A cárie dentária continua sendo um grande desafio para os Cirurgiões-Dentistas pela dificuldade de diagnóstico, sobretudo em superfícies proximais. Muitos equipamentos se destinam a facilitar o exame do paciente, tendo como principal objetivo o diagnóstico de cáries incipientes. Dentre os exames mais utilizados está a radiografia interproximal associada ao exame clínico. O Sistema Internacional de Avaliação e Detecção de Cáries (ICDAS) vem sendo bem aceito tanto para o uso clínico como para pesquisas in vitro e in vivo, apresentando ótimos resultados. Além da técnica interproximal, a tomografia cone beam (CBCT) vem entrando no cotidiano da Odontologia, mas pouco se sabe sobre o seu desempenho para avaliação de cáries iniciais em superfícies proximais. A microtomografia (CT) é um novo método de avaliação destinado a pequenos espécimes e se assemelha a uma versão em miniatura da tomografia axial computadorizada, gerando imagens na ordem de micrômetros. Este método vem sendo utilização em pesquisas para se avaliar tecidos mineralizados, devido à sua habilidade de aferir com precisão o coeficiente de atenuação linear. O método padrão ouro que define com maior precisão os estágios da cárie é o histológico. Contudo, para sua avaliação é necessário destruir os espécimes. Este trabalho teve por objetivo avaliar o desempenho do método ICDAS, de radiografias digitais pela técnica interproximal, da CBCT e da CT para lesões precoces de cárie, com relação à histologia. Houve correlação entre os dados obtidos com o sistema ICDAS para superfícies proximais e as imagens da CT, no que diz respeito à classificação quanto à profundidade das lesões. A CT tem correlação positiva com a histologia tanto na classificação das lesões como na profundidade, contudo esta relação poderia ser maior se uma melhor resolução fosse conseguida. As radiografias digitais pela técnica interproximal tiveram o melhor desempenho com relação à CT e à histologia, sendo este desempenho muito semelhante ao método clínico ICDAS. A CBCT obteve o pior desempenho, contudo ainda assim houve correlação positiva com a histologia e com a CT. A associação do método clínico ICDAS e as radiografias interproximais digitais tiveram o melhor desempenho com relação à histologia. A grande vantagem da microtomografia quando comparada a outros métodos de avaliação da doença cárie, é a manutenção da integridade dos espécimes, a informação tridimensional e isotrópica, possibilitando o uso dos espécimes em outro momento, sem a perda de eventuais características presentes nos mesmos. / Dental caries is still a great challenge to dentists, manly in proximal surfaces due to its difficult diagnosis. Many types of equipment have been designed to minimize this problem, specially aiming early caries detection. Among all, one of the most used by clinicians is the interproximal radiograph. The International Caries Assessment System (ICDAS) is a clinical evaluation method that is well accepted and used having a good performance not only for in vivo but also for in vitro studies. Cone beam CT (CBCT) is also being assessed in the overall Dentistry, but its performance on early caries detection has not extensively being evaluated. Microtomography (CT) is a new assessment method which is addressed to small specimens and is similar to a miniature version of axial computed tomography, producing images with micrometrical definition. CT is being assessed in dental research to evaluate mineral content of hard tissues, due to its ability to measure precisely the linear attenuation coefficient. The gold standard method to measure early caries lesions is histological method. However, to perform it, its necessary to cut the specimen. This study had the aim to evaluate the ICDAS, digital X-rays with the interproximal technique, CBCT and CT performance for early caries lesions, when compared to histology. ICDAS for proximal surfaces and CT had a positive correlation through the lesions depth. CT had a positive correlation with histology when analyzing lesions depth and the classification relating to the severity of the lesion, although this relation could be better if a better resolution could be achieved. Digital bite-wing radiographs had the best performance among all exams when comparing to CT and histology, similar to what we notice with the ICDAS results. CBCT had the worst results when comparing to CT and histology, but it was still considered a good relation. The best performance was achieved with the association of ICDAS and digital bite-wing radiographs when comparing to histology. The great advantage of CT when compared to other validating methods to evaluate dental caries is that it doesnt destroy the specimens, it gives tridimensional and isotropic information, making possible to use the specimens again, without losing inner properties.

