O sucesso da cirurgia ortognática está relacionado com diversos fatores como análise facial precisa e acurada, e exames de imagem com alta qualidade. Atualmente, diversos programas de imagens tridimensionais, comerciais e abertos, estão disponíveis no auxílio diagnóstico, elaboração do plano de tratamento e simulação do procedimento cirúrgico para correção das deformidades dentofaciais. Entretanto, estudos avaliando os diferentes métodos de mensuração linear empregados pelos programas de imagem por meio da reconstrução 3D no planejamento da osteotomia tipo Le Fort I são escassos e, maiores esclarecimentos sobre sua precisão e a acurácia são necessários. O objetivo deste estudo foi estabelecer: a) precisão e acurácia de medidas lineares tridimensionais para osteotomia tipo Le Fort I obtidas por meio da tomografia computadorizada multislice (TCMS) e feixe cônico (TCFC) e b) comparar a precisão e acurácia de medidas lineares para osteotomia tipo Le Fort I realizadas por meio de três programas de imagem utilizando a 3D-TCFC. A amostra foi constituída por onze crânios secos submetidos à TCMS 64 canais e TCFC. As reconstruções tridimensionais (3D-TC) foram geradas, e medidas lineares (n=11) baseadas em estruturas e pontos anatômicos de interesse à osteotomia tipo Le Fort I foram realizados independentemente, por dois radiologistas experientes, duas vezes cada, utilizando programa Vítrea 3.8.1 em reconstruções 3D-TCMS e 3D-TCFC e os programas OsiriX 1.2 64-bit e Dolphin Imaging versão 11.5.04.35 por meio da 3D-TCFC. Sequencialmente, um terceiro observador experiente e calibrado, que não participou da análise das imagens, realizou as medidas sobre os crânios secos utilizando paquímetro digital (padrão ouro) com quais as medidas foram comparadas. A análise intra e inter-observadores assim como as correlações individuais de cada medida foram realizadas utilizando o coeficiente de correlação intra-classe (CCI), sendo o intervalo de confiança adotado de 95%. Os resultados demonstraram na análise intra-observador, utilizando o programa Vítrea, correlação excelente para todas as medidas variando de 0,87 a 0,96 e 0,82 a 0,98 para os observadores 1 e 2 respectivamente utilizando a TCMS e de 0,84 a 0,98 e 0,80 a 0,98 utilizando a TCFC. A análise inter-observadores variou de 0,85 a 0,98 para a TCMS e de 0,80 a 0,99 para a TCFC. A análise intra-observador utilizando os diferentes programas de imagem na TCFC apresentou variações de 0,90 a 0,97 (Vítrea), 0,65 a 0,97 (OsiriX) e 0,51 a 0,94 (Dolphin). Na análise inter-obsevador obtivemos valores de 0,92 a 0,99 e 0,88 a 0,98 para os observadores 1 e 2 respectivamente utilizando o Vítrea, 0,58 a 0,90 e 0,48 a 0,85 para o programa OsiriX e de 0,80 a 0,96 e 0,57 a 0,92 com o programa Dolphin. O programa Vítrea não apresentou diferenças estatisticamente significante nas análises intra e inter-observador e medidas físicas utilizando a TCMS e TCFC. Em relação à análise dos programas, diferenças estatisticamente foram constatadas com o programa OsiriX e Dolphin em relação ao padrão ouro. / The success of orthognathic surgery depends on many factors as precise and accurate facial analysis and high quality imaging exams. Nowadays a lot of commercial and open-source three-dimensional software programs currently available to assist diagnosis, elaboration of treatment planning, and to predict outcomes related to orthognathic surgery. The aim of this study was to establish: a) the precision and accuracy of three-dimensional linear measurements for Le Fort I osteotomy, obtained from multislice computed tomography (MSCT) and cone-beam computed tomography (CBCT) scans and b) compare the precision and accuracy of linear measurements for Le Fort I osteotomy performed by three different imaging software programs and obtained from 3D-CBCT images. The study population consisted of 11 dried skulls submitted to 64-row MSCT and CBCT scans. Three-dimensional reconstructed images (3D-CT) were generated, and linear measurements (n = 11) based on anatomical structures and landmarks of interest for Le Fort I osteotomy were performed independently by 2 oral and maxillofacial radiologists, twice each, using Vítrea 3.8.1 software for 3D-MSCT and 3D-CBCT and OsiriX 1.2 64-bit and Dolphin Imaging version 11.5.04.35 from 3D-CBCT. Subsequently, a third examiner expert in anatomical analysis and calibrated, who did not evaluate the images, performed measurements on dry skulls using a digital caliper (gold standard) with which the measurements were compared. The analyses of intra- and inter-observer as well as the individual correlations of each measurement were performed using the coefficient of intra-class correlation (ICC), with a confidence interval of 95 %. The intra-observer results showed that using the Vitrea program, excellent correlation for all measurements were reached with ICC values ranging from 0.87 to 0.96 and 0.82 0.98 for observers 1 and 2 respectively using the MSCT and 0.84 to 0.98 and 0.80 to 0.98 using CBCT. Inter-observer analysis ranged from 0.85 to 0.98 for MSCT and 0.80 to 0.99 for CBCT. The intra-observer analysis using the different programs using CBCT images varied from 0.90 to 0.97 for Vitrea, 0.65 to 0.97 for OsiriX and 0.51 to 0.94 using Dolphin. Inter-observer analysis demonstrated values ranging from 0.92 to 0.99 and 0.88 0.98 for observers 1 and 2 respectively using the Vitrea; 0.58 to 0.90 and 0.48 to 0.85 for OsiriX, and 0.80 to 0.96 and 0.57 to 0.92 using Dolphin. Vítrea software showed no statistically significant differences for intra-and inter-observer analysis and physical measurements using MSCT and CBCT. Regarding the analysis of softwares, statistical differences were found with the program OsiriX and Dolphin in comparison to gold standard.

