# RF Pulse Shape

The pulses are shaped like truncated sinc functions [ sinc (*x*) = (sin (*x*))/*x* ]. Without truncation sinc(*x*) → ±∞. A sinc(*x*) function is used because the Fourier transform of a sinc function is a rectangle. Remember that the time domain and frequency domain are related by the Fourier transform. Thus the shape of the excited tissue will be a rectangle: a "slice". We use a sinc function so that the edges of the slice (between one slice and the next one) can be made as sharp as possible.

Further reading on this topic:

Books: MRI From Picture to Proton p112, 346, Q&A in MRI p74, MRI The Basics p94-95