O objetivo principal desta pesquisa foi justificar a proposta de utilização de um novo método tomográfico (cone beam) de avaliação das espessuras ósseas alveolares, maxilares e mandibulares, por meio de testes objetivos das Condições de Repetitividade e de Precisão Intermediária associadas à variação intra e interoperadores, e conforme a utilização de programa computacional independente (AutoCAD®) para a realização das medições, aplicadas à sequência do Procedimento Operacional Padrão (POP) definido para este experimento. A Fase I da pesquisa registrou os critérios de obtenção da qualidade final das imagens tomográficas definitivas, a partir de equipamento iCAT® (Imaging Sciences International, Hatfield, Pa), com parâmetros de aquisição de 120KVp, 37,7mA e 26,9s, e considerando FOV cilíndrico de 13cm e matriz de 512x512 pixels. A resolução do voxel foi de 0,25mm; A Fase II registrou os critérios exploratórios relativos às condições operacionais do software de visualização, registro (inspeção e identificação) e medição das grandezas selecionadas. A Fase III registrou a realização dos testes de repetitividade e de reprodutibilidade das medidas. Um total de 72 grandezas lineares foram previamente definidas e metodologicamente testadas em sua qualidade de inspeção, identificação e medição, a partir da avaliação de sete (7) operadores independentes, cinco dos quais eram especialistas e com Mestrado Acadêmico em Ortodontia pela FOUSP e, o outro, especialista em Radiologia Odontológica e Doutor em Diagnóstico Bucal (FOUSP). Os examinadores foram previamente instruídos, calibrados e treinados considerando os requerimentos necessários à execução dos testes propostos. O protocolo de pesquisa foi aprovado pelo Comitê de Ética em Pesquisa da Faculdade de Odontologia da Universidade de São Paulo (Parecer CAAE 0120.0.017.000-11). A análise estatística dependeu da utilização de Modelo de Componentes de Variância (hierárquico), e foram consideradas como fontes de variação: as medidas, efetuadas por um mesmo operador ou por diferentes operadores; a face considerada, vestibular ou lingual/palatina; os locais (três níveis de espessura óssea alveolar) em cada uma das faces e, ainda, os diferentes dentes. Esta análise foi realizada de forma separada para mandíbula e maxila. Valores de p<0,05 indicaram significância estatística. Os resultados indicaram significativa confiabilidade geral no método proposto, considerando a Condição de Repetitividade, com apenas 0,24% da variabilidade maxilar total atribuível a um único operador, e mandibular de 0,53%; e com valores expressivos relativos às incertezas de medida maxilares (0,156mm) e mandibulares (0,091mm), desse modo atestando significativa consistência interna (repetibilidade) do método. Os testes da Condição de Precisão Intermediária também indicaram significativa confiabilidade geral no método proposto, com apenas 1,52% da variabilidade total mandibular atribuível à participação de diversos operadores, e maxilar de 0,25%; e com valores também expressivos relativos às incertezas de medida mandibulares (0,149mm) e maxilares (0,158mm), desse modo atestando significativa condição final de reprodutibilidade. Conclui-se que a utilização de imagens provenientes de tomógrafo iCAT®, conforme indicação de resolução de imagem com voxel de 0,25mm, em humanos vivos e a partir de cortes trans-axiais sistematicamente operacionalizados com auxílio de Software AutoCAD®, propicia a geração de condições metodológicas suficientemente favoráveis à obtenção de mapeamento quantitativo linear de espessuras ósseas alveolares, vestibulares e palatinas/linguais, tanto para a maxila quanto para a mandíbula. / This research aimed to justify the proposed use of a new tomography method (cone beam) in the clinical assessment of alveolar, maxillary and mandibular bone width, through objective tests of the Conditions of Repetitiveness and Intermediate Precision associated with intra- and inter-operator variation, using the independent computer program (AutoCAD®) for the execution of the measurements according to the Standard Operating Procedure (SOP) sequence defined for this experiment. Phase I of the research recorded the criteria for obtaining the final quality of the tomography images, using iCAT® (Imaging Sciences International, Hatfield, Pa, USA) equipment with acquisition parameters 120KVp, 37.7mA, and 26.9s, and considering cilindric field-of-view (FOV) of 13cm and 512x512 pixels matrix. The voxel resolution was 0.25mm. Phase II recorded the exploratory criteria relative to the operational conditions of the visualization software, registry (visual inspection and landmark identification) and measurement of the selected magnitudes. Phase III recorded the tests of repeatability and reproducibility of the measurements. A total of 72 linear magnitudes were previously defined and methodologically tested for their quality of inspection, identification and measurement, based on assessment by seven (7) independent operators, five of whom were specialists, with masters degrees in Orthodontics from FOUSP; and the other, a specialist in Dental Radiology and Doctor of Oral Diagnosis (FOUSP). The examiners were previously instructed, calibrated and trained according to the requirements for performing the proposed tests. The research protocol was approved by the Committee for Ethics in Research of the Faculty of Dentistry at the University of São Paulo (Protocol # 102/11-CAAE 0120.0.017.000-11). Statistical analysis used the (hierarchical) Components of Variation Model, and the sources of variation were considered to be: the measurements, made by the same operator or by different operators; the face considered, whether vestibular or lingual/palatal; the locations (three levels of alveolar bone thickness) in each of the faces and, also, the different teeth. This analysis was carried out separately for the mandible and the maxilla. Values of p<0.05 indicated statistical significance. The results indicated overall significant reliability in the proposed method considering the Condition of Repetitiveness, with only 0.24% of total maxillary, and 0.53% of mandibular, variability attributable to a single operator; and with expressive values relative to measurement uncertainties of maxillary (0.156 mm) and mandibular (0.091mm) averages, thereby attesting to significant internal consistency (\"repeatability\") of the method. Tests for the Condition of Intermediate Precision also indicated overall significant reliability of the proposed method, with only 1.52% total mandibular, and 0.25% maxillary, variability attributable to the participation of the various operators; and, also, with expressive values relative to measurement uncertainties of mandibular (0.149mm) and maxillary (0.158mm) averages, thereby attesting to the significant final condition of reproducibility. It is concluded that the use of images from iCAT® tomography, as indicated by image resolution with voxels of 0.25mm, in live humans and from transaxial cuts performed systematically with the help of AutoCAD® Software, provides methodological conditions sufficiently favorable for obtaining linear quantitative mapping of alveolar, vestibular and palatal/lingual bone thicknesses, for both the maxillary and mandibular dental arches.

