La tomodensitométrie intégrant une source de rayons X à faisceau divergent et un détecteur grand champ est une technique bien connue dans le domaine de la tomographie industrielle. La nature des matériaux et les épaisseurs traversées conduisent inévitablement à la génération de rayonnement diffusé. Ce dernier est généré par l’objet mais également par le détecteur. La présence de rayonnement parasite conduit à ne plus respecter l’hypothèse de la loi de Beer-Lambert. Par conséquent, on voit apparaitre sur les coupes tomographiques des artefacts de reconstruction comme des streaks, des effets ventouses ou des valeurs d’atténuation linéaire erronée. Par conséquence, on retrouve dans la littérature de nombreuses méthodes de correction du diffusé. Ce travail vise à mettre en point et tester une méthode originale de correction du diffusé. Le premier chapitre de cette étude, dresse un état de l’art de la plupart des méthodes de corrections existantes. Nous proposons, dans le deuxième chapitre, une évolution de la méthode de superposition des noyaux de convolution (Scatter Kernel Superposition). Notre méthode repose sur une description continue des noyaux en fonction de l’épaisseur traversée. Dans cette méthode, les noyaux de diffusion sont paramétrés analytiquement sur toute la plage d'épaisseur. Le procédé a été testé pour des objets à la fois mono-matériaux et poly-matériaux, ainsi que sur des données expérimentales et simulées. Nous montrons dans le troisième chapitre l’importance de la contribution du diffusé détecteur dans la qualité de l’image reconstruite. Mais également l’importance de décrire les noyaux de convolution à l'aide d'un modèle à quatre gaussienne. Les résultats obtenus à partir de données expérimentales prouvent que la correction du diffusé de l'objet seul ne suffit pas pour obtenir une image de reconstruite sans artefacts. Afin de disposer d’une meilleur modélisation du diffusé du détecteur, nous décrivons, dans le dernier chapitre, une méthode basée sur la combinaison de données expérimentales et simulées permettant d’améliorer l’estimation des noyaux de diffusé. / Advanced Cone Beam Computed Tomography (CBCT) typically uses a divergent conebeam source and a large area detector. As a result, there an inevitable increase in the size area of illumination causing an increase in the intensity of X-ray scatter signal, both from the object and the detector. This leads to the violation of prime assumption of reconstruction process which is based on straight line integrals path followed by the photons. Consequently scatter artifacts appear in the reconstruction images as steaks, cupping effect and thus produce wrong reconstruction values. Due to the severity of the reconstruction artifact caused by scatter, many scatter corrections methods have been adopted in literature. The first part of this study, reviews most of the existing scatter correction methods. The effect of scattering becomes more prominent and challenging in case of X-ray source of high energy which is used in industrial Non Destructive Testing (NDT), due to higher scatter to primary ratio (SPR). Therefore, in this study, we propose a continuously thickness-adapted deconvolution approach based on improvements in the Scatter Kernel Superposition (SKS) method. In this method, the scatter kernels are analytically parameterized over the whole thickness range of the object under study to better sample the amplitude and shape of kernels with respect to the thickness. The method is tested for both homogeneous and heterogeneous objects as well as simulated and experimental data. Another important aspect of this study is the comprehensive evaluation of contribution of the detector scatter performed using continuous method by separating the contribution of scatter due to the object and the detector. This is performed by modeling the scatter kernels using a four-Gaussian model. In the first approach, we performed this evaluation based on simulation of kernels from Monte Carlo simulations and the corrections are performed on typical industrial experimental data. The results obtained prove that the scatter correction only due to the object is not sufficient to obtain reconstruction image, free from artifacts, as the detector also scatters considerably. In order to prove this point experimentally and to have a better modeling of the detector, we describe a method based on combination of experiments and simulations to calculate the scatter kernels. The results obtained also prove, the contribution of the detector scattering becomes important and the PSF of the detector is not constant as considered in the studies so far, but it varies to a great extend with the energy spectrum.

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

Die Radiologie fungiert als wesentliches Instrument in der Diagnostik und Nachsorge fibro-ossärer Läsionen (FOL). Hierbei gewinnen überlagerungsfreie, dreidimensionale Aufnahmen aufgrund der im Kopf-Halsbereich vorhandenen hohen Dichte und Vielfalt anatomischer Strukturen und der damit einhergehenden Fülle von Differentialdiagnosen an Bedeutung. Anhand der Studie wurden die röntgenologischen Charakteristika von ossären Dysplasien (OD) und ossifizierenden Fibromen (OF) im dentalen Volumentomogramm herausgestellt, sowie diagnostische und therapeutische Vorteile der dentalen Volumentomographie (DVT) im Vergleich zur Orthopantomographie (OPG) und Computertomographie (CT) ermittelt und gegenübergestellt. Zu diesem Zwecke wurden anhand eines Fragebogens 18 Röntgenbildpaare (OPG-DVT) von FOL durch zehn Betrachter auf (A) deren röntgenologische Eigenschaften sowie Metallartefakte befundet und (B) deren Abbildungsqualität von sehr gut (1) bis schlecht (5) bzw. nicht beurteilbar bewertet. Insgesamt wurden 360 Analysebögen ausgewertet. Entitäts- und röntgentechnikspezifische Unterschiede wurden statistisch ermittelt. Die Abbildungsqualitäten der DVT und CT wurden auf Grundlage einer intensiven Literaturrecherche verglichen. Die Ergebnisse dieser Studie stellten signifikante Unterschiede in den röntgenologischen Eigenschaften von OD und OF heraus. Acht von zehn Strukturen zeigten in den DVT-Aufnahmen eine signifikant bessere Abbildungsqualität im Vergleich zu den OPG-Aufnahmen. Die teilweise gravierenderen Befunde in den DVT-Aufnahmen deuteten auf eine Unterinterpretation dieser Befunde im OPG hin. Die Literaturrecherche zu Gegenüberstellungen der Abbildungsqualitäten in CT und DVT wies nahezu ausnahmslos auf eine Überlegenheit der DVT hin.

