Dissertations / Theses on the topic 'Coefficient of weight'

Sorting out data into partitions is increasing becoming complex as the constituents of data is growing outward everyday. Mixed data comprises continuous, categorical, directional functional and other types of variables. Clustering mixed data is based on special dissimilarities of the variables. Some data types may influence the clustering solution. Assigning appropriate weight to the functional data may improve the performance of the clustering algorithm. In this paper we use the extension of the Gower coefficient with judciously chosen weight for the L2 to cluster mixed data.The benefits of weighting are demonstrated both in in applications to the Buoy data set as well simulation studies. Our studies show that clustering algorithms with application of proper weight give superior recovery level when a set of data with mixed continuous, categorical directional and functional attributes is clustered. We discuss open problems for future research in clustering mixed data.

With the development of intelligent era, speech recognition has been a hottopic. Although many automatic speech recognition(ASR) tools have beenput into the market, a considerable number of them do not support Swedishbecause of its small number. In this project, a Swedish ASR model basedon Hidden Markov Model and Gaussian Mixture Models is established usingKaldi which aims to help ICA Banken complete the classification of aftersalesvoice calls. A variety of model patterns have been explored, whichhave different phoneme combination methods and eigenvalue extraction andprocessing methods. Word Error Rate and Real Time Factor are selectedas evaluation criteria to compare the recognition accuracy and speed ofthe models. As far as large vocabulary continuous speech recognition isconcerned, triphone is much better than monophone. Adding feature transformationwill further improve the speed of accuracy. The combination oflinear discriminant analysis, maximum likelihood linear transformand speakeradaptive training obtains the best performance in this implementation. Fordifferent feature extraction methods, mel-frequency cepstral coefficient ismore conducive to obtain higher accuracy, while perceptual linear predictivetends to improve the overall speed.<br>Det existerar flera lösningar för automatisk transkribering på marknaden, menen stor del av dem stödjer inte svenska på grund utav det relativt få antalettalare. I det här projektet så skapades automatisk transkribering för svenskamed Hidden Markov models och Gaussian mixture models genom att användaKaldi. Detta för att kunna möjliggöra för ICABanken att klassificera samtal tillsin kundtjänst. En mängd av modellvariationer med olika fonemkombinationsmetoder,egenvärdesberäkning och databearbetningsmetoder har utforskats.Word error rate och real time factor är valda som utvärderingskriterier föratt jämföra precisionen och hastigheten mellan modellerna. När det kommertill kontinuerlig transkribering för ett stort ordförråd så resulterar triphonei mycket bättre prestanda än monophone. Med hjälp utav transformationerså förbättras både precisionen och hastigheten. Kombinationen av lineardiscriminatn analysis, maximum likelihood linear transformering och speakeradaptive träning resulterar i den bästa prestandan i denna implementation.För olika egenskapsextraktioner så bidrar mel-frequency cepstral koefficiententill en bättre precision medan perceptual linear predictive tenderar att ökahastigheten.

Master`s thesis is divided in to two parts, practical and theoretical. In theoretical part are listed basic information’s about light weight concrete, special emphasis are given to characteristic and practical application of compact light weight concrete with Liapor aggregates. In this study is described influence of high temperature on concrete structure and chemical, mechanical and physical changes, which take place during exposal to high temperatures. Further is evaluated surface permeability of concrete and addition of polypropylene fibres to concretes resistive to high temperatures. The practical part deals with design, production and testing of cement based concrete with use of different aggregates (light weight aggregates Liapor, basalt). The properties and use for applications in high temperatures is also mentioned. The influence of high temperature on strength, absorption, thermal conductivity, changes of surface permeability and degradation of testing specimens due to heat loads according to normative heat curve (ISO 834). For better transparency are experimental tests divided in to five phases and the measured values are evaluated on the end of each phase. In conclusion are resumed all knowledge’s obtained by testing and evaluated the most suitable formulation. The approach for further research is also mentioned.

L'etude d'un melange ternaire de polymeres en solution semidiluee presente deux modes de relaxation. Mise en evidence par diffusion de lumiere quasi-elastique de deux processus de diffusion: le premier, lent, correspond au mouvement relatif des deux polymeres; le second, rapide, correspond au mouvement cooperatif du reseau physique forme par les deux polymeres

Cancer is one of the major causes of worldwide mortality. Imaging plays a vital role in the staging, follow-up, and evaluation of therapeutic response in cancer patients. Whole-body (WB) magnetic resonance imaging (MRI), as a non-ionizing imaging technique, is a promising procedure to assess tumor spreading in a single examination. New MRI technological developments now enable the application of diffusion-weighted imaging (DWI) of the entire body. DWI reflects the random motion of water molecules and provides functional information of body tissues. DWI can be quantified with the use of the apparent diffusion coefficient (ADC). The aim of this dissertation was to demonstrate the value of WB MRI including DWI in cancer patients. WB MRI including DWI, 18F-NaF PET/CT, and bone scintigraphy was performed on 49 patients with newly diagnosed, high-risk prostate cancer, for the purpose of detecting bone metastases. WB DWI showed higher specificity, but lower sensitivity compared to 18F-NaF PET/CT. In addition, WB MRI including DWI, and CT of the chest and abdomen was performed in 23 patients with malignant melanoma. We concluded that WB MRI could not completely supplant CT for the staging of malignant melanoma, especially with respect to the detection of lesions in the chest region. In this study, WB MRI and DWI were able to detect more bone lesions compared to CT, and showed several lesions outside the CT field of view, reinforcing the advantage of whole-body examination. WB MRI, including DWI, was performed in 71 patients with testicular cancer. This modality demonstrated its feasibility for use in the follow-up of such patients. WB MRI, including DWI, and 18F-FDG PET-CT, were carried out in 50 patients with malignant lymphoma. Both these imaging modalities proved to be promising approaches for predicting clinical outcomes and discriminating between different subtypes of lymphomas. In conclusion, WB MRI, including DWI, is an evolving technique that is continuing to undergo technical refinement. Standardization of image acquisition and analysis will be invaluable, allowing for more accurate comparison between studies, and widespread application of this technique in clinical practice. Both WB MRI, including DWI and PET/CT, have their particular strengths and weaknesses in the evaluation of metastatic disease. DWI and PET/CT are different functional techniques, so that combinations of these techniques may provide complementary and more comprehensive information of tumor tissue.

In this thesis, Finite Volume Weighted Essentially Non-Oscillatory (FV-WENO) codes for one and two-dimensional discretised Euler equations are developed. The construction and application of the FV-WENO scheme and codes will be described. Also the effects of the grid coefficients as well as the effect of the Gaussian Quadrature on the solution have been tested and discussed. WENO schemes are high order accurate schemes designed for problems with piecewise smooth solutions containing discontinuities. The key idea lies at the high approximation level, where a convex combination of all the candidate stencils is used with certain weights. Those weights are used to eliminate the stencils, which contain discontinuity. WENO schemes have been quite successful in applications, especially for problems containing both shocks and complicated smooth solution structures. The applications tested in this thesis are the Diverging Nozzle, Shock Vortex Interaction, Supersonic Channel Flow, Flow over Bump, and supersonic Staggered Wedge Cascade. The numerical solutions for the diverging nozzle and the supersonic channel flow are compared with the analytical solutions. The results for the shock vortex interaction are compared with the Roe scheme results. The results for the bump flow and the supersonic staggered cascade are compared with results from literature.

Radiological imaging already has a key role in the detection and management of patients with metastatic colorectal cancer (mCRC). With the evolution of personalised medicine there is a need for non-invasive imaging biomarkers that can detect early tumour response to targeted therapies. Translation from bench to bedside requires a multicentre approach that follows an agreed development roadmap to ensure that the proposed biomarker is precise (reproducible/ repeatable) and accurate in its characterisation of a meaningful physiological, pathological or post treatment response. The following thesis (organized in the alternative format with experimental studies written as individual complete manuscripts) investigates methods to improve precision and accuracy of the Apparent Diffusion Coefficient (ADC), a proposed quantitative imaging biomarker with a potential role in characterisation of post treatment responses in mCRC. The first objective was to establish baseline multicentre reproducibility (n=20) for ADC. A change in ADC greater than 21.1% was required to determine a post treatment response. Using a statistical error model, the dominating factors that influenced reproducibility were motion artefact and tumour volume. In the second study these factors were addressed using a single centre cohort with pre and post treatment data. Correcting for errors due to motion and tumour volume improved sensitivity from 30.3% to 1.7%, so a post treatment response was detected in 6/12 tumours compared to 0/12 using the baseline approach. In the third study, motion correction was implemented and the statistical error model was applied successfully to a multicentre cohort of 15 patients (1.9% sensitivity). The results of this thesis highlights that with careful consideration and correction of factors that negatively influence sensitivity, ADC is a potential imaging biomarker for use in post treatment response for patients with mCRC.

La tecnica di Diffusion Weighted Imaging (DWI) si basa sullo studio del moto diffusivo delle molecole d’acqua nei tessuti biologici ed è in grado di fornire informazioni sulla struttura dei tessuti e sulla presenza di eventuali alterazioni patologiche. Il più recente sviluppo della DWI è rappresentato dal Diffusion Tensor Imaging (DTI), tecnica che permette di determinare non solo l’entità, ma anche le direzioni principali della diffusione. Negli ultimi anni, grazie ai progressi nella tecnica di risonanza magnetica, l’imaging di diffusione è stato anche applicato ad altri distretti anatomici tra cui quello renale, per sfruttarne le potenzialità diagnostiche. Tuttavia, pochi sono ancora gli studi relativi all’applicazione delle metodiche di diffusione per la valutazione della malattia policistica renale autosomica dominante (ADPKD). ADPKD è una delle malattie ereditarie più comuni ed è la principale causa genetica di insufficienza renale dell’adulto. La caratteristica principale consiste nella formazione di cisti in entrambi i reni, che progressivamente aumentano in numero e dimensioni fino a causare la perdita della funzionalità renale nella metà circa dei pazienti. Ad oggi non sono disponibili terapie capaci di arrestare o rallentare l’evoluzione di ADPKD; è possibile controllare le complicanze per evitare che costituiscano componenti peggiorative. Il lavoro di tesi nasce dalla volontà di indagare se la tecnica dell’imaging di diffusione possa essere utile per fornire informazioni sullo stato della malattia e sul suo grado di avanzamento. L’analisi di studio è concentrata sul calcolo del coefficiente di diffusione apparente (ADC), derivato dalle immagini DWI e valutato nella regione della midollare. L’obiettivo di questo lavoro è verificare se tale valore di ADC sia in grado di caratterizzare la malattia policistica renale e possa essere utilizzato in ambito clinico-diagnostico come indicatore prognostico nella progressione di questa patologia.

