The degree of mineral liberation is important for the efficiency of subsequent physical separation processes such as froth flotation. Mineral liberation studies involve determining the volumetric abundance or volumetric grade distribution of a specific mineralogical phase in a particular mineral. Currently, methodologies for assessing mineral liberation are laborious regarding sample preparation, analysis time (from weeks to months), and the need for stereological correction. These constraints can be eliminated by using X-ray CT which gives the cross-sections directly from three-dimensional data in shorter time (from ten minutes to hours) with minimal sample preparation. X-ray computed tomography (CT) is a non-destructive technique which allows three-dimensional visualisation of inner structures of an object based on the variations in density and atomic composition. Initially, it was developed as a medical tool for imaging soft tissue and bone. During the last decade, the number of X-ray CT applications in engineering and geology has steadily increased, with the improvements in performance and imaging capabilities. The aim of the present work is to apply X-ray CT technique for finely divided ore samples and to study the relationship between mineral liberation and CT results. Four different ore types were used in this study: Northparkes ore (Australia), Ernest Henry ore (Australia), Keetac ore (USA) and Cannington ore (Australia). Different settings of the desktop X-ray CT technique were applied for each particular ore sample for several ore liberation (particle size distribution) properties. Two dimensional CT images were reconstructed from the three-dimensional X-ray CT data. It was found that the settings for CT technique were a function of the ore type. Particularly in the case of Cannington (high density ore) the best setting conditions split from the rest of the ores tested. The appearance of different artifacts occurring during the analysis were studied and kept to the minimum. A functionality between mineral liberation and CT results was found. The variables affecting the most the results were the Voltage and Minimum Intensity Percentage. Contrary to the expected trends, variables having a negligible effect on the results were found to be exposure time / equivalent Al filter thickness.

The degree of mineral liberation is important for the efficiency of subsequent physical separation processes such as froth flotation. Mineral liberation studies involve determining the volumetric abundance or volumetric grade distribution of a specific mineralogical phase in a particular mineral. Currently, methodologies for assessing mineral liberation are laborious regarding sample preparation, analysis time (from weeks to months), and the need for stereological correction. These constraints can be eliminated by using X-ray CT which gives the cross-sections directly from three-dimensional data in shorter time (from ten minutes to hours) with minimal sample preparation. X-ray computed tomography (CT) is a non-destructive technique which allows three-dimensional visualisation of inner structures of an object based on the variations in density and atomic composition. Initially, it was developed as a medical tool for imaging soft tissue and bone. During the last decade, the number of X-ray CT applications in engineering and geology has steadily increased, with the improvements in performance and imaging capabilities. The aim of the present work is to apply X-ray CT technique for finely divided ore samples and to study the relationship between mineral liberation and CT results. Four different ore types were used in this study: Northparkes ore (Australia), Ernest Henry ore (Australia), Keetac ore (USA) and Cannington ore (Australia). Different settings of the desktop X-ray CT technique were applied for each particular ore sample for several ore liberation (particle size distribution) properties. Two dimensional CT images were reconstructed from the three-dimensional X-ray CT data. It was found that the settings for CT technique were a function of the ore type. Particularly in the case of Cannington (high density ore) the best setting conditions split from the rest of the ores tested. The appearance of different artifacts occurring during the analysis were studied and kept to the minimum. A functionality between mineral liberation and CT results was found. The variables affecting the most the results were the Voltage and Minimum Intensity Percentage. Contrary to the expected trends, variables having a negligible effect on the results were found to be exposure time / equivalent Al filter thickness.

The degree of mineral liberation is important for the efficiency of subsequent physical separation processes such as froth flotation. Mineral liberation studies involve determining the volumetric abundance or volumetric grade distribution of a specific mineralogical phase in a particular mineral. Currently, methodologies for assessing mineral liberation are laborious regarding sample preparation, analysis time (from weeks to months), and the need for stereological correction. These constraints can be eliminated by using X-ray CT which gives the cross-sections directly from three-dimensional data in shorter time (from ten minutes to hours) with minimal sample preparation. X-ray computed tomography (CT) is a non-destructive technique which allows three-dimensional visualisation of inner structures of an object based on the variations in density and atomic composition. Initially, it was developed as a medical tool for imaging soft tissue and bone. During the last decade, the number of X-ray CT applications in engineering and geology has steadily increased, with the improvements in performance and imaging capabilities. The aim of the present work is to apply X-ray CT technique for finely divided ore samples and to study the relationship between mineral liberation and CT results. Four different ore types were used in this study: Northparkes ore (Australia), Ernest Henry ore (Australia), Keetac ore (USA) and Cannington ore (Australia). Different settings of the desktop X-ray CT technique were applied for each particular ore sample for several ore liberation (particle size distribution) properties. Two dimensional CT images were reconstructed from the three-dimensional X-ray CT data. It was found that the settings for CT technique were a function of the ore type. Particularly in the case of Cannington (high density ore) the best setting conditions split from the rest of the ores tested. The appearance of different artifacts occurring during the analysis were studied and kept to the minimum. A functionality between mineral liberation and CT results was found. The variables affecting the most the results were the Voltage and Minimum Intensity Percentage. Contrary to the expected trends, variables having a negligible effect on the results were found to be exposure time / equivalent Al filter thickness.

The degree of mineral liberation is important for the efficiency of subsequent physical separation processes such as froth flotation. Mineral liberation studies involve determining the volumetric abundance or volumetric grade distribution of a specific mineralogical phase in a particular mineral. Currently, methodologies for assessing mineral liberation are laborious regarding sample preparation, analysis time (from weeks to months), and the need for stereological correction. These constraints can be eliminated by using X-ray CT which gives the cross-sections directly from three-dimensional data in shorter time (from ten minutes to hours) with minimal sample preparation. X-ray computed tomography (CT) is a non-destructive technique which allows three-dimensional visualisation of inner structures of an object based on the variations in density and atomic composition. Initially, it was developed as a medical tool for imaging soft tissue and bone. During the last decade, the number of X-ray CT applications in engineering and geology has steadily increased, with the improvements in performance and imaging capabilities. The aim of the present work is to apply X-ray CT technique for finely divided ore samples and to study the relationship between mineral liberation and CT results. Four different ore types were used in this study: Northparkes ore (Australia), Ernest Henry ore (Australia), Keetac ore (USA) and Cannington ore (Australia). Different settings of the desktop X-ray CT technique were applied for each particular ore sample for several ore liberation (particle size distribution) properties. Two dimensional CT images were reconstructed from the three-dimensional X-ray CT data. It was found that the settings for CT technique were a function of the ore type. Particularly in the case of Cannington (high density ore) the best setting conditions split from the rest of the ores tested. The appearance of different artifacts occurring during the analysis were studied and kept to the minimum. A functionality between mineral liberation and CT results was found. The variables affecting the most the results were the Voltage and Minimum Intensity Percentage. Contrary to the expected trends, variables having a negligible effect on the results were found to be exposure time / equivalent Al filter thickness.