Os dentes incisivos inferiores apresentam, em sua maioria, canal radicular único, que pode ter conformações distintas. De acordo com a literatura científica, a presença de um segundo canal radicular pode ser constatada em 10 a 40% dos casos. A não-detecção do segundo canal é um importante fator para o insucesso do tratamento endodôntico. Esta pesquisa foi realizada com os seguintes objetivos: 1) comparar a eficácia na identificação de padrões anatômicos internos em incisivos inferiores permanentes extraídos com uso de imagem radiográfica periapical digital e de tomografia computadorizada de feixe cônico (TCFC); e 2) determinar a prevalência de 2 canais radiculares em incisivos inferiores em imagens de TCFC de um banco de dados de exames previamente realizados, associando com localização do dente, gênero e idade do paciente. Na primeira etapa da pesquisa, 40 dentes incisivos inferiores foram submetidos a escaneamento em microtomógrafo computadorizado da FOB-USP (Skyscan 1074) para estabelecer o padrão ouro do tipo anatômico interno de cada dente. Os dentes foram então classificados em: Tipo I (1 canal radicular regular, n=12), Tipo Ia (1 canal radicular oval, n=12) e Tipo III (2 canais radiculares, n=16). Em seguida, os dentes foram divididos em 10 grupos de 4 dentes e posicionados em alvéolos de uma mandíbula humana para exposição radiográfica periapical digital direta com duas tomadas variando o ângulo horizontal de incidência (Schick CDR) e para escaneamento em 3 tomógrafos (Kodak 9000 3D, Veraviewepocs 3De e NewTom 5G) da Universidade de Loma Linda, CA, EUA. Dois examinadores treinados classificaram o tipo anatômico de cada dente e suas respostas foram comparadas ao padrão ouro estabelecido por microtomografia. Para descrição dos resultados, utilizou-se a porcentagem (%) de respostas certas / erradas. Aplicou-se o teste do qui-quadrado (X2), com nível de significância estatística de 5%, para verificação da associação entre variáveis. As concordâncias inter e intraexaminador foram determinadas por teste de kappa. Na segunda etapa da pesquisa, foram interpretadas imagens de incisivos inferiores de 100 pacientes, cujos exames estavam disponíveis no banco de dados do tomógrafo i-CAT Classic da FOB-USP. Dois examinadores avaliaram a anatomia interna de incisivos inferiores, em reconstruções axiais, sagitais e coronais, classificando-a de acordo com o número de canais radiculares. A prevalência de 2 canais radiculares foi relacionada à localização do dente e ao gênero e idade do paciente. Para descrição dos dados coletados, utilizou-se a porcentagem (%). Para verificar a associação entre variáveis, utilizou-se o teste do qui-quadrado (X2), com nível de significância estatística de 5%. Para a concordância intra e interexaminador, utilizou-se o teste de kappa. Como resultado da primeira etapa da pesquisa, obteve-se alto índice de detecção de tipos anatômicos para todos os métodos avaliados (p <0,05). Para dentes com Tipo I (1 canal radicular regular), as imagens de TCFC foram superiores em comparação à radiografia periapical digital com dupla exposição (RP= 67% de acerto; TCFC= 98% de acerto, p <0,05). Considerando os 3 aparelhos de TCFC, não houve diferença estatística significante entre eles para identificação do Tipo I. Já para dentes com Tipo Ia (1 canal radicular oval), houve diferença estatística significante somente entre radiografia periapical digital com dupla exposição e o tomógrafo NewTom (RP= 44% de acerto; TCFC NewTom= 88% de acerto). Não houve diferença significante entre os outros 2 tomógrafos e radiografia periapical ou entre os 3 tomógrafos. Considerando dentes com Tipo III (2 canais radiculares), não houve diferença estatística significante entre nenhum dos métodos. Todos os métodos apresentaram números de respostas certas semelhantes para o Tipo III, sugerindo que a radiografia periapical com dupla angulação é suficiente para identificação de 2 canais radiculares em incisivos inferiores. A concordância intraexaminador para radiografia periapical foi regular (kappa=0,40 a 0,66) e de boa a excelente para os aparelhos de TCFC (kappa=0,62 a 0,85). A concordância interexaminador para radiografia periapical foi de ruim a regular (kappa=0,25 a 0,32) e de boa a excelente para os aparelhos de TCFC (kappa=0,62 a 0,92). Na segunda etapa da pesquisa, o total de 386 incisivos inferiores foi avaliado, sendo 192 incisivos centrais e 194 incisivos laterais. A prevalência de 2 canais radiculares constatada no total de dentes foi de 16,5%, sendo de 13% em incisivos centrais e de 20% nos incisivos laterais (p >0,05). Não houve diferença estatisticamente significante entre gêneros e idades. A concordância intra e interexaminador foi regular (kappa intra=0,60; kappa inter=0,57). Como conclusão da primeira etapa da pesquisa, observou-se que a identificação do número de canais radiculares foi efetiva em todos os métodos. No entanto, limitações foram encontradas para a diferenciação da forma do canal radicular. Na segunda etapa da pesquisa, concluiuse que a presença de 2 canais radiculares em incisivos inferiores de pacientes da região de Bauru é de aproximadamente 20% e não depende da localização do dente ou de gênero e idade do paciente. / Mandibular incisors most commonly have a single root canal, which can present with different anatomic configurations. According to the literature, the presence of a second root canal can be observed in 10 - 40% of the teeth. Difficulty in detecting the second root canal is an important factor for the endodontic treatment failure. The aim of this research was: 1) to compare the efficacy of digital periapical radiography (PA) with double exposure and cone beam computed tomography (CBCT) in the identification of internal anatomic patterns in mandibular incisors, and 2) to determine the prevalence of 2 root canals in mandibular incisors using cone beam computed tomographic images of a patient database, comparing to tooth position and patients gender and age. In the first part of this research, 40 extracted mandibular incisors underwent microcomputed tomographic (micro-CT) scanning (Skyscan 1074) in order to establish the gold standard for internal anatomic pattern. The teeth were classified according to: Type I (1 regular root canal, n=12), Type Ia (1 oval root canal, n=12), and Type III (2 root canals, n=16). Then, the teeth were divided into 10 groups of 4 teeth and placed in a preserved human mandible for direct digital periapical radiographic double exposure (Schick CDR) and CBCT scans using Kodak 9000 3D, Veraviewepocs 3De and NewTom 5G. Two blinded examiners classified the anatomic pattern of each tooth and their answers were compared to the gold standard (microtomographic images). Percentage (%) of right / wrong answers was used for the statistical analysis of the results. Chi-square test (X2) was used to verify the association between variables (p <.05). Inter and intraexaminer agreements were determined using kappa values. In the second part of this research, CBCT images of a 100 patients database from FOB-USP were examined. Two examiners assessed the internal anatomy of mandibular incisors in axial, sagittal and coronal reconstructions and classified the teeth according to the number of root canals. The prevalence of 2 root canals was related to the tooth location and patients gender and age. Percentage (%) was used to describe the collected data. Chi-square test (X2) was used to verify the association between variables (p <.05). Inter and intraexaminer agreements were determined using kappa values. The results of the first part of the research showed a high level of identification of anatomic patterns for all the methods (p <0.05). Considering Type I (1 regular root canal), CBCT images were better in comparison to PA (PA= 67%; CBCT= 98%, p <0.05). There was no significant difference between the 3 CBCT scanners. For Type Ia (1 oval root canal), there was a significant difference between PA and CBCT imaging using the NewTom unit only (PA= 44%, NewTom CBCT= 88%). No significant differences were found between the other 2 CBCT units and PA or between the 3 CBCT units. Considering Type III (2 root canals), there was no significant difference between the various methods. All the methods presented similar corrected answers index for Type III, which may suggest that PA with double exposure is sufficient for the identification of 2 root canals in mandibular incisors. The intraexaminer agreement was fair for PA (kappa=0.40 to 0.66) and good to very good for the CBCT units (kappa=0.62 to 0.85). The interexaminer agreement was poor to fair for PA (kappa=0.25 to 0.32) and good to very good for CBCT units (kappa=0.62 to 0.92). In the second part of this research, the total amount of 386 mandibular incisors was assessed in CBCT images (192 mandibular central incisors and 194 mandibular lateral incisors). The overall prevalence of 2 root canals was 16.5%, and 13% in mandibular central incisors and 20% in mandibular lateral incisors (p >0.05). There was no significant difference between gender and age. The intra and interexaminer agreement was fair (kappa intra=0.60; kappa inter=0.57). For the first part of this research, it is possible to conclude that the identification of the number of root canals was effective using all the methods. However, limitations were found in differentiating the shape of the root canal. As a conclusion of the second part of this research, the presence of 2 root canals in mandibular incisors of Bauru region patients is approximately 20% and it does not depend on tooth location or patients gender and age.

