  We study effects of a mean-field interaction on the spacetime geometry of the
hadron source measured by utilizing the Hanbury Brown and Twiss (HBT)
interferometry in the ultrarelativistic heavy-ion collisions. We show how a
modification of a pion amplitude, caused in the freeze-out process, is
incorporated into the correlation function of the interferometry within a
semiclassical method. Profiles of the distorted images are illustrated. To make
a quantitative estimate of the effects, we construct a mean-field-interaction
model on the basis of the pion-pion scattering amplitude, and then investigate
to what extent the effects of the mean-field interaction acts to efficiently
modify the HBT radii.
