Validation of techniques that characterize and correct for brain shift for image guided surgery requires a realistic anthropomorphic phantom for use as a gold standard. The purpose of this study was to determine the characteristics of a deformable brain phantom made of polyvinyl alcohol cryogel (PVAc). The phantom was made of three layers of PVAc with inserted plastic tubes to simulate blood vessels. A catheter with an inflatable balloon was placed under the phantom in order to deform it in a nonlinear manner. The reproducibility of the elastic deformation was evaluated using MR imaging and surface measurements. Our experiments show that the phantom is well suited for MR and ultrasound imaging (B-mode and Doppler) with sub-millimeter reproducibility for the deformations.