Computed tomography angiography (CTA) of the brain poses challenges on the imaging system; the contrast between blood vessels and surrounding soft tissue is very low, and to render small intricate vessel structures high spatial resolution is needed. Higher precision angiography would facilitate more accurate diagnosis of pathological conditions. The aim of this work was to analyze the factors which contribute to the image quality in cerebrovascular imaging contexts and make a comparison between state-of-the-art energy-integrating and photon counting CT systems. A geometrical model was devised to mimic the conditions of cerebral angiography. Different parameters and detectors were used to reconstruct images of a spherical head phantom. Compton noise was added to several image acquisitions after a Monte Carlo study was used to estimate the scatter to primary ratio (SPR) with a spherical phantom. The images were evaluated qualitatively and quantitatively. A real phantom was scanned with an experimental photon counting detector and compared with the simulated approach. The work resulted in qualitative reconstructed images, a decrease in SPR when introducing air gaps and improved resolution but worsened contrast as a result of smaller detector sizes. The SPR was shown to be higher in cone-beam geometry than fan-beam geometry. Electronic noise present with energy integrating detectors was shown to degrade image quality significantly in low dose imaging, reducing contrast when imaging vascular-like structures. Photon counting detectors without electronic noise could provide greater image quality and better diagnostic information.

Published Article / Rapid Manufacturing (RM) has emerged over the past few years as a potential technology to successfully produce patient-specific implants for maxilla/facial and cranial reconstructive surgeries. However, in the area of spinal implants, customization has not yet come to the forefront and with growing capabilities in both software and manufacturing technologies, these opportunities need to be investigated and developed wherever possible. The possibility of using Computed Tomography (CT) and Rapid Manufacturing (RM) technologies to design and manufacture a customized, patient-specific intervertebral implant, is investigated. Customized implants could aid in the efforts to reduce the risk of implant subsidence, which is a concern with existing standard implants. This article investigates how accurately the geometry of a customized artificial intervertebral disc (CAID) can represent the inverse geometry of a patient's vertebral endplates. The results indicate that the endplates of a customized disc implant can be manufactured to a calculated average error of 0.01mm within a confidence interval of 0.022mm, with 95% confidence, when using Direct Metal Laser Sintering.

PEPT (positron emission particle tracking) is a technique for tracking a small radioactive tracer in Lagrangian co-ordinates. The technique was used to study the flow patterns of non-Newtonian CMC (Carboxy Methyl Cellulose) solutions inside a vessel agitated by an axial flow impeller. The 'non-intrusive' PEPT technique uses two position-sensitive detectors to track a radioactive particle in space and time. The particle is labelled with a positron emitting isotope. Once emitted from the nucleus a positron annihilates with an electron releasing energy in the form of two 511 keV back-to-back gamma-rays travelling in opposite directions, 180 degrees apart. The tracer particle is introduced into the stirred vessel which is mounted between the two detectors of the positron camera. Three axial flow impellers produced by Lightnin Mixers Ltd were used to carry out the experiments. Results showed that the discharge from the three impellers was radial when agitating non-Newtonian viscous solutions of CMC. Trajectory analysis was used to compare the performance of the impellers using the agitation index and the efficiency of circulation. A limited number of experiments was carried out to compare the effect of baffles on the circulation of the fluids in a mixing tank. The results showed that mixing of these non-Newtonian liquids in an unbaffled tank is better than in a baffled tank when using axial flow impellers. Other experiments were carried out to suspend solid particles in viscous fluids. Results showed that the minimum speed required to suspend large particles is lower than that required to suspend small particles. There are many correlations and models in the literature to determine the minimum speed required to suspend all the particles in a fluid; some of these correlations and models were compared with experimental results from this work. The correlation of Zweitering (1958) agreed with experimental data after modification. The Geisler et al. (1993) model agreed with the data provided that the power consumption is correctly substituted. The last part of this work concerned the flow of non-Newtonian viscous materials through industrial equipment. Yoghurt was chosen as the test fluid as one of the companies sponsoring this project was Eden Vale, a yoghurt manufacturer. A method was proposed using rheological measurements to simulate the flow through the dispensing pipeline and distributing nozzles; this method allows the designer to predict the final properties of yoghurt after passing through the paching head. Measurements were also carried out to determine the final gel structure of yoghurt in the delivery pots. This data of this thesis is useful in designing stirred tanks when non-Newtonian fluid is present, either for agitation or when suspending solids. Also, a method was provided to design yoghurt manufacturing line.

The dependence of tumour growth and metastasis on blood vessels makes tumour angiogenesis a rational target for therapy. Imaging of αvβ3 expression could potentially be used as a biomarker and an early indicator of efficacy of antiangiogenic treatments at a molecular level. Research efforts have mainly focused on the development of RGD-based radiolabelled αvβ3 inhibitors suitable for PET and SPECT imaging modalities that, owing to their high sensitivity, represent the most powerful tool for monitoring in vivo tumour angiogenesis. The aim of this multidisciplinary project was the design, synthesis and biological evaluation of novel αvβ3 ligands as molecular imaging probes. Three classes of integrin antagonists were designed: 1) triazole-based RGD mimetics that can be isotopically-labelled with tritium, fluorine and iodine radioisotopes by means of highly practical procedures, 2) RGD peptidomimetics incorporating the metabolically stable 2,2,2-trifluoroethylamine function as a peptide bond bioisostere and 3) RGD cyclopeptides conjugated with FDR, a novel prosthetic group allowing glycosylation and 18F-fluorination of aminooxy-functionalised molecules in one synthetic step. RGD-based strategies have also been used for selective tumour delivery of chemotherapeutic agents. A number of cytotoxic drugs have been conjugated to RGD peptides, providing experimental evidence that αvβ3 targeted chemotherapy strategies could be used as a powerful tool to reduce the toxicity and augment the therapeutic window of existing cytotoxic agents. In this work, we described the rational design of a novel targeted cytotoxic conjugate containing a triazole-based RGD peptidomimetic as tumour-homing motif of the potent antimitotic agent, paclitaxel. Preliminary in vitro studies were performed to assess the therapeutic potential of this targeted cytotoxic construct.

