A podcast system and method are provided to select and deliver media ads over a network to a user device and to insert the media ads in media content subscribed to and delivered over the network to the user device. Since the internal resistance related value is a value related to the internal resistance which closely depends on the battery condition, the battery condition can be judged in detail based on the above relation. The balloon catheters of the present invention may be used in peripheral, coronary, or neurovascular applications.