Adjustable gastric band implants contain a hollow elastomeric balloon with fixed end points encircling a patient's stomach just inferior to the esophago-gastric junction. These balloons can expand and contract through the introduction of saline solution into the balloon. In current bands, this saline solution must be injected into a subcutaneous port with a needle to reach the port located below the skin surface. The port communicates hydraulically with the band via a catheter. As an alternative to using a percutaneously accessed injection port, a system for regulating the flow of saline that is totally implanted may rely upon bidirectionally pumping fluid from an implant device. This system instead transfers AC magnetic flux energy from an external primary coil to a secondary coil that powers the pump in the implanted reservoir. A magnetically permeable rod centered within the primary coil increases power coupled to the secondary coil. <；IMAGE>；