Thesis (MScMedSC (Medical Imaging and Clinical Oncology. Nuclear Medicine))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Single photon emission computed tomography (SPECT) with a superior contrast resolution has been shown to be more sensitive and specific with a lower nondiagnostic rate than planar imaging in many nuclear medicine studies but it is still not being routinely implemented in V/Q studies at many centres including Tygerberg Hospital. There are many studies on V/Q SPECT using Technegas as a ventilation agent but very limited studies available on 81m Kr gas. Aim: To clinically compare conventional planar and SPECT V/Q imaging using 81mKr gas in the diagnosis of pulmonary embolism, with CTPA as the gold standard. Patients and Methods: All patients referred with clinical suspicion of pulmonary embolism were assessed. The inclusion criteria were normal chest radiograph, normal renal function and no contrast allergy. Exclusion criteria were age below 18 years old, pregnancy, abnormal chest radiograph, abnormal serum creatinine/urea levels and unstable patients. A Well’s score was assigned to each enrolled patient. Perfusion scintigraphy was performed after intravenous injection 125 MBq of 99mTc MAA. Ventilation scintigraphy was performed with 81mKr gas. On a dual head camera, SPECT was done before planar acquisition, while perfusion was done before ventilation imaging in the same position. Planar V/Q images consisted of 6 standard views. All V/Q SPECT images were reconstructed using ordered-subset expectation-maximization (OSEM) algorithm and a post-reconstruction 3D Butterworth filters were applied. V/Q Planar and V/Q SPECT images were later evaluated and reviewed separately and reported based on recent EANM guidelines blinded to the CTPA results. All patients underwent multi-slice CTPA examinations on a 40-detector row scanner. The images were later assessed and reported blinded to the V/Q results. Statistical analysis was done using the Fisher exact test for comparison of categorical variables and the one-way ANOVA for continuous variables (p<0.05 was significant). Results: A total of 104 consecutive patients were referred with clinical suspicion of pulmonary embolism. Seventy-nine patients were excluded from this study mostly due to abnormal serum creatinine/urea levels. Only 25 patients were included in this study, with a mean age of 48 ± 19 years, and 64% being females. When compared to CTPA as gold standard, the prevalence of PE was 16% [5% – 37% at 95% CI], sensitivity 75% [21% – 99% at 95% CI], specificity 90% [68% – 98% at 95% CI], positive predictive value 60% [17% – 93% at 95% CI], negative predictive value 95% [73% – 100% at 95% CI] and diagnostic accuracy 88% [69% – 97%at 95% CI] for both V/Q Planar and SPECT. V/Q Planar showed a lower reader confidence i.e. could only clearly resolve 72% of cases compared to V/Q SPECT, which could precisely interpret all cases, showed more and better delineated mismatch vs match and segmental vs non-segmental defects. All patients who were scored as PE unlikely on Wells’ score (4) had PE ruled out on CTPA (p=0.04581) as well as 89% of patients on V/Q SPECT and V/Q Planar. Conclusion: Based on this study, V/Q Planar and V/Q SPECT have a similar diagnostic performance in patients with a normal or near normal chest X-rays. / AFRIKAANSE OPSOMMING: Enkelfoton emissie rekenaartomografie (EFERT) met beter kontrasresolusie is bewys om meer sensitief en spesifiek met ‘n laer nie-diagnostiese opbrengs as planare beelding in verskeie kerngeneeskunde ondersoeke te wees. In Tygerberg Hospitaal, soos in verskeie ander sentra, word dit egter steeds nie roetineweg vir ventilasie-perfusiestudies (V/Q) geïmplementeer nie. Daar is verskeie EFERT V/Q studies met Technegas as ventilasie agens, maar beperkte studies met 81m Kr gas beskikbaar. Doel: Om konvensionele planare en EFERT V/Q beelding vir die diagnose van pulmonale embolisme met mekaar te vergelyk, met rekenaartomografie pulmonale angiografie (RTPA) as goue standaard. Pasiënte en Metodes: Alle pasiënte wat met ‘n kliniese vermoede van pulmonale embolisme verwys is, is geevalueer. Die insluitingskriteria was ’n normale borskas Xstraal, normale nierfunksie en geen kontrasallergie nie. Uitsluitingskriteria was pasiënte jonger as 18 jaar, swanger pasiënte, abnormale borskas X-straal, abnormale serum kreatinien / ureumvlakke en onstabiele pasiënte. ’n Wells telling is vir elke pasiënt wat in die studie ingesluit is, bepaal. Perfusiebeelding is uitgevoer na die intraveneuse toediening van 125 MBq 99mTc MAA. Ventilasiestudies is gedoen met 81mKr gas. Die V/Q EFERT studies is voor die planare beelding met ’n dubbelkop gammakamera uitgevoer. Perfusiebeelding is voor die ventilasie in dieselfde posisie verkry. V/Q planare beelding het bestaan uit 6 standaard beelde. Alle V/Q EFERT is met “ordered-subset expectationmaximization” (OSEM) algoritmes verwerk, en post-rekonstruksie 3D Butterworth filters is toegepas. V/Q planare en V/Q EFERT beelding is later afsonderlik en sonder RTPA inligting volgens onlangse EANM riglyne evalueer en gerapporteer. ‘n Veelsnit RTPA met ‘n 40 snit skandeerder is op alle pasiënte uitgevoer. Die beelde is later beoordeel en gerapporteer sonder inagneming van die V/Q beeldingsresultate Statistiese verwerking is gedoen met die Fisher presisietoets vir vergelyking van kategoriese veranderlikes en die eenrigting ANOVA vir kontinue veranderlikes (p<0.05 is statisties betekenisvol). Resultate: ‘n Totaal van 104 opeenvolgende pasiënte met ‘n kliniese vermoede van pulmonale embolisme is verwys. Nege-en-sewentig pasiënte is uitgesluit, in die meeste gevalle as gevolg van abnormale serum kreatinienvlakke. Slegs 25 pasiënte is ingesluit, met ’n gemiddelde ouderdom van 48 ± 19 jaar, en 64% vroue. In vergelyking met RTPA as goudstandaard, was die prevalensie van PE 16% [5% – 37% met 95% VI], sensitiwiteit 75% [21% – 99% met 95% VI], spesifisiteit 90% [68% – 98% met 95% VI], positiewe voorspellingswaarde 60% [17% – 93% met 95% VI], negatiewe voorspellingswaarde 95% [73% – 100% met 95% VI] en diagnostiese akkuraatheid van 88% [69% – 97% met 95% VI] vir beide planare en EFERT V/Q beelde. V/Q planare beelde het ‘n laer lesersvertroue getoon, nl. dat slegs 72% van gevalle opgelos kon word relatief tot V/Q EFERT beelde, wat in alle gevalle presies geïnterpreteer kon word, met meer en beter omskrewe nie-ooreenstemmende teenoor ooreenstemmende en segmentele teenoor nie-segmentele defekte. In alle pasiënte met ‘n Wells puntetelling van 4 is PE met die RTPA uitgeskakel (p=0.04581), terwyl dit in 89% van pasiënte met V/Q EFERT en planare beelde uitgeskakel is. Gevolgtrekking: Gebaseer op hierdie studie het V/Q planare en EFERT beelding ‘n ooreenstemmende diagnostiese prestasie in pasiënte met ’n normale of naby normale borskas X-straal.

