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Gao, Bo. "Multigrid reconstruction of micro-CT data." Thesis, KTH, Skolan för teknik och hälsa (STH), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-211180.
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The group of Medical Imaging at School of Health and Technology is developing a micro-CT scanner for small animal imaging. Micro-CT refers to reconstructing CT image with resolution in scale of micrometer, and this goal is achieved by acquiring projection data with high resolution. Nevertheless, high resolution projection data and high resolution recon- struction image have introduced the problem of memory insufficiency, as more points need to be processed during micro-CT reconstruction. For this reason, this paper has investigated how to alleviate the burden on computers memory through applying multi-grid reconstruction algo- rithms, which means to reconstruct region of interest (ROI) with high resolution while reconstructing background with lower resolution. By do- ing that, pixels being considered in the reconstruction space has been decreased and normal computers will be capable to handle reconstruction of micro-CT image. Through testing on numerical data (Shepp Logan Phantom), it can be concluded that multi-grid reconstruction algorithm could reconstruct high fidelity ROI with much faster speed comparing to full resolution reconstruction. Moreover, this proposed technique can also give decent reconstruction to data acquired from micro-CT scanner.
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Sen, Sharma Kriti. "Compressed Sensing based Micro-CT Methods and Applications." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/52866.
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High-resolution micro computed tomography (micro-CT) offers 3D image resolution of 1 um for non-destructive evaluation of various samples. However, the micro-CT performance is limited by several factors. Primarily, scan time is extremely long, and sample dimension is restricted by the x-ray beam and the detector size. The latter is the cause for the well-known interior problem. Recent advancement in image reconstruction, spurred by the advent of compressed sensing (CS) theory in 2006 and interior tomography theory since 2007, offers great reduction in the number of views and an increment in the volume of samples, while maintaining reconstruction accuracy. Yet, for a number of reasons, traditional filtered back-projection based reconstruction methods remain the de facto standard on all manufactured scanners.
This work demonstrates that CS based global and interior reconstruction methods can enhance the imaging capability of micro-CT scanners. First, CS based few-view reconstruction methods have been developed for use with data from a real micro-CT scanner. By achieving high quality few-view reconstruction, the new approach is able to reduce micro-CT scan time to up to 1/8th of the time required by the conventional protocol. Next, two new reconstruction techniques have been developed that allow accurate interior reconstruction using just a limited number of global scout views as additional information. The techniques represent a significant progress relative to the previous methods that assume a fully sampled global scan. Of the two methods, the second method uses CS techniques and does not place any restrictions on scanning geometry. Finally, analytic and iterative reconstruction methods have been developed for enlargement of the field of view for the interior scan with a small detector. The idea is that truncated projections are acquired in an offset detector geometry, and the reconstruction procedure is performed through the use of a weighting function / weighted iteration updates, and projection completion. The CS based reconstruction yields the highest image quality in the numerical simulation. Yet, some limitations of the CS based techniques are observed in case of real data with various imperfect properties. In all the studies, physical micro-CT phantoms have been designed and utilized for performance analysis. Also, important guidelines are suggested for future improvements.Ph. D.
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Sharma, Yash. "Automated fibre segmentation in micro CT images of paper." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50044.
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Characterizing the structure of paper products made from Northern Bleached Softwood Kraft (NBSK) pulp after Low Consistency refining is a vital step to understanding the strengthening mechanisms of NBSK fibres as well as the effect of refining on the fibre morphology. X-ray micro tomographic (µCT) imaging coupled with advanced image analysis enables the characterization of the internal structure of paper at a very high resolution in 3D.
In this work, a novel algorithm has been developed to isolate individual papermaking fibres in µCT images of paper handsheets as a first step to characterize the paper structure. The three step fibre segmentation algorithm segments the papermaking fibres by (i) tracking the hollow inside the fibres via a modified connected component methodology, (ii) extracting the fibre walls using a distance transform and (iii) labeling the fibres through collapsed sections by a final refinement step. Further, post processing algorithms have been developed to calculate the length, coarseness and relative bonded area of the fibres thus segmented. The algorithms have been validated by segmenting hollow aluminum tubes in test geometry similar in complexity to the paper structure. The capabilities and limitations of the algorithms have been evaluated by segmenting 2484 papermaking fibres within a 1mm x 1mm handsheet sample manufactured from NBSK pulp.
The Fibre Segmentation algorithm is the first ever reported method for the automated and robust segmentation of the tortuous 3D morphology of papermaking fibres within 3D images of paper handsheets. The segmented structure thus obtained provides the capabilities to calculate several important properties of paper. The fibre segmentation algorithm is a unique and powerful tool to analyze the paper structure and provide novel insights into the papermaking process.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Zainon, Rafidah Binti. "Spectral Micro-CT Imaging of Ex Vivo Atherosclerotic Plaque." Thesis, University of Canterbury. Physics and Astronomy, 2012. http://hdl.handle.net/10092/7165.
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The goal of this research was to demonstrate the potential of spectral CT for the discrimination of vulnerable atherosclerotic plaques. It was proposed that spectral CT has the potential to identify the presence of specific markers for vulnerable plaques: iron deposits and lipid core. A spectral micro-CT system incorporating the latest Medipix spectroscopic photon- counting detectors was commissioned for this purpose. Using spectroscopic methods developed with this system, it was possible to distinguish the presence of iron deposits and lipid core within ex vivo atherosclerotic plaques. Atherosclerosis or hardening of arteries is a systemic disease of the vessel wall that occurs in the aorta, carotid, coronary and peripheral arteries. It is characterised by the deposition of calcified plaques on the innermost layer of the artery wall. Vulnerable plaques are unstable, prone to rupture and put the person at risk of cardiovascular events and strokes. Factors that may lead to plaque instability are lipid content and iron deposits. This preclinical study is a precursor to the development of a clinical technique that will enable vulnerable atherosclerotic plaques to be identified in vivo prior to treatment or removal. Following a preliminary study on atherosclerotic plaques with a prototype system, the MARS-CT3 spectral micro-CT system incorporating Medipix3 was developed and commissioned for further plaque studies. The spectral CT data sets acquired by this system were assessed visually for morphology and analysed for material composition using a linear algebra method. The results were correlated with photography and histology (the histology is the current gold standard).
The presence of iron and lipid can be differentiated from the background soft-tissue using a linear algebra method. However the quantification of iron in the presence of calcium is not currently possible without additional data or constraints. Nevertheless the presence of iron deposits within the plaques can be distinguished in the high resolution MARS-CT images and has been correlated with photographic and histological evidence. Thus, using the high spatial resolution spectral data from MARS-CT, the discrimination of lipid core and iron deposits within ex vivo advanced human atherosclerotic plaques is feasible. This may provide the basis for the development of a clinical technique that will identify vulnerable plaques in vivo by high resolution spectral CT.
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Opie, Alexander M. T. "Contributions to spectral CT." Thesis, University of Canterbury. Electrical and Computer Engineering, 2013. http://hdl.handle.net/10092/8532.
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Spectral x-ray computed tomography (CT) is an important nascent imaging modality with several exciting potential applications. The research presented in this thesis separates into two primary areas with the common underlying theme of spectral CT; the first area is Compton scatter estimation and the second is interior tomography.
First, the research is framed and outputs are identified. Background on the concepts used in the thesis is offered, including x-ray imaging and computed tomography, CT scanner architecture, spectral imaging, interior tomography and x-ray scatter. The mathematical background of techniques for image reconstruction from x-ray transmission measurements are presented. Many of the tools used to perform the research, both hardware and software, are described. An algorithm is developed for estimating the intensity of Compton scattered photons within a spectral CT scan, and a major approximation used by the algorithm is analysed. One proposed interior reconstruction algorithm is briefly evaluated; while this is not directly linked to spectral CT, it is related to the work on a novel hybrid spectral interior micro-CT architecture. Conclusions are summarised and suggestions for future work are offered.
Scatter is known to cause artefacts in CT reconstructions, and several methods exist to correct data that has been corrupted by scatter. Compton scatter affects the energy of photons, therefore spectral CT measurements offer the potential to correct for this phenomenon more accurately than conventional measurements. A Compton scatter algorithm is developed and is found to match very well to Monte Carlo validation simulations, with the constraints that the object be at the micro-CT scale and that electron-binding effects are omitted. Development of the algorithm uses an approximation of the post-scatter attenuation to simplify the estimation problem and enable implementation. The consequences of this approximation are analysed, and the error introduced is found to be less than 5% in most biomedical micro-CT situations.
Interior tomography refers to the incomplete data situation caused by the truncation of some or all CT projections, and is an active research area. A recently proposed interior reconstruction algorithm is evaluated with regard to its sensitivity to input error, and is found to have mediocre performance in this respect. Published results are not found to be reproducible, suggesting some omission from the published algorithm.
A novel hybrid spectral interior architecture is described, along with an iterative reconstruction algorithm for hybrid data sets. The system combines a full field of view conventional imaging chain and an interior field of view spectral imaging chain to enable spectral measurement of a region of interest, and addresses some important limitations of spectral x-ray detectors; promising results are shown. Spectral reconstructions from interior data are shown to have sufficient information to distinguish two k-edge contrast agents (iodine and gadolinium) not only within the interior field of view but also beyond it. The architecture is further explored in the context of radiation exposure reduction, including testing of an analytical hybrid reconstruction algorithm.
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Gomes, Mauricio Neves. "Desproteinização do esmalte associada à técnica de remineralização no clareamento em consultório." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/23/23140/tde-30112011-164218/.
