Radial feed through packaging for an implantable electroacupuncture device
An implantable electroacupuncture device (IEAD) treats a disease or medical condition of a patient through application of stimulation pulses applied at a specified acupoint or other target tissue location. In a preferred implementation, the IEAD is an implantable, coin-sized, self-contained, leadless electroacupuncture device having at least two electrodes attached to an outside surface of its housing. The device generates stimulation pulses in accordance with a specified stimulation regimen. Power management circuitry within the device allows a primary battery, having a high internal impedance, to be used to power the device. The stimulation regimen generates stimulation pulses during a stimulation session of duration T3 minutes applied every T4 minutes. The duty cycle, or ratio T3/T4, is very low, no greater than 0.05. The low duty cycle and careful power management allow the IEAD to perform its intended function for several years.
1. An hermetically sealed, leadless, package for housing an implantable electroacupuncture device (IEAD), comprising:
a shallow coin-sized case having a bottom plate of width D2 and a side wall connected to a perimeter edge of the bottom plate, the side wall having a height W2, wherein the ratio of W2 to D2 is about 0.1, and wherein D2 is about 25 mm;
a radial recess formed at one portion of the side wall, said radial recess in the side wall extending radially inward toward the center of the bottom plate, and having a radial depth of D5 measured from the perimeter edge of the bottom plate, the side wall having an opening therein at or near the point where the radial recess has its maximum depth;
a feed-through pin; and
an insulating material through which the feed-through pin passes,
wherein the insulating material is hermetically bonded to the opening in the bottom of the recess, and the surface of the pin is hermetically bonded to the insulating material, and further wherein a distal end of the feed-through pin extends radially outward for at least a distance D5 to the top of the recess, and wherein a proximal end of the feed-through pin extends radially inward towards the center of the coin-sized case;
at least two electrodes mounted on an outside surface of the coin-sized case, including: (i) a central plate electrode mounted substantially in the center of an outside surface of the bottom plate of the coin-sized case, (ii) a ring electrode placed around the perimeter edge of the bottom plate so as to make electrical contact with the distal end of the feed-through pin, and (iii) an insulating layer of non-conductive material positioned between the ring electrode and the outside surface of the perimeter edge of the bottom plate, thereby preventing the electrode from making electrical contact with the outside surface of the coin-sized case;
wherein a feed-through assembly is created when electronic circuitry, comprising pulse generation circuitry powered by a thin coin-cell primary battery, is placed inside of the coin-sized case and connected to the proximal end of the feed-through pin, presenting stimulation pulses in accordance with a specified stimulation regimen at the ring electrode, with an electrical return path through the central plate electrode;
a cover plate welded to the upper edge of the side wall of the coin-sized case, thereby hermetically sealing the electronic circuitry inside of the case and cover, and
wherein an hermetically-sealed feed-through connection is established between the electronic circuitry on the inside of the coin-sized case and the central and ring electrodes mounted on the outside surface of the coin-sized case.
2. The hermetically sealed IEAD package of claim 1 further including
a layer of non-conductive material covering all external surface areas of the coin-sized case and cover plate except the circumscribing electrode and plate electrode.
3. The hermetically sealed IEAD package of claim 2 wherein the insulating material through which the feed-through pin passes comprises a ruby or ceramic insulator.
4. The hermetically sealed IEAD package of claim 3 wherein the feed-through pin, ruby insulator, and the bottom of the recess through which the feed-through pin and ruby or ceramic insulator pass are all hermetically sealed as a unit with gold brazing.
5. The feed-through assembly of claim 2 wherein the case and cover are round.