http://hdl.handle.net/1974/770 Wed, 19 Jun 2013 05:07:33 GMT 2013-06-19T05:07:33Z http://hdl.handle.net/1974/8054 Title: TELEOPERATED MRI‐GUIDED PROSTATE NEEDLE PLACEMENT Authors: Seifabadi, REZA Abstract: Most robotic systems reported for MRI-guided prostate interventions use manual needle insertion, based on a previously acquired image, which requires withdrawing the patient from the scanner multiple times during the procedure. This makes the intervention longer, more expensive and elongating the discomfort to patient and, most importantly, less accurate due to the virtually inevitable motion of the target. As a remedy, automated needle placement methods were proposed, putting human supervision out of the control loop. This thesis presents the development of enabling technologies for human-operated in-room master-slave needle placement under real-time MRI guidance, while the patient is kept in the scanner and having the process of needle placement under continuos control of the physician. The feasibility of teleoperated needle insertion was demonstrated by developing a 1-DOF (degree of freedom) MRI-compatible master-slave system, which was integrated with a 4-DOF robot for transperineal prostate biopsy and brachytherapy. An accuracy study was conducted on a robotic system for MRI-guided prostate needle placement. Different error sources were identified and quantified. This study concluded that errors occurring during needle insertion have the most significant contribution to needle placement error. In order to compensate for these errors, teleoperated needle steering under real-time MRI guidance was proposed. A 2-DOF piezo-actuated MRI-compatible needle steering module was developed and integrated with the aforementioned 4-DOF transperineal robot, yielding a fully actuated 6-DOF (x, y, z, yaw, pitch, roll) robotic platform for MRI-guided prostate interventions. A novel MRI-compatible master robot was also developed to enable teleoperated needle steering inside the MRI room. MRI-compatible controller hardware and software were developed. A novel MRI-compatible force/torque sensor was devised using Fiber Bragg Grating for force measurement in MRI room. Phantom experiments proved the feasibility iii of teleoperated needle steering under real-time MRI guidance. A system was also developed for real-time 3D shape tracking of a bevel-tip needle with Fiber Bragg Grating sensors embedded along the needle shaft. The needle profile was overlaid on the real-time MR image, yielding real time navigation with accuracy better than 0.5 mm. The experimental system is presently being refitted for clinical safety and feasibility trials on real patients. Description: Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2013-05-30 12:26:18.732 Thu, 30 May 2013 04:00:00 GMT http://hdl.handle.net/1974/8054 2013-05-30T04:00:00Z http://hdl.handle.net/1974/8045 Title: Large-eddy simulation of unidirectional turbulent flow over dunes Authors: Omidyeganeh, MOHAMMAD Abstract: We performed large eddy simulation of the flow over a series of two- and three-dimensional dune geometries at laboratory scale using the Lagrangian dynamic eddy-viscosity subgrid-scale model. First, we studied the flow over a standard 2D transverse dune geometry, then bedform three-dimensionality was imposed. Finally, we investigated the turbulent flow over barchan dunes. The results are validated by comparison with simulations and experiments for the 2D dune case, while the results of the 3D dunes are validated qualitatively against experiments. The flow over transverse dunes separates at the dune crest, generating a shear layer that plays a crucial role in the transport of momentum and energy, as well as the generation of coherent structures. Spanwise vortices are generated in the separated shear; as they are advected, they undergo lateral instabilities and develop into horseshoe-like structures and finally reach the surface. The ejection that occurs between the legs of the vortex creates the upwelling and downdrafting events on the free surface known as “boils”. The three-dimensional separation of flow at the crestline alters the distribution of wall pressure, which may cause secondary flow across the stream. The mean flow is characterized by a pair of counter-rotating streamwise vortices, with core radii of the order of the flow depth. Staggering the crestlines alters the secondary motion; two pairs of streamwise vortices appear (a strong one, centred about the lobe, and a weaker one, coming from the previous dune, centred around the saddle). The flow over barchan dunes presents significant differences to that over transverse dunes. The flow near the bed, upstream of the dune, diverges from the centerline plane; the flow close to the centerline plane separates at the crest and reattaches on the bed. Away from the centerline plane and along the horns, flow separation occurs intermittently. The flow in the separation bubble is routed towards the horns and leaves the dune at the tips. Barchan dunes induce two counter-rotating streamwise vortices, along each of the horns, which direct high-momentum fluid toward