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Objetivo: avaliar cor, brilho, rugosidade e alterações ultraestruturais do esmalte dental clareado com peróxido de hidrogênio a 35 %, submetido ao tratamento prévio com agente desproteinizante, ou ao tratamento posterior com o agente remineralizador fosforopeptídeo de caseína/fosfato de cálcio amorfo (ACP-CPP). Material e Métodos: Os grupos experimentais foram: GC (controle/consultório): H2O2 a 35 % - 4 sessões de 8 min; GE1 (primer+consultório): NaOCl 5,25 % por 1 min, aplicação do H2O2 a 35 % como no GC; e GE2 (consultório+ACP): GC + ACP-CPP diariamente por 7 dias. Fragmentos contendo esmalte e dentina (n=8), obtidos de dentes bovinos, foram utilizados para avaliar cor, brilho e a rugosidade. Alteração de cor (E), parâmetros L* e b* foram determinados com colorímetro e o brilho superficial com glossímetro antes, imediatamente após (1h), 4 e 7 dias após o tratamento. Parâmetros de rugosidades, Ra, Rt e RSm, foram obtidos com perfilômetro de contato antes, imediatamente após o tratamento e 7 dias após os tratamentos. Os resultados de E, brilho superficial e rugosidade foram avaliados separadamente usando ANOVA 2 fatores e teste de Tukey (p=0,05). Para avaliar a alteração ultraestrutural, dentes pré-molares humanos, seccionados nos sentidos vestibulo-lingual e mesio distal foram observados em microscópio eletrônico de varredura, por emissão de campo, e realizada a quantificação de elementos químicos por EDS. Análise tridimensional da estrutura do esmalte foi realizada por microtomografia computadorizada (micro-CT) com resolução 11,24 m (n=8). Foram realizadas análises dos parâmetros estruturais: espessura estrutural (St.Th.), separação estrutural (St.Sp.) e índice de fragmentação (Fr.I.) antes e após os tratamentos em duas regiões: ROI 1= 56,2 m e ROI 2= 110,2 m, ambas a partir da superfície vestibular. Foi utilizado o teste t pareado para análise estatística de cada parâmetro estrutural. Resultados: Não houve diferença estatística entre os diferentes tratamentos de superfície para E, Ra e RSm. Imediatamente após o clareamento (1h) ocorreu maior aumento do L* e queda do brilho superficial que se manteve por 7 dias. O uso de agente desproteinizante em dentes bovinos não acentuou a redução do brilho do esmalte, mas a aplicação de ACP-CPP acarretou em maior perda brilho e aumento nos valores de rugosidade após 7 dias para Rt. A aplicação do agente desproteinizante previamente ao clareamento em dente humano revelou uma superfície mais lisa, sem alterar os parâmetros estruturais. Há uma maior quantidade de cálcio, formação de um manto de recobrimento após aplicação de ACP-CPP em torno dos prismas de esmalte, aumento de St.Th de 4,1m, menor espaçamento entre os cristais de hidroxiapatita e redução de St.Sp em 0,8 m e de Fr.I em 0,01 no ROI-1 após 7 dias. Conclusão: O uso de agente desproteinizante não altera a cor, brilho e a ultraestrutura inorgânica. A aplicação de ACP-CPP após a técnica de clareamento de consultório não contribui para alteração de cor, mas reduz o brilho e altera a ultraestrutura da porção mais externa do esmalte após 7 diasPurpose: To evaluate color, gloss, roughness and ultrastructural changes of enamel bleached with 35% hydrogen peroxide, subjected to previous treatment with deproteinized agent, or later treatment with remineralizing agent casein phosphopeptide-amorphous calcium phosphate (CPP-ACP). Materials and Methods: The experimental groups were: GC (control + in-office): 35% H2O2 - 4 sessions of 8 min; GE1(primer+in-office): 5.25% NaOCl during 1 min before the application of 35% H2O2 as done in GC, and GE2 (in-office+ACP-CPP): GC + ACP-CPP, daily applied during 7 days. Enamel and dentin blocks (n=8), obtained from bovine tooth, were used to evaluate color, gloss and roughness. Color changes (E), L* and b* parameters were done with a colorimeter and surface gloss with a glossimeter, before, immediately after (1h), 4 and 7 days after treatment. Roughness parameters, Ra, RT and Rsm, were done with a contact perfilometer before, immediately after and 7 days after treatments. ANOVA two-way and Tukeys test were performed to evaluate E, gloss and roughness separately (p=0.05). To access human pre-molar ultrastructural changes, teeth were cross-sectioned buccal-lingual and disto-mesio observed by scanning electron microscope, field emission gun, EDS to quantify chemical elements. Enamel three-dimensional images were analysed with microcomputed tomography (micro-CT) with resolution 11,24m (n=8). Structural parameters were analyzed: structural thickness (St.Th.), structural separation (St.Sp.) and fragmentation index (Fr.I.) before and after treatments in two regions of interest:ROI 1= 56,2m and ROI 2= 110,2 m, both from buccal surface. Paired t-test was done for analyses of each structural parameter. Results: There was no statistical difference among surface treatments to E, Ra and Rsm. Immediately after bleaching (1h) occured highest L* increase and decrease of surface gloss which remained until 7 days. Deproteinized agent applied on bovine tooth not emphasized enamel gloss reduction, but the CPP-ACP has resulted in a higher gloss reduction and roughness increase (Rt parameter) after 7 days. Deproteinized agent application previous to in- office bleaching observed a smooth surface, without structural parameters changes. There is a greater calcium quantity, forming a cover mantle after CPP-ACP application around enamel prisms, St.Th increase of 4,1m, less spacing between hydroxyapatite crystals and reductions of St.Sp of 0,8 m and Fr.I of 0,01 on ROI-1 after 7 days. Conclusion: Application of deproteinized agent does not change bovine enamel color, gloss and human enamel inorganic ultrastructure. CPP-ACP application after in-office bleaching does not contribute to color change, but decrease gloss of bovine enamel and change human enamel outermost ultrastructure portion after 7 days.
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Iglecias, Elaine Faga. "Avaliação qualitativa e quantitativa da instrumentação e obturação de canais radiculares achatados utilizando-se microtomografia computadorizada." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/23/23145/tde-19022015-172359/.
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Na Endodontia, a microtomografia (CT) tem sido amplamente utilizada como método de análise tridimensional. Atualmente, três movimentos mecanizados para o preparo do canal radicular tem sido introduzidos na rotina endodôntica, oscilatório, rotatório e recíproco. Existem diferentes sistemas de limas acionadas por motores capazes de realizar esses movimentos. Sendo assim, os objetivos deste trabalho são utilizar a CT para avaliar, em canais mesiais achatados de molares inferiores, a qualidade e modelagem final de preparo do canal radicular, utilizando-se sistemas oscilatório, recíproco e rotatório e avaliar a obturação do canal radicular com cone único ou ondas contínuas de condensação, no que diz respeito ao volume de material obturador e de espaços vazios. Os resultados não mostraram diferença estatísitica significativa no volume de desgaste entre os grupos testados. Para a porcentagem de superfície não tratada os grupos oscilatório e rotatório tocaram mais paredes nos terços cervical e médio do que o grupo recíproco. A técnica de ondas contínuas de condensação e cone único apresentaram preenchimento de obturação semelhantes nos terços médio e apical, sendo que no terço cervical a técnica de ondas contínuas deixou menor porcentagem de espaços vazios.Endodontics in the microtomography (CT) has been widely used as a method for three-dimensional analysis. Currently, three mechanized movements for root canal preparation has been introduced in endodontic, oscillatory, rotational and reciprocal routine. There are different files systems driven by motors capable of these movements. Thus, the objectives of this work are using CT to evaluate, in flattened mesial canals of mandibular molars, the quality and final modeling of root canal preparation, using oscillatory, reciprocal and rotational systems and evaluate the root canal filling with single cone or continuous waves of condensation, with respect to the volume of filling material and voids. The results showed no significant difference in estatísitica wear volume between the tested groups. For the percentage of untreated surface and the oscillating rotating groups played more walls in the cervical and middle thirds of the reciprocal group. The technique of continuous wave of condensation and single cone showed similar fillings fill in the middle and apical thirds, and in the cervical third of the technique of continuous wave left lower percentage of voids.
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Robertson, Galen Charles. "Quantification of Skeletal Phenotype Using Micro-CT and Mechanical Testing." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4874.
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With the vast array of genetically altered (knockout) mice becoming available there is a need for quantitative, repeatable, and efficient methodologies to characterize the phenotypic consequences of knocking out specific genes. Since knockout animals often have the ability to compensate for a single missing gene, it is important to examine the structural, material and morphological properties to obtain a thorough understanding of the changes occurring. For this project, femurs of knockout mice were first scanned using microcomputed tomography (micro-CT) to obtain high-resolution images of the trabecular bone in the distal femur, as well as cortical bone in the mid-diaphysis. After scanning, the femurs were tested to destruction in four-point bending at the mid-diaphysis about the medial lateral axis of the femur. These methodologies allowed quantification of (1) morphologic properties such as bone volume fraction, trabecular properties and 2nd moment of the area (2) structural properties such as stiffness, maximum load at failure, and post yield deformation and (3) material properties such as bone mineral density, elastic modulus and yield strength.
As part of two independent studies, two different knockout mice, cyclooxygenase-2 (COX-2 -/-) and Apolipoprotein E (APOE -/-), were examined for structure-function relationships using these methodologies. COX-2 knockout mice were found to have decreased mineral content in their femurs, and increased post yield deformation. APOE knockout mice at 10 weeks of age had decreased bone mass and structural properties. However, by 40 weeks of age APOE deficient mice caught up to and exceeded the structural properties and bone mass of their wild type counterparts.
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Cahoon, Lindsey Charlene. "Micro-CT Inspection of Impact Damage in Carbon/Epoxy Rods." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6350.
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Various configurations of unidirectional carbon/epoxy composite rods were impacted radially, inspected using micro-CT scanning equipment, and tested in axial compression to measure the residual strength after impact. This data was used to correlate the relationship between impact energy, residual strength, and the peak crack area and total crack volume along the length of the specimens. These specimens represent local members of open three-dimensional composite lattice structures (e.g., based on isogrid or IsoTruss® geometries) that are continuously fabricated using advanced three-dimensional braiding techniques. The specimens were radially impacted with 2.5 J (1.9 ft-lbs), 5.0 J (3.7 ft-lbs), 7.5 J (5.6 ft-lbs), 10 J (7.4 ft-lb), 15 J (11 ft-lbs), and 20 J (15 ft-lbs) of energy, and compared to undamaged control specimens. The unidirectional core specimens were 8 mm (5/16") in diameter and were consolidated with various sleeve configurations and materials. Sleeves differed in types (bi-directional braided sleeves or unidirectional spiral wraps), nominal sleeve coverage of the core fibers (full or half), and sleeve material (Nomex Thread or Dunstone Hi-Shrink Tape). The unsupported length of the specimens used in this research was 50.8 mm (2") to ensure a strength-controlled compression failure rather than a failure due to buckling. After impact, the specimens were scanned using a micro-CT scanner at resolutions of 50 and 35 microns and subsequently tested in axial compression. The micro-CT scan images were analyzed to measure the crack areas along the specimen. From this analysis, the peak crack area and total crack volume along the length of the specimen was calculated. Similar to past research, as the impact energy increases, the residual compression-strength-after-impact decreases. As the impact energy increases, specimens with shrink tape sleeves had the largest increase in peak crack area and overall crack volume while specimens with full spiral sleeves had the lowest increase in peak crack area and overall crack volume. A bimodal increase is evident in the peak crack area and total crack volume over the length of the specimen where specimens impacted at 15 J (11 ft-lbs) showed the highest peak crack area across all sleeve types. There is a slight correlation between the increase in peak crack area and overall crack volume and the decrease in residual compression strength after impact. Shrink Tape, while yielding a higher quality specimen with greater compression strength prior to impact, did not protect the specimens against damage due to impact as well as other sleeve types. This was shown by the large decrease in residual compression strength after impact and increase in peak crack area and overall crack volume as the impact energy increased.
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SERRA, FRANCESCA GIULIA. "Bone-like inducing grafts: in vivo and micro-CT analysis." Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2858349.
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taha, Nada. "3D RECONSTRUCTION OF MICRO CT IMAGES FOR SINGLE PHOTON PROCESSING SYSTEM." Thesis, Mittuniversitetet, Institutionen för informationsteknologi och medier, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-20028.
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David, Alfaro. "Micro-CT measurement of the internal fit of lithium disilicate crowns." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44929.
