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1
Лоєнко, Євген Олександрович. "Автоматизований лазерний терапевтичний опромінювач". Master's thesis, КПІ ім. Ігоря Сікорського, 2019. https://ela.kpi.ua/handle/123456789/30538.
Повний текст джерелаАнотація:
Магістерська атестаційна робота складається зі 162 аркушів. До неї входять 128 ілюстрацій, 14 таблиць, 4 додатки, 60 бібліографічних найменувань за переліком посилань.
Мета і задачі роботи: дослідити вплив опромінювання крові оптичним випромінюванням видимого діапазону на оксигенацію крові і частоту пульсу в залежності від типу шкіри, побудувати модель транспорту кисню в залежності від вмісту гемоглобіну в крові та встановити функціональні закономірності зміни відсоткового значення оксигенації в залежності від дози опромінення.
Об’єкт дослідження: зміна оксигенації крові і частоти пульсу при опроміненні крові оптичним випромінюванням видимого діапазону. Предмет дослідження: оксигенація крові і частота пульсу.
Результати проведених досліджень дозволили визначити час досягнення ефекту впливу оптичного випромінювання на показники крові в залежності від типу шкіри.
Результати роботи можуть бути впроваджені у виробництво медичної апаратури та практику її експлуатації, а також використані студентами, що спеціалізуються в області розробки медичних приладів.
За результатами досліджень опубліковано 7 наукових праць, у тому числі 1 стаття у наукових виданнях та 6 патентів України.Master’s degree work consists of 162 pages. It includes 128 illustrations, 14 tables, 4 enclosures, 60 bibliographical names by list of references. Goal and problems of this work are: to investigate influence of blood irradiation by optical radiation of visible range for blood oxygenation and pulse frequency depending on type of skin, to build model of oxygen transport according to blood saturation of hemoglobin and establish functional patterns of changes in percentage value of oxygenation depending on irradiation dose. Object of investigation: changes of blood oxygenation and pulse frequency under blood irradiation by optical radiation of visible range. Subject of investigation: blood saturation and pulse frequency. The results of conducted researches permitted to define time of effect achievement of optical radiation influence to blood results depending on type of skin. The results of this paper could be established into medical apparatus production and practice of its exploitation and applied by students, who specialize in development of medical devices. 7 scientific transactions, which include 1 articles in publications from list of State Commission for Academic Degrees and Titles and 6 patents of Ukraine, were published on the investigations’ results.
2
Aning, Jonathan. "Critique of fourier transform infrared microspectroscopy applications to prostate pathology diagnosis." Thesis, Cranfield University, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/5626.
Повний текст джерелаАнотація:
Prostate cancer is a biologically heterogenous disease with considerable variation in
clinical aggressiveness. Gleason grade, the universally accepted method for
classification of prostate cancer, is subjective and gives limited predictive information
regarding prostate cancer progression. There is a clinical need for an objective, reliable
tool to help pathologists improve current prostate tissue analysis methods and better
assess the malignant potential of prostate tumours. Fourier Transform Infrared (FTIR)
microspectroscopy is a powerful bioanalytical technique that uses infrared light to
interrogate biological tissue. The studies detailed in this thesis examine the ability of
FTIR combined with multivariate analysis to discriminate between benign,
premalignant and malignant prostate pathology in snap frozen, paraffinated and
deparaffinated tissue.
Prostate tissue was collected during and after urological procedures performed between
2005 and 2008. The tissue was analysed utilising a bench top FTIR system in point and
image mapping modes. The histology under interrogation was identified by a uro-
pathologist. Multivariate analysis was applied to the spectral dataset obtained. FTIR
performance was evaluated.
FTIR was able to reproducibly discriminate between benign and malignant prostate
tissue in a pilot study. Cross validated diagnostic algorithms, constructed from the
spectral dataset in this experiment, achieved sensitivities and specificities of 95% and
89% respectively.
FTIR analysis of transverse paraffinated and deparaffinated radical prostatectomy
sections achieved good differentiation of the benign, premalignant and malignant
pathology groups. However the performance of diagnostic algorithms constructed from
this dataset under cross validation was poor.
The work in this thesis illustrates the potential of FTIR to provide an objective method
to assist the pathologist in the assessment of prostate samples. The limitations of the
technique and directions for future work are presented.
3
Gates, Andrew R. C. "Blood flow studies using nuclear magnetic resonance imaging." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260496.
Повний текст джерела
4
Golemati, Spiretta. "Motion analysis of atherosclerotic plaque from b-mode ultrasound." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396015.
Повний текст джерела
5
Cleasen, Stefan. "A verification and display system for multiple modality DICOM 3.0 objects." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391942.
Повний текст джерела
6
Cole, Mary Janet. "Fluorescence lifetime imaging for biomedical applications." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393718.
Повний текст джерела
7
Taffler, Sean. "The use of the Hilbert Spectrum in the analysis of electromyographic signals and its application in the development of myoelectric prosthesis controllers." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393789.
Повний текст джерела
8
Zhang, Yongyue. "Model-based approaches to brain MR image segmentation." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393516.
Повний текст джерела
9
Xiao, Guofang. "3-D free-hand ultrasound imaging and image analysis of the breast." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393987.
Повний текст джерела
10
Garnett, Matthew Romney. "The nuclear magnetic resonance investigation of traumatic brain injury." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393513.
Повний текст джерела
11
Gear, Jonathan. "Polymer gels for dosimetry in targeted radionuclide therapy." Thesis, Institute of Cancer Research (University Of London), 2009. http://publications.icr.ac.uk/10124/.
Повний текст джерелаАнотація:
This thesis Presents an investigation into the use of polymer gel dosimeters for analysis in targeted radionuclide therapy (TRT). The project aims to establish viability, technical issues, and potential uses of polymer gel dosimetry when incorporating radioisotopes. The thesis begins by outlining the current status of TRT and the need for accurate dosimetry. The inaccuracies of the dosimetry methods being employed are highlighted, as is the requirement of a "gold standard" method for dosimetry quality assurance. Polymer gel dosimeters are porposed as a possible means of achieving this. As a research topic in its own right an introduction into polymer gel dosimeters is given with a detailed description of their development and current uses in external beam radiotherapy. In the thesis polymer gel dosimeters are used in conjunction with MR and a detailed description of the MR techniques used is also given. Monte Carlo simulations are currently considered the best method to determine absorbed dose from a known activity distribution. A Monte Carlo user code written for EGSnrc has been developed to verify and validate polymer gel dosimetry. Details of the Monte Carlo code are given and comparisons made with published data. The accuracy of poymer gel dosimetry is susceptible to many factors and use with internal isotopes may introduce further technical issues. These are investigated in a number of small experiments and comparison made with external beam irradiation. A method for using polymer gel dosimeters with internal isotopes is developed and verified by comparing dose measurements and distributions with that calculated using the Monte Carlo code. Comparisons with various SPECT based dosimetry techniques have been made for geometrical phantoms of both uniform and non-uniform distributions. Methods for comparing and analysing 3D dose maps have also been investigated and the results from these experiments discussed. The thesis concludes with a case study, whereby polymer gel dosimeters are used for analysis of a specific patient situation. A patient synopsis is given with details of an anatomical phantom based on that patient. Polymer gel and SPECT based dosimetry is performed and the clinical significance of the findings discussed.
