UBC Theses and Dissertations

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UBC Theses and Dissertations

Development of a desktop high-resolution MRI for microflow visualization Sahebjavaher, Ramin


Research in lab-on-a-chip (LOC) technology involving microfluidics is a growing field aiming at the development of miniaturized biomedical systems with rich functionality. In order to design effective LOC microfluidic systems, the flow fields and the fluids inside LOC devices need to be carefully characterized. High-resolution magnetic resonance imaging (MRI) offers a powerful non-intrusive technology for this application. In this thesis, the design and implementation of a prototype for a desktop high-resolution MRI instrument, consisting of a magnet, gradient coils, gradient amplifiers, and radio frequency (RF) electronics, is presented. To reduce the size and cost of this MRI instrument, a permanent magnetic configuration with a magnetic flux density of 0.6 T is designed with off-the-shelf NdFeB permanent magnets. The coils of the triaxial gradient module are developed using a novel lithography technique. This gradient module is capable of generating gradient fields as high as 2.83 T/m with custom made current amplifiers. The radio frequency (RF) probe is integrated with the gradient module and is connected to the RF electronics which are made using off-the-shelf components. Pulse sequences and signal processing for acquiring static images and velocity profiles are described. The performance of this instrument in terms of static and dynamic image resolution are presented. As a preliminary test, the velocity profile of water flowing inside a small tube was measured with a nominal resolution of 40 μm. The instrument is designed for a static resolution of better than 30 μm and a velocity resolution better than 50 μm/s. Improvements to the current instrument in addition to theoretical limitations are also detailed.

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