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The introduction of digital impressions into the field of dentistry has begun the era of entirely computer assisted crown fabrication. The aim of this study was to assess the internal fit of lithium disilicate crowns fabricated using this novel impression technology and to compare their fit to the fit of crowns obtained by traditional elastomeric impressions. Thus, 15 lithium disilicate crowns were fabricated using an entirely digital workflow (impression and fabrication), 15 lithium disilicate crowns were fabricated manually from digital impressions, and 15 lithium disilicate crowns were fabricated using a “traditional” manual process. For the fabrication of the crowns, tooth #15 was prepared for an all-ceramic restoration on an ivorine typodont, which in turn was digitized and a replica milled in zirconia. This master zirconia model and die were then utilized for the impression procedures. Duplicate dies of the master zirconia die were made in polyurethane, enabling the internal fit of each crown to be evaluated via micro CT analysis, due to the contrast in radioopacity between the ceramic, die and internal space. The total volume of the internal space (gap), the mean and maximum thickness of the gap, and the percentage of the gap that was at or below 120um thickness were calculated and evaluated statistically via one-way ANOVA, with post-hoc Scheffé analysis. The results demonstrated that the lithium disilicate crowns fabricated from digital impressions resulted in a smaller internal space, and therefore more intimate fit, in comparison to the lithium disilicate crowns fabricated via the traditional manual approach. Three-dimensional renderings of the internal space were also created, allowing for a descriptive analysis of the distribution of this internal space.
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Qaseminejad, Raeini Ali. "Modelling multiphase flow through micro-CT images of the pore space." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/11617.
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We present a numerical method for modelling two-phase flow through porous media directly at the pore scale. The volume of fluid method is used to capture the interface motion. The volume of fluid equation and the incompressible Navier-Stokes equations are discretised by the finite volume method using a single fluid methodology, with a discontinuity in the phase properties. Capillary forces are calculated using a new semi-sharp formulation and filtered, to allow for simulations at low capillary numbers and avoid non-physical velocities. They are applied into the Navier-Stokes equations using a semi-implicit formulation, which allows larger time steps at low capillary numbers. The numerical method is verified on several test cases, demonstrating its efficiency, stability and accuracy in modelling multiphase flow through porous media with complex interface motion and irregular solid boundaries. We present two-phase flow simulations on simple pore geometries and study the mechanisms controlling two-phase flow at the pore scale. Particularly, we study the effect of geometry and flow rate on trapping and mobilization of the non-wetting-phase. We introduce a new concept to upscale the subpore-scale forces and find the relations between the flow and the pore-scale pressure drops. These information can be used as input to pore-network models. As an example, we applied this concept to predict the threshold capillary number to prevent trapping during imbibition. Furthermore, we present two-phase flow simulations on two micro-CT images of porous media and show the effect of capillary number on the flow pattern, the trapped non-wetting phase saturation and blob sizes. We present a rigorous approach to relate the pore-scale forces controlling the flow to the Darcy-scale parameters and use it to obtain relative permeability curves. Overall, this thesis provides a methodology for a detailed pore-scale analysis of multiphase flow, serving as a rigorous foundation for large-scale modelling and prediction.
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Britton, Steven Todd. "AN ANALYSIS OF INTERNAL VOIDS OF ORTHODONTIC ADHESIVES VIA MICRO-CT." Master's thesis, Temple University Libraries, 2019. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/598784.
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Oral BiologyM.S.
Objectives: While bracket debonding has been explored through shear bond-strength tests with debonding linked to the type of material used, the technique of adhesive application, and contamination, the contribution of internal voids in orthodontic adhesives is unknown. Voids may result in fracture or bond-failure, either within the adhesive or at the tooth-adhesive-bracket interfaces. The aim of this thesis is to quantify the internal volumetric voids and bonding strength of three generations of bracket adhesives. Methods: Extracted third molars were bonded with three groups of orthodontic brackets including conventionally-pasted (CP), pre-coated (PC), or pre-coated flash-free (FF) (n=5 per group). The three-dimensional internal structure of the adhesive was evaluated with Micro Computed Tomography (micro-CT) using the Skyscan micro-CT (maximum resolution of 5 microns). Data from the micro-CT were analyzed with SkyScan software to perform 3D reconstructions, image processing, and qualitative and quantitative analysis of the adhesive’s structure. The amount of void was determined by measuring the percentage of voids at the bonded interfaces (Vint) and within the adhesive (Vbulk). The total amount of void was also calculated (Vtot= Vint+ Vbulk). Differences in void between the groups were assessed using one-way ANOVA with post-hoc Tukey tests (α=0.05). The bonding strength of the three adhesives systems was evaluated via shear bond strength tests. Results: Our void quantification results showed that FF brackets had a statistically higher (p0.05) for any the analyzed locations (Vint, Vbulk). Our results indicate the majority of voids were found at bonded interfaces (Vint) compared to within the bulk (Vbulk) for all three groups, with statistically significant (p<0.05) differences for CP and FF. Our bonding strength evaluation revealed the pre-coated group (PC) to have on average the highest bond strength compared to conventionally-pasted (CP) and pre-coated flash-free (FF) groups. Conclusions: The overall amount of void in the pre-coated flash-free adhesive brackets is significantly higher compared to conventionally-pasted and pre-coated groups. The majority of the void was identified to be located at the bonded interfaces (tooth/adhesive and bracket/adhesive) rather than within the bulk of the adhesive for all groups. Our bonding strength results indicate the pre-coated brackets to have the highest bond strength compared to pre-coated flash-free and conventionally-pasted. Our preliminary set of results indicate an inverse relationship between bonding strength and amount of void of brackets adhesives, with the pre-coated exhibiting the highest bond strength and least void. However, due to a limited sample size additional data are needed to validate these conclusions and find solid relationships between adhesive voids and bonding strength.
Temple University--Theses
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Liu, Fanxiao [Verfasser], and Peter [Akademischer Betreuer] Müller. "Micro-CT and Micro-FE analysis of stress transfer of femoral stems / Fanxiao Liu ; Betreuer: Peter Müller." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2021. http://d-nb.info/1228270732/34.
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Bennett, James. "Hybrid Spectral Micro-CT: System Implementation, Exposure Reduction, K-edge Imaging Optimization, and Content Management." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/25525.
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Spectral computed tomography (CT) has proven an important development in biomedical imaging, yet there are several limitations to this nascent technology. Near-term implementation of spectral CT imaging can be enhanced using a hybrid architecture that integrates a narrow-beam spectral 'interior' imaging chain integrated with a traditional wide-beam 'global' imaging chain. The first study demonstrates the feasibility of hybrid spectral micro-CT architecture with a first-of-its-kind system implementation and preliminary results showing improved contrast resolution and spatial resolution. The second study seeks to characterize the hybrid spectral micro-CT scan protocol for reduction of radiation exposure. In the third study, the spectral 'interior' imaging chain was optimized for K-edge imaging of high-z elemental contrast agents. In the final study, an open-source, low-cost solution for managing digital content in an academic setting was demonstrated. The results of these studies confirm the merits of a hybrid architecture and warrant further consideration in future pre-clinical and clinical spectral micro-CT and CT scanner design and protocols.Ph. D.
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Michelon, Carina. "EFICÁCIA DA ATIVAÇÃO ULTRASSÔNICA PASSIVA DO SOLVENTE NA REMOÇÃO DE MATERIAL OBTURADOR DURANTE O RETRATAMENTO ENDODÔNTICO ANÁLISE POR MICROTOMOGRAFIA COMPUTADORIZADA." Universidade Federal de Santa Maria, 2013. http://repositorio.ufsm.br/handle/1/6106.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorThe removal of pre-existing root canal filling is basic requirement for endodontic retreatment in order to reveal necrotic tissue debris and bacteria which may be responsible for periapical inflammation and by the treatment failure. The aim of this study was to evaluate the efficacy of passive ultrasonic activation (PUA) with use of organic solvent as an assistant method in removal of filling material during endodontic retreatment and determine a protocol for its utilization, using high-resolution micro-Computed Tomography (micro-CT). Thirty curved mesial roots of mandibular molars with isthmus area were instrumented and filled with gutta-percha and EndoFill (Dentsply-Maillefer, Ballaigues, Switzerland) through Tagger s hybrid technique. After 30 days, the filling material was removed with the ProTaper Retreatment rotary system (Dentsply-Maillefer, Ballaigues, Switzerland) and the root canals were prepared with the F1-F4 ProTaper instruments (Dentsply-Maillefer, Ballaigues, Switzerland). The specimens will be randomized into two groups according to the final irrigation protocol. In the Manual Group, the root canals were irrigated and agitated manually with Orange Oil solvent (Citrol, Biodinâmica, Ibiporã, Brazil), 2,5% Sodium Hypochlorite (NaOCl) (Biodinâmica, Ibiporã, Brazil) and 17% Ethylenediaminetetraacetic Acid (EDTA) (Biodinâmica, Ibiporã, Brazil). In the PUA Group, the specimens were submitted to PUA with Orange Oil solvent, 2,5% NaOCl and 17% EDTA. High-resolution micro-CT scans was used to select the sample, analyze the root filling and measure the volume of the remaining root filling material after each stage of the retreatment. The volume of remaining filling material was established and transformed into percentage in relation to total volume of filling material. The dates were statistically analyzed with a significance level set at α = 0.05. The Mann Whitney test was used to compare the percentage of remaining filling material between groups, for canal thirds in each retreatment step. The Friedman test was used to verify differences among root filling material and the successive retreatment stages at each canal segment in same group. The differences amongst the coronal, middle and apical third in the each group were analyzed with Friedman test. The Dunn test was performed as the post-hoc multiple comparison method. No significant differences between groups when rotary instrumentation (Stage 1) was considered (P > 0.05). None of the irrigation protocols removed completely the remains of the root canal filling. The use of Manual e PUA protocols decreases statistically the amount of remaining filling material compared to Stage 1 (P = 0.000). In the PUA Group, the root canals showed significantly less percentage remaining filling material compared with Manual Group, for all thirds (P < 0.05). The PUA protocol left similar amount of filling material among the apical, middle and cervical thirds (P > 0.05). None of the irrigation protocols tested was able to completely remove all gutta-percha/sealer from the curved canals and with isthmus area. However, the results of this study suggest that in root canals with complex anatomy that require endodontic retreatment, the PUA with orange oil, NaOCl and EDTA can be a great aid in the removal of the remaining root filling material left after removal of the bulk of filling material.
