118 research outputs found

    Low Frequency Bio-Electrical Impedance Mammography and Dielectric Measurement

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    Assessment of electrical impedance of biological tissues at low frequencies offers a great potential for a safe, simple, and low-cost medical breast imaging techniques such as mammography. As such, in this dissertation a mammography method which uses tissue electrical impedance to detect breast malignancies was developed. The dissertation also introduces a new technique for measuring the dielectric properties of biological tissues at low frequencies. The impedance mammography technique introduced in this study is founded on the assumption that dielectric values of breast malignancies are significantly higher than the dielectric values of normal breast tissues. While previous studies have shown that this assumption is valid at high frequencies (50MHz-20GHz), less research efforts have been dedicated to ascertain the validity of such assumption at low frequencies (in silico and tissue mimicking phantom studies. Results of this investigation suggest that imaging the electrical impedance properties of biological tissues through the proposed electrical impedance mammography can be potentially employed for breast cancer detection in a reliable and safe manner

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

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    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

    DICOM for EIT

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    With EIT starting to be used in routine clinical practice [1], it important that the clinically relevant information is portable between hospital data management systems. DICOM formats are widely used clinically and cover many imaging modalities, though not specifically EIT. We describe how existing DICOM specifications, can be repurposed as an interim solution, and basis from which a consensus EIT DICOM ‘Supplement’ (an extension to the standard) can be writte

    Estimation of thorax shape for forward modelling in lungs EIT

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    The thorax models for pre-term babies are developed based on the CT scans from new-borns and their effect on image reconstruction is evaluated in comparison with other available models

    Rapid generation of subject-specific thorax forward models

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    For real-time monitoring of lung function using accurate patient geometry, shape information needs to be acquired and a forward model generated rapidly. This paper shows that warping a cylindrical model to an acquired shape results in meshes of acceptable mesh quality, in terms of stretch and aspect ratio

    Torso shape detection to improve lung monitoring

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    Two methodologies are proposed to detect the patient-specific boundary of the chest, aiming to produce a more accurate forward model for EIT analysis. Thus, a passive resistive and an inertial prototypes were prepared to characterize and reconstruct the shape of multiple phantoms. Preliminary results show how the passive device generates a minimum scatter between the reconstructed image and the actual shap

    Nanoparticle electrical impedance tomography

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    We have developed a new approach to imaging with electrical impedance tomography (EIT) using gold nanoparticles (AuNPs) to enhance impedance changes at targeted tissue sites. This is achieved using radio frequency (RF) to heat nanoparticles while applying EIT imaging. The initial results using 5-nm citrate coated AuNPs show that heating can enhance the impedance in a solution containing AuNPs due to the application of an RF field at 2.60 GHz

    Tecniche Elettrotomografiche per la caratterizzazione dei tessuti biologici

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    Electrical impedance tomography (EIT) is an imaging modality wherein the spatial map of conductivity and permittivity inside a medium is obtained from a set of surface electrical measurements. Electrodes are brought into contact with the surface of the object being imaged and a set of currents are applied and the corresponding voltages are measured. These voltages and currents are then used to estimate the electrical properties of the object using an image reconstruction algorithm which relies on an accurate model of the electrical interaction. The process of property estimation, called inverse problem, is highly ill-posed and it requires a Regularization method. The objective of this Thesis was to develop a device for imaging using the EIT technique, which was convenient, noninvasive, easily programmable, portable and relatively cheap in contrast to many other diagnostic tool. In this direction a simple EIT system and its hardware and software parts are developed. The data processing was accomplished by utilizing the EIDORS toolkit, which was developed for application to this nonlinear and ill-posed inverse problem. Experiments have indicated that the EIT system can reconstruct resistive and capacitive images of good contrast despite errors in the measurement are not taken in account

    Detection, numerical simulation and approximate inversion of optoacoustic signals generated in multi-layered PVA hydrogel based tissue phantoms

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    In this article we characterize optoacoustic signals generated from layered tissue phantoms via short laser pulses by experimental and numerical means. In particular, we consider the case where scattering is effectively negligible and the absorbed energy density follows Beer-Lambert's law, i.e. is characterized by an exponential decay within the layers and discontinuities at interfaces. We complement experiments on samples with multiple layers, where the material properties are known a priori, with numerical calculations for a pointlike detector, tailored to suit our experimental setup. Experimentally, we characterize the acoustic signal observed by a piezoelectric detector in the acoustic far-field in backward mode and we discuss the implication of acoustic diffraction on our measurements. We further attempt an inversion of an OA signal in the far-field approximation.Comment: 10 pages, 6 figures, supplementary code at https://github.com/omelchert/SONOS.gi

    Experimental Evaluation of a Microwave Tomography System for Breast Cancer Detection

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    Microwave tomography is a potential candidate for future breast-cancer screening or diagnosis. Contrary to x-rays, microwaves are non-ionizing and therefore not a health risk by their own. The examination procedure would also be more comfortable for the patient compared to conventional mammography since no compression of the breast is needed.The examination is performed by irradiating the breast with microwaves from multiple directions. The collected data is then processed by an iterative algorithm that reconstructs the permittivity and conductivity distribution in the interrogated region. Ideally, tumors could be identified in these reconstructed images due to their different properties compared to normal tissue.In this thesis, a prototype system for microwave tomographic imaging is experimentally evaluated. The system consists of 16 monopole antennas and utilize a mixture of water and glycerin as coupling liquid. As a tool for the assessment, two phantoms have been studied. One is a simplistic phantom consisting of a cylinder in which smaller cylindrical inclusions can be inserted. The other is a 3D printed structure made to resemble a human breast geometrically. This particular phantom consists of two shells, representing the different tissues of the breast. The system is found to produce well reconstructed images of both the interrogated phantoms. However, the interior geometry of the 3D printed phantom was more challenging.Furthermore, two different reconstruction algorithms are tested. The first is a Gauss-Newton based FEM algorithm and the second is a gradient-descent based FDTD method. Both of the studied algorithms proved to yield good reconstructions
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