RAPID REPETITION OF THE BURST SEQUENCE - THE ROLE OF DIFFUSION AND CONSEQUENCES FOR IMAGING

When the Burst pulse sequence (Hennig et al. MAGMA 1, 39-48 (1993)) is applied with elementary pulses of finite flip angle, a non-uniform lo ngitudinal magnetization is created, in the form of a series of fine b ands of saturated spins. Both during and after the pulse train, the mo lecules contained within these bands diffuse. In this paper a full des cription is given of the evolution of the non-uniform longitudinal mag netization subsequent to the pulse train and the theory is verified ex perimentally. The value of the diffusion coefficient influences strong ly the signal obtained when the Burst sequence is repeated rapidly. Th e consequences of this for imaging are discussed and, in particular, f or the so-called ''frequency-shifted'' Burst technique.