An endoprosthesis or stent comprising a continuous loop of material is disclosed, along with a method and systems for deploying the stent at a desired location within a collapsed vessel. The stent can comprise a double spiral configuration or a double helix configuration, and can be coated with a slippery biocompatable substance. The systems for deploying a stent include catheters capable of maintaining a stent in a reduced diameter state and releasing the stent so that it can resume it expanded diameter state at the implantation site.