Evolution strategy optimization for adiabatic pulses in MRI

We propose a new type of adiabatic pulses for uniform inversion of the magn etization in magnetic resonance imaging. We produced these pulses with an e volution strategy optimization, by which the search of the "best solution" has been made more efficient than by deterministic algorithms. The pulse pa rametrization takes into account an "Offset-independent adiabaticity condit ion," which guarantees insensitivity to RF inhomogeneities. The RF pulse po wer (both peak and mean) contributes to the cost to be minimized, as well a s the error function does: in this way we obtain solutions that require low er energy than the well-known hyperbolic-secant pulse, with no loss of qual ity in the response profile. (C) 1999 Academic Press.