A cárie dentária continua sendo um grande desafio para os Cirurgiões-Dentistas pela dificuldade de diagnóstico, sobretudo em superfícies proximais. Muitos equipamentos se destinam a facilitar o exame do paciente, tendo como principal objetivo o diagnóstico de cáries incipientes. Dentre os exames mais utilizados está a radiografia interproximal associada ao exame clínico. O Sistema Internacional de Avaliação e Detecção de Cáries (ICDAS) vem sendo bem aceito tanto para o uso clínico como para pesquisas in vitro e in vivo, apresentando ótimos resultados. Além da técnica interproximal, a tomografia cone beam (CBCT) vem entrando no cotidiano da Odontologia, mas pouco se sabe sobre o seu desempenho para avaliação de cáries iniciais em superfícies proximais. A microtomografia (CT) é um novo método de avaliação destinado a pequenos espécimes e se assemelha a uma versão em miniatura da tomografia axial computadorizada, gerando imagens na ordem de micrômetros. Este método vem sendo utilização em pesquisas para se avaliar tecidos mineralizados, devido à sua habilidade de aferir com precisão o coeficiente de atenuação linear. O método padrão ouro que define com maior precisão os estágios da cárie é o histológico. Contudo, para sua avaliação é necessário destruir os espécimes. Este trabalho teve por objetivo avaliar o desempenho do método ICDAS, de radiografias digitais pela técnica interproximal, da CBCT e da CT para lesões precoces de cárie, com relação à histologia. Houve correlação entre os dados obtidos com o sistema ICDAS para superfícies proximais e as imagens da CT, no que diz respeito à classificação quanto à profundidade das lesões. A CT tem correlação positiva com a histologia tanto na classificação das lesões como na profundidade, contudo esta relação poderia ser maior se uma melhor resolução fosse conseguida. As radiografias digitais pela técnica interproximal tiveram o melhor desempenho com relação à CT e à histologia, sendo este desempenho muito semelhante ao método clínico ICDAS. A CBCT obteve o pior desempenho, contudo ainda assim houve correlação positiva com a histologia e com a CT. A associação do método clínico ICDAS e as radiografias interproximais digitais tiveram o melhor desempenho com relação à histologia. A grande vantagem da microtomografia quando comparada a outros métodos de avaliação da doença cárie, é a manutenção da integridade dos espécimes, a informação tridimensional e isotrópica, possibilitando o uso dos espécimes em outro momento, sem a perda de eventuais características presentes nos mesmos. / Dental caries is still a great challenge to dentists, manly in proximal surfaces due to its difficult diagnosis. Many types of equipment have been designed to minimize this problem, specially aiming early caries detection. Among all, one of the most used by clinicians is the interproximal radiograph. The International Caries Assessment System (ICDAS) is a clinical evaluation method that is well accepted and used having a good performance not only for in vivo but also for in vitro studies. Cone beam CT (CBCT) is also being assessed in the overall Dentistry, but its performance on early caries detection has not extensively being evaluated. Microtomography (CT) is a new assessment method which is addressed to small specimens and is similar to a miniature version of axial computed tomography, producing images with micrometrical definition. CT is being assessed in dental research to evaluate mineral content of hard tissues, due to its ability to measure precisely the linear attenuation coefficient. The gold standard method to measure early caries lesions is histological method. However, to perform it, its necessary to cut the specimen. This study had the aim to evaluate the ICDAS, digital X-rays with the interproximal technique, CBCT and CT performance for early caries lesions, when compared to histology. ICDAS for proximal surfaces and CT had a positive correlation through the lesions depth. CT had a positive correlation with histology when analyzing lesions depth and the classification relating to the severity of the lesion, although this relation could be better if a better resolution could be achieved. Digital bite-wing radiographs had the best performance among all exams when comparing to CT and histology, similar to what we notice with the ICDAS results. CBCT had the worst results when comparing to CT and histology, but it was still considered a good relation. The best performance was achieved with the association of ICDAS and digital bite-wing radiographs when comparing to histology. The great advantage of CT when compared to other validating methods to evaluate dental caries is that it doesnt destroy the specimens, it gives tridimensional and isotropic information, making possible to use the specimens again, without losing inner properties.

