It is well established that bone is capable of adapting to changes in its environment; however, little is known regarding how environmental stimuli, specifically loading, are associated with the internal 3D microarchitecture of cortical bone. The aim of this thesis was to develop a small animal model that can be used to experimentally test hypotheses regarding bone adaptation. High resolution micro-CT was validated and employed as a novel method for the visualization and quantification of rat cortical bone microarchitecture in 3D. The use of this imaging method allowed for the measurement of primary vascular canal orientation in 3D, which had never been achieved before. Using this measure along with an immobilization model for unloading allowed me to test how loading is associated with the orientation of these vascular canals. Normally ambulating rat bones (from 10 female rats) had a canal structure that was 9.9° more longitudinal than their immobilized counterparts. This finding that loading has an effect on primary canal orientation brought to light the need to induce remodeling and therefore, secondary vascular canals, in the rat to increase its novelty as a model for looking at bone adaptation. Remodeling was induced by increasing the calcium demands of female rats, either through a calcium restricted diet (n=2) or pregnancy and lactation coupled with a calcium restricted diet (n=2). Mean cortical thickness for the calcium restricted rats and the pregnant and lactating rats that were on a calcium restricted diet were 622 µm and 419 µm, respectively. The mean BMU count for calcium restricted rats seemed to be higher than that of the pregnant and lactating rats; however, the calcium restricted rats seemed to have a lower BMU density. Once this full-scale study is executed the rat will provide a more representative model for studying human bone adaptation.

No description available.

No description available.

Cortical bone is a dynamic tissue which undergoes adaptive and pathological changes throughout life. An improved understanding of the spatio-temporal process of remodeling holds great promise for improving our understanding of bone development, maintenance and senescence. The use of micro-computed tomography (µCT) on living animals is relatively new and allows the three dimensional quantification of change in trabecular bone microarchitecture over time. The use of in vivo µCT is limited by the radiation dose created by the x-ray beam, with commercially available in vivo systems generally operating in the 10-20 um resolution range and delivering an absorbed dose between 0.5-1 Gy. Because dose scales to the power of four with resolution, in vivo imaging of the cortical canal network, which requires a higher resolution, has not been achieved. I hypothesized that using synchrotron propagation phase contrast µCT, cortical porosity could be imaged in vivo in rats at a dose on the same level as those used currently for trabecular bone analysis. Using the BMIT-BM beamline, I determined the optimal propagation distance and used ion chamber and lithium fluoride crystal thermoluminescent dosimetry to measure the absorbed dose of my in vivo protocol as well as several ex vivo protocols using synchrotron phase contrast µCT at 5 µm, 10 µm, and 11.8 µm and conventional desktop in vivo protocols using commercial µCT systems. Using synchrotron propagation phase contrast µCT, I scanned the forelimb of two adult Sprague-Dawley rats and measured an absorbed dose of 2.53 Gy. Using two commercial µCT system, I measured doses between 1.2-3.6 Gy for protocols at 18µm that are in common use. This thesis represents the first in vivo imaging of rat cortical porosity and demonstrates that an 11.8 µm resolution is enough to visualize cortical porosity in rats, with a dose within the scope of those used for imaging trabecular bone in vivo.

abstract: Craniofacial morphology in primates can vary on the basis of their diet because foods are often disparate in the amount and duration of force required to break them down. Therefore diet has the potential to exercise considerable selective pressure on the morphology of the masticatory system. The zygomatic arch is a known site of relatively high masticatory strain and yet the relationship between arch form and load type is relatively unknown in primates. While the relative position and robusticity of the arch is considered a key indicator of craniofacial adaptations to a mechanically challenging diet, and central to efforts to infer diet in past species, the relationships between morphology and diet type in this feature are not well established. This study tested hypotheses using two diet categorizations: total consumption percent and food material properties (FMPs). The first hypothesis that cortical bone area (CA) and section moduli (bone strength) are positively correlated with masticatory loading tests whether CA and moduli measures were greatest anteriorly and decreased posteriorly along the arch. The results found these measures adhered to this predicted pattern in the majority of taxa. The second hypothesis examines sutural complexity in the zygomaticotemporal suture as a function of dietary loading differences by calculating fractal dimensions as indices of complexity. No predictable pattern was found linking sutural complexity and diet in this primate sample, though hard object consumers possessed the most complex sutures. Lastly, cross-sectional geometric properties were measured to investigate whether bending and torsional resistance and cross-sectional shape are related to differences in masticatory loading. The highest measures of mechanical resistance tracked with areas of greatest strain in the majority of taxa. Cross-sectional shape differences do appear to reflect dietary differences. FMPs were not correlated with cross-sectional variables, however pairwise comparisons suggest taxa that ingest foods of greater stiffness experience relatively larger measures of bending and torsional resistance. The current study reveals that internal and external morphological factors vary across the arch and in conjunction with diet in primates. These findings underscore the importance of incorporating these mechanical differences in models of zygomatic arch mechanical behavior and primate craniofacial biomechanics. / Dissertation/Thesis / Appendix A / Appendix B / Appendix D / Doctoral Dissertation Anthropology 2017