A remoção do material obturador pré-existente é um requisito fundamental para a realização do retratamento endodôntico a fim de revelar restos de tecido necrótico e bactérias que podem ser responsáveis pela inflamação periapical e pela falha do tratamento. O objetivo deste estudo foi avaliar a eficácia da Ativação Ultrassônica Passiva (AUP) com uso de solvente orgânico, como um método auxiliar na remoção do material obturador durante o retratamento endodôntico e determinar um protocolo para sua utilização, através da Microtomografia Computadorizada (micro-CT). Trinta raízes mesiais curvas e com istmo de dentes molares inferiores foram instrumentadas e obturadas com guta percha e cimento EndoFill (Dentsply-Maillefer, Ballaigues, Suíça) através da técnica híbrida de Tagger. Após 30 dias, o material obturador foi removido com o sistema rotatório de desobturação ProTaper Retratamento (Dentsply-Maillefer, Ballaigues, Suíça) e o canal repreparado com os instrumentos F1-F4 do sistema rotatório ProTaper Universal (Dentsply-Maillefer, Ballaigues, Suíça). Os espécimes foram aleatoriamente divididos em dois grupos (n=15) de acordo com o protocolo de irrigação final. No Grupo Manual, os canais radiculares foram irrigados e agitados manualmente com solvente a base de Óleo de Laranja (Citrol, Biodinâmica, Ibiporã, Brasil), Hipoclorito de Sódio (NaOCl) 2,5% (Citrol, Biodinâmica, Ibiporã, Brasil) e Ácido Etilenodiaminotetracético (EDTA) 17% (Citrol, Biodinâmica, Ibiporã, Brasil) . No Grupo AUP, os espécimes foram submetidos à AUP com Óleo de Laranja, NaOCl 2,5% e EDTA 17%. A seleção da amostra, a análise da obturação e a mensuração do volume de material obturador remanescente após cada estágio do retratamento foram realizadas através da micro-CT. O volume de material obturador remanescente foi estabelecido e transformado em porcentagem em relação ao volume total de material obturador. Os dados foram submetidos à análise estatística com nível de significância fixado em α = 0.05. O teste de Mann Whitney foi usado para comparar a porcentagem de material obturador remanescente entre os grupos, em cada fase do retratamento. O teste de Friedman foi usado para analisar diferenças entre o volume da obturação e os estágios do retratamento dentro de um mesmo grupo. Diferenças entre os terços cervical, médio e apical dentro do mesmo grupo foram analisadas com o teste de Friedman. O teste de Dunn foi usado como post hoc para múltiplas comparações. Não houve diferença estatisticamente significante entre os grupos quando a instrumentação rotatória (Estágio 1) foi considerada (P > 0.05). Nenhum dos protocolos de irrigação removeu completamente os remanescentes de material obturador em todos os espécimes. Tanto o protocolo da AUP quanto o Manual diminuíram a quantidade de remanescente de guta percha e cimento em relação ao Estágio 1 (P = 0.001). No grupo AUP, os canais radiculares mostraram significantemente menos porcentagem de remanescentes de material obturador que o grupo Manual, para todos os terços (P < 0.05). O protocolo da AUP deixou quantidade similar de material remanescente em todos os terços do canal radicular (P > 0.05). Nenhum dos protocolos de irrigação testados foi capaz de remover completamente a guta percha/cimento de canais radiculares curvos e com área de istmo. Contudo, os resultados obtidos neste estudo sugerem que em canais radiculares com anatomia complexa que necessitam de retratamento endodôntico, a AUP com óleo de laranja, NaOCl e EDTA pode ser um grande auxiliar na remoção dos remanescentes de material obturador deixados após a desobturação do canal radicular.
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Pichotka, Martin Peter [Verfasser], and Caroline [Akademischer Betreuer] Röhr. "Iterative CBCT reconstruction-algorithms for a spectroscopic Medipix-Micro-CT = Iterative CBCT Rekonstruktions-Algorithmen für ein spektroskopisches Medipix-Mikro-CT." Freiburg : Universität, 2014. http://d-nb.info/1115495674/34.
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Stjärnesund, Johan. "A micro-CT investigation of density changes in pressboard due to compression." Thesis, Uppsala universitet, Tillämpad mekanik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-350876.
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Pressboard, a high-density cellulose-based product, is used both as load bearing structures and dielectric insulation in oil-filled power transformers. During transformer operation, mechanical forces and vibrations are applied on the material. In particular, this investigation focuses on pressboard sheets placed between the turns of transformer windings, called the spacers, which during short circuit are subjected to high compressive forces of impulse nature. As a result of these forces, remaining deformations are created in the components. One step to reduce the negative consequences that come from the deformations is to understand how the fiber structure of the material changes by these forces, thus finding the week link. Understanding these changes could lead to future modification of the material to better withstand short circuits. To see the fiber structure and its changes in the material, pressboard has been investigated with a micro-CT at the Division of Applied Mechanics at Uppsala University. The scanned images have been reconstructed and analyzed in NRecon, CTAnalyser, and Matlab to investigate the density distribution changes and to identify the densification patterns. The study shows that pressboard initially has an inhomogeneous density distribution through the thickness and after mechanical indentations, the densification tends to begin in the more porous parts of the material. The project also included a prediction of the densification pattern, performed by finite element analysis (FEA) using a simplified material model. The results show that a material model with varying Young’s modulus through the thickness, based on a stiffness and porosity relationship, can produce similar densification patterns as in the experiments.
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Kabini, S. N. "An in-vitro comparative micro-computed tomographic evaluation of three obturation systems." University of the Western Cape, 2017. http://hdl.handle.net/11394/6312.
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Magister Chirurgiae Dentium - MChD (Prosthodontics)Gaps or voids between walls of root canal and obturation material may lead to re-infection of the obturated root canal. Therefore, adaptation of the obturation material to dentine walls is essential for the success of root canal treatment.
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Sório, Ana Luisa Riul. "Avaliação histológica e microtomográfica do efeito de células osteoblásticas originárias da medula óssea em defeitos ósseos na calvária de ratos submetidos a um modelo experimental de osteorradionecrose." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/58/58138/tde-30082017-090138/.
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A osteorradionecrose é uma séria e debilitante consequência da radioterapia da cabeça e pescoço, definida como uma área óssea que não sofre reparação após a irradiação. O objetivo deste trabalho foi analisar o efeito in vivo da presença de células mesenquimais da medula óssea carreadas em gel em defeitos provocados na calvária de ratos submetidos a um modelo experimental de osteorradionecrose. Foi realizada a obtenção de células osteoblásticas da medula óssea de ratos cultivadas in vitro e devidamente caracterizadas quanto ao seu fenótipo por meio de ensaios bioquímicos como proliferação celular, atividade de fosfatase alcalina e sua detecção in situ, além da detecção e quantificação de nódulos mineralizados. Posteriormente, ratos wistar foram submetidos ao protocolo de osteorradionecrose (irradiação com 20 Gy em dose única) e pareados com controles para em seguida serem realizados defeitos nas calvárias para inserção de células osteoblásticas da medula óssea previamente cultivadas in vitro juntamente com gel carreador e realizada a sutura. Os animais foram divididos em 4 grupos: controle (C), controle + células osteoblásticas (CC); osteorradionecrose (IR) osteorradionecrose + células osteoblásticas (IRc). Ao final de 4 semanas os animais foram sacrificados e realizados os seguintes ensaios: (1) análise histológica com base em cortes histológicos descalcificados (2) análise tomográfica por meio de micro-CT dos defeitos previamente criados. Os dados obtidos foram submetidos ao teste de normalidade e posteriormente à análise estatística para p<0,05. As células mesenquimais derivadas da medula óssea apresentaram fenótipo característico de células osteoblásticas após serem cultivadas em meio osteogênico, com aumento da proliferação, atividade de fosfatase alcalina e formação de nódulos mineralizados quando comparado com as células cultivadas em meio basal. A análise qualitativa dos cortes histológicos corados em hematoxilina-eosina e tricrômico de Masson demonstrou maior neoformação óssea no grupo IRc quando comparado ao grupo IR e similar ao grupos controles. A análise tomográfica revelou um aumento na espessura trabecular, densidade de conectividade, número trabecular e superfície óssea no grupo IRc em relação ao grupo IR. Os resultados sugerem que a inserção de células mesenquimais diferenciadas em osteoblastos favorece a neoformação de defeitos ósseos na presença de osteorradionecrose.Osteoradionecrosis is a serious and debilitating consequence of head and neck radiotherapy, defined as a bone area that does not repair after irradiation. The purpose of this investigation was to analyze in vivo the presence of mesenchymal cells from bone marrow in calvariae defects of rats submitted to osteoradionecrosis. Cells were collected from rat femur bone marrow to perform characterization of osteoblastic phenotype by means of biochemical assays such as cell proliferation, alkaline phosphatase activity and its in situ detection and mineralization. Afterwards, male wistar rats were submitted to osteoradionecrosis protocol (20 Gy in a single dose) and paired with control animals. After 30 days, there were performed calvariae defects and placement of osteoblastic cells previously cultured with a gel vehicle inside the defects, which were sutured properly. The animals were divided in 4 groups: control (C), control + osteoblastic cells (CC), osteoradionecrosis (IR) osteoradionecrosis + osteoblastic cells (Irc). After 30 days, the animals were euthanized to perform the following analysis: (1) Histological evaluation by means of decalcified slide sections stained with hematoxilin-eosin and Masson trichrome; (2) Tomographic evaluation by means of adequate parameters. Data obtained were submitted to normality test and statistical analysis for p<0,05. The mesenchymal cells from bone marrow presented osteoblastic phenotype after being cultured in osteogenic medium, with higher ALP detection and activity, as well as an increase of mineralized nodules when compared to cells cultured in basal medium. Histological analysis showed that irradiation impaired bone neoformation and affected bone marrow composition, as well as the presence of osteoblasts and osteocytes. On the other hand, cell therapy in group IRc improved bone neoformation when compared to group IR, showing similarity to control groups. Tomographic analysis revealed an increase in trabecular thickness, density of connectivity, trabecular number and bone surface when compared to group IR. The results suggest that the placement of mesenchymal cells differentiated in osteoblasts may improve bone neoformation of defects created after the onset of osteoradionecrosis.
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Al, Jamaan Tamer Saleh. "Diagnostic accuracy and reproducibility of conventional and novel caries detection methods as determined by histology and micro-CT : a study in vitro." Thesis, University of Dundee, 2016. https://discovery.dundee.ac.uk/en/studentTheses/8aee92e0-8af5-4815-b67b-96de1088e07d.
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Taylor, Howard. "Assessing the potential for suffusion in sands using X-ray micro-CT images." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/56070.
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Internal erosion is a major safety concern for embankment dams and flood embankments and is the focus of much research internationally. Suffusion is a mechanism of internal erosion which affects gap-graded or broadly graded cohesionless soils and is characterised by selective removal of fine material, leaving behind a coarse material with increased hydraulic conductivity. Early studies on suffusion proposed design criteria based on laboratory testing, and presented conceptual models to explain the results in terms of grain-scale behaviour. The study by Kenney & Lau (1985) identified three criteria for suffusion: 1 – Fine particles must be free to move (mechanical criterion); 2 – Fine particles must be small enough to fit through the void space between coarse particles (geometric criterion); 3 – Fluid flowing through the void space must have sufficient velocity to transport the fine particles (hydraulic criterion). Recent studies have examined the first two criteria using grain-scale models with idealised particles, including analytical models and discrete element models (DEM) with circular or spherical particles. This thesis presents a new methodology, using non-destructive 3D imaging (micro-CT) to characterise the internal microstructure in physical specimens of sands and glass beads. This methodology involved the development of innovative image processing and numerical techniques to quantify unstable particle assemblies and to measure particle size distributions and void constriction size distributions. The new method was validated and was shown to produce good agreement with existing methods for idealised particle configurations, however the results for real sand specimens provided new insights into the effects of particle shape, particle size distribution and density on void constriction sizes. Furthermore, the 3D images of real specimens have provided new insights into the appropriateness of existing conceptual models for gap-graded particle structures. These results were used to critically examine and evaluate existing mechanical and geometric criteria for suffusion. The 3D images showed, qualitatively, that the void structures in sands varied significantly from those in porous rocks – which had been the basis for the majority of existing grain-scale fluid flow models. To examine this issue quantitatively, computational fluid dynamics (CFD) simulations were performed within the 3D images of sands and glass beads, in parallel to laboratory permeameter tests on the same materials. The results presented in this thesis provided entirely new insights into the patterns of fluid flow in sands, they allowed correlations to be made between fluid flow and void constriction sizes and also showed how local velocities varied from volume-average discharge and seepage velocities. This study provides new information to support, clarify and improve upon the current understanding of suffusion, filtration and seepage flows in sands. The detailed methodology and results also highlight issues of great importance to future micro-scale modelling of these phenomena.
