Electrical Impedance Mammography Research Articles

Machine Learning for the Analysis of Conductivity From Mono Frequency Electrical Impedance Mammography as a Breast Cancer Risk Factor

Computational approaches have been used for analyzing risk factors together with conventional mammograms for breast cancer detection. Currently, other screening methods like electro-impedance mammography are available. Notwithstanding, as far as we know there is not related work evaluating the role of electrical-conductivity index of the mammary gland as a quantitative factor for early detection of breast cancer. This paper aims to demonstrate the importance of including breast conductivity index as a quantitative local risk-factor by analyzing a dataset of Mexican patients from a machine learning perspective. There are 12 attributes distributed into two groups: electrical-conductivity (3) and medical records (9). According to the obtained results with unsupervised methods, the performance in terms of accuracy of using only electrical-conductivity (43%) is better than using all available features (38%) and the medical records (33%). On the other hand, we identified that SVM achieves higher results in comparison with other algorithms when only the electrical-features are used. The obtained results demonstrate the important role of conductivity index as a quantitative local risk-factor for being considered in screening processes. Besides, it emerges as an important aspect to be included in the development of automatic tools for experts to perform breast cancer diagnosis.

Monofrequency electrical impedance mammography (EIM) diagnostic system in breast cancer screening

BackgroundSome evidence has shown that malignant breast tumours have lower electrical impedance than surrounding normal tissues. Electrical impedance could be used as an indicator for breast cancer detection. The purpose of our study was to analyse the sensitivity and specificity of electrical impedance mammography (EIM) and its implementation for the differential diagnosis of pathological lesions of the breast, either alone or in combination with mammography/ultrasound, in 1200 women between 25 and 70 years old.MethodsThis study is a prospective, cross-sectional epidemiological observational study of serial screening. The women were invited to participate and signed a consent letter. Impedance imaging of the mammary gland was evaluated with the computerized mammography equipment of MEIK electroimpedance v.5.6. (0.5 mA, 50 kHz), developed and manufactured by PKF SIM-Technika®. The successful identification of breast cancer along with the sensitivity, specificity, and positive and negative predictive values of EIM were determined as follows: % sensitivity; % specificity; % positive predictive value (PPV); and % negative predictive value (NPV).ResultsEIM had a sensitivity of 85% and a specificity of 96%; the positive predictive value was 12%, and the negative predictive value was 99%. Seven cases were biopsy confirmed cancers. Significant correlations between the electrical conductivity index and body mass index (BMI) (p = 0.04) and patient age were observed (p = 0.01). We also observed that the average conductivity distribution increased according to age group (p = 0.001). We used the chi-squared test to assess the interactions between percent density and BMI (normal < 25 kg/m2 (n = 310), overweight 25–29.9 kg/m2 (n = 418) and obese ≥30 (n = 437)) (p < 0.05). The patients with a diagnosis of mammary carcinoma had a BMI of 35.51 kg/m2.ConclusionsOur results demonstrate that the use of monofrequency electrical impedance mammography (EIM) in the detection of breast cancer had a sensitivity and specificity of 85 and 96%, respectively. These findings may support future research in the early detection of breast cancer. EIM is a non-radiation method that may also be used as a screening method for young women with dense breasts and a high risk of developing breast cancer.

Modified weighted back-projection algorithm (MWBP) for 3D electrical impedance mammography systems with the planar electrode array

Electrical impedance mammography (EIM), as one of the EIT medical applications, is applied for diagnostics and imaging of the breast. Quality of reconstructed images in this method depends on precision of the EIM hardware and efficiency of the image reconstruction algorithm. One of the linearized methods in EIT image reconstruction is Weighted Back-Projection (WBP). The purpose of this paper is to present a novel method, which is a modified version of the current 3D WBP algorithm (MWBP), to improve the quality of reconstructed images in electrical impedance mammography. In order to calibrate the 3D WBP algorithm with regards to real equipotential surfaces and output results, some attempts have been made to model the real EIM conditions in terms of body shape and electrode positions by means of a saline-filled phantom. We have proposed a few modifications which improve the quality of images greatly, in terms of sensitivity, resolution, contrast, and accuracy in size and position of objects under imaging. The mentioned modifications contain: changing the problem assumptions, adding a new weighting function to the current 3D WBP equation, and defining an exciting radius for the pixel being reconstructed. The final results (containing phantom and in vivo images) prove the efficiency of the proposed modifications.

