We present a systematic numerical investigation of the imaging of states in highly transmiting open quantum dots within a Green's function method applied to a tight-binding lattice model. We show evidence that images obtained from conductance change are not bona fide images of the unperturbed probability densities, because the coupled quantum dot-tip system induces coupling between several resonances, hindering a reliable interpretation of the conductance maps. We suggest that mapping the energy shifts of the resonances may provide the necessary complementary tool for good wave function imaging in quantum billiards.7124