A modified correlated spectroscopy (COSY) revamped with asymmetric Z-gradient echo detection sequence was designed to investigate the influence of diffusion behaviour on intermolecular double-quantum coherence signal attenuation during the pre-acquisition period.Theoretical formulas were deduced and experimental measurements and simulations were performed.It is found that the diffusion behaviour of intermolecular double-quantum coherence in the pre-acquisition period may be different from that of conventional single-quantum coherence,depending on the relative orientation of diffusion weighting gradients to coherence selection gradients.When the orientation of the diffusion weighting gradients is parallel or anti-parallel to the orientation of the coherence selection gradients,the diffusion is modulated by the distant dipolar field.This study is helpful for understanding the signal properties in intermolecular double-quantum coherence magnetic resonance imaging.