ENGLISH ABSTRACT: Background: The detection of bone infection can be very difficult especially in bone with altered structure due to prior trauma or surgical procedures. Complicated osteomyelitis (COM) is becoming a public health problem especially with the difficult choice between, high cost surgery and prolonged courses of intravenous or oral antibiotic therapy, as well as the social and psychological effect of longterm disease and disability of the patient. The correct localisation of especially bone infection is still a challenge for the clinician. The single photon emission computed tomography/low dose computed tomography (SPECT/CT), by fusing the functional information with the anatomical parts, is a wellestablished tool used in many nuclear medicine studies. This improves the overall quality of the study with more clear answers. The aim of the study was to determine the added value of SPECT/CT in the management of complicated osteomyelitis (COM) in patients with endo-prosthesis, post traumatic osteomyelitis with and without metal implants and diabetic foot. Methods: This was a prospective study, between February 2010 and February 2012. Patients with suspected COM who fulfilled the selection and inclusion criteria were included. All had abnormal three phase bone scan followed by infection imaging with 99mTc labelled white blood cells and 99mTc -colloid if the99mTc labelled white blood cell study was abnormal. 67Ga citrate was used in vertebral involvement. Planar and SPECT/CT images were reviewed for presence of abnormal uptake and for its localization in bone and soft tissue. Scan results were defined as positive or negative. Both planar and SPECT/CT images were compared regarding diagnosis and precise localization of infection. The final diagnosis was obtained from surgical specimen or microbiological culture as well as clinical follow-up of all patients. Results: There were 72 patients, 29 male and 43 female with mean age of 57 yrs [range 27-88].There were 24 patients with prosthesis, 16 with hip prosthesis (PH=16), and 8 with knee prosthesis (PK=8). There were 44 patients with post traumatic osteomyelitis, 26 with metal implants (TOM=26) and 18 without metal implants (TOWM= 18). Four patients had diabetic foot (DF= 4). Infection was diagnosed in 19/72 patients on planar images and in 21/72 on SPECT/CT. Infection was diagnosed in 4 patients with prosthesis, 16 patients with post traumatic injury and one diabetic foot patient. The four patients with prosthesis, SPECT /CT added diagnostic value by excluding osteomyelitis in 3 patients and by defining the exact extent and localizing soft tissue and bone infection (STI/OM) in one patient. In 16 patients with post traumatic OM on planar images, SPECT /CT added diagnostic value, by excluding OM in 4 patients and confirming only STI, better localisation of the uptake in bone and soft tissue in 5 patients, of them 2 patient was negative on planar, and in 7 patients, confirmed and defined the exact extent of both OM and STI. One diabetic foot was positive for STI on the planar, the SPECT/CT added diagnostic value by defining the extent of the infection. In summary the added value of SPECT/CT was: a. Overall infection: 1. Exclusion of osteomyelitis by confirming only soft tissue involvement: 7 patients (10%) 2. Better localization in bone and soft tissue: 6 patients (8%) 3. Better delineation of extent of infection: 9 patients (12%) 4. None: 50 patients (70%) b. In positive cases only: 1. Exclusion of osteomyelitis by confirming only soft tissue involvement: 7 patients (33%) 2. Better localization in bone and soft tissue: 5 patients (24%) 3. Better delineation of extent of infection: 9 patients (43%) 4. None: 0 patients The overall sensitivity, specificity, positive predictive value, negative predictive value and accuracy for infection, on planar was 90%, 100%, 100%, 97%, 97%, respectively and for SPECT/CT 100%, 100%, 100%, 100%, 100%. For OM on planar, the sensitivity, specificity , positive predictive value, negative predictive value and accuracy was 100%, 89%, 53%, 100%, 90%, respectively and for SPECT/CT 100%, 100%, 100%, 100%, 100%. Conclusion: In complicated osteomyelitis, SPECT/CT is useful in localizing, defining the exact extent of infection where the planar images are abnormal, with no added value if the planar images are negative. We recommend in clinical practice the routine use of hybrid SPECT/CT imaging in complicated osteomyelitis when planar images are abnormal. / AFRIKAANSE OPSOMMING: Agtergrond: Die opspoor van beeninfeksie is veral moeilik in been wat as gevolg van vorige trauma of chirurgiese prosedures misvorm is. Gekompliseerde osteomiëlitis word ‘n gesondheidsprobleem veral as gevolg van die moeilike keuse tussen hoë koste chirurgie en langdurige kursusse binneaarse of orale antibiotika, asook die sosiale en sielkundige gevolge van langstaande siekte en die gestremdheid van die pasiënt. Die korrekte lokalisering van veral beeninfeksie is steeds ‘n uitdaging vir die geneesheer. Enkel foton emissie rekenaartomografie / lae dosis rekenaartomografie (SPECT/CT), die kombinasie van funksionele en anatomiese inligting, is ‘n goed gevestigde metode in baie kerngeneeskunde ondersoeke. Dit verbeter die algemene kwaliteit van die studie met ‘n meer spesifieke antwoord. Die doel van hierdie studie was om die bykomende waarde van SPECT/CT in die hantering van gekompliseerde osteomiëlitis in pasiënte met endo-protese, post traumatise osteomiëlitis met en sonder metaal prosteses asook diabetiese voet te bepaal. Metode: ‘n Prospektiewe studie is tussen Februarie 2010 en Februarie 