Design ofB1-Insensitive andB1-Selective RF Pulses by Means of Stochastic Optimization
✍ Scribed by Klaus Scheffler
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 209 KB
- Volume
- 109
- Category
- Article
- ISSN
- 1064-1866
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✦ Synopsis
Novel B 1 -insensitive and B 1 -selective RF pulses are derived by insensitive pulse does not act according to the adiabatic prinapplying the stochastic optimization techniques of simulated anciple, it induces complete transverse magnetization, indepennealing and threshold accepting. These B 1 -insensitive pulses generdent of the applied RF power.
ate complete transverse magnetization over a wide range of RF
As a novel excitation, we propose a B 1 -selective pulse. This field strengths, whereas the B 1 -selective pulses act only over a pulse acts on the magnetization in a limited range of B 1 amplipredetermined range of RF field amplitudes. In combination with a tudes akin to a frequency-selective pulse that acts on a certain surface coil, B 1 -selective pulses can be used for regional excitation frequency range. Outside the defined B 1 range, the resulting without the application of B 0 gradients. The performance of the magnetization remains zero. Two major fields of applications two pulse types is verified experimentally, and the problems arising of B 1 -selective pulses are found in NMR imaging, with B 1in connection with their implementation are discussed. ᭧ 1995 Academic Press, Inc.
field slice selection and localized NMR spectroscopy with surface coils. Applying a single B 1 -selective pulse in combination with a surface coil, which produces a spherically shaped B 1 field distribution, it is possible to excite a single onion-shell-175