Boston Scientific Neuromodulation Corporation

Robert Dai Ozawa

Jordi Parramon

Joey Y Chen

Rafael Carbunaru

Md Mizanur Rahman

Vasily Dronov

Daniel Aghassian

Emanuel Feldman

Jess Weiqian Shi

Robert Graham Lamont

Damon Moazen

Joonho Hyun

Goran Nils Marnfeldt

Thomas W Stouffer

Yuping He

Dennis Allen Vansickle

Kenneth A McGiboney

Dave Peterson

Kelly Hobart McClure

Scott M Loftin

Gaurav Gupta

Mizanur Rahman

Michael L Fister

Goran N Marnfeldt

Robert G Lamont

Dennis A Vansickle

An implantable medical device (IMD) is disclosed having measurement circuitry for measuring one or more currents in the IMD, such as the currents drawn from various power supply voltages. Such currents are measured without disrupting normal IMD operation, and can be telemetered from the IMD for review. Switching circuitry in line with the current being measured is temporarily opened for a time period to disconnect the power supply voltage from the circuitry being powered. A voltage across a capacitance in parallel with the circuitry is measured when the switching circuitry is opened and again closed at the end of the time period, with the circuitry drawing power from the charged capacitance during this time period. The average current drawn by the power supply voltage is determined using the difference in the measured voltages, the known capacitance, and the time period between the measurements.

Power supply disconnect current measurement for an implantable medical device

An external charger for a battery in an implantable medical device and charging techniques are disclosed. Simulation data is used to model the power dissipation of the charging circuitry in the implant at varying levels of implant power. A power dissipation limit constrains the charging circuitry from producing an inordinate amount of heat to the tissue surrounding the implant, and duty cycles of a charging field are determined so as not to exceed that limit. A maximum simulated average battery current determines the optimal (i.e., quickest) battery charging current, and at least an optimal value for a parameter indicative of that current is determined and stored in the external charger. During charging, the actual value for that parameter is determined, and the intensity and/or duty cycle of the charging field are adjusted to ensure that charging is as fast as possible, while still not exceeding the power dissipation limit.

Efficient external charger for an implantable medical device optimized for fast charging and constrained by an implant power dissipation limit

Preferred orientations and placements of an inductor relative to a communication coil in an Implantable Medical Device (IMD) are disclosed. The inductor can comprise part of a boost converter used to generate a power supply voltage in the IMD, which inductor may interfere with the coil. The inductor may have a length defined by its windings around an axis, which axis may be in a plane of the coil or in a plane parallel to the coil. The inductor can be included within the area extent of the coil, and is preferably oriented such that its axis is parallel to a maximum dimension of the coil. Ends of the inductor are further preferably equidistant from the coil. So oriented and placed, the inductor is less prone to interfering with the coil, thus improving communications with the IMD.

Orientation and placement of inductive components to minimize noise coupling to a communication coil in an implantable medical device

Battery management circuitry for an implantable medical device such as an implantable neurostimulator is described. The circuitry has a T-shape with respect to the battery terminal, with charging circuitry coupled between rectifier circuitry and the battery terminal on one side of the T, and load isolation circuitry coupled between the load and the battery terminal on the other side. The load isolation circuitry can comprise two switches wired in parallel. An undervoltage fault condition opens both switches to isolate the battery terminal from the load to prevent further dissipation of the battery. Other fault conditions will open only one the switches leaving the other closed to allow for reduced power to the load to continue implant operations albeit at safer low-power levels. The battery management circuitry can be fixed in a particular location on an integrated circuit which also includes for example the stimulation circuitry for the electrodes.

Battery management for an implantable medical device

The disclosed system for providing closed loop charging between an external charger and an implantable medical device such as an IPG involves the use of reflected impedance modulation, i.e., by measuring at the external charger reflections arising from modulating the impedance of the charging coil in the IPG. During charging, the charging coil in the IPG is periodically pulsed to modulate its impedance. The magnitude of the change in the coil voltage produced at the external charger &#x394;V as a result of these pulses is assessed and is used by the controller circuitry in the external charger as indicative of the coupling between the external charger and the IPG. The external charger adjusts its output power (e.g., Icharge) in accordance with the magnitude of &#x394;V, thus achieving closed loop charging without the need of telemetering coupling parameters from the IPG.

