Finite RF Pulse Correction on DESPOT2

Magnetization transfer and finite radiofrequency (RF) pulses affect the steady state of balanced steady state free precession. As quantification of transverse relaxation (T-2) with driven equilibrium single pulse observation of T-2 is based on two balanced steady state free precession acquisitions, both effects can influence the outcome of this method: a short RF pulse per repetition time (T-RF/TR << 1) leads to considerable magnetization transfer effects, whereas prolonged RF pulses (T-RF/TR > 0.2) minimize magnetization transfer effects, but lead to increased finite pulse effects. A correction for finite pulse effects is thus implemented in the driven equilibrium single pulse observation of T-2 theory to compensate for reduced transverse relaxation effects during excitation. It is shown that the correction successfully removes the driven equilibrium single pulse observation of T-2 dependency on the RF pulse duration. A reduction of the variation in obtained T-2 from over 50% to less than 10% is achieved. We hereby provide a means of acquiring magnetization transfer-free balanced steady state free precession images to yield accurate T-2 values using elongated RF pulses. Magn Reson Med 65:858-862, 2011. (c) 2010 Wiley-Liss, Inc.