Dissertations / Theses: 'Micro-Computed Tomography'

1

Nogueira, Rocha Clementino Luedemann Tatiana. "Micro-computed tomography in caries research." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-70621.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Chen, W. (Wu). "A novel detector micro-module for computed tomography." Doctoral thesis, University of Oulu, 2004. http://urn.fi/urn:isbn:9514274474.

Full text

Abstract:

Abstract To realize faster and more precise treatment of patients, CT technology has an urgent demand to make the CT detector arrays larger, and to cover a larger section of the body during one scan of X-ray imaging. A novel detector micro-module is developed in this thesis to meet this demand. In the novel detector micro-module, photocurrent signals are read out from the bottom side of the photodiode array chip. By avoiding the use of the top surface of the chip for routeing, as is the case in conventional CT modules, rectangular detector building blocks containing a certain number of detector elements can be produced. By tiling such building blocks in both x- and y-directions in a plane, detector arrays with any number of detector elements (in multiples of the number in a single building block) can be built. This cannot be achievable by the conventional method. The novel detector micro-module developed in this thesis consists of an array of 16×16 active elements, and the size of the array is 21×21mm2. The array of detector elements is soldered to a multilayer LTCC (low temperature co-fired ceramics) substrate via a BGA (ball grid array) with each element soldered onto one solder sphere, from which photocurrent signals are read out. In this thesis, the working principle and the evolution of CT detector modules are reviewed and the necessity of developing the novel detector modules is justified. The concept and the structure of the novel detector micro-module are presented. The thermo-mechanical stress modeling and simulation of the structure is performed. The design and the process technology of the photodiode array for the novel detector micro-modules are discussed. The electronic characteristics of the novel detector micro-modules and the related front-end electronics are theoretically analyzed. The LTCC multi-layer substrate is developed. The assembly process of the novel detector micro-module is developed. The basic detector characteristics and light response measurement results of the novel micro-module are presented and discussed. By improving the photodiode silicon process technology, a dark current density as low as 33pA/cm2 is achieved. Excellent mechanical accuracy is achieved with the LTCC substrate. The dimensional tolerance is +/-10μm and the flatness value is less than 50μm over a distance of a 30.5mm distance. A 64-slice detector module is produced successfully by tiling several novel micro-modules. The novel detector micro-modules are superior to conventional CT modules on many respects while being tileable. Their light sensitivity curve is smoother. They exhibit extremely low signal cross-talk; They have nearly zero wiring capacitance compared to up to 20pF in commercial CT detector modules. They also have almost zero wiring resistance compared to tens of ohm or more than one hundred ohms in the present products. This result will have a significant impact on CT technology and the CT industry because the detector will be no longer the limiting factor in CT system performance.

APA, Harvard, Vancouver, ISO, and other styles

3

Ghous, Abid Petroleum Engineering Faculty of Engineering UNSW. "Digital formation evaluation via x-ray micro-computed tomography." Awarded by:University of New South Wales. School of Petroleum Engineering, 2005. http://handle.unsw.edu.au/1959.4/20581.

Full text

Abstract:

Machined fragments of 10 core plugs from oshore reservoirs have been analysed using a high resolution X-ray micro-computed tomography (micro-CT) facility. The facility includes a system capable of acquiring 3D images made up of 20003 voxels on core plugs up to 6 cm diameter with resolutions down to 2 um. The cores analysed include six cores from a gas reservoir and four cores from an oil reservoir. The cores exhibit a very broad range of pore and grain sizes, porosity, permeability and mineralogy. The petrological data, available only for gas reservoir cores, is compared with the data obtained from the tomographic images. Computational results made directly on the digitized tomographic images are presented for the permeability, formation factor, resistivity index and drainage capillary pressure across a range of . We show that data over a range of porosity can be computed from a single fragment. We compare the computations of petrophysical data on fragments to conventional laboratory measurements on the full plug. Permeability predictions from digital and conventional core analysis are consistent. It is shown that a characteristic length scale can be dened as a quality control parameter for the estimation of permeability. Results for formation factor, drainage capillary pressure and resistivity index are encouraging. The results demonstrate the potential to predict petrophysical properties from core material not suited for laboratory testing (e.g., sidewall or damaged core and drill cuttings) and the feasibility of combining digitized images with numerical calculations to predict properties and derive correlations for specic rock lithologies. The small sample size required for analysis makes it possible to produce multiple measurements on a single plug. This represents a potential multiplier on the quantity of core data allowing meaningful distributions or spreads in petrophysical properties to be estimated. We discuss the current limitations of the methodology and suggest improvements; in particular the need to calibrate the simulated data to parallel laboratory core measurements. We also describe the potential to extend the methodology to a wider range of petrophysical properties. This development could lead to a more systematic study of the assumptions, interpretations and analysis methods commonly applied within industry and lead to better correlations between petrophysical properties and log measurements.

APA, Harvard, Vancouver, ISO, and other styles

4

Rytky, S. (Santeri). "Contrast enhanced micro-computed tomography of cartilage and chondrocytes." Bachelor's thesis, University of Oulu, 2018. http://urn.fi/URN:NBN:fi:oulu-201805312341.

Full text

Abstract:

Contrast enhanced micro-computed tomography (CEμCT) is a widely used, cost-efficient method for imaging soft tissues. For articular cartilage imaging, different stains are used to assess amount of cartilage constituents. Osteoarthritis progression can be monitored using CEμCT in clinical environment and laboratory. In clinical modalities, ioxaglate (Hexabrix™) is used to indirectly assess proteoglycan content of cartilage. It is a iodine based anionic stain that has inversely proportional distribution to proteoglycan content. Collagen specific contrast agents are not in clinical use yet. In vitro studies that evaluate osteoarthritis progression use histological staining as a gold standard method. Downside for this is long required time and destruction of sample for a thin, two-dimensional view of the sample. Alternatively, μCT could be used as a non-invasive tool for this when using a collagen stain. One such contrast agent is phosphotungstic acid. It has been shown to be able for three-dimensional evaluation of osteoarthritis grade in same manner as with histological stains. Cationic contrast agent (CA4+) is used in vitro to assess proteoglycan content. It binds to glycosaminoglycan side chains while also slightly accumulating around chondrons. Its advantage is that it binds to target molecule giving accurate information about proteoglycan content when compared to other contrast agents. Chondrocyte imaging with contrast agents is quite demanding. There is not a commonly accepted stain for chondrocytes up to date, but such dyes would be of high interest. Some potential stains might be gallocyanin chrome-alum or glucose-coated gold nanoparticles. A possible method for using gold nanoparticles is proposed in this thesis. There are also studies of chondron morphology using hexamethyldisilazane drying. Downside for this method is tissue shrinkage that might alter at least superficial chondrons. Competing modalities for CEμCT include magnetic resonance imaging (MRI), Fourier transform infrared spectroscopy, near-infrared spectroscopy and Raman spectroscopy. In clinical environment MRI has clear advantage as it does not require utilization of ionizing radiation to produce great soft tissue contrast. High cost and low availability however are main limitations. Spectroscopic methods do not require contrast agents, but especially infrared spectroscopy requires extensive sample preparation and these methods provide only 2D maps of the sample. Latest methods for desktop CEμCT cartilage imaging are reviewed in this thesis. Extracellular matrix assessing methods are studied in clinic and in vitro. Some chondrocyte imaging possibilities are discussed. CEμCT can be used to cost-effectively assess articular cartilage characteristics and OA progression in 3D.

APA, Harvard, Vancouver, ISO, and other styles

5

Amurao, Maxwell Leland Ramirez. "Investigating collagen hydration with micro computed tomography a dissertation /." San Antonio : UTHSC, 2008. http://proquest.umi.com.libproxy.uthscsa.edu/pqdweb?did=1625775011&sid=1&Fmt=2&clientId=70986&RQT=309&VName=PQD.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Rathore, Jitendra Singh. "Computed tomography based quality optimization of micro injection molding." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3422422.

Full text

Abstract:

