，实际使用时需要重新对模型进行修正。填充探头与等效电路模型匹配度较高，因此具有较好的测量准确性和可靠性。     

骨肿瘤微波等效体模的配置及其介电常数的测量

本文介绍了2450MHz骨肿瘤微波等效体模的配制方法，利用模拟六端口反射计测试系统测量了等效体模的介电常数，并与骨肿瘤组织的介电常数进行比较。结果证明该体模与骨肿瘤组织等效。     

30例健康人血液射频介电常数和电导率的测量

在10kHz～110MHz频率范围,利用4294A阻抗分析仪测量了30例正常健康人血液样本的介电常数和电导率,通过介电常数和电导率频谱、复数平面图、介电损耗频谱、电导率虚部频谱和损耗角正切频谱的数据分析,旨在建立正常人血液的电生理特征参数,为进一步的临床研究提供基础数据和研究方法。结果表明,正常健康人全血介电常数和电导率具有频率依从性,其介电行为具有两个特征频率：第一特征频率f1=0.59MHz;第二特征频率f2=2.12MHz。     

低温下脂肪在8～12GHz频率内的介电常数与电导率测量

在生物组织的低温保存中,微波复温和降温方法得到了广泛研究,但低温下材料物性参数一直比较缺乏.为研究微波复温的加热过程和微波降温的非热效应提供物性参数,并对其机理进行探索,本文应用波导传输发射法测量生物组织在-43～30℃,频率为8～12GHz时的介电常数与电导率.首先通过测量有机材料对测量系统进行验证,证明本文所提出的系统具有较好的测量精度与可重复性,然后测量了在生物组织中分布很广的脂肪的介电常数与电导率,给出了几组样品的实验测量值,并讨论了单个样品的介电常数与电导率随温度和频率变化的规律.     

MTT检测超声激活血卟啉对SW-480细胞的杀伤作用

本实验采用1.1、1.6、2.3MHz频率聚焦超声结合血卟啉的方式对体外培养的人结肠癌细胞SW-480进行照射,其介质分别为NaCl溶液、PRMI1640、完全培养基,并采用MTT法测试SDT对肿瘤细胞的杀伤效果。结果表明:SW-480细胞在声照强度为1.5W/cm2 ,频率2.3 MHz条件下,介质为NaCl溶液、PRMI1640和完全培养基中都存在超声激活血卟啉增强杀伤肿瘤细胞的效果,且在PRMI1640和完全培养基中这种效果和处理后细胞孵育的时间有一定的相关性。     

生物物质的介电测量技术

本文根据传输线法介电测量原理建立起100KHz～500MHz频率范围的生物物质介电测量系统,该系统由网络分析仪、同轴线腔式传感器及测温控温装置等组成,并由计算机实现自动采样与分析。对测量误差的来源作了详细分析,一定修正和补偿条件下,本文制做的腔式传感器适用于整个频率范围。对人全血和人脑组织等高含水量物质的介电常数测量误差小于3％,电导率误差小于2％。     

三千兆赫微波波段复合介质介电常数的测量

本文从理论上导出了复合介质的介电常数的计算公式。并应用10厘米(3千兆赫)微波系统,测出了一种复合介质的介电常数。实验结果与用计算公式计算的结果得到较好的符合。     

利用计算机立体视觉原理建立乳房体积测量系统

目的:运用计算机立体测量技术建立乳房体积计算机立体测量系统.方法:(1)采用计算机立体视觉原理,设计乳房体积测量运算模式,编制乳房体积测量分析程序.(2)所建立的乳房体积测量系统系统和传统的水体积置换方法测试对照,然后将测试的结果进行配对t检验,研究本系统的精确性和可靠性.结果:(1)实现了数据的快速处理,测试空间范围为120 mm×140 mm×80mm,精确度最大误差为0.9mm.(2)本系统测量乳房体积,特别是快速、非接触和非侵入.与金标准水体积置换方法比较,P=0.485＞0.05,差值的95%可信区间为(-14.0177,7.0843),说明本系统测试方法精确度高,可靠性强.结论:(1)本系统可应用于乳房体积测量,简捷而且精确,为临床工作提供了一种有效实验手段.(2)本系统为软组织形态分析的技术领域提供了一种新的技术方法.     

