Implantable medical device including eddy current reducing capacitor

An implantable device, such as a pacer, defibrillator, or other cardiac rhythm management device, can include one or more MRI Safe components. In an example, the implantable device includes a capacitor including a first electrode including a first slot extending from a perimeter of the first electrode to an interior of the first electrode. A second electrode is separated from the first electrode by a first distance. The second electrode includes a second slot extending from a perimeter of the second electrode to an interior of the second electrode. The first and second slots are configured to at least partially segment surface areas of the first and second electrodes, respectively, to reduce a radial current loop size in each of the first and second electrodes.

BACKGROUND

Implantable medical devices (IMDs) can perform a variety of diagnostic or therapeutic functions. For example, an IMD can include one or more cardiac function management features, such as to monitor the heart or to provide electrical stimulation to a heart or to the nervous system, such as to diagnose or treat a subject, such as one or more electrical or mechanical abnormalities of the heart. Examples of IMDs can include pacers, automatic implantable cardioverter-defibrillators (ICDs), or cardiac resynchronization therapy (CRT) devices, among others. Nuclear magnetic resonance imaging (MRI), is a medical imaging technique that can be used to visualize internal structure of the body. MRI is an increasingly common diagnostic tool, but can pose risks to a person with an IMD, such as a patient undergoing an MRI scan or a person nearby MRI equipment, or to people having a conductive implant.

In a MR field, an item, such as an IMD, can be referred to as “MR Safe” if the item poses no known hazard in all MRI environments. In an example, MR Safe items can include non-conducting, non-metallic, non-magnetic materials, such as glass, porcelain, a non-conductive polymer, etc. An item can be referred to as “MR Conditional” in the MR field if the item has been demonstrated to pose no known hazards in a specified MRI environment with specified conditions of use (e.g., static magnetic field strength, spatial gradient, time-varying magnetic fields, RF fields, etc.). In certain examples, MR Conditional items can be labeled with testing results sufficient to characterize item behavior in a specified MRI environment. Testing can include, among other things, magnetically induced displacement or torque, heating, induced current or voltage, or one or more other factors. An item known to pose hazards in all MRI environments, such as a ferromagnetic scissors, can be referred to as “MR Unsafe.”

DETAILED DESCRIPTION

Nuclear magnetic resonance (NMR) devices (e.g., an MRI scanner, an NMR spectrometer, or other NMR device) can produce both static and time-varying magnetic fields. For example, an MRI scanner can provide a strong static magnetic field, B0, such as to align nuclei within a subject to the axis of the B0field. The B0can provide a slight net magnetization (e.g., a “spin polarization”) among the nuclei in bulk because the spin states of the nuclei are not randomly distributed among the possible spin states. Because the resolution attainable by NMR devices can be related to the magnitude of the B0field, a stronger B0field can be used to spin polarize the subject's nuclei to obtain finer resolution images. NMR devices can be classified according the magnitude of the B0field used during imaging, such as a 1.5 Tesla B0field, a 3.0 Tesla B0field, etc.

After nuclei are aligned using the B0field, one or more radio frequency (RF) magnetic excitation pulses can be delivered such as to alter the alignment of specified nuclei (e.g., within a particular volume or plane to be imaged within the subject). The power, phase, and range of frequencies of the one or more RF excitation pulses can be selected, such as depending on the magnitude of the B0field, the type or resonant frequency of the nuclei to be imaged, or one or more other factors. After the RF excitation pulses are turned off, one or more RF receivers can be used to detect a time-varying magnetic field (e.g., a flux) developed by the nuclei as they relax back to a lower energy state, such as the spin polarized state induced by the static magnetic field, B0.

One or more gradient magnetic fields can also be provided during MR, such as to create a slight position-dependent variation in the static polarization field. The variation in the static polarization field slightly alters the resonant frequency of the relaxing nuclei, such as during relaxation after excitation by the one or more RF pulses. Using the gradient field along with the static field can provide “spatial localization” of signals detected by the RF receiver, such as by using frequency discrimination. Using a gradient field allows a volume or plane to be imaged more efficiently. In a gradient field example, signals received from relaxing nuclei can include energy in respective unique frequency ranges corresponding to the respective locations of the nuclei.

Active MRI equipment can induce unwanted torques, forces, or heating in an IMD or other conductive implant, or can interfere with operation of the IMD. In certain examples, the interference can include disruption in sensing by the IMD, interference in communication between the IMD and other implants or external modules during MRI operation, or disruption in monitoring or therapeutic function of the IMD.

During an MRI scan, the one or more RF excitation pulses can include energy delivered at frequencies from less than 10 MHz to more than 100 MHz, such as corresponding to the nuclear magnetic resonances of the subject nuclei to be imaged. The gradient magnetic field can include energy delivered at frequencies lower than the RF excitation pulses, because most of the AC energy included in the gradient field is provided when the gradient field is ramping or “slewing.” The one or more gradient magnetic fields can be provided in multiple axes, such as including individual time-varying gradient fields provided in each of the axes to provide imaging in multiple dimensions.

In an example, the static field, B0, can induce unwanted forces or torques on ferromagnetic materials, such as steel or nickel. The forces or torques can occur even when the materials are not directly within the “bore” of the MRI equipment—because significant fields can exist near the MRI equipment. Moreover, if an electric current is switched on or off in the presence of the B0field, a significant torque or force can be suddenly imposed in the plane of the circulation of the current, even though the B0field itself is static. The induced force or torque can be minimal for small currents, but the torque can be significant for larger currents, such as those delivered during defibrillation shock therapy. For example, assuming the circulating current is circulating in a plane normal (e.g., perpendicular) to the static field, the torque can be proportional to the magnitude of the B0field, multiplied by the surface area of the current loop, multiplied by the current.

Time-varying fields, such as the gradient field or the field associated with the RF excitation pulse, can present different risks than the static field, B0. For example, the behavior of a wire loop in the presence of a time-varying magnetic field can be described using Faraday's law, which can be represented by

ɛ=-ⅆΦB1ⅆt,
in which ε can represent the electromotive force (e.g., in volts), such as developed by a time-varying magnetic flux. The magnetic flux can be represented as

ΦB⁢⁢1=∫∫S⁢B1·ⅆS,
in which B1can represent an instantaneous magnetic flux density vector (e.g., in Webers per square meter, or Tesla). If B1is relatively uniform over the surface S, then the magnetic flux can be approximately ΦB1=|B1∥A|, where A can represent the area of the surface S. Operating MRI equipment can produce a time-varying gradient field having a slew rates in excess of 100 Tesla per second (T/s). The slew rate can be similar to a “slope” of the gradient field, and is thus similar to

The electromotive force (EMF) of Faraday's law can cause an unwanted heating effect in a conductor—regardless of whether the conductor is ferromagnetic. EMF can induce current flow in a conductor (e.g., a housing of an IMD, one or more other conductive regions within an IMD, or one or more other conductive implants). The induced current can dissipate energy and can oppose the direction of the change of the externally applied field (e.g., given by Lenz's law). The induced current tends to curl away from its initial direction, forming an “eddy current” over the surface of the conductor, such as due to Lorentz forces acting upon electrons moving through the conductor. Because non-ideal conductors have a finite resistivity, the flow of induced current through the conductor can generate heat. The induced heat can cause a significant temperature rise in or near the conductor over the duration of the scan. The eddy current power deposition can be proportional to the square of both the peak flux density and the frequency of the excitation.

Generally, induced currents, such as induced by the RF magnetic excitation pulse, can concentrate near the surface of a conductor, a phenomenon that can be referred to as the skin effect. The skin effect can limit both the magnitude and depth of the