<p>The Kappa coefficient is widely used in assessing categorical agreement between two raters or two methods. It can also be extended to more than two raters (methods).  When using Kappa, the shortcomings of this coefficient should be not neglected.  Bias and prevalence effects lead to paradoxes of Kappa. These problems can be avoided by using some other indexes together, but the solutions of the Kappa problems are not satisfactory. This paper gives a critical survey concerning the Kappa coefficient and gives a real life example. A useful alternative statistical approach, the Rank-invariant method is also introduced, and applied to analyze the disagreement between two raters.</p>

Ce travail de thèse consiste en l’étude de la prédiction du handicap à l’aide de la séquence IRM pondérée en diffusion (DWI). Dans un premier temps, nous nous sommes intéressés à la prédiction du volume final de l’infarctus grâce à un algorithme d’analyse d’images basé sur le traitement de la cartographie du coefficient apparent de diffusion (ADC) sur 216 patients (<6H). La croissance prédite et réelle de l’infarctus étaient significativement corrélées (0,478, p<0,0001). La méthode distinguait les « infarctus stables » des « infarctus en évolution » avec une sensibilité de 77 % et une spécificité de 80 %. La relation croissance prédite - croissance réelle était modifiée par la recanalisation artérielle et la glycémie, deux facteurs connus pour influer sur le devenir de la pénombre. Dans un deuxième temps, nous avons cherché à prédire directement le handicap des patients (n=79) à 3 mois en combinant les valeurs d’ADC dans les 6 premières heures (H6) et le lendemain (J1) à une information de localisation anatomique (les structures motrices). Les valeurs d’ADC étaient significativement plus basses chez les patients dépendants (score de Rankin 3-5) dans le faisceau cortico-spinal (FCS) et le putamen à H6 et à J1 ainsi que dans le cortex moteur primaire. A l’échelle individuelle, le putamen à H6 et le FCS à J1 étaient les régions qui permettaient la meilleure classification des patients selon le pronostic (74% et 75% de précision respectivement). Ce travail souligne le rôle des voies de substance blanche par rapport au cortex dans le pronostic et l’importance de la localisation de la lésion comme facteur essentiel dans la prédiction du handicap des AIC carotidiens.

La thèse porte sur la caractérisation expérimentale des pertes singulières dans les matériaux magnétiques au sein d’actionneurs électromécaniques conçus pour le développement du programme « avion plus électrique », où la maîtrise des pertes d’énergie est un enjeu absolument majeur. Ce programme, de portée mondiale, vise, entre autre, à remplacer, dans l’avion, les actionneurs hydrauliques par des actionneurs électromécaniques, quand c’est possible.Par pertes singulières on entend toutes les pertes liées aux contraintes magnéto-mécano-thermiques liées d’une part à la mise en œuvre (découpe, assemblage contraint, isolation, traitement thermique...) des matériaux et d’autre part aux conditions réelles de fonctionnement (champ tournant, haute fréquence, saturations locales...) au sein des machines électriques (HV/HF), et qui sont très difficiles à estimer précisément de façon analytique ou via les dispositifs conventionnels de tests. Ces sollicitations influencent les caractéristiques de tôles qui peuvent s’éloigner significativement des données du fabricant (donc fausser le calcul des performances).Au début de cette thèse on s’est focalisé sur le montage d’un banc d’essai évolutif équipé de moyens de mesure directe du couple et d’une machine d’entraînement (8 ktr/min ; 42 kW) tarée par nos soins. Sur cette dernière une longue campagne d’essais a été menée pour isoler les différentes composantes de pertes, dont, par exemple, les pertes mécaniques (par frottement dans les roulements + aérodynamiques) qui ont été quantifiées via un rotor neutre. Les pertes dans les aimants sont indissociables des pertes fer, donc, elles ont été estimées par le biais d’une modélisation par éléments finis tridimensionnelle. Les pertes dans la frette de maintien sont nulles du fait qu’elle est isolante (thermo-rétractable). Le bobinage utilisé dans ce moteur est très particulier, à barres massives (remplissage de cuivre dans l’encoche jusqu’à 90%), développé dans notre laboratoire IES. Les pertes atypiques au sein de ce bobinage spécial ont été profondément abordées dans ces travaux (effet de refoulement de courants, pertes aux extrémités de la machine...).Dans la dernière partie de cette thèse, nous avons exploré le fonctionnement des machines synchrones à aimants à haute fréquence afin d’accroître la densité de puissance de nos moteurs (pour franchir la barre de 2.5 kW/kg). Pour ce faire, après une étude détaillée, nous avons proposé en premier lieu un prototype avec des matériaux standard (stator FeCo Vacodur49 0.2mm, rotor FeSi, aimants NdFeB nuance N35EH, bobinage à barres cuivre) fonctionnant à 1666 Hz, tournant à 5000 tr/min, avec une densité de puissance de 4.5 kW/kg et un rendement de 94%. En second lieu, nous avons proposé un deuxième prototype de rendement plus faible (93%) mais qui a une densité de puissance proche de 6 kW/kg avec un rotor sans fer et un bobinage en Aluminium.Avant le montage final de ce prototype modulaire, nous avons effectué des mesures de pertes magnétiques, en conditions réelles de fonctionnement d’un moteur électrique, sur une multitude de tôles FeSi et FeCo (Vacodur49, NO20, M270-35A) avec la variation de différents procédés de fabrication: isolation (vernis thermo-collant « back-lack », vernis C5), découpe (laser, électroérosion) et traitement thermique. Pareillement, toutes les pertes mises en jeu ont été séparées (mécaniques, par courants induits dans les viroles...) pour pouvoir remonter aux pertes magnétiques et, donc, enfin, quantifier empiriquement le coefficient de majoration de pertes fer<br>The main aim of this thesis was to study and experimentally assess the additional iron losses in the stator (electrical lamination steel) of high performance permanent magnet synchronous machines (PMSM) designed for aircraft applications, in relation with the “more-electric-aircraft” project. This international program consists of gradually introducing electrical systems to replace onboard hydraulic and pneumatic systems, for example to power the landing gear wheels (Electric Green Taxiing System)…The extra iron losses are caused by manufacturing processes (cutting, sticking, insulation, stacking, pressing, shrink-fitting, thermal treatment …) and the real conditions of use of electrical motor (namely: rotational flux, saturation, high frequency…). Indeed, the mechanical and thermal stresses during the manufacturing steps can deteriorate the magnetic properties of the material and significantly increase the iron losses. These aspects are difficult to accurately evaluate by analytical models or standard measurements (Epstein frame…) and require experimental assessment to precisely calculate the motor efficiency.First of all, we started by developing a test bench equipped with drive motor: PMSM 8000 RPM ; 42 kW. For accurate assessment, the losses in this machine are separated on the test bench, for example, the mechanical losses (bearings loss &amp; windage loss) have been measured at different speed with a non-magnetic rotor. Rotor magnets eddy-current losses cannot be isolated from iron losses, for this reason they have been calculated using a 3D finite element model. To limit rotor loss we then used a non-conductive retaining sleeve (heat shrink sleeve). In the winding, we used bar-wound conductors, which is an original winding technology developed in our laboratory, and whose advantage among others is the unusual copper fill factor that reaches almost 90%.Subsequently, we explored the high frequency machines (&gt;1 kHz) in order to increase the power-to-weight ratio (cross the threshold of 2.5 kW/kg). We proposed, the following to the analytical and finite element study, a first conventional prototype with a power-to-weight ratio equal to 4.5 kW/kg with: FeCo stator (Vacodur49 0.2 mm), FeSi rotor and NdFeB magnets (N35EH), operated at 1666 Hz, 5000 RPM and 94% efficiency at full load. A second motor had been also proposed with both rotor and winding in aluminum, in this case the power-to-weight ratio reaches around 6 kW with, however, less efficiency (93%).Finally, this HF motor was tested, at no load, on the aforementioned test bench. The experiments were carried out on a multitude of FeCo and FeSi stator core samples coming from different manufacturing processes (insulation: bonding varnish and C-5 varnish; cutting: laser and EDM “Electrical Discharge Machining”; thermal treatment) in real operating conditions of a high frequency PM machine in order to experimentally obtain the famous “additional coefficient” of iron losses (Kadd)

This thesis focuses on the measurement of diffusion coefficient of dialysis membrane. The first part describes possibilities of membrane modelling. Basic models, which allow us to determine the basic characteristics of dialysis membranes like permeability and diffusion coefficient, are described. Next chapter deals with basic types and properties of membranes. The main part focuses on making the experimental installation, which is used to simulate permeance of contrast agent, used in DCE-MRI, through dialysis membrane. The last theoretical chapter describes calculations used to estimate diffusion coefficient. Practical part of this thesis uses a designed experimental installation for estimation of diffusion coefficient for two contrast agents Gadovist® and Multihance®.

Neste trabalho são obtidos os coeficientes do modelo da Soma-Ponderada-dos-gases-cinza (WSGG) a partir do banco de dados HITEMP 2010, permitindo o uso do modelo com os dados mais precisos disponíveis atualmente. Neste trabalho também se faz uma comparação dos valores de emitância total obtidos a partir do modelo WSGG com valores benchmark, obtidos nesse trabalho, mostrando uma excelente concordância. Com os coeficientes obtidos, problemas unidimensionais de transferência de calor radiante são resolvidos de modo a comparar a solução obtida pelo modelo WSGG com a solução obtida pela integração LBL (solução benchmark). Nas comparações, diferentes perfis de temperatura, comprimentos de trajeto, gradientes de temperatura e concentrações de espécies são utilizadas. Em todos os casos é possível verificar uma boa concordância entre os resultados WSGG e LBL. Para comparações com perfil de temperatura parabólico, verifica-se erros locais abaixo de 8%. Para perfis de temperatura cossenoidais, é possível observar erros de até 18% para alguns casos, porém com erros médios menores que 1,6%.<br>In this work the coefficients for the Weighted Sum-of-Gray-Gases model (WSGG) are determined from HITEMP 2010 database, allowing the use of the model with the most accurate data available nowadays. This study also makes a comparison of the total emittance values obtained from the model with benchmark values, obtained in this work, showing an excellent agreement. With the obtained coefficients, one-dimensional radiant heat transfer problems are solved in order to compare the solution obtained by the WSGG model with the solution obtained by the LBL integration (benchmark solution). In the comparisons, different temperature profiles, path lengths, temperature gradients and species concentrations are used. In all cases it is possible to verify the good agreement of the WSGG and LBL results. For comparisons with parabolic temperature profile, the local error is below 8%. For cosine temperature profile, the local error is about 18% for some cases, but with average errors less than 1,6%.

