Basic Concepts

The basic concepts about RF including hard pulse and soft pulse, and the implementation such as slice selective excitation, saturation, and refocusing will be introduced. The Fourier relationship between the RF pulse shape and the pulse profile should be understood. Given a slice-selective RF pulse and the initial orientation of the magnetization vector, the slice profile can be determined by solving the Bloch-equations. This will enable a deeper understanding of how RF pulses operate and help the audience in designing and choosing the proper pulses for their own experiments.

RF pulse design methods

This section will talk about different RF pulse design methods in kinds of application scenarios. The SLR algorithm is the hard pulse approximation that allows the pulse designer to generate target RF pulses given the desired slice profile and the initial conditions. Adiabatic pulses are a special class of RF pulses that can excite, refocus, or invert magnetization vectors uniformly, even in the presence of a spatially nonuniform B1 field. Instead, the flip angle of an adiabatic pulse depends on how the B1 field varies its amplitude and modulation frequency (or the phase) during the pulse. Multi-band pulses will excite multiband slices simultaneously which have been wildly used in MRI Acceleration techniques recently. Spatial-spectral pulses excite magnetization that has both a specified slice location and a specified spectral content and has clinical applications in lipid suppression and spectroscopic imaging (MRSI).

Acknowledgements

No acknowledgement found.

References

Bernstein M A, King K F, Zhou X J. Handbook of MRI pulse sequences. Elsevier, 2004.