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Kim, Paul [Verfasser]. "In-vitro-Untersuchung des Pulpenraums mandibulärer primärer Prämolaren im Micro-CT / Paul Kim." Mainz : Universitätsbibliothek der Johannes Gutenberg-Universität Mainz, 2020. http://d-nb.info/1224810201/34.
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McMurray, Alexis Kelly. "Micro-CT/PET Assessment of Lung Metastasis in a Mouse Model of Osteosarcoma." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1364308724.
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Starnoni, Michele. "Modelling single and two-phase flow on micro-CT images of rock samples." Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=232293.
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In this Thesis, numerical simulations of single and two-phase pore-scale flow on three dimensional images obtained from micro-CT scanning of different reservoir rocks are presented. For single-phase flow, the petrophysical properties of rocks, namely Representative Elementary Volume (REV), mean pore and grain size, and absolute permeability, are calculated using an integrated approach comprising image processing, statistical correlation and numerical simulations. Two rock formations, one carbonate and one sandstone, are used throughout this Thesis. It is shown that REV and mean pore and grain size are effectively estimated using the two-point spatial correlation function. A comparison of different absolute permeability estimates is also presented, showing a good agreement between the numerical value and the experimentally determined one for the carbonate sample, but a huge discrepancy for the sandstone. For two-phase flow, the Volume-of-fluid method is used to track the interfaces. The surface tension forces are modelled using a filtered sharp formulation, and the Stokes equations are solved using the PISO algorithm. A study on the snap-off mechanism, investigating the role of several parameters including contact angle and viscosity ratio, is presented. Results show that the threshold contact angle for snap-off increases from a value of 28◦ for a circular cross-section to 30-34◦ for a square cross-section and up to 40◦ for a triangular one. For a throat of square cross-section, increasing the viscosity of the injected phase results in a drop in the threshold contact angle from a value of 30◦ when µ = 1 to 26◦ when µ = 10 and down to 24◦ when µ = 20, where µ is the viscosity ratio. Finally, a rigorous spatial averaging procedure is presented, leading to a novel definition of the macroscopic capillary pressure. Simulations results of drainage on the scanned images of the rock samples are used to compare different estimates of the macroscopic capillary pressure. The comparison reveals that, contrary to what is commonly done following the traditional approach, use of surface average for the pressures is more appropriate than that of volume average, when averaging the microscopic balance equations relevant for pore-scale two-phase flows in porous media.
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Hopper, Timothy Andrew John. "Quantitative MRI and Micro-CT of bone architecture : applications and limitations in orthopaedics." Thesis, Queensland University of Technology, 2005. https://eprints.qut.edu.au/16149/1/Timothy_Hopper_Thesis.pdf.
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The aim of this thesis was to investigate some methods for quantitative analysis of bone structure, particularly techniques which might ultimately be applied post-operatively following orthopaedic reconstruction operations.
Initially it was decided to explore the efficacy of MRI in quantifying the bone structure at high resolution by comparing high resolution MRI against 'gold standards' such as Scanning Electron Microscopy (SEM) and optical histology. This basic study provided a measure of the distortions in the morphological bone parameters derived from MR images due to susceptibility artefacts and partial volume effects. The study of bone architecture was then extended to a model of advanced renal osteodystrophy in a growing rat. For this study, high-resolution micro computed tomography (microCT) was used and as a result of the high resolution images obtained, three new bone morphological parameters were introduced to characterise the bone structure.
The desire to study bone architecture post-operatively in hip replacements led to a preliminary study on ex-vivo sheep acetabulae following total hip replacement, to determine the extent that the bone architecture could be investigated around the acetabulum. The motivation for studying the acetabulum was based on the high occurrence of debonding at the bone / prosthesis interface. This study demonstrated the superior nature of 3D MRI over conventional x-ray radiographs in early quantitation of fibrous membranes located between the host bone and the non-metallic implant and/or the bone cement. The presence of such fibrous membranes is strongly indicative of failure of the prosthesis.
When using clinical MRI to image post-operative hip replacement, the image quality is severely affected by the presence of the metallic implant. The head of the prosthesis is shaped like a metal sphere and is located in the acetabular cup. This problem was investigated by performing simulations of MR images in the presence of the field perturbation induced by the presence of a metal sphere, with the effects of slice excitation and frequency encoding incorporated into the simulations. The simulations were compared with experimental data obtained by imaging a phantom comprising a stainless steel ball bearing immersed in agarose gel. The simulations were used to predict the effects of changing imaging parameters that influence artefact size and also to show how current metal artefact reduction techniques such as view angle tilting (VAT) work and to identify their limitations. It was shown that 2D SE and VAT imaging techniques should not be used when metallic prosthesis are present due to extreme slice distortion, whereas 3D MRI provided a method that has no slice distortion, although the effects of using a frequency encoding gradient still remain.
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Hopper, Timothy Andrew John. "Quantitative MRI and Micro-CT of Bone Architecture: Applications and Limitations in Orthopaedics." Queensland University of Technology, 2005. http://eprints.qut.edu.au/16149/.
Full textAbstract:
The aim of this thesis was to investigate some methods for quantitative analysis of bone structure, particularly techniques which might ultimately be applied post-operatively following orthopaedic reconstruction operations. Initially it was decided to explore the efficacy of MRI in quantifying the bone structure at high resolution by comparing high resolution MRI against 'gold standards' such as Scanning Electron Microscopy (SEM) and optical histology. This basic study provided a measure of the distortions in the morphological bone parameters derived from MR images due to susceptibility artefacts and partial volume effects. The study of bone architecture was then extended to a model of advanced renal osteodystrophy in a growing rat. For this study, high-resolution micro computed tomography (microCT) was used and as a result of the high resolution images obtained, three new bone morphological parameters were introduced to characterise the bone structure. The desire to study bone architecture post-operatively in hip replacements led to a preliminary study on ex-vivo sheep acetabulae following total hip replacement, to determine the extent that the bone architecture could be investigated around the acetabulum. The motivation for studying the acetabulum was based on the high occurrence of debonding at the bone / prosthesis interface. This study demonstrated the superior nature of 3D MRI over conventional x-ray radiographs in early quantitation of fibrous membranes located between the host bone and the non-metallic implant and/or the bone cement. The presence of such fibrous membranes is strongly indicative of failure of the prosthesis. When using clinical MRI to image post-operative hip replacement, the image quality is severely affected by the presence of the metallic implant. The head of the prosthesis is shaped like a metal sphere and is located in the acetabular cup. This problem was investigated by performing simulations of MR images in the presence of the field perturbation induced by the presence of a metal sphere, with the effects of slice excitation and frequency encoding incorporated into the simulations. The simulations were compared with experimental data obtained by imaging a phantom comprising a stainless steel ball bearing immersed in agarose gel. The simulations were used to predict the effects of changing imaging parameters that influence artefact size and also to show how current metal artefact reduction techniques such as view angle tilting (VAT) work and to identify their limitations. It was shown that 2D SE and VAT imaging techniques should not be used when metallic prosthesis are present due to extreme slice distortion, whereas 3D MRI provided a method that has no slice distortion, although the effects of using a frequency encoding gradient still remain.
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Inness, Philip Ralph Patton. "Assessment of different contrast preparations for micro-computed tomographic microangiographic assessment of canine cadaveric hindlimbs." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/27503.
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Reliable microvascular identification and quantitative vascular assessment via Micro-CT collection of intraosseous measurements has not been reported in dogs. The aim of this study was to identify the ideal preparation (Criteria: perfusability, radiodensity and homogeneity) for quantitative assessment of canine intraosseous microvasculature.
Materials/Methods:
Cadaveric specimens were perfused initially with resin preparations [Resin Study: Barium+Resin (BS+R), Barium, Acetone+Resin (BSA+R), Barium Slurry+Resin (BSS+R), and Barium Slurry, Acetone+Resin (BSSA+R)]. BSS+R was then compared with Barium+Saline (BSS) and Barium+Gelatine (BSG) [Comparative Study] using micro-CT via mean radiodensity and Coefficient of Variation (n=20) [vessels >1mm2, 0.3mm2-1mm2 and <0.2mm2] and intraosseous vessel diameter (<200µm) and distribution within the femur, tibia and patella (n=12).
Results:
Resin Study: BSS+R identified a greater proportion and number of small intraosseous vessels <100µm with a similar mean radiodensity and homogeneity across all vessel sizes. All test preparations were superior to the control (BS+R). The addition of saline, acetone or both improved vessel perfusion. The homogeneity of all preparations was poor with significant variation.
Comparative Study: BSS and BSG exhibited larger mean radiodensity compared with BSS+R (P<0.001) at all vessel sizes. BSG produced the most homogenous preparation. All preparations identified vessels to two scan voxels in diameter. BSS exhibiting the smallest mean vessel diameter, greatest proportion (P<0.001) and number of different vessel diameters <100µm.
Conclusions:
BSS is the most appropriate suspension for analysis of canine intraosseous microvasculature resulting in a significantly more accurate and detailed quantitative microvascular analysis. Resin preparations performed poorly within all characteristics and were inferior to both BSS and BSG. No resin preparation produced a homogeneous suspension in any vessel size.
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Pan, Lei. "The earliest members of the genus Homo in South Africa : evidence from inner structure of lower postcanine dentition." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30087/document.
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Cette thèse se compose de deux projets individuels et six chapitres, qui sont basées sur l'examen de la structure interne dentaire inférieure dentition postcanine dans un certain nombre de fossiles et modernes spécimens, à travers lesquels une étude approfondie a été effectuée à l'aide de micro-tomodensitométrie et ordinateur-outils de paleonanthropology assistée. Nous avons d'abord recensé et évalué la valeur taxinomique de l'épaisseur de l'émail et des modèles de distribution de l'épaisseur de l'émail 3D entier couronne dans un certain nombre des premiers membres du genre Homo en Afrique du Sud, et examiné dans le relavence taxonomique de EDJ morphologie long postcanine dentition, et discuté de la facteurs d'adaptation possibles / développement qui tiennent compte de la variation de la morphologie EDJ nous avons observé ici. Les trois premiers chapitres (Introduction, Matériel et méthodes) donnent un aperçu des objectifs de cette thèse, et d'examiner les études précédentes. En outre, ils fournissent une introduction détaillée des matières fossiles, les sites et un arrière-plan de la méthode assistée par ordinateur (micro-XCT) pour analyser la structure interne dentaire. Le chapitre des résultats comprend deux documents de recherche indépendants, dans les différentes étapes de soumission et de publication. Les résultats et les chapitres de discussion offrent un résumé détaillé de l'épaisseur de l'émail, EDJ morphométrie géométrique et 3D-EDJ variation métamérique entre les espèces, et de comparer les résultats avec un certain nombre d'études morphologiques et de développement, et de fournir une perspective d'étude future. Le dernier chapitre atteint des points décisifs de cette thèse, il met en évidence la valeur taxinomique des prémolaires EDJ, et met l'accent sur les caractéristiques de la mosaïque de la dentition des premiers membres du genre Homo sud-africaineThis thesis consists of two individual projects and six chapters, which are based on the examination of dental inner structure of lower postcanine dentition in a number of fossil and modern specimens, through which a comprehensive study has been done using micro-computed tomography and computer-assisted paleonanthropology tools. We first documented and assessed the taxonomical value of enamel thickness and 3D whole-crown enamel thickness distribution patterns in a number of earliest members of the genus Homo in South Africa, and looked into the taxonomic relavence of EDJ morphology along postcanine dentition, and discussed the possible adaptive/developmental factors that account for the variation of EDJ morphology we observed here. The first three chapters (Introduction, Materials and Methods) provide an overview of the objectives of this thesis, and review previous studies. Also, they provide a detailed introduction of fossil materials, sites and a background of computer-aided method (micro-XCT) to analyze the dental inner structure. The Results chapter comprises of two independent research papers, in different stages of submission and publication. The Results and Discussion chapters offer an extensive summary of enamel thickness, EDJ geometric morphometrics and 3D-EDJ metameric variation between species, and compare the results with a number of morphological and developmental studies, and provide an outlook of future study. The last chapter reaches the conclusive points of this thesis, it highlights the taxonomical value of premolar EDJ, and emphasizes the mosaic features of the dentition of South African early Homo
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Cheng, Linda Lam. "Repair of root resorption four and eight weeks following the application of continuous light and heavy forces for four weeks: micro-ct and histology studies." Thesis, Faculty of Dentistry, 2007. http://hdl.handle.net/2123/4308.
