241 research outputs found

    A Patient-Specific Approach for Breast Cancer Detection and Tumor Localization Using Infrared Imaging

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    Breast cancer (BC) is the most common cancer among women in the United States; approximately one out of every 24 women die of related causes. BC screening is a critical factor for improving patient prognosis and survival rate. Infrared (IR) thermography is an accurate, inexpensive and operator independent modality that is not affected by tissue density as it captures surface temperature variations induced by the presence of tumors. A novel patient-specific approach for IR imaging and simulation is proposed. In this work, multi-view IR images of isolated breasts are obtained in the prone position (face down), which allows access to the entire breast surface because the breasts hang freely. The challenge of accurately determining size and location of tumors within the breasts is addressed through numerical simulations of a patient-specific digital breast model. The digital breast models for individual patients are created from clinical images of the breast, such as IR imaging, digital photographs or magnetic resonance images. The numerical simulations of the digital breast model are conducted using ANSYS Fluent, where computed temperature images are generated in the same corresponding views as clinical IRI images. The computed and clinical IRI images are aligned and compared to measure their match. The determination of tumor size and location was conducted through the Levenberg-Marquardt algorithm, which iteratively minimized the mean squared error. The methodology was tested on the breasts of seven patients with biopsy-proven breast cancer with tumor diameters ranging from 8 mm to 27 mm. The method successfully predicted the equivalent tumor diameter within 2 mm and the location was predicted within 6.3 mm in all cases. The time required for the estimation is 48 minutes using a 10-core, 3.41 GHz workstation. The method presented is accurate, fast and has potential to be used as an adjunct modality to mammography in BC screening, especially for dense breasts

    Development of a Clinical Head and Neck Hyperthermia Applicator

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    Treatment of advanced tumours in the head and neck (H&N) remains complex and the toxicity related to the currently standard treatment modalities is a major issue. For many tumour sites, the addition of hyperthermia (HT) to radiotherapy has been shown to result in improved local control rates and/or better overall survival rates. HT has a high potential to improve cancer treatment results in H&N patients as well without adding toxicity. However, an appropriate applicator that can heat both superficially and deeply located target sites in the H&N region is currently not available. This thesis describes the items that needed to be addressed to design and build such an applicator. Extensive theoretical parameters studies were performed 1) to show the feasibility of deep heating in the H&N using radiofrequency (RF) waves and 2) to guide the design of the applicator. These parameter studies were performed using electromagnetic (EM) simulation programs. The predictions were then verified by measurements and with their results we designed and build a clinical prototype (the HYPERcollar applicator). We performed treatment planning for several patients to establish the specific absorption rate (SAR) patterns that are achievable with this applicator. In a heating session of the first patient of an ongoing clinical feasibility study we showed the possibility of deep heating using the HYPERcollar applicator

    Heating technology for malignant tumors: a review

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    The therapeutic application of heat is very effective in cancer treatment. Both hyperthermia, i.e., heating to 39-45 degrees C to induce sensitization to radiotherapy and chemotherapy, and thermal ablation, where temperatures beyond 50 degrees C destroy tumor cells directly are frequently applied in the clinic. Achievement of an effective treatment requires high quality heating equipment, precise thermal dosimetry, and adequate quality assurance. Several types of devices, antennas and heating or power delivery systems have been proposed and developed in recent decades. These vary considerably in technique, heating depth, ability to focus, and in the size of the heating focus. Clinically used heating techniques involve electromagnetic and ultrasonic heating, hyperthermic perfusion and conductive heating. Depending on clinical objectives and available technology, thermal therapies can be subdivided into three broad categories: local, locoregional, or whole body heating. Clinically used local heating techniques include interstitial hyperthermia and ablation, high intensity focused ultrasound (HIFU), scanned focused ultrasound (SFUS), electroporation, nanoparticle heating, intraluminal heating and superficial heating. Locoregional heating techniques include phased array systems, capacitive systems and isolated perfusion. Whole body techniques focus on prevention of heat loss supplemented with energy deposition in the body, e.g., by infrared radiation. This review presents an overview of clinical hyperthermia and ablation devices used for local, locoregional, and whole body therapy. Proven and experimental clinical applications of thermal ablation and hyperthermia are listed. Methods for temperature measurement and the role of treatment planning to control treatments are discussed briefly, as well as future perspectives for heating technology for the treatment of tumors