La variabilidad de peso vivo cobra especial relevancia en la porcicultura moderna donde la importancia de la integridad y homogeneidad del lote resulta crucial para no interrumpir los flujos de producción. Una de las consecuencias negativas de obviar la variabilidad de peso vivo es una mayor depreciación de las canales en matadero, obteniéndose un menor rendimiento económico por cerdo engordado. Por ello, el objetivo general de la presente tesis doctoral fue el de conocer algunos factores relacionados con la variabilidad de peso vivo, haciendo especial hincapié en sus efectos al final del ciclo. La variabilidad de peso vivo tiene un origen multifactorial, por lo que muchos factores deben ser tenidos en cuenta. Poder identificar estos factores resulta importante para poder tomar medidas correctoras con prontitud para poder paliar los efectos adversos en matadero. Así, en el Capítulo 4, se identificaron varios factores directamente relacionados con un menor crecimiento de los cerdos a lo largo de todo el ciclo productivo. Estos cerdos con menores tasas de crecimiento, son responsables de un aumento de la variabilidad, y, mediante una metodología de corte epidemiológico se jerarquizaron los principales factores relacionados con este menor crecimiento (peso vivo al nacimiento, días de lactación, peso vivo al destete y ganancia media diaria). El estudio, además, se realizó en tres poblaciones de cerdos independientes, obteniéndose similares resultados. De entre los factores más relevantes que inciden directamente en el arranque de los lechones en las primeras fases del ciclo productivo, destacan los días de lactación. Es posible que la duración de la lactación, además de afectar el crecimiento de los distintos cerdos de la camada (y por tanto su variabilidad) tenga un efecto que perdure hasta el sacrificio. Así, en el Capítulo 5 se confirmó que, dependiendo del manejo utilizado en las granjas, la duración de la lactación tiene un efecto importante en la variabilidad de peso vivo de los cerdos desde el destete hasta el final del ciclo. Una lactación de 26 días, así como un peso al destete de 7 kg serían los valores recomendados para optimizar el peso vivo al final del ciclo. Finalmente, si bien la variabilidad de peso vivo no puede ser erradicada en su totalidad, sí se puede intervenir para reducirla mediante estrategias de carácter práctico y que no impliquen complicaciones de tipo logístico o cambios drásticos en el sistema de producción. En este sentido, un uso correcto de los comederos en cuanto al número de animales por boca, así como una segregación de los animales en función de su peso, combinada con una alimentación diferencial sobre los cerdos de menor peso vivo fue explorado en el Capítulo 6. Los resultados en relación a los comederos mostraron un incremento del peso vivo (80,2 vs. 82,1 kg para 5,5 y 2,2 cerdos/boca respectivamente; P = 0,011) y una tendencia a disminuir el CV (10,53 vs. 8,86% para 5,5 y 2,2 cerdos/boca respectivamente; P = 0,150) al final del ciclo. En cuanto al manejo de la alimentación, los resultados fueron favorables a la alimentación ‘específica, Sp.’ comparado con el ‘estándar, Std. ', con mejores valores de peso vivo (96,2 vs. 94,1 kg para Sp. y Std. respectivamente; P <0,001) y CV (9,7 vs. 11,3% para Sp. y Std. respectivamente; P = 0,005) al sacrificio.<br>Live weight variability is particularly important in modern pig production, because the importance of the integrity and homogeneity of the batch is crucial in order not to interrupt production flows. One of the negative consequences of not considering the variability of live weight is a greater depreciation of the carcasses at the slaughterhouse, obtaining a lower economic income per fattened pig. Regarding this problem, the general objective of this PhD thesis was to know some factors related to the variability of live weight, with special emphasis on its effects at the end of the cycle. The variability of live weight has a marked multifactorial origin; therefore, many factors should be considered. Being able to identify these factors is important to take corrective measures promptly to control or mitigate the adverse effects in slaughterhouse. Thus, in Chapter 4, several factors directly related to lower growth of pigs throughout the productive cycle were identified. These pigs with lower growth rates are responsible for an increase in variability, and, by an epidemiological approach, the main factors related to this lower growth (birth body weight, days of lactation, weaning body weight and average daily gain at different productive phases) were ranked. The study was also conducted in three independent pig populations, obtaining similar results. Among the most relevant factors that directly affect the startup of piglets in the early stages of the production cycle, highlight the lactation length. It is possible that the duration of lactation, in addition to affecting the growth of the different pigs of the litter (and therefore its variability) has an effect that lasts in the time until slaughter. Lactation length was studied in Chapter 5 and, in fact, it was confirmed that depending on the general management used in the farms, the duration of lactation has a significant effect beyond weaning until the end of the cycle in the body weight variability of the pigs. Then, lactation length around 26 days and weaning weight close to 7 kg would be the recommended values to optimize the body weight at the end of the cycle. Finally, although the variability of live weight cannot be eradicated in its entirety, it can be intervened to reduce it, and practical strategies that do not imply logistical issues or even drastic changes in the production system, would be appropriate. In this sense, a correct use of the feeders in terms of the number of animals per feeder space, as well as a segregation of the animals according to their live weight, combined with a differential feeding on the pigs of lower live weight was explored in Chapter 6. Thus, the results in relation to the feeders showed an increase in live weight (80.2 vs. 82.1 kg for 5.5 and 2.2 pigs / space respectively, P = 0.011) and a tendency to decrease the CV (10.53 vs. 8.86% for 5.5 and 2.2 pigs / space respectively, P = 0.150) at the end of the cycle. Regarding the feeding management, the results were favorable to the 'specific feed, Sp.' compared to the 'standard, Std.', with better live weight values (96.2 vs. 94.1 kg for Sp. and Std., respectively, P <0.001) and CV (9.7 vs. 11.3% for Sp and Std. respectively, P = 0.005) at slaughter.

Актуальність теми. Зважаючи на політику закладену в стратегії розвитку електроенергетичного сектору України, а саме інтеграцію до ENTSO-E, виникає значна кількість питань, які мають бути вирішені до моменту інтеграції. Одним з таких питання є підвищення надійності електричних мереж. Це питання частково може бути вирішено, за рахунок оптимального секціонування повітряних розподільчих мереж 6 - 20 кВ в умовах застосування Smart Grid. У магістерській дисертації представлено варіант визначення оптимального секціонування розподільчих мереж 6 - 20 кВ, за допомогою покрашеної методики розрахунку на основі «жадібного» алгоритму, представлений аналіз комерціалізації запропонованої методики та проаналізовані соціально – економічні вигоди від його впровадження. Метою дисертаційної роботи є: проведення аналізу оптимального секціонування повітряних розподільчих мереж 6 - 20 кВ в умовах застосування Smart Grid технологій. Для досягнення мети були поставлені та вирішені такі питання: • проведений аналіз особливостей та шляхів підвищення надійності функціонування розподільних мереж напругою 6 - 20 кВ в України та світі; • розглянуті перспективи впровадження технологій Smart Grid з метою підвищення надійності розподільчих мереж; • вдосконалена методика оптимального секціонування розподільчих мереж 6 - 20 кВ; • розроблені пропозиції практичної реалізації (комерціалізації) розробленої методики та перспективи її подальшого розвитку. Об’єктом дослідження є процеси функціонування повітряних розподільчих мереж напругою 6 - 20 кВ в умовах застосування Smart Grid технологій. Предметом дослідження є особливості впливу Smart Grid технологій на надійність електропостачання споживачів. Метод дослідження. Для вирішення поставлених завдань у дисертаційній роботі було застосовано методи оптимального секціонування повітряних розподільчих мереж в умовах врахування нормування показників надійності. За основу для розрахунку оптимального секціонування розподільчих мереж був використаний «жадібний алгоритм». Основні наукові результати роботи включають в себе: - набула подальшого розвитку методика оптимального секціонування повітряних розподільних мереж, що дозволило вирішувати задачу в умовах широкого використання засобів розосередженої генерації та узгодження роботи окремих комутаційно-захисних апаратів, що дозволяє підвищити надійність роботи інтегрованих систем електропостачання, які при цьому утворюються; - вперше здійснено аналіз можливості та доцільності впровадження технології SOP в розподільних мережах в плані підвищення надійності їх роботи, що надає можливість більш широкого й ефективного використання розосередженої генерації; - удосконалено структуру управління РМ на базі OMS, що поряд з підвищенням надійності електропостачання надає можливість одночасного зменшення втрат електричної енергії. Практичне значення одержаних результатів полягає в: - розробці програмного забезпечення для вирішення задачі оптимального секціонування розподільних мереж з інтегрованими в них джерелами розосередженої генерації та при можливості використання широкого спектру комутаційно-захисних пристроїв; - використанні, так званого, «жадібного» алгоритму, що без втрати ефективності отриманого результату в декілька разів скоротити час на вирішення задачі оптимального секціонування розподільних мереж.<br>Relevance of the topic. Given the policy set out in Ukraine's electricity sector development strategy, namely integration into ENTSO-E, a number of issues arise that need to be addressed by the time of integration. One such issue is to increase the reliability of electrical networks, which can be partially solved via the optimal sectionalizing of overhead distribution networks 6 - 20 kV in terms of Smart Grid. The master's dissertation presents a way of determining the optimal sectionalizing of 6 - 20 kV distribution networks, using an improved calculation method based on the "greedy" algorithm, presents an analysis of the commercialization of the proposed method and analyzes the socio-economic benefits of its implementation. The purpose of the work: analysis of the optimal sectionalizing of overhead distribution networks 6 - 20 kV in terms of Smart Grid technologies. To achieve this goal, the following issues were considered and resolved: • the analysis of features and ways to increase the reliability of functioning of distribution networks with a voltage of 6 - 20 kV in Ukraine and the world was carried out; • the prospects of introduction of Smart Grid technologies in order to increase the reliability of distribution networks were considered; • the method of optimal sectionalizing of 6 - 20 kV distribution networks was improved; • a proposal of practical realization (commercialization) of the developed technique and prospects of its further development was made. The object of the study is the processes of functioning of overhead distribution networks with a voltage of 6 - 20 kV in the conditions of application of Smart Grid technologies. The subject of the study is the features of the influence of Smart Grid technologies on the reliability of electricity supply to consumers. Research methods. To solve the set tasks, the methods of optimal sectioning of overhead distribution networks were applied, taking into account the standardization of reliability indicators. The “greedy algorithm” was used as a basis for calculation of the optimal partitioning of distribution networks. The main scientific results of the work include: • the technique of optimal sectioning of overhead distribution networks was further developed, which made it possible to solve the problem in the conditions of widespread use of distributed generation means and coordination of the operation of individual switching-protective devices, which makes it possible to increase the reliability of the integrated power supply systems, which are formed in this case; • for the first time, an analysis was made of the possibility and feasibility of introducing SOP technology in distribution networks in terms of increasing the reliability of their operation, it makes it possible to use more widely and efficiently distributed generation; • improved control structure of distribution network based on OMS, which, along with increasing the reliability of power supply, provides an opportunity to simultaneously reduce losses of electrical energy. The practical significance of the results obtained is: • development of software for solving the problem of optimal sectionalizing of distribution networks with integrated sources of distributed generation and, if possible, using a wide range of switching protection devices; • using the so-called "greedy" algorithm, without losing the effectiveness of the result obtained, to reduce several times the time for solving the problem of optimal partitioning of distribution networks.