12
Mohseni, Hamid R. "ERP source tracking and localization from single trial EEG MEG signals." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54898/.
Повний текст джерелаАнотація:
Electroencephalography (EEG) and magnetoencephalography (MEG), which are two of a number of neuroimaging techniques, are scalp recordings of the electrical activity of the brain. EEG and MEG (E/MEG) have excellent temporal resolution, they are easy to acquire, and have a wide range of applications in science, medicine and engineering. These valuable signals, however, suffer from poor spatial resolution and in many cases from very low signal to noise ratios. In this study, new computational methods for analyzing and improving the quality of E/MEG signals are presented. We mainly focus on single trial event-related potential (ERP) estimation and E/MEG dipole source localization. Several methods basically based on particle filtering (PF) are proposed. First, a method using PF for single trial estimation of ERP signals is considered. In this method, the wavelet coefficients of each ERP are assumed to be a Markovian process and do not change extensively across trials. The wavelet coefficients are then estimated recursively using PF. The results both for simulations and real data are compared with those of the well known Kalman Filtering (KF) approach. In the next method we move from single trial estimation to source localization of E/MEG signals. The beamforming (BF) approach for dipole source localization is generalized based on prior information about the noise. BF is in fact a spatial filter that minimizes the power of all the signals at the output of the filter except those that come from the locations of interest. In the proposed method, using two more constraints than in the classical BF formulation, the output noise powers are minimized and the interference activities are stopped.
13
Alex, Aneesh. "Multispectral three-dimensional optical coherence tomography." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54164/.
Повний текст джерелаАнотація:
A spectral-domain OCT system operating at 1300 nm wavelength region, capable of acquiring 47,000 A-lines/s, was designed and developed. Its axial and transverse resolutions were ∼ 6 µm and ∼15 µm respectively. OCT images of human skin were obtained in vivo using three OCT systems, in order to find the optimal wavelength region for dermal imaging. 800 nm OCT system provided better image contrast over other two wavelength regions. Meanwhile, 1300 nm wavelength region was needed to obtain information from deeper dermal layers. To determine the effect of melanin pigmentation on OCT, images were taken from subjects with different ethnic origins. Interestingly, melanin pigmentation was found to have little effect on penetration depth in OCT. In vitro tumour samples, comprising samples with different degrees of dysplasia, were imaged at 800 nm, 1060 nm and 1300 nm wavelength regions to find the capability of OCT to diagnose microstructural changes occurring during tumour progression. 800 nm OCT system was capable to detect the malignant changes with higher contrast than other wavelength regions. However, higher wavelength regions were required to penetrate deeper in densely scattering tumour samples at advanced stages. OCT system operating at 1060 nm was combined with a photoacoustic imaging (PAT) system to obtain complementary information from biological tissues. This multimodal OCT/PAT system demonstrated its potential to deliver microstructural information based on optical scattering and vascular information based on optical absorption in living mice and human skin. The results indicate OCT as a promising imaging modality that can have profound applications in several areas of clinical diagnostic imaging.
14
Ravindranathan, Devi. "Photoplethysmography for the evaluation of diabetic autonomic neuropathy." Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/54981/.
Повний текст джерелаАнотація:
The aim of this study was to determine if photoplethysmography (PPG) could be used to analyse the foot microvascular changes caused by diabetic autonomic neuropathy. The digital PPG signals were collected from 37 healthy volunteers (Group I), 35 diabetic patients (Group II), and 38 diabetic patients with sensory neuropathy (Group III) and analysed using MAT LAB. Prominent spectral peaks with sidebands were obtained at both the high frequency (HF) and the low frequency (LF) end of the Fourier spectrum of these PPG signals. Previous studies of microcirculation have shown that both are sympathetically and parasympathetically mediated and hence are a good measure of the autonomic activity. In the HF analysis, the heart rate (HR) response from 13 participants in Group III was severely reduced and significantly different from the responses obtained from the other two groups. However the responses from remaining 25 participants had similar characteristics to those of Group II. Hence the HF analyses failed to both statistically and objectively differentiate between the diabetics with and without neuropathy. The spectral density for the frequency bandwidth of 3-20 cpm was significantly reduced in the neuropathic group, compared to the other two groups. A Statistically significant difference was observed in the spectral densities calculated from Group II and III, though no difference could be established between Groups I and III. The LF analysis of this bandwidth differentiated between Groups II and III with a sensitivity of 84% and specificity of 61%. Activities at the LF end of the spectrum mostly represent the sympathetic control as opposed to the HR variability that is mostly a measure of the parasympathetic control. These results suggest that sympathetic dysfunction possibly precedes parasympathetic dysfunction and that PPG can assess the changes in the skin microcirculation due to sympathetic damage with moderate success.
15
Nazarpour, Kianoush. "Brain signal analysis in space-time-frequency domain : an application to brain computer interfacing." Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54718/.
Повний текст джерелаАнотація:
In this dissertation, advanced methods for electroencephalogram (EEG) signal analysis in the space-time-frequency (STF) domain with applications to eye-blink (EB) artifact removal and brain computer interfacing (BCI) are developed. The two methods for EB artifact removal from EEGs are presented which respectively include the estimated spatial signatures of the EB artifacts into the signal extraction and the robust beamforming frameworks. In the developed signal extraction algorithm, the EB artifacts are extracted as uncorrelated signals from EEGs. The algorithm utilizes the spatial signatures of the EB artifacts as priori knowledge in the signal extraction stage. The spatial distributions are identified using the STF model of EEGs. In the robust beamforming approach, first a novel space-time-frequency/time-segment (STF-TS) model for EEGs is introduced. The estimated spatial signatures of the EBs are then taken into account in order to restore the artifact contaminated EEG measurements. Both algorithms are evaluated by using the simulated and real EEGs and shown to produce comparable results to that of conventional approaches. Finally, an effective paradigm for BCI is introduced. In this approach prior physiological knowledge of spectrally band limited steady-state movement related potentials is exploited. The results consolidate the method.
16
Cosker, Darren. "Animation of a hierarchical image based facial model and perceptual analysis of visual speech." Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/56003/.
