Low-velocity impact damage in IM7/977-3 carbon fiber reinforced polymer (CFRP) composites was investigated using 3D computed tomography (CT). 32-ply IM7/977-3 symmetric cross-ply composites were impacted at different impact energy levels and with different impactors (DELRIN® resin flat-ended cylindrical and tool steel hemispherical strikers) using an Instron 8200 Dynatup drop-weight impact machine. The impact energies were chosen to produce slightly visible damage, characterized by short cracks on the impacted surface and little delamination on the non-impacted surface (29.27 J), and barely visible damage, characterized by indentation on the impacted surface but no visible delamination on the back surface of the specimens (20.77 J). Internal damage was assessed using the Zeiss METROTOM 1500 industrial CT scanning system, and CT images were reconstructed using VGStudio MAX and the MyVGL 2.2 viewer. To determine the extent of the damage zone, impacted 152.4 mm square composite plates were initially scanned. As the relatively large specimen size did not allow for evaluation of internal cracks and isolation of delamination at ply interfaces, smaller specimens that enclosed the damaged region (45 mm square plates) were cut out and imaged. The CT scan results showed that volume of the impact damage zone had a generally positive correlation with impact energy, maximum load, and maximum deflection, but that the relationship was generally weak. Absence of a definite correlation between damage volume and impact energy was unexpected, as the difference in the impact energy was up to 30%.

Introduction: Root resorption is an undesired but frequent side effect of orthodontic treatment. Several studies have already aimed to evaluate the performance of CBCT on this topic. However, none have addressed the peculiarities of the most common daily orthodontic scenario. The aim of the study was to evaluate the influence of CBCT scans on the diagnosis of artificial external root resorption in the apical third of anterior teeth. Materials and methods: One hundred extracted human anterior teeth were randomly assigned to 2 uneven groups (51 as the control and 49 as the experimental group). A limited area of the apical third of the root of the teeth of the experimental group was selected and a buffer solution was used to induce tooth subsurface demineralization. Before CBCT image acquisition, each tooth was coated with an approximately 0.3 mm thick layer of utility wax to simulate the radiographic appearance of the periodontal space and placed into an empty mandibular anterior socket of a partially edentulous dry human mandible. The mandible was placed into a polystyrene box filled with water prior to the CBCT examination to simulate soft-tissue attenuation and scattering. The CBCT images were obtained on an i-CAT unit (i-CAT Next Generation, Imaging Sciences International, Hatfield, PA) according to three protocols: (I) half scan (180°), 0.40 mm voxel size; (II) full scan (360°), 0.40 mm voxel size; and (III) full scan (360°), 0.125 mm voxel size. The 300 resultant CBCT DICOM volumes were imported into InVivo software (InVivo5, Anatomage, San Jose, CA) for evaluation by three blinded, previously calibrated observers using a five-point confidence rating scale. Cohen’s kappa was used to calculate observers’ agreement. The diagnostic values of sensitivity (Sn), specificity (Sp) and accuracy (Ac) were performed by pooling observer responses for every image modality. Receiver operating characteristic (ROC) were built and the areas under the curve (AUC) were calculated. The Sn, Sp and Ac values were compared by Cochran’s Q test. The AUC values were compared by Mann-Whitney U test. Results: The observers’ agreement ranged from 0.63 to 0.71, which was interpreted as a substantial agreement. Protocol III (0.125 mm voxel size) displayed the highest Sn (81.63 %), Ac (80.67%) and AUC (0.807). There were statistically significant differences between protocol III and the other two protocols (p < 0.001). The specificity of protocol I (84.97 %) was greater than that of protocols II (69.93 %) and III (79.74 %); however statistically significant difference was only found between protocols I and II (p = 0.005). Conclusion: Although there was no difference in accuracy between the degrees of rotation (half and full scan) within the same voxel size (0.4 mm), there was a considerable difference between those and the smallest voxel size (0.125 mm). In fact, it may be suggested that a more dedicated, high resolution scan should be acquired when one intends to investigate the early stage of external root resorption during orthodontic treatment.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22316号 / 医博第4557号 / 新制||医||1040(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 溝脇 尚志, 教授 松田 秀一, 教授 安達 泰治 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Articular cartilage is a highly organized, anisotropic tissue lining the ends of bones within synovial joints. Composed primarily of water, collagens, proteoglycans and chondrocytes which synergistically give rise to the tissue's mechanical and tribological properties. Fluid pressurization and resistance to fluid flow within the porous extracellular matrix of cartilage, coupled with the low hydraulic permeability of the tissue endow the tissue with a viscoelastic response to loading and aid to reduce the coefficient of friction between articulating surfaces, with the pressurized fluid supporting 95% of applied loads. Experiencing millions of articulations throughout an average lifetime, articular cartilage possesses distinct biotribological properties. These require effective lubrication, mediated by the synergistic interaction between fluid and boundary lubricants, to provide a low coefficient of friction and prevent wear at the cartilage surface. Osteoarthritis is the progressive deterioration of articular cartilage and synovial joint structure and function, leading to softer and wear prone tissue on account of altered biochemical composition of the extracellular matrix. Plain radiography remains the most accessible tool and the current standard of care to visualize musculoskeletal diseases and injuries (e.g., osteoarthritis), but cannot directly visualize soft tissues or cartilage, and diagnoses are based solely on boney changes, which occur in the later stages of the disease. Coupled with no way to quantitatively assess tissue health prior to irreversible deterioration, there remains no cure for osteoarthritis. Integral to OA pathology are concomitant changes in the biochemical composition of synovial fluid that result in deterioration of rheological properties, contributing to increased cartilage wear. To address both the lack of quantitative diagnosis methods and lack of chondroprotective therapies, this dissertation presents a dual faceted approach to quantitatively image articular cartilage health, coupled with lubrication strategies to improve cartilage lubrication, and preserve cartilage tissue. This dissertation describes the synthesis of tantalum oxide nanoparticles of varying surface charges for use as contrast agents for rapid, minimally invasive, non-destructive, and quantitative contrast-enhanced computed tomography to assess both the biochemical content and biomechanical integrity of articular cartilage. Ex vivo contrast enhanced computed tomography attenuation using the nanoparticle contrast agent reveals correlations between attenuation and the mechanical and biochemical properties of the tissue. The lubrication strategy described within this dissertation involves introducing a rolling ball element between two surfaces to reduce friction. In this strategy, either single, globular macromolecules or nanoparticles are employed as ball bearings between articulating surfaces to reduce friction when asperities on the surfaces are in direct contact. Rheological characterization and construction of classical Stribeck curves using the lubricant formulations reveal that introducing the rolling element reduces the coefficient of friction during boundary lubrication, while leaving the rheological properties of the base fluid intact. Ex vivo cartilage mechanical testing involving shear deformation under varying speeds and loads reveal improved biotribological performance compared to pure synovial fluid or saline.