A exodontia é o procedimento cirúrgico odontológico bastante praticado pelo Cirurgião Dentista clínico geral e pelo especialista quando, por diversos motivos, o elemento dentário necessita ser avulsionado. Atualmente a literatura ressalta enfaticamente a importância da preservação do rebordo alveolar durante o planejamento cirúrgico da exodontia, no que tange ao uso de técnicas cirúrgicas minimamente traumáticas, bem como o tratamento dado ao alvéolo fresco. Este estudo caso controle verifica variações das dimensões alveolares horizontais em alvéolos de dentes homólogos anteriores superiores, onde se realizou a manobra de Chompret (controle) e alvéolos onde esta não foi realizada (teste), ao final de um intervalo de sete dias pós operatórios, e conclui que há uma alteração dimensional média de 6,2% em espessura na parte coronária do alvéolo (p=0,003), quando se faz a manobra, também conhecida por compressão alveolar bidigital pós exodontia. O paciente necessita e deve ser reabilitado para que possa, dentro dos limites protéticos, voltar a ter suas funções mastigatória, estética e dictiva restauradas, o que nos compromete a espoliar ao mínimo suas estruturas ósseas remanescentes. / Tooth extraction is a surgical dental procedure always performed by general dentists and specialists when a tooth requires extraction, by several causes. Actually dental literature enphasizes alveolar ridge preservation importance during surgical planning to teeth extraction considering minimally traumatic surgical skill and the treatment gave to fresh socket. This case control study verifies horizontal alveolar dimensions in homologues upper anterior tooth extracted alveoli, in which Chomprets maneuver, known by post-extraction alveolar compression, was performed (Control) and alveoli in which this one was not performed (Test), in a post-operative seven days gap of time, and concludes that there is width dimensional difference of 6,2% in the alveolus coronary section (p=0.003) when the maneuver is done. Patients must be rehabilited to can, inside prosthetics limits, to chew, to speak, to smile, to get aesthetics, what compromises us to prevent damages to remaining bone structures during tooth extraction and post-extraction socket procedures.

A exodontia é o procedimento cirúrgico odontológico bastante praticado pelo Cirurgião Dentista clínico geral e pelo especialista quando, por diversos motivos, o elemento dentário necessita ser avulsionado. Atualmente a literatura ressalta enfaticamente a importância da preservação do rebordo alveolar durante o planejamento cirúrgico da exodontia, no que tange ao uso de técnicas cirúrgicas minimamente traumáticas, bem como o tratamento dado ao alvéolo fresco. Este estudo caso controle verifica variações das dimensões alveolares horizontais em alvéolos de dentes homólogos anteriores superiores, onde se realizou a manobra de Chompret (controle) e alvéolos onde esta não foi realizada (teste), ao final de um intervalo de sete dias pós operatórios, e conclui que há uma alteração dimensional média de 6,2% em espessura na parte coronária do alvéolo (p=0,003), quando se faz a manobra, também conhecida por compressão alveolar bidigital pós exodontia. O paciente necessita e deve ser reabilitado para que possa, dentro dos limites protéticos, voltar a ter suas funções mastigatória, estética e dictiva restauradas, o que nos compromete a espoliar ao mínimo suas estruturas ósseas remanescentes. / Tooth extraction is a surgical dental procedure always performed by general dentists and specialists when a tooth requires extraction, by several causes. Actually dental literature enphasizes alveolar ridge preservation importance during surgical planning to teeth extraction considering minimally traumatic surgical skill and the treatment gave to fresh socket. This case control study verifies horizontal alveolar dimensions in homologues upper anterior tooth extracted alveoli, in which Chomprets maneuver, known by post-extraction alveolar compression, was performed (Control) and alveoli in which this one was not performed (Test), in a post-operative seven days gap of time, and concludes that there is width dimensional difference of 6,2% in the alveolus coronary section (p=0.003) when the maneuver is done. Patients must be rehabilited to can, inside prosthetics limits, to chew, to speak, to smile, to get aesthetics, what compromises us to prevent damages to remaining bone structures during tooth extraction and post-extraction socket procedures.