We have continued our work on the development of algorithms for the synthesis of frequency-selective pulses. Our algorithm, called by others the Shinnar LeRoux (SLR) algorithm, has become a standard in the field. First, we can synthesize pulses which have the identical frequency profile, but require substantially less peak B1 power. This uses a modification of our algorithm. We have developed ways of getting a linear phase response for the pulse, while maintaining a reduced power requirement. Second, we have shown that the total energy of the pulse is encoded in one of the Fourier coefficients of the pulse. This is being used in two different projects. First, we are trying to synthesize adiabatic pulses with desired frequency response. Second, we shall determine how reducing the energy content of the pulse will reduce its slice selectivity. Third, we have continued to collaborate and provide pulses for specific applications. These include MRI coronary angiography, STEAM localized spectroscopy, and fast three dimensional angiography. In STEAM, we have shown that optimized pulses are crucial for the success of the technique. We are currently working on determining the most important parameters to optimize. Our last project is understanding the nature of what magnetizations are physically realizable. As part of this effort, we have shown that effects of a pulse far from the excited frequency range can have a major impact on the overall MR signal. The techniques developed by us are now part of a collaborative effort with Oded Gonen of Fox Chase Cancer Center to develop improved techniques for localized spectroscopy.
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