2012 gedoen. Pasiënte met vermoedelik gekompliseerde osteomiëlitis wat aan die keuse en insluitingskriteria voldoen het, is ingesluit. Almal het abnormale drie-fase beenflikkergramme gehad, gevolg deur infeksiebeelding met 99mTc gemerkte witselle en 99mTc kolloïed indien die 99mTc gemerkte witselstudie abnormaal was. 67Ga sitraat is gebruik wanneer daar werwelaantasting teenwoordig was. Die planare en SPECT/CT beelde is vergelyk ten opsigte van diagnose en presiese lokalisering van die infeksie. Die finale diagnose is met behulp van chirurgiese monsters en mikrobiologiese kweking asook die kliniese opvolg van alle pasiënte bepaal. Resultate: Die studie het 72 pasiënte, 29 mans en 43 vroue, met gemiddelde ouderdom van 57 jaar [27 – 88 ingesluit]. Daar was 24 pasiënte met prosteses, waarvan 16 met heupprosteses (PH= 16) en 8 met knieprosteses (PK= 8). Van die 44 pasiënte met post traumatiese osteomiëlitis, het 26 metaal prosteses (TOM= 26) en 18 geen metaalprosteses gehad nie (TOWM= 18). Vier pasiënte het diabetiese voet gehad (DF= 4). By 19/72 van die pasiënte is infeksie op die planare beelde gediagnoseer en in 21/72 op die SPECT/CT beelde. Die bykomende twee gevalle was 1 met TOM en 1 met TOWM. Infeksie is by 4 pasiënte met prosteses, 16 pasiënte met post traumatiese besering en 1 met diabetiese voet gediagnoseer. In die vier pasiënte met prosteses, het SPECT/CT ‘n diagnostiese bydrae gelewer om osteomiëlitis by 3 van die pasiënte uit te skakel en die presiese omvang en lokalisering van sagte weefsel en beeninfeksie (STI/OM) in een pasiënt te bepaal. In 16 pasiënte met post traumatise osteomiëlitis op die planare beelde, was SPECT/CT van diagnostiese waarde, waar osteomiëlitis in 4 pasiënte uitgesluit is, en slegs STI bevestig is. Beter lokalisering van die opname in been en sagte weefsel was in 5 pasiënte moontlik, van wie 2 op die planare beelde negatief was, en in 7 pasiënte bevestig en die presiese omvang met beide OM en STI gedefinieer is. Een diabetiese voet was positief vir STI op die planare beelde, maar die SPECT/CT het diagnostiese waarde verbeter deur die omvang van die infeksie beter te toon. Ter opsomming, was die waarde van die SPECT/CT: 1. Uitsluiting van osteomiëlitis deur slegs van sagte weefsel aantasting te bevestig: 7 pasiënte 10% 2. Beter lokalisering in been en sagte weefsel: 5 pasiënte 7% 3. Beter definisie van omvang van infeksie: 9 pasiënte 12% 4. Geen bykomende waarde: 51 pasiënte 71% Die algehele sensitiwiteit, spesifisiteit, positiewe voorspellingswaarde, negatiewe voorspellingswaarde en akkuraatheid vir die opspoor van infeksie vir die planare beelde was 90%, 100%, 100%, 97%, 97%, onderskeidelik en vir die SPECT/CT 100%, 100%, 100%, 100% en 100%. Vir osteomiëlitis was sensitiwiteit, spesifisiteit, positiewe voorspellingswaarde, negatiewe voorspellingswaarde en akkuraatheid van planare beelde 100%, 89%, 53%, 100%, 90%, onderskeidelik en die van SPECT/CT 100%, 100%, 100%, 100% , 100%. Gevolgtrekking: SPECT/CT is nuttig in die lokalisering en definiëring van die presiese omvang van die infeksie in gekompliseerde osteomiëlitis in gevalle waar die planare beelde abnormaal is, met geen bykomende waarde wanneer planare beelde negatief is nie. Ons beveel SPECT/CT beelding as roetine in kliniese praktyk aan wanneer planare beelde in gekompliseerde osteomiëlitis abnormaal is.

Austenitic stainless steels are frequently used for engineering applications in aggressive environments. Typical sources of component failures are associated with localized attack at grain boundaries, such as intergranular corrosion and stress corrosion cracking. To prevent premature failures, structural integrity assessments are carried out, with the aim of predicting the maximum likelihood of cracking that may develop. For accurate predictions it is of great importance to know the interaction of parameters involved in life-determining processes. This PhD thesis investigates the effect of microstructure and stress on intergranular stress corrosion cracking in Type 302 / Type 304 austenitic stainless steels. High-resolution X-ray tomography has been successfully applied to examine, for the first time in 3-dimensions, in-situ, the interaction between microstructure and crack propagation. The development and subsequent failure of crack bridging ligaments has been observed and correlated with regions of ductile tearing persistent on the fracture surface. These ductile regions were consistent with the morphology of low-energy, twin-type grain boundaries, and are believed to possess the capability of shielding the crack tip. Following this observation, a new grain bridging model has been developed, in order to quantify the effect of static stress and crack bridging on the maximum likely crack length. The model was compared and evaluated with in the literature available percolation-like models. Intergranular stress corrosion tests in tetrathionate solutions have been designed and carried out to validate the new model. The assessment comprised,(i) a thorough examination of the microstructure and analysis parameters employed,(ii) the determination of the degree of sensitisation with subsequent crack path investigations,(iii) the identification of a suitable test system with associated grain boundary susceptibility criteria,(iv) the application of Grain Boundary Engineering (GBE) for microstructure control,(v) statistical crack length assessments of calibrated IGSCC test specimens. The results of these tests showed that the new model successfully predicts the magnitude of stress and the effect of grain boundary engineering on the maximum crack lengths.

