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Introduction: Electrical Impedance Tomography (EIT) is an emerging clinical imaging technique. Functional EIT by Evoked Response (fEITER) was developed at the University of Manchester as a high-speed, functional brain imaging device for use at the bedside. This 32-electrode EIT system applies an injection frequency of 10kHz and captures data using a 10ms temporal resolution. This thesis reports on the first volunteer and patient trials undertaken using fEITER for the following conditions: (a) flashing visual sequence - 14 awake volunteers; (b) a voluntary Valsalva manoeuvre (VM) - 15 awake volunteers and (c) during the induction of anaesthesia - 16 elective surgical patients. Aims: The research presented in this thesis was undertaken to differentiate between noise and physiological changes in raw fEITER data signals. Methods: SNR was determined for fEITER. Raw fEITER signals were pre-processed to reduce noise and dominant trends before multiple comparisons between reference and stimulus data were undertaken. Histograms and ROC curves were produced to illustrate the difference between reference and stimulus fEITER data. AUC values for single-subject and pooled ROC curves were calculated to determine whether fEITER data can be reliably differentiated between reference and stimulus conditions. Approximate Entropy (ApEn) was applied to evaluate the regularity of high frequency components within fEITER data for each trial condition. Results: Average SNR values for fEITER acquired using mesh and physical phantoms ranged from 62.94dB to 63.58dB, and 28.29dB to 31.45dB respectively. The following AUC values were acquired: Visual stimulus-frontal electrode pairs and electrode pairs overlying the visual cortex 0.520 and 0.505 respectively; VM: 0.658; and induction of anaesthesia: 0.547. The VM induced the greatest difference between pooled reference and stimulus data. Visual stimulation and induction of anaesthesia data showed poor distinction between pooled reference and stimulus data, although some single subject data did show a significant response. No significant differences were acquired for the comparison of ApEn-reference and ApEn-stimulus data for all trial conditions using a Wilcoxon's signed ranks test (visual stimulus-frontal electrode pairs: upper p = 0.998, visual stimulus-electrode overlying the visual cortex: upper p = 0.980; the VM: upper p = 0.976, and induction of anaesthesia: p = 0.912). Discussion: Although single-subject and pooled fEITER data recorded during the VM produced the greatest differences between reference and stimulus measurements, stimuli such as visual flashes and induction of anaesthesia may not be large enough to induce quantifiable changes between reference and stimulus data recorded from single electrode pairs. Collectively, these results provide little evidence to show that pre-processing of raw fEITER data amplifies features in fEITER waveforms which may be representative of physiological changes induced by an applied stimulus.

Using joint P-wave seismic tomography, receiver functions, and ambient noise we image the magmatic structure beneath Newberry Volcano, located near Bend, Oregon. Use of active source and teleseismic events in a joint tomographic inversion provides the ray crossings necessary to resolve a low velocity body around 4 km depth. Receiver functions show large lateral heterogeneity and are consistent with the location of a low velocity body derived from the tomography but require a larger low velocity anomaly. Ambient noise autocorrelations are used to image a low velocity reflector, located at ~3 km depth, shallower than the imaged low velocity body recovered using tomography and receiver functions. Ultimately, our results reveal a magma chamber at 3-4 km depth beneath Newberry caldera, with an overlying partially molten sill at ~3 km depth. These results show the usefulness of dense seismometer deployments over volcanoes.

