Phase-cycled averaging for the suppression of residual magnetisation in SPI sequences

A prominent in vivo example is that of sodium imaging in biological tissue where transverse relaxation times are such that unwanted coherences can occur and therefore residual magnetisation becomes a significant problem. For instance, sodium in biological tissue has two transverse relaxation times of approximately 3 ms and 15 ms at 4 T and this can result in significant artefacts if the encoding time is short and TR ≪ 3 ms.