An inexpensive laboratory module to teach principles of NMR/MRI
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We report the details of, and our experience with, a relatively simple and inexpensive teaching laboratory apparatus which demonstrates some of the basic physical phenomena and principles of Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI). Our approach uses two 221 inch Neodymium Iron Boron (NdFeB) permanent magnets in the 0.6 T range, and large cylindrical (5 inch diameter, one inch thick) field-spreading pole pieces made of soft steel, along with a one-half-inch-thick walled soft-steel enclosure. This design trades away field strength for uniformity in order to get a large enough volume (at least a 1 cm cube) of highly-uniform 0.08 T in which the NMR phenomenon is easily observed. While others have demonstrated and/or market more complex and elegant benchtop NMR or MRI systems generally costing several thousands of dollars (e.g. TeachSpin), our goal was to create a simple tool which would be inexpensive enough so that there could be one per lab bench in an imaging course. The magnetic field is also well contained in this design, and not strong enough to represent a significant hazard or nuisance. The component cost (including magnets) for this system is approximately $400 and it can demonstrate Free Induction Decay and Spin Echo. The sample used can be a small container of glycerin. It is assumed that an oscilloscope and a bench power supply are available. This module is was used in the form of a lecture demonstration of the Spin Echo experiment in the Northwestern University Biomedical Engineering course BME 325, Introduction to Medical Imaging, during the Fall 2004 quarter. This course includes undergraduate and graduate students from both ECE and BME majors. We report our experiences and a formal evaluation of the effectiveness of the module.