Made available in DSpace on 2014-06-11T19:31:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-03-12Bitstream added on 2014-06-13T19:41:52Z : No. of bitstreams: 1 jorge_eg_dr_arafo_parcial.pdf: 228397 bytes, checksum: 7fd4a09ffeb7d4881dcc794270ae8361 (MD5) Bitstreams deleted on 2015-06-25T13:01:04Z: jorge_eg_dr_arafo_parcial.pdf,. Added 1 bitstream(s) on 2015-06-25T13:03:24Z : No. of bitstreams: 1 000718680_20160312.pdf: 206271 bytes, checksum: 74de041b3b2b5333623f8ae23c35b272 (MD5) Bitstreams deleted on 2016-03-14T11:16:20Z: 000718680_20160312.pdf,. Added 1 bitstream(s) on 2016-03-14T11:17:03Z : No. of bitstreams: 1 000718680.pdf: 848471 bytes, checksum: 4aabc45470eacf0e09cd93b63cbe4f22 (MD5) / This study was divided into two sections, having as individual objectives: (1) - to evaluate the healing of periapical lesion after endodontic surgery, through the comparison among area values measured in digitized conventional and digital radiographs, and Cone Beam computed tomography (CBCT) and (2) - to evaluate the periapical bone repair over different periods of time after endodontic surgery by volume measured in CBCTs, and by percentage values calculated from the conventional and digital radiographs, and CBCTs. Material and Methods: Eleven maxillary anterior teeth, with the presence of periapical lesion were submitted to root-end filling. Conventional and digital radiographs, and CBCTs were taken prior to the surgeries and after 48 h (baseline), 4 and 8 months. For each period, the area (mm 2 ) of the periapical lesion observed in the radiographs was compared to those of CBCTs. The volume of the lesions, at all stages of evaluation, was calculated using the software ImageJ. The radiographic images were also imported into the ImageJ software, and the area of periapical radiolucency was measured. The area in the CBCTs was obtained based on the slice with the greater mesio-distal diameter of the lesion. To calculate the volume, the area of the periapical lesion of each CBCT slice, in a parallel orientation to the sagittal axis of the entire lesion, was calculated. Then, the volume of each slice was calculated by multiplying the area by the distance between the tomographic slices. The values of area (mm 2 ), measured in the radiographs and CBCTs, and volume (mm 3 ), measured in the CBCTs, were used to calculate the percentage of periapical bone repair. The data were submitted to Analyses of Variance (α=0.05), followed by T-tests. Results: A significant effect was observed among the Periods of Evaluation... (Complete abstract click electronic access below)

Orientador: Marcelo Gonçalves / Coorientador: Mário Tanomaru Filho / Banca: Celso Luiz Caldeira / Banca: Rubens Spin-Neto / Banca: Juliane Maria Guerreiro Tanomaru / Banca: Renato de Toledo Leonardo / Resumo:Este estudo teve como objetivos: (1) - avaliar a evolução do reparo ósseo periapical de dentes com lesão periapical após cirurgia parendodôntica, por meio da comparação entre áreas mensuradas em radiografias periapicais convencionais digitalizadas, radiografias periapicais digitais e tomografia computadorizada Cone Beam (CBCT) e (2) - avaliar, em diferentes períodos, o reparo periapical após cirurgia parendodôntica, por meio de mensurações volumétricas em CBCT, e porcentuais, em radiografias periapicais convencionais, digitais e CBCTs. Material e Métodos: Foram selecionados dentes anteriores superiores de 11 pacientes, com rarefação óssea periapical visível radiograficamente e indicação de tratamento cirúrgico. Radiografias periapicais, convencionais e digitais, e CBCTs foram realizadas previamente às cirurgias parendodônticas e após os períodos inicial (48 h), 4 e 8 meses. Para cada período, a área (mm 2 ) de rarefação óssea foi mensurada nas radiografias e comparada com à medida tomográfica na região de maior diâmetro da lesão. As imagens radiográficas foram importadas para o programa ImageJ para delimitação do contorno e cálculo da área radiolúcida periapical. A mensuração das áreas na tomografia, por meio do programa ImageJ, foi realizada nos cortes paralelos ao plano mésio-distal de maior diâmetro da lesão. Para o cálculo de volume, as áreas das rarefações ósseas foram mensuradas nos cortes tomográficos paralelos ao plano sagital de toda extensão da lesão periapical. Em seguida, o volume de cada fatia foi calculado multiplicando a área dos cortes pela distância entre eles. Os valores de área (mm 2 ), obtidos nas radiografias e CBCTs, e volume (mm 3 ), obtidos nas CBCTs, foram utilizados para a comparação e análise do porcentual de reparo ósseo periapical. Os dados foram... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study was divided into two sections, having as individual objectives: (1) - to evaluate the healing of periapical lesion after endodontic surgery, through the comparison among area values measured in digitized conventional and digital radiographs, and Cone Beam computed tomography (CBCT) and (2) - to evaluate the periapical bone repair over different periods of time after endodontic surgery by volume measured in CBCTs, and by percentage values calculated from the conventional and digital radiographs, and CBCTs. Material and Methods: Eleven maxillary anterior teeth, with the presence of periapical lesion were submitted to root-end filling. Conventional and digital radiographs, and CBCTs were taken prior to the surgeries and after 48 h (baseline), 4 and 8 months. For each period, the area (mm 2 ) of the periapical lesion observed in the radiographs was compared to those of CBCTs. The volume of the lesions, at all stages of evaluation, was calculated using the software ImageJ. The radiographic images were also imported into the ImageJ software, and the area of periapical radiolucency was measured. The area in the CBCTs was obtained based on the slice with the greater mesio-distal diameter of the lesion. To calculate the volume, the area of the periapical lesion of each CBCT slice, in a parallel orientation to the sagittal axis of the entire lesion, was calculated. Then, the volume of each slice was calculated by multiplying the area by the distance between the tomographic slices. The values of area (mm 2 ), measured in the radiographs and CBCTs, and volume (mm 3 ), measured in the CBCTs, were used to calculate the percentage of periapical bone repair. The data were submitted to Analyses of Variance (α=0.05), followed by T-tests. Results: A significant effect was observed among the Periods of Evaluation... (Complete abstract click electronic access below) / Doutor

Made available in DSpace on 2014-06-12T18:02:18Z (GMT). No. of bitstreams: 2 arquivo5666_1.pdf: 7107729 bytes, checksum: 331daa72875ae82bd7eecdcd35436b14 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2011 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Tomografia por coerência óptica (OCT) é uma técnica de imageamento não invasiva que usa radiação infravermelho para sondar alguns milímetros the profundidade de um alvo com um resolução de poucos micrômetros. Aqui, nós expomos a base teórica para entender a técnica. O texto cobre as duas variedades de OCT domínio temporal e domínio da frequência e descreve três aplicações da técnica em odontologia: a) Um na avalição the propagação rachaduras em polímeros reforçado com fibra usado em restauração dental; b) O imageamento da sobra de dentina e cavidade pulpar após excavação da dentina, com o propósito de medir a espessura da dentina, e c) uma avaliação clínica da integridade de restaurações dentais. Em todas essa aplicações, OCT gerou imagens marcantes e forneceu informações semiquatitativas sobre a estrura dentária. Com o objetivo de desenvolver um sistema de tomografia óptica integrada em um chip. Nós expomos a base teórica da plataforma de fotônica integrada. Após uma revisão literária, nós descobrimos que não existe espectrômetro integrado com a especificações necessárias para uso em OCT. Nós, então, desenvolvemos um espectrômetro com a características necessárias. Isso foi possível devido a uma nova arquitetura de espectrômetro baseada na combinação de um ressoador em anel e um espectrômetro de grade de difração

Cachexia occurs commonly and is a significant cause of morbidity and up to 20% mortality in patients with cancer. Loss of muscle mass occurs as part of the cachexia wasting process and low muscle mass is a key element of the most recent consensus cachexia definition. Measuring muscle mass and changes in skeletal muscle is important to phenotype cachectic individuals and to monitor response to anti-cachectic treatments. This thesis investigates minimally invasive or burdensome methods of measuring muscle mass and muscle protein kinetics for use in a clinical or research setting. Quantification of muscle area on routine diagnostic cross-sectional imaging offers a novel and relatively non-invasive method of assessing both regional (and by extrapolation) whole body muscle mass. The need for such a direct measurement of muscle mass was demonstrated by showing that simple anthropometric formulae are unable to predict muscularity accurately (within 