Submitted by PPG Odontologia (odontologia-pg@pucrs.br) on 2018-11-13T11:21:21Z No. of bitstreams: 1 ANDRE_XAVIER_PADILHA_FAVORETO_DIS.pdf: 4813223 bytes, checksum: 0ef272778a4eecc19798203feb8449ef (MD5) / Approved for entry into archive by Caroline Xavier (caroline.xavier@pucrs.br) on 2018-11-13T16:37:50Z (GMT) No. of bitstreams: 1 ANDRE_XAVIER_PADILHA_FAVORETO_DIS.pdf: 4813223 bytes, checksum: 0ef272778a4eecc19798203feb8449ef (MD5) / Made available in DSpace on 2018-11-13T17:02:11Z (GMT). No. of bitstreams: 1 ANDRE_XAVIER_PADILHA_FAVORETO_DIS.pdf: 4813223 bytes, checksum: 0ef272778a4eecc19798203feb8449ef (MD5) Previous issue date: 2018-03-07 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / This retrospective study aims to evaluate the morphological changes produced after and surgically assisted maxillary rapid expansion (ERMAC). A three-dimensional evaluation was performed with CBT and scanning of the intraoral and gingival models at the preoperative (T0) and postoperative (T1 and T2) moments in order to evaluate linear and angular movements with bone and dental changes underlying. The possible morphological alterations of the related structures were evaluated: nasopharynx volume, oropharynx volume in relation to ERMAC. The sample consisted of 15 individuals (8 males and 7 females aged 19 to 54 years) submitted to MRS. In general, ERMAC produced a significant increase in all linear distances of the maxilla. There was a greater expansion of the maxilla in the anterior region than in the posterior one. The ERMAC produced a significant increase of the skeletal dimensions of the maxilla in the transversal direction. In the airways, there was a significant increase in all patients and the greatest effects of ERMAC occurred at the dental level, with the buccal inclination of the first molars and the upper premolars being observed. / Objetiva-se com este estudo retrospectivo avaliar as altera??es morfol?gicas produzidas ap?s e expans?o r?pida maxilar assistida cirurgicamente (ERMAC). Realizou-se uma avalia??o tridimensional com TCCB e escaneamento dos modelos de gesso e dos dentes intraoral no momento pr?-operat?rio (T0) e p?s-operat?rio (T1 e T2) a fim de avaliar os movimentos lineares e angulares com as altera??es ?sseas e dent?rias subjacentes. Avaliou - se as poss?veis altera??es morfol?gicas das estruturas correlatas: volume da nasofaringe, volume da orofaringe com rela??o a ERMAC. A amostra constituiu-se de 15 indiv?duos (8 homens e 7 mulheres com idades entre 19 e 54 anos) submetidos a ERMAC. De modo geral, a ERMAC produziu aumento significativo de todas as dist?ncias lineares da maxila. Houve maior expans?o da maxila na regi?o anterior do que na posterior. A ERMAC produziu aumento significativo das dimens?es esquel?ticas da maxila no sentido transversal. Nas vias a?reas houve aumento significativo em todos os pacientes e os maiores efeitos da ERMAC ocorreram no n?vel dent?rio, sendo observada a inclina??o vestibular dos primeiros molares e nos pr?-molares superiores.

