Devices and methods for assessing the orientation and shape of vessel lumens and hollow portions of organs are described. The devices and methods are particularly adapted for determining the orientation and shape of a lumen to, for example, perform a valvuloplasty or facilitate the later implantation of a prosthetic heart valve. The devices are typically catheter-based having an expandable member fixed to a distal end of the catheter. Located within the expandable member are materials of different densities wherein the materials of different densities cooperate to indicate the orientation of the device within a lumen. The methods typically comprise deploying the balloon percutaneously to a target location, expanding the balloon, and determining the orientation and shape of a lumen.