A quick accurate method for measuring the microwave dielectric properties of small tissue samples.

A resonant cavity perturbation technique has been developed which provides a quick, simple and accurate method of measuring the microwave dielectric properties of small, easily prepared samples of tissues, tissue-simulating materials and biological fluids. The method gives dielectric properties averaged over the sample volume. The measurement accuracy with the apparatus used is +/- 2.2% for relative permittivity and +/- 3.5% for the loss factor for most tissue and biological material samples. With appropriate basic microwave equipment the method can be applied over the 1.5-6 GHz range of frequencies of interest for active and radiometric tissue microwave imaging.     

New materials for dielectric simulation of tissues.

Two novel materials have been developed to simulate the dielectric properties of human muscle and fat at 1000 MHz. These materials, which are based on ethanediol set with gelatine, are easily made and have good mechanical properties. The complex permittivity, epsilon *, of each material was measured with an open-ended coaxial sensor in conjunction with an automatic network analyser. Values of epsilon * at 1000 MHz and room temperature (49.4-24.4j for the muscle-equivalent material, 8.2-3.6j for the fat-equivalent) compared well with literature values for tissue at body temperature. Thermal properties were also considered. Specific heat capacities of the materials at room temperature were measured by differential scanning calorimetry and found to be very close to values predicted by theory. Densities were also measured and the thermal conductivities estimated. For comparison, new measurements were made of the specific heat and density of human muscle and fat at body temperature.     

Dielectric detection on human skin by in-vivo measuring technique

1.INTRODUCTIONThein-vivodielectricpropettiesoftissuesareofpracticalinterestduetofurtherresearchontheiflteractionmechanismofelectromagneticwavesintherangeofradioandmicrowavefrequencieswithbiologicalsystems.Itisalsoesselltialtohavethein-vivodielectric.parametersindeterminingthespecificabsorptionrateanditsdistriblltioninasimplifiedanimalorhumanmodel.Althoughanumberofinvestigatorshavemeasuredthedielectricpropertiesofvariousmammarytissuesoverawidefrequencyrange['-#]4fewinvivostudyonhumanskinsur…     

正常人血小板射频段介电响应测量

目的在射频段测量正常人血小板介电谱,建立血小板对交流电场介电响应的数据特征。方法利用频域阻抗技术测量人血小板交流阻抗,经过介电谱、Cole-Cole图、介电损耗因子Δε”、导电率虚部Δκ”、介电损耗角正切Δtgδ等频谱,明确人血小板介电频响的数据特征。结果在射频电场中,人血小板的介电常数和电导率具有频率依赖性;血小板介电响应具有两个中心特征频率:第一中心特征频率fC1=6.66MHz,第二中心特征频率fC2=9.81MHz。结论交流阻抗技术能够测量血小板射频段介电响应。     

Sielectric Properties of Terahertz Windows Materials for Bio-sample Measurement

We presented the dielectric properties of three materials for bio-sample measurement using THz transmission spectroscopy.The materials,PE,COC and PVDF,have sufficient transmittance.The results demonstrate that PVDF membranes are suitable media for THz transmission spectrum above 0.3 THz.However,it is not property to measure the solution sample because of the water existed after active processing by ethanol.In this paper,the refractive index,the absorption coefficient,and the complex dielectric functions in the THz region are compared for each material.From the measured dielectric properties,the loss mechanism of THz radiation for each material is also discussed.     

Dielectric properties of ocular tissues in the supercooled and frozen states

Values of the relative permittivity and conductivity of the rabbit retina and lens have been measured between 10 MHz and 10 GHz over the temperature range 20 to -20 degrees C. As the temperature was lowered from 20 degrees C the dielectric parameters changed smoothly until -9 degrees C where freezing occurred. At this temperature a sharp transition was observed in both conductivity and relative permittivity, the latter falling to a value of below 10 over most of the frequency range. Analysis shows that this is due to the unfreezable water, from which a value of lens hydration is calculated. This value agrees with that obtained previously at 37 degrees C using conventional dielectric mixture theory, but the associated margin of error is much smaller.