Magnetic resonance imaging (MRI) has established itself as a key diagnostic technique in medical detection and imaging of a variety of cancers. In all MRI systems, a radio frequency coil is used to generate and receive the NMR signal. The design of these coils is important because signal quality required precise control over the shape and homogeneity of the RF magnetic field. One popular design is the so-called """"""""birdcage resonator"""""""", a cylindrically symmetric cage structure which exhibits high magnetic field homogeneity and signal-noise ratio. It is the purpose of the present proposal to conduct theoretical, computational, and experimental purpose of the present proposal to conduct theoretical, computational, and experimental studies of the rf birdcage coil. These studies will consist of: a) theoretical analysis of the electrical behavior of the coil including mutual inductance, magnetic shielding, and the effects of coil coupling and sample loading; b) computation of the fields radiated by the structure, their distribution and homogeneity, and dependence on frequency, number of columns, and other coil parameters; c) experimental measurements on a variety of fabricated coils to validate the accuracy of theory concerning effects of coil geometry, shielding, coil coupling and loading including human and animal loads as well as phantoms. Previous theoretical work has resulted in a general approach to coil analysis providing understanding of key coil parameters under unloaded conditions with some mutually inductive coupling. A three-dimensional fields computer simulation, which uses a magnetic vector potential approach, has also been developed for mapping the resulting field distribution. Future evaluation of MRI technology will likely require increasingly precise control and optimization of the rf magnetic field with the aim of improving sensitivity and resolution. The studies proposed here will complete previous work and extend prior results to a realistic clinical setting. With interaction of theory and experiment, a more complete understanding will be provide for these key MRI system components.
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