Table of FiguresAbstractProblem MotivationBackgroundDesign SpecificationsCommon Coil DesignsProduct DevelopmentSimulationValidation of ComputationsFuture WorkReferencesAppendix A – Product Design SpecificationsAppendix B – Biot-Savart ScriptUNIVERSITY OF WISCONSIN – MADISONDEPARTMENT OF BIOMEDICAL ENGINEERINGBME 200/300 – DESIGNMRI Gradient CoilsMid-Semester ReportNeal Haas - BSACPeter Kleinschmidt – LeaderAnne Loevinger - CommunicatorLuisa Meyer - BWIG10/20/2008ContentsTable of Figures............................................................................................................................................2Abstract......................................................................................................................................................3Problem Motivation...................................................................................................................................3Background..................................................................................................................................................5Design Specifications...................................................................................................................................6Common Coil Designs..................................................................................................................................7Product Development..................................................................................................................................8Simulation................................................................................................................................................9Validation of Computations...................................................................................................................10Future Work...............................................................................................................................................11References.................................................................................................................................................12Appendix A – Product Design Specifications..............................................................................................13Appendix B – Biot-Savart Script.................................................................................................................15Table of FiguresFigure 1 – Coordinate system for the MRI...................................................................................................1Figure 2 – The Helmholtz Coil Pair...............................................................................................................1Figure 3 – The Magnetic Field Created by Helmholtz Coil Pair.....................................................................1Figure 4 – The Maxwell Coil Pair and Direction of Current Flow..................................................................1Figure 5 – The Golay Coil Pairs.....................................................................................................................1Figure 6 – Preliminary Design concept for probe stand...............................................................................1Figure 7 – Final design of Probe stand.........................................................................................................12AbstractAs part of a broader goal to develop novel applications of Magnetic Resonance Imaging (MRI), a low-cost and modular MRI system is currently being developed. One component of this project is the design, construction and testing of gradient coils to function within the system. In addition to background on MRI, several common gradient coil designs are presented within this report, and serve as a basis for development. A simulation script has been developed to approximate magnetic field strengths produced by a given coil design. This will aid in formulating a coil design that produces a magnetic field that varies linearly along its axis. Finally, designs for a testing environment have been developed to aid in the design of the coils, as well as to validate the simulations. Future work will include construction of the testing apparatuses, validation of the simulation script, and preliminary construction and testing of one set of gradient coils.Problem MotivationMagnetic Resonance Imaging (MRI) is a non-invasive medical imaging technique that creates cross-sectional images of the body. It mainly functions as a tool to help physicians diagnose medical conditions. By taking advantage of the nuclear spin inherent in protons and influencing them with a powerful magnetic field, MRIs can align the magnetic poles of all protons in a specimen. After alignment, it creates images with the aid of radiofrequency amplifiers, data acquisition units, and computers. Additionally, MRIs use gradient coils as a way to distinguish points in three-space.A complete Magnetic Resonance Imaging system cannot always provide medical professionals with the detailed, potentially life-saving information that they desire. It would be most advantageous to be able to use Magnetic Resonance (MR) technology to address more specific problems in the medical field. For example, it would be useful to be able to image heart chambers or other vital parts of the body in real time and from multiple angles, all with a greater image quality than provided by a traditional MRI system.In order to accomplish this goal, MRI probe designs have been developed. The goal for the probes is to be able to use them for MR guidance. These probes, when used, would be guided to the specific point of interest on a patient and then oriented to a satisfactory position where the doctor could proceed with the imaging. This method would also be easier on a patient sinceunlike in a full MRI system, multiple images would not require the patient to be repositioned multiple times. Theoretically, the probes would produce a better, more useful image to doctors.3It has been implied by the clients that the primary use for the probes would be to observe parts of the circulatory system, particularly heart chambers. Before being able to implement the probes in any kind of medical setting, they need to be validated in some fashion. One option for validation involves testing the reliability of the probesusing a large MRI system. This method
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