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Ballard, Darin J. "Properties of root cementum: part 11 continuous versus intermittent controlled orthodontic forces on root resorption. a micro-ct study." Thesis, Faculty of Dentistry, 2006. http://hdl.handle.net/2123/4307.
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May, Catherine M. "Craniofacial Bone Density is Regulated by Thyroid Hormone in Zebrafish:." Thesis, Boston College, 2019. http://hdl.handle.net/2345/bc-ir:108815.
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Thesis advisor: Sarah McMenaminThyroid hormone (TH) facilitates developmental transitions, particularly by modulating cell proliferation and differentiation. Its role in regulating skeletal growth is well documented. Previous work from our lab and others have demonstrated that hypo- and hyperthyroid fish display changes in bone shape, ossification and the timing of ossification5. Zebrafish (Danio rerio) develop bone quickly, grow indefinitely throughout their lives, are highly amenable for imaging, and are a valuable model for skeletal biology research. Using Danio rerio, we sought to study the long-term effects of TH on bone density by rearing and comparing normal euthyroid (Eu) with a transgenically thyroid-ablated hypothyroid (TH-) and mutant hyperthyroid (TH+) fish. We found that TH strongly affects bone density and volume. We further hypothesize that TH is critical for the timing and fidelity of skeletogenesis. In hormone-dysregulated fish, we found that massive bone and cartilage exostoses grow on the dentary. Thyroid hormone’s effects are highly bone-specific: in TH- fish, we see reduced density in many craniofacial bones, but also increased volume and mineralization in other regions of the dentary. These data suggest that TH plays a critical role in coordinating bone mineralization with growth
Thesis (MS) — Boston College, 2019
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Biology
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He, Bihui. "Functional role of CKIP-1 for bone formation reduction during aging: micro CT analysis." HKBU Institutional Repository, 2015. https://repository.hkbu.edu.hk/etd_oa/141.
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Background: Bone metabolism is a dynamic balance, consisting two major courses: bone resorption and bone formation. Bone loss during aging is an age-associated process. There are several aspects changing with age in bone, including bone mechanical behavior, bone mineral matrix, bone proteins, genetic and molecular signaling in bone cells physiology. Based on the above factors, when the formation decreases, it leads to a disorder disease: osteoporosis, characterized by low bone mineral density and degenerating microstructure, resulting in increased risks of bone fractures. Many previous studies aim on how to reduce bone resorption, but there is a study shows that Smurfl has an important role in inhibiting osteoblast activity but not influencing osteoclast activity. And Ckip-1 (casein kinase-2 interacting protein-I) can reinforce the process. This thesis focuses on CKIP-1 functional role in regulating bone formation and the results are discussed on the basic of micro CT data analysis. Aim: Evaluate the functional role of CKIP-1 in regulating bone formation through BMP signaling pathway in established osteoporosis rats model on bone hismorphometric parameters. Methods: The bodies of tibia and femur were obtained from thirty-six six-month-old female rats which had been divided into either CKIP-1 knockout(KO;n=18)group or CKIP-1 wild type(WT;n=18)group. According to rats age, a timeline was divided into three parts:4 months,6 months and 8 months. Every time point included two groups(K0=6; WT=6). Ten days and three days before sacrificed, Calcein green(l Omg/kg)and xylenol orange(30mg/kg)would be injected intraperitoneally in all the rats to symbol the surface of bone formation. After sacrifice, the tibia and femur bodies would be scanned and reconstructed as 3D images by micro CT. Results: Figure decrease in micro CT parameters during aging is attenuated in KO group. Conclusion: The negatively functional role of CKIP-1 in monitoring bone formation in aging bone can be a good way and high specificity regulate bone formation. Keywords: CKIP-l(Casein kinase-2 interacting protein-l);KO groups(knockout);WT groups(wild type);Micro CT.
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Epshteyn, Leonid. "OPTIMAL SPECIFICATIONS FOR MEASURING BONE-TO-IMPLANT CONTACT OF MINI-SCREWS USING MICRO-CT." Master's thesis, Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/395373.
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Oral BiologyM.S.
The use of mini-screws (MSs) as temporary anchorage devices (TADs) is becoming more common in orthodontic treatment. With the increased use of TADs and the numerous manufactures producing them, research is needed to aid orthodontists in their selection of MSs. One of the major advantages of using mini-screw implants is that they can be loaded immediately and do not require osseoitegration.1 For this to be successful, the mini-screw needs to have adequate primary stability to retain itself in the bone. The mini-screw bone system relies on the stability of the mini-screw, the stability of the bone, and the stability of their interface.19,20 In the literature, this stability if usually quantified by measuring the pullout force, insertion torque and bone-to-implant contact.25,26 To date, much of the research has demonstrated that the geometric configuration of the mini-screw plays a significant role in its primary stability. Features such as pitch (length between threads), thread body design, screw length and diameter factor into primary stability.5,21,23 In order to observe the bone-to-implant contact traditionally, researchers had to perform histologic section. This method is destructive to the sample and does not allow it to be used for other analyses such as pullout force. With micro-CT technology, it is now possible to study the bone-to-implant relationship without destroying the sample and with great accuracy.6 Currently, it is unclear as to the optimal scanning specification to choose when using a micro-CT to measure bone-to-implant contact. The optimal scan is one, which provides the most accurate measurement within the least amount of time. The highest quality scans increase both time and costs of acquisition, while lower quality scans have the potential of introducing inaccuracies. This study aims to determine the optimal specifications needed to scan a mini-screw in bone using a SkyScan 1172 micro-CT, to measure the bone-to-implant contact. A total of three orthodontic mini-screws from Aarhus (American Orthodontics, Sheboygan, Wisc), 1.4 mm in diameter and 8 mm long were inserted into an adult pig mandible. All three mini-screws were inserted into the lingual area in the molar region. Each mini-screw was inserted until all the threads were buried into the bone. After placement, the blocks of bone containing the individual mini-screw were cut out and shaped to facilitate scanning by micro-CT. Each sample was be positioned and scanned individually using micro-CT (SkyScan 1172; SkyScan, Aartselaar, Belgium) under 5 different specifications, see table 1. SkyScan software was used to process the scans and calculate qualitative and quantitative data. For each sample bone-to-implant contact was measured. The software measured the TS, which is the area of the mini-screws surface and the IS, which is where the bone interfaces with the mini-screws. The IS/TSx100 was determined to be the percentage of the mini-screws surface that is in contact with bone or the bone-to-implant contact. Qualitative and quantitative analyses were performed to determine statically significant differences between the various bone-to-implant contact measurements of the samples. BIC varied greatly between the scanning specifications and samples, from 0% to 70.35%. Quantitative and qualitative analysis was performed to compare the differences in BIC(%) values between the 5 specifications. Two of the three samples displayed an accuracy of greater than 95% for specification 3, thus providing latitude in adjustment/reduction of scanning times with minimal variance in data accuracy for BIC(%). The results show for measuring BIC(%), scanning specifications can be modified/optimized to reduce scanning time while maintaining acceptable accuracy when scanning of large sample sizes are needed. It is recommended that for studies where absolute BIC(%) is needed, specification 5 is recommended since it will provide the most accurate measurement. For studies that are comparing changes in BIC(%), specification 3 is recommended as it will provide an acceptable level of accuracy in a reasonable amount time. However, due to limited sample size, more data is needed.
Temple University--Theses
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Mohapatra, Sucheta. "Development and quantitative assessment of a beam hardening correction model for preclinical micro-CT." Thesis, University of Iowa, 2012. https://ir.uiowa.edu/etd/3500.
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The phenomenon of x-ray beam hardening (BH) has significant impact on preclinical micro-CT imaging systems. The causal factors are the polyenergetic nature of x-ray beam used for imaging and the energy dependence of linear attenuation coefficient of the imaged material. With increase in length of propagation of beam in the imaged object, lower energy photons in the projected beam become preferentially absorbed. The beam "hardens" (as average energy increases) and progressively becomes more penetrating, causing underestimation of the attenuation coefficient. When this phenomenon is not accounted for during CT reconstruction, it results in images with nonuniform CT number values across regions of uniform density. It leads to severe errors in quantitative applications of micro-CT and degradation in diagnostic quality of images. Hence, correction for beam hardening effect is of foremost importance and has been an active area of research since the advent of micro -CT.
The Siemens Inveon micro-CT system uses a common linearization approach for BH correction. It provides a set of standard default coefficients to be applied during CT reconstruction. However, our initial experiments with uniform water phantoms of varying diameters indicated that the correction coefficients provided by default in the Inveon system are applicable for imaging mouse-size (~28 mm) objects only. For larger objects the correction factors yielded incorrect CT values along with characteristic 'cupping' observed in the uniform region in the center of the phantom. This study provides an insight into the nature and characteristics of beam hardening on the Inveon CT system using water phantoms of varying sizes. We develop and test a beam hardening correction scheme based on linearization using cylindrical water phantoms of two different diameters - 28 mm and 71 mm, selected to represent mouse and rat sizes respectively. The measured non-linear relationship between attenuation and length of propagation is fitted to a polynomial function, which is used to estimate the effective monoenergetic attenuation coefficient for water. The estimated effective linear attenuation coefficient value is used to generate the expected sum of attenuation coefficients along each x-ray path through the imaged object. The acquired poly-energetic data is then linearized to expected projections using a third order polynomial fit, which is consistent with the Inveon BH model and software. The coefficients of this trinomial are then applied for BH correction during CT reconstruction.
Correction achieved with the proposed model demonstrates effective removal of the characteristic cupping artifact that was observed when default BHC coefficients were applied. In addition to water phantoms, we also test the effectiveness of the proposed scheme using solid cylindrical phantoms of three different densities and composition. The proposed method was also used to measure the BH effect for 12 different kVp/filtration combinations. By generating twelve distinct sets of BHC coefficients, for each setting, we achieve a significant expansion in the quantitative performance of the Inveon CT system.
