1. An apparatus for imaging the mechanical properties of a tissue region from within an endocavity of a patient, the apparatus comprising: (a) an ultrasound probe insertable inside the endocavity and having a distal end contactable against the tissue region to be imaged; (b) a vibration assembly translationally coupled to a proximal end of the probe and operable to vibrate the probe along a vibration plane parallel to the longitudinal axis of the probe; and (c) a rotation assembly rotationally coupled to the vibration assembly and operable to rotate the probe and vibration assembly such that the vibration plane is rotated about a selected rotational range.