Micro injection molding is a well-established manufacturing techniques for mass replication of micro parts. However, a new product development requires a process optimization with respect to the desired quality criteria. From the quality aspect, there has been demands for new technologies for quality assessment of the micro products. X-ray computed tomography (CT) is an emerging technology for industrial quality control. The current project focuses on application based quality optimization of micro injection molded parts utilizing X-ray CT. Processing parameters play a significant role in the final part quality; the most crucial parameters are: melt temperature, mold temperature, cooling time, packing pressure etc. The influence of the process parameters on the part quality is investigated by means of design of experiment approach. X-ray CT is an extremely powerful tool which can used for different evaluations and analyses e.g. dimensional metrology, internal porosity, fiber orientation etc. Within the framework of this project, three different studies have been performed based on their critical quality aspects. First study was focused on microfluidics where holistic dimensional quality control is desired. X-ray CT was used for the overall part measurement related to shrinkage and warpage, whereas conventional three dimensional optical profiler was employed used for the micro channel measurements. CT based data fusion approach was applied for the holistic part measurements. Moreover, the effect of electron beam alignment was also studied on the CT measurements of micro molded parts. Fiber-reinforced polymers are commonly used in micro injection applications where higher mechanical properties are desirable e.g. in electronic connectors. Nevertheless, the use of fiber-reinforced polymers affects the desired accuracy, which is attributed mainly to the orientation of fibers in the final part. The non-destructive nature of X-ray CT allows to study the fiber orientation and its effect on the dimensional accuracy of the parts. An experimental investigation was carried out focusing the influence of process parameters (melt temperature, mold temperature, cooling time and packing pressure) on the desired fiber characteristics (orientation, fiber volume content iv etc.). A simulation based study was also performed to validate the CT based characterization of fiber reinforced composites. The last part was focused on a specific micro injection molding application where the internal defects (voids) alter the quality adversely. A series of experimental investigations were made by varying the critical process parameters. X-ray CT was used for the part characterization and quality assessment considering the different quality criteria e.g. total void volume, part volume (shrinkage) etc. Optimal set of process parameters was identified by performing the statistical analysis.
Il micro-srampaggio a iniezione è una tecnica di produzione ben consolidata per la replica in massa di micro parti. Tuttavia, lo sviluppo di un nuovo prodotto richiede un'ottimizzazione di processo conforme ai parametri di qualità desiderati. Dal punto di vista della qualità, sono richieste nuove tecnologie per la valutazione della qualità di micro prodotti e parti. La tomografia computerizzata a raggi X (CT) è una tecnologia emergente per il controllo della qualità nel settore industriale. L'attuale progetto si concentra sull'ottimizzazione della qualità di parti micro-stampate a micro iniezione, utilizzando la CT a raggi X. I parametri di lavorazione giocano un ruolo significativo nella qualità del prodotto finale; i parametri più importanti sono: temperatura del fuso, temperatura dello stampo, tempo di raffreddamento, pressione di compattazione, ecc. L'influenza dei parametri di processo sulla qualità del pezzo viene analizzata tramite la progettazione dell'approccio sperimentale. La tomografia a raggi X è uno strumento estremamente potente che può essere utilizzato per diverse valutazioni e analisi, ad es. metrologia dimensionale, porosità interna, orientamento delle fibre, ecc. Nell'ambito di questo progetto, sono stati condotti tre diversi studi in base agli elementi di qualità più rilevanti. Il primo studio si è concentrato sulla microfluidica dove è desiderato un controllo qualitativo dimensionale olistico. La tomografia a raggi X è stata utilizzata per la misurazione complessiva del pezzo, in particolare per le dimensioni e le deformazioni; mentre la profilometria ottica tridimensionale è stata utilizzata per le misurazioni dei micro canali. La fusione dei dati, ottenuti tramite l’uso della CT è stata utilizzata per le misurazioni olistiche del pezzo. Inoltre, l'effetto dell'allineamento del fascio di elettroni è stato studiato tramite le misurazioni di parti micro stampate utilizzando la tecnologia CT . I polimeri rinforzati con fibre sono comunemente usati nelle applicazioni di micro iniezione in cui sono desiderabili proprietà meccaniche superiori, ad es. nei connettori elettronici. Tuttavia, l'uso di polimeri rinforzati con fibre influisce sulla precisione desiderata, che è attribuita principalmente all'orientamento delle fibre nel prodotto finale. La natura non distruttiva della tecnologia CT a raggi X consente di studiare l'orientamento delle fibre e la sua influenza sulla precisione dimensionale delle parti. È stata condotta un'indagine sperimentale, focalizzando quest’ultima sull'influenza dei parametri di processo (temperatura del fuso, temperatura dello stampo, tempo di raffreddamento e pressione di riempimento) sulle caratteristiche delle fibre (orientamento, contenuto di volume della fibra ecc.). È stato inoltre eseguito uno studio che include l'analisi e la simulazione numerica delle acquisizioni per validare la caratterizzazione, eseguita con tecnologia CT, di compositi rinforzati con fibre. L'ultima parte si focalizza su una specifica applicazione del micro-stampaggio a iniezione dove i difetti interni (i vuoti) alterano la qualità in modo avverso. Una serie di indagini sperimentali sono state eseguite variando i parametri critici del processo. La tomografia a raggi X è stata utilizzata per la caratterizzazione delle parti e la valutazione della qualità considerando i diversi criteri di qualità, ad es. volume totale dei difetti, volume della parte (restringimento) ecc. Il set ottimale dei parametri di processo è stato identificato tramite analisi statistica.

APA, Harvard, Vancouver, ISO, and other styles

7

Lunel, Marie Monique France. "Structure characterisation of catalysts using X-ray micro-computed tomography." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5710/.

Full text

Abstract:

Knowledge of internal porous structure is essential in improving the development of a catalytic system and consequently leading to an optimized performance. XRCT has been used to show differences in density and pore distribution and that differences can be related to the process route by which the specimen was prepared. Alumina samples with defects prepared using different conditions have been investigated in order to acquire information on the introduction and development of cracks. Results indicated that cracks became larger when the water content, the ram speed of the extruder and the drying temperature were higher. The calcination process increased the number and the 3-D size of the cracks. Both concentration of the bulk solution and impregnation time appeared to have a significant impact on the metal distribution profile during the impregnation process. Drying had a strong impact on the metal profile, as a redistribution of copper was noticed. The redistribution was observed exclusively in the case of weak adsorption of copper with alumina support. Experiments on the newly established I13 beamline synchrotron in Diamond was carried out in order to gain an understanding of the cracks induction/propagation and of the diffusion of metallic solution inside the catalyst support.

APA, Harvard, Vancouver, ISO, and other styles

8

Karhula, S. (Sakari). "Quantification of osteochondral tissue modifications during osteoarthritis using micro-computed tomography." Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526220963.

Full text

Abstract:

Abstract Osteoarthritis (OA) is a heterogenic joint disease significantly affecting the quality of life of a patient, causing pain and disability. OA causes degenerative changes to the structure and composition of articular cartilage and subchondral bone. Currently, effective treatments for OA are limited, partly due to limitations in defining the imaging biomarkers of early OA. Improvement of imaging modalities in OA research and clinical setup is a requirement for quantitating early OA-related tissue features. In the clinical and preclinical setup, computed tomography (CT) enables imaging of bone and, using specific contrast agents, articular cartilage. The aim of this study is to create and validate novel micro-computed tomography (μCT) methods to quantify OA-related features and modifications in articular cartilage and subchondral bone. Contrast-enhanced μCT methods for imaging the collagen (phosphotungstic acid (PTA) and phosphomolybdic acid (PMA)) and GAG (CA4+) content of the articular cartilage in vitro were validated against various reference methods measuring the biochemical composition of articular cartilage. To improve the μCT imaging of subchondral bone, grey-level co-occurrence matrix (GLCM) based analysis of sub-resolution features of subchondral bone was introduced. In addition, to test the translatability of the GLCM-based analysis to clinical resolution, sub-resolution features extracted from clinical cone-beam CT were validated against the subchondral bone morphometrics from the μCT. PTA showed stronger association with the collagen content of the articular cartilage compared to PMA. PTA was also associated with collagen content even in degraded articular cartilage. CA4+ distribution was found to accumulate in chondrons and surrounding areas, suggesting that it is a prominent contrast agent for high-resolution μCT studies of chondrocytes. The GLCM-based analysis of subchondral bone provided information on cellular structure from μCT images and trabecular bone micro-structures from clinical CT images. In conclusion, μCT imaging can provide quantitative information on the collagen content and chondrons of articular cartilage, as well as on osteocytes in subchondral bone. The methods presented here extend the tools for researchers to quantify osteochondral tissue modifications in OA. Furthermore, the developed image processing tools could be translatable to the clinical CT
Tiivistelmä Nivelrikko on heterogeeninen niveltauti, joka huonontaa yksilön elämän laatua aiheuttaen kipua ja liikuntakyvyttömyyttä. Nivelrikko aiheuttaa nivelkudosten rappeumaa vaikuttaen mm. ruston ja rustonalaisen luun rakenteeseen ja koostumukseen. Nivelrikon kudosmuutosten kuvantamisen kehittäminen ja määrällinen tutkiminen taudin alkuvaiheissa tukisivat nykyisten nivelrikon hoitomenetelmien kehittämistä. Kliinisessä käytössä ja perustutkimuksessa, tietokonetomografia (TT) mahdollistaa luukuvantamisen ja varjoaineita käytettäessä myös rustokuvantamisen. Tämän väitöskirjan tavoitteena on esitellä ja validoida uusia mikrotietokonetomografia-menetelmiä (μTT) nivelrikon rusto- ja luumuutosten määrälliseen tutkimukseen. Varjoaineavusteisia μTT in vitro menetelmiä ruston kollageenin (fosfovolframihappoa (PTA) ja fosfomolybdeenihappoa (PMA)) ja GAG (CA4+) jakauman määrälliseen tutkimukseen validoitiin useilla eri ruston biokemiallista koostumusta mittaavilla vertailumenetelmillä. Rustonalaisen luun kuvantamista kehitettiin soveltamalla harmaasävyjen tekstuurianalyysiä, jolla pyrittiin tunnistamaan kuva-alkiota pienempiä luurakenteita. Rustonalaisen luun μTT-kuvien analyysien tulokset validoitiin synkrotronisäteilyyn perustuvan μTT:n avulla. Lisäksi tekstuurianalyysin soveltuvuutta testattiin kliinisen resoluution kartiokeilan TT-kuville. Kuvista analysoituja tekstuuriparametrejä verrattiin μTT:lla mitattuun todelliseen rustonalaisen luun rakenteeseen. Väitöskirjan tulokset osoittavat, että PTA on spesifimpi kollageenille testatuista varjoaineista ja sen jakauma on verrannollinen kollageenijakaumaan jopa rappeutuneessa nivelrustossa. GAG-spesifisen varjoaineen CA4+:n todettiin kerääntyvän myös kondroneihin, mikä viittaa siihen, että kyseinen varjoaine soveltuisi potentiaalisesti rustosolujen korkean resoluution μTT-tutkimuksiin. Rustonalaisen luun μTT-kuvista analysoitujen tekstuuriparametrien havaittiin olevan verrannollisia osteosyyttien tilavuusfraktion kanssa. Väitöskirjassa esitettyjen tulosten perusteella μTT-kuvantaminen tarjoaa kvantitatiivisen menetelmän nivelruston kollageenijakauman ja rustosolujen sekä rustonalaisen luun osteosyyttien tutkimuksiin. Väitöskirjassa esitetyt menetelmät laajentavat jo olemassa olevaa tutkimusmenetelmien kirjoa nivelrikon aiheuttamien nivelrusto- ja luumuutosten tutkimuksessa. Lisäksi kehitetyt kuva-analyysimenetelmät voivat tarjota tarkempaa tietoa kliinisestä TT:sta

APA, Harvard, Vancouver, ISO, and other styles

9

Schneider, Philipp. "Ultrastructural phenotyping of murine bone using synchrotron micro- and nano-computed tomography." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17438.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Hagenmüller, Henri. "Combining micro-computed tomography monitoring and mechanical loading in bone tissue engineering /." Zürich : ETH, 2009. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18151.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Niehaus, Wilmari Lianne. "Micro-computed tomography to diagnose and quantify biofilms in central venous catheters." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/382952/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Almeida, Natasha Vasiliki. "Three-dimensional features of chondritic meteorites : applying micro-computed tomography to extraterrestrial material." Thesis, Birkbeck (University of London), 2018. http://bbktheses.da.ulcc.ac.uk/303/.