Conditioning Electrical Impedance Mammography System

A multi-frequency Electrical Impedance Mammography (EIM) system has been developed to evaluate the conductivity and permittivity spectrums of breast tissues, which aims to improve early detection of breast cancer as a non-invasive, relatively low cost and label-free screening (or pre-screening) method. Multi-frequency EIM systems typically employ current excitations and measure differential potentials from the subject under test. Both the output impedance and system performance (SNR and accuracy) depend on the total output resistance, stray and output capacitances, capacitance at the electrode level, crosstalk at the chip and PCB levels. This makes the system design highly complex due to the impact of the unwanted capacitive effects, which substantially reduce the output impedance of stable current sources and bandwidth of the data that can be acquired. To overcome these difficulties, we present new methods to design a high performance, wide bandwidth EIM system using novel second generation current conveyor operational amplifiers based on a gyrator (OCCII-GIC) combination with different current excitation systems to cancel unwanted capacitive effects from the whole system. We reconstructed tomography images using a planar E-phantom consisting of an RSC circuit model with different set of values, which represents the resistance of extra-cellular (R), intra-cellular (S) and membrane capacitance (C) of the breast tissues to validate the performance of the system. The experimental results demonstrated that an EIM system with the new design achieved a high output impedance of 10 MΩ at 1 MHz to at least 3 MΩ at 3 MHz frequency, with an average SNR and modelling accuracy of over 80 dB and 99%, respectively.

A feasibility study of a rotary planar electrode array for electrical impedance mammography using a digital breast phantom

A feasibility study of an electrical impedance mammography (EIM) system with a rotary planar electrode array, named RPEIM, is presented. The RPEIM system is an evolution of the Sussex MK4 system, which is a prototype instrument for breast cancer detection. Comparing it with the other planar electrode EIM systems, the rotation feature enables a dramatic increase in the number of independent measurements. To assist impedance evaluation exploiting electrode array rotation, a synchronous mesh method is proposed. Using the synchronous mesh method, the RPEIM system is shown to have superior performance in image accuracy, spatial resolution and noise tolerance over the MK4 system. To validate the study, we report simulations based on a close-to-realistic 3D digital breast phantom, which comprises of: skin, nipple, ducts, acinus, fat and tumor. A digital breast phantom of a real patient is constructed, whose tumor was detected using the MK4 system. The reconstructed conductivity image of the breast phantom indicates that the breast phantom is a close replica of the patient’s real breast as assessed by the MK4 system in a clinical trial. A comparison between the RPEIM system and the MK4 system is made based on this phantom to assess the advantages of the RPEIM system.

Effective electrode sampling strategies for 3D electrical impedance mammography

A novel three-dimensional (3D) electrical impedance mammography (EIM) system, named the combined EIM (CEIM) system, is introduced. It combines a ring electrode array with a planar electrode array that can operate independently or together. Three operational modes of the CEIM system are presented. Using a close-to-realistic digital breast phantom, the CEIM system is shown to provide enhanced detectability of a tumour deep within the tissue, as required for a large-volume breast. An implicit comparison with the authors' former MK4 system demonstrates the benefits of this integrated multimode mammography system.

Electrical impedance mammography. Electrical conductivity of the breast

Electrical impedance mammography. Electrical conductivity of the breast

Влияние монотерапии эстрогенами на состояние молочных желез у женщин климактерического периода

For the treatment of genitourinary disorders is an effective means of appointment of local forms of estriol. The article presents the results of assessing the impact of estriol on the breast using the method of electrical impedance mammography. The absence of negative impact and no change in the state of mammary glands using local forms of estriol.

