USE OF AN OPTIMAL CONTROL ALGORITHM FOR THE DESIGN OF MRI REFOCUSING PULSES WITH PHASE-FREE ROTATION AXIS

摘要

A method of designing a refocusing pulse (RRP) or pulse train (RPT) for Magnetic Resonance Imaging comprising the steps of: a) determining a performance criterion, called phase-free performance criterion, representative of a proximity between a rotation of nuclear spins induced by said pulse and at least a target operator, summed or averaged over one or more voxels of an imaging region of interest; and b) adjusting a plurality of control parameters of said pulse to maximize said phase-free performance criterion; wherein said or each said target operator is chosen such that said phase-free performance criterion takes a maximum value when the nuclear spins within all said voxels undergo a rotation of a same angle Θ around a rotation axis lying in a plane perpendicular to a magnetization field B0, called a transverse plane, with an arbitrary orientation; characterized in that said angle Θ is different from Μπ radians, with integer M, preferably with θ<π radians and even preferably with θ≤0.9·π radians.