O objetivo principal desta pesquisa foi justificar a proposta de utilização de um novo método tomográfico (cone beam) de avaliação das espessuras ósseas alveolares, maxilares e mandibulares, por meio de testes objetivos das Condições de Repetitividade e de Precisão Intermediária associadas à variação intra e interoperadores, e conforme a utilização de programa computacional independente (AutoCAD®) para a realização das medições, aplicadas à sequência do Procedimento Operacional Padrão (POP) definido para este experimento. A Fase I da pesquisa registrou os critérios de obtenção da qualidade final das imagens tomográficas definitivas, a partir de equipamento iCAT® (Imaging Sciences International, Hatfield, Pa), com parâmetros de aquisição de 120KVp, 37,7mA e 26,9s, e considerando FOV cilíndrico de 13cm e matriz de 512x512 pixels. A resolução do voxel foi de 0,25mm; A Fase II registrou os critérios exploratórios relativos às condições operacionais do software de visualização, registro (inspeção e identificação) e medição das grandezas selecionadas. A Fase III registrou a realização dos testes de repetitividade e de reprodutibilidade das medidas. Um total de 72 grandezas lineares foram previamente definidas e metodologicamente testadas em sua qualidade de inspeção, identificação e medição, a partir da avaliação de sete (7) operadores independentes, cinco dos quais eram especialistas e com Mestrado Acadêmico em Ortodontia pela FOUSP e, o outro, especialista em Radiologia Odontológica e Doutor em Diagnóstico Bucal (FOUSP). Os examinadores foram previamente instruídos, calibrados e treinados considerando os requerimentos necessários à execução dos testes propostos. O protocolo de pesquisa foi aprovado pelo Comitê de Ética em Pesquisa da Faculdade de Odontologia da Universidade de São Paulo (Parecer CAAE 0120.0.017.000-11). A análise estatística dependeu da utilização de Modelo de Componentes de Variância (hierárquico), e foram consideradas como fontes de variação: as medidas, efetuadas por um mesmo operador ou por diferentes operadores; a face considerada, vestibular ou lingual/palatina; os locais (três níveis de espessura óssea alveolar) em cada uma das faces e, ainda, os diferentes dentes. Esta análise foi realizada de forma separada para mandíbula e maxila. Valores de p<0,05 indicaram significância estatística. Os resultados indicaram significativa confiabilidade geral no método proposto, considerando a Condição de Repetitividade, com apenas 0,24% da variabilidade maxilar total atribuível a um único operador, e mandibular de 0,53%; e com valores expressivos relativos às incertezas de medida maxilares (0,156mm) e mandibulares (0,091mm), desse modo atestando significativa consistência interna (repetibilidade) do método. Os testes da Condição de Precisão Intermediária também indicaram significativa confiabilidade geral no método proposto, com apenas 1,52% da variabilidade total mandibular atribuível à participação de diversos operadores, e maxilar de 0,25%; e com valores também expressivos relativos às incertezas de medida mandibulares (0,149mm) e maxilares (0,158mm), desse modo atestando significativa condição final de reprodutibilidade. Conclui-se que a utilização de imagens provenientes de tomógrafo iCAT®, conforme indicação de resolução de imagem com voxel de 0,25mm, em humanos vivos e a partir de cortes trans-axiais sistematicamente operacionalizados com auxílio de Software AutoCAD®, propicia a geração de condições metodológicas suficientemente favoráveis à obtenção de mapeamento quantitativo linear de espessuras ósseas alveolares, vestibulares e palatinas/linguais, tanto para a maxila quanto para a mandíbula. / This research aimed to justify the proposed use of a new tomography method (cone beam) in the clinical assessment of alveolar, maxillary and mandibular bone width, through objective tests of the Conditions of Repetitiveness and Intermediate Precision associated with intra- and inter-operator variation, using the independent computer program (AutoCAD®) for the execution of the measurements according to the Standard Operating Procedure (SOP) sequence defined for this experiment. Phase I of the research recorded the criteria for obtaining the final quality of the tomography images, using iCAT® (Imaging Sciences International, Hatfield, Pa, USA) equipment with acquisition parameters 120KVp, 37.7mA, and 26.9s, and considering cilindric field-of-view (FOV) of 13cm and 512x512 pixels matrix. The voxel resolution was 0.25mm. Phase II recorded the exploratory criteria relative to the operational conditions of the visualization software, registry (visual inspection and landmark identification) and measurement of the selected magnitudes. Phase III recorded the tests of repeatability and reproducibility of the measurements. A total of 72 linear magnitudes were previously defined and methodologically tested for their quality of inspection, identification and measurement, based on assessment by seven (7) independent operators, five of whom were specialists, with masters degrees in Orthodontics from FOUSP; and the other, a specialist in Dental Radiology and Doctor of Oral Diagnosis (FOUSP). The examiners were previously instructed, calibrated and trained according to the requirements for performing the proposed tests. The research protocol was approved by the Committee for Ethics in Research of the Faculty of Dentistry at the University of São Paulo (Protocol # 102/11-CAAE 0120.0.017.000-11). Statistical analysis used the (hierarchical) Components of Variation Model, and the sources of variation were considered to be: the measurements, made by the same operator or by different operators; the face considered, whether vestibular or lingual/palatal; the locations (three levels of alveolar bone thickness) in each of the faces and, also, the different teeth. This analysis was carried out separately for the mandible and the maxilla. Values of p<0.05 indicated statistical significance. The results indicated overall significant reliability in the proposed method considering the Condition of Repetitiveness, with only 0.24% of total maxillary, and 0.53% of mandibular, variability attributable to a single operator; and with expressive values relative to measurement uncertainties of maxillary (0.156 mm) and mandibular (0.091mm) averages, thereby attesting to significant internal consistency (\"repeatability\") of the method. Tests for the Condition of Intermediate Precision also indicated overall significant reliability of the proposed method, with only 1.52% total mandibular, and 0.25% maxillary, variability attributable to the participation of the various operators; and, also, with expressive values relative to measurement uncertainties of mandibular (0.149mm) and maxillary (0.158mm) averages, thereby attesting to the significant final condition of reproducibility. It is concluded that the use of images from iCAT® tomography, as indicated by image resolution with voxels of 0.25mm, in live humans and from transaxial cuts performed systematically with the help of AutoCAD® Software, provides methodological conditions sufficiently favorable for obtaining linear quantitative mapping of alveolar, vestibular and palatal/lingual bone thicknesses, for both the maxillary and mandibular dental arches.