    Investigations of the thermal properties of human and animal tissues

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    The work presented in this thesis was carried as part of a project to improve the analysis of clinical data obtained by microwave thermography. For microwave thermography measurements to be usefully interpreted for detecting thermal anomalies in the human body at depths of up to several centimetres, the thermal and microwave dielectric properties of tissues must be known. This thesis is mainly concerned with the measurement and interpretation of the values of the thermal conductivity and diffusivity of human and animal tissues. The thermal properties of biological tissue are required, in conjunction with a bio-heat equation, to allow the formation of computational models to simulate the temperature distribution inside the human body. These computational models are also useful in the analysis of tomographic temperature measurements, and are essential to ensure accurate heating in hyperthermia. The Pennes conventional bio-heat equation has proven to be successful in analysing the data produced by microwave thermography. The thermal properties of biological soft tissue are dependant on the tissue water content. Water is a major constituent of most soft biological tissues, and it has a higher thermal conductivity and thermal diffusivity than any other constituent of biological tissue. The thermal properties of biological tissue can be modelled using a mixture equation, which describes the behaviour of a two phase system in terms of the thermal properties of the individual constituents and their relative volume fractions. This allows the variation of the thermal properties of biological tissue with water content to be analysed. A self-heating thermistor probe system was used in this study to measure the in-vitro thermal conductivity and thermal diffusivity of a wide variety of human and animal tissues. The system was calibrated using glycerol and agar-gelled water since the thermal behaviour of these materials and mixtures of these materials was well known. The calibration data was examined to determine the accuracy of the calibration and to determine if there was a relationship between the observed thermal conductivity and thermal diffusivity which was generated by the measurement syste

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

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    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

    APPLICATIONS OF HEAT AND MASS TRANSFER ANALYSIS IN BIO-MEDICINE AND MATERIALS

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    Heat and mass transfer analysis has its application in various fields including automobile, steam-electric power generation, energy systems, HVAC, electronic device cooling and in characterizing and diagnosing diseases. Here we have focused on applying the principles of heat and mass transfer to biological tissue and materials. In the first part we introduce a computational method to simultaneously estimate size, location and blood perfusion of model cancerous breast lesions from surface temperature data. A 2-dimensional computational phantom of axisymmetric tumorous breast with six tissue layers, epidermis, papillary dermis, reticular dermis, fat, gland, muscle layer and spherical tumor was used to generate surface temperature distributions and estimate tumor characteristics iteratively using an inverse algorithm based on the Levenberg-Marquardt method. However, similar steady state temperature profiles for different tumors are insufficient to simultaneously estimate blood perfusion, size and location of tumor. This becomes possible when transient temperature data are used along with steady state data. Thus, in addition to the steady state temperature data, we modified and expanded the inverse algorithm to include transient data that can be captured by dynamic infrared imaging. Blood perfusion is an indicator of the growth rate of the tumor and therefore its evaluation can lead to assessment of tumor malignancy. In the second part we treat X-ray computed tomography (CT) perfusion. The goal was to reduce the total radiation exposure by reducing the number of scans without compromising information integrity. CT scan images obtained from a rabbit model of liver and tumors were processed using the maximum slope (MS) method to estimate blood perfusion in the liver. Limitations of MS method are also discussed. The MS method makes use of key time points, forming the basis of the rationale to explore optimization strategies that utilize variable time intervals, rather than the more common approach of fixed time intervals. Results show that this leads to significant improvement, without compromising diagnostic information. In the last section we explore the magnetic shielding efficacy of superconducting materials and methods to mitigate the effect of necessary discontinuities in superconducting shield
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