This invention provides an implantable infusion port which comprises a non planar septum, a fluid reservoir of a substantially spherical shape, inlet means to access the reservoir, and optimized outlet means from the reservoir. The rollers are mounted to rotate about an axle defining a primary axis of rotation extending at an angle of between about zero and 45 degrees to the walking direction, as viewed from above the shoe, for rolling sideways along a support surface. It is emphasized that this abstract is provided to comply with the rules requiring an abstract, which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. A radial clearance between the seal land and the knife edges is nominally 0. Also provided is a method of correlating a plurality of medical images by obtaining a trigger signal of a timing of interest, obtaining a plurality of images of a feature of interest, and correlating the plurality of images with the trigger signal. The slave unit having a mechanism for encryption judges whether it is located inside or outside the firewall, and executes encryption if it is located outside or executes no encryption if it is located inside.