Full text

Abstract:

This work examines the application of X-ray computed tomography (XCT) in meteoritics. This powerful technique uses the attenuation of X-rays passing through a sample to map it in three dimensions, allowing for the imaging and quantification of phases and features without the need for destructive sampling. XCT is a novel method with its applications to planetary science only recently recognised and not extensively explored. As such, this study presents two examples of using XCT to both elucidate its potential, and better understand the constituents of chondritic meteorites and the processes experienced on their parent bodies. To test the reliability of XCT, the data are conjoined with standard analytical techniques. Firstly, the 3D fabric and textural properties of 17 L chondrites of varying petrological type and shock stage are described. Specifically, porosity is imaged, quantified and compared with pycnometry data. For each chondrite, the size distribution and orientations of metal grains are reconstructed and correlated with the degree and direction of anisotropy of magnetic susceptibility in the sample. Both porosity and metal grain fabrics reveal trends with progressive thermal and shock metamorphism. The mechanisms accounting for such correlation are explored. Secondly, XCT is used to survey fragments of the Barwell L6 meteorite to identify and locate igneous inclusions. From this data, several inclusions were then subsampled and further geochemically investigated, including oxygen isotopic compositions, hafnium-tungsten systematics, and trace element analysis. Studied inclusions are found to be similar in composition and age to chondrules, but depleted in metal. A possible formation scenario is proposed and the potential link to chondrule formation is discussed. Using these examples, the factors influencing the accuracy of XCT data acquisition and processing are described. The benefits and limitations of the technique, with respect to the analysis of extraterrestrial material and implications for future use, are also considered.

APA, Harvard, Vancouver, ISO, and other styles

13

Mairhofer, Stefan. "Extracting root system architecture from X-ray micro computed tomography images using visual tracking." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/27739/.

Full text

Abstract:

X-ray micro computed tomography (µCT) is increasingly applied in plant biology as an imaging system that is valuable for the study of root development in soil, since it allows the three-dimensional and non-destructive visualisation of plant root systems. Variations in the X-ray attenuation values of root material and the overlap in measured intensity values between roots and soil caused by water and organic matter represent major challenges to the extraction of root system architecture. We propose a novel technique to recover root system information from X-ray CT data, using a strategy based on a visual tracking framework embedding a modiffed level set method that is evolved using the Jensen-Shannon divergence. The model-guided search arising from the visual tracking approach makes the method less sensitive to the natural ambiguity of X-ray attenuation values in the image data and thus allows a better extraction of the root system. The method is extended by mechanisms that account for plagiatropic response in roots as well as collision between root objects originating from different plants that are grown and interact within the same soil environment. Experimental results on monocot and dicot plants, grown in different soil textural types, show the ability of successfully extracting root system information. Various global root system traits are measured from the extracted data and compared to results obtained with alternative methods.

APA, Harvard, Vancouver, ISO, and other styles

14

Chopra, Preeti M. "Micro-computed tomographic analysis of bone healing subsequent to graft placement." Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2006. http://www.mhsl.uab.edu/dt/2007m/chopra.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Townsend, Katy Louise. "The Use of Radiographs, Dual-energy X-ray Absorptiometry, Quantitative Computed Tomography and Micro-computed Tomography to Determine Local Cancellous Bone Quality in the Canine Proximal Femur." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1336769521.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Taylor, Thomas Timothy. "Detection of Regional Variation of Bone Mineralization in a Human Mandible using Computed Tomography." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1331042122.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Kiyan, Wataru. "Ultrasound Parameters for Human Osteoarthritic Subchondral Bone Ex Vivo: Comparison with Micro-Computed Tomography Parameters." Kyoto University, 2019. http://hdl.handle.net/2433/236621.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Fritz, Nathan K. "Micro-computed tomography for interlaminar analysis, void quantification, and feature localization in carbon fiber composites." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/118724.

Full text

Abstract:

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 173-180).
In an effort to more fully leverage the relatively rich data within x-ray micro computed tomography ([mu]CT) datasets, two automated analysis tools have been developed which limit subjectivity compared to extant CT analysis of composites. The developed tools extract micron-scale morphological information in three dimensions for laminated advanced composite structures, specifically unidirectional prepreg aerospace-grade carbon fiber reinforced plastic (CFRP) laminated composites. The interlaminar thickness tool locates the interlaminar region and calculates its thickness at each voxel, and the porosity tool quantifies the void volume fraction and localizes each void to the interlaminar or intralaminar regions. Both of these tools were validated on exemplary datasets, and are shown to outperform manual methods. The interlaminar thickness measurements are accurate within 1.5 Jim and well within the standard error of the manual measurement performed via the currently accepted (destructive) method: Scanning Electron Microscopy (SEM). The tool revealed several previously unidentified features of the interlaminar region, including significant fiber misalignment at ply interfaces, and resin-rich regions that extend in the direction of ply microfibers, termed Tow-Aligned Resin Pockets (TARPs) herein. The porosity tool reveals macrovoids (volumes greater than 100 lim3) and microvoids (volumes less than 100 [mu]m 3) and localizes each void to the interlaminar or intralaminar regions. Macrovoids are studied in extant void quantification literature using optical or SEM inspection of cross-sections, but the small microvoids have been overlooked by these analyses and are found to be pervasive in the interlaminar and intralaminar regions. The tools were used to assess two aerospace unidirectional CFRP material systems: autoclave-cured AS4/8552 and out-of-autoclave (OoA) IM7/M56. Laminates of each material were manufactured with and without vertically aligned carbon nanotubes (CNTs) reinforcing the interlaminar region; this hierarchical nanoengineered architecture, termed nanostitching, is of interest in other work to improve strength and toughness of laminates. The analysis shows that the baseline AS4/8552 and IM7/M56 interlaminar thicknesses are 8.6 jrm and 14 jrm thick, respectively, and the nanostitched versions are 2.2 urm and 8.0 jim thicker than the baseline, respectively. TARPs are common to both materials, and are found to become 38 % larger with the addition of CNTs. Void content in the baseline and nanostitched materials was very low, -0.002vol% for the AS4/8552 and -0.001vol% for the IM7/M56. It was found that small microvoids (with diameters on the order of microns) are persistent in both materials, numbering -300 per mm3 with an average volume of 25 [mu]m3, and are generally evenly distributed, although some samples exhibit concentrations of small intralaminar microvoids in the certain plies. Future work will investigate possible connections of the newly-identified features (TARPs and microvoids) to mechanical properties, particularly as they may be damage precursors. Additional materials should be evaluated to determine if these newly-identified features persist in other aerospace-grade composites. In addition to these tools, this work provides a procedure for developing additional [mu]CT analysis tools, such as tools to automate damage identification and quantification.
by Nathan K. Fritz.
S.M.

APA, Harvard, Vancouver, ISO, and other styles

19

Melean, Y., Kathryn E. Washburn, P. T. Callaghan, and Christoph H. Arns. "A numerical analysis of NMR pore-pore exchange measurements using micro X-ray computed tomography." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-192412.

Full text

Abstract:

Pore-pore relaxation exchange experiments are a recent development and hold great promise to spectrally derive length scales and connectivity information relevant for transport in porous media. However, for large pores, NMR diffusion-relaxation techniques reach a limit because bulk relaxation becomes dominant. A combination of NMR and Xray-CT techniques could be beneficial and lead to better models for regions of unresolved porosity in CT images, increasing the accuracy of image based calculations of transport properties. In this study we carry out numerical NMR pore-pore exchange experiments on selected Xray-CT images of sandstones and carbonate rock, while at the same time tracking information about the geometry and topology of the pore space. We use pore partitioning techniques and geometric distance fields to relate T2-T2 relaxation exchange spectra to underlying structural quantities. It is shown that T2-T2 pore-pore exchange measurements at room temperatures for the samples considered likely reflect exchange between pores and throats or pores and roughness.

APA, Harvard, Vancouver, ISO, and other styles

20

Melean, Y., Kathryn E. Washburn, P. T. Callaghan, and Christoph H. Arns. "A numerical analysis of NMR pore-pore exchange measurements using micro X-ray computed tomography." Diffusion fundamentals 10 (2009) 30, S. 1-3, 2009. https://ul.qucosa.de/id/qucosa%3A14125.