Повний текст джерелаАнотація:
In this Thesis a hierarchical image-based 2D talking head model is presented, together with robust automatic and semi-automatic animation techniques, and a novel perceptual method for evaluating visual-speech based on the McGurk effect. The novelty of the hierarchical facial model stems from the fact that sub-facial areas are modelled individually. To produce a facial animation, animations for a set of chosen facial areas are first produced, either by key-framing sub-facial parameter values, or using a continuous input speech signal, and then combined into a full facial output. Modelling hierarchically has several attractive qualities. It isolates variation in sub-facial regions from the rest of the face, and therefore provides a high degree of control over different facial parts along with meaningful image based animation parameters. The automatic synthesis of animations may be achieved using speech not originally included in the training set. The model is also able to automatically animate pauses, hesitations and non-verbal (or non-speech related) sounds and actions. To automatically produce visual-speech, two novel analysis and synthesis methods are proposed. The first method utilises a Speech-Appearance Model (SAM), and the second uses a Hidden Markov Coarticulation Model (HMCM) - based on a Hidden Markov Model (HMM). To evaluate synthesised animations (irrespective of whether they are rendered semi automatically, or using speech), a new perceptual analysis approach based on the McGurk effect is proposed. This measure provides both an unbiased and quantitative method for evaluating talking head visual speech quality and overall perceptual realism. A combination of this new approach, along with other objective and perceptual evaluation techniques, are employed for a thorough evaluation of hierarchical model animations.
17
Mitchell, Claire. "The development of new imaging strategies of human tumour vasculature." Thesis, University of Manchester, 2010. http://www.manchester.ac.uk/escholar/uk-ac-man-scw:123697.
Повний текст джерела
18
Naeini, Mandana Rafiei. "Low-noise measurement techniques for brain function imaging by electrical impedance tomography." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488642.
Повний текст джерелаАнотація:
In neurosciences, there is a great need to improve methods for direct imaging of functional activity in the nervous system of the brain. Such activities occur on a time scale of the order of 10 milliseconds. No portable system exists to measure these activities non-invasively with sufficient temporal resolution and with sensitivity to the deepest regions of the brain. Electrical Impedance Tomography (EIT), as a non-invasive means for fast imaging of impedance changes during neural activity, has the promise to be highly portable, to give information on the deepest regions of the brain, and is already applied routinely in other medical applications such as breast imaging. For this technique to 'follow' the human brain's processing cycle for individual stimuli, a temporal resolution of much less than 1 second is required. The sensitivity and spatial resolution of EIT can be enhanced significantly by increasing the measurementSNR. It has been suggested that an EIT system with measurement s~nsitivity of 80 dB is required for the measurement of impedance changes in the brain occurring directly due to neural function. For this application, the University of Manchester is developing a 32channel EIT system, fElTER, with temporal resolution of 100 frames per second and SNR of 80 dB, operating over the current excitation frequency range from 10 kHz to 100 kHz. In this thesis, a modular single-channel EIT system is designed to investigate ways of achieving the high performance requirements of the fEITER system. It uses digital waveform synthesis, a 16-bit DAC and subsequent reconstmction filter, to drive the improved Howland current source. The voltage is measured using an instmmentation amplifier followed by an anti-aliasing filter and a 16-bit ADC, prior to digital PSD where the amplitude and phase information of the measured voltage is obtained. In this system the digital parts are implemented in an FPGA. The design considerations to achieve the required performance related to each module are discussed prior to design, implementation and testing related to each module in a separate chapter. The resulting single-channel EIT system operates in the frequency range of 10 kHz to 100 kHz in steps of 10 kHz. The SNR perfoffilance of the developed system is 77 dB and it has the potential of achieving 100 frames per second image acquisition for the 32-channel fEITER system.
19
Hardie, Donald. "Non-linear modelling of microwave soft-tissue ablation using the finite element method." Thesis, Heriot-Watt University, 2006. http://hdl.handle.net/10399/2077.
Повний текст джерелаАнотація:
Reliable and accurate information regarding the heat distribution inside biologica.I tissue due to microwave thennal ablation is essential for the design and optimization of safe therapeutic applicators and for the development of experiments, which aim to investigate their effects. To date, very few finite element models (FEM) have been developed to describe and illustrate electric field penetration, specific absorption rate (SAR) and temperature distribution in biological tissue due to microwave ablation probes. A coupled field finite elemerit analysis model that accounts for the temperature dependent conductivity and blood perfusion changes has not, as yet, been developed for ablation type devices. Although it is widely acknowledged that accounting for temperature dependent phenomena may affect the outcome ofthese models, the effect has not yet been assessed for microwave tumour ablation (MTA). This thesis aims to develop an improved non-linear coupled field electromagnetic and thermal FE model of microwave ablation, incorporating temperature dependent electrical and thermal properties of, ex-vivo bovine liver. Measurements of temperature dependent ex-vivo bovine liver electrical permittivity are made and their effect. presented. Temperature dependent thennal properties of the tissue are limited. to temperatures below phase change. Therefore, a theoretical tissue model for going changes in phase is also presented. The FE model of microwave ablation is based on a 2.45 GHz minimally invasive dielectric loaded monopole antenna
20
Alonzi, Roberto. "Evaluation of the oxygenation and vascularity of prostate cancer using magnetic resonance imaging." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1444256/.
Повний текст джерелаАнотація:
The outcome of radical treatment for prostate cancer is appreciably influenced by the presence of hypoxia. Oxygenation status may therefore be another underlying biological parameter, beyond the classic prognostic factors (age, clinical stage, Gleason score and prostate specific antigen), that predicts for treatment failure in this malignancy. Angiogenesis plays a pivotal role in the growth, invasion, metastasis and survival of prostate tumours. Measurements of angiogenesis have been linked with clinical and pathological stage, histological grade and the potential for metastasis formation. They also provide prognostic information and have been correlated with disease-specific survival and progression after treatment. Magnetic resonance imaging techniques are capable of detecting the molecular, biochemical, physiological and metabolic changes that occur due to pathological processes within tissues. Experiments presented in this thesis have sought to evaluate the ability of Dynamic Contrast Enhanced MRI (DCE-MRI), Dynamic Susceptibility Contrast MRI (DSC-MRI), Intrinsic Susceptibility Weighted MRI (also known as Blood Oxygen Level Dependent (BOLD) MRI) and Diffusion Weighted Imaging (DWI) to characterise the oxygenation and vascular status of prostate tumours in animal models and in patients with prostate cancer. This research has demonstrated the feasibility of hypoxia imaging in prostate cancer. Although MRI can not precisely map tissue p02, the combination of BOLD-MRI and dynamic susceptibility contrast MRI provides a valuable surrogate and predicts the pattern of hypoxia, as determined by pimonidazole immunohistochemistry, with reasonable accuracy. The research has also shown that prostate cancer responds to carbogen gas breathing and that androgen deprivation causes profound vascular collapse within one month of starting therapy. These findings should help in the rational design of future studies that aim to target tumour vasculature and combat tumour hypoxia in prostate cancer.
21
Reid, C. "Spectroscopic methods for medical diagnosis at terahertz wavelengths." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/17571/.