Les processus autorégressifs à bifurcation (BAR) ont été au centre de nombreux travaux de recherche ces dernières années. Ces processus, qui sont l'adaptation à un arbre binaire des processus autorégressifs, sont en effet d'intérêt en biologie puisque la structure de l'arbre binaire permet une analogie aisée avec la division cellulaire. L'objectif de cette thèse est l'estimation les paramètres de variantes de ces processus autorégressifs à bifurcation, à savoir les processus BAR à valeurs entières et les processus BAR à coefficients aléatoires. Dans un premier temps, nous nous intéressons aux processus BAR à valeurs entières. Nous établissons, via une approche martingale, la convergence presque sûre des estimateurs des moindres carrés pondérés considérés, ainsi qu'une vitesse de convergence de ces estimateurs, une loi forte quadratique et leur comportement asymptotiquement normal. Dans un second temps, on étudie les processus BAR à coefficients aléatoires. Cette étude permet d'étendre le concept de processus autorégressifs à bifurcation en généralisant le côté aléatoire de l'évolution. Nous établissons les mêmes résultats asymptotiques que pour la première étude. Enfin, nous concluons cette thèse par une autre approche des processus BAR à coefficients aléatoires où l'on ne pondère plus nos estimateurs des moindres carrés en tirant parti du théorème de Rademacher-Menchov.

Cette thèse, comporte deux parties distinctes.Dans la première partie, on étudie l'existence et l'inexistence d'une inégalité qu'on a appelée l'inégalité de Hopf Uniforme (IHU), pour une équation linéaire de la forme Lv = f à coefficients bornés mesurables et sous les conditions de Dirichlet homogènes. L'IHU est une variante du principe de maximum, on l'a appliquée dans la preuve de la régularité W1;p 0 pour un problème semi-linéaire singulier : Lu = F(u) où les coefficients de L sont dans l'espace vmor (fonctions à oscillation moyenne évanescente) et F(u) est singulier en u = 0 F(0) = +∞. De plus, si les coefficients sont lipschitziens, on prouve que la régularité optimale du gradient de la solution u est bmor (fonctions à oscillation moyenne bornée i.e Grad u dans bmor).Dans la seconde partie, on s'intéresse à la régularité du système d'élasticité (équations stationnaires des ondes élastiques) avec une fonction source singulière au sens qu'elle n’est qu'intégrable par rapport à la fonction distance au bord du domaine. Via la dualité, nous montrons, selon ~f , que le problème admet une solution dite très faible dont le gradient n'est pas nécessairement intégrable sur tout le domaine mais uniquement localement. Nous déterminons aussi les fonctions vectorielles ~f pour lesquelles, ~u a son gradient intégrable sur tout l'espace de travail<br>We discuss the existence and non existence of the so called Hopf uniform Inequality (variant of a maximum principle) for the linear equation Lv = f with measurable coefficients and under the homogeneous Dirichlet Boundary condition. Then we apply such inequality to prove the W1;p 0 -regularity of a semi linear problem Lu = F(u), singular at u = 0, with the coefficients of the main operator of L in the space of vanishing mean oscillation. Moreover, when those coefficients are Lipschitz, we show that the gradient of the solution is at most in the space of bounded mean oscillation : bmor. In the last part of this thesis, we are concerned with the linear easticity system (Stationnary equation of the waves elasticity). But, here the second terms varies with respect to the distance function until the boundary.Using the duality method, we study the regularity of the solution of the elasticity system for the data belonging to various weighted spaces

As imagens de ressonância magnética (RM) ponderadas em Difusão são conhecidas como uma técnica funcional capaz de refletir alterações estruturais e celulares de neoplasias. No câncer de mama, a difusão e sua quantificação através dos valores do coeficiente de difusão aparente (CDA) têm sido utilizados para avaliar resposta tumoral após quimioterapia neoadjuvante (QTN). Os variados desfechos clínicos do câncer de mama, incluindo as diferentes respostas ao tratamento quimioterápico podem estar relacionados à heterogeneidade da doença. A presença das células tronco tumorais (CTT) é uma das hipóteses aceitas para explicar os diferentes comportamentos biológicos dos tumores. Este estudo buscou avaliar uma possível associação entre os valores de CDA nas neoplasias invasivas da mama e a presença de marcadores de CTT e os principais marcadores prognósticos da doença em pacientes tratadas com QTN. Foram avaliadas prospectiva e consecutivamente as imagens de RM pré-tratamento de 27 pacientes com câncer da mama que realizaram QTN seguida de cirurgia. Os valores de CDA média, p10, p25 e p50 foram obtidos através de duas mensurações, uma com único ROI e outra com múltiplos ROIs envolvendo toda extensão tumoral. Esses valores de CDA foram correlacionados: à quantificação por citometria de fluxo de CTT com fenótipos ESA+/CD44+/CD24-, células ESA+ com alta atividade ALDH1 e células ESA+/ABCG2+, à capacidade de formação de mamoesferas, e aos principais fatores prognósticos do câncer de mama, incluindo estágio clínico, doença axilar linfonodal, grau tumoral, receptores de estrógeno (RE), receptores de progesterona (RP) e superexpressão do HER2. Também foi realizada correlação dos valores de CDA com a resposta patológica completa após QTN. A presença de CTT, a capacidade de formação de mamoesferas e a resposta patológica completa não se correlacionaram aos valores de CDA. Para ambas as medidas e todos os parâmetros avaliados de CDA (x10-3mm2/s), os valores foram significantemente menores nos tumores com estágio clínico III e IV vs II (0,90±0,16; 1,02±0,18); com doença linfonodal após QTN vs axila livre (0,89±0,16; 1,01±0,17); RE+ vs RE- (0,90±0,16; 1,00±0,18); RP+ vs RP- (0,91±0,16; 0,98±0,18) e HER2+ vs HER2- (0,92±0,17;0,97±0,18). Tumores grau 1 apresentaram CDA com valores significativamente maiores em relação aos tumores grau 2 (diferença 0,18; CI: 0,03-0,33, p=0,02). Os valores de CDA dos tumores de mama pré-QTN não predizem a presença de CTT, a capacidade de formação de mamoesferas ou a resposta patológica completa, porém se correlacionam com o estágio clínico da doença, doença linfonodal axilar após QTN, grau tumoral e expressão das proteínas RE, RP e HER2, sendo um promissor marcador de agressividade tumoral<br>The diffusion-weighted magnetic resonance imaging (DWMRI) is a functional technique able to reflect structural and cellular changes in the tumors. In the breast cancer, the diffusion-weighted images and its numeric value known as the apparent diffusion coefficient (ADC) has been applied to evaluate pathologic response in patients treated with neoadjuvant chemotherapy (NC). The difference in the clinical results after breast cancer treatment, including different rates of responses to the NC has been associated to the heterogeneity of the disease. The presence of the breast cancer stem cells (BCSC) is an accepted hypothesis to explain the different biologic breast cancers behaviors. The aim of this study was to correlate the ADC value of invasive breast cancer with the presence of cancer stem cells markers and the major prognostic factors in patients treated with neoadjuvant chemotherapy. Prospectively, the MRI pre-treatment of twenty-seven consecutive patients with invasive breast cancer posteriorly treated with NC followed by surgery were evaluated. The ADC values mean, 10th percentile, 25th percentile, 50th percentile were obtained from two measurements, one of them with a unique ROI and the other with multiple ROIs encompassing the entire lesion. The ADC values were correlated to: presence of BCSCs (cell surface markers CD44+/CD24-, ABCG2 and ALDH1) identified by flow cytometric analysis, tumor grade, breast cancer staging, lymph nodal involvement, expression of estrogen receptors (ER), expression of progesterone receptors (PR) and expression of HER2. The assay mammospheres (Mammocult ®) were analyzed in 18 samples. Additionally, the ADC values were correlated to the pathologic complete response after QN treatment. There were no correlations between ADC values and breast cancer stem cells markers or mammospheres formation efficiency. For all parameters calculated, the ADC values (x10- 3 mm 2 /s) were lower in: breast cancer stage III and IV than stage II (0,90±0,16; 1,02±0,18), tumors with lymph node metastasis than without lymph node metastasis (0,89±0,16; 1,01±0,17), ER expression than ER negative (0,90±0,16; 1,00±0,18), PR expression than PR 10 negative (0,91±0,16; 0,98±0,18) and HER2 expression than HER2 negative (0,92±0,17; 0,97±0,18). The ADC values were significantly higher in grade-1 tumors (difference 0,18; CI: 0,03-0,33) compared to grade-2 tumors (p=0,02). The tumors values of ADC pretreatment were not correlated to the pathologic complete response after NC. The ADC values in pre-treatment invasive breast cancers are not a predictor of BCSC presence, mammospheres formation efficiency or pathologic complete response to QN. However it is correlated to the tumor grade, breast cancer staging, lymph nodal involvement, expression of ER, PR and HER2 and may represent a promising marker of tumor aggressiveness