Full text

Abstract:

Pore-pore relaxation exchange experiments are a recent development and hold great promise to spectrally derive length scales and connectivity information relevant for transport in porous media. However, for large pores, NMR diffusion-relaxation techniques reach a limit because bulk relaxation becomes dominant. A combination of NMR and Xray-CT techniques could be beneficial and lead to better models for regions of unresolved porosity in CT images, increasing the accuracy of image based calculations of transport properties. In this study we carry out numerical NMR pore-pore exchange experiments on selected Xray-CT images of sandstones and carbonate rock, while at the same time tracking information about the geometry and topology of the pore space. We use pore partitioning techniques and geometric distance fields to relate T2-T2 relaxation exchange spectra to underlying structural quantities. It is shown that T2-T2 pore-pore exchange measurements at room temperatures for the samples considered likely reflect exchange between pores and throats or pores and roughness.

APA, Harvard, Vancouver, ISO, and other styles

21

Wils, Patricia. "Tomographie par rayons X : correction des artefacts liés à la chaîne d'acquisition." Phd thesis, INSA de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00708545.

Full text

Abstract:

L'imagerie cone-beam computed tomography (CBCT) est une méthodologie de contrôle non destructif permettant l'obtention d'images volumiques d'un objet. Le système d'acquisition se compose d'un tube à rayons X et d'un détecteur plan numérique. La recherche développée dans ce manuscrit se déroule dans le contexte industriel. L'objet est placé sur une platine de rotation et une séquence d'images 2D est acquise. Un algorithme de reconstruction procure des données volumiques de l'atténuation de l'objet. Ces informations permettent de réaliser une étude métrologique et de valider ou non la conformité de la pièce imagée. La qualité de l'image 3D est dégradée par différents artefacts inhérents à la plateforme d'acquisition. L'objectif de cette thèse est de mettre au point une méthode de correction adaptée à une plateforme de micro-tomographie par rayons X d'objets manufacturés poly-matériaux. Le premier chapitre décrit les bases de la physique et de l'algorithmie propres à la technique d'imagerie CBCT par rayons X ainsi que les différents artefacts nuisant à la qualité de l'image finale. Le travail présenté ici se concentre sur deux types d'artefacts en particulier: les rayonnements secondaires issus de l'objet et du détecteur et le durcissement de faisceau. Le second chapitre présente un état de l'art des méthodes visant à corriger le rayonnement secondaire. Afin de quantifier le rayonnement secondaire, un outil de simulation basé sur des techniques de Monte Carlo hybride est développé. Il permet de caractériser le système d'acquisition installé au laboratoire de façon réaliste. Le troisième chapitre détaille la mise en place et la validation de cet outil. Les calculs Monte Carlo étant particulièrement prohibitifs en terme de temps de calcul, des techniques d'optimisation et d'accélération sont décrites. Le comportement du détecteur est étudié avec attention et il s'avère qu'une représentation 2D suffit pour modéliser le rayonnement secondaire. Le modèle de simulation permet une reproduction fidèle des projections acquises avec le système réel. Enfin, le dernier chapitre présente la méthodologie de correction que nous proposons. Une première reconstruction bruitée de l'objet imagé est segmentée afin d'obtenir un modèle voxélisé en densités et en matériaux. L'environnement de simulation fournit alors les projections associées à ce volume. Le volume est corrigé de façon itérative. Des résultats de correction d'images tomographiques expérimentales sont présentés dans le cas d'un objet mono-matériaux et d'un objet poly-matériaux. Notre routine de correction réduit les artefacts de cupping et améliore la description du volume reconstruit.

APA, Harvard, Vancouver, ISO, and other styles

22

Stephenson, Robert. "Micro-computed tomography for high resolution soft tissue imaging : applications in the normal and failing heart." Thesis, University of Liverpool, 2013. http://livrepository.liverpool.ac.uk/17313/.

Full text

Abstract:

The normal structure and function of the heart, the common pathological changes that cause abnormal function and the interventions proposed to improve or restore its function are fundamentally based on cardiac anatomy. Therefore in all these areas a detailed and accurate understanding of 3D structure is essential. However there is still disparity over some aspects of the form and function of the healthy heart. Furthermore, in heart failure (HF) the transition from compensated to decompensated HF is poorly understood, and details of ventricular, and particularly atrial, remodelling and their effects on cardiac function are yet to be fully elucidated. In addition little is known on how the 3D morphology of the cardiac conduction system is affected in disease, and further knowledge is required on the structural substrates for arrhythmogenesis associated with HF. Here we have developed contrast enhanced micro-CT for soft tissue imaging, allowing non-invasive high resolution (~5 µm attainable) differentiation of multiple soft tissue types including; muscle, connective tissue and fat. Micro-CT was optimised for imaging of whole intact mammalian hearts and from these data we reveal novel morphological and anatomical detail in healthy hearts and in hearts after experimental HF (volume and pressure overload). Remodelling of the myocardium in HF was dramatic with significant hypertrophy and dilatation observed in both atria and ventricles. The atria showed a 67% increase in myocardial volume, with the left atrium showing a 93% increase. The pectinate muscle: wall thickness ratio was significantly increased in both atria (p=<0.05), and total cavity volume of the atria was increased by 119% (p=<0.05). An 84% (p=<0.05) and 28% (p=<0.01) increase in myocardial volume was seen in the right and left ventricles (RV and LV) respectively. The LV cavity increased to 231% of control (p=<0.001). Regional remodelling occurred in the LV with the base and mid-wall of the heart undergoing eccentric hypertrophy and the apex undergoing mixed hypertrophy. Longitudinal in vivo analysis by echocardiography revealed progressive loss of function pre termination (41% reduction in fractional shortening, p=< 0.001). We have imaged the major regions of the cardiac conduction system (CCS) in single intact hearts and we present the data as high resolution 3D renderings. This is the first time that such data has been shown for any species. In HF all regions of the CCS underwent dramatic morphological changes, with all regions undergoing hypertrophy and stretch. The sinoatrial node showed an 85% increase in volume (p=0.08) and 51% increase in surface area (p=<0.05). The atrioventricular node increased in both volume (52% p=< 0.05) and 3D length (14% p=< 0.05). The free running Purkinje fibre network showed an 85% increase in volume (p=<0.05); 3D filament analysis revealed the free running length was increased by 62% (p=<0.05), and was strongly correlated with the increase in LV cavity volume. Applying a novel technique for the extraction of 3D fibre orientation from micro-CT data we showed that significant changes occur in HF. The technique was first validated in skeletal muscle and then applied to the heart. Fibre orientation in the ventricles was consistent with previous findings, and novel insight into the complex and heterogeneous fibre orientation of the atria and their accompanying muscle bands was obtained. In HF significant changes in fibre orientation were seen in regions of dilatation; in the LV fibres became more vertical at the endocardium and this coincided with a reduction in the transverse angle; in the transmural mid-wall of both the LV and interventricular septum the percentage of circumferential fibres was reduced, and fibres became more disordered. Based on changes in morphology and 3D fibre orientation we present the idea of regional specific compensated and decompensated HF in the presence of volume and pressure overload. Data presented here provides new information on remodelling of the heart in HF, giving insight into the mechanisms underlying the contractile and electrical pathologies associated with HF.

APA, Harvard, Vancouver, ISO, and other styles

23

Kizhakke, Puliyakote Abhilash Srikumar. "Comprehensive assessment and characterization of pulmonary acinar morphometry using multi-resolution micro x-ray computed tomography." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/3120.

Full text

Abstract:

The characterization of the normal pulmonary acinus is a necessary first step in understanding the nature of respiratory physiology and in assessing the etiology of pulmonary pathology. Murine models play a vital role in the advancement of current understanding of the dynamics of gas exchange, particle deposition and the manifestations of diseases such as COPD, Cystic Fibrosis and Asthma. With the advent of interior tomography techniques, high-resolution micro computed tomography (μCT) systems provide the ability to nondestructively assess the pulmonary acinus at micron and sub-micron resolutions. With the application of Systematic Uniform Random Sampling (SURS) principles applied to in-situ fixed, intact, ex-vivo lungs, we seek to characterize the structure of pulmonary acini in mice and study the variations across dimensions of age, location within the lung and strain phenotypes. Lungs from mice of three common research strains were perfusion fixed in-situ, and imaged using a multi-resolution μCT system (Micro XCT 400, Zeiss Inc.). Using lower resolution whole lung images, SURS methods were used for identification of region-specific acini for high-resolution imaging. Acinar morphometric metrics included diameters, lengths and branching angles for each alveolar duct and total path lengths from entrance of the acinus to the terminal alveolar sacs. In addition, other metrics such as acinar volume, alveolar surface area and surface area/volume ratios were assessed. A generation-based analysis demonstrated significant differences in acinar morphometry across young and old age groups and across the three strains. The method was successfully adapted to large animals and the data from one porcine specimen has been presented. The registration framework provides a direct technique to assess acinar deformations and provides critical physiological information about the state of alveolar ducts and individual alveoli at different phases of respiration. The techniques presented here allow us to perform direct assessment of the three-dimensional structure of the pulmonary acinus in previously unavailable detail and present a unique technique for comprehensive quantitative analysis. The acinar morphometric parameters will help develop improved mathematical and near-anatomical models that can accurately represent the geometric structure of acini, leading to improved assessment of flow dynamics in the normal lung.

APA, Harvard, Vancouver, ISO, and other styles

24

Costin, Marius. "Multiresolution Image Reconstruction in X-ray Micro- and Nano- Computed Tomography : Application in Materials Non-Destructive Testing." Lyon, INSA, 2010. http://theses.insa-lyon.fr/publication/2010ISAL0034/these.pdf.

