A system for accessing implantable medical ports in the office setting

There is a need for safer and more reliable means to access to implanted ports in the office setting. We highlight this need using adjustable gastric bands as an example. We summarize the existing technology for providing the necessary needle guidance. We then describe approaches to position and orientation dependent (POD) sensing that use magnetic induction between coils. Two approaches are discussed, one based on frequency domain multiplexing and the other using Time Domain Multiplexing (TDM). We summarize the results of our experiments with prototype equipment. These results motivate a discussion of the utility of estimating the full relative position and orientation of the implant and external equipment. We then describe a port locator system based on multiple TDM POD measurements that uses an externally energized passive implant.