Complex networks have been studied extensively due to their relevance to many real-world systems such as the world-wide web, the internet, biological and social systems. During the past two decades, studies of such networks in different fields have produced many significant results concerning their structures, topological properties, and dynamics. Three well-known properties of complex networks are scale-free degree distribution, small-world effect and self-similarity. The search for additional meaningful properties and the relationships among these properties is an active area of current research. This thesis investigates a newer aspect of complex networks, namely their multifractality, which is an extension of the concept of selfsimilarity. The first part of the thesis aims to confirm that the study of properties of complex networks can be expanded to a wider field including more complex weighted networks. Those real networks that have been shown to possess the self-similarity property in the existing literature are all unweighted networks. We use the proteinprotein interaction (PPI) networks as a key example to show that their weighted networks inherit the self-similarity from the original unweighted networks. Firstly, we confirm that the random sequential box-covering algorithm is an effective tool to compute the fractal dimension of complex networks. This is demonstrated on the Homo sapiens and E. coli PPI networks as well as their skeletons. Our results verify that the fractal dimension of the skeleton is smaller than that of the original network due to the shortest distance between nodes is larger in the skeleton, hence for a fixed box-size more boxes will be needed to cover the skeleton. Then we adopt the iterative scoring method to generate weighted PPI networks of five species, namely Homo sapiens, E. coli, yeast, C. elegans and Arabidopsis Thaliana. By using the random sequential box-covering algorithm, we calculate the fractal dimensions for both the original unweighted PPI networks and the generated weighted networks. The results show that self-similarity is still present in generated weighted PPI networks. This implication will be useful for our treatment of the networks in the third part of the thesis. The second part of the thesis aims to explore the multifractal behavior of different complex networks. Fractals such as the Cantor set, the Koch curve and the Sierspinski gasket are homogeneous since these fractals consist of a geometrical figure which repeats on an ever-reduced scale. Fractal analysis is a useful method for their study. However, real-world fractals are not homogeneous; there is rarely an identical motif repeated on all scales. Their singularity may vary on different subsets; implying that these objects are multifractal. Multifractal analysis is a useful way to systematically characterize the spatial heterogeneity of both theoretical and experimental fractal patterns. However, the tools for multifractal analysis of objects in Euclidean space are not suitable for complex networks. In this thesis, we propose a new box covering algorithm for multifractal analysis of complex networks. This algorithm is demonstrated in the computation of the generalized fractal dimensions of some theoretical networks, namely scale-free networks, small-world networks, random networks, and a kind of real networks, namely PPI networks of different species. Our main finding is the existence of multifractality in scale-free networks and PPI networks, while the multifractal behaviour is not confirmed for small-world networks and random networks. As another application, we generate gene interactions networks for patients and healthy people using the correlation coefficients between microarrays of different genes. Our results confirm the existence of multifractality in gene interactions networks. This multifractal analysis then provides a potentially useful tool for gene clustering and identification. The third part of the thesis aims to investigate the topological properties of networks constructed from time series. Characterizing complicated dynamics from time series is a fundamental problem of continuing interest in a wide variety of fields. Recent works indicate that complex network theory can be a powerful tool to analyse time series. Many existing methods for transforming time series into complex networks share a common feature: they define the connectivity of a complex network by the mutual proximity of different parts (e.g., individual states, state vectors, or cycles) of a single trajectory. In this thesis, we propose a new method to construct networks of time series: we define nodes by vectors of a certain length in the time series, and weight of edges between any two nodes by the Euclidean distance between the corresponding two vectors. We apply this method to build networks for fractional Brownian motions, whose long-range dependence is characterised by their Hurst exponent. We verify the validity of this method by showing that time series with stronger correlation, hence larger Hurst exponent, tend to have smaller fractal dimension, hence smoother sample paths. We then construct networks via the technique of horizontal visibility graph (HVG), which has been widely used recently. We confirm a known linear relationship between the Hurst exponent of fractional Brownian motion and the fractal dimension of the corresponding HVG network. In the first application, we apply our newly developed box-covering algorithm to calculate the generalized fractal dimensions of the HVG networks of fractional Brownian motions as well as those for binomial cascades and five bacterial genomes. The results confirm the monoscaling of fractional Brownian motion and the multifractality of the rest. As an additional application, we discuss the resilience of networks constructed from time series via two different approaches: visibility graph and horizontal visibility graph. Our finding is that the degree distribution of VG networks of fractional Brownian motions is scale-free (i.e., having a power law) meaning that one needs to destroy a large percentage of nodes before the network collapses into isolated parts; while for HVG networks of fractional Brownian motions, the degree distribution has exponential tails, implying that HVG networks would not survive the same kind of attack.

The work is focussed on the determination of capital structure in its market values, determination of the cost of non-own capital, and determination of the cost of equity, primarily by using the CAPM method. In terms of the CAPM procedure the work deals with the main parameters required by the method, such as risk-free yield rate, risk market premium, and beta coefficient. Furthermore, attention is given to modifications resulting from the inaccuracies of the CAPM method to make the method correspond as much as possible with the actual yield and risk of shares historically achieved at the capital market, and likewise to modifications needed when applying the CAPM method to the valuation of Czech businesses. The recommended procedure of determining the market discount rate for the valuation of an enterprise is applied on an example. Data obtained from the capital market of the Czech Republic are used to calculate the risk premium of the Czech capital market and beta coefficient of selected ten shares out of the Czech capital market, giving an assessment of the possibility of using the data obtained from the Czech capital market for the valuation of businesses incorporated in the Czech Republic.

ACI Committee 544's repeated drop-weight impact test for concrete is often criticized for large variations within the results. This paper identifies the sources of these large variations and accordingly suggests modifications to the ACI test. The proposed modifications were evaluated and compared to the current ACI test by conducting impact resistance tests on 40 specimens from two batches of polypropylene fiber-reinforced concrete (PPFRC). The results obtained from both methods were statistically analyzed and compared. The variations in the results were investigated within the same batch and between different batches of concrete. The impact resistance of PPFRC specimens tested with the current ACI test exhibited large coefficients of variation (COV) of 58.6% and 50.2% for the first-crack and the ultimate impact resistance, respectively. The corresponding COV for PPFRC specimens tested according to the modified technique were 39.4% and 35.2%, indicating that the reliability of the results was significantly improved. It has been shown that, using the current ACI test, the minimum number of replications needed per each concrete mixture to obtain an error below 10% was 41 compared to 20 specimens for the modified test. Although such a large number of specimens is not good enough for practical and economical reasons, the reduction presents a good step on the development of a standard impact test.

碩士<br>淡江大學<br>資訊工程學系碩士班<br>98<br>Over the past decade the studies of complex networks have been analyzed and researched. In analyzing Clustering coefficient is a important concept Clustering coefficient characterizes the relative tightness of a network and is a defining network statistics that appears in many “real-world” network data. This paper proposed a local link switching algorithm which effectively increases the clustering coefficient of a directed weight network while preserving the network node degree distributions. This link switching algorithm is based on local neighborhood information. Link switching algorithm is widely used in producing similar networks with the same degree distribution, that is, it is used in ‘sampling’ networks from the same network pool. How to use this algorithm to implement in directed and weight network is major study in this paper.

碩士<br>國立中正大學<br>電機工程研究所<br>106<br>Super-resolution is a technique majoring to restore the lost information when image scaling, such like the edge blurry in image scaling up, or it cannot describe the original object details in low-resolution image, and it will cause the quality decrease when image scaling. To reach the goal of light-weight Super-resolution, this research is major to reconstruct the image details and reducing the impact on image quality of image scaling without increasing excess computational cost. Based on conventional image interpolation scheme, the proposed technique utilizes the high frequency component of the image generated by the bilateral filter to compensate the detail distortion during scaling. By analysis the image standard deviation and local gradient, the proposed algorism redefines the bilateral filter with range filter and noise reduction filter, it will improve the characteristic of object details when image scaling and Simultaneously improve the image quality by noise reduction. In addition to improving the image quality, the research also focused on reducing the computational complexity and hardware cost. We are devoted to implement the hardware of real-time applications with line buffer-based algorithm.

yes<br>ACI Committee 544’s repeated drop-weight impact test for concrete is often criticized for large variations within the results. This paper identifies the sources of these large variations and accordingly suggests modifications to the ACI test. The proposed modifications were evaluated and compared to the current ACI test by conducting impact resistance tests on 40 specimens from two batches of polypropylene fiber-reinforced concrete (PPFRC). The results obtained from both methods were statistically analyzed and compared. The variations in the results were investigated within the same batch and between different batches of concrete. The impact resistance of PPFRC specimens tested with the current ACI test exhibited large coefficients of variation (COV) of 58.6% and 50.2% for the first-crack and the ultimate impact resistance, respectively. The corresponding COV for PPFRC specimens tested according to the modified technique were 39.4% and 35.2%, indicating that the reliability of the results was significantly improved. It has been shown that, using the current ACI test, the minimum number of replications needed per each concrete mixture to obtain an error below 10% was 41 compared to 20 specimens for the modified test. Although such a large number of specimens is not good enough for practical and economical reasons, the reduction presents a good step on the development of a standard impact test.

碩士<br>樹德科技大學<br>電腦與通訊系碩士班<br>106<br>In this thesis, we will solve for the coefficient estimation problem of digital system using the particle swarm optimization (PSO) algorithm. The influence of the weight parameter of the algorithm on the estimation performance are further examined and discussed. To verify the feasibility and effectiveness of the proposed scheme on the coefficient estimation of digital systems, four different experiments including the FIR digital filter, IIR digital filter, Volterra digital system, and bilinear digital filter are demonstrated. Some conclusions are also addressed.

Кваліфікаційна робота магістра складається з трьох розділів. Об’єкт дослідження – жіночі сумки виготовленні зі шкіри. У роботі розглядаються теоретичні аспекти ідентифікації та товарознавчої експертизи шкіряних жіночих сумок, споживних властивостей жіночих сумок та вимоги, які висуваються до якості жіночих шкіряних сумок. Проаналізовано нормативну документацію, яка регламентує якість шкіряної галантереї, вимоги, які висуваються до критеріїв та показників ідентифікації товарів. Використані експертні методи оцінювання та розрахунків коефіцієнтів вагомості показників естетичних та ергономічних показників. Запропоновано балову оцінку показників якості естетичних та ергономічних властивостей жіночих шкіряних сумок, перечень критеріїв та показників ідентифікації жіночих шкіряних сумок, програму експертизи жіночих шкіряних сумок та методи дослідження шкіряних сумок.<br>The diploma consists of three chapters. Object of study women's bags made of leather. Diploma thesis deals with theoretical aspects of identification and commodity expertise of leather women's bags, consumer properties of women's bags and the requirements imposed on the quality of women's leather bags, the choice of the most important consumer properties of women's bags and the determination of the weighting factors for these indicators.