Full text

Abstract:

Dans le cadre d'une large coopération internationale, le projet Saphir a comme but principal la production sure, intégrée et contrôlée de produits nano-structurés multifonctionnels. Dans ce contexte, notre contribution consiste à développer une méthode d'imagerie tridimensionnelle pour inspecter et caractériser les échantillons et les pièces fournis par les partenaires du projet. La tomographie par rayonnement X a été choisie car elle constitue une technique adaptée au contrôle non-destructif. Mais pour des échantillons très complexes présentant des détails sur plusieurs ordres de grandeur, les scanners commerciaux ne répondent pas à tous les besoins et une méthode adaptée a du être développée. Cette thèse établit une base théorique et expérimentale pour une méthode originale capable de produire des images multi-résolution et que nous avons nommé ASDIR (Approximate Single Detail Image Reconstruction). Dans une configuration de type « zoom-in », deux jeux de données sont acquis et fusionnés. La reconstruction de ces données combinées est basée sur l'algorithme standard de rétroprojection filtrée (FBP), mais notre méthode est une extension qui implémente une accélération par l'utilisation de la théorie des ondelettes. Deux versions préliminaires sont également présentées : elles produisent des résultats moins satisfaisants et ont servi de base pour la version finale. Une période importante a été consacrée aux expériences ainsi qu'à l'étude et la compréhension des phénomènes physiques intervenant en CT. Des corrections pour les plus importantes sources d'artefacts ont été mises en oeuvre et leur efficacité a été démontré e grâce à la qualité des images obtenues. Nous avons validé notre approche sur des données simulées et expérimentales. Nous avons généré des données simulées avec des fantômes que nous avons spécialement conçus pour évaluer différentes caractéristiques de la méthode et des échantillons. Les données expérimentales ont été acquises avec deux dispositifs différents, un microtomographe et un nanotomographe, et sur des échantillons de tailles différentes. Une étude de métrologie a été menée sur les images produites et des informations sur la porosité des échantillons ont pu être extraites
In a large international cooperation, the Saphir project aims at producing in a safe, integrated and controlled way, multifunctional nanostructured products. Within this framework, our contribution is the development of a method for three dimensional inspection and characterization of samples and parts produced by the partners. As a starting point, the X-ray computed tomography (CT) was chosen as the most appropriate non-destructive technique. But because the samples are very complex, with features over more orders of magnitude, the available commercial devices could not solve all the requirements and an adapted method for the image reconstruction needed to be developed. This thesis puts a theoretical and an experimental basis for an original method that we abbreviated ASDIR (Approximate Single Detail Image Reconstruction), capable of producing multiresolution images. In a zoom in CT setup, two sets of projections are acquired and combined. The reconstruction is based on the standard filtered backprojection (FBP) algorithm, but we extended it by implementing an acceleration technique that uses a wavelet processing of the data. Two preliminary variants are also presented, which turned out to produce unsatisfactory results, but they were the basis for the final version. We validated our approach on both simulated and experimental data. We generated numerical data with phantoms that we designed specially to assess different features of the method and of the samples. The experimental data was acquired with two different devices, a micro-tomograph and a nano-tomograph, with samples of different sizes. The images that we produced were subject to a basic analysis and we are confident that more information can be extracted from a detailed study

APA, Harvard, Vancouver, ISO, and other styles

25

Hasanpour, Sadegh. "Characterization of porous transport layers of polymer electrolyte membrane fuel cells using X-ray micro-computed tomography." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58406.

Full text

Abstract:

Among different methods available for the estimation of the transport properties of porous transport layers (PTLs) of polymer electrolyte membrane fuel cells, X-ray micro-computed tomography (X-µCT) imaging has been recognized as a viable tool. This method provides the 3D structure of materials with a high resolution. Despite the general success of X-µCT, the following topics have not been explored: first, the porosity obtained for one PTL sample using different methods varies due to arbitrary assumptions made in finding the surface of PTLs. Second, the minimum volume required to obtain permeability and effective diffusivity has not been introduced. Finally, the effect of the cracks of the micro porous layer (MPL) (i.e., the second layer of a dual-layer PTL) on porosity has thoroughly been studied but not for permeability and effective diffusivity. In this thesis, a robust surface identification method, named as "Rolling Ball", is introduced to systematically identify the surface and consequently to measure the porosity of PTLs. The main advantage of this method is that it uses the carbon fibre radius (instead of arbitrary assumptions) to identify the surface and also preserves the surface roughness by following the topology of the surface. Different 3D image sizes of PTLs are also analyzed using Avizo software to identify the representative volume for which the estimated permeability and effective diffusivity are independent of the size. The results of these analyses are compared to the comprehensive model of Tomadakis-Sotirchos (TS), which shows the TS model overestimates through-plane permeability and effective diffusivity. The effect of the cracks in MPL on permeability and effective diffusivity is studied for PTL samples with MPL and the segmented MPL from the PTL. The permeability and effective diffusivity results show a decreasing trend due to the presence of the MPL, which is similar to the results of numerical models previously developed based on the nanopores of the MPL. The consistency between these results and previous models suggests that the cracks play the major role in the transport properties.
Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate

APA, Harvard, Vancouver, ISO, and other styles

26

Chiu, Mei-ling Bonnie, and 趙美玲. "Preparation of curved root canals with different nickel-titanium rotary systems: three-dimensional comparisonusing micro-computed tomography." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31954273.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Huang, Yan. "Structural Mapping of Paper Towels: Comparison of Twin Laser Profilometry and Synchrotron X-ray Micro-computed Tomography." Miami University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=miami1281751951.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Guelpa, Anina. "Maize endosperm texture characterisation using the rapid visco analyser (RVA), X-ray micro-computed tomography (μCT) and micro-near infrared (microNIR) spectroscopy." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96967.

Full text

Abstract:

Thesis (PhD (Food Sc))--Stellenbosch University, 2015.
ENGLISH ABSTRACT: Maize kernels consists of two types of endosperm, a harder vitreous endosperm and a softer floury endosperm, and the ratio of the vitreous and floury endosperm present mainly determines the hardness of the kernel. Maize (Zea mays L.) is a staple food in many countries, including South Africa, and is industrially processed into maize meal using dry-milling. For optimal yield and higher quality products, hard kernels are favoured by the milling industry. Despite many maize hardness methods available, a standardised method is still lacking, furthermore, no dedicated maize milling quality method exists. Using an industrial guideline (chop percentage), a sample set of different maize hybrids was ranked based on milling performance. Unsupervised inspection (using principal component analysis (PCA) and Spearman’s rank correlation coefficients) identified seven conventional methods (hectoliter mass (HLM), hundred kernel mass (HKM), protein content, particle size index (PSI c/f), percentage vitreous endosperm (%VE) as determined using near infrared (NIR) hyperspectral imaging (HSI) and NIR absorbance at 2230 nm (NIR @ 2230 nm)) as being important descriptors of maize milling quality. Additionally, Rapid Visco Analyser (RVA) viscograms were used for building prediction models, using locally weighted partial least squares (LW-PLS). Hardness properties were predicted in the same order or better than the laboratory error of the reference method, irrespective of RVA profile being used. Classification of hard and soft maize hybrids was achieved, based on density measurements as determined using an X-ray micro-computed tomography (µCT) density calibration constructed from polymers with known densities. Receiver operating classification (ROC) curve threshold values of 1.48 g.cm-3 , 1.67 g.cm-3 and 1.30 g.cm-3 were determined for the entire kernel (EKD), vitreous (VED) and floury endosperm densities (FED), respectively at a maximum of 100% sensitivity and specificity. Classification based on milling quality of maize hybrids, using X-ray µCT derived density and volume measurements obtained from low resolution (80 µm) µCT scans, were achieved with good classification accuracies. For EKD and vitreous-to-floury endosperm ratio (V:F) measurements, 93% and 92% accurate classifications were respectively obtained, using ROC curve. Furthermore, it was established that milling quality could not be described without the inclusion of density measurements (using PCA and Spearman’s rank correlation coefficients). X-ray µCT derived density measurements (EKD) were used as reference values to build NIR spectroscopy prediction models. NIR spectra were acquired using a miniature NIR spectrophotometer, i.e. a microNIR with a wavelength range of 908 – 1680 nm. Prediction statistics for EKD for the larger sample set (where each kernel was scanned both germ-up and germ-down) was: R2 V = 0.60, RMSEP = 0.03 g.cm-3 , RPD = 1.67 and for the smaller sample set (where each kernel was scanned only germ-down): R2 V = 0.32, RMSEP = 0.03 g.cm-3 , RPD = 1.67. The results from the larger sample set indicated that reasonable predictions can be made at the fast NIR scan rate that would be suitable for breeders as a rough screening method.
AFRIKAANSE OPSOMMING: Mieliepitte bestaan uit twee tipes endosperm, ‘n harder glasagtige endosperm en ‘n sagter melerige endosperm, en die verhouding waarin die twee tipes endosperm aangetref word, bepaal hoofsaaklik die hardheid van die pit. Mielies (Zea mays L.) is ‘n stapelvoedsel in baie lande, insluitende Suid-Afrika, en word industrieël geprosesseer na mieliemeel deur van droë-vermaling gebruik te maak. Vir optimale produksie en beter kwaliteit produkte, word harde pitte deur die meule verkies. Ongeag die beskikbaarheid van verskeie mielie hardheid metodes, ontbreek ‘n gestandardiseerde metode nog, en verder bestaan ‘n metode om mielies se maalprestasie te bepaal ook nie. ‘n Monsterstel, bestaande uit verskillende mieliebasters, is op grond van maalprestasie ingedeel deur van ‘n industriële riglyn (chop persentasie) gebruik te maak. Inspeksie sonder toesig (deur gebruik te maak van hoofkomponentanalise (HKA) en Spearman’s rangkorrelasiekoëffisiënte) het sewe onkonvensionele metodes (hektoliter massa, honderd pit massa, protein inhoud, partikel grootte indeks, persentasie glasagtige endosperm soos bepaal deur gebruik te maak van naby-infrarooi (NIR) hiperspektrale beelding en NIR absorbansie by 2230 nm) identifiseer as belangrike beskrywers van maalprestasie. Daarbenewens, is Rapid Visco Analyser (RVA) viskogramme gebruik om voorspellingsmodelle te bou deur gebruik te maak van plaaslik geweegte gedeeltelike kleinstekwadrate (PG-GKK) wat hardheidseienskappe kon voorspel met laer, of in dieselfde orde, laboratorium foute van die verwysingsmetodes, ongeag die gebruik van verskillende RVA profiele. Klassifikasie tussen harde en sagte mieliebasters was moontlik, gebasseer op digtheidsmetings soos bepaal met ‘n X-staal mikro-berekende tomografie (µBT) digtheids kalibrasie gebou vanaf polimere met bekende digthede. Ontvanger bedryf kenmerkende (OBK) kurwe drempelwaardes van 1.48 g.cm-3 , 1.67 g.cm-3 en 1.30 g.cm-3 is bepaal vir hele pit, glasagtige en melerige endosperm digthede, onderskeidelik, teen ‘n maksimum van 100% sensitiwiteit en spesifisiteit. Klassifikasie van die mieliebasters, gebasseer op maalprestasie en deur gebruik te maak van X-straal µBT afgeleide digtheid en volume metings soos verkry teen lae resolusie (80 µm) skanderings, was moontlik met goeie klassifikasie akkuraatheid. Vir heel pit digtheid en glasagtigtot-melerige endosperm verhouding metings is 93% en 92% akkurate klassifikasies verkry wanneer OBK kurwes gebruik is. Verder is dit vasgestel (deur gebruik te maak van HKA en Spearman’s rangkorrelasiekoëffisiënte) dat digtheidsmetings ingesluit moet word vir ‘n volledige beskrywing van maalprestasie. X-straal µBT afgeleide digtheid metings is gebruik as verwysings waardes om NIR spektroskopie voorspellings modelle te bou. NIR spektra is verkry deur van ‘n miniatuur NIR spektrofotometer, naamlik ‘n microNIR, bebruik te maak vanaf 908 – 1680 nm. Voorspellings statestiek vir die groter monsterstel (waar elke pit beide kiem-bo en kiem-onder geskandeer is) was vir HPD: R2 V = 0.60, RMSEP = 0.03 g.cm-3 , RPD = 1.67 en vir die kleiner monsterstel (waar elke pit was slegs kiem-onder geskandeer is) vir HPD: R2 V = 0.32, RMSEP = 0.03 g.cm-3 , RPD = 1.67. Die resultate van die groter monsterstel het aangedui dat redelike voorspellings moontlik is, teen die vinnige NIR skaderings tempo wat as rowwe vertoningsmetode geskik sal wees vir telers.