25%) when compared with estimates derived from patients diagnostic CT scans. It may be that qualitative changes in muscle may be more sensitive indices of the wasting process rather than qualitative change. Myosteatosis (infiltration of muscle by fat) is known to occur in both cachexia and age related sarcopenia and can be quantified using the Hounsfield spectrum observed on routine diagnostic CT scans. However, not all patients undergo routine CT scanning and there is a need for a biomarker derived from urine or blood. Consequently, cross sectional imaging was used to phenotype patients in a proteomic analysis of urine with the aim of identifying protein or peptide biomarkers associated with myosteatosis in cancer cachexia. A biomarker model for myosteatosis was developed with good sensitivity (97%) but poor specificity (71%). Many of the potential protein / peptide markers identified had poor associations with known mechanisms of muscle wasting and further study of the identified peptides in an extended cohort would help determine the validity of the present findings. However, two proteins with potential roles in muscle repair or neuromuscular function (Agarin and Cathepsin C) were identified and these may warrant targeted investigation with evaluation against sequential measures of muscle mass to determine their value in defining muscle loss over time. As different regional measures of muscularity are available, trunk (L3 CT) and limb muscle (quadriceps MRI) cross sectional measurements were compared with functional assessments to determine the optimal site for measurement. Neither measure proved superior to the other but appeared to reflect different aspects of function. Quadriceps muscle area correlated with quadriceps strength and power whilst truncal muscle area correlated more with complex movements such as the timed-up-and-go test. Changes in regional muscle area in patients with upper gastrointestinal cancer were assessed by upper and lower limb MRI before and after surgery and by L3 CT cross sectional area before and after neo-adjuvant chemotherapy. No change in limb muscularity was seen at 220 days post operatively compared with pre-op measurements. During neo-adjuvant chemotherapy a significant loss of truncal muscle occurred in the absence of significant weight loss suggesting that sequential cross sectional imaging is capable of detecting changes in body composition that may not be apparent clinically. Whilst sequential scans may document changes in muscularity, they do not describe the underlying levels of muscle synthesis or degradation that may regulate muscle volume. The final section of this thesis describes the development of a novel tracer method to measure skeletal muscle synthesis and its application in a study of patients with cancer and healthy volunteers. This novel method was able to measure skeletal muscle fractional synthetic rate (FSR) over a longer time-period than previous methods (weeks rather than hours) and reduced the burden on the patient by the use of a single oral tracer dose and single muscle biopsy. Comparison of synthesis rates in quadriceps and rectus abdominis showed higher rates in quadriceps, 0.067% per hour vs 0.058% per hour respectively. Despite a net loss of muscle as measured by serial CT scans, skeletal muscle FSR appeared to be marginally increased in weight losing patients with cancer compared with weight stable patients and healthy controls. When FSR was combined with measures of muscle mass it was demonstrated that only small differences between synthesis and degradation are required to see the levels of muscle wasting seen in patients with cancer. In summary, routine cross sectional imaging provides a useful and unique measure of muscularity that is associated with function in patients with cancer Sequential scans can provide additional information about changes in body composition even in the absence of weight loss. There are significant regional variations in both muscle wasting and skeletal muscle fractional synthetic rate. The combination of sequential estimates of muscle mass from diagnostic CT scans along with estimates of FSR allow assessment of the contribution of altered synthesis and degradation to muscle loss. In patients with upper GI cancer it would appear that increased degradation may be more important that altered synthesis. The relative change in either process to account for absolute loss of muscle mass is small. Such findings have implications for the targeted therapy of muscle wasting in cancer patients.

