  We review Foyle et al. (2011) previous results, by applying a Fourier
intensity phases method to a nine object sample of galaxies. It was found that
two of the objects (NGC 628 and NGC 5194), with strong two-arm patterns,
present positive evidence for long-lived spirals. Only one of the objects (NGC
3627) shows the contrary evidence. As determined by an analysis of resolved
mass maps, the rest of the objects can not be included in the analysis because
they belong to flocculent and multi-arm type of spiral arms, which are not
described by density wave theory.
