O objetivo do presente estudo foi comparar a sensibilidade e acuidade das imagens obtidas por meio de tomografia computadorizada de feixe cônico (TCFC) com equipamentos com diferentes especificações técnicas, durante o tratamento endodôntico, tendo a microtomografia computadorizada como padrão de referência. Molares inferiores (n=14), com presença de istmo na raiz mesial, foram escaneados por microCT e por 3 diferentes tipos de TCFC, (1) Accuitomo (ACC), (2) NewTom 5G (N5G) e (3) NewTom VGi evo (NEVO), durante as 3 diferentes fases do tratamento: (1) diagnóstico e anatomia do sistema de canais radiculares (SCR), (2) pós preparo biomecânico e (3) pós obturação. Para a padronização das imagens obtidas com os diferentes aparelhos utilizou-se o programa MeVisLab. As imagens obtidas pelos quatro sistemas de imagens foram avaliadas quantitativamente pelos parâmetros bidimensionais de área, perímetro, circularidade e diâmetros maior e menor; e qualitativamente, por 2 examinadores calibrados, por meio de atribuição de escores em relação às fases do tratamento endodôntico: (1) classificação da morfologia do sistema de canais radiculares (SCR) segundo Vertucci (1984) e classificação de istmos segundo Hsu; Kim (1997); (2) presença ou ausência de debris no SCR e nas áreas de istmos e presença de perfurações radiculares e (3) qualidade da obturação no SCR e nas áreas de istmos. Os dados qualitativos foram avaliados estatisticamente por meio do teste Kappa e os quantitativos por análise de variância ANOVA e teste de Tukey, a concordância entre os dados foi verificada pelo coeficiente de correlação intercalasse (ICC) e regressão linear simples. Na fase inicial, houve concordância moderada (k=0,49) e substancial (k=0,63) entre o microCT e os TCFCs. Os TCFCs avaliados não apresentaram acuidade para a classificação dos istmos tipos II e III. Houve reprodutibilidade satisfatória entre microCT e TCFC apresentados pelos valores de perímetro, circularidade, diâmetros maior e menor (0,410,74), sendo esses valores menores para circularidade (0,410,42). O diagnóstico de debris no canal radicular e no istmo foi dificultado nas imagens do ACC (42,9%), N5G (40,0%), NEVO (40%), não mostrando concordância entre o microCT e os TCFCs (0,050,12). Após o preparo biomecânico 2,4% a 4,8% das imagens dos TCFCs demonstraram a presença de perfuração que não existia no microCT. Todos os parâmetros quantitativos analisados apresentaram reprodutibilidade excelente ou satisfatória entre o microCT e os TCFCs (0,600,76). Na avaliação da qualidade da obturação, foi possível o diagnóstico do istmo parcialmente preenchido em torno de 2,9% a 8,8% das imagens obtidas nos TCFCs quando comparados ao microCT em que foi possível o diagnóstico em torno de 26,5% das imagens, levando a uma falta de concordância entre microCT x ACC e uma concordância pobre entre microCT x 5G e microCT X NEVO. Os parâmetros, área, perímetro, diâmetro maior e diâmetro menor apresentaram concordância excelente, e as medidas da circularidade foram satisfatória, limitando a nitidez do material obturador. Os TCFCs fornecem subsídios para o diagnóstico e planejamento do tratamento endodôntico, porém é importante conhecer seus diferentes protocolos e limitações para atingir melhores resultados com menor risco e dano para o paciente / The aim of this study compared the sensitivity and acuity of the images obtained by cone beam computed tomography (CBCT) with equipment with different technical specifications during endodontic treatment, with microCT. Fourteen lower molars were evaluated, with the presence of isthmus in the mesial root. The samples were scanned by microCT and 3 different types of CBCT, (1) Accuitomo, (2) NewTom 5G and (3) NewTom VGi evo, during of the three stages of endodontic treatment, (1) initial, (2) post biomechanical preparation and (3) post-obturation. MeVisLab software was used for registration for all images. The images were analysed quantitatively by the two-dimensional parameters of area, perimeter, roudness and major and minor diameters; and qualitatively, by 2 calibrated examiners, through the assignment of choices regarding the phases of the endodontic treatment: (1) classification of root canal system (SCR) according to Vertucci (1984) and classification of isthmus according to Hsu; Kim (1997); (2) presence or absence of non-SCR debris and areas of isthmus and presence of root perforations and (3) quality of non-SCR obturation and in the isthmus areas.The qualitative data were evaluated statistically by means of the Kappa test and the quantitative variables by ANOVA and Tukey test, the agreement between the data was verified by the interclass correlation coefficient (ICC) and simple linear regression. In the initial phase, there was moderate agreement (k = 0.49) and substantial agreement (k = 0.63) between the microCT and the CBCTs. All CBCTs evaluated were not accurate for the classification of the isthmus types II and III. There was a satisfactory reproducibility between microCT and CBCT presented by the values of perimeter, roundness, major and minor diameters (0.41 0.74), lowest values for circularity (0.41 0.42). The assessment in the images of biomechanical preparation did not allow diagnosis of debris in the root canal and in the isthmus of ACC (42.9%), N5G (40.0%), NEVO (40%) and the results did not find agreement between microCT and the TCFCs (0.05 0.12). Perforations was showed in 2.4% to 4.8% the images of CBCT but not reported on microCT. The data of area, perimeter, major a minor diameter and roundness showed excellent or satisfactory reproducibility between the microCT and the CBCT (0.60 0.76). In the evaluation of the quality of the obturation, the images of the TCFC with the partially filled isthmus presented a value of 2.9% for the ACC and 8.8% for the N5G and NEVO, in this way, they did not agree the value showed in the microCT (26.5%), leading to a lack of agreement between microCT x ACC and poor agreement between microCT x 5G and microCT X NEVO. The parameters, area, perimeter, major and minor diameter presented excellent agreement, but the roundness measurements were satisfactory, making the obturator material clearer. The CBCTs provide subsidies for the diagnosis endodontic treatment, but it is important to know its different protocols and limitations to achieve better results with less risk and harm to the patient

