The electrical properties of biological tissue as of colloidal dispersion in an alternating electric field depend on the concentration and behaviour of the chemical components of the tissue. The electrical properties of tumour tissue differ significantly from those of the surrounding tissues. Therefore, electrical conductivity is a suitable parameter for making the distinction between healthy and tumour tissues.
Electrical impedance mammography is a method of primary breast cancer screening. It is highly informative, safe for the personnel and the patient, it’s portable and mobile.
Screening tasks are to detect breast cancer, including early detection (when tumour size is below 1 cm), and to form survey or risk groups.
In order to solve these tasks, the following should be undertaken:
a. search for areas with abnormal electrical conductivity
b. detection of distortions in normal mammographic scheme
c. evaluation of age-related electrical conductivity
Formation of survey group
Application of a scale for age-related electrical conductivity of breast tissue with defined percentile limits allows to organize a survey group, which should include patients with abnormally low values of age-related electrical conductivity of breast tissue. They signify that in the breast structure the glandular-ductal component is prevalent among the patients of this age group. High mammographic density may be linked to a fourfold increase of the risk of breast cancer occurrence.Early diagnostics of breast cancer
Electrical properties of a cancerous tumour differ significantly from those of the surrounding tissues. It is an established fact that the electrical activity of cancer cells increases.
The results of these studies are given in the table
(The Use of Tissue Electrical Characteristics for Breast Cancer Detection: A Perspective Review. E. Y. K. Ng, Ph.D., S. Vinitha Sree, MSc., K. H. Ng, Ph.D., G. Kaw, MBBS, M.D. Technology in Cancer Research and Treatment ISSN 1533-0346 Volume 7, Number 4, August 2008).
The study results confirm that electrical conductivity is a valid parameter for making the distinction between healthy and tumorous tissues.
Primary activity during mammography screening is the search for the areas with anomalous electric conductivity; it is an important criterion for the early diagnostics of breast cancer.
Authors, Year |
Studied frequency range |
Nature of study and results |
Fricke et al. (29), 1926 |
20 kHz |
Measurements of parallel capacitance and resistance of the following excised samples from the breast: adipose, glandular tissue, mastitis, fibroadenoma and carcinoma. Discovery of significantly higher permittivity of the tumour tissue at 20 kHz as compared to healthy or benign tissues. |
Singh et al. (30), 1979 |
100 Hz -100 kHz |
In vivo impedance measurements on female mammary glands with and without tumours. Results demonstrating that malignant tumours have higher relative permittivity and lower resistance compared to healthy breast tissue. |
Chaudhary et al. (31), 1984 |
3 MHz - 3 GHz |
Examination of excised healthy and malignant breast tissues, discovery showing that conductivity and permittivity of malignant tissues are higher than those of healthy tissues, especially at frequencies lesser than 100 MHz. |
Surowiec et al. (32), 1988 |
20 kHz -100 MHz |
In vitro dielectric studies at three different samples of breast tissues: main tumour tissue, tissue immediately surrounding the tumour, and peripheral healthy tissue. It was discovered that the tumour tissues demonstrate low frequency (100 kHz) conductivity around 2 to 4 S·m/cm, which is higher than the conductivity of healthy tissue (below 1 S·m/cm) and lower than that of the tissue surrounding the tumour (8 S·m/cm). |
Morimoto et al. (33, 34), 1990 |
0 - 200 kHz |
Measurements of extracellular and intracellular resistance and membrane capacitance of breast tumours in vivo. Conclusion that there are statistically significant differences between healthy and cancerous tissues. However, it has been reported that malignant tumours have lowered capacitance compared to benign tumours. This is different from the results of the study conducted by Jossinet (36) and Fricke (33), who have recorded higher capacitance values for malignant tumours. |
Jossinet (35), 1996 |
488 Hz - 1 MHz |
Study of six groups of healthy and pathological breast tissues in vitro. Within each group, variability of impedivity was assessed by statistical methods. It was found that the variability was smaller in adipose tissue, carcinoma and fibroadenoma at frequencies above 10 kHz. |
Jossinet (36), 1998 |
488 Hz - 1 MHz |
Using the same data from (35), it was found that the cancerous tissue differed significantly from fibroadenoma and mammary gland tissues by the modulus of impedivity up to 31.25 kHz and from the remaining tissue groups (connective tissue, adipose tissue, and mastopathy) by the low-frequency-limit resistivity and the phase angle from 125 kHz to 1 MHz. It was also observed that neither the impedivity, nor the low-frequency-limit resistivity nor the fractional power value was different between the groups of healthy and benign tissues. |
Jossinet et al. (37), 1999 |
488 Hz - 1 MHz |
Again using the same excised data collected for previous studies, a set of eight parameters that could differentiate cancerous breast tissues from non-cancerous ones was defined. Conclusion that a combination of the parameters over various frequencies is necessary for the accurate differentiation among tissues. |
Chauveau et al. (38), 1999 |
10 kHz - 10 MHz |
In vitro study of healthy and pathological breast tissues, observation of significant differences in their dielectric properties. Determination of three indices based on extracellular resistance, intracellular resistance and membrane capacitance to differentiate between various tissue pathologies: healthy tissue, Invasive Ductal Carcinoma (IDC), IDC with stromal reaction and fibrocystic changes. |
Results of studies confirm that electrical conductivity is a suitable parameter for making the distinction between healthy and tumour tissues. Primary activity during mammography screening is the search for the areas with anomalous electric conductivity, which is an important criterion for the early diagnostics of breast cancer.
