The Sensing Range Of Dielectric Properties Of Human Tissues And Its Applications In Breast Tissue

Tissue dielectric properties refer to the ability of biological tissues to store and dissipate electromagnetic energy under the action of electromagnetic fields.They are usually expressed in terms of relative permittivity εr and electrical conductivity σ(S/m),as the basic physical parameters of biological tissues.Electrical properties can reflect the changes in the physiological and pathological state of tissues.The dielectric properties of tumor tissues and normal tissues are generally different.By measuring the dielectric properties of tissues,it is possible to provide reference information for distinguishing benign and malignant tissues.At this stage,the clinical applications of measuring the difference in dielectric properties between tissues in vivo including:real-time detection of the edges of malignant tissues during surgery,magnetic resonance electrical characteristic tomography(MR EPT),microwave breast imaging technology,etc.The open-ended coaxial probe method,as a common method for measuring the dielectric properties of tissues,has been widely used in a considerable number of studies on the dielectric properties of tissues.However,there is still a lack of detailed reports on the sensing range of this method.This research focuses on the sensing range and influencing factors of the open-ended coaxial probe method,including the size of the open-ended coaxial probe,the output power of the network analyzer and the dielectric characteristics of the measured object,and design the in-vivo measurement program of the dielectric properties of breast tissue is introduced.Intraoperative malignant tissue edge real-time detection technology assists doctors in judging the pathological state of the target tissue area by measuring the dielectric properties of the target tissue area,and then judging the position of the resection margin and the scope of resection,so as to preserve the best benign tissue for the patient in order to obtain a better prognosis.The measurement range of the dielectric properties of human tissue directly affects the accuracy of the measurement results.For this reason,we have studied many factors that affect the measurement range.We explored the relationship between output power and measurement error.When the output power of the network analyzer is less than-10dBm,the error range cannot meet the requirements for distinguishing the dielectric properties of different tissues.Increasing power will increase the sensing range to a certain extent.Theoretical analysis and simulation experiment It shows that the sensing range is positively correlated with the diameter of the probe.The actual measurement experiment of the sensing range shows that for an open-end coaxial probe with a diameter of 3.58mm,the sensing depth in deionized water and ethanol under 15dBm is increased by 7.9%,respectively,compared with that under-10dBm.9.8%.We explored the feasibility of breast dielectric properties measurement technology to identify breast cancer in vivo,as well as the design scheme of the breast dielectric properties measurement system in vivo,and established a multi-layered tissue composite dielectric properties model in COMSOL 5.6,and then used A patch antenna that can be used in human tissue to achieve impedance matching.The reflection coefficient S11 is simulated on a model containing normal breast tissue and breast cancer tissue over a wide frequency band.The simulation results show that when the subcutaneous fat of the model contains breast cancer tissue,its S11 curve will change its resonance frequency and corresponding peak value compared with the S11 curve of tissue without breast cancer.When the patch antenna is located above the horizontally arranged breast model,The S11 curve changes significantly.In order to meet the test requirements of breast dielectric properties in vivo measurement,we designed and produced a dielectric properties phantom similar to breast anatomy for in vivo measurement of breast dielectric properties and assisted breast cancer electrical properties tomography technology Development.The results of this research can be applied to real-time detection of malignant tissue edges in clinical operations,and also provide a new non-invasive detection method for early screening of breast cancer,at the same time can provide support for magnetic resonance electrical characteristics of breast tomography technology.