Trabalho final de mestrado integrado em Medicina área científica de Imagiologia, apresentado á Faculdade de Medicina da Universidade de Coimbra<br>Purpose: To measure apparent diffusion coefficient (ADC) values of liver parenchyma and focal hepatic lesions (FHL), investigate the utility of ADC for the differential diagnosis of hepatic findings, and determine the influence of region of interest (ROI) characteristics in the overall ADC measurements. Materials and Methods: Ninety-three patients (47 men, 46 women; mean age, 58 years) with at least one FHL ≥ 10 mm, or parenchyma abnormalities, were retrospectively evaluated. Reference standard for diagnosis was obtained from histopathologic data, consensus between imaging methods, follow-up imaging and patient clinical history. A total of 90 lesions were evaluated: 14 hepatocellular carcinomas (HCC), 18 metastases, 10 focal nodular hyperplasias (FNH), 4 adenomas, 30 hemangiomas and 14 cysts. Respiratory-Triggered (RT) DWI was performed using b-values of 50 and 700 s/mm2. ADC was measured in hepatic parenchyma by placing ROIs in four different segments, and in FHL by using three circular 1 cm2 ROIs and one ROI encompassing all lesion volume. Data was statistically compared in SPSS software using the Mann-Whitney and Friedman tests. Wilcoxon test was used to confirm ROI influence and receiver operating characteristic (ROC) curve was analyzed to evaluate the utility of ADC for diagnosis of malignancy. P<0.05 was significant. Results: Mean ADCs (×10−3mm2/s) were 1.45, 1.28 and 1.25 for normal, cirrhotic and steatotic liver parenchyma and 1.16, 1.18, 1.30, 1.64, 1.89 and 2.77 for metastases, HCCs, adenomas, FNHs, hemangiomas and cysts, respectively. Parenchyma ADCs in segment II were significantly higher than in any other region. ADCs of malignant lesions were significantly lower than those of benign lesions (p<0.001). Individually, ADCs of Cysts were significantly higher than all other lesions except hemangiomas. There was significant overlap between benign solid lesions and malignant lesions and between HCCs and cirrhotic parenchyma. The area under the curve for diagnosis of malignancy was 0.939, with sensitivity of 89.7% and specificity of 90.6%, using a cutoff ADC of 1.43×10−3 mm2/s. No significant difference was found between the different ROI sampling methods, but only homogeneous lesions were studied. Conclusion: We concluded that (a) quantitative measurements of ADC can be useful in differentiating normal from pathological liver parenchyma and in the characterization of focal hepatic lesions, (b) left hepatic lobe is more subject to cardiac motion artifacts, and (c) the size of ROI does not influence ADC measurements in homogeneous lesions<br>Objectivo: Medir o coeficiente de difusão aparente (ADC) do parênquima hepático e de lesões hepáticas focais (LHF), investigar a utilidade do ADC no diagnóstico diferencial de lesões hepáticas e determinar a influência das características da região de interesse (ROI) nos valores de coeficiente obtidos. Materiais e Métodos: Noventa e três doentes (47 homens, 46 mulheres; idade média, 58 anos) com pelo menos uma LHF maior ou igual que 10 mm, ou parênquima patológico, foram retrospectivamente avaliados. Confirmação diagnóstica foi obtida por histopatologia, concordância entre métodos de imagem, follow-up e historial do doente. No total, 90 lesões foram avaliadas: 14 carcinomas hepatocelulares (CHC), 18 metástases, 10 hiperplasias nodular focais (HNF), 4 adenomas, 30 hemangiomas e 14 quistos. Foi efectuado estudo ponderado em difusão com trigger respiratório (valores b de 50 e 700 s/mm2). Medições de ADC foram efectuadas no parênquima através de ROIs colocadas em quarto segmentos hepáticos e, nas LHF, através de três ROIs de 1 cm2 e uma ROI englobando toda a lesão. O tratamento estatístico foi efectuado, através do software SPSS, pelos testes Mann-Whitney e Friedman. O teste Wilcoxon foi utilizado para confirmar a influência do ROI e uma curva ROC foi analisada para avaliar o ADC como ferramenta diagnóstica de malignidade. P<0.05 foi considerado significativo. Resultados: ADCs médios (×10−3mm2/s) foram 1.45, 1.28 e 1.25 para parênquima normal, cirrótico e esteatótico, e 1.16, 1.18, 1.30, 1.64, 1.89 e 2.77 para metástases, CHCs, adenomas, HNFs, hemangiomas e quistos, respectivamente. ADCs medidos (×10−3mm2/s) no parênquima do segmento II foram significativamente mais altos do que em qualquer outro segmento. Lesões malignas apresentaram ADCs significativamente mais baixos que lesões benignas (p<0.001). Individualmente, os ADCs de quistos foram significativamente maiores do que os de outras lesões, exceptuando hemangiomas. Verificou-se uma sobreposição significativa entre lesões sólidas benignas e leso+es malignas, e entre CHCs e parênquima cirrótico. A área sobre a curva para diagnóstico de malignidade foi 0.939, com um ADC limiar de 1.43×10−3 mm2/s (sensibilidade de 89.7% e especificidade de 90.6%). Não foi encontrada diferença significativa entre as medições efectuadas com as ROIs de diferentes tamanhos. Conclusão: Concluímos que (a) medições quantitativas de ADC são úteis na distinção entre parênquima normal e patológico e na caracterização de LHF, (b) o lobo hepático esquerdo é mais susceptível a artefactos cardíacos, e (c) o tamanho da ROI não influencia o valor do ADC calculado.

Trabalho final de mestrado integrado em Medicina, apresentado à Faculdade de Medicina da Universidade de Coimbra.<br>Purpose: To assess the relevance of diffusion-weighted imaging (DWI) in the hepatocellular carcinoma (HCC) detection as a stand-alone procedure or in combination to conventional magnetic resonance imaging (MRI). Methods: Medical records from nineteen patients with pathological confirmation of HCC, who have been submitted to conventional MRI and DWI in a time frame 3 months prior and 3 months after diagnosis, were retrospectively reviewed. For each patient, apparent diffusion coefficient (ADC) values were measured in the HCC lesion, in the liver parenchyma and in the spleen. Tumor ADC and parenchyma ADC, obtained with and without normalization, were compared through paired-samples t-test. Tumor ADC was analyzed according to lobe, size category and acquisition system using the Mann-Whitney test. For sensitivity assessment of DWI and conventional MRI, individually and combined, a contingency table was made. Results: The calculated DWI sensitivity for HCC detection (47.4%) was lower than conventional MRI sensitivity (68.4%). The highest sensitivity was obtained with the combined reading of both techniques (78.9%). A statistically significant difference between tumor ADC and parenchymal ADC was found, both for normalized and non-normalized values, with lower values for the HCC lesions. Comparison of tumor ADC values according to lobe, size and acquisition system did not show a statistically significant difference. Conclusions: For HCC detection in the setting of liver cirrhosis the use of DWI increases tumor detection compared to conventional MR alone and its use is recommended. This result corroborates other literature reports regarding the added value of DWI in HCC diagnosis, irrespective of the magnetic field strength. Due to the small patient sample of the current series further investigation may be warranted.<br>Objectivo: Determinar a relevância da ressonância magnética ponderada em difusão (DWI) no diagnóstico do carcinoma hepatocelular (CHC) a título individual e enquanto complemento à ressonância magnética (RM) convencional. Métodos: Registos médicos de dezanove pacientes com confirmação anatomopatológica de CHC, que tinham sido submetidos a RM convencional e DWI na faixa temporal 3 meses antes e 3 meses depois do diagnóstico, foram revistos retrospectivamente. Para cada paciente foram medidos os valores do coeficiente de difusão aparente (ADC) na lesão tumoral, no parênquima hepático e no baço. O ADC do tumor e o ADC do parênquima, com e sem normalização, foram comparados através do t-teste para amostras emparelhadas e o ADC do tumor foi analisado de acordo com lobo, categoria dimensional e sistema de aquisição utilizando o teste de Mann-Whitney. Para determinação da sensibilidade da DWI e da RM convencional, individualmente e em conjunto, foi feita uma tabela de contingência. Resultados: A sensibilidade calculada da DWI (47.4%) foi inferior à da RM convencional (68.4%). Contudo, a sensibilidade calculada quando ambos os métodos foram combinados (78.9%) revelou-se superior. Foi encontrada uma diferença estatisticamente significativa entre o ADC do tumor e o ADC do parênquima hepático, tanto para os valores não normalizados como para os normalizados, com valores menores registados para as lesões tumorais. Após comparação dos ADC tumorais de acordo com lobo, categoria dimensional e sistema de aquisição, não foi encontrada uma diferença estatisticamente significativa. Conclusões: Os resultados do nosso estudo estão em concordância com a literatura mais recente que sustenta o valor adicional da DWI no diagnóstico do CHC. No entanto, as limitações que reconhecemos ao presente trabalho sugerem a necessidade de mais investigação nesta área.

碩士<br>國立彰化師範大學<br>統計資訊研究所<br>97<br>Many studies in medical, industry and business fields commonly use questionnaires and diagnoses reported by different raters or instruments to evaluate the agreement of multiple ratings. The most popular indices of agreement for a categorical response are the kappa measures, Cohen’s kappa for binary outcomes and weighted kappa for ordinal outcomes (Cohen 1960, 1968). However, when raters assess the same observation on two or more occasions, these ratings are dependent, and, therefore one must take into account the correlation between the kappa estimates for making inference. In this thesis, we focus on estimating kappa measures on inter and intra-agreement using the weighted least squares (WLS) approach for dependent categorical data and testing the equality of the dependent kappa coefficients by using PROC CATMOD in SAS. We modified the SAS code in Barnhart and Williamson (2002) to analyze dependent agreement data with more than two raters and to use different numbers of categories. In addition, it will be compared with the results using generalized estimating equation (GEE) for Cohen’s kappa and weighted kappa. Simulation studies are conducted to evaluate the performance under WLS and GEE approaches. Four applications of repeated ratings by multiple raters are illustrated, including similarity in myopic status for twin pairs with respect to zygosity, conformity between an optometric device and ophthomologist in diagnoses of high myopia, test-retest radiographic examinations by seven endodontists, and comparison between a computerized planimetry method and direct visual assessment for assessing cervical ectopy. The results reveal that the performance of WLS is better than that of GEE.

碩士<br>國立臺灣大學<br>生醫電子與資訊學研究所<br>103<br>Intravoxel incoherent motion diffusion-weighted magnetic resonance imaging (IVIM DW MRI) is a technique that can quantitatively assess both the water molecular diffusion in static tissues (true diffusion coefficient, D) and the incoherent motion of blood water molecules in capillary networks due to perfusion (pseudo-diffusion coefficient, D*). However, D* value in liver parenchyma appears to be of high uncertainty among literatures. The aim of this study is to determine the reproducibility of D* in normal liver at 3T, considering SNR, b value sampling numbers and the existence of large vessel in ROI. A modified fit approach combined with an error evaluation method was proposed. Through the proposed method, the reproducibility of D* in 6-time-averaged liver images improved. Future studies can utilize this procedure for IVIM liver investigation while the scanning time can still be further optimized.