L'imagerie cone-beam computed tomography (CBCT) est une méthodologie de contrôle non destructif permettant l'obtention d'images volumiques d'un objet. Le système d'acquisition se compose d'un tube à rayons X et d'un détecteur plan numérique. La recherche développée dans ce manuscrit se déroule dans le contexte industriel. L'objet est placé sur une platine de rotation et une séquence d'images 2D est acquise. Un algorithme de reconstruction procure des données volumiques de l'atténuation de l'objet. Ces informations permettent de réaliser une étude métrologique et de valider ou non la conformité de la pièce imagée. La qualité de l'image 3D est dégradée par différents artefacts inhérents à la plateforme d'acquisition. L'objectif de cette thèse est de mettre au point une méthode de correction adaptée à une plateforme de micro-tomographie par rayons X d'objets manufacturés poly-matériaux. Le premier chapitre décrit les bases de la physique et de l'algorithmie propres à la technique d'imagerie CBCT par rayons X ainsi que les différents artefacts nuisant à la qualité de l'image finale. Le travail présenté ici se concentre sur deux types d'artefacts en particulier: les rayonnements secondaires issus de l'objet et du détecteur et le durcissement de faisceau. Le second chapitre présente un état de l'art des méthodes visant à corriger le rayonnement secondaire. Afin de quantifier le rayonnement secondaire, un outil de simulation basé sur des techniques de Monte Carlo hybride est développé. Il permet de caractériser le système d'acquisition installé au laboratoire de façon réaliste. Le troisième chapitre détaille la mise en place et la validation de cet outil. Les calculs Monte Carlo étant particulièrement prohibitifs en terme de temps de calcul, des techniques d'optimisation et d'accélération sont décrites. Le comportement du détecteur est étudié avec attention et il s'avère qu'une représentation 2D suffit pour modéliser le rayonnement secondaire. Le modèle de simulation permet une reproduction fidèle des projections acquises avec le système réel. Enfin, le dernier chapitre présente la méthodologie de correction que nous proposons. Une première reconstruction bruitée de l'objet imagé est segmentée afin d'obtenir un modèle voxélisé en densités et en matériaux. L'environnement de simulation fournit alors les projections associées à ce volume. Le volume est corrigé de façon itérative. Des résultats de correction d'images tomographiques expérimentales sont présentés dans le cas d'un objet mono-matériaux et d'un objet poly-matériaux. Notre routine de correction réduit les artefacts de cupping et améliore la description du volume reconstruit. / Cone-beam computed tomography (CBCT) is a standard nondestructive imaging technique related to the acquisition of three-dimensional data. This methodology interests a wide range of applications. An industrial CBCT system comprises an X-ray source and a flat-panel detector. Radiographic images are acquired during a rotation of the object of interest. A reconstruction algorithm leads to a volumic representation of the object and a post-processing routine assesses its validity. Accurate quantitative reconstruction is needed to perform an efficient diagsnotic. However, it is challenged by the presence of different artefacts coming from the acquisition itself. This thesis aims at analyzing and correcting those artefacts in a context of industrial micro-tomography. After an introduction to the physical and algorithmic background of CBCT, the artefacts are presented. Our study adresses two major artefacts: beam hardening and scatter radiations coming from the object and the detector. The second chapter reports on the state of the art in secondary radiation correction. A simulation model of the CBCT imaging chain is developed in a Monte Carlo environment. This model is designed to be realistic in order to get an accurate insight on the processes contributing to the final image formation. The third chapter focuses on the built and validation of the simulation tool. Monte Carlo methods are exact but prohibitively slow. Consequently, acceleration and optimization techniques are used to speed-up the calculations without loss of accuracy. A layer model of the flat-panel detector gives some insight on its secondary radiation behavior. More specifically, we demonstrate that a 2D description of the detector would be sufficient to compute its contribution. Our projection tool fits well with the real system. Finally, the last chapter describes our iterative correction method. The noisy initial reconstruction is segmented into different materials and densities and fed to the simulation framework. Beam hardening and secondary radiations are corrected via the volume reconstructed from the difference between acquired and simulated projections. This correction method is shown to be effective on both mono-material and poly-material objects.

