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 .