Distorted mammographic scheme in cases of breast cancer
Along with focal changes, one of possible manifestations of breast cancer is the diffuse changes in the structure of mammary gland that lead to the distortion of the normal mammographic scheme. The disease development resulting from the destruction of epithelial basement membrane is linked with various phenomena occurring in the tumour and the surrounding tissues: they lead to changes in the electrical properties of the tumour, i.e. oedema and sponginess of fibrous connective tissues, sliming, hyaline degeneration, calcification, formation of areas with suppurative inflammation, lymphocytic infiltration of tissue. Consequently, tumour growth is accompanied with changes of electrical properties of the tumour and its surrounding tissues.
Classification of breast structure
The distinctive feature of electrical impedance method of breast structure evaluation is the numerical expression of its anatomical and histological structure. It is a well-known fact that density of breast is determined by breast structure. Breast density is an important factor that has an effect over malignant changes in breast. Electrical conductivity index allows to evaluate breast density. ‘Dense’ breast, i.e. the so-called ductal type, is characterized by low electrical conductivity index. High electrical conductivity index is common for amorphous type of mammary gland, which consists mostly of adipose and connective tissue.
Introduction of a new technology is rarely painless due to complicated discussions. During the last few years, in different countries clinical trials were held aimed to determine the capacities of electrical impedance mammography in the diagnostics of breast cancer.
Sachin Prasad and colleagues performed a study in 2008 to determine the diagnostic efficiency of 3D electrical impedance tomography (EIT) compared to mammography (mg) and ultrasonography (USG) in breast imaging. A group of 88 patients with various breast complaints was examined using combined mammography and ultrasonography (MG & USG) or either of these modalities alone. The same patients were then examined using the 3D EIT imaging system MEIK. The study revealed that there was no overall significant difference in sensitivity between MG-USG (p = 0.219) and MG-EIT (p = 0.779) and USG-EIT (p = 0.169).
O. Raneta and colleagues performed a study in 2012 to analyze the possibilities of electrical impedance tomography (EIT) application in the differential diagnosis of pathological lesions of the breast either solely, or in a combination with MMG/USG. A group of 870 eligible women was examined with suspected pathological breast lesion discovered by mammography (MMG) or ultrasound examination (USG) who were recommended to pass histological examination to verify the diagnosis. The sensitivity of MMG increased from 87.8% when using it as an independent method to 94.5% with EIT added. The sensitivity of USG increased from 86.7% when used as an independent method to 93.3% with EIT added. The results of the study showed that the use of EIT in addition to MMG/USG can improve the sensitivity of these methods and increase the rate of early detection of breast cancer with minimal economic costs and time input of highly qualified staff.
Daglar G. and colleagues performed a study in 2016 to compare the usefulness of the breast electrical conductivity measures performed in a surgical examination room against conventional breast screening modalities for identifying the symptomatic lesions of the breast tissue. A group of 181 patients were examined with ultrasonography (USG), mammography (MG), electrical impedance scanning (EIS) modalities and were followed-up for 24 months to clarify the lesion tumour progression relationship. EIS exhibited compatible sensitivity (81.2 %), accuracy (84.6 %) and PPV (81.8 %) rates with USG in BI-RADS 4 subgroup, combination of these modalities raised sensitivity rates to 92.31 %, accuracy and PPV to 100 %. EIS results in BI-RADS 3 subgroup were pointed out 77.8 % specificity and 87.5 % NPV rates. Breast electrical impedance measures should be useful to reduce the number of the unnecessary follow-up and biopsy rates in the clinical setting.
Xu Feng and colleagues performed a study in 2017 to investigate the diagnostic accuracy of electrical impedance tomography (EIT) for benign and malignant breast diseases in comparison to conventional ultrasonography and mammography. A total of 121 patients with 126 breast lesions who underwent ultrasonography mammography and EIT were enrolled in the study. All of these lesions were confirmed by pathological biopsy. The accuracy, sensitivity, specificity, positive predictive value and negative predictive value of EIT, ultrasonography and mammography were calculated with histology used as the ‘gold’ standard. The accuracy of EIT, ultrasonography and mammography were 75.4%, 81.7% and 76.1% respectively. The sensitivity was 76.8%, 94.6% and 74.4% respectively. The specificity was 74.3%, 71.4% and 77.6% respectively. The accuracy, sensitivity and specificity of EIT combined with ultrasound in the diagnosis of breast lesions were 91.3%, 98.2% and 85.7%, respectively. The accuracy (χ2=4.896, P=0.027) and specificity (χ2=4.242, P=0.039) were significantly higher on EIT compared to ultrasound. The accuracy, sensitivity and specificity of EIT combined with mammography were 95.5%, 97.4% and 93.9%, respectively, which were significantly higher than those of mammography (χ2=13.474, P<0.001; χ2=8.573, P=0.003; χ2=5.333, P=0.021). Used together with ultrasound or mammography, the electrical impedance tomography (EIT) could be a valuable complementary examination in the diagnosis of breast diseases. Furthermore, EIT could provide very useful additional information for metabolic assessment of mammary glands, which may be used for early screening of breast diseases.
Blanca Murillo-Ortiz and colleagues performed a study in 2019 to know the effectiveness of the electrical impedance mammography for the detection of mammary carcinoma in 615 women from 25 to 70 years of age. The sensitivity and specificity of the electrical impedance mammography (MEIK) was 85% and 97% respectively.
Operational characteristics of electrical impedance mammography (sensitivity and specificity) were defined in a survey conducted in large oncological centres with limited sampling, in the so-called ‘high prevalence group’, using a referential method (X-ray mammography) and confirmed diagnoses. The acquired operational characteristics may be spread on large groups of patients with low prevalence and be used for the planning of screening examinations