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Effects of geometric and material property changes on the apparent elastic properties of cancellous boneLIEVERS, WILLIAM BRENT 24 April 2009 (has links)
Osteoporosis is a disease characterized by reduced bone mass and reduced bone quality. This deterioration manifests itself in osteoporotic fractures at skeletal sites containing large proportions of cancellous bone (ie. forearm, hip, spine). Given the costs associated with these fractures, improvements in our ability to model and predict the behaviour of cancellous bone would be of great financial and social benefit to society.
This thesis makes contributions in three areas within the much larger goal of developing a comprehensive model for describing the mechanical behaviour of cancellous bone. Since the accuracy of model predictions can only be as good as the test data against which it is compared, the effect of experimental artifacts introduced by specimen geometry is examined for cored samples. The apparent elastic modulus of cancellous bone is found to be relatively insensitive to specimen (or gauge) length, such that it can be reduced below the recommended 2:1 aspect ratio without introducing detectable artifact. Conversely, apparent modulus is found to be much more sensitive to specimen diameter. The role of water is also examined. Dehydration at room temperature was found to increase the apparent elastic modulus by roughly 14%. This net increase results from the competing effects of an increased tissue modulus and a decreased bone volume fraction due to shrinkage. Finally, preliminary work is presented which attempts to relate micro-CT voxel intensity and locally measured nanoindentation moduli, in order to provide an experimental basis for assigning heterogeneous material properties to finite element method (FEM) models. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2009-04-24 14:28:17.772
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Experimental investigation of two-phase flow properties of small core samplesOlafuyi, Olalekan Adisa, Petroleum Engineering, Faculty of Engineering, UNSW January 2008 (has links)
This thesis presents an experimental investigation of two-phase flow properties of porous rock samples having different scales ranging from micro-CT imaging to conventional core plug scales. Advances in micro-CT imaging of porous materials provide the opportunity to extract representative networks from the images. This improves the predictive capability of porescale network models to predict multiphase flow properties. However, all these predictions need to be validated with laboratory data. Micro-CT imaging is currently limited to small sample sizes, having bulk volumes of the order of 0.1 cm??. Conventional core plugs, however, have sizes several orders of magnitude larger than that (bulk volumes of 10 cm?? or larger). The aim of this thesis is to investigate the scale effect on laboratory data and to provide reliable experimental data which can be used to test the predictive value of microCT based network models. Berea and Bentheim sandstones and Mount Gambier carbonate were used in the experiments. The core samples were thoroughly cleaned in order to obtain strongly, uniform water-wet conditions. Simple well-characterized fluid systems were chosen in the experiments: Air-brine fluid-system for drainage capillary pressure, resistivity index and spontaneous imbibition experiments while oil-brine fluid-system for wettability and relative permeability measurements. Drainage capillary pressure, resistivity index, relative permeability and spontaneous imbibition measurements were made on the cores having bulk volumes ranging from 0.1 to 12 cm??. Previous studies have shown that experiments at this scale are still lacking. The wettability was tried to keep strongly water-wet for all experiments. The experimental results show that the measurements of drainage capillary pressure, and resistivity index and spontaneous imbibition on small core samples, having similar scales as micro-CT imaging can be made accurately in the laboratory. The measurement of relative permeability remains challenging. This thesis concludes that commonly used homogeneous rock types (Berea and Bentheim sandstones and Mt. Gambier carbonate) can be considered to be sufficiently homogeneous from the pore to core scale based on the two-phase flow properties examined in this study. Hence, laboratory data taken from these rocks using conventional core plugs can be used to calibrate micro-CT based network models for multiphase flow properties.
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Micro computed tomography assessment of tumor size in breast cancer compared to histopathological examinationSarraj, Wafa Mowafak 12 March 2016 (has links)
PURPOSE: The purpose of this study was to assess the ability of Micro Computed Tomography (Micro CT) to measure primary tumor size in breast lumpectomy specimens, as compared to the histopathological measurement.
METHODS: This was a diagnostic study involving women who were scheduled to have breast lumpectomy surgery at the Massachusetts General Hospital (MGH) Department of surgery from June 2011 - September 2011. Those who met the study eligibility criteria were recruited to participate in the study. The study was approved by the MGH Institutional Review Board (IRB). All the participants provided consent prior to their participation in the study. The lumpectomy specimens of 45 subjects were scanned by Micro CT scan for no longer than 15 minutes, they were then delivered to the gross pathology lab for processing via the standard pathological protocol. Later on, the maximum dimension of the invasive breast tumor was obtained from the Micro CT image and was compared to the corresponding pathology report for each subject.
RESULTS: We found that Micro CT tends to overestimate the breast malignant tumor size. However, there were few differences in T-stage classification between Micro CT and pathology. Overall, Micro CT demonstrated good agreement with pathological tumor size and staging. For Invasive ductal carcinoma, Micro CT showed a substantial agreement with pathological tumor size and staging. However, Micro CT showed no agreement with pathological tumor size and staging for invasive lobular carcinoma.
CONCLUSIONS: Micro CT is a promising modality in measuring and staging the invasive ductal carcinoma.
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Avaliação volumétrica da obturação dos canais radiculares realizada com diferentes cimentos e técnicas, por meio de microtomografia / Volumetric evaluation of root canal fillings performed with different sealers and techniques through microtomographyVanessa Lessa Cavalcanti de Araujo 21 January 2014 (has links)
O sucesso do tratamento endodôntico está associado não só com a limpeza e a instrumentação do sistema de canais radiculares (SCR), mas com a capacidade de selamento do material obturador principalmente do terço apical. O objetivo do presente estudo in vitro foi analisar o volume de guta-percha e de cimento endodôntico no milímetro apical das obturações, utilizando diferentes cimentos e técnicas de condensação. Para tanto, 64 incisivos centrais superiores foram preparados com instrumentos rotatórios de NiTi até o diâmetro cirúrgico #60.02, e então distribuídos aleatoriamente em quatro grupos. Para cada um usou-se um cimento diferente, a saber: Endofill, Sealer 26, AH Plus e Sealapex. E para cada cimento utilizado, metade dos dentes foi obturada pela técnica de condensação lateral ativa (n=8), e a outra metade, pela técnica da condensação lateral passiva (n=8). Feitas as obturações, os dentes foram submetidos ao exame tomográfico com o uso do microtomógrafo SkyScan 1174 v2. As imagens foram reconstruídas pelo programa NRecon e em seguida foi avaliado o parâmetro tridimensional do volume de cimento e guta-percha no milímetro apical, por meio do programa CTan. A análise de variância a dois critérios para o volume de guta-percha demonstrou haver diferença estatisticamente significante para o fator de variação Cimento endodôntico (p>0,05). Por meio do teste Tukey, observou-se que o grupo obturado com o Sealer 26 apresentou maior volume de guta-percha no milímetro apical do comprimento de trabalho quando comparado ao Endofill que se apresentou com menor volume. Já a análise de variância para o volume de cimento endodôntico demonstrou haver diferença estatisticamente significante para o fator de variação Cimento endodôntico (p<0,05), Técnica obturadora (p<0,05) e pelas interações dos fatores (p<0,05). O teste Tukey para o fator de variação Cimento endodôntico demonstrou que o grupo obturado com o Sealapex apresentou menor volume de cimento no milímetro estudado quando comparado ao grupo obturado com AH Plus e Sealer 26, que evidenciaram maior volume de cimento. Em relação ao fator de variação Técnica obturadora, a condensação lateral ativa apresentou menor volume de cimento comparada técnica passiva. Pode-se concluir que o maior volume de guta-percha foi encontrado nos dentes obturados com o cimento endodôntico Sealer 26, semelhantes aos obturados com Sealapex e AH Plus, independentemente da técnica de condensação. O menor volume de cimento endodôntico foi encontrado no grupo obturado com Sealapex, semelhante ao grupo obturado com o Endofill. Em relação à técnica obturadora, a condensação lateral ativa apresentou menor volume de cimento quando comparada à passiva. / The success of endodontic treatment is associated not only with the cleaning and the instrumentation of the root canal system (RCS) but also with the sealing ability mainly in the apical third of the filling material. The aim of this in vitro study was to analyze the volume of gutta-percha and sealer in the apical millimeter of the fillings, using different obturation technique and sealers. For that purpose, 64 maxillary central incisors were prepared with NiTi rotary instruments until the surgical diameter of #60.02, and then divided randomly into four groups. For each group, different sealers were used, such as Endofill, Sealer 26, AH Plus and Sealapex. And for each sealer used, half the teeth were obturated using an active lateral condensation technique (n=8), and the other half by passive lateral condensation technique (n=8). After the fillings procedures, samples were examined by SkyScan 1174 v2 micro-CT. Images were reconstructed by NRecon software, and then the dimensional parameter of the volume of sealer and gutta-percha at the apical millimeter was evaluated through the CTan program. The ANOVA Two-Way results for the analysis of the volume of guttapercha showed a statistically significant difference for endodontic sealer factor (p>0,05). The Tukey test showed that the group filled with Sealer 26 had higher volume of gutta-percha at the apical millimeter of working length when compared to that of the Endofill, which presented lower volumes. However, the ANOVA Two-Way analysis for the volume of sealer, showed a statistically significant difference for the endodontic sealer factor (p<0.05), obturation technique (p<0.05) and between the interactions of the factors (p<0.05). The Tukey test for the Sealer endodontic variation factor showed that the group filled with Sealapex had the lowest volume of sealer in the studied millimeter when compared to the group filled by AH Plus and Sealer 26, which had the highest volume of sealer. Regarding the filling technique variation factor, the active lateral condensation technique showed lower sealer volume than passive. It can be concluded that the higher volume of gutta-percha was found in teeth filled with sealer Sealer 26, similar to Sealapex and AH Plus, regardless of the technique of condensation. The lowest volume of sealer was found in the group filled with Sealapex, similar to the group filled with Endofill. Regarding the obturation technique, the active lateral condensation technique showed lowest volume of sealer than the passive.
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The impact of bacteria on the biophysics of water retention and flow in soilDello Sterpaio, Patricia January 2012 (has links)
Understanding soil structure, in particular the void spaces through which water, gases and solutes flow and in which organisms exist, is vital to a sustainable future on earth. The investigation of the structural behaviour of soil under different influences is fundamental to understanding and protecting the soil. This study has investigated the impact of bacteria on the biophysics of water retention and flow, aiming to elucidate the effect of three key components produced by the model organism, Pseudomonas fluorescens SBW25. Cellulose is an extracellular polysaccharide involved in the formation of the matrix of the bacterial biofilm, lipopolysaccharide is a cell membrane component required for bacterial attachment, and viscosin is a biosurfactant released from the bacteria. Four isogenic strains mutated so as to heighten or suppress production of one of these key components were used in addition to the wild-type strain. Labfield sandy loam soil was sieved and packed into replicate experimental cores which were incubated with different bacterial treatments. Following sterilisation, the gravimetric water content (u g g-1) of the soil was determined at equilibrated matric potentials from -1 cm to -100 cm during two wet-dry cycles. Sorptivity (S, mm s-1/2) of the soil, indicative of water repellency, was determined using a mini-infiltrometer setup and has been reported as the rate of infiltration of water into the soil. Bacteria have been shown to increase water repellency of soil, decrease the total water content at saturation and increase the water retaining ability of the soil as it drains (p < 0.05). Three-dimensional analysis of core scale structure was carried out using micro X-ray computed tomography (µXCT) and of aggregate scale structure using synchrotron-µXCT. Volumetric analyses of the 3D structures has shown decreased pore connectivity and destabilisation of aggregates in soil systems treated with bacteria deficient in the production of a key extracellular component, cellulose, LPS or viscosin (p < 0.05). Analyses of cracking patterns in two types of sandy loam soil, Labfield and Bullionfield has highlighted the importance of taking into account the soil type and its composition when studying soils, as even within soil classification groups different behaviours are observed. This study has provided clear evidence of the ability of bacteria and their extracellular components to impact upon (i) the hydrodynamics of water retention and flow in soil and (ii) the structural organisation, aggregation and stabilisation of soil.
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Performance of a Micro-CT System : Characterisation of Hamamatsu X-ray source L10951-04 and flat panel C7942CA-22 / Prestanda hos ett Micro-CT System : Karaktärisering av Hamamatsu röntgenkälla L10951-04 och plattpanel C7942CA-22Baumann, Michael January 2014 (has links)
This master thesis evaluated the performance of a micro-CT system consisting of Hamamatsu microfocus X-ray source L10951-04 and CMOS flat panel C7942CA-22. The X-ray source and flat panel have been characterised in terms of dark current, image noise and beam profile. Additionally, the micro-CT system’s spatial resolution, detector lag and detector X-ray response have been measured. Guidance for full image correction and methods for characterisation and performance test of the X-ray source and detector is presented. A spatial resolution of 7 lp/mm at 10 % MTF was measured. A detector lag of 0.3 % was observed after ten minutes of radiation exposure. The performance of the micro-CT system was found to be sufficient for high resolution X-ray imaging. However, the detector lag effect is strong enough to reduce image quality during subsequent image acquisition and must either be avoided or corrected for.
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Evaluation of Quantitative Light-induced Fluorescence to assess lesion depth in cavitated and non-cavitated root caries lesions – an in vitro studyKreher, Deborah 13 July 2022 (has links)
No description available.
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The Roles of the High and Low Molecular Weight Isoforms of Fibroblast Growth Factor 2 in Ischemia-Induced RevascularizationAdeyemo, Adeola T. 26 May 2016 (has links)
No description available.
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Hybrid Spectral Micro-CT: System Implementation, Exposure Reduction, K-edge Imaging Optimization, and Content ManagementBennett, James 21 February 2014 (has links)
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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Compressed Sensing based Micro-CT Methods and ApplicationsSen Sharma, Kriti 12 June 2013 (has links)
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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