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Simulation of Subject Specific Bone Remodeling. (Ph.D. dissertation)

Abastract Conditions of low bone density (e.g., osteoporosis) are major health concerns nowadays. Particularly, vertebral compression fracture is one of the severe conditions that affects the patient's daily functionality and quality of life. The vertebral compression fracture is mainly caused by overloading on weak cancellous bone structures. Thus an effective method that measures the loads on the vertebra and predicts the change of cancellous bone structure under the loads can be very helpful in assisting clinical diagnosis and treatment of low bone density conditions. This study demonstrates a simulation method that can eventually be incorporated with clinical treatment tailored for a particular individual to prevent bone loss and vertebral compression fractures. This method simulates the bone remodeling process with the inputs of initial cancellous bone structure, the stress and strain as a result of mechanical stimulus, and biological factor such as age. To demonstrate the use of the method, this study conducted the simulation of the bone changes under different physical activities. The result of the iterative simulation is an optimized cancellous structure, which can be characterized by a set of bone parameters. The simulation uses optimized algorithms and parallelization of computing to achieve computing effectiveness and cost efficiency. Thus, using the simulation, the cancellous structure can be characterized quantitatively for clinical diagnosis in individual cases, and facilitate informed decisions on a patient's lifestyle for bone health.

3D Organ Modeling (Master's Thesis)

The focus of this project was to develop a tool to reconstruct a 3D geometry from multiple images taken from a single camera. It combines the voxel carving from silhouettes and voxel coloring method in reconstructing a model of the stomach affected by Aortic Aneurysm. The foreground which contains the image of the organ, is separated from the background by calculating an appropriate background model. A voxel model is generated from those images and a triangulated surface model is created using the Marching cube technique.

Virtual reality powered wheelchair simulator

Power wheelchairs (PW/C) offer the means for independent mobility for individuals with severe physical impairments thereby improving their ability to participate in society. The current training methods used to teach an individual to use a PW/C are inefficient, and potentially unsafe. Ideally, a large space is required with different environments to train in. Those users who are new to a PW/C may find it difficult to initially operate the wheelchair since they may not have adequate cognitive and/or physical ability to effectively control the PW/C. The (VRPW/C) simulator presented in this paper may offer an alternative way to train individuals to use a PW/C and provide objective data on the client's ability to successfully operate a PW/C independently. The proposed VRPW/C offers potential benefits over traditional PW/C training methods. For example, the associated virtual environment (VE) can be shaped to meet the skill level of the client, i.e., the VE can be made easier to maneuver through at first, with the difficulty increasing as the client’s ability improves. Additionally, the VRPW/C simulator can provide quantitative data on the client’s performance that can be used to document change and capacity to independently operate a PW/C, e.g., for insurance purposes. The developed VRPW/C system extends past results by providing users with realistic visual, kinesthetic, and vestibular feedback that is highly immersive. The system consists of three main components: (1) a seven degree-offreedom (DOF) Stewart platform (a form of parallel robot) that serves as a motion base capable of providing haptic feedback to a user seated in a manual wheelchair mounted on the motion base that is synchronized with (2) an immersive VE, presented to a user via a stereoscopic head-mounted display (HMD), and navigated using (3) a standard PW/C control device, e.g., a joystick or puff-and-sip.