Breast cancer is a major global health problem and the most common form of cancer among women. Major advances in the technologies of imaging provide improved detection and sensitivity with fewer unnecessary biopsies. Commonly used imaging modalities include mammography, ultrasonography, magnetic resonance imaging (MRI), scintimammography, single photon emission computed tomography (SPECT) and positron emission tomography (PET). The current study is focused on breast MRI imaging, especially one of the most promising recent techniques, i.e. the Diffusion Weighted Imaging breast MRI (DWI). DWI is an unenhanced MRI technique, based on volume sequences on various b values (the b value identifies the measurement's sensitivity to diffusion and determines the strength and duration of the diffusion gradients) measuring the mobility of water molecules (Brownian motion) in vivo (in tissues) and provides different and potentially complementary information to Dynamic Contrast-Enhanced Magnetic Resonance Imaging (DCE-MRI) technique. As DWI based on the diffusive properties of water molecules, reflects their random motion resulting from thermal agitation. Water diffusion on breast can be quantified by measuring the mean diffusivity, which is the average of Apparent Diffusion Coefficient (ADC). The ADC can be calculated by making measurements at a low b factor, b1, and a higher b factor, b2. DWI allows the mapping of the diffusion process of molecules by the ADC map. ADC maps are calculated by collecting images with at least 2 different values, b1 and b2, of the b factor. The ADC map is a parametric image whose color scale or gray scale represents the ADC values of the voxels and is usually generated by proprietary or in house software. DWI apart from the 3D anatomical information, provides a noninvasive investigation of tissue vascularity, a novel contrast mechanism in MRI and has a high sensitivity in the detection of changes in the local biologic environment due to a pathologic process. Therefore, in addition to contrast enhancement-based characterization (DCE-MRI), measurement of the motion of water molecules in DWI provides an additional feature for lesion characterization that may further increase the specificity of MRI for classifying breast lesions. The diagnostic task that the current study deals with, accounts for the diagnosis of mass-like lesions in Diffusion Weighed Magnetic Resonance Imaging, based on low ADC values compared to high once in case of benign versus normal tissue. The hypothesis is that diffusivity of water molecules is restricted in environments of high cellularity, intracellular and extracellular edema, high viscosity, and fibrosis, such as malignant tumors, because these conditions become barriers to the movement of water molecules. Therefore, most of breast cancers show low ADC values compared with benign and normal tissue. Many studies have revealed the usefulness of ADC values in the differential diagnosis of breast lesions; however, the clinical effect remains limited because of the substantial overlap between benign and malignant lesions, which presents challenges for implementing a useful diagnostic ADC threshold. The majority of studies, similar to the current study, determined optimal cutoff levels of the ADC value between malignant and benign lesions by using ROC analysis, and ranged from 0.90 to 1.76 × 10-3 mm2/s while the sensitivity and specificity ranged from 63% to 100% and 46% to 97%, respectively. In addition, the methods for measuring ADC differ among reported studies, with the most representative method being the mean value of ADC (mean ± standard deviation) over a Region Of Interest representative of the breast lesion. The purpose of this study was to investigate the ability of histogram characteristics of Apparent Diffusion Coefficient (Apparent Diffusion Coefficient-ADC) to differentiate malignant from benign breast lesions in breast DWI. To this end the ADC maps of representative lesion ROIs were subjected to first order statistics analysis by calculating five first order textural features: Mean value, Standard Deviation, Kurtosis, Skewness and Entropy. This approach is intended to offer a more complete assessment of tumor texture and heterogeneity. The dataset analyzed is comprised of 92 histologically verified breast lesions, originating from 69 women with mammographically and/or ultrasonographically detected or palpable findings. Histology revealed 53 malignant lesions originating from 45 women and 39 benign lesions originating from 26 women. All of the breast MR examinations were performed with a 3T MR scanner, for b= 0, 900 s/mm2. Diagnostic performances of these parameters were compared by receiver operating characteristic (ROC) curve analysis. The mean of ADC of benign lesions [(1.470 ± 0.342) × 10-3 mm2/s] was found to be significantly higher than that of malignant tumours, [(0.965 ± 0.268) × 10-3 mm2/s, (p<0.00001)]. The standard deviation of ADC of benign lesions [(0.184 ± 0.999) × 10-3 mm2/s] was not significantly different from that of malignant tumours, [(0.192 ± 0.151) × 10-3 mm2/s, (p=0.6581)]. The skewness of ADC of benign [-0.303 ± 0.584] was significantly different than that of malignant tumours, 0.210 ± 0.725. (p = 0.0008)]. The kurtosis of ADC of benign [3.003 ± 1.065] was not significantly different from that of malignant tumours, [3.337 ± 1.334. (p=0.0987)]. The entropy of ADC of benign [4.794 ± 0.665] was significantly lower than that of malignant tumours, [5.569 ± 0.649, (p<0.00001)] The corresponding area under the empirical receiver operating characteristic curve was: 0.862 ± 0.042 (95% confidence interval: 0.754, 0.925) for mean of ADC, 0.705 ± 0.054 (95% confidence interval: 0.589, 0.800) for skeweness of ADC, 0.800 ± 0.046 (95% confidence interval: 0.691, 0.874) for entropy of ADC, resulting a good diagnostic performance of DWI for these parameters. On the other hand, an AUC of 0.527 ± 0.063 (95% confidence interval: 0.393, 0.640) and 0.601 ± 0.061 (95% confidence interval: 0.470, 0.707) for Standard deviation and kurtosis respectively, suggests a degree of overlap in ADC values between benign and malignant tumors. In an effort to identify optimal threshold values for differentiating benign versus malignant lesions these were selected to correspond to the points of highest accuracy of the ROC curves. In our study, we obtained two threshold values of mean ADC, both with an accuracy of 83.15%: 1.21 x 10-3 mm2/s with a sensitivity of 86.27% and specificity of 78.95%; and 1.32 x 10-3 mm2/s with a sensitivity of 92.16% and specificity of 71.05%. The threshold value of skeweness was -0.06 with an accuracy of 68.54%, a sensitivity of 66.03% and specificity of 66.67%. Finally, we found two threshold values of entropy, both with an accuracy of 76.40%: 5.17 with a sensitivity of 75.47% and specificity of 71.80%; and 5.21 with a sensitivity of 73.59% and specificity of 74.36%. In conclusion, results of the current study suggest the contribution of texture analysis methods in Diffusion-weighted MRI breast imaging for the quantification of tissue heterogeneity, providing important information for breast cancer diagnosis. Histogram analysis of ADC values in breast cancer has potential for differentiating benign and malignant tumors, providing information about the entire tumor. The mean, skewness and entropy of ADC are valuable parameters that are correlated with pathologic characterization of breast tumors. These 3 ADC parameters significantly elevated the quantitative diagnostic performance of breast DWI and would be effective parameters in distinguishing between malignant and benign breast lesions. Finally, future efforts will also focus on investigating the correlation of extracted texture features with histopathological findings, in order to verify the potential of the proposed texture analysis of ADC map in providing non-invasive prognostic factors of breast cancer.