Closed loop charger for an implantable medical device system employing reflected impedance modulation

An external controller is disclosed for communicating with an external trial stimulator (ETS) for an implantable medical device. The external controller is programmed with a battery algorithm able to assist a clinician in choosing a suitable implant for the patient based on battery performance parameters estimated for a number of implants during an external trial stimulation phase that precedes implantation of the implant. The algorithm is particularly useful in assisting the clinician in choosing between a rechargeable-battery implant or a primary-battery implant for the patient.

External device for determining an optimal implantable medical device for a patient using information determined during an external trial stimulation phase

To recharge an implanted medical device, an external device, typically in the form of an inductive charger, is placed over the implant to provide for transcutaneous energy transfer. The external charging device can be powered by a rechargeable battery. Since the battery is in close proximity to the charge coil, the large magnetic field produced by the charge coil induces eddy currents that flow on the battery's metallic case, often resulting in undesirable heating of the battery and reduced efficiency of the charger. This disclosure provides a means of shielding the battery from the magnetic field to reduce eddy current heating, thereby increasing efficiency. In one embodiment, the magnetic shield consists of one or more thin ferrite plates. The use of a ferrite shield allows the battery to be placed directly over the charge coil as opposed to outside the extent of the charge coil.

Inductive charger with magnetic shielding

The disclosed means of determining alignment between an external charger and an implantable medical device (IMD) involves the use of reflected impedance modulation, i.e., by measuring at the external charger reflections arising from modulating the impedance of the charging coil in the IMD. During charging, the charging coil in the IMD is pulsed to modulate its impedance. The difference in the coil voltage (&#x394;V) produced at the external charger as a result of these pulses is assessed and is used by the external charger to indicate coupling. If the magnitude of &#x394;V is above a threshold, the external charger considers the coupling to the IMD to be adequate, and an alignment indicator in the external charger is controlled accordingly. The magnitude of Vcoil can be assessed in addition to &#x394;V to determine alignment with the IMD with improved precision, and/or to further define a high quality alignment condition.

Charger alignment in an implantable medical device system employing reflected impedance modulation

A base station for passively recharging a battery in an implant without patient involvement is disclosed. The base station can be hand held or may comprise equipment configured to be placed at a fixed location, such as under a bed, on or next to a wall, etc. The base station can generate electric and magnetic fields (E-field and B-field) that couple with an antenna and a receiving coil within the implant to generate a charging current for charging the implant's battery. No handling or manipulation on part of the patient is necessary; the implant battery is passively charged whenever the patient is within range of either the magnetic or electric charging fields generated by base station. Charging using the B-field occurs when the IPG is at a relatively short distance from the base station, while charging using the E-field occurs at longer distances.

Charging system for an implantable medical device employing magnetic and electric fields

An external charger for a battery in an implantable medical device (implant), and technique for charging batteries in multiple implants using such improved external charger, is disclosed. During charging, values for a parameter measured in the implants are reported from the implants to the external charger. The external charger infers from the magnitudes of the parameters which of the implants has the highest (hot) and lowest (cold) coupling to the external charger. The intensity of the magnetic charging field is optimized for the cold implant to ensure that it is charged with a maximum (fastest) battery charging current. The duty cycle of the magnetic charging field is also optimized for the hot implant to ensure that it does not exceed a power dissipation limit. As a result, charging is optimized to be fast for all of the implants, while still safe from a tissue heating perspective.

Efficient external charger for charging a plurality of implantable medical devices

An implantable medical device (IMD) is disclosed having one or more magnetic field sensors for measuring a strength of a magnetic charging field provided by an external charger and used to provide operational power to the IMD, for example, to charge its battery. The measured field strength data, or derivations of such data, are telemetered to the external charger, which further process the received data if necessary and can inform a user whether alignment between the external charger and IMD is sufficient, a misalignment direction, and/or a misalignment distance, so that the user can attempt to improve the alignment of the external charger. The one or more sensors are preferably placed at or equidistantly around a center axis of the IMD's charging coil. However, the sensors may be placed at any number of locations in the IPG, and at different distances from the center axis.

Growing community of inventors

Woodland Hills, CA, United States of America

Robert Dai Ozawa