  We apply the path-integral method to study the multiple scattering and
collective flow in intensity interferometry in high-energy heavy-ion
collisions. We show that the Glauber model and eikonal approximation in an
earlier quantum treatment are special examples of the more general
path-integral method. The multiple scattering and collective flow lead
essentially to an initial source at a shifted momentum, with a multiple
collision absorption factor that depends on the pion absorption cross section
and a phase factor that depends on the deviations of the in-medium particle
momenta from their asymptotic values.