APA, Harvard, Vancouver, ISO, and other styles

29

Chiu, Mei-ling Bonnie. "Preparation of curved root canals with different nickel-titanium rotary systems three-dimensional comparison using micro-computed tomography /." Click to view the E-thesis via HKUTO, 2003. http://sunzi.lib.hku.hk/hkuto/record/B31954273.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Schroeder, Agmar Anthony. "Micro-computed tomography analysis of post space preparation in teeth obturated with carrier-based thermoplasticized gutta percha techniques." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/51594.

Full text

Abstract:

Many dentists use the obturation technique of carrier-based thermoplasticized gutta percha. Placement of a post may be indicated for teeth in which there has been extensive loss of coronal tooth structure. This study aimed to determine if post space preparation deviated from the endodontic preparation in teeth obturated with the Thermafil, GuttaCore, or gutta percha material. Forty-two extracted human permanent maxillary lateral incisors were decoronated and their root canals instrumented with nickel-titanium rotary files using a standardized protocol. Samples were divided into three groups and filled with Thermafil, GuttaCore, or gutta percha, before post space preparation was performed. Teeth were scanned using micro-computed tomography after obturation, and again after post space preparation. Scans were examined for post space deviation, volume and linear deviation of post space preparation, and minimum root thickness before and after post space preparation. Data were analyzed with parametric and non-parametric statistical methods. Deviation occurred in eight teeth; seven from the Thermafil group (50%), one from the GuttaCore group (7%), and none from the gutta percha group. Deviation occurred statistically more often in the Thermafil group than in each of the other two groups (p < 0.05). The volume difference before and after post space preparation was statistically greater in the Thermafil group than in each of the other two groups (p < 0.05). Linear deviation of post space preparation was greater in the Thermafil group than in both of the other groups, and was statistically greater than that of the gutta percha group (p < 0.05). The minimum root thickness before post space preparation was significantly greater than it was after post space preparation for all groups (p < 0.01). There was no difference between the groups with respect to the difference in minimum root thickness before and after post space preparation. The differences in the number of samples showing post space deviation, volume, and linear deviation of post space preparation amongst the Thermafil, GuttaCore, and gutta percha groups were due to the presence or absence of a carrier as well as the different carrier materials.
Dentistry, Faculty of
Graduate

APA, Harvard, Vancouver, ISO, and other styles

31

Khoshkhou, Danial. "The use of synchrotron X-ray micro computed tomography to study the failure mechanisms of thermal barrier coatings." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7817/.

Full text

Abstract:

Thermal barrier coatings (TBCs) are used to protect high-pressure stage 1 turbine components in aero engines. At present the full potential high-temperature capabilities of TBCs cannot be utilised due to the difficulties in estimating the remaining useful life of in-service TBCs. State of the art non-destructive techniques, such as photo-luminescent piezospectroscopy (PLPS) have aided in furthering the understanding of damage evolution mechanism techniques, but are limited in applicability at temperature. In this work, a new force-balance model is presented for calculating the growth stress in a thermally grown oxide (TGO) layer at oxidation temperatures. Furthermore, a new experimental technique is explored for observation of the full-field strain distribution using synchrotron X-ray microtomography (SX μCT) coupled with digital volume correlation (DVC). The forcebalance method relates the creep in bondcoats of precision-machined cylindrical micro-specimens to the stress acted on the bondcoat by the TGO. These precisionmachined specimens were volumetrically imaged at the I12 JEEP beamline of Diamond Light Source (DLS) to reveal the three-dimensional evolution of TBC microstructure with time at temperature. The time-dependent volumetric image data acquired at DLS were processed using commercial digital volume correlation code to compute full-field displacement and strain distribution.

APA, Harvard, Vancouver, ISO, and other styles

32

Couves, Colette Rose. "Investigating the petrophysical properties of volcanic reservoir analogues through the use of micro-focus X-ray computed tomography." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/396580/.

Full text

Abstract:

Volcanic rocks can host significant hydrocarbon resources but are poorly understood in terms of their reservoir properties: especially their porosity and permeability characteristics. Basaltic lavas and volcaniclastic outcrops around Tenerife and basaltic lava flows from the Large Igneous Provinces of the Deccan Traps and the Faroe Islands were studied as potential “reservoir analogues” to compare with existing hydrocarbon discoveries in volcanic rocks. These studies together with the analysis of subsurface samples from South America permitted the geochemical and petrophysical properties of several volcanic reservoir analogues to be examined. Field observations of flow morphology and continuity of defined lava flow facies, were integrated with conventional core porosity and permeability measurements and the results of a micro-focus X-ray tomography (µCT) study to characterize the petrophysical properties of various volcanic rocks. Application of µCT allows the quantification and 3D visualisation of the pore space down to a µm scale and thus provides unprecedented insights into pore morphologies. When combined with traditional petrographic observations, this provides a powerful tool with which to analyse porosity development. Vesicles and fractures are the principle controls upon effective porosity development with permeability often controlled by the degree of vesiculation. Samples with vesicle densities greater than 20 % show significantly higher permeabilities and higher effective porosities due to the increased degree of vesicle coalescence forming connected networks. Individual lava flows can be divided into base, core and top facies, with lava piles comprising repeated cycles of these distinct facies. The best reservoir quality occurs in basalt flow tops (mean µCT ? = 21.85%) where vesicular porosity dominates. Reservoir quality significantly decreases in the tight flow cores, where primary porosity is controlled by cooling joints (fracture porosity) and inter-crystalline micro-porosity (mean µCT ? = 2.32%). Flow bases show variable reservoir potential due to the presence of breccia and/or vesiculation, depending upon the eruption environment (e.g. subaerial v subaqueous) and original geochemistry (e.g. acidic v basaltic) of the lava (mean µCT ? = 9.70%). The most porous horizons are the flow tops of each successive lava flow, whilst connectivity (permeability) between these horizons is via primary cooling joints or secondary fractures. Volcaniclastic lithologies of, tuff, ignimbrite, scoria and pumice, have the highest porosity and permeability (mean µCT ? = 48.09%). Distribution of the various volcanic facies is influenced by the magma chemistry, cooling rate and mode of eruption. The primary porosity and the permeability of the rocks may be subsequently modified either to create additional porosity and permeability by tectonic fracturing and dissolution during burial or weathering, or occlude porosity through the precipitation of secondary minerals and the alteration of primary minerals. Given volcanic rocks can exhibit high porosity (especially within flow top internal zones and to as lesser extent flow bases) these lithologies can form viable reservoirs. The stacking of successive flows results in a layer cake stratigraphy, with the more porous and permeable flow tops and bases separated by relatively impervious flow cores. Should sufficient fractures and cooling joints exist, then these reservoir horizons will be in communication with each other, permitting charging of hydrocarbons. The conclusion of this thesis is that despite low permeabilities, volcanic rocks are good hydrocarbon prospects, and understanding the distribution of these key internal zones and their characteristic porosities and permeabilities will enhance hydrocarbon exploration within these unconventional reservoirs.