A large proportion of dogs undergoing computed tomography are anaesthetised and receive concurrent supplementary oxygen. Both factors promote the development of pulmonary atelectasis, which may mask or mimic lung pathology and compromise image quality, which is of concern to the radiologist. The aim of the study was firstly to determine whether significant atelectasis would develop using a commonly employed anaesthetic protocol in a typical hospital setting, especially where dogs may have been anaesthetised in lateral recumbency prior to scanning. Secondly, to determine whether a change in body position to sternal recumbency would be sufficient to resolve atelectasis. Six healthy adult Beagles were anaesthetised in sternal recumbency and using a breath-hold technique, baseline helical transverse thoracic images were acquired. Dogs were then placed in either right or left lateral recumbency for 30 minutes, with scans performed at predetermined lung lobe locations and time intervals. Dogs were then repositioned in sternal recumbency for a further 20 minutes, with similar scans performed. The study was repeated two weeks later in the opposite lateral recumbency. Changes in Hounsfield units and cross-sectional area of all lung lobes were measured. Lateral recumbency did not result in true atelectasis in healthy Beagles of normal body condition. Infrequently, patchy increased attenuation, which failed to resolve completely during sternal recumbency, was visualised in the left cranial lobe during left lateral recumbency. The degree of attenuation changes in healthy Beagles was minimal, and thus if dogs were anaesthetised in lateral recumbency prior to computed tomography, this should not preclude scanning. / Dissertation (MMedVet)--University of Pretoria, 2016. / Companion Animal Clinical Studies / MMedVet / Unrestricted