the symmetry plane and low-momentum fluid near the bed away from the centerline. Description: Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2013-05-27 18:58:48.969 Tue, 28 May 2013 04:00:00 GMT http://hdl.handle.net/1974/8045 2013-05-28T04:00:00Z http://hdl.handle.net/1974/8025 Title: FABRICATION AND STUDY OF AC ELECTRO-OSMOTIC MICROPUMPS Authors: Guo, Xin Abstract: In this thesis, microelectrode arrays of micropumps have been designed, fabricated and characterized for transporting microfluid by AC electro-osmosis (ACEO). In particular, the 3D stepped electrode design which shows superior performance to others in literature is adopted for making micropumps, and the performance of such devices has been studied and explored. A novel fabrication process has also been developed in the work, realizing 3D stepped electrodes on a flexible substrate, which is suitable for biomedical use, for example glaucoma implant. There are three major contributions to ACEO pumping in the work. First, a novel design of 3D “T-shaped” discrete electrode arrays was made using PolyMUMPs® process. The breakthrough of this work was discretizing the continuous 3D stepped electrodes which were commonly seen in the past research. The “T-shaped” electrodes did not only create ACEO flows on the top surfaces of electrodes but also along the side walls between separated electrodes. Secondly, four 3D stepped electrode arrays were designed, fabricated and tested. It was found from the experiment that PolyMUMPs® ACEO electrodes usually required a higher driving voltage than gold electrodes for operation. It was also noticed that a simulation based on the modified model taking into account the surface oxide of electrodes showed a better agreement with the experimental results. It thus demonstrated the possibility that the surface oxide of electrodes had impact on fluidic pumping. This methodology could also be applied to metal electrodes with a native oxide layer such as titanium and aluminum. Thirdly, a prototype of the ACEO pump with 3D stepped electrode arrays was first time realized on a flexible substrate using Kapton polyimide sheets and packaged with PDMS encapsulants. Comprehensive experimental testing was also conducted to evaluate the mechanical properties as well as the pumping performance. The experimental findings indicated that this fabrication process was a promising method to create flexible ACEO pumps that can be used as medical implants and wearable devices. Description: Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2013-05-06 10:57:48.077 Tue, 07 May 2013 04:00:00 GMT http://hdl.handle.net/1974/8025 2013-05-07T04:00:00Z http://hdl.handle.net/1974/7992 Title: Laser Welding of Alumina Ceramic Substrates with Two Fixed Beams Authors: Sedore, Blake Abstract: Laser welding was investigated as a potential joining technology for alumina ceramic substrates. The objective of this study was to develop a method to preheat the ceramic using a single defocused laser beam prior to welding. Engineering ceramics are employed in a variety of systems and environments due to their unique properties. Joining technologies must be developed to facilitate the manufacture of complex or large ceramic components. Laser welding is advantageous as it forms joints rapidly, and does not introduce intermediate materials to form the bond, which can have deleterious effects. The Laser Machining System (LMS) at Queen’s University was adapted for this study. A defocused far-infrared (FIR) laser beam was positioned to overlay a focused near-infrared (NIR) laser beam; the defocused FIR beam preheated the ceramic substrate and the focused NIR beam formed the weld. A finite element model was developed in COMSOL MultiPhysics to simulate the preheating processes and to develop a preheating protocol. The protocol was implemented using the FIR beam and adjusted to achieve preheating temperatures of 1450, 1525, and 1600degC. Welds were performed on 1 mm thick alumina plates using the preheating protocols and NIR beam powers of 25, 50, and 75 W. Weld speed was held constant throughout the study at 0.5 mm/s. The preheating protocols were successful at achieving near-constant preheating temperatures, with standard deviations below 32 degrees. Partially penetrating welds were formed with the NIR beam at 25 W, and fully penetrating welds at 50 and 75 W. Large pores were present in the 25 W and 50 W welds. Minimal porosity was observed in the welds formed at 75 W. All of the welded plates experienced a transverse fracture that extended perpendicular to weld, and a longitudinal fracture extending parallel to the weld. This study shows that a fixed defocused laser beam can successfully preheat alumina substrates to the high temperatures required for welding; however, non-homogenous cooling results in fracture. Increasing the preheating beam diameter or introducing an auxiliary means to provide a controlled cool-down cycle may mitigate these effects. Description: Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2013-04-29 17:59:57.43 Tue, 30 Apr 2013 04:00:00 GMT http://hdl.handle.net/1974/7992 2013-04-30T04:00:00Z