Basic Studies On Impedance Spectroscopy Measurement Methods And Characteristics Of Lung Tissue

Biological tissue impedance spectroscopy is an intrinsic biophysical property; itcontains a wealth of physiological and pathological information and shows that thecomplex impedance of biological tissue varies with the frequency of driven currentchange.Our basic studies have several aspects: quantitative analysis of dielectricproperties of human lung tissue with different pulmonary air content; study thedifferences of dielectric properties between cancerous tissues and human lung normaltissues which have the same air content; study the differences of different types ofcancerous tissue impedance spectra; establishment of database management systemsof lung tissue impedance spectroscopy. These studies are aimed to provide the basictheory and reference data for medical research and clinical diagnosis.This paper focuses on the study of impedance spectroscopy measurementmethods and characteristics of human lung tissue. The main work includes threeaspects:1. Two main categories of tissues were considered as specimens: the central partof the tumor and the normal tissue around the tumor, which were sampled by lungtumor resection operation. Specimens’ impedance spectra measurement wasperformed at frequency from100Hz to100MHz using4294A impedance analyzer ofAgilent Company and test chamber’s temperature and humidity were controlled atexpected values. Impedance characteristic parameters were extracted by using theleast square curve fitting method based on Cole-Cole model. An air filling factor F isdefined, which is determined from the mass and volume of the specimen, fordescribing pulmonary air content. The results show that dielectric properties of lungtissue are a function of air content and decrease with increasing F. Comparisonsbetween different types of cancerous tissues find that small cell carcinoma impedancespectra is significant difference compared with the other three epithelial carcinoma.The results show that we can distinguish these two types of lung cancer from theperspective of biophysics and provide theoretical basis for lung cancer clinicaldiagnosis and treatment. 2. Comparisons between cancerous and normal tissue find that the relativepermittivity of cancerous tissue is1.2~3times larger than that of the normal tissuewith F=0.1781, the conductivity of cancerous tissue is1.6~2times larger than that ofthe normal tissue and the greatest difference occurs at1kHz. Among the impedancecharacteristic parameters (R0, R,, andf c), the difference of low frequencyresistance () between the two categories of tissues is statistically significant.Impedance spectroscopy of lung cancer tissue moves apparently to low impedancedirection. It is concluded that the differences of dielectric properties and lowfrequency resistance between cancerous and normal tissues are significant and whichprovide theoretical basis and reference data for electrical impedance tomographytechnology used in monitoring pulmonary function.3. we setup the database management systems of lung tissue impedancespectroscopy using Visual C++6.0and Access2000. The program prepares a friendlyinterface to connect with the background database management system through ADOtechnology. The program of lung tissue impedance spectroscopy database can realizedata sharing and facilitate the retrieval and use of data.