<br>Ο καρκίνος του μαστού είναι ένα σημαντικό παγκόσμιο πρόβλημα υγείας και η πιο διαδεδομένη μορφή καρκίνου στον γυναικείο πληθυσμό. Η ολοένα και πιο έγκαιρη διάγνωση του καρκίνου του μαστού έχει οδηγήσει σε σημαντική βελτίωση του ρυθμό θεραπείας της νόσου. Σημαντικές πρόοδοι στην τεχνολογία της απεικόνισης παρέχουν τη βελτιωμένη ανίχνευση και ευαισθησία του καρκίνου και οδηγούν σε όλο ένα και λιγότερες περιττές βιοψίες. Οι πιο συνηθισμένες μέθοδοι απεικόνισης, που χρησιμοποιούνται, περιλαμβάνουν την Μαστογραφία, την Υπερηχογραφία, την Μαγνητική Τομογραφία (MRI), την σπινθηρομαστογραφία, την Τομογραφία Εκπομπής Φωτονίων (SPECT) και την Τομογραφία Εκπομπής Ποζιτρονίων (PET). Η παρούσα μελέτη επικεντρώνεται στην τεχνολογία της Απεικόνισης Μαγνητικού Συντονισμού ειδικά σε μία πρόσφατη και ελπιδοφόρα τεχνική απεικόνισης του καρκίνου του μαστού, που ονομάζεται Απεικόνιση Σταθμισμένης Διάχυσης στη Τομογραφία Πυρηνικού Μαγνητικού Συντονισμού (Diffusion Weighted Imaging breast MRI (DWI)). Η DWI είναι μια MRI ακολουθία χωρίς χρήση σκιαγραφικής ουσίας, η οποία βασίζεται σε αλληλουχίες για διάφορες τιμές του παράγοντα διάχυσης b (η τιμή b προσδιορίζει την διαχυτότητα και καθορίζει την ένταση και τη διάρκεια των βαθμωτών πεδίων διάχυσης). Η DWI ποσοστικοποιεί την κινητικότητα των μορίων του νερού (Brownian κίνηση) in vivo (σε ιστούς) και παρέχει διαφορετικές και ενδεχομένως συμπληρωματικές πληροφορίες στην μαστογραφία μαγνητικής τομογραφίας με χρήση σκιαγραφικού (Dynamic Contrast-Enhanced Magnetic Resonance Imaging: DCE-MRI). Η DWI με βάση τις ιδιότητες διάχυσης των μορίων του νερού, αντανακλά την τυχαία κίνησής τους λόγω της θερμικής τους ενέργειας. Η διάχυση του νερού στον μαστό μπορεί να ποσοτικοποιηθεί με τη μέτρηση της μέσης διαχυτότητας, η οποία αναφέρεται ως Φαινόμενος Συντελεστής Διάχυσης (Apparent Diffusion Coefficient-ΑDC). Ο ADC υπολογίζεται ύστερα από μετρήσεις για δυο b τιμές, μια χαμηλή b1 και μια υψηλότερη b2 τιμή. Η DWI επιτρέπει την χαρτογράφηση της διάχυσης των μορίων του νερού μέσω του ADC χάρτη. Ο ADC χάρτης είναι μια παραμετρική εικόνα της οποίας η κλίμακα χρωμάτων ή κλίμακα των τόνων του γκρι, αντιπροσωπεύει τις ADC τιμές των voxels και συνήθως παράγεται από λογισμικό. Οι παραμετρικοί ADC χάρτες απεικόνισης DWI αναπαριστούν τη μικροδομή των ιστών για διάφορους συνδυασμούς τιμών της παραμέτρου b. Η DWI εκτός από 3D ανατομική πληροφορία, παρέχει μια μη επεμβατική διερεύνηση της αγγειοβρίθειας του ιστού, έναν νέο μηχανισμό αντίθεσης στην MRI, και χαρακτηρίζεται από υψηλή ευαισθησία στην ανίχνευση ενδεχόμενων αλλαγών στο τοπικό βιολογικό περιβάλλον, οι οποίες οφείλονται σε παθολογία. Ως εκ τούτου, εκτός από τον χαρακτηρισμό αλλοιώσεων βάση σκιαγραφικής ενίσχυσης (DCE - MRI), η ποσοτικοποίηση της κίνησης των μορίων του νερού στην DWI παρέχει επιπλέον στοιχεία για τον χαρακτηρισμό της αλλοίωσης, κάτι το οποίο μπορεί να αυξήσει περαιτέρω την ειδικότητα της MRI για την ταξινόμηση των αλλοιώσεων του μαστού. Το διαγνωστικό πρόβλημα το οποίο αντιμετώπισε/εστίασε η παρούσα διπλωματική εργασία, αφορά στο χαρακτηρισμό/διάγνωση χωροκατακτητικών αλλοιώσεων (mass-like) του μαστού στην Απεικονιση Μαγνητικου Συντονισμου Σταθμισμενης Διαχυσης (DWI) και την ποσοτικη αναλυση του Φαινομενου Συντελεστη Διαχυσης (ADC) για διαγνωση καρκινου του μαστου. Η ικανότητα διάχυσης των μορίων του νερού περιορίζεται σε περιβάλλον υψηλής κυτταροβρίθιας, ενδοκυττάριων και εξωκυττάριων οιδημάτων, υψηλού ιξώδους και ίνωσης, όπως συμβαίνει στους κακοήθεις όγκους, διότι οι παράγοντες αυτοί εμποδίζουν την κυκλοφορία των μορίων του νερού. Αποτέλεσμα αυτού είναι οι περισσότεροι καρκίνοι του μαστού να παρουσιάζουν χαμηλές ADC τιμές σε σύγκριση με τους καλοήθεις όγκους ή τον φυσιολογικό ιστό. Πολλές μελέτες έχουν δείξει τη χρησιμότητα των ADC τιμών στη διαφορική διάγνωση των αλλοιώσεων του μαστού. Εν τούτοις, το κλινικό αποτέλεσμα παραμένει περιορισμένο λόγω της σημαντικής επικάλυψης καλοήθων και κακοήθων αλλοιώσεων, γεγονός που αποτελεί πρόκληση για την εφαρμογή ενός χρήσιμου διαγνωστικού ορίου της μέσης ADC. Στη πλειοψηφία των μελετών, όπως και στη παρούσα μελέτη, τα βέλτιστα επίπεδα αποκοπής της ADC μεταξύ κακοήθων και καλοήθων αλλοιώσεων προσδιορίστηκαν με τη χρήση ROC ανάλυσης. Στις μέχρι τώρα μελέτες τα διαγνωστικά όρια της μέσης ADC κυμαίνονται από 0.90 έως 1.76 × 10-3 mm2 / s, με ευαισθησία και ειδικότητα να κυμαίνονται από 63% έως 100% και 46% έως 97%, αντίστοιχα. Γεγονός αποτελεί, επίσης, η διαφορετική μέθοδος υπολογισμού της ADC που ακολουθεί η κάθε μελέτη, με πιο συχνή μέθοδο, ο υπολογισμός της μέσης τιμής της ADC (μέση τιμή ± τυπική απόκλιση) σε μια περιοχή ενδιαφέροντος (ROI) μιας αλλοίωσης του μαστού. Σκοπός της παρούσας μεταπτυχιακής διπλωματικής εργασίας ήταν να διερευνηθεί η ικανότητα των χαρακτηριστικών ιστογράμματος του Φαινόμενου Συντελεστή Διάχυσης (Apparent Diffusion Coefficient-ADC) να διαφοροποιούν κακοήθεις από καλοήθεις αλλοιώσεις του μαστού στην Απεικόνιση Μαγνητικού Συντονισμού Σταθμισμένης Διάχυσης (Diffusion Weighted MRI-DWI). Για το σκοπό αυτό, δημιουργήθηκε ο ADC παραμετρικός χάρτης ο οποίος αποτέλεσε τη βάση για την εφαρμογή μεθόδου ανάλυσης υφής εικόνας, και τον υπολογισμό πέντε χαρακτηριστικών υφής πρώτης τάξης: την μέση τιμή, την τυπική απόκλιση, την κύρτωση, την λοξότητα και την εντροπία. Η προσέγγιση αυτή θεωρήθηκε ότι θα προσφέρει μια πιο ολοκληρωμένη αξιολόγηση της υφής του όγκου και της ετερογένειας. Η προσέγγιση εφαρμόσθηκε σε κλινικό δείγμα 92 ιστολογικά αποδεδειγμένων αλλοιώσεων του μαστού, οι οποίες προέρχονται από 69 γυναίκες οι οποίες είχαν νωρίτερα ανιχνευθεί μέσω μαστογραφίας ή/και υπερηχογραφίας ή από ψηλαφητά ευρήματα. Η ιστολογική εξέταση αποκάλυψε 53 κακοήθεις αλλοιώσεις που προέρχονταν από 45 γυναίκες και 39 καλοήθεις αλλοιώσεις από 26 γυναίκες. Όλες οι εξετάσεις μαγνητικής τομογραφίας του μαστού έγιναν με σύστημα MRI 3T και για b=0 και 900 s/mm2. Η διαγνωστική απόδοση/επίδοση των παραμέτρων αυτών συγκρίθηκε με την ανάλυση λειτουργικού χαρακτηριστικού δέκτη (ROC analysis). Τα αποτελέσματα υποδεικνύουν τον σημαντικό ρόλο της ανάλυσης ADC ιστογράμματος χρησιμοποιώντας τα 5 παραπάνω χαρακτηριστικά υφής για την ταυτοποίηση των αλλοιώσεων του μαστού. Οι μετρήσεις της μέσης τιμής, της λοξότητας και της εντροπία της ADC των καλοήθων και κακοήθων αλλοιώσεων του μαστού είχαν στατιστικώς σημαντική διαφορά. Ειδικότερα, η μέση ADC τιμή των καλοήθων όγκων [(1.470 ± 0.342) × 10-3 mm2/s] ήταν σημαντικά υψηλότερη από εκείνη των κακοήθων, [(0.965 ± 0.268) × 10-3 mm2/s, (ρ < 0.00001)]. Η λοξότητα της ADC των καλοήθων όγκων [-0.303 ± 0.584], διέφερε σημαντικά από εκείνη των κακοήθων, [0.210 ± 0.725. (ρ= 0.0008)]. Και η εντροπία της ADC των καλοήθων όγκων [4.794 ± 0.665], ήταν σημαντικά χαμηλότερη από εκείνη των κακοήθων, [5.569 ± 0.649, (ρ < 0.00001)]. Ωστόσο, η τυπική απόκλιση και η κύρτωση της ADC των καλοήθων και κακοήθων αλλοιώσεων του μαστού δεν είχαν στατιστικώς σημαντική διαφορά. Συγκεκριμένα, η τυπική απόκλιση της ADC των καλοήθων όγκων ήταν [(0.184 ± 0.999) × 10-3 mm2/s] ενώ των κακοήθων ήταν [(0.192 ± 0.151) × 10-3 mm2/s, (ρ = 0.6581)] και η κύρτωση της ADC των καλοήθων όγκων ήταν [3.003 ± 1.065] ενώ των κακοήθων ήταν [3.337 ± 1.334, (ρ = 0.0987)]. Η περιοχή κάτω από την ROC καμπύλη (AUC) για τη μέση ADC τιμή ήταν 0.862 ± 0.042 (95% διάστημα εμπιστοσύνης: 0.754, 0.925), για την λοξότητα της ADC ήταν 0.705 ± 0.054 (95% διάστημα εμπιστοσύνης: 0.589, 0.800) και για η εντροπία της ADC ήταν 0.800 ± 0.046 (95% διάστημα εμπιστοσύνης: 0.691, 0.874), και είχαν ως αποτέλεσμα μια καλή διαγνωστική απόδοση/ επίδοση της DWI για τις παραμέτρους αυτές. Από την άλλη πλευρά, η AUC με 0.527 ± 0.063 (95% διάστημα εμπιστοσύνης: 0.393, 0.640) και με 0.601 ± 0.061 (95% διάστημα εμπιστοσύνης: 0.470, 0.707) για την τυπική απόκλιση και την κύρτωση, αντίστοιχα, υποδηλώνει ένα βαθμό επικάλυψης στις ADC τιμές μεταξύ καλοήθων και κακοήθων όγκων. Τα βέλτιστα κατώφλια αποκοπής για διαφοροποίηση καλοήθων έναντι κακοήθων αλλοιώσεων καθορίστηκαν με τον εντοπισμό των σημείων όπου η ακρίβεια ήταν μέγιστη στις καμπύλες ROC. Από τη συγκεκριμένη μελέτη, προέκυψαν δύο τιμές κατωφλίου αποκοπής της μέσης ADC, με την ίδια ακρίβεια 83.15%. Το πρώτο κατώφλι με τιμή 1.21 x 10-3 mm2/s χαρακτηρίζεται με ευαισθησία 86.27% και ειδικότητα 78.95%. Και το δεύτερο κατώφλι με τιμή 1.32 x 10-3 mm2/s χαρακτηρίζεται με ευαισθησία 92.16% και ειδικότητα 71.05%. Το κατώφλι για την λοξότητα της ADC ήταν στα -0.06 με ακρίβεια 68.54%, ευαισθησία 66.03% και ειδικότητα 66.67%. Τέλος, προέκυψαν δύο τιμές κατωφλίου αποκοπής της εντροπίας της ADC με την ίδια ακρίβεια ακρίβεια 76.40%. Το πρώτο κατώφλι με τιμή 5.17 χαρακτηρίζεται με ευαισθησία 75.47% και ειδικότητα 71.80%. Και το δεύτερο κατώφλι με τιμή 5.21 χαρακτηρίζεται με ευαισθησία 73.59% και ειδικότητα 74.36%. Συμπερασματικά, τα αποτελέσματα της παρούσας μελέτης δείχνουν τη συνεισφορά των μεθόδων ανάλυσης υφής εικόνας στη Απεικονιση Μαγνητικου Συντονισμου Σταθμισμενης Διαχυσης (DWI) του μαστού για την ποσοτικοποίηση της ετερογένειας του ιστού, παρέχοντας σημαντικές πληροφορίες για τη διάγνωση του καρκίνου του μαστού. Η ανάλυση ιστογράμματος των ADC τιμών στον καρκίνο του μαστού έχει τη δυνατότητα διαφοροποίησης καλοήθων και κακοήθων όγκων, παρέχοντας πληροφορίες για το σύνολο του όγκου. Η μέση τιμή, η λοξότητα και η εντροπία του ADC είναι πολύτιμες παράμετροι που συσχετίζονται με παθολογικό χαρακτηρισμό των όγκων του μαστού. Αυτές οι 3 ADC παράμετροι αύξησαν σημαντικά την ποσοτική διαγνωστική απόδοση της DWI του μαστού και πιθανότατα να είναι αποτελεσματικές παράμετροι όσον αφορά τη διάκριση μεταξύ καλοήθων και κακοήθων αλλοιώσεων του μαστού Μελλοντικές προσπάθειες πρόκειται να εστιάσουν στη διερεύνηση της συσχέτισης των εξαχθέντων χαρακτηριστικών υφής με ιστοπαθολογικούς δείκτες, με σκοπό την περαιτέρω επιβεβαίωση των προτεινόμενων προσεγγίσεων και ενδεχομένως την χρήση συγκεκριμένων χαρακτηριστικών υφής ως μη επεμβατικών προγνωστικών δεικτών καρκίνου του μαστού.