Don: I dug up a couple of (many) journal articles on the TET system. Here's an excerpt from "A Transcutaneous Energy and Information Transfer System for Implanted Medical Devices" from the American Society for Artificial Internal Organs Journal, 1995:
"The energy transfer system can deliver up to 60W with power transfer efficiences between 60 and 83%. An automatically tuned, resonant frequency tracking method is used to obtain optimum power transfer over a range of operating conditions. The remote communications sytems can transfer digital data through intact skin at rates up to 9600 baud. The system transmits information by frequency modulating an 890 nm infrared carrier signal. The system has demonstrated satisfactory performance during multicenter evaluation with ventricular assist and total artificial heart devices. Design improvements have been identified, which will be implemented to produce an optimized system for energy transfer to and remote communications with various implantable medical devices".
The last line is very interesting from a potential market point of view. The article lead off by saying...
"Currently there are more than 500,000 medical devices on the market and 25,000 new devices enter the market each year. Many medical devices are now designed to be implantable (pacemakers, cochlear implants, neuromuscular stimulators, biosensors, etc.). Almost all the active devices and many of the passive devices require a source of power."
So it would appear they could market the TET separately from the HeartSaver VAD and find a large potential market.
Back to your original question about the effects of power transfer through tissue,in "Transcutaneous Energy Transfer System", Artificial Organs, 1993, there's some information on the effect on tissue:
"To study the chronic impact on tissue, two control and two activated TET systems were implanted in a 45 kg porcine model (that's a pig!) for 6 weeks. These systems were designed to dissipate a controlled amount of power inside the implanted secondary coil...At the end of the 6 weeks, ellipses of skin taken from implantation istes were assessed for degree of inflammatory change, vascularization, fibrotic response and other changes. A maximum of 1.5 W, which represents the coil losses, was dissipated in the secondary coil. Results indicated no hisological damage and the TET will be able to deliver up to 40 W without the tissue-contacting surface temperature of the coil exceeding 42 degrees centrigrade."
Dan |