Diagnostic Criteria for Mass Lesions Differentiating in Electrical Impedance Mammography

Currently, there emerged a necessity of a standardized description of volumetric lesions and developing of a system for volumetric lesions description in the mammary gland to be in line with ACR BI-RADS categories. The purpose of this research was to determine the diagnostic criteria for differentiating volumetric lesions in the mammary gland in electrical impedance mammography. The research was carried out utilizing the electrical impedance computer mammograph «MEIK v.5.6»®, which enables to acquire images of 3-D conductivity distribution layers within mamma’s tissues up to 5 cm depth. The weighted reciprocal projection method was employed to reconstruct the 3-D electric conductivity distribution of the examined organ. The results of 3,710 electrical impedance examinations were analyzed. The analysis of a mass lesion was conducted in BI-RADS ACR terms and included assessment of its shape, contour, internal electrical structure and changes of the surrounding tissues. Moreover, mammary gland status was evaluated with the help of comparative and age-related electrical conductivity curves. The diagnostic charts were built and will be discussed in this talk. Each criterion was measured in points. Using the numerical score for evaluation of volumetric and non-volumetric lesions within the mammary gland in electrical impedance mammography allowed comparing this information to BI-RADS ACR categories

An image reconstruction algorithm for 3-D electrical impedance mammography.

The Sussex MK4 electrical impedance mammography system is especially designed for 3-D breast screening. It aims to diagnose breast cancer at an early stage when it is most treatable. Planar electrodes are employed in this system. The challenge with planar electrodes is the inaccuracy and poor sensitivity in the vertical direction for 3-D imaging. An enhanced image reconstruction algorithm using a duo-mesh method is proposed to improve the vertical accuracy and sensitivity. The novel part of the enhanced image reconstruction algorithm is the correction term. To evaluate the new algorithm, an image processing based error analysis method is presented, which not only can precisely assess the error of the reconstructed image but also locate the center and outline the center and outline the shape of the objects of interest. Although the enhanced image reconstruction algorithm and the image processing based error analysis method are designed for the Sussex MK4 system, they are applicable to all electrical impedance tomography systems, regardless of the hardware design. To validate the enhanced algorithm, performance results from simulations, phantoms and patients are presented.

Diagnostic criteria for mass lesions differentiating in electrical impedance mammography

The purpose of this research was to determine the diagnostic criteria for differentiating volumetric lesions in the mammary gland in electrical impedance mammography. The research was carried out utilizing the electrical impedance computer mammograph ≪MEIK v.5.6≫®, which enables to acquire images of 3-D conductivity distribution layers within mamma's tissues up to 5 cm depth. The weighted reciprocal projection method was employed to reconstruct the 3-D electric conductivity distribution of the examined organ. The results of 3,710 electrical impedance examinations were analyzed. The analysis of a volumetric lesion included assessment of its shape, contour, internal electrical structure and changes of the surrounding tissues. Moreover, mammary gland status was evaluated with the help of comparative and age-related electrical conductivity curves. The diagnostic chart is provided. Each criterion is measured in points. Using the numerical score for evaluation of mass and non-volumetric lesions within the mammary gland in electrical impedance mammography allowed comparing this information to BI-RADS categories developed by American College of Radiology experts. The article is illustrated with electrical impedance mammograms and tables.

Diagnosis of Breast Cancer Using Electrical Impedance Tomography

The efficiency of electrical impedance tomography, a new method of breast cancer diagnosis, is considered in this work. A total of 117 female patients (apparently healthy, patients with mastopathy, patients with benign tumors, patients with breast cancer) were tested. The method was implemented using an electrical impedance computer mammograph with special 5.6 software version. Its efficiency was estimated to be 87.39%. Of 75 patients with breast cancer, 96% were found to have degree III of risk of disease progression; 4%, degree II of disease progression risk. Additional examination was recommended. Electrical impedance mammography was demonstrated to be a noninvasive, safe, comfortable, rapid, and informative method of diagnosis.

P2-10-08: Electrical Impedance Imaging Characteristics of Nodular and Edematous-Infiltrative Forms of Breast Cancer.