Objetivo: Evaluar el grosor dentinario en el tercio cervical, medio y apical de primeros molares deciduos a nivel de las paredes de los conductos radiculares mediante el uso de tomografía computarizada de haz cónico. Materiales y métodos: La muestra estuvo conformada por 30 tomografías de haz cónico. La unidad de análisis estuvo compuesta por primeros molares deciduos, los cuales fueron divididos en dos grupos (n=15), el grupo de primeros molares deciduos superiores e inferiores. Para la toma de las medidas del grosor dentinario de las paredes de cada conducto, se realizó 3 cortes de vista axial en la tomografía en el tercio cervical, medio y apical. Luego, cada tercio fue dividido en 4 superficies (distal, mesial, lingual/palatino y vestibular), lo cual sirvió para tomar las medidas y realizar la sumatoria de las 4 superficies del grosor dentinario en milímetros para obtener el promedio final del tercio. Los datos fueron analizados mediante estadística descriptiva (media, mediana, desviación estándar y rango intercuartílico). Resultado: Se obtuvieron las medias para el grupo del primer molar deciduo superior e inferior, en los cuales se observó medidas diferentes a nivel de los tres tercios y superficies evaluadas. Conclusión: Es importante tener mayor conocimiento sobre la anatomía del primer molar deciduo, debido a las diversas características que esta presenta en comparación a los molares de la dentición permanente. / Objective: To evaluate the dentin thickness in cervical, middle and apical third of deciduous first molars at the level of the root canal walls by using cone beam computed tomography. Materials and Methods: The sample consisted of 30 Cone Beam tomography. The analysis unit was made up of deciduous first molars, which were divided into two groups (n=15), the group of upper and lower deciduous first molars. To take the measurements of the dentin thickness of the walls of each canal, 3 axial views were made on the tomography in the cervical, middle and apical third. Then each third was divided into 4 surfaces (distal, mesial, lingual / palatal and vestibular), which served to take the measurements and make the sum of the 4 surfaces of the dentin thickness in millimeters to obtain the final average of the third. Data were analyzed using descriptive statistics (mean, median, standard deviation and interquartile range). Results: The means for the upper and lower deciduous first molar group were obtained, in which different measures were observed at the level of the three-thirds and evaluated surfaces. Conclusion: It is important know more about anatomy of the first deciduous molar, due to the various characteristics that it presents compared to the molars of the permanent dentition. / Tesis

C-arm Cone Beam CT (CBCT) systems – due to compact size, flexible geometry and low radiation exposure – inaugurated the era of on-board 3D image guidance in therapeutic and surgical procedures. Leksell Gamma Knife Icon by Elekta introduced an integrated CBCT system to determine patient position prior to surgical session, thus advancing to a paradigm shift in facilitating frameless stereotactic radiosurgeries. While CBCT offers a quick imaging facility with high spatial accuracy, the quantitative values tend to be distorted due to various physics based artifacts such as scatter, beam hardening and cone beam effect. Several 3D reconstruction algorithms targeting these artifacts involve an accurate and fast segmentation of craniofacial CBCT images into air, tissue and bone. The objective of the thesis is to investigate the performance of deep learning based convolutional neural networks (CNN) in relation to conventional image processing and machine learning algorithms in segmenting CBCT images. CBCT data for training and testing procedures was provided by Elekta. A framework of segmentation algorithms including multilevel automatic thresholding, fuzzy clustering, multilayer perceptron and CNN is developed and tested against pre-defined evaluation metrics carrying pixel-wise prediction accuracy, statistical tests and execution times among others. CNN has proven its ability to outperform other segmentation algorithms throughout the evaluation metrics except for execution times. Mean segmentation error for CNN is found to be 0.4% with a standard deviation of 0.07%, followed by fuzzy clustering with mean segmentation error of 0.8% and a standard deviation of 0.12%. CNN based segmentation takes 500s compared to multilevel thresholding which requires ~1s on similar sized CBCT image. The present work demonstrates the ability of CNN in handling artifacts and noise in CBCT images and maintaining a high semantic segmentation performance. However, further efforts targeting CNN execution speed are required to utilize the segmentation framework within real-time 3D reconstruction algorithms. / C-arm Cone Beam CT (CBCT) system har tack vare sitt kompakta format, flexibla geometri och låga strålningsdos startat en era av inbyggda 3D bildtagningssystem för styrning av terapeutiska och kirurgiska ingripanden. Elektas Leksell Gamma Knife Icon introducerade ett integrerat CBCT-system för att bestämma patientens position för operationer och på så sätt gå in i en paradigm av ramlös stereotaktisk strålkirurgi. Även om CBCT erbjuder snabb bildtagning med hög spatiel noggrannhet så tenderar de kvantitativa värdena att störas av olika artefakter som spridning, beam hardening och cone beam effekten. Ett flertal 3D rekonstruktionsalgorithmer som försöker reducera dessa artefakter kräver en noggrann och snabb segmentering av kraniofaciala CBCT-bilder i luft, mjukvävnad och ben. Målet med den här avhandlingen är att undersöka hur djupa neurala nätverk baserade på faltning (convolutional neural networks, CNN) presterar i jämförelse med konventionella bildbehandlings- och maskininlärningalgorithmer för segmentering av CBCT-bilder. CBCT-data för träning och testning tillhandahölls av Elekta. Ett ramverk för segmenteringsalgorithmer inklusive flernivåströskling (multilevel automatic thresholding), suddig klustring (fuzzy clustering), flerlagersperceptroner (multilayer perceptron) och CNN utvecklas och testas mot fördefinerade utvärderingskriterier som pixelvis noggrannhet, statistiska tester och körtid. CNN presterade bäst i alla metriker förutom körtid. Det genomsnittliga segmenteringsfelet för CNN var 0.4% med en standardavvikelse på 0.07%, följt av suddig klustring med ett medelfel på 0.8% och en standardavvikelse på 0.12%. CNN kräver 500 sekunder jämfört med ungefär 1 sekund för den snabbaste algorithmen, flernivåströskling på lika stora CBCT-volymer. Arbetet visar CNNs förmåga att handera artefakter och brus i CBCT-bilder och bibehålla en högkvalitativ semantisk segmentering. Vidare arbete behövs dock för att förbättra presetandan hos algorithmen för att metoden ska vara applicerbar i realtidsrekonstruktionsalgorithmer.