APA, Harvard, Vancouver, ISO, and other styles

33

Lu, Jing [Verfasser]. "Advanced Methods for the Quantification of Trabecular Bone Structure and Density in Micro Computed Tomography Images / Jing Lu." Aachen : Shaker, 2011. http://d-nb.info/1071528580/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

35

Jonsson, Åsa, and Grim Skarsgård. "Synchrotron tomography of pressboard during in-situ compression loading : Construction of compression rig, image acquisition procedure and methods for image processing." Thesis, Uppsala universitet, Tillämpad mekanik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-257276.

Full text

Abstract:

Pressboard, a high density cellulose-based material used for insulation in high voltage power transformers, exhibits stress relaxation during compressive loading. Investigating the micro-mechanical mechanisms responsible for the relaxation can lead to modifications of the production process to control the behaviour of the material. This investigation can be done using Synchrotron X-ray micro Computed Tomography which provides sufficient temporal and spatial resolutions to capture the stress relaxation process. In the present thesis, a compression rig for in-situ mechanical loading during X-ray micro Computed Tomography was designed and constructed. Local tomography scans with sub-micrometre resolution were obtained at the TOMCAT beamline at the Swiss Light Source, Paul Scherrer Institut, Switzerland. Several fibre segmentation techniques are analysed, together with Optical Flow and Digital Volume Correlation (DVC), methods used for estimating displacement, strain and velocity vector fields. Suitability of the tested methods is evaluated, and it is found that segmentation of individual fibres in a cellulose material of such a high density is probably not possible using currently available segmentation techniques. The movements during relaxation are measurable at the used resolution, and can be estimated using Optical Flow. Further work into correction of image shift due to rig movement between scans, as well as image artefact reduction should allow for measurement and comparisons of displacement during relaxation as well as DVC-computed strain measurements during compression, recreating earlier results.

APA, Harvard, Vancouver, ISO, and other styles

36

Sen, Sharma Kriti. "Compressed Sensing based Micro-CT Methods and Applications." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/52866.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

37

Opie, Alexander M. T. "Contributions to spectral CT." Thesis, University of Canterbury. Electrical and Computer Engineering, 2013. http://hdl.handle.net/10092/8532.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

38

知紀, 山口, and Tomonori Yamaguchi. "Microstructural analysis of three-dimensional canal network in the rabbit lumbar vertebral endplate using high-resolution micro-computed tomography." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12908294/?lang=0, 2014. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12908294/?lang=0.

Full text

Abstract:

椎間板変性を引き起こす要因として、骨性終板内の栄養管狭小および軟骨終板の石灰化による椎間板への栄養供給の低下が推察されているが、椎体終板内栄養管の3次元微細構造は未だ明確にされていない。本論文は高解像度マイクロCTを用いて家兎腰椎骨性終板内栄養管の3次元微細構造を明らかにする事を目的とし、各栄養管の長さ,直径,配向及び表面からの深さを定量的に解析することでその多層構造を定量的に評価することができた。
Insufficient nutrient supply through vertebral canal structures to the intervertebral disc (IVD) has been considered as an important contributor for disc degeneration. In spite of this, three-dimensional (3D) topology inside the vertebral endplate remains poorly understood. This study aims to characterize the 3D canal structure in the rabbit lumbar vertebral endplate using micro computed tomography (µCT), and revealed a distinct depth-dependent structure of the canal in the rabbit vertebral endplate characterized by length, diameter and orientation of the individual canals.
博士(工学)
Doctor of Philosophy in Engineering
同志社大学
Doshisha University

APA, Harvard, Vancouver, ISO, and other styles

39

HAIDE, Robert Christian. "Characterization of Multi-Phase Fluid Displacement in Porous Media during Drying by means of X-Ray Micro Computed Tomography." Doctoral thesis, Università degli studi di Bergamo, 2021. http://hdl.handle.net/10446/189681.

Full text

Abstract:

Lo spostamento del fluido in mezzi porosi durante la lenta essiccazione in atmosfera controllata viene esplorato a livello dei pori, utilizzando la tecnica della micro tomografia computerizzata a raggi X. A tal fine, un corpo campione regolare, poroso e di dimensioni micro-metriche, che presenta una struttura dei pori e una bagnabilità predefinite, è concepito e prodotto sulla base di una serie di esperimenti preliminari. Dopo l’infusione con acqua distillata, viene studiato il comportamento di essiccazione del campione in atmosfera controllata. Successivamente viene definita e condotta una serie di esperimenti tomografici e vengono valutati i dati risultanti. Un punto focale principale è l’ottimizzazione dell’intera catena del processo di acquisizione dei dati tomografici ad alta risoluzione. Questo include la preparazione del campione, la definizione dei parametri di scansione, gli approcci di ricostruzione, così come l’elaborazione e la segmentazione delle immagini. Un approccio sistematico in tutti questi settori fornisce una visione d’insieme delle lacune esistenti e delle potenzialità ancora non sfruttate della tomografia micro computata a raggi X come strumento per studiare i processi di essiccazione a livello dei pori. Il secondo punto focale principale è la segmentazione dei dati e il contenuto informativo dei dati segmentati relativi agli eventi di spostamento dei fluidi a livello dei pori durante l’essiccamento. I modelli di rete dei pori vengono estratti e trasmessi, in combinazione con i dati valutati, a progetti di ricerca correlati sulla simulazione e la visualizzazione per ulteriori usi e scopi di validazione.
Fluid displacement in porous media during slow drying in controlled atmosphere is explored on the pore-level, by using the technique of X-ray micro computed tomography. To this end, a regular, porous sample body of micro-metric dimensions, which exhibits a predefined pore structure and wettabilty, is conceived and produced on basis of a set of preliminary experiments. After infusion with distilled water, the drying behavior of the sample in a controlled atmosphere is investigated. Subsequently a set of tomographic experiments is defined and conducted, and the resulting data is evaluated. One main focus point is set on the optimization of the whole process chain of acquiring high-resolution tomographic data. This includes the sample preparation, definition of scanning parameters, reconstruction approaches, as well as image processing and segmentation. A systematic approach in all of those domains provides insight into the existing shortcomings and the existing, as well as the yet untapped potential of X-ray micro computed tomography as a tool to investigate drying processes on the pore-level. The second main focus point is set onto the segmentation of the data and the information content of the segmented data regarding pore-level fluid displacement events during drying. Pore network models are extracted and relayed in combination with the evaluated data to related research projects on simulation and visualization for further usage and validation purposes.

APA, Harvard, Vancouver, ISO, and other styles

40

Agbogun, Henry Mosimabale. "Three-Dimensional Measurement of Porosity and Solute-Concentration Distributions during Diffusion in Porous Geologic Media Using X-ray Micro-Computed Tomography." Thesis, Fredericton: University of New Brunswick, 2011. http://hdl.handle.net/1882/36022.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

King, Shalinie. "A diet high in fat and fructose in rats: impact on osseointegration, bone structure and function." Thesis, The University of Sydney, 2019. https://hdl.handle.net/2123/21294.

Full text

Abstract:

Diets high in fat and sugar are associated with metabolic dysfunction including reduced bone quality. This thesis considers whether diet-induced metabolic changes adversely affect bone metabolism including implant osseointegration in female rats. Sprague Dawley rats were divided into three groups of n=10, control group (normal chow), 2 intervention groups on a high fat (60%) high fructose (20%) diet, and a sham surgery group (SS, n=4). Implants were placed in the proximal tibia at week 1 (control /SS groups), 6 weeks after (HFHF group) or 4 weeks before (dHFHF group) commencing the diet, and observed for 8 weeks. Metabolic function was assessed by insulin and glucose tolerance, fasting blood glucose levels, and body composition. Structural and functional features of bone in the peri-implant region, tibia and vertebra were analysed ex vivo using microCT and histomorphometry. Bone metabolism was analysed by quantifying plasma levels of bone turnover markers, P1NP and CTX-1; and expression of bone regulatory genes, Runx2, and Pparγ. Metabolic dysfunction was more pronounced in the dHFHF group. Bone structure was compromised in the HFHF group and minimally compromised in the dHFHF group with tibiae being more compromised than vertebrae. Bone-to-implant contact and bone cell function in the peri-implant region were reduced in both diet intervention groups as was bone metabolism (reduced P1NP and Runx2). Additionally, in the dHFHF group CTX-1 and osteoclast numbers were reduced while Pparγ expression was upregulated. Metabolic outcomes were worse when the HFHF diet was commenced at an older age. Bone structure was more compromised when the diet was commenced at a younger age and was site specific. Osseointegration was compromised independent of metabolic changes and, regardless of whether the diet was commenced before or after implant placement. These changes were mediated by altered bone cell formation and function resulting in an overall reduction in bone turnover.

APA, Harvard, Vancouver, ISO, and other styles

42

Bashoor, Zadeh Mahdieh. "Geometric characterization and simulation of cell-mediated resorption for porous bone substitutes using micro computed tomography and advanced fuzzy method." Thèse, Université de Sherbrooke, 2011. http://savoirs.usherbrooke.ca/handle/11143/1950.