Η υπολογιστική τομογραφία θώρακος αποτελεί την απεικονιστική τεχνική επιλογής για την διάγνωση και την ποσοτικοποίηση των διάμεσων νοσημάτων του πνεύμονα (1). Η διάγνωση όμως τέτοιων παθολογιών χαρακτηρίζεται από μεγάλη ένδο- και μεταξύ παρατηρητών μεταβλητότητα λόγω της μη ύπαρξης κριτηρίων του απεικονιστικού προτύπου των παθολογιών καθώς και του μεγάλου όγκου δεδομένων της εξέτασης. Για τον λόγο αυτό στην βιβλιογραφία έχει προταθεί η χρήση συστημάτων αυτόματης ποσοτικοποίησης με σκοπό την ακριβή μέτρηση των παθολογιών η οποία έως σήμερα πραγματοποιείται με ημι-ποσοτικές κλίμακες. Τα συστήματα αυτά λειτουργούν είτε σε επίπεδο τομής (2Δ) είτε σε ολόκληρο των όγκο (3Δ) του πνευμονικού πεδίου. Τα 3Δ συστήματα υπερτερούν τον 2Δ καθώς καλύπτουν το σύνολο του όγκου των πνευμονικών πεδίων περιορίζονται όμως λόγο της μειωμένης ποιότητας εικόνας (2-4). Τα συστήματα ποσοτικοποίησης αποτελούνται (συνήθως) από δύο στάδια προ-επεξεργασίας τα οποία προηγούνται του σταδίου ποσοτικοποίησης των παθολογιών. Τα στάδια προ-επεξεργασίας στοχεύουν στην απομόνωση του πνευμονικού παρεγχύματος. Ειδικότερα στο πρώτο στάδιο πραγματοποιείται απομόνωση των πνευμονικών πεδίων ενώ στο δεύτερο στάδιο πραγματοποιείται η αφαίρεση του αγγειακού δένδρου με αποτέλεσμα την απομόνωση του πενυμονικού πεδίου φυσιολογικού η μη. Η επίδραση των δύο βημάτων προ-επεξεργασίας είναι καθοριστική στην ακρίβεια του συστήματος ποσοτικοποίησης όπως έχει διατυπωθεί στην βιβλιογραφία. Τα συστήματα ποσοτικοποίησης που έχουν προταθεί έως σήμερα υιοθετούν σαν τεχνικές τμηματοποίησης πνευμονικών πεδίων είτε τεχνικές κατωφλίωσης σε συνδυασμό με μορφολογική επεξεργασία (2) είτε συνδυασμό τεχνικών που βασίζονται στην ανάλυση υφής περιοχής (5-8). Στα πλαίσια τμηματοποίησης των πνευμονικών πεδίων έχει προταθεί μια σειρά αλγορίθμων ικανή να τμηματοποίηση πνευμονικά πεδία χωρίς παρουσία παθολογιών ή με την παρουσία μικρών όγκων (οζιδίων) (9-14) ενώ μόλις πρόσφατα προτάθηκαν τεχνικές τμηματοποίησης οι οποίες στοχεύουν στην τμηματοποίηση πνευμονικών πεδίων με παρουσία διάχυτων ασθενειών του πνεύμονα (3) (15). Στην εικόνα 2 παρουσιάζονται τόσο φυσιολογικά όσο και παθολογικά πνευμονικά πεδία. Στην περίπτωση των παθολογικών πνευμονικών πεδίων είναι φανερό πως η τμηματοποίηση υπό την παρουσία προτύπων διάχυτων νοσημάτων δεν είναι «εύκολη αποστολή» καθώς τα πρότυπα της παθολογίας και ο περιβάλλον ιστός μοιράζονται κοινά απεικονιστικά χαρακτηριστικά. Λεπτομερής περιγραφή των αλγορίθμων τμηματοποίησης θα πραγματοποιηθεί στα επόμενα κεφάλαια. Στην υπολογιστική τομογραφία το σήμα (προβολές) που καταγράφεται στους ανιχνευτές χαρακτηρίζεται από παρουσία θορύβου, φαινόμενο που κυρίως οφείλεται στην τυχαιότητα απορρόφησης των φωτονίων στους ανιχνευτές. Ο θόρυβος αυτός γενικότερα αναφέρεται ως κβαντικός θόρυβος. O θόρυβος μέσω της διαδικασίας ανακατασκευής εικόνας κληροδοτείται και στη τελική εικόνα. Ο θόρυβος αυτός μπορεί να μειωθεί είτε αυξάνοντας τα στοιχεία λήψης (υψηλότερη δόση), είτε εφαρμόζοντας τεχνικές ανακατασκευής οι οποίες χρησιμοποιούν πυρήνες εξομάλυνσης (smoothing kernel).΄Όμως, λαμβάνοντας υπόψη τη βασική αρχή ακτινοπροστασίας ALARA (As Low As Reasonable Achievable) τα στοιχεία λήψης πρέπει να είναι όσο το δυνατόν χαμηλότερα. Κάνοντας όμως χρήση του πυρήνα εξομάλυνσης μειώνεται η διακριτική ικανότητα εικόνας. Αυτό φανερώνει ότι η μείωση θορύβου δεν είναι ένα τετριμμένο πρόβλημα. Με εικόνες που χαρακτηρίζονται από υψηλό SNR (σήμα προς θόρυβο) μπορεί να επιτευχθεί ακριβής διάγνωση αλλά και να αξιοποιηθούν στα πλαίσια τεχνικών ανάλυσης εικόνας όπως τεχνικές αντιστοίχισης και τμηματοποίησης [1]. Όπως προαναφέραμε τα 3Δ πρωτόκολλα χαρακτηρίζονται από μειωμένη ποιότητα εικόνας λόγω παρουσίας θορύβου σε σχέση με τα 2Δ πρωτόκολλα υψηλής ανάλυσης Έως τώρα στη βιβλιογραφία έχουν προταθεί πολλές τεχνικές για μείωση θορύβου στην υπολογιστική τομογραφία. Για παράδειγμα έχουν χρησιμοποιηθεί επαναληπτικές τεχνικές ανακατασκευής οι οποίες αποσκοπούν στην μείωση θορύβου, μέσω της βελτιστοποίησης στατιστικών συναρτήσεων [2]-[4]. To βασικό μειονέκτημα αυτών των τεχνικών είναι η υψηλή υπολογιστική πολυπλοκότητα (high computational complexity). Η εφαρμογή αλγορίθμου μείωσης θορύβου μετά την ανακατασκευή εικόνας (post-processing) αποτελεί πρόκληση κυρίως λόγω του χαρακτήρα του θορύβου στην ανακατασκευασμένη εικόνα. Επιπλέον η κατευθυντικότητα του θορύβου λόγω υψηλής απορρόφησης κατά μήκος συγκεκριμένων κατευθύνσεων καθιστά τη διαφοροποίηση μεταξύ δομών και θορύβου ιδιαίτερα πολύπλοκη. Μια πολύ βασική αρχή στην οποία θα πρέπει να υπακούει κάθε τεχνική μείωσης θορύβου που εφαρμόζεται σε ιατρικές εικόνες είναι ότι η κλινική πληροφορία της εικόνας πρέπει να διατηρείται. Οι πιο πρόσφατες τεχνικές που σχετίζονται με την μείωση θορύβου στις ανακατασκευασμένες εικόνες χρησιμοποιούν τεχνικές οι οποίες αφαιρούν το θόρυβο αλλά ταυτόχρονα διατηρούν τις αιχμές της εικόνας (16). Χαρακτηριστικό ιδιαίτερα χρήσιμο στην περίπτωση των περίπλοκων απεικονιστικών προτύπων τις διάχυτης παθολογίας του πνεύμονα όπως το γραμμικό δικτυωτό πρότυπο τις πνευμονικής ίνωσης το οποίο μπορεί να συνυπάρχει με το πρότυπο της θαμβή υάλου το οποίο δεν περιέχει δομές αλλά εύκολα συγχέεται με το φυσιολογικό πνευμονικό παρέγχυμα παρουσία θορύβου. Ανοικτό ζήτημα στην βιβλιογραφία αποτελεί η τμηματοποίηση των πνευμονικών πεδίων, ιδιαίτερα στην περίπτωση όπου η παθολογία επηρεάζει τα όρια αυτών. Οι τεχνικές που έχουν προταθεί έως σήμερα εστιάζουν στην εφαρμογή των αλγορίθμων σε δεδομένα τα οποία έχουν προέλθει από τον ίδιο υπολογιστικό τομογράφο με συγκεκριμένο πρωτόκολλο λήψης. Στις μελέτες αυτές δεν έχει γίνει διερεύνηση της επίδρασης του θορύβου στους αλγορίθμους τμηματοποίησης. Οι αλγόριθμοι μείωσης θορύβου έχουν προταθεί στην βιβλιογραφία έως βήμα προ επεξεργασίας για δεδομένα τα οποία είτε προέρχονται από διαφορετικά κέντρα ή έχουν ληφθεί αξιοποιώντας διαφορετικό πρωτόκολλο. Στην παρούσα μελέτη πραγματοποιήθηκε μελέτη της επίδρασης των τεχνικών μείωσης θορύβου στις τεχνικές τμηματοποίησης σε δεδομένα υπολογιστικής τομογραφίας θώρακος. Στην μελέτη αξιοποιήθηκαν δεδομένα τα όποια ελήφθησαν με πρωτόκολλο λήψης 3D δεδομένων ενώ στα πνευμονικά πεδία υπήρχαν πρότυπα ενδιάμεσης πνευμονοπάθειας. Οι τεχνικές τμηματοποίησης η οποίες αξιοποιήθηκαν ήταν οι k-means, Voxel Classification based, thresholding, MRF και η ΜΕΤΕΤ. Η τεχνική k-means είχε μια παράμετρο των αριθμών κλάσεων στην εικόνα η όποια προέκυψε έπειτα από πειραματικό προσδιορισμό (κ=4). Η τεχνική MRF απαιτούσε τον καθορισμό δυο παραμέτρων, του αριθμού των κλάσεων καθώς και του Β μιας παραμέτρου που καθορίζει την βαρύτητα που παίζει η γειτονία ενός pixel. Στην παρούσα μελέτη χρησιμοποιήθηκε μια σχετικά μεγάλη τιμή προκειμένου να μειωθεί η επίδραση του θορύβου στην τελική τμηματοποίηση. Τέλος η τεχνική ΜΕΤΕΤ περιέχει μια παράμετρο (του αριθμού κλάσεων) η όποια επιλεγεί να είναι κ=4 όπως προτείνεται στην βιβλιογραφία. Για την αξιολόγηση των αλγορίθμων τμηματοποίησης αξιοποιήθηκε η πλειοψηφία των δεικτών τμηματοποίησης που χρησιμοποιούνται στην βιβλιογραφία. Στην μελέτη αυτή χρησιμοποιήθηκαν όλοι οι δείκτες και όχι αποσπασματικά όπως εφαρμόζονται σε διάφορες δημοσιεύσεις. Το δείγμα αληθείας προέκυψε έπειτα από χειροκίνητη τμηματοποίηση 370 τομών από ακτινολόγο με χρόνια εμπειρίας στην ερμηνεία δεδομένων υπολογιστικής τομογραφίας. Για την υλοποίηση της εργασίας σχεδιάστηκε και αναπτύχθηκε στο εργαστήριο Ιατρικής Φυσικής του Πανεπιστήμιου Πατρών κατάλληλη γραφική επιφάνεια διεπαφής η οποία επέτρεπε στην ‘φόρτωση’ των δεδομένων, την τμηματοποίηση των πνευμονικών πεδίων, την εφαρμογή των αλγορίθμων μειώσης θορύβου, την χειροκίνητη τμηματοποίηση του υπολογισμού των δεικτών ακρίβειας και τέλος την αποθήκευση όλων των δεδομένων. Στην βιβλιογραφία έως σήμερα έχουν προταθεί μια σειρά αλγορίθμων τμηματοποίησης πνευμονικών πεδίων οι οποίες στοχεύουν είτε στην τμηματοποίηση υγιών πνευμονικών πεδίων είτε παθολογικών πνευμονικών πεδίων. Ωστόσο όλοι οι αλγόριθμοι εφαρμόζονται σε δεδομένα τα οποία προέρχονται από υπολογιστικούς τομογράφους με συγκεκριμένο πρωτόκολλο χωρίς να γίνεται περαιτέρω μελέτη συμπεριφοράς των αλγορίθμων σε δεδομένα από διαφορετικό πρωτόκολλο λήψης (διαφορετικό επίπεδο θορύβου). Βάση των αποτελεσμάτων τόσο στις αρχικές όσο και στις επεξεργασμένες εικόνες η τεχνική ΜΕΤΕΤ έδωσε τα καλύτερα αποτέλεσμα ως προς όλους τους δείκτες εκτός του δείκτη TPF όπου εκεί η μέθοδος k-means έδωσε το καλύτερο αποτέλεσμα. Το γεγονός αυτό μπορούμε να το αποδώσουμε επειδή η τεχνική βασίζεται στην ένταση των επιπέδων του γκρι τμηματοποιεί όλα τα τμήματα με φυσιολογική εμφάνιση άρα συμπίπτει καλύτερα με την τμηματοποίηση του ακτινολόγου χωρίς να εμφανίζει υπερ-τμηματοποίηση. Ο δείκτης TPF αποτελεί το κοινό τμήμα των δυο τμηματοποιήσεων. H στατιστική ανάλυση βάσης του δείκτη ρ που προκύπτει από το student t test ανέδειξε ότι η συμπεριφορά της ΜΕΤΕΤ δεν εμφανίζει στατιστικές σημαντικές διαφορές στις αρχικές όσο και στις επεξεργασμένες εικόνες. Τέλος οι τεχνικές τμηματοποίησης MRF, Thresholding, και Voxel Classification based εμφανίζουν την ίδια συμπεριφορά τόσο στις αρχικές όσο και στις επεξεργασμένες εικόνες. / Accurate and automated Lung Field (LF) segmentation in volumetric computed tomography protocols is highly challenged by the presence of pathologies affecting lung borders, also affecting the performance of computer-aided diagnosis (CAD) schemes. In this work, 4 three-dimensional LF segmentation algorithms are evaluated. The 4 algorithms considered are: • k-means based unsupervised segmentation. • Thresholding based segmentation (based on minimum error thresholding proposed by Kittler et al.). • Unsupervised segmentation followed by supervised border refinement. • Markov Random Field based unsupervised segmentation. Further more the algorithms are applied with or without denoising of data as a pre-processing step. Denoising techniques have been proposed to deal with the use of multi-center data i.e. datasets acquired with equipment from different vendors or different protocols. A home developed graphical user interface was used to apply the segmentation algorithms, perform denoising and finally allow for ground truth derivation. Seven quantitative indexes were used including overlap, Dice similarity coefficient, true and false positive fraction, mean distance, root mean square distance and finally distance maximum. Based on the analysis performed, unsupervised segmentation followed by supervised border refinement outperformed all the other methods exploited with respect to all quantitative measures considered except false positive fraction. Additionally the technique was robust against noise levels (performance with or without denoising did not present statistically significant difference). K-means unsupervised segmentation performed better from the other methods with respect to false positive fraction. This can be attributed to under-segmentation occurred since in this study k-means algorithm was based only on gray level information.