In this thesis a new framework is proposed for obtaining the spongy bone, cortical bone, muscle and adipose tissue from MRI data. The method focuses on the accurate extraction of the edges of the target tissues, which is the main drawback of previous works. In this framework six new methods, as listed in section 1.3, are utilized together for improving the result of the segmentation by detecting the relational position of the tissues, acquiring the best possible contribution from the operator in terms of time and efficiency, forward and backward transfer of the segmented tissues at the seed slice and using the newly proposed Deformable Kernel Fuzzy-C Mean (DKFCM) method for improving the result of segmentation on the edges. This method first limits the searching area for the voxels of the target tissue from the whole data to a small strip around the edges of the target tissue. Then, it applies a very accurate segmentation on the searching area, using a deformable kernel, which is capable of adapting itself with the shape of the edge. Comparing the results of this work with some popular MRI segmentation methods like active contour, watershed, FCM and also some heuristic methods, which are proposed in literature for segmenting the MRI to four tissues, demonstrates the superiority of the proposed method especially on the edges.

No description available.

No description available.

<p>Mechanical instruments, such as saw and bur are commonly used for bone cutting during orthopedics surgeries. These conventional instruments showed good bone removal efficiency. Nonetheless, there are some issues with the use of the mechanical tools, such as ill-placed screws and elevation of tissue temperature, which results in thermal damage to the surrounding tissues. These difficulties accompanied with using mechanical tools led to laser ablation investigations. Lasers, including continues wave (CW) and pulsed, were considered to be a promising tool for bone ablation. When compared to mechanical tools, lasers produce less thermal damage to the surrounding tissues due to their ability to focus on a very small spot, which also produces more precise ablation. Lasers also produce no significant mechanical vibrations within the surrounding tissue and thus less mechanical damage and cracks occur during ablation. Performances of laser ablations are measured by several factors; such as collateral damage, machining time, ablated depth, and ablative precision. In this thesis work, a literature review was conducted with the aim of understanding the bone characteristics that are related to the optical properties of bone, which leads to a better understanding for ablation mechanisms. This helps in a proper choice of laser parameters for a certain tissue ablation, and thus avoiding collateral damage.</p> <p>Some laser parameters (pulse energy, scanning speed, and number of passes) were characterized as a first step towards producing large holes. The effect of each one of these laser parameters on the groove depth was found. The feasibility of the ultrafast laser in creating large scale holes was examined, using two scanning strategies: (i) concentric circles scanning, the largest crater depth measured using this procedure was 3.81 mm, (ii) helical scanning, which was used to reduce the machining time, using this procedure a micropillar was created with 12 passes in just 2.5 minutes.</p> / Master of Applied Science (MASc)

Yes / Physical properties of scaffolds such as nanofibers and aligned structures have been reported to exert profound effects on the growth and differentiation of stem cells due to their homing-effect features and contact guidance. However, the biological function of aligned nanofiber utilized as bone-scaffold has not been rigorously characterized. In the present study, aligned electrospun cellulose/CNCs nanocomposite nanofibers (ECCNNs) loaded with bone morphogenic protein-2 (BMP-2) were used for the first time to investigate (1) in vitro osteogenic differentiation of human mesenchymal stem cells (BMSCs) and (2) in vivo collagen assembly direction and cortical bone regeneration. Aligned ECCNNs scaffolds loaded with BMP-2 possess good biological compatibility. The growth orientation of BMSCs followed the underlying aligned nanofibers morphology, accompanied with increased alizarin red stain, ALP activity and calcium content in vitro while, a rabbit calvaria bone defect model was used in an in vivo study. / This work was supported by Natural Science Foundation of China (NSFC) grants (31500789, 51433006, 51473100, 81870758 and 31871464), Chongqing Yuzhong District science and technology plan project grants (20170124), Chongqing Research Program of Basic Research and Frontier Technology (cstc2018jcyjAX0807, cstc2017jcyjBX0019 and cstc2017jcyjAX0020), Temple University Kornberg School of Dentistry research start-up funds, the RCUK China-UK Science Bridges Program through the Medical Research Council and the Engineering and Physical Sciences Research Council and Program for Innovation Team 1015 Building at Institutions of Higher Education (No. 1016 CXTDG201602006) funded by the Chongqing Municipal 1017 Education Commission of China in 2016