Abstract Introduction: The purpose of this research is to establish diagnostic criteria of electrical impedance mammography, which are typical for nodular and diffuse forms of breast cancer. Materials and Methods: From 2008 to 2011, we examined 558 patients, 34 of whom had various forms of breast cancer (BC). All the patients were examined with electrical impedance potential mammography utilizing the electrical impedance computer mammograph MEIK, which enables to acquire images of 3-D conductivity distribution layers within mamma's tissues up to 5 cm depth. Group I comprised 27 women suffering from nodular forms of BC. Among them 9 women without clinical signs of the disease were put into subgroup I&amp;a. 19 patients having significant clinical signs, such as edema, inflammation and infiltration, were put into subgroup Ib. Group II included 6 patients with diffuse BC. 102 patients without any mammary gland disease were put into the control group. Both visual and quantitative assessment of electrical impedance mammograms (EIM) was conducted. Result: Distinctions of kind were revealed between EIMs of the abovementioned patient groups. In case of nodular BC both general and local changes were observed in EIMs. General changes include deformation of mamma's contour, hyperimpedance contour and displacement of inner structures. Local changes comprise focal changes of electrical conductivity in form of an- or isoimpedance areas and hyperimpedance contour on the border of the tumor and surrounding tissue. In EIM mammograms of 100% patients belonging to subgroup Ia only local changes of electrical conductivity were detected in a form of animpedance area presented on several scan planes in the location corresponding to the tumor (electrical conductivity index &amp;gt;0.95), while there were no general changes in the image. The size of lesions detected in this group was less than 1 cm. Clinical signs of the decease were always present in group Ib patients. EIMs of these patients revealed both general and various local changes. Visual estimation of images revealed deformation of the mammary gland contour in 50% of the cases, subcutaneous fat infiltration - in 61%, anatomic changes with displacement of internal structures in 78%, perifocal infiltration in 94%. The quantitative analysis established the following: mean electrical conductivity index of a healthy mammary gland, as a rule, exceeded the index of mean electrical conductivity of the affected one; and the index of the mean electrical conductivity of a tumor exceeded the index of mean electrical conductivity of the affected gland almost twofold. EIMs of 100% of the patients with diffuse (edematous-infiltrative) BC revealed typical general changes of electrical conductivity: electrical conductivity of the affected mammary gland is considerably lower than that of the healthy one as well as lower than that of the age norm. This results in the intense dark EIM and significant change of electrical impedance anatomy. Conclusions: The revealed peculiarities of the electrical impedance images during various forms of the infiltrating BC growth correlate with the pathological-physiological phases of the tumor development. The article is illustrated with electrical impedance mammograms (EIMs) and tables. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-10-08.

Analysis of forward solvers for electrical impedance tomography in a mammography geometry

We explain how the problem of improving image reconstruction in electrical impedance mammography can be studied by comparing measured data with predictions from the continuum model, ave-gap model, and complete electrode model. The data is measured by the RPI ACT4 system using 60 electrodes arranged in a mammography geometry. Each model's accuracy can be determined by comparing the computed eigenvalues of its Neumann-to-Dirichlet map with those found from experimentally measured N-to-D maps. It will be explained how the different models can be used to reconstruct images of the electrical conductivity and permittivity inside a region bounded by a pair of electrode arrays in a mammography geometry. Reconstructions from experimental data are presented.

A flexible and configurable hardware for the combined EIM and Ultrasound device

One of the current methods in breast cancer detection is Sonography, also known as Ultrasound imaging. Sonography is effective for imaging soft tissues of the body and returns a high resolution image. Its operation is highly subjective depending on the operator and the images do vary with positioning. At the University of Sussex we have successfully built an automated and repeatable Ultrasound scanner and combined and reconstructed the data in 3D. Ultrasound imaging does have its limitations when it comes to cancer detection and diagnosis. The Sussex EIM (Electrical Impedance Mammography) device is a novel imaging system developed at the University of Sussex for the detection of breast lesions in-vivo using quadrature detection of impedance. Combining the high resolution images of Ultrasound with the parametric data of EIT would give a more precise diagnosis. This paper describes how we have achieved a totally configurable system where we have combined our current EIT technology for breast cancer detection to the 3D Ultrasound scanner we have built. This was done with a quick turn-around in development time using off-the-shelf hardware and a 3U PXI Chassis. The system is based around a National Instruments PXI (PCI eXtensions for Instrumentation) chassis which is a modular electronic instrumentation platform.

Signal calibration for an Electrical Impedance Mammography system

Electrical Impedance Tomography (EIT) technology has been applied clinically since the 1980s. Numerous papers have addressed a variety of systematic error sources and indicated different calibration methods. The Sussex Mk4 Electrical Impedance Mammography (EIM) system has been developed for the investigation of early stage breast lesions. Investigations have shown that the system performance is subjected to a number of systematic errors: frequencies-dependant noise level due to both internal and external sources; stray capacitance within both PCB tracks and cable connections; and artefacts generated by patient movement during scanning etc. This paper reports upon several traditional and novel calibration methods utilized to reduce some of these errors in the acquired signals before image reconstruction. Techniques used include frequency spectrum analysis, filtering, phase calibration and other means of noise reduction. Results of both before and after calibration are presented and analyzed. The conclusion is reached that the signal quality of the Sussex Mk4 EIM system is such that the system is, post-calibrated, capable of producing images for the diagnosis of breast cancer.

Further investigation of a contactless patient-electrode interface of an Electrical Impedance Mammography system

The Sussex Mk4 Electrical Impedance Mammography (EIM) system is a novel instrument, designed for the detection of early breast cancer, based upon Electrical Impedance Tomography (EIT). Many innovations in the field have been incorporated in the design improving both signal distribution and response. This paper investigates the behaviour of the contactless patient-electrode interface. The interface was studied in detail using phantom and healthy volunteer, in-vivo, data. Our findings show the necessity for the careful design of electrode enclosure so that the response of the system is not affected by the unpredictable positioning of the breast; it closely mimics those conditions seen when using the phantom. The paper includes a number of possible designs and their individual characteristics. In addition an explanation on the unanticipated effects and solutions for such are described.

The flexible and configurable Sussex EIM MK4 using PCI eXtensions for Instrumentation (PXI)

The Sussex Electrical Impedance Mammography (EIM device is a novel imaging system developed at the University of Sussex for the detection of breast lesions in-vivo using quadrature detection of impedance. The device uses a fully programmable planar array of electrodes. The control method employed is such that any two electrodes apply current to the breast whilst any other two, similarly non-invasive, electrodes detect the developed potential difference under the direction of proprietary software. The currents injected are provided by a signal source with available output frequencies that are continuous over a wide bandwidth. The system is a prototype device for research and clinical evaluation, therefore maximum flexibility is required for hardware and software settings. This paper describes how we have achieved a totally configurable system with a quick turn-around in development time using off-the-shelf hardware and a 3U PXI Chassis. The system is based around a National Instruments PXI (PCI eXtensions for Instrumentation) chassis which is a modular electronic instrumentation platform. The modules are register-based products, which use software drivers hosted on a PC to configure them as useful instruments, taking advantage of the increasing power of PCs to improve hardware access and simplify embedded software in the modules.

Dual-frequency electrical impedance mammography for the diagnosis of non-malignant breast disease

Electrical impedance tomography (EIT) enables one to determine and visualize non-invasively the spatial distribution of the electrical properties of the tissues inside the body, thus providing valuable diagnostic information. The electrical impedance mammography (EIM) system is a specialized EIT system for diagnostics and imaging of the breast. While breast cancer is the main target for any investigation conducted in this area, the diagnosis of non-cancerous diseases is also very important because it opens the way to improve the quality of life for many women and it may also reduce the incidence of breast cancer through effective treatment of mastopathy. This paper presents the main results of a comprehensive examination of 166 women using four methods: multifrequency electrical impedance mammography, ultrasonic investigation, x-ray mammography and puncture biopsy. The objective of the investigation is to estimate the usefulness of multifrequency electrical impedance mammography for diagnosing dyshormonal mammary gland diseases. The results demonstrate the advantages of the multifrequency EIM method. In particular, dual-frequency electrical impedance mammography in contrast with the single-frequency variant enables one not only to diagnose mastopathy, but also allows accurate detection of its cystless form based on observation of the absence of any difference between average conductivity in both phases of the menstrual cycle. Because the cystless form of mastopathy is associated with a higher risk of cancer development, this method allows identification of a higher risk group of patients for more frequent investigations.

0-100. Preliminary in vitro studies of electrical impedance mammography (EIM): a future technique for non-invasive breast tissue imaging?

0-100. Preliminary in vitro studies of electrical impedance mammography (EIM): a future technique for non-invasive breast tissue imaging?