The objective of this work is to develop an on-line planning and delivery technique for palliative radiotherapy of spinal metastases using a linear accelerator capable of cone-beam CT (CBCT) imaging. This technique integrates all preparation and delivery steps into a single session equivalent to an initial treatment session. The key technical challenges pertaining to the development and implementation of this novel treatment technique are related to CBCT image performance, efficient system integration, development of on-line planning tools and design of novel quality assurance (QA) phantoms and processes. Hardware and software image corrections were first implemented to make CBCT images suitable for target definition and planning. These corrections reduced CBCT non-uniformity and improved CBCT-number accuracy. The on-line treatment technique workflow and the integration of all the subsystems involved in the process were assessed on a customized spine phantom constructed for the study. The challenges related to the routine QA of the highly integrated on-line treatment technique were addressed with the construction and validation of an integral test phantom. This phantom, which contains point detectors (diodes) allows for real-time QA of the entire image guidance, planning and treatment process in terms of dose delivery accuracy. The integral test phantom was also effective for the QA of high-dose, high-precision spinal radiosurgery. Simulation of the on-line treatment technique on patient data showed that the planning step was the one of the most time consuming tasks due predominantly to manual target definition. A semi-automatic method for detection and identification of vertebrae on CBCT images was developed and validated to streamline vertebra segmentation and improve the on-line treatment efficiency. With a single patient setup at the treatment unit, patient motion during the on-line process represents the main source of geometric uncertainty for dose delivery. Spine intra-fraction motion was assessed on CBCT for a group of 49 patients treated with a palliative intent. The use of surface marker tracking as a surrogate for spine motion was also evaluated. Finally, the complete on-line planning and delivery technique was implemented in a research ethics board (REB) approved clinical study at the Princess Margaret Hospital and 7 patients have been successfully treated at the time of this report with this novel treatment approach.

This dissertation describes the application of two principled variance reduction strategies to increase the efficiency for two applications within medical physics. The first, called correlated Monte Carlo (CMC) applies to patient-specific, permanent-seed brachytherapy (PSB) dose calculations. The second, called adjoint-biased forward Monte Carlo (ABFMC), is used to compute cone-beam computed tomography (CBCT) scatter projections. CMC was applied for two PSB cases: a clinical post-implant prostate, and a breast with a simulated lumpectomy cavity. CMC computes the dose difference between the highly correlated dose computing homogeneous and heterogeneous geometries. The particle transport in the heterogeneous geometry assumed a purely homogeneous environment, and altered particle weights accounted for bias. Average gains of 37 to 60 are reported from using CMC, relative to un-correlated Monte Carlo (UMC) calculations, for the prostate and breast CTV’s, respectively. To further increase the efficiency up to 1500 fold above UMC, an approximation called interpolated correlated Monte Carlo (ICMC) was applied. ICMC computes using CMC on a low-resolution (LR) spatial grid followed by interpolation to a high-resolution (HR) voxel grid followed. The interpolated, HR is then summed with a HR, pre-computed, homogeneous dose map. ICMC computes an approximate, but accurate, HR heterogeneous dose distribution from LR MC calculations achieving an average 2% standard deviation within the prostate and breast CTV’s in 1.1 sec and 0.39 sec, respectively. Accuracy for 80% of the voxels using ICMC is within 3% for anatomically realistic geometries. Second, for CBCT scatter projections, ABFMC was implemented via weight windowing using a solution to the adjoint Boltzmann transport equation computed either via the discrete ordinates method (DOM), or a MC implemented forward-adjoint importance generator (FAIG). ABFMC, implemented via DOM or FAIG, was tested for a single elliptical water cylinder using a primary point source (PPS) and a phase-space source (PSS). The best gains were found by using the PSS yielding average efficiency gains of 250 relative to non-weight windowed MC utilizing the PPS. Furthermore, computing 360 projections on a 40 by 30 pixel grid requires only 48 min on a single CPU core allowing clinical use via parallel processing techniques.