  We report sensitive detection of parametric resonances in a high-density
sample of ultracold $^{87}Rb$ atoms confined to a far-off-resonance optical
dipole trap. Fluorescence imaging of the expanded ultracold atom cloud after a
period of parametric excitation shows significant modification of the atomic
spatial distribution and has high sensitivity compared with traditional
measurements of parametrically-driven trap loss. Using this approach, a
significant shift of the parametric resonance frequency is observed, and
attributed to the anharmonic shape of the dipole trap potential.