The degree of mineral liberation is important for the efficiency of subsequent physical separation processes such as froth flotation. Mineral liberation studies involve determining the volumetric abundance or volumetric grade distribution of a specific mineralogical phase in a particular mineral. Currently, methodologies for assessing mineral liberation are laborious regarding sample preparation, analysis time (from weeks to months), and the need for stereological correction. These constraints can be eliminated by using X-ray CT which gives the cross-sections directly from three-dimensional data in shorter time (from ten minutes to hours) with minimal sample preparation. X-ray computed tomography (CT) is a non-destructive technique which allows three-dimensional visualisation of inner structures of an object based on the variations in density and atomic composition. Initially, it was developed as a medical tool for imaging soft tissue and bone. During the last decade, the number of X-ray CT applications in engineering and geology has steadily increased, with the improvements in performance and imaging capabilities. The aim of the present work is to apply X-ray CT technique for finely divided ore samples and to study the relationship between mineral liberation and CT results. Four different ore types were used in this study: Northparkes ore (Australia), Ernest Henry ore (Australia), Keetac ore (USA) and Cannington ore (Australia). Different settings of the desktop X-ray CT technique were applied for each particular ore sample for several ore liberation (particle size distribution) properties. Two dimensional CT images were reconstructed from the three-dimensional X-ray CT data. It was found that the settings for CT technique were a function of the ore type. Particularly in the case of Cannington (high density ore) the best setting conditions split from the rest of the ores tested. The appearance of different artifacts occurring during the analysis were studied and kept to the minimum. A functionality between mineral liberation and CT results was found. The variables affecting the most the results were the Voltage and Minimum Intensity Percentage. Contrary to the expected trends, variables having a negligible effect on the results were found to be exposure time / equivalent Al filter thickness.

The degree of mineral liberation is important for the efficiency of subsequent physical separation processes such as froth flotation. Mineral liberation studies involve determining the volumetric abundance or volumetric grade distribution of a specific mineralogical phase in a particular mineral. Currently, methodologies for assessing mineral liberation are laborious regarding sample preparation, analysis time (from weeks to months), and the need for stereological correction. These constraints can be eliminated by using X-ray CT which gives the cross-sections directly from three-dimensional data in shorter time (from ten minutes to hours) with minimal sample preparation. X-ray computed tomography (CT) is a non-destructive technique which allows three-dimensional visualisation of inner structures of an object based on the variations in density and atomic composition. Initially, it was developed as a medical tool for imaging soft tissue and bone. During the last decade, the number of X-ray CT applications in engineering and geology has steadily increased, with the improvements in performance and imaging capabilities. The aim of the present work is to apply X-ray CT technique for finely divided ore samples and to study the relationship between mineral liberation and CT results. Four different ore types were used in this study: Northparkes ore (Australia), Ernest Henry ore (Australia), Keetac ore (USA) and Cannington ore (Australia). Different settings of the desktop X-ray CT technique were applied for each particular ore sample for several ore liberation (particle size distribution) properties. Two dimensional CT images were reconstructed from the three-dimensional X-ray CT data. It was found that the settings for CT technique were a function of the ore type. Particularly in the case of Cannington (high density ore) the best setting conditions split from the rest of the ores tested. The appearance of different artifacts occurring during the analysis were studied and kept to the minimum. A functionality between mineral liberation and CT results was found. The variables affecting the most the results were the Voltage and Minimum Intensity Percentage. Contrary to the expected trends, variables having a negligible effect on the results were found to be exposure time / equivalent Al filter thickness.

Thesis (M.S.)--University of Alabama at Birmingham, 2010. / Title from PDF title page (viewed on June 25, 2010). Includes bibliographical references (p. 29-31).

Είναι κοινά αποδεκτή η γνώμη ότι στις μέρες μας η υπολογιστική τομογραφία αποτελεί αναπόσπαστο μέσο διάγνωσης στην κλινική πράξη. Προκαταρκτικές όμως εξετάσεις ρουτίνας σε μικρά ζώα είναι επίσης ωφέλιμες με απώτερο στόχο την εφαρμογή νέων τεχνικών διάγνωσης και τη βελτίωση παλαιοτέρων, στον άνθρωπο. Αυτό τον ρόλο καλείται να παίξει η μικροτομογραφία, που ουσιαστικά αποτελεί μια παραλλαγή της κλασσικής Υπολογιστικής Τομογραφίας Κωνικής Δέσμης (CBCT). Στόχος της παρούσας διατριβής είναι η μελέτη, η ανάπτυξη, η εφαρμογή και η αξιολόγηση αλγορίθμων ανακατασκευής εικόνας μικρών ζώων και αντικειμένων, απο τις προβολικές εικόνες τους. Συνδυάζοντας προβολικά δεδομένα λήψης από διάφορες γεωμετρίες, όπως της επίπεδης ισοκεντρικής τροχιάς αλλά και της τρισορθογώνιας, της ελικοειδούς καθώς και αυτής του περιορισμένου γωνιακού κυκλικού τόξου, ανακατασκευάστηκαν λογισμικά κυρίως μοντέλα των υπό εξέταση δειγμάτων. Με απώτερο στόχο την εφαρμογή αλλά και τη βελτίωση γνωστών αλγορίθμων ανακατασκευής αλλά και τον πειραματισμό και την ανάπτυξη καινούργιων μεθόδων αναδημιουργίας στο χώρο της τομογραφίας, ένα νέο λογισμικό εργαλείο δημιουργήθηκε στα πλαίσια της διατριβής αυτής. Πρόκειται για την Υπολογιστική Βιβλιοθήκη CLCT, μια ενοποιημένη πλατφόρμα προσομοίωσης που έχει αναπτυχθεί στην αντικειμενοστραφή γλώσσα προγραμματισμού C++. Χρησιμοποιώντας το εργαλείο αυτό, είναι δυνατή η σύνθεση ενός σεναρίου υπολογιστικής τομογραφίας με χρήση των επιμέρους στοιχείων της βιβλιοθήκης. Στο πλαίσιο της βιλιοθήκης, έχει αναπτυχθεί πληθώρα εργαλείων που αφορούν την ανακατασκευή αλλά και την επεξεργασία εικόνας. Παραδείγματα χρήσης της βιβλιοθήκης αναφέρονται τόσο για την περίπτωση της μικροτομογραφίας κωνικής δέσμης (στην ανακατασκευή μοντέλων μικρών ζώων και πειραματικών δεδομένων) όσο και για άλλες γενικές εφαρμογές της κλασσικής υπολογιστικής τομογραφίας στην ιατρική. / It is common belief that nowadays Computed Tomography is an integral part of medical diagnosis. Preliminary studies on small animals are also useful as they allow applying new diagnostic techniques and imaging modalities on humans, while improving at the same time the well established traditional methods. This is a role to be played by micro Computed Tomography (μCT), a technique similar to the conventional Cone Beam CT. The aim of the current thesis is to study, develop, apply and evaluate image reconstruction algorithms using projection images of small animals and objects. Using different acquisition geometries like circular or three-orthogonal trajectories as well as helical and limited arc trajectories, reconstructions were performed using software phantoms. A new software tool, CLCT library, was created during this thesis aiming to contribute to the implementation and improvement of well-known image reconstruction algorithms but also to the experimental testing and evaluation of new image reconstruction techniques. CLCT is an object-oriented class library, implemented in C++. In the core of the library, fundamental elements are classes, tightened together in a logical hierarchy. Real world objects, like an X-Ray Source or a Flat- Detector, can be defined as instances of corresponding classes. Various utilities (like 3D transformations, loading, saving, filtering of images, creation of planar or curved objects of various dimensions) have been incorporated in the software tool as class methods. They allow the user to easily set up any arrangement of these objects in 3D space and to experiment with many different trajectories and configurations. The application of CLCT library confirms the flexibility of the approach which is presented in this thesis through simulations on software phantoms as well as on real projection data for both cases of μCT and conventional Cone Beam CT.

Orientador: Frederico Canato Martinho / Banca: Márcia Carneiro Valera Garakis / Banca: Cláudio Antonio Talge Carvalho / Banca: Luiz Alexandre Thomaz / Banca: Maria Rachel Figueiredo Penalva Monteiro / Resumo: O conhecimento da posição topográfica dos ápices dentários em relação às corticais ósseas externas e estruturas anatômicas é de importância para a endodontia, sobretudo quando da instituição de técnicas com sobreinstrumentação. A tomografia computadorizada de feixe cônico (TCFC) permite uma análise tridimensional da localização do ápice radicular, estimando os riscos em relação a essas estruturas. Os objetivos desta pesquisa foram: a) aferir a medida linear entre os ápices radiculares de dentes posteriores e canino superiores e o seio maxilar e entre os ápices de dentes posteriores inferiores e o canal mandibular, relacionando os achados com gênero e idade; b) comparar as medições realizadas em tomografias entre ápices e estruturas anatômicas, com as realizadas em radiografias panorâmicas; c) verificar a proximidade dos ápices radiculares dos dentes superiores com a respectiva cortical óssea externa adjacente e dos ápices radiculares dos dentes inferiores com as corticais ósseas externas vestibular e lingual; d) verificar a ocorrência de fenestrações apicais, em todos os grupos dentais e e) classificar riscos de sobreinstrumentação baseando-se nas medidas lineares entre ápices radiculares e estruturas anatômicas/ corticais ósseas externas. Foram selecionados 800 TCFCs e 200 radiografias panorâmicas obtidas de pacientes com indicações diversas. Na TCFC, foram encontradas médias entre os ápices radiculares e o seio maxilar, variando de 0,37mm até 6,22mm, e na mandíbula, entre o... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: It is important to know the topographic position of dental root apices in relation to external cortical bones and adjacent anatomical structures for endodontics, mainly regarding the use of over-instrumentation techniques. Cone beam computed tomography (CBCT) allows for analysis of the root apex position and estimation of the risks in relation to these structures. The objectives of this study were: a) to assess the linear measurement between root apices of posterior teeth and upper canine and maxillary sinus as well as between apices of lower posterior teeth and mandibular canal according to gender and age; b) to compare tomographic measurements of apices and anatomical structures to those from panoramic radiographs; c) to verify the proximities of the root apices of upper teeth to corresponding adjacent cortical bones and of lower teeth to buccal and lingual cortical bones; d) to verify the occurrence of apical fenestrations in all dental groups; and e) to assess the risks of overinstrumentation based on linear measurements between root apices and anatomical structures/external cortical bones. A total of 800 tomographs and 200 panoramic radiographs were selected. CBCT images showed mean distances between root apices and maxillary sinus ranging from 0.37mm to 6.22mm and between root apices and mental foramen ranging from 2.81mm to 4.92mm. By comparing the tomographs to panoramic radiographs, over-estimation and sub-estimation were found in the maxillary and mandibular measurements, respectively (P < 0.01). The distances between each root apex and corresponding cortical bone were ranked according to distance, with the majority of the apices located less than 1 mm from the cortical bone in the maxilla and greater than 3mm in the mandible. Higher rates of fenestrations were found in the maxilla, whereas lingual bone plate was more affected in the mandible. ...(Resumo completo, clicar acesso eletrônico abaixo) / Doutor

Introdução: As reabsorções radiculares internas (RRI) são lesões de difícil prognóstico e o diagnóstico é baseado em exames clínicos e de imagem. Estudos que avaliam a acurácia dos exames por imagem para a detecção de RRI, utilizam simulações realizadas por brocas, criando cavidades com forma e limites definidos diferentes da realidade clínica. Além disso, sabe-se que tão importante quanto a detecção da lesão de RRI é a capacidade de visualização do envolvimento da estrutura dentinária adjacente. Assim, este trabalho objetivou desenvolver uma nova metodologia para simulação de RRI com base na desmineralização ácida e, após, testar a influência de diferentes protocolos de aquisição de imagens tomográficas na medição do volume dessas lesões. Materiais e métodos: Foi testada uma metodologia de simulação de RRI, com ação progressiva de ácido nítrico 5% e hipoclorito de sódio 8%, em onze dentes monorradiculares. As cavidades geradas foram avaliadas em Microscopia Eletrônica de Varredura (MEV) e as medidas de diâmetro e profundidade foram correlacionadas com os tempos de ação do ácido. Imagens de Tomografia Computadorizada de Feixe Cônico (TCFC) foram adquiridas de todos os dentes da amostra em dois aparelhos, de FOV amplo e restrito, com três protocolos de tamanho de voxel cada: I-Cat Next Generation (voxel 0,200; 0,250; 0,300 mm) e Kodak 9000 3D (voxel 0,076; 0,100; 0,200 mm). As simulações de RRI foram mensuradas com uma ferramenta de cálculo de volume do software Dolphin 3D. Os valores médios de volume das cavidades foram comparados com Análise de Variância (ANOVA) e Teste Tukey ( =0,05). A validação das mensurações de volume obtidas pelo software foi realizada por meio de moldagem das cavidades com silicona de adição. Resultados: As simulações de RRI reproduziram lesões de diferentes tamanhos e com profundidades de 0.22 mm a 1.59 mm. Em relação às medidas volumétricas, não houve diferença estatística significante (P<0,05) entre os volumes de RRI mensurados a partir dos dois menores tamanhos de voxel em cada aparelho de TCFC, mas ambos foram diferentes estatisticamente (P>0,05) do volume calculado com os maiores tamanhos de voxel. Ainda, as médias de volume a partir das impressões em silicona foram menores que as mensuradas pelo voxel 0,200 mm. Conclusão: A metodologia de simulação de RRI proposta gerou cavidades com limites irregulares e com razão de diâmetro:profundidade mais semelhante ao processo de RRI in vivo. Diferentes protocolos de TCFC influenciam nas medidas de volume de RRI simuladas, ressaltando a importância da padronização na aquisição das imagens para acompanhamento dessas lesões. / Introduction: The internal root resorption (IRR) injuries are difficult to predict and the diagnosis is based on clinical and radiographic examination. Studies that evaluated the accuracy of imaging tests for the detection of IRR using simulations produced by burs, created cavities with different forms and limits of clinical reality. Furthermore, it is known that as important as the IRR detection is the ability to preview the involvement of adjacent dentinal structure. Thus, this study aimed to develop a new methodology for IRR simulation-based with acid demineralization and after investigate the influence of different tomographic protocols in the measurement of the IRR lesions volume. Materials and methods: A methodology was desenvolved for simulation of IRR with progressive action of 5% nitric acid and 8% sodium hypochlorite in eleven teeth single-rooted. IRR cavities produced were evaluated by scanning electron microscopy (SEM), measured in diameter and depth and after correlated with the acid times. Cone Beam Computed Tomography (CBCT) images were acquired of all teeth in two tomography devices, with large and restrict field of view (FOV) using three voxel sizes protocols: I-Cat Next Generation (voxel 0.200, 0.250, 0.300 mm) and Kodak 9000 3D (voxel 0.076, 0.100, and 0.200 mm). IRR simulations were measured with a tool for calculating volume of the Dolphin 3D software. Volume means of the IRR cavities were compared using Analysis of Variance (ANOVA) and Tukey test ( = 0.05). A validation of the tomographic measurements was performed with addition silicone impression. Results: The simulations reproduced IRR lesions with different sizes and depths (0.22mm to 1.59mm). Regarding volumetric measurements, there was no statistically significant (P<0,05) difference between the IRR volumes measured from the two smaller voxel sizes in each CBCT device, but both were statistically different (P>0,05) from the calculated volume with larger voxel sizes. Still, the volume means from silicone impressions were lower than those measured at 0.200 mm voxel. Conclusion: The IRR simulation methodology generated cavities with irregular borders and diameter:depth ratio more similar to in vivo process of IRR. Different protocols of CBCT influences the volume measures of IRR simulated, emphasizing the importance of standardization in the acquisition of CBCT images for monitoring these lesions.