Повний текст джерелаАнотація:
Terahertz (THz) radiation lies between the microwave and infrared regions of the electromagnetic spectrum. THz radiation excites intermolecular interactions and is non-ionising making it a viable tool for medical imaging. This thesis describes the development and validation of spectroscopic methods for diagnosis of tissue pathologies at THz wavelengths. Theoretical techniques were developed to determine the origin of the contrast seen in THz images of biological tissue. Specific biological tissues investigated in this thesis were colonic tissues with the aim of determining the origin of contrast between healthy and diseased tissue in THz images. This thesis investigates the interaction of THz radiation with matter using simple tissue phantoms made from five biologically relevant materials: water, methanol, lipid, sucrose and gelatin. Phantoms are designed to imitate the spectroscopic properties of tissue at specific wavelengths where physical properties of the phantom, such as concentration and homogeneity, can be accurately controlled. The frequency-dependent absorption coefficients, refractive indices and Debye relaxation times of the pure compounds were measured and used as prior knowledge in the different theoretical methods for the determination of concentration. Three concentration analysis methods were investigated, a) linear spectral decomposition, b) spectrally averaged dielectric coefficient method and c) the Debye relaxation coefficient method. These methods were validated on phantoms by determining the concentrations of the phantom chromophores and comparing to the known composition. Two-component phantoms were made comprising water with methanol, lipid, sucrose or gelatin. Two different three-component phantoms were created; one with water, methanol and sucrose and a second with water, gelatin and lipid. The accuracy and resolution of each method was determined to assess the potential of each method as a tool for medical diagnosis at THz wavelengths. Finally, the spectroscopic methods were applied to measurements of ex-vivo colon tissues containing cancerous and dysplastic regions. Statistical analysis of the reflected time-domain waveforms demonstrated good distinction between healthy and diseased tissues with an estimated sensitivity of 89.2% and specificity of 78.3%.
22
Gilad, Ori. "Preliminary studies in imaging neuronal depolarization in the brain with electrical or magnetic detection impedance tomography." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1444179/.
Повний текст джерелаАнотація:
Electrical impedance Tomography (EIT) is a novel medical imaging method which has the potential to provide the revolutionary advance of a method to image fast neural activity non-invasively. by imaging electrical impedance changes over milliseconds which occur when neuronal ion channels open during activity. These changes have been estimated to be c.1% locally in cerebral cortex, if measured with applied current below 100Hz. The purpose of this work was to determine if such changes could be reproducibly recorded in humans non invasive First, a novel recessed electrode was designed and tested to determine to enable a maximal current of 1mA to be applied to the scalp without causing painful skin sensation. Modelling indicated that this produced a peak current density of 0.3A/m2 in underlying cortex, which was below the threshold for stimulation. Next, the signal-to-noise ratio of impedance changes during evoked visual activity was investigated in healthy volunteers with current injected with scalp electrodes and recording of potential by scalp electrodes (Low Frequency EIT) or magnetic field by magnetoencephalography (Magnetic Detection EIT). Numerical FEM simulations predicted that resistivity changes of 1% in the primary7 visual cortex translate into scalp voltage changes of IjiV (0.004%) and external magnetic field changes of 30fT (0.2%) and were independently validated in saline filled tanks. In vivo, similar changes with a signal-to-noise ratio of 3 after averaging for 10 minutes were recorded for both methods the main noise sources were background brain activity and the current source. These studies with non-invasive scalp recording have, for the first time, demonstrated the existence of such changes when measured non-invasively. These are unfortunately too low to enable reliable imaging within a realistic recording time but support the view that such imaging could be possible in animal or human epileptic studies with electrodes placed on the brain or non-invasively following technological improvements this further work is currently in progress.
23
Holder, David Simon. "An Assessment of Some Possible Neurological Applications of Electrical Impedance Tomography." Thesis, University College London (University of London), 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518534.
Повний текст джерела
24
McClelland, James Robert. "Registration based respiratory motion models for use in lung radiotherapy." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1444228/.
Повний текст джерелаАнотація:
Respiratory motion is a major factor contributing to errors and uncertainties in Radiotherapy (RT) treatment of lung tumours. Knowledge of this motion may improve the planning and delivery of RT treatment for lung cancer patients. This thesis develops and evaluates methods of building patient specific respiratory motion models. These relate the internal motion to respiratory parameters derived from an external surrogate signal that can be measured during data acquisition and treatment delivery. The models offer a number of advantages over current methods of imaging and analysing respiratory motion, in particular their ability to account for variations in the respiratory motion. Computer Tomography (CT) data is acquired over several respiratory cycles to sample some of the variation in the respiratory motion. B-spline registrations are used to recover the motion and deformation from the CT data. The models are then constructed by fitting functions that relate the registration results to the respiratory parameters. This thesis describes the CT data and respiratory parameters that have been used to construct the motion models. It details the registrations protocols used and evaluates their results. The initial models presented in the thesis relate the registration results to a single parameter, the phase of the respiratory cycle, and average out any variation in the respiratory motion. The later models relate the registration results to two respiratory parameters, with the intention of modelling some of the variation. A number of different functions are assessed for both the single and two parameter models. The results show that the models can predict the respiratory motion in the CT data very accurately (mean error < 1.4 mm). This thesis also discusses some of the uses of the motion models in RT and, in particular, explores the use of the motion models for 'tracking' respiratory motion while delivering intensity modulated RT.
25
Donaldson, Nicholas de Neufville. "The electrical design of an implantable stimulator to restore motor control to the paralysed." Thesis, University College London (University of London), 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507521.
Повний текст джерела
26
Wächter, I. "3D reconstruction of cerebral blood flow and vessel morphology from X-ray rotational angiography." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/16356/.
Повний текст джерелаАнотація:
Three-dimensional (3D) information on blood flow and vessel morphology is important when assessing cerebrovascular disease and when monitoring interventions. Rotational angiography is nowadays routinely used to determine the geometry of the cerebral vasculature. To this end, contrast agent is injected into one of the supplying arteries and the x-ray system rotates around the head of the patient while it acquires a sequence of x-ray images. Besides information on the 3D geometry, this sequence also contains information on blood flow, as it is possible to observe how the contrast agent is transported by the blood. The main goal of this thesis is to exploit this information for the quantitative analysis of blood flow. I propose a model-based method, called flow map fitting, which determines the blood flow waveform and the mean volumetric flow rate in the large cerebral arteries. The method uses a model of contrast agent transport to determine the flow parameters from the spatio-temporal progression of the contrast agent concentration, represented by a flow map. Furthermore, it overcomes artefacts due to the rotation (overlapping vessels and foreshortened vessels at some projection angles) of the c-arm using a reliability map. For the flow quantification, small changes to the clinical protocol of rotational angiography are desirable. These, however, hamper the standard 3D reconstruction. Therefore, a new method for the 3D reconstruction of the vessel morphology which is tailored to this application is also presented. To the best of my knowledge, I have presented the first quantitative results for blood flow quantification from rotational angiography. Additionally, the model-based approach overcomes several problems which are known from flow quantification methods for planar angiography. The method was mainly validated on images from different phantom experiments. In most cases, the relative error was between 5% and 10% for the volumetric mean flow rate and between 10% and 15% for the blood flow waveform. Additionally, the applicability of the flow model was shown on clinical images from planar angiographic acquisitions. From this, I conclude that the method has the potential to give quantitative estimates of blood flow parameters during cerebrovascular interventions.
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Bohndiek, Sarah Elizabeth. "Active pixel sensors for breast biopsy analysis using X-ray diffraction." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1444112/.
Повний текст джерелаАнотація:
Breast cancer diagnosis currently requires biopsy samples to be analysed by a histopathologist a time consuming, highly specialised process. X-ray diffraction is a quantitative technique that can distinguish between healthy and diseased breast biopsy samples using the change in proportions of fat and fibrous tissue that occurs when cancer invades. A semi-automated breast biopsy analysis system based on X-ray diffraction could yield a faster patient diagnosis. Recording X-ray diffraction patterns is a challenging task needing low noise, large area, and wide dynamic range detectors. Scientific complementary metal oxide semiconductor (CMOS) Active Pixel Sensors will soon be able to meet all of these demands in a single device. Characterization of two novel Active Pixel Sensors that advance towards an ideal X-ray diffraction detector is presented. 'Vanilla' exhibits a low read noise of 55e r.m.s. and high quantum efficiency of up to 70% so was selected for the design and implementation of the first 'Active Pixel X-ray Diffraction' (APXRD) system. Following on from Vanilla, the 'Large Area Sensor' (LAS) covered an area of over 29cm2 and had a wide dynamic range of over 95dB. The first linear systems model of an Active Pixel Flat Panel Imager (scintillator coupled APS) was formulated in the design of the APXRD system, to select filters to narrow the spectral width of the X-ray beam and predict the recorded scatter intensity. Following system implementation, scatter signatures were recorded for numerous breast tissue equivalent samples. A multivariate analysis model calibrated with these was able to predict the percentage fat content of an 'unknown' sample to within 3% a very promising result. The width of the filtered polychromatic X-ray spectrum had only a minor influence on the APXRD scatter signatures indicating that the system preserves all relevant structural information.
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Bhardwaj, Neil. "Ablation of liver tissue : a comparison between microwave, cryotherapy and radiofrequency." Thesis, University of Leicester, 2011. http://hdl.handle.net/2381/9509.
Повний текст джерелаАнотація:
Introduction The majority of primary and secondary liver tumours are inoperable. „In situ‟ thermal destruction techniques such as radiofrequency, microwave ablation and cryotherapy have been employed to treat these inoperable tumours. Despite recent advances in these technologies, large and peri-vascular tumours still suffer from a relatively high recurrence rate post ablation. This is thought to be due to the loss of thermal energy to surrounding vasculature, known as the heat sink effect. The aim of this project was to investigate the effect of surrounding vasculature on ablation morphology and success and compare the three most popular ablation modalities. Methods Standard sized ablations were created in rat liver at various distances from the hilum with all three methods. At various time points, tissue samples were retrieved and underwent histological (H&E) and immuno-cytochemical (Hsp70 and Caspase 3) staining in order to assess lesion evolution and the effects of surrounding vasculature on ablation completeness. Results All rats survived. The greatest amount of activity was seen in the transition zone. H&E and immuno-cytochemical analyses of lesion evolution discovered previously unreported cellular changes, particularly in the transition zone. Cryotherapy ablation seemed to be the most irregular and unpredictable of the three. Radiofrequency ablation was uniform but showed evidence of extra-lesional apoptosis and perivascular cell survival in addition to Hsp 70 activity in the transition zone that was affected by surrounding vasculature. Microwave ablation seemed to be influenced least by surrounding vasculature and formed the most uniform lesion with very little extra-lesional collateral damage. Conclusion The success of ablation is dependent upon the adjacent blood vessels and microwave ablation seemed to form the most predictable burn and be least affected by surrounding vasculature compared to radiofrequency. Cryotherapy should not be used as first line treatment to treat unresectable liver tumours. In addition the exact role of HSP 70 on the fate of cells in the transition zone, and the subsequent final ablation size and morphology is yet to be determined. Larger ablations in larger animal models may help answer some of these questions.
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Chin, Kong Yien. "A new approach for non-invasive continuous arterial blood pressure measurement in human." Thesis, University of Leicester, 2011. http://hdl.handle.net/2381/10253.
Повний текст джерелаАнотація:
The need for continuous noninvasive arterial blood pressure (ABP) monitoring from an artery closer to the heart (i.e. the ascending aorta) has led to the research and development work presented in this thesis. Clinical applications of continuous ABP waveform include assessments of cardiac function, cerebral autoregulation, autonomic function, arterial elasticity, physiological measurements in aerospace research, and also monitoring in anaesthesia and critical care. The superficial temporal artery (STA) was chosen as the measurement site and the measurement technique was the arterial volume clamping with photoplethysmography (PPG). The optoelectronic circuitry to measure PPG is contained in a specially designed probe placed over the STA and kept in place with a lightweight aluminium head frame. The complete prototype device (STAbp) also includes original designs for the pneumatic, electronic, signal processing, control and display sub-systems. A self-calibration feature that regularly updates the PPG reference level (Setpt) was also included to ensure accurate continuous ABP recording. The performance of the STAbp was compared against the Finapres®. Five parameters were evaluated: resting ABP (agreement, signal bandwidth, frequency response and magnitude squared coherence, and assessment of drift) and ABP dynamic change during isometric handgrip exercise. The agreement of resting ABP gave bias (SD) of -23.1 (15.05), -10.8 (13.83) and -12.4 (12.93) mmHg for systolic, mean (MAP) and diastolic pressures respectively. Further investigations were carried out to understand factors that can affect the accuracy of ABP measurements, notably the sensitivity of ABP to perturbation of the Setpt. Also, differences between the external compressing pressure at the PPG peak pulsation amplitude and the MAP were found to be normally distributed with mean (SD) of -4.7 (5.63) mmHg. In conclusion, it is demonstrated that the new STAbp device has great potential as a new tool for a wide range of clinical and research applications which require continuous ABP waveforms.
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Jarchi, Delaram. "Estimation of single trial ERPs and EEG phase synchronization with application to mental fatigue." Thesis, University of Surrey, 2011. http://epubs.surrey.ac.uk/804408/.
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Richard, Morgiane. "A computer model of in vitro cellular response to radiation." Thesis, University of Surrey, 2008. http://epubs.surrey.ac.uk/2239/.
Повний текст джерелаАнотація:
It is believed that irradiation interacts with biological tissues to break or modify the DNA, which is the molecule contained in the nuclei of cells that carries all the relevant information for the organism. As such, radiation is dangerous for individuals; however, its properties can also be used in medicine, e.g.. in cancer treatments. Nevertheless, the exact mechanisms of cellular response to radiation are not fully understood yet, especially for low doses (below 50 cGy), where non-targeted effects, i.e. that do not involve only the interactions radiation-DNA, are taking place. In order to deepen the knowledge of those non-targeted effects,a.computer model of a population of cells irradiated in vitro was written, taking into account the phenomena in the low dose domain. As a start, two non-targeted effects were studied, the bystander effect and the low dose hyperradiosensitivity. The program was written in C++ and the technique of the cellular automaton was used. The clonogenic assay was reproduced; cells were seeded in a dish and if the colony they formed after a given period of time was bigger than 50 cells, the seeded cells were assumed to have survived. The direct effect of radiation was calculated by the traditional linear quadratic model and in addition cells were subjected to the bystander effect. Some simulations were run in the case of two cell lines, the hamster cell line V79 and the glioma cell line T98G. The results show that the bystander effect is unlikely to be limited to one period of the cell cycle, but that the low dose hyper-radiosensitivity and the bystander effect could be the same phenomenon. This work also suggests that the bystander effect may be significant after low doses of conventional radiotherapy. Such a model represents a very useful tool for solving problems that at the moment cannot be investigated experimentally.
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Alzimami, Khalid. "The potential use of cerium-doped lanthanum scintillators and optimisation of imaging processing in SPECT." Thesis, University of Surrey, 2010. http://epubs.surrey.ac.uk/795818/.
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Tang, Kit Tzu. "Development and evaluation of free-living physical activity monitoring devices for application in clinical populations." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=12392.
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MacIntyre, Lynsey. "Application of matrix-assisted laser desorption/ionisation (MALDI) imaging mass spectrometry and high resolution Fourier transform mass spectrometry for profiling pharmaceuticals and biomarkers in a variety of biological samples." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=15488.
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MacLellan, Steven. "Novel polymeric magnetic resonance imaging (MRI) contrast agents." Thesis, University of Strathclyde, 2009. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=12805.
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Makani, Julie. "Defining the clinical spectrum of sickle cell disease in Tanzania : a clinico-epidemiological study." Thesis, Open University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545678.
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Al-Mandil, Maryam Mansour. "Pulsed short wave therapy : its clinical use and physiological effects in healthy subjects and osteoarthritic patients." Thesis, University of Hertfordshire, 2004. http://hdl.handle.net/2299/14364.
Повний текст джерелаАнотація:
PSWT is a commonly used electrotherapy modality and surveys have shown it to be one of the most widely used modalities among physiotherapists in the UK. Nevertheless, the literature supporting its therapeutic effects and explaining its mechanism of actions remains scant, is of poor methodological quality and of minimal clinical value. This research program was set to examine both the nature of use and the efficacy of PSWT. The nature of PSWT use was examined in outpatient clinics using an audit and a nationwide survey. The efficacy of PSWT was examined in two randomised placebo controlled trials; one conducted in a laboratory setting on healthy subjects and the other was a clinical trial on patients with osteoarthritis. Following the same methodology and protocol, the effects of low and high dose of PSWT on skin temperature (SkT), blood volume (BVol), and nerve conduction velocity (NCV) were evaluated against a placebo and a control condition. The findings have revealed the poor documentary skills of physiotherapists, and a state of confusion ~n the clinical decision-making with regard to PSWT dosage. Based on experimentation, it was established that patients react differently from healthy subjects when similar levels of energies are applied. Whilst low dose resulted in non-significant changes in SkT and NCV in healthy subjects, the same dose significantly altered BVol, SkT, and NCV in patients. Placebo effects were found to account for 39% of the patients' response to PSWT treatments. The findings have revealed a discrepancy between evidence and practice that necessitates a reconsideration of the treatment approaches adopted by physiotherapists when using PSWT. The study has also demonstrated the physiological and therapeutic efficacy of PSWT on patients with osteoarthritis, and showed that treatment outcomes are dependent on the amount of exogenous energy applied and the type of tissue treated. The thesis also highlights areas for future research based on the literature reviewed and the experimentation conducted.
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Dungey, Fiona A. "Targeting replication-specific DNA repair pathways to enhance the therapeutic ratio of brain tumour radiotherapy." Thesis, University of Sussex, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506947.
Повний текст джерелаАнотація:
Glioblastoma multiforme is associated with poor prognosis and resistance to standard therapy. However the non-dividing nature of normal brain provides an opportunity for enhancing the therapeutic ratio by combining radiation with inhibitors of replication-specific DNA repair pathways. KU-0059436, an inhibitor of the base excision repair (BER) protein poly(ADP-ribose) polymerase (PARP), was demonstrated to specifically radiosensitise glioma cells during S-phase and to increase lonising radiation (IR)-induced γH2AX and Rad51 foci. This radiosensitisation was enhanced using fractionated radiation, possibly because more cells were exposed to IR whilst in S-phase. A model is proposed whereby PARP inhibition decreases repair of radiation-induced single strand breaks (SSB) which are converted at collapsed replication forks to double strand breaks (DSB) requiring homologous recombination (HR) for repair. To investigate whether inhibition of downstream HR repair potentiates the radiosensitising effect of KU-0059436, and in the absence of specific HR inhibitors, the heat shock protein 90 (HSP90) inhibitor 17-AAG was used. This compound exhibits tumour-specific cytotoxic and radiosensitising properties and downregulates the HR proteins BRCA2 and Rad5l. Work in this thesis confirmed that 17-AAG inhibits HRR and radiosensitises glioma cells. Radiosensitisation was replication-dependent and was increased in the presence of KU-0059436. The combined effect was at least partially replication-dependent, was associated with increased γH2AX foci in G2 cells, and was absent in non-malignant CHO cells. Since Rad5l-depleted cells were also radiosensitised by 17-AAG, this effect could not be attributed entirely to HRR inhibition. 17-AAG inhibits multiple tumour survival and DNA repair pathways that may contribute to its enhancement of the replication-dependent effects of KU-0059436. These multiple mechanisms may be difficult to elucidate but are likely to be therapeutically beneficial. In summary, the combination of HSP90 and PARP inhibitors may potentially improve brain tumour radiotherapy by mechanisms that include but are not restricted to inhibition of the BER and HRR DNA repair pathways.
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Natsheh, Abdel-Razzak. "Neural network based hybrid algorithm for automated diagnosis in ENT applications." Thesis, Manchester Metropolitan University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534244.
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Babrah, Jaspreet. "A study of FT-IR spectroscopy for the identification and classifcation of haematological malignancies." Thesis, Cranfield University, 2009. http://dspace.lib.cranfield.ac.uk/handle/1826/4594.
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The aim of the work presented in this thesis was to explore the use of FT-IR spectroscopy, as a complementary clinical tool for haematological laboratory analysis. FT-IR spectra were measured from air-dried and frozen cell lines derived from lymphoma, lymphoid, myeloid leukaemia and normal and chronic lymphocytic leukaemia blood samples. Multivariate statistical analysis was used to extract important spectral information with the greatest discriminative power. Principal component fed linear discriminant spectral models have been tested with leave one out cross validation procedures. A preliminary unfiltered classification model using 50 frozen and air-dried samples correctly classified 54% of 18556 spectra. The performance improved with the three cell line group datasets, with 71% of 19903 spectra correctly classified. Furthermore, the use of the frozen spectra improved the performance of the three cell line group classification model considerably. Findings showed that 73.3% of 9920 spectra were correctly classified in the frozen datasets, whereas in the air-dried only 41.5% of 9983 spectra are correctly classified. Optimisation of the spectral models by selection of principal components, application of Savitsky-Golay filters and selecting spectra using standard deviation and absorption filter tool was investigated. Using the first 25 significant PCs, a 0 th derivative Savitsky-Golay filter and the absorbance filter tool on the frozen five cell line spectral dataset were shown to be the optimal parameters for constructing a classification model. When tested with leave one batch out cross validation 90% of the spectra were correctly classified for the five cell line model. Blood component classification models tested with leave one batch out cross validation performed well. The whole blood model correctly classified 70% of 1736 spectra, measured on 22 samples. The plasma model correctly classified 80.6% of 331 spectra and the buffy coat model correctly classified 99.5% of 1438 spectra. This demonstrated that the buffy coat (containing white blood cells) holds the key biochemical information for discrimination between the pathology of the blood samples. Partial least squares analysis has been demonstrated as a method to support whole blood count tests for real time prediction of cellular constituents. These findings demonstrate the potential of FT- IR spectroscopy as a clinical tool although more work is needed if it is to be applied in clinical practice.
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Sattlecker, Martina. "Optimisation of machine learning methods for cancer detection using vibrational spectroscopy." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/6286.
Повний текст джерелаАнотація:
Early cancer detection drastically improves the chances of cure and therefore methods are required, which allow early detection and screening in a fast, reliable and inexpensive manner. A prospective method, featuring all these characteristics, is vibrational spectroscopy. In order to take the next step towards the development of this technology into a clinical diagnostic tool, classification and imaging methods for an automated diagnosis based on spectral data are required. For this study, Raman spectra, derived from axillary lymph node tissue from breast cancer patients, were used to develop a diagnostic model. For this purpose different classification methods were investigated. A support vector machine (SVM) proved to be the best choice of classification method since it classified 100% of the unseen test set correctly. The resulting diagnostic models were thoroughly tested for their robustness to the spectral corruptions that would be expected to occur during routine clinical analysis. It showed that sufficient robustness is provided for a future diagnostic routine application. SVMs demonstrated to be a powerful classifier for Raman data and due to that they were also investigated for infrared spectroscopic data. Since it was found that a single SVM was not capable of reliably predicting breast cancer pathology based on tissue calcifications measured by infrared micro-spectroscopy a SVM ensemble system was implemented. The resulting multi-class SVM ensemble predicted the pathology of the unseen test set with an accuracy of 88.9%, in comparison a single SVM assessed with the same unseen test set achieved 66.7% accuracy. In addition, the ensemble system was extended for analysing complete infrared maps obtained from breast tissue specimens. The resulting imaging method successfully detected and staged calcification in infrared maps. Furthermore, this imaging approach revealed new insights into the calcification process in malignant development, which was not previously well understood.
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Knobloch, Henri. "Serum and urine headspace using electronic nose (e-nose) technology." Thesis, Cranfield University, 2009. http://dspace.lib.cranfield.ac.uk/handle/1826/6974.
Повний текст джерелаАнотація:
For the last 20 years, several applications of electronic nose (e-nose) have been reported in the area of microbiology, environmental and agricultural monitoring or medical diagnosis. E-noses were used to detect contaminants or for quality control. However, little has been reported about complex methodological problems which are strongly linked to the e-nose performance. This thesis summarises various e-nose systems and alternatives for gas and headspace analysis, highlights the essential problems associated with e-nose analysis and explains why these devices have a potential for the detection of trace gas molecules but also why a stable and reliable analysis is not possible yet. Methodological weaknesses such as changes in mass flow rates, filter application or sampling methods are addressed. Understanding these enables analysis of serum and urine samples from cattle or badgers either naturally or experimentally infected with the zoonotic diseases caused by Mycoplasma bovis, Mannheimia haemolytica A1, Mycobacterium bovis, Mycobacterium avium ssp. paraTuberculosis and Brucella sp. The circumstances under which meaningful results can be obtained using the ST214 e-nose (Scensive Tech. Ltd., UK) are assessed which show the current limitations for discriminating between samples. Alternative methods for analysing e-nose data are mentioned and reasons are given why under the stated circumstances no straightforward multivariate statistics is possible. However, despite various difficulties, meaningful results at a group level were obtained and could be correlated with other results obtained using alternative analytical methods. This indicates the positive proof-of-principle character of this project.
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Irfan, Memon. "Coherence analysis : methods, solutions and problems." Thesis, Brunel University, 2008. http://bura.brunel.ac.uk/handle/2438/7141.
Повний текст джерелаАнотація:
A coherence function is a measure of the correlation of two signals and may be used as a measure for functional relationship between brain areas. In studying functional relationships, referenced EEG (REEG) coherence analysis yields important new aspects of brain activities, which complement the data obtained by power spectral analysis. However, REEG-based coherence tends to show a false high value due to volume conduction from un correlated sources (VCUS). Existing signal processing methods address this issue using a Fourier coherence function of scalp Laplacian. Although this method has been proved useful to reveal correlation between EEG signals with minimum VCUS effects, it only provides frequency-domain analysis. Since EEG signals are highly non-stationary, it is more appropriate to use time-frequency methods for coherence analysis of scalp Laplacian. Thus this research applies the wavelet transform on coherence analysis of scalp Laplacian. To verify our technique, already recorded EEG data of event related potentials were obtained from a study of two large groups of alcoholic and abstinent alcoholic subjects, performing visual picture-recognition tasks. The proposed coherence method successfully detected time-frequency correlation between EEG signals with minimum VCUS effects. It showed significant spatial specificity and revealed detailed coherence patterns. Some new important results regarding time-frequency characteristics of VCUS effects on wavelet and short-time Fourier transform (STFT) coherence analysis of REEG signals were deduced. The proposed coherence method was also compared to a conventional wavelet coherence method of REEG signals in the study of coherence difference between coherences of alcoholic and abstinent alcoholic EEG signals. Results of this study provided substantial evidence that VCUS effects are not additive and therefore can not be ignored in comparison of different brain states between groups of subjects.
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Nailon, William H. "Tissue characterisation from intravascular ultrasound using texture analysis." Thesis, University of Edinburgh, 1997. http://hdl.handle.net/1842/1374.
