A device for treating a tissue region is supplied with a separate usage key card. The usage key card comprises a storage medium, which is formatted to contain an identification code unique to the usage key card. The usage key card is adapted to be read by a remote reader, to download the identification code for processing by a controller for the device. Processing of the identification code by the controller either enables or disables operation of the device according to prescribed criteria. A viewable image is generated on a display screen that changes in response to processing of the identification code.