Electrical impedance tomography (EIT) is an imaging modality with many possible practical applications. It is mainly used for geophysical applications, for which it is called electrical resistivity tomography. There have also been many proposed medical applications such as respiratory monitoring and breast tumour screening. Although there have been many uniqueness and stability results published over the last few decades, most of the results are in the context of the theoretical continuous problem. In practice however, we almost always have to solve a discretised problem for which very few theoretical results exist. In this thesis we aim to bridge the gap between the continuous and discrete problems. The first problem we solve is the three-dimensional triangulation problem of uniquely embedding a tetrahedral mesh in R3. We parameterise the problem in terms of dihedral angles and we provide a constructive procedure for identifying the independent angles and the independent set of constraints that the dependent angles must satisfy. We then use the implicit function theorem to prove that the embedding is locally unique. We also present a numerical example to illustrate that the result works in practice. Without the understanding of the geometric constraints involved in embedding a three-dimensional triangulation, we cannot solve more complex problems involving embeddings of finite element meshes. We next investigate the discrete EIT problem for anisotropic conductivity. It is well known that the entries of the finite element system matrix for piecewise linear potential and piecewise constant conductivity are equivalent to conductance values of resistors defined on the edges of the finite element mesh. We attempt to tackle the problem of embedding a finite element mesh in R3, such that it is consistent with some known edge conductance values. It is a well known result that for the anisotropic conductivity problem, the boundary data is invariant under diffeomorphisms that fix the boundary. Before investigating this effect on the discrete case, we define the linear map from conductivities to edge conductances and investigate the injectivity of this map for a simplistic example. This provides an illustrative example of how a poor choice of finite element mesh can result in a non-unique solution to the discrete inverse problem of EIT. We then extend the investigation to finding interior vertex positions and conductivity distributions that are consistent with the known edge conductances. The results show that if the total number of interior vertex coordinates and anisotropic conductivity variables is larger than the number of edges in the mesh, then there exist discrete diffeomorphisms that perturb the vertices and conductivities such that no change in the edge conductances is observed. We also show that the non-uniqueness caused by the non-injectivity of the linear map has a larger effect than the non-uniqueness caused by diffeomorphism invariance.

Electrical impedance tomography is an imaging method with applications to geophysics and medical imaging. A new approximation is presented based on Nachman's 2-dimensional construction for closed domains. It improves upon existing approximations by extending the range of application from resolving 2 times the surface conductivity to imaging perfect conductors and insulators. With perfect knowledge of boundary data, this approximation exactly resolves a single conductive disc embedded in a homogenous domain. The problem, however, is ill-posed, and imaging performance degrades quickly as the distance from the boundary increases. The key to the approximation lies in (a) approximating Fadeev's Green's function (b) pre-processing measured voltages based on a boundary-integral equation (c) solving a linearized inverse problem (d) solving a d-bar equation, and (e) scaling the resulting image based on analytical results for a disc. In the development of the approximation, a new formula for Fadeev's Green's function is presented in terms of the Exponential Integral function. Also, new comparisons are made between reconstructions with and without solving the d-bar equation, showing that the added computational expense of solving the d-bar equation is not justified for radial problems. There is no discernible improvement in image quality. As a result, the approximation converts the inverse conductivity problem into a novel one-step linear problem with pre-conditioning of boundary data and scaling of the resulting image. Several extensions to this work are possible. The approximation is implemented for a circular domain with unit conductivity near the boundary, and extensions to other domains, bounded and unbounded should be possible, with non-constant conductivity near the boundary requiring further approximation. Ultimately, further research is required to ascertain whether it is possible to extend these techniques to imaging problems in three dimensions. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

This thesis reports on the research carried out in the area of Microwave Tomography (MWT) where the study aims to develop inversion algorithms to obtain cheap and stable solutions of MWT inverse scattering problems which are mathematically formulated as nonlinear ill posed problems. The study develops two algorithms namely Inexact Newton Backtracking Method (INBM) and Newton Iterative-Conjugate Gradient on Normal Equation (NI-CGNE) which are based on Newton method. These algorithms apply implicit solutions of the Newton equations with unspecific manner functioning as the regularized step size of the Newton iterative. The two developed methods were tested by the use of numerical examples and experimental data gained by the MWT system of the University of Manchester. The numerical experiments were done on samples with dielectric contrast objects containing different kinds of materials and lossy materials. Meanwhile, the quality of the methods is evaluated by comparingthem with the Levenberg Marquardt method (LM). Under the natural assumption that the INBM is a regularized method and the CGNE is a semi regularized method, the results of experiments show that INBM and NI-CGNE improve the speed, the spatial resolutions and the quality of direct regularization method by means of the LM method. The experiments also show that the developed algorithms are more flexible to theeffect of noise and lossy materials compared with the LM algorithm.