In the area of translational research, stent developers consult pathologists to obtain the best and most complete amount of data from implanted test devices in the most efficient manner. Through the use of micron-scale computed tomography along with post-fixation staining techniques in this study, full volumes of previously implanted stents have been analyzed in-situ in a non-destructive manner. The increased soft tissue contrast imparted by metal-containing stains allowed for a qualitative analysis of the vessel’s response to the implant with greater sensitivity and specificity while reducing beam-hardening artifact from stent struts. The developed staining techniques included iodine-potassium iodide, phosphomolybdic acid, and phosphotungstic acid, all of which bind to soft tissue and improve image quality through their ability to attenuate high energy X-rays. With these stains, the overall soft tissue contrast increased by up to 85 percent and contrast between medial and neointimal layers of the vessel increased by up to 22 percent. Beam hardening artifact was also reduced by up to 38 percent after staining. Acquiring data from the entirety of the stent and the surrounding tissue increased the quality of stent analysis in multiple ways. The three dimensional data enabled a comprehensive analysis of stent performance, lending information such as neointimal hyperplasia, percent stenosis, delineation of vessel wall layers, stent apposition, and stent fractures. By providing morphological data about stent deployment and host response, this method circumvents the need to make the more traditional histology slides for a morphometric analysis. These same data may also be applied to target regions of interest to ensure histology slides are cut from the optimal locations for a more in-depth analysis. The agents involved in such techniques are readily available in most pathology laboratories, are safe to work with, and allow for rapid processing of tissue. The ability to forego histology altogether or to highly focus what histology is performed on a vessel has the potential to hasten the development process of any coronary stent.

Trap-jaw ants are characterized by high-speed mandibles used for prey capture and defense. Power-amplified mandibles have independently evolved at least four times among ants, with each lineage using different structures as a latch, spring and trigger. We examined two species from the genus Myrmoteras (subfamily Formicinae), whose morphology is unique among trap-jaw ant lineages, and describe the performance characteristics, spring-loading mechanism and neuronal control of Myrmoteras strikes. Like other trap-jaw ants, Myrmoteras latch their jaws open while the large closer muscle loads potential energy in a spring. The latch differs from other lineages and is likely formed by the co-contraction of the mandible opener and closer muscles. The cuticle of the posterior margin of the head serves as a spring, and is deformed by approximately 6% prior to a strike. The mandibles are likely unlatched by a subgroup of closer muscle fibers with particularly short sarcomeres. These fast fibers are controlled by two large motor neurons whose dendrites overlap with terminals of large sensory neurons originating from labral trigger hairs. Upon stimulation of the trigger hairs, the mandibles shut in as little as 0.5 ms and at peak velocities that are comparable with other trap-jaw ants, but with much slower acceleration. The estimated power output of the mandible strike (21 kW kg(-1)) confirms that Myrmoteras jaws are indeed power amplified. However, the power output of Myrmoteras mandibles is significantly lower than distantly related trap-jaw ants using different spring-loading mechanisms, indicating a relationship between power-amplification mechanism and performance.

Thesis advisor: Sarah K. McMenamin / Thesis advisor: Vicki Losick / Proper bone development requires coordination and timing of specific morphogenetic events, and relative shifts in these temporal processes can change morphology. Thyroid hormone (TH) plays an important role in regulating the timing of vertebrate skeletogenesis, and the hormone induces the profound skeletal shape changes that occur during amphibian metamorphosis. Like humans, zebrafish do not undergo an ecological metamorphosis; yet TH is essential in coordinating postembryonic developmental processes. In particular, several elements of the craniofacial skeleton that continue to ossify and remodel during later stages of development are sensitive to TH titer. My aims focus on the role of TH in regulating skeletal growth and shape changes in zebrafish. To examine changes in the entire zebrafish skeleton during normal postembryonic development, I generated a skeletal reference of microCT scans of zebrafish ranging from early juvenile through adult stages (Chapter 2). After defining the normal changes that wild-type zebrafish undergo, I hypothesized that TH coordinates the developmental shape changes and determined the role of TH in stimulating developmental shape change in zebrafish skulls and its effects on skeletogenic cell populations (Chapter 3). Finally, I investigated whether phenotypes induced by altered TH levels mirror some of the evolutionary diversity seen across Danioninae craniofacial skeletons (Chapter 4). My research elucidates the role of TH in the regulation of bone growth and shape change in a vertebrate system and provides new insights into the natural craniofacial diversity of Danioninae. / Thesis (PhD) — Boston College, 2024. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Biology.

La pulpe dentaire est un tissu connectif innervé et vascularisé, contenu dans une structure minéralisée inextensible formée par l’émail, la dentine et le cément. Ce tissu assure l’homéostasie et la sensibilité de la dent. Il est sujet à des lésions sévères faisant suite à une carie ou à un traumatisme. La thérapeutique conventionnelle préconisée alors est le traitement endodontique, qui consiste en l’exérèse de la totalité du tissu pulpaire et le comblement de l’espace évidé par un matériau synthétique bioinerte. Malgré les résultats cliniques satisfaisants, cette thérapeutique induit une fragilisation de la dent et une plus grande susceptibilité aux infections, qui peuvent conduire à terme à la perte de la dent. En se basant sur la présence de cellules souches mésenchymateuses dans la pulpe dentaire, des stratégies de régénération alternatives au traitement endodontique traditionnel sont à l’étude, afin de permettre le maintien des fonctions de nutrition et de sensibilité de la pulpe, garantes de la pérennité de la dent sur l’arcade. Elles s’inscrivent dans deux approches: la régénération de novo, en cas de nécrose du tissu pulpaire et la régénération partielle, lorsque seul le tissu pulpaire endommagé est éliminé et régénéré. Nos travaux portent sur la faisabilité de cette dernière approche dans un modèle préclinique. En effet, dans la perspective d’un transfert vers la clinique humaine, des modèles chez le gros animal doivent être développés afin de tester la faisabilité et le succès de cette thérapie, dans des conditions proches de la clinique. Du fait de ses similitudes avec l’homme en termes d’anatomie et de physiologie, le miniporc représente un modèle de choix pour les études précliniques d’ingénierie pulpaire. L’objectif principal de cette étude est de tester la faisabilité de la régénération pulpaire partielle, en implantant des cellules pulpaires porcines (pDPCs) contenues des hydrogels injectables dans des défauts pulpaires artificiellement créés chez le miniporc. Au cours ce travail, différentes techniques d’imagerie d’évaluation du processus de régénération ont été développées. En particulier, un protocole d’angiographie tridimensionnelle in- pour la visualisation du réseau vasculaire pulpaire a été mise au point. Par ailleurs, en utilisant des paramètres morphométriques spécifiques, initialement développés pour caractériser l’os, une analyse tridimentionnelle par micro-CT des tissus minéralisés de réparation a été élaborée. En appliquant un “split mouth model”, les hydrogels injectables ensemencés ou non par des pDPCs ont été implantés dans des molaires et des prémolaires, après amputation de la pulpe camérale. À 21 jours après la chirurgie, les analyses d’imagerie, d’histologie et d’immunologie ont mis en évidence, qu’indépendamment de la présence des pDPCs, l’implantation des hydrogels a induit la formation d’un pont d’ostéodentine. La caractérisation morphométrique tridimensionnelle a montré que la microarchitecture de ce pont différait largement de la dentine native. De plus, en présence des pDPCs, le processus de réparation était modifié, avec une moins bonne étanchéité du pont. Au cours de ce travail, une technique de suivi non invasive de la régénération a tenté d’être mise au point. Une angiographie tridimensionnelle par soustraction a été réalisée avant et après la procédure de régénération pulpaire partielle. Si les angiographies ont révélé l’entière vascularisation des mâchoires et des dents à croissance continue, l’apport vasculaire des dents matures traitées, du fait de son faible flux, n’a pas pu être mis en évidence. L’absence de régénération partielle de la pulpe dans les conditions testées souligne l’importance des modèles précliniques pour identifier les facteurs promouvant un environnement favorable à la régénération, dans la perspective d’un transfert vers la clinique humaine. / The dental pulp is a connective tissue, which is highly innervated and vascularized, encapsulated in a mineralized inextensible structure formed by enamel, dentin and cementum, ensuring the homeostasis and sensibility of the tooth. The pulp is often damaged by caries and trauma, resulting in infection or necrosis. In such situations, the routine clinical treatment is a root canal therapy, which consists in the elimination of the affected tissue and filling of the endodontic canal system with bioinert synthetic materials. In spite of satisfactory clinical outcomes, none of the original functions is restored and the lack of sensitivity as well as natural defence may lead to tooth fracture and reinfection. Cell-based pulp regeneration could provide a valid alternative to traditional endodontic treatment of damaged teeth. This strategy focuses, in fact, on the preservation of the healthy pulp tissue and the regeneration of the damaged one, by combining stem cells, scaffolds and growth factors. In case of trauma or carious lesion, as the pulp inflammatory reaction is compartmentalized in first instance, such conservative approach could be indicated. Regarding non-rodent animal model, to our knowledge, only Iohara et al. (2009) reported the achievement of partial pulp regeneration in canine tooth by implantation of subfractions of autologous pulp cells; however, in the perspective of a transfer to the human clinic, larger animal models should be developed to test the feasibility and the success of the therapy mimicking the clinical conditions of pulpotomy. Due to dental anatomical and physiological similarities with human, the minipig constitutes a model of choice for preclinical pulp engineering studies. The aim of this study was to develop a preclinical model of partial dental pulp regeneration in minipig, by implanting a pulp construct, made by self-assembling nano-peptide injectable hydrogel and porcine minipig dental pulp cells (pDPCs), in artificially created pulp defects. Secondarily, in the context of this preclinical model, two different techniques of analysis of the regeneration process have been developed. In particular, an in vivo 3D subtraction angiography has been set for the visualization of dental pulp vascular network. Indeed, further developments of this modality open promising perspectives of its application for the morphometric characterization of angiogenesis process in newly formed dental tissues and bone defects. Moreover, using specific morphometric parameters, initially developed to characterize bone, a micro-CT morphometric analysis of the mineralized reparative tissues, obtained by the partial pulp regeneration protocol, has been elaborated. By split mouth model, pulp constructs made with self-assembling injectable nano-peptide hydrogel with and without porcine dental pulp cells (pDPCs) were implanted, after pulp chamber amputation in premolars and molars. At day 21 after surgery, three-dimensional morphometric characterization, Masson’s trichrome and immunolabeled for DSP and BSP were performed on treated teeth. 3D subtraction angiographies have been performed before and after partial pulp regeneration procedure. Regardless of the presence of pDPCs, the implantation of pulp construct induces the formation of an osteodentin bridge, whose microarchitecture sensibly differs from the native dentin. Furthermore, the presence of pDPCs in the construct slightly impairs this reparative process. The latter was led the remaining pulp cells, instead of the pDPCs in the scaffold. Angiographies could show entire vascularization of jaws and continuously growing teeth but blood supply of treated mature permanent teeth could not be displayed. The failure of partial pulp regeneration cell based strategy, in these near-real clinical conditions, highlights the importance of preclinical models, to identify the factors promoting a favourable regenerative environment, in the perspective of a transfer to the human clinics.

In this work, two innovations were demonstrated for in-situ 3D study of fatigue cracks and their closure as a function of applied load. The first related to improvements in how absorption microtomography is used to study fatigue cracks. The second is a new approach to 3D crack mapping relying on X-ray phase imaging and stereometric approaches. Absorption microtomography was used to determine crack surface positions. Crack opening was measured from absorption microtomography data both before and after crack extension and patterns of opening at several loads were analyzed for both cases. X-ray phase contrast imaging, an alternative approach to absorption microtomography, whose sensitivity to cracks is not strongly affected by the shape of the specimen, was also investigated. Increased sensitivity of phase imaging to cracks, compared to that of the absorption X-ray methods, allowed detecting crack positions up to the crack tip with no load applied to the sample. Stereometry reconstruction based on the phase microradiographs was carried out, and the results were compared with those of absorption microtomography on the same specimen. This study demonstrated that it is possible to reconstruct accurate 3D positions of features inside optically opaque sample by recording several X-ray phase microradiographs.

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.

No description available.

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.

Although mammals are the most commonly utilized laboratory animal, laboratory animal medicine continually seeks to replace them with animals of lower phylogenic classification. Fish are becoming increasingly important as investigators seek alternative animal models for research. Fish can provide an economical and feasible alternative to typical mammalian models; moreover, many fish, which have comparatively short life spans, can easily reproduce in the laboratory. One key area of animal health research in which fish have been underutilized is the field of advanced imaging. Although many images of fish have been captured through the use of computed tomography (CT), radiography, and ultrasonography, these images have been primarily utilized for anatomical study. In addition, fish have never before been studied with positron emission tomography/ computed tomography (PET/CT). My objectives were to determine if these imaging techniques can be used to obtain physiological information from fish, therefore making it more likely that fish can be utilized as replacement animals using these new imaging techniques (CT, PET/CT). I performed two different types of studies to assess the potential application of advanced imaging techniques to fish. In the first experiment, microCT was used to characterize otolith deformity in vitamin C deficient captive-raised red drum and relate the deformity to behavioral and physiological changes. I found that the normal and abnormal fish had statistically significant differences in behavior, cortisol levels, and otolith volume and density. MicroCT assessment of abnormal fish revealed operculum abnormalities, malocclusions, and several types of otolith malformations. Therefore, the affected fish had not only an abnormal skeletal appearance but also significantly abnormal behavior and cortisol responses. In the second experiment, fluorodeoxyglucose-positron emission tomography/ computed tomography (FDG-PET/CT) was used to quantify glucose uptake in select organs prior to carcinogenesis studies in fish. The quantified glucose uptake was compared to published data on humans, mice, and dogs. Rapid, quantifiable glucose uptake was demonstrated, particularly in brain, kidneys, and liver in all imaged fish species. Glucose uptake in the major organ systems of fish was closer to that in humans than uptake in mice or dogs, indicating that fish may serve as an effective alternative animal model for tumor studies using this technology. Other applications for this technique in fish may include metabolism studies and screening for environmental carcinogenesis. I found that both microCT and PET/CT imaging provided useful and meaningful results. In addition, the use of non-invasive scanning allows for re-use of fish, thus reducing the number of animal models used in experiments. These experiments suggest that fish will be good replacement models for mammals using these advanced imaging techniques.