The goal of this study was to develop and validate a system for the telemetric measurement of in vivo compressive intervertebral loads in the sheep, and to measure these loads in a variety of activities. / A miniature load cell and radio transmitter were implanted in the L3--L4 space of the spine. A total of four sheep were operated on; one was sacrificed five days after surgery, due to failure of the transmitter, and another was sacrificed after failing to ambulate for two weeks after surgery. The other two animals (average mass 67 kg) were kept for five weeks, during which a range of activities were performed, including standing, lying prone, walking/trotting, and jumping. / Results for a range of activities were as follows: in walking at 1.5 m/s, average maximum and minimum loads were 461 N and 256 N, respectively; in walking at 2m/s, average maximum and minimum loads were 684 N and 303 N, respectively; in standing, loads averaged 161 N; and in lying prone, loads averaged 212 N. The highest loads were recorded in jumping, where the peak load was 1290 N. / The results of this study demonstrate for the first time, to our knowledge, the magnitude of in vivo axial loads in the sheep lumbar spine. These findings have implications for the evaluation of studies which employ the sheep model to test spinal implants. As treatment methods for disc degeneration progress from the spacer and fusion approach to more sophisticated prostheses and tissue engineered disc replacements which preserve segmental mobility, such data will become even more important to the design, animal testing, and evaluation of implants.

Brain image segmentation is an active research in computer image analysis. The challenge lies in the fact that the brain anatomy is not identical for all normal subjects let alone subjects with abnormal tissue. / In this thesis, we explain the research we have implemented to extract the brain from T1-weighted MRI images, and then segment the brain into the three prominent compartments (i.e. the cerebellum and the two hemispheres of the cerebrum). The brain extraction is implemented using morphological operations after thresholding. The brain segmentation, however, is implemented in two separate steps. The first step segments the two hemispheres by approximating the midsagittal surface using mainly Radon transform. The second step segments the cerebellum using an atlas-based contour as an initial contour for the gradient vector flow active contour algorithm. / Validation tests have been performed for the brain extraction and cerebellum segmentation methods.

Thesis (Ph.D.)--Lehigh University, 2007. / Adviser: Terrance Boult.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6638. Adviser: Yi Lu. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6373. Adviser: Stephen G. Sligar. Includes bibliographical references (leaves 142-166). Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6252. Adviser: William W. Mantulin. Includes bibliographical references (leaves 206-220). Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3889. Adviser: Thomas S. Huang. Includes bibliographical references (leaves 126-133) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3643. Adviser: Robert B. Gennis. Includes bibliographical references (leaves 103-109) Available on microfilm from Pro Quest Information and Learning.

The rules and mechanical forces governing cell motility and interactions with the extracellular matrix of a tissue are often critical for understanding the mechanisms by which breast cancer is able to spread through the breast tissue and eventually metastasize. Ex vivo experimentation has demonstrated the the formation of long collagen fibers through collagen gels between the cancerous mammary acini responsible for milk production, providing a fiber scaffolding along which cancer cells can disorganize. We present a minimal mechanical model that serves as a potential explanation for the formation of these collagen fibers and the resultant motion. Our working hypothesis is that cancerous cells induce this fiber formation by pulling on the gel and taking advantage of the specific mechanical properties of collagen. To model this system, we present a hybrid method where we employ a new Eulerian, fixed grid simulation known as the Reference Map Method to model the collagen as a nonlinear viscoelastic material coupled with a multi-agent model to describe individual cancer cells. We find that these phenomena can be explained two simple ideas: cells pull collagen radially inwards and move towards the tension gradient of the collagen gel, while being exposed to standard adhesive and collision forces. From a computational perspective, we hope that our work can serve as a generalizable framework for future theoretical studies of the mechanical interactions between a large number of cells and a dynamic environment.

Because snowboarders are known to injure their ankles more often than alpine skiers, it has been postulated that stiffer snowboard boots would provide better protection to the ankle ligaments than current soft boots do. To test this hypothesis, we have measured the kinematics of the feet and lower legs of five snowboarders riding down a course of 10 gates on a ski hill using an electromagnetic motion tracking system. Results were obtained with each snowboarder wearing soft boots and stiffer step-in boots. The measurements were expressed in anatomically relevant rotations of the ankle joint complex. Two models were developed to predict ligament strains from rotations of the ankle joint complex: (1) a statistical model using published ligament strain measured on cadaver specimens at various combinations of ankle rotations as an interpolation and extrapolation table to predict strains in two ankle ligaments at the rotations measured during the snowboarding trials; (2) a personalized 2-degrees-of-freedom kinematic model of the ankle joint complex, based on the Denavit-Hartenberg formulation of serial-link manipulators, to predict strains in flue ankle ligaments from the relative position of the shank and foot. The experimental results showed that the left and right ankles are asymmetrically rotated, mostly in dorsiflexion, eversion and external rotation. Compared to step-in boots and bindings, soft boots and strap bindings allowed more rotation of the ankle joint complex and more strain in the anterior talofibular ligament, according to the statistical model. The kinematic model was not sensitive enough to detect differences in ligament strains between the 2 types of equipment. A functional determination of the axes of rotation of the talocrural and subtalar joints could further improve the predictions of this model. This is the first known study to document experimentally the kinematics of snowboarding. It generally confirms the expectation that softer boats allow significantly wider ranges of ankle rotation and ligament strain.