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Iori, Gianluca. "Micro-FEM models based on micro-CT reconstructions for the in vitro characterization of the elastic properties of trabecular bone tissue." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5422/.
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This master’s thesis describes the research done at the Medical Technology Laboratory (LTM) of the Rizzoli Orthopedic Institute (IOR, Bologna, Italy), which focused on the characterization of the elastic properties of the trabecular bone tissue, starting from october 2012 to present.
The approach uses computed microtomography to characterize the architecture of trabecular bone specimens. With the information obtained from the scanner, specimen-specific models of trabecular bone are generated for the solution
with the Finite Element Method (FEM). Along with the FEM modelling, mechanical tests are performed over the same reconstructed bone portions. From the linear-elastic stage of mechanical tests presented by experimental results, it
is possible to estimate the mechanical properties of the trabecular bone tissue.
After a brief introduction on the biomechanics of the trabecular bone (chapter 1) and on the characterization of the mechanics of its tissue using FEM models (chapter 2), the reliability analysis of an experimental procedure is explained (chapter 3), based on the high-scalable numerical solver ParFE. In chapter 4, the sensitivity analyses on two different parameters for micro-FEM model’s reconstruction are presented.
Once the reliability of the modeling strategy has been shown, a recent layout for experimental test, developed in LTM, is presented (chapter 5). Moreover, the results of the application of the new layout are discussed, with a stress on the difficulties connected to it and observed during the tests. Finally, a prototype experimental layout for the measure of deformations in trabecular bone specimens is presented (chapter 6). This procedure is based on the Digital Image Correlation method and is currently under development in LTM.
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Klinge, Christine [Verfasser]. "Quantitative Strukturanalyse der Mäuselunge mit stereologischen Methoden: Korrelation von Micro-CT und Histologie / Christine Klinge." Hannover : Bibliothek der Tierärztlichen Hochschule Hannover, 2013. http://d-nb.info/1037834569/34.
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Terrin, Massimo. "Micro-CT for small animal imaging : Optimization of the tube voltage for low-contrast imaging." Thesis, KTH, Skolan för teknik och hälsa (STH), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176482.
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This master thesis evaluated the optimal tube voltage for low-contrast imaging of a micro-CT system (intended for small animal imaging) built at the School of Technology and Health (STH) of the Royal Institute of Technology (KTH). The main goal of this work was to calibrate the above-mentioned device (composed moreover by a Hamamatsu microfocus L10951-01 X-ray tube, a CMOS flat panel Hamamatsu C7942CA-22 and using a Cone-Beam CT reconstruction algorithm) for obtaining the best imaging of low-contrast structures. In order to do this, an analytical model, re-adapted from the previous state-of-the-art Micro-CT studies, was evaluated for finding a sub-optimal tube voltage from which to start the experiments, done on a reference Low-Contrast phantom specifically intended for the calibration of Micro-CT devices. Finally, by looking to the results from the experiments, a good tube setting for the optimization of the CT for low-contrast imaging was found. The optimal tube voltage for low-contrast imaging, from the experiments on the QRM phantom, was found to be between 48 and 50 kV. This tube voltage values gave the best CNR and contrast profiles results. Ultimately, we found that the usage of a 1mm Al filtration reduced the absorbed dose without affecting the image quality.
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Möllmann, Henriette Louise [Verfasser]. "Evaluation der Knochenarchitektur im diät-induzierten Osteoporosemodell der Ratte mittels Micro-CT / Henriette Louise Möllmann." Gießen : Universitätsbibliothek, 2016. http://d-nb.info/1092995846/34.
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Andersson, Sebastian. "Implementation of a reconstruction software and image quality assessment tool for a micro-CT system." Thesis, KTH, Fysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-183147.
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Yeslam, Hanin E. "The effect of acid etching on remineralization of incipient caries lesions : a micro-ct study /." Connect to resource online, 2009. http://hdl.handle.net/1805/2084.
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Thesis (M.S.D.)--Indiana University School of Dentistry, 2009.Title from PDF t. p. (viewed Feb. 10, 2010) Advisor(s): Masatoshi Ando, Chair of the Research Committee, Carlos Gonzalez-Cabezas, Melvin Lund, Tien-Min Gabriel Chu, Michael Cochran. Curriculum vitae. Includes abstract. Includes bibliographical references (leaves 64-70).
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Bianculli, Antonella. "Analysis of the scale effect in different computed tomography systems on the evaluation of bone tissue parameters." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11207/.
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Tra le patologie ossee attualmente riconosciute, l’osteoporosi ricopre il ruolo di protagonista data le sua diffusione globale e la multifattorialità delle cause che ne provocano la comparsa. Essa è caratterizzata da una diminuzione quantitativa della massa ossea e da alterazioni qualitative della micro-architettura del tessuto osseo con conseguente aumento della fragilità di quest’ultimo e relativo rischio di frattura. In campo medico-scientifico l’imaging con raggi X, in particolare quello tomografico, da decenni offre un ottimo supporto per la caratterizzazione ossea; nello specifico la microtomografia, definita attualmente come “gold-standard” data la sua elevata risoluzione spaziale, fornisce preziose indicazioni sulla struttura trabecolare e corticale del tessuto. Tuttavia la micro-CT è applicabile solo in-vitro, per cui l’obiettivo di questo lavoro di tesi è quello di verificare se e in che modo una diversa metodica di imaging, quale la cone-beam CT (applicabile invece in-vivo), possa fornire analoghi risultati, pur essendo caratterizzata da risoluzioni spaziali più basse. L’elaborazione delle immagini tomografiche, finalizzata all’analisi dei più importanti parametri morfostrutturali del tessuto osseo, prevede la segmentazione delle stesse con la definizione di una soglia ad hoc.
I risultati ottenuti nel corso della tesi, svolta presso il Laboratorio di Tecnologia Medica dell’Istituto Ortopedico Rizzoli di Bologna, mostrano una buona correlazione tra le due metodiche quando si analizzano campioni definiti “ideali”, poiché caratterizzati da piccole porzioni di tessuto osseo di un solo tipo (trabecolare o corticale), incluso in PMMA, e si utilizza una soglia fissa per la segmentazione delle immagini. Diversamente, in casi “reali” (vertebre umane scansionate in aria) la stessa correlazione non è definita e in particolare è da escludere l’utilizzo di una soglia fissa per la segmentazione delle immagini.
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Li, Yufei. "Joint super-resolution/segmentation approaches for the tomographic images analysis of the bone micro-structure." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI125/document.
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L'ostéoporose est une maladie caractérisée par la perte de la masse osseuse et la dégradation de la micro-architecture osseuse. Bien que l'ostéoporose ne soit pas une maladie mortelle, les fractures qu'elle provoque peuvent entraîner de graves complications (lésions des vaisseaux et des nerfs, infections, raideur), parfois accompagnées de menaces de mort. La micro-architecture osseuse joue un rôle important dans le diagnostic de l'ostéoporose. Deux appareils de tomodensitométrie courants pour scanner la micro-architecture osseuse sont la tomodensitométrie quantitative périphérique à haute résolution et la tomodensitométrie microscopique. Le premier dispositif donne accès à l'investigation in vivo, mais sa résolution spatiale est inférieure. Le micro tomodensitomètre donne une meilleure résolution spatiale, mais il est contraint à une mesure ex vivo. Dans cette thèse, notre but est d'améliorer la résolution spatiale des images de tomodensitométrie périphérique à haute résolution afin que l'analyse quantitative des images résolues soit proche de celle donnée par les images de tomodensitométrie Micro. Nous sommes partis de la régularisation de la variation totale, à une combinaison de la variation totale et du potentiel de double puits pour améliorer le contraste des résultats. Ensuite, nous envisageons d'utiliser la méthode d'apprentissage par dictionnaire pour récupérer plus de détails sur la structure. Par la suite, une méthode d'apprentissage approfondi a été proposée pour résoudre un problème de super résolution et de segmentation joint. Les résultats montrent que la méthode d'apprentissage profond est très prometteuse pour les applications futuresOsteoporosis is a disease characterized by loss of bone mass and degradation of bone microarchitecture. Although osteoporosis is not a fatal disease, the fractures it causes can lead to serious complications (damage to vessels and nerves, infections, stiffness), sometimes accompanied with risk of death. The bone micro-architecture plays an important role for the diagnosis of osteoporosis. Two common CT devices to scan bone micro architecture is High resolution-peripheral Quantitative CT and Micro CT. The former device gives access to in vivo investigation, but its spatial resolution is inferior. Micro CT gives better spatial resolution, but it is constrained to ex vivo measurement. In this thesis, we attempt to improve the spatial resolution of high resolution peripheral CT images so that the quantitative analysis of the resolved images is close to the one given by Micro CT images. We started from the total variation regularization, to a combination of total variation and double-well potential to enhance the contrast of results. Then we consider to use dictionary learning method to recover more structure details. Afterward, a deep learning method has been proposed to solve a joint super resolution and segmentation problem. The results show that the deep learning method is very promising for future applications
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Barbar, Joseph Salem. "Influência do teor de ar incorporado no desempenho de concretos com diferentes teores de agregados." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/102/102131/tde-23012017-100027/.
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A utilização de aditivos incorporadores de ar em concretos é uma prática comum na construção civil e sua aplicação influencia significativamente diversas propriedades do concreto no estado fresco e endurecido. O objetivo deste estudo foi avaliar a influência do teor de ar incorporado, por meio de aditivo, no desempenho de concretos com diferentes teores de agregados. O programa experimental incluiu avaliação da eficiência de aditivos na incorporação de ar em pastas de cimento, análise microestrutural e ensaios para determinação de propriedades físicas, mecânicas e de durabilidade de concretos com diferentes teores de ar e agregados. No estado fresco, foram realizados ensaios para determinação do teor de ar, massa específica e abatimento. No estado endurecido foram realizados ensaios de massa específica, absorção, resistência à compressão, módulo de elasticidade, velocidade de propagação da onda ultrassônica, carbonatação acelerada e condutividade térmica. Utilizando Microtomografia Computadorizada de Raios-X (Micro-CT) foram dimensionados e quantificados os poros presentes nas amostras dos concretos, bem como determinadas suas porosidades. Os concretos com ar incorporado apresentaram redução na resistência mecânica. Os concretos com menores teores de agregados apresentaram menor resistência mecânica, menor velocidade da frente de carbonatação e menor condutividade térmica. De acordo com os resultados obtidos, pode-se concluir que o aditivo a base de resinas sintéticas foi mais eficiente na incorporação de ar; maiores teores de ar implicam em variabilidade nos resultados de ensaios de resistência à compressão e módulo de elasticidade; os concretos com maiores teores de agregados apresentaram maior velocidade da frente de carbonatação, para mesmos teores de ar incorporado; a condutividade térmica é inversamente proporcional ao teor de ar incorporado no concreto, e quanto menor o teor de agregados, menor a condutividade térmica; o aumento do teor de ar no concreto promove aumento no diâmetro equivalente dos poros e redução da incidência de poros esféricos.The use of entraining air additives in concrete is a common practice in construction and its application influences several concrete properties in the fresh and hardened state. The aim of this study was evaluate the influence of air entrained content, by additive, in concrete performance with different aggregate contents. The experimental program included the evaluation of additives effectiveness of air entrainment in cement pastes, microstructural analysis and the concretes physical and mechanical properties and durability, with different levels of entrained air and aggregates. Tests were performed in fresh to determine the air content, density and slump. In hardened concrete, density, absorption, compressive strength, elastic modulus, ultrasonic pulse velocity, accelerated carbonation and thermal conductivity tests were performed. By computed X-ray microtomography, the pores present in the concrete samples were sized and quantified and determined the concretes porosities. The air entrained concrete presented decrease in mechanical strength. Concretes with lower aggregate levels presented lower mechanical strength, carbonation speed and thermal conductivity. According to the results, it can be concluded that the synthetic resins base additive was more efficient in air entrainment; larger air content implies variability in the results of the compressive strength and elastic modulus tests; concrete with higher aggregate levels presented higher carbonation speed, for the same entrained air content; thermal conductivity is inversely proportional to the air entrained content in concrete, and as lower was the aggregate content, lower was the thermal conductivity; the increase of air content in concrete promotes increase in the pores diameter and reduction of the incidence of spherical pores.
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Bouhnaida, Zaïnaba. "Étude comparative de trois systèmes de préparation canalaire en endodontie : Étude in vitro en micro-CT." Thesis, Reims, 2018. http://www.theses.fr/2018REIMO201/document.
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Le but de cette étude est de comparer le respect de la morphologie canalaire après instrumentation à l’aide de trois systèmes de mise en forme canalaire différents : le One Shape NEW Generation®, le Wave One® et le Revo-S® grâce à une étude en Micro-tomographie assistée par ordinateur ou micro-CT (Computed Tomography). La mise en place d’une chaîne méthodologique totalement tridimensionnelle (3D) comprenant la reconstruction, le recalage et la segmentation a permis de traiter les images acquises et d’extraire les images recalées des canaux dentaires avant et après instrumentation. Les artéfacts de segmentation dus aux calcifications et aux débris dentinaires ont été traités. Une méthode d’estimation des zones non instrumentées a également été décrite.Le transport canalaire a été calculé pour chaque coupe de chaque tiers radiculaire, en comparant la position du centroïde avant et après instrumentation. La comparaison des moyennes de transport canalaire ne montre pas de différence significative entre les 3 systèmes d’instrumentation.Cette approche méthodologique en 4 parties a permis de valider un protocole d’imagerie 3D reproductible, qui pourra être appliqué in vitro en recherche endodontique dans l’analyse des effets instrumentauxThe aim of this study is to compare the respect of the root canal morphology after instrumentation with different shaping systems (One Shape NEW Generation®, Wave One® and Revo-S®), by using Micro-Computed Tomography.We used a fully three-dimensional (3D) methodological process which involved the reconstruction, registration and segmentation. By this methodological process, images have been acquired and processed in order to extract registered canals images before and after the instrumentation. The segmentation artifacts like calcifications and debris have been taken into account. A method to estimate the non-instrumented zones is also described.The canal transportation was calculated for each slice of each root-third by comparing the position of the centroids before and after instrumentation. No significant difference was found between the three instrumentation systems when canal transport means were done.This 4-part methodological approach has enabled the validation of a reproducible 3D imaging protocol. This can be applied in vitro in endodontic research for analysis of the instrumental effects
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Shkarin, Roman [Verfasser]. "Machine learning-based automated segmentation with a feedback loop for 3D synchrotron micro-CT / Roman Shkarin." Karlsruhe : KIT-Bibliothek, 2021. http://d-nb.info/1228439400/34.
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Lemmon, Heber. "Methods for reduced platen compression (RPC) test specimen cutting locations using micro-CT and planar radiographs." Texas A&M University, 2003. http://hdl.handle.net/1969/310.
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Tuchman, Marni. "COMPARISON OF INSERTION ANGULATIONS MEASURED VIA BONE-TO-IMPLANT CONTACT OF MINI-SCREWS USING MICRO-CT." Master's thesis, Temple University Libraries, 2018. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/520294.
Full textAbstract:
Oral BiologyM.S.
Bone-to-implant contact of orthodontic mini-screws has been determined via Micro-CT to be a strong predictor of primary stability. Various insertion angulations, including both 900 and 500, have been reported as ideal for providing optimum primary stability. The aim of this investigation was to determine if a statistically significant difference exists in the bone-to-implant contact of mini-screws placed with an insertion angulation of 900 compared to those placed at 500 as determined via Micro-CT. Ten self-drilling, self-tapping orthodontic mini-screws (Aarhus,1.5mmx6mm) (n=5) were inserted into the posterior ramus of an adult pig mandible, an analog to an adult human mandible. A custom stent with ten holes, five at 900 and five at 500, was fitted to the bone surface to control insertion angulation. The bone was cut to 1.5x1.5x1cm segments and scanned using SkyScan 1127 with ideal specifications (8mm pixel size, medium camera, 80Kv, 100mA, 10W, 1800 rotation, and 0.5Al+0.25Cu filter). The raw scans were reconstructed using NReconV1.6.10 and these datasets were then reoriented using DataviewerV1.5.2 along the Z-axis to standardize the peri-implant bone for analysis. A custom task-list was used with CT-AnalyzerV1.14.41 to determine the percent of bone-to-implant contact per mini-screw. A Mann-Whitney U test indicated that the bone-to-implant contact was not statistically significantly different for the mini-screws placed at 900 (Mdn= 72.34) compared to the mini-screws placed at 500 (Mdn= 53.25), U=5, p=.1443. Therefore, the results do not significantly differ at p<.05. There is no statistically significant difference in the bone-to-implant contact between the Aarhus 1.5mmx6mm orthodontic mini-screws placed at 900 compared to those placed at 500 as measured by Micro-CT. This may lead to the conclusion that there is no significant difference in the primary stability of Aarhus mini-screws placed at 900 and 500.
Temple University--Theses
50
Dong, Pei. "Three-dimensional analysis of bone cellular tissue from SR CT Imaging." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0022/document.
Full textAbstract:
Le système ostéocytaire soulève un intérêt croissant depuis quelques années car il est joue un rôle important dans l'adaptation de l'os. Le système ostéocytaire est inclus dans un réseau poreux dénommé le réseau lacuno-canaliculaire (LCN). L’observation du système ostéocytaire est difficile car les ostéocytes sont profondément enfouies dans la matrice osseuse et difficilement accessible par les techniques optiques. Récemment l’équipe de Creatis a montré la faisabilité d’imager le LCN en 3D grâce à la micro tomographie par rayonnement synchrotron. Toutefois, il n’existe actuellement pas de méthodes d’analyse permettant de quantifier, de façon automatique, le réseau lacuno-canaliculaire en 3D. L’objectif de cette thèse était de développer des méthodes d’analyse d’images permettant d’extraire des paramètres quantitatifs sur le réseau lacuno-canaliculaire. La première partie, consacrée à l’état de l’art. Le chapitre 1 présente les objectifs de ce travail. Le chapitre 2 rappelle les éléments de base sur le tissu osseux et présente les caractéristiques du réseau lacuno-canaliculaire. Le chapitre 3 présente les différentes méthodes d’imagerie utilisées jusqu’à présent pour étudier le réseau lacuno-canaliculaire. Le chapitre 4 présente l’état de l’art sur les paramètres qui sont classiquement utilisés pour caractériser le réseau lacuno-canaliculaire. La seconde partie est consacrée aux contributions de ce travail. Le chapitre 5 présente les deux systèmes expérimentaux de l’ESRF sur lesquels des images d’échantillons osseux ont été acquises. Le chapitre 6 décrit la méthode développée pour la quantification des lacunes ostéocytaires à partir d’images à l’échelle micrométrique. Elle propose de calculer des paramètres issus des moments géométriques ainsi que des paramètres basés sur la notion de volumes intrinsèques. Les méthodes sont appliquées à une série de 13 échantillons acquis en collaboration avec le Laboratoire d’Imagerie Paramétrique, Paris. Les résultats obtenus sont comparés et discutés par rapport à ceux de la littérature. Le chapitre 7 décrit la quantification des canalicules reliant les ostéocytes à partir d’images à l’échelle sous-micrométrique. En particulier, nous nous sommes intéressées à estimer le nombre de canalicules issues d’une lacune ostéocytaire, paramètre encore jamais mesuré en 3D. L’évolution de ce paramètre en fonction de la distance au centre de la lacune a permis de mettre en évidence et de quantifier la ramification des canalicules. Le chapitre 8 propose l’application des méthodes développées à une série d’échantillons acquis en collaboration le groupe de Sharmila Majumdar à l’université de San Francisco. Dans ce chapitre, nous avons travaillé sur une nouvelle méthode de segmentation du réseau lacuno-canaliculaire basée sur une méthode de chemins géodésiques. Les premiers résultats acquis sur 8 échantillons humains d’âges différents sont présentés. Finalement, le chapitre 9 conclut ce travail et présente des perspectivesThe osteocyte system has raised increasing interest in the recent years, since it is hypothesized to play an important role in orchestrating bone adaptation through mechanosensation and bone mechanotransduction mechanism. The osteocytes are deeply buried within the bone matrix, where their bodies are encysted in cavities called lacunae and their stellular processes are enclosed in tunnels called canaliculi. Together, they formed the lacuno-canalicular network (LCN). The geometry of the LCN is of importance since it is supposed to potentially affect and reflect the viability of the osteocyte and is supposed to be related to biomechanical constraints at the cell level. However, studying the LCN is quite challenging, due to limitations in an ideal imaging modality and the lack of quantitative analysis tools. In this thesis, we propose computational efficient and automated methods to quantify the 3D morphological properties of the LCN from synchrotron radiation (SR) micro / nano-CT images. For image acquisition, we used the SR micro/nano-CT setups installed on beamlines ID19 and ID22 at ESRF. A series of human cortical samples were imaged with spatial resolutions ranging between 3.5 µm to 60 nm. For the 3D assessment of lacunae, we used an image moment-based approach to calculate the volume, length, width, height and anisotropy of each osteocyte lacuna. We employed a fast algorithm to further calculate the surface area, the Euler number and the SMI of each lacuna. Validation of segmentation and experimental results on 13 bone samples are presented. For the 3D assessment of canaliculi, we propose a method to quantify the canalicular ramification around each lacuna. After segmentation, our method first labels each lacuna from the LCN. Then, a signature of the numbers of canaliculi at different distances from the lacunar surface is estimated through the calculation of topological parameters. Validation of this method and statistical results a large 3D SR micro-CT image of a human femoral bone sample are reported. We also improved the segmentation of the canaliculi and illustrated the feasibility of the application on a series of bone samples. We investigated a segmentation approach based on minimum cost paths and geodesic voting. A parallel computation scheme was implemented to reduce the computation times. The LCN was characterized by using the previous methods. Besides, we introduced the parameters from the Voronoi tessellation. Statistical results are reported on 8 large 3D micro-CT images, including around a hundred lacunae and the canaliculi. Future works will concern the improvement of canaliculi segmentation of from images at 300 nm as well as its evaluation and further characterization of LCN from SR CT images at both 300 nm and 50 nm. This work opens many perspectives for a better knowledge of the physiopathology of bone at the cellular scale