An investigation of planar array system artefacts generated within an electrical impedance mammography system developed for breast cancer detection

An Electrical Impedance Mammography (EIM) planar array imaging system is being developed at the University of Sussex for the detection of breast cancers. Investigations have shown that during data collection, systematic errors and patient artefacts are frequently introduced during signal acquisition from different electrodes pairs. This is caused, in particular, by the large variations in the electrode-skin contact interface conditions occurring between separate electrode positions both with the same and different patients. As a result, the EIM image quality is seriously affected by these errors. Hence, this research aims to experimentally identify, analyse and propose effective methods to reduce the systematic errors at the electrode-skin interface. Experimental studies and subsequent analysis is presented to determine what ratio of electrode blockage seriously affects the acquired raw data which may in turn compromise the reconstruction. This leads to techniques for the fast and accurate detection of any such occurrences. These methodologies can be applied to any planar array based EIM system

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. © 2010 IOP Publishing Ltd

EPIC: Examining Patch Impedance Characteristics

In the United States, approximately one in 4 adults have at least one chronic illness, making up approximately 84% of US Healthcare Spending. Unfortunately, 50% of patients with chronic diseases do not take their medication properly and as such spend more money trying to get better – approximately $100 billion in annual preventable costs. One solution to this issue is digital medicine as it allows for the monitoring of patient medicine consumption. Our industry partner has developed a three-part digital medicine system with the aim of allowing patients with chronic health issues to better reach their health goals through monitoring of medication consumption. About one-third of clinical trials exhibit erroneous data, showing intermittent malfunction of the patch in the system. The focus of this senior design project is decoding these erroneous readings due to the patch and proposing possible solutions. This senior design project took the form of a design of diagnostic experiments, culminating in a mathematical model that synthesized all of the phenomena we uncovered through experimentation

A Partially Reflecting Random Walk on Spheres Algorithm for Electrical Impedance Tomography

In this work, we develop a probabilistic estimator for the voltage-to-current map arising in electrical impedance tomography. This novel so-called partially reflecting random walk on spheres estimator enables Monte Carlo methods to compute the voltage-to-current map in an embarrassingly parallel manner, which is an important issue with regard to the corresponding inverse problem. Our method uses the well-known random walk on spheres algorithm inside subdomains where the diffusion coefficient is constant and employs replacement techniques motivated by finite difference discretization to deal with both mixed boundary conditions and interface transmission conditions. We analyze the global bias and the variance of the new estimator both theoretically and experimentally. In a second step, the variance is considerably reduced via a novel control variate conditional sampling technique

Investigation of undesired errors relating to the planar array system of electrical impedance mammography for breast cancer detection

Breast cancer in women continues to be one of the leading causes of death in the world. Since the exact causes are not completely known, the most important approach is to reduce this mortality by early detection and treatment. Although the current detection techniques for breast cancer such as X-ray mammography provide useful informationfor diagnosis; development of a new imaging technique using non-ionising radiation is highly desirable in order to detect breast cancer at an early stage and overcome current limitations, such as age-dependent sensitivity. Electrical Impedance Mammography (EIM) provides a new solution to break through the current limitation for early cancer detection. The focus of this thesis is to investigate the current fourth generation Sussex EIM system. This system implements the EIM technique by examination of the tissueresponse to a multi-frequency injected current. The Sussex Mk4 system is discussed indetail followed by system hardware modelling. The hardware modelling includes both analogue and digital components. The analogue part includes modelling of the voltage to current converter (V-I) and analogue multiplexer while the digital section consists of modelling the signal generation, measurement and demodulating components. In the analogue section, bandwidth limitation due to the current source and the analogue multiplexer’s configuration is also the prime focus of investigation along with the proposal to overcome it. Possible factors affecting the system performance and signal quality are also part of the research. In this section, possible factors are characterized and discussed in detail on the basis of external and internal sources of possible errors along with predictable and unpredictable noise sources. External sources of error artefacts introduced by the patients and their movements while scanning are most likely to affect the image reconstruction. Predictable and unpredictable causes may introduce frequency dependent noise whereas internal sources, which can be also be classified as systematic errors, degrade system performance due to electronic circuit design, configuration, stray capacitance and cable connections. Further, comprehensive investigation is performed on the in-vivoun desired voltage threshold levels which come hand-in-hand with the methods to mitigate the possible factors responsible for them. A comprehensive study and analysis is also carried out to determine what ratio of electrode blockage can affect the acquired raw data and how this may compromise reconstruction. Techniques for fast detection of any such occurrences are also discussed

Clinical performance of a novel textile interface for neonatal chest electrical impedance tomography

Objective: Critically ill neonates and infants might particularly benefit from continuous chest electrical impedance tomography (EIT) monitoring at the bedside. In this study a textile 32-electrode interface for neonatal EIT examination has been developed and tested to validate its clinical performance. The objectives were to assess ease of use in a clinical setting, stability of contact impedance at the electrode–skin interface and possible adverse effects. Approach: Thirty preterm infants (gestational age: 30.3 ± 3.9 week (mean ± SD), postnatal age: 13.8 ± 28.2 d, body weight at inclusion: 1727 ± 869 g) were included in this multicentre study. The electrode–skin contact impedances were measured continuously for up to 3 d and analysed during the initial 20-min phase after fastening the belt and during a 10 h measurement interval without any clinical interventions. The skin condition was assessed by attending clinicians. Main results: Our findings imply that the textile electrode interface is suitable for long-term neonatal chest EIT imaging. It does not cause any distress for the preterm infants or discomfort. Stable contact impedance of about 300 Ohm was observed immediately after fastening the electrode belt and during the subsequent 20 min period. A slight increase in contact impedance was observed over time. Tidal variation of contact impedance was less than 5 Ohm. Significance: The availability of a textile 32-electrode belt for neonatal EIT imaging with simple, fast, accurate and reproducible placement on the chest strengthens the potential of EIT to be used for regional lung monitoring in critically ill neonates and infants