Introduction: Magnetic resonance (MR) represents still the gold standard in myocardial imaging. There are some studies suggesting that the computed tomography (CT) might be a valid alternative for some patients (especially the ones who are unable to undergo MR). Aims: We had two aims. Aim number 1: To evaluate the ability of CT in the evaluation of delayed contrast enhancement (DCE) in patients with dilated cardiomyopathy. Aim number 2: To assess the possibilities of CT originally performed for a different indication in myocardial tissue characterization. Methods: Part 1: We prospectively enrolled 17 patients with dilated cardiomyopathy. All the patients underwent both cardiac CT and cardiac MR. We compared the findings of DCE on CT with the findings of DCE on MR. Part 2: We retrospectively evaluated 96 patients who underwent both CT for any indication and cardiac MR. We compared the findings of a hypodense area in the myocardium with the findings of DCE on MR. Results: Part 1: CT detected DCE in 3 patients and MR detected DCE in 6 patients. The agreement between both modalities was in v 82% cases (kappa 0.56). The sensitivity and specificity of CT were 50% and 100%, respectively and the positive predictive value was 100%. In patients with positive findings on CT, the localization of DCE was almost...

Die moderne multimodale Computertomografie (CT) beinhaltet das Schichtröntgen des Gehirns (native CT), die Darstellung der hirnversorgenden Arterien (CT-Angiografie) und die Messung der Hirndurchblutung (CT-Perfusion). Mit Hilfe dieser Untersuchungstechnik kann bei Patienten mit akutem Schlaganfall rasch die Ursache der plötzlich eingesetzten Symptome beleuchtet werden: Liegt eine Gefäßobstruktion oder eine Blutung in das Gehirn vor? Wie ausgedehnt ist die Durchblutungsstörung und wie viel Hirngewebe ist bereits beschädigt bzw. vom Untergang bedroht? Anhand dieser Informationen kann sofort eine spezifische Therapie eingeleitet werden, die es ermöglicht, die Patienten vor dauerhafter schwerer Behinderung zu bewahren bzw. die Prognose schon früh abzuschätzen. / Computed tomography (CT), including CT perfusion imaging and CT angiography, has the capacity to assess stroke pathology on a functional and morphological level and can thus provide important information about patients with acute stroke. It excludes brain haemorrhage, assesses the extent of perfusion deficit, the extent of ischemic damage, and the site and type of arterial obstruction. Ischemic brain tissue below the blood flow level of structural integrity takes up water immediately and causes a decrease in x-ray attenuation. Computed tomography thus has the specific advantage of being able to identify the brain tissue which is irreversibly injured. If CT can exclude major ischemic damage in acute stroke patients, reperfusion strategies may rescue brain function and prevent disability.

Indiana University-Purdue University Indianapolis (IUPUI) / Raloxifene is an FDA-approved selective estrogen receptor modulator (SERM) that improves tissue quality by binding to collagen and increasing the bound water content in the bone matrix in a cell-independent manner. In this thesis, active tissue formation was induced by non-invasive external tibial loading in female mice and combined with raloxifene treatment to assess their combined effect on bone morphology and mechanical properties. Thermoregulation is an important factor that could have physiological consequences on research outcomes, and was introduced as an additional experimental factor in this study. We hypothesized that by removing the mild cold stress under which normal lab animals are housed, a metabolic boost would allow for further architectural and mechanical improvements as a result of the combination of tibial loading and raloxifene treatment. Ten week old female C57BL/6J mice were treated with raloxifene, underwent tibial loading to a strain level of 2050µε and were housed in thermoneutral conditions (32°C) for 6 weeks. We investigated bone morphology through microcomputed tomography (µCT) and mechanical properties via four-point bending and fracture toughness testing. Results indicated a combined improvement by external loading and raloxifene on geometry, particularly in the cancellous region of the bone, and also in bone mechanics leading to greater improvements than either treatment individually. Temperature did not have a robust impact on either bone architecture or mechanical integrity.

Learning to identify anomalies in x-ray images is a time consuming and difficult task. Manyhours of looking at similar images to familiarize oneself with the images can feel daunting andunmotivating. This is why a game application where the user, in a challenging environment, canlearn while being adequately stimulated.In this thesis, a game for this exact reason is created, with the aim being to teach anatomy tomedical students in a stimulating fashion. The game is made in the programming languagePython, which uses libraries supporting the DICOM-format, which is widely used in the medicalfield. By combining a score system with a time limit, the user can challenge themselves and seeconcrete improvement by playing the game.The goal of this thesis is to prepare medical students for their future profession as a doctor,training them to easily detect anomalies in the human body. A small test is conducted to test thegame and confirm that it improves the user’s ability to identify anatomical structures. The resultis then presented along with proposed improvements and alternative approaches.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第24473号 / 医博第4915号 / 新制||医||1062(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 溝脇 尚志, 教授 黒田 知宏, 教授 花川 隆 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM