| Breast cancer is the most common malignant tumor that threatens the health and even lives of women.It is an important factor of prognosis of breast cancer that whether early breast cancer is detected and reasonable therapy strategy is set down.But the currently available clinical examination instruments don't fit the general breast survey of the woman because of their limitations in clinical application.As the commonly used early detection method,mammography has high cost and brings pain and damage of X-ray to patients,and is not suitable to early detection of all patients.Sonography is also not suitable because of its low sensitivity to small lesions and dependent on the experience of operator.CT,MRI and CDI are also not suitable owing to many shortcomings.Thanks to its freedom from radiation,invasion and high cost,breast Electrical Impedance Imaging(EIS) has opened up a brand-new horizon in the early detection and assistant diagnosis of the breast cancer.Previous researches had proved that there is significant difference in impedance characteristics between the breast cancer and the normal tissues.The feasibility of the application of EIS to breast cancer diagnosis is also confirmed by clinical observation tests.There yet have been many problems in the study of EIS.(1) criteria:The basic studies pointed out that resistivity of the breast cancer is 3～6 times lower than that of either the normal tissue or the benign lesion.So,the breast cancer appears as bright spots with high conductivity on EIS.But we found that some breast cancer appeared as ether bright or dark spots on the EIS equipment developed by ourselves,which phenomenon had been seldom reported abroad and needed further observation.(2) The ability of EIS test to early diagnosis of breast cancer needed more adequate clinical data to support.(3) Based on the differences in components and incidence of breast disease of different races,the characteristic of EIS must be different which has not ever been reported abroad. (4) With present level of diagnosis,EIS test can not replace mammography which has been used as a standard means of early detection of breast cancer.To find a better application area is very important.In order to explore the impedance characteristics of Chinese women and resolve those problems,we build a system for impedance spectroscopy measurement in vitro,with which a relative systemic study is indispensable on the impedance characteristics of the breast tissue of Chinese women using our own EIS equipment- Angelplan-EIS 1000.On the other hand,we embarked on EIS of a large number of clinical cases and made the control test with ultrasound and mammography.The present paper covers the following aspects.1.Construction of the breast impedance spectroscopy measurement systemWe constructed an impedance spectroscopy measurement system based on the frequency response analyzer,which provides current injection with different frequencies ranging from 10μHz to 1MHz and voltage measurement circuit with an accurate and stable output signal.The system also consisted of rectangular drawing,which can make the size of tissues fixed and four-terminal silvern configuration.To ensure the consistency of experiment condition,the temperature and humidity were also controlled.2.Measurement of the impedance spectroscopy of pathological breast tissuesBased on our impedance spectroscopy system and technique,the impedance spectroscopy of diseased breast tissues were measured including invasive ductal carcinoma,invasive lobular carcinoma,mastopathy,fibroadenoma,mastoid neoplasm and cysts hyperplasia.The results showed that the impedance of breast carcinoma was higher than that of the benign tissue while there was no difference in impedance between the two carcinomas and between the four benign diseases.3.Impedance spectroscopy measurements of breast carcinoma and its surrounding normal tissues of breast organ with contrast of image produced by EIS in vivo.In this study,we measured the impedance spectroscopy of breast cancer and its surrounding normal tissues,which were obtained from mastectomy surgeries with infiltrating duct carcinoma to find the differences between them.The results were contrasted with the images of EIS test.The results showed there was significant difference in impedance characteristic between the breast carcinoma and its surrounding tissue.This study has indicated that there is an experimental base for Chinese women's breast survey by means of EIS.The other finding was that with different kind of surrounding tissues,the impedance characteristics were different.If the ingredient is mainly of fatty tissue,the impedance of carcinoma was lower than that of the peripheral tissue and the breast cancer appears as bright spots on EIS image.If the ingredient is mainly of normal gland tissue,the impedance of carcinoma was higher than that of the peripheral tissue and the breast cancer appears as dark spots on EIS image.These results can reasonably explain the reason why some breast cancers shows dark spots on EIS image in some patients and successfully solve the contradiction in abroad articles.4.Analysis of electrical impedance scanning of breasts in normal women.Using our own EIS equipment- Angelplan-EIS 1000,we tested normal breasts of 191 volunteers.The differences between different subjects were analyzed and the similarities between left and right breasts of the same subject were compared.The results demonstrated that the electrical impedance parameters were quite different between different subjects,but quite similar between the two breasts of the same subject.The characteristics of electrical impedance had no correlation with clinical parameters including age,stature and weight.5.Collection and analysis of EIS test data of patients on a large scale.In this study,a total of 3124 patients were entered into the study between Dec 2005 and Dec 2007.We collected results of EIS,pathological reports,ages, physical sighs,and other clinical information.The data were statically and methodology analyzed.The results demonstrated that:(1) Our self-developed electrical impedance instrument(Angelplan-EIS1000) had high sensitivity and specificity for diagnosis of breast cancer and its ability was not weaker than the foreign mature product TransScan-TS 2000.(2) EIS had some advantages which can't be replaced by other methods in diagnosis of early breast cancer.(3) The test of EIS rise superior to the size of breast and age.(4) For breast masses with different diameters,EIS has different diagnosis ability.The sensitivity and specificity were higher in groups with masses smaller than 20ram.(5) A higher sensitivity and specificity were observed in patients who received EIS test in delayed menstruation. 6.Contrast test of EIS and ultrasound,mammography.We designed two contrast clinical tests to compare the test ability of EIS and ultrasound,mammography.There were 163 and 207 patients enrolled into the two studies,respectively.The results indicated that there were no differences between the abilities of EIS and ultrasound in diagnosis of T1 breast cancer,but the two kinds of test had complementarity.Combinational detections were obviously able to increase sensitivity and PPV of breast cancer detection. Mammography was prior to EIS in detecting T1 breast cancer,but to patients whose age were younger than 40,the two tests had no differences.7.Prospective study on combinational detection of EIS and ultrasound in estimating risk for development of breast cancer in young women.A prospective,double blind clinical trial was done in young women aged 45 years and under.EIS and ultrasound results were compared with final histopathology results.Study end points included sensitivity and specificity of EIS,ultrasound and both combination,as well as relative probability of breast cancer of positive patients detected by combinational application of EIS and ultrasound.The results show that the combination of EIS and ultrasound could obviously increase sensitivity in detecting breast cancer of young women.The more important results was that the combination could increase the relative possibility of breast cancer of positive young women from 8.67,5.77 to 14.84. The combination of EIS and ultrasound is likely to become a main approach to screen early breast cancer for young women.
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