Повний текст джерелаАнотація:
Intravascular ultrasound has, over the past decade, significantly changed the clinical diagnosis and therapeutic strategy of coronary and vascular disease assessment, as it not only allows visualisation of the vessel lumen, but gives a unique view of the pathophysiologic structure of the artery wall. This information is currently unavailable from the universally accepted instrument for artery assessment, angiography, which has on several occasions had its diagnostic accuracy questioned. With intravascular ultrasound, there is the potential to categorise diseased arterial tissue belonging to distinct pathological groups which can ultimately aid in the understanding of individual lesions as well as making a significant contribution to treatment choice and management of cardiac patients. The high resolution image information offered by intravascular ultrasound provides excellent cross-sectional views of coronary artery disease at the level of the disease process itself. This information can be used by the clinician to characterise atherosclerotic plaque composition and vessel wall morphology, both of which are important, in determining the clinical response to the disease condition. However, this visual diagnosis is in general highly subjective due to inter- and intra-observer error. To overcome the short comings inherent in the visual assessment of intravascular ultrasound images, texture analysis was used to assess plaque in regions of interest identified by a clinician. In the two dimensional images produced by intravascular ultrasound, texture is perceived as homogeneous visual patterns representing the surface composition being imaged. Since every tissue sub-group has its own texture, verified from histological analysis, it can be used as a means of characterising it. In this thesis, the findings of applying texture analysis techniques to 30 MHz intravascular ultrasound data, gathered in vitro, to assess its potential in quantitative coronary plaque characterisation are presented. Histo-pathological analysis was used to form a gold standard based upon clot composition, from which the results were verified. The ultimate aim of the work was to determine a reliable protocol based upon textural analysis for assessing plaque composition in vivo. Textural properties, in the form of features, were calculated for regions of interest using first-, second- and higher-order statistics. These were found to be computationally expensive and in certain instances produced duplicate, and hence redundant, information. Feature selection was used to increase the computational efficiency of the algorithm by optimising the feature set. In a further attempt to overcome the weaknesses of the aforementioned techniques, fractal texture analysis was used to obtain textural information on regions of interest. Fractals proved useful in describing the texture of these areas by a single measure. This measure, the fractal dimension, described the degree of irregularity in the surface texture. A new method is proposed for classifying arterial plaque which relies on a combination of the two powerful techniques previously mentioned, statistical and fractal texture analysis. The results presented show the ability of the texture analysis techniques used to discriminate certain tissue sub-groups. Limited success was achieved for the analysis on the atherosclerotic plaque groups studied, however, the approach adopted significantly discriminated the three types of clot composition studied: plasma; white thrombus; and red thrombus.
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Curry, Richard Ian. "Development and modelling of a versatile active micro-electrode array for high density in-vivo and in-vitro neural signal investigation." Thesis, Durham University, 2010. http://etheses.dur.ac.uk/232/.
Повний текст джерелаАнотація:
The electrophysiological observation of neurological cells has allowed much knowledge to be gathered regarding how living organisms are believed to acquire and process sensation. Although much has been learned about neurons in isolation, there is much more to be discovered in how these neurons communicate within large networks. The challenges of measuring neurological networks at the scale, density and chronic level of non invasiveness required to observe neurological processing and decision making are manifold, however methods have been suggested that have allowed small scale networks to be observed using arrays of micro-fabricated electrodes. These arrays transduce ionic perturbations local to the cell membrane in the extracellular fluid into small electrical signals within the metal that may be measured. A device was designed for optimal electrical matching to the electrode interface and maximal signal preservation of the received extracellular neural signals. Design parameters were developed from electrophysiological computer simulations and experimentally obtained empirical models of the electrode-electrolyte interface. From this information, a novel interface based signal filtering method was developed that enabled high density amplifier interface circuitry to be realised. A novel prototype monolithic active electrode was developed using CMOS microfabrication technology. The device uses the top metallization of a selected process to form the electrode substrate and compact amplification circuitry fabricated directly beneath the electrode to amplify and separate the neural signal from the baseline offsets and noise of the electrode interface. The signal is then buffered for high speed sampling and switched signal routing. Prototype 16 and 256 active electrode array with custom support circuitry is presented at the layout stage for a 20 μm diameter 100 μm pitch electrode array. Each device consumes 26.4 μW of power and contributes 4.509 μV (rms) of noise to the received signal over a controlled bandwidth of 10 Hz - 5 kHz. The research has provided a fundamental insight into the challenges of high density neural network observation, both in the passive and the active manner. The thesis concludes that power consumption is the fundamental limiting factor of high density integrated MEA circuitry; low power dissipation being crucial for the existence of the surface adhered cells under measurement. With transistor sizing, noise and signal slewing each being inversely proportional to the dc supply current and the large power requirements of desirable ancillary circuitry such as analogue-to-digital converters, a situation of compromise is approached that must be carefully considered for specific application design.
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Elemento, Elisa. "New gadolinium contrast agents for MRI." Thesis, Durham University, 2008. http://etheses.dur.ac.uk/2266/.
Повний текст джерелаАнотація:
A collaboration between Bracco Imaging S.p.A. and Durham University allowed the work described in this thesis on the design and synthesis of new contrast agents for MRI. Significant enhancements in the relaxivity of contrast agents for MRI can be gained by increasing the complex rotational correlation time ((_TR)). Incorporating a Gd(^111) ion within a ligand structure possessing a suitably large dendritic framework, inspired the first part of this project. Thus, the periphery of a Gd-DOTA derivative was adorned with carbohydrate containing wedges. The symmetry of the mono- aqua tetra-substituted structure places the gadolinium-water vector at the centre of any tumbling motion, allowing a coherent tumbling of the macromolecule and an optimization of its rotational correlation time. The carbohydrates ensured high water solubility and favoured a large second sphere hydration contribution to the relaxivity. An increase in the hydration around the metal centre and a rapid exchange of the water molecules with the bulk solvent can also significantly increase the contrast agent efficacy, by efficiently transmitting the paramagnetic effect from the Gd(^111) to the solvent. In a second part of the work, the development was undertaken of diaqua systems based on the seven-membered heterocycle 6-amino-6-methyl- perhydro-1,4-diazepin (AMPED). The three N-positions were substituted with different phosphinate and carboxylate groups and lanthanide complexes (Eu(^111), Gd(^111), Yb(^111)) prepared and studied by multinuclear NMR methods The alkylation of the amino groups with chiral 1,5-dicarboxylate pendant arms led to complex diastereisomers, possessing different water exchange rates. The individual water exchange rates of each isomer were determined, and differed by a factor of six. Furthermore, the periphery of the isomer possessing a faster water exchange rate was adorned with carbohydrate containing wedges, and the relaxation properties studied.
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Berlinger, S. "Characterisation and functional importance of stress induced signalling following irradiation of prostate cancer cells." Thesis, Queen's University Belfast, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517087.
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Vasu, V. "Biomedical analysis of non-contact signals." Thesis, Queen's University Belfast, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546434.
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Shannon, H. J. "Applications of Room Surface Mapping in Cardial Resynchronisation Therapy." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527894.
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Hanna, G. G. "An evaluation of the role of Positron Emission Tomography/Computed Tomography Imaging in Radiotherapy Target Volume Definition for the treatment of Non-Small Cell Lung Cancer." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527810.
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