Full text

Abstract:

The objective of this thesis is to provide an improved characterization of porous scaffolds. A more focused objective is to provide a computational model simulating the cell mediated resorption process of resorbable bone substitutes. The thesis is structured in three scientific manuscripts. The first manuscript used fuzzy-based image treatment methods to analyse images generated by micro-computed tomography. From the literature, it is known that the fuzzy-based method helps to improve the accuracy of the characterization, in particular for scaffolds featuring a relatively small pore size. In addition, a new algorithm was introduced to determine both pore and interconnection sizes. The surface area of bone substitutes was quantified by using marching cube algorithm. Besides, the so-called Lattice Boltzmann method was used to characterize the permeability of the investigated scaffolds. Scaffolds made of [béta]-tricalcium phosphate ([béta]-Ca[subscript 3](PO[subscript 4])[subscript 2]) and presenting a constant porosity and four variable pore sizes were examined. The average pore size (diameter) of the four bone substitute groups (denominated with a letter from group A to D) was measured to be 170.3«1.7, 217.3«5.2, 415.8«18.8 and 972.3«10.9 [micro]m. Despite this significant change in pore size, the pore interconnection size only increased slightly, in the range of 61.7 to 85.2 [micro]m. The average porosity of the four groups was 52.3«1.5 %. The surface density of scaffolds decreased from 11.5 to 3.3 mm[superscript -1], when the pore size increased. The results revealed that the permeability of scaffolds is in the same order of magnitude and increased from 1.1?10[superscript -10] to 4.1?10[superscript -10] m[superscript 2] with increasing the pore size. The second manuscript was devoted to the use of subvoxelization algorithm and high-resolution scanner, in an attempt to further improve the accuracy of the results, in particular, of the small pore scaffolds. As expected, an increase of the image resolution from 15 to 7.5 [micro]m significantly eased the segmentation process and hence improved scaffold characterization. Subvoxelization also improved the results specifically in terms of interconnection sizes. Specifically, much smaller interconnection sizes were yielded after applying the subvoxelization process. For example, the mean interconnection size of small pore size groups, group A and B, dropped from 63 to 20 and 30 [micro]m, respectively. Furthermore, due to more details obtained from subvoxelization and high-resolution scanning, additional effects so called"boundary effects" were observed. The boundary effects can yield misleading results in terms of interconnection sizes. The means to reduce these effects were proposed. The third manuscript focused on the simulation and understanding of cell mediated resorption of bone graft substitutes. A computer model was developed to simulate the resorption process of four bone substitute groups. [mu]CT data and new"image processing" tools such as labelling and skeletonization were combined in an algorithm to perform the steps of resorption simulation algorithm. The proposed algorithm was verified by comparing simulation results with the analytical results of a simple geometry and biological in vivo data of bone substitutes. A correlation coefficient between the simulation results and both analytical and experimental data, was found to be larger than 0.9. Local resorption process revealed faster resorption in external region specifically at earlier resorption time. This finding is in agreement with the in vivo results. Two definitions were introduced to estimate the resorption rate; volume resorption rate and linear resorption rate. The volume resorption rate was proportional to accessible surface and decreased when the pore size increased, while the linear resorption rate was proportional to thickness of material and increased with increasing the pore size. In addition, the simulation results revealed no effect of resorption direction on resorption behaviour of substitutes. However, the resorption rate of small pore size samples was decreased with increasing the minimum interconnection size required for cell ingrowth, to 100 [micro]m. This thesis combined novel"image processing" tools and subvoxelization method to improve the characterization of porous bone substitutes used in the bone repair process. The improved characterization allowed a more accurate simulation process. The simulation data were consistent with previously obtained biological data of the same group and allows understanding the local resorption process. The available tools and results are expected to help with the design of optimal substitute for bone repair."--Résumé abrégé par UMI.

APA, Harvard, Vancouver, ISO, and other styles

43

Yin, Xianzhen. "Structure Pharmaceutics Based on Synchrotron Radiation X-Ray Micro- Computed Tomography: From Characterization to Evaluation and Innovation of Pharmaceutical Structures." Thesis, University of Bradford, 2016. http://hdl.handle.net/10454/17378.

Full text

Abstract:

Drug delivery systems (DDS) are essentially pharmaceutical products for human therapy, typically involving a mixture of active ingredients and excipients. Based upon quantitative characterization of structure, the thesis introduces the concept of classifying the architecture of DDS into four levels by their spatial scale and the life time period. The primary level is recognised as the static structure of the whole dosage form with a size from μm to cm with the final structure generated by formulation design. The secondary level categorises the structures of particles or sub-units to form a DDS with sizes from nm to mm as key units in processing such as mixing, grinding, granulation and packing; The tertiary level represents the dynamic structures of DDS during the drug release phase in vitro or in vivo incorporating the structure size range from nm to mm, which undergo changes during dissolution, swelling, erosion or diffusion. The spatial scale for the quaternary level is defined as the meso or micro scale architecture of active and non-active molecules within a DDS with sizes from Å to μm for the molecular structure of drug and excipients. Methods combining X-ray tomography, image processing, and 3D reconstructions have been devised and evaluated to study systematically pharmaceutical structures and correlate them with drug release kinetics of DDS. Based on the quantitative structural information of pharmaceutical intermediates and dosage forms, it is possible now to correlate structures with production processing, behaviour and function, and the static and dynamic structures of DDS with the release kinetics. Thus, a structure-guided methodology has been established for the research of DDS.
Chinese Academy of Sciences

APA, Harvard, Vancouver, ISO, and other styles

44

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/.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

45

Spaw, Alexandra J. "Fetal Developmental Anatomy of the Human Cardiovascular and Central Nervous Systems Using Lugol’s Iodine Staining and Micro-Computed Tomography." Ohio University Honors Tutorial College / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1398950897.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Jensen, Lauren Elizabeth. "Mechanical preparation of oval-shaped root canals in mandibular premolars with the TRUShape 3D Conforming File: a micro-computed tomography study." Thesis, University of Iowa, 2017. https://ir.uiowa.edu/etd/5523.

Full text

Abstract:

The TRUShape 3D Conforming File (TRUShape), a novel, S-shaped nickel-titanium (NiTi) rotary file, was developed to facilitate cleaning and shaping of irregular-shaped root canals. The purpose of this study was to evaluate the shaping ability of TRUShape compared to Vortex Blue (VB) when used in non-round, oval-shaped root canals by micro-computed tomography (MCT). Thirty single-rooted human mandibular premolar teeth with radiographically similar root canal size and curvature were randomly allocated to two groups (N=15), and mechanically prepared with TRUShape or VB. Each tooth was submitted to MCT at 20 μm resolution at three time intervals: before shaping, and after shaping to an intermediate apical size 30 and a final apical size 40. Three-dimensional data sets were superimposed and evaluated for root canal volume, surface area, and treated surface. Matched axial slices in the apical, middle, and coronal root thirds were evaluated for area, roundness, and canal transportation expressed as center of mass shift (CMS). Data were statistically analyzed using parametric and non-parametric tests. Root canal volumes increased similarly and significantly overall (p< 0.001; from an initial volume of 7.3±3.5 mm3 to an intermediate volume of 8.7±3.1 mm3 and a final volume of 9.9±3.0 mm3). Treated canal surface was significantly larger in the TRUShape group at both apical sizes 30 and 40 with 72±15% vs. 55±23% and 85±12% vs. 71±20% non-static voxels for TRUShape and VB, respectively (p< 0.05). Canal transportation was less than 100 μm in all but 8 out of 90 cross sections and was not significantly different between groups. This MCT study demonstrated the TRUShape 3D Conforming File to be effective in the mechanical preparation, specifically, the surface treatment, of single-rooted premolars with non-round, oval-shaped root canals. Funding was provided by the American Association of Endodontists (AAE) Foundation and the Department of Endodontics at the University of Iowa, College of Dentistry.

APA, Harvard, Vancouver, ISO, and other styles

47

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.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Baumann, Michael. "Performance of a Micro-CT System : Characterisation of Hamamatsu X-ray source L10951-04 and flat panel C7942CA-22." Thesis, KTH, Skolan för teknik och hälsa (STH), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155454.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

49

Lai, Wendy Wing Man. "The quality of root canal filling in mandibular molars utilizing warm vertical and single cone technique : a three-dimensional micro-computed tomography." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58669.

Full text

Abstract:

The goal of the root canal filling procedure is the total 3-dimensional filling of root canals and accessory canals. With the development of innovative sealers and gutta percha in matching taper and diameter as rotary instruments, the single cone technique is gaining popularity. Objective: To compare the percentage of voids and gaps in the coronal, middle and apical third of mandibular molar root canals obturated with different sealers and techniques using micro-computed tomography. Hypothesis: No differences in the percentage of voids and gaps are found between: 1) the obturation groups; 2) the mesial or distal canals of the mandibular molars; and 3) the root canal thirds. Methods: Thirty extracted two-rooted human mandibular molars were divided into three experimental groups: 1) single cone technique using ThermaSeal Plus sealer; 2) warm vertical technique using ThermaSeal Plus sealer; and 3) single cone technique using BC sealer. All canals were instrumented with Vortex Blue 0.04 files to an apical size of #35 (mesial) and #40 (distal). The teeth were mounted on a custom attachment for post-instrumentation and post-obturation micro-CT scan. The scans were examined for the relative proportions of voids and gaps in the coronal, middle and apical third of mandibular molar root canals. Data were analyzed with mixed effects models and Wald chi-square test. Results: A statistically higher percentage of gaps was found in the apical third compared to the coronal third and the middle third of the canal (p <0.05). No significant differences in voids were found in the root canal thirds. No significant differences in voids and gaps were found between the three obturation groups or between the mesial and distal canals (p > 0.05). None of the methods were able to produce a void-free root filling and voids occurred in both mesial and distal canals with no predilection for any part of the canals. Conclusion: Within the limitations of this study, it appears that the single cone technique utilizing gutta percha in matching taper and size as rotary instruments is a suitable alternative for obturation of mandibular molars as compared to the warm vertical technique.
Dentistry, Faculty of
Graduate

APA, Harvard, Vancouver, ISO, and other styles

50

Cumpston, Devan N. "New Approaches to Studying Coronary Collateral Growth in a Mouse Model." NEOMED Integrated Pharmaceutical Medicine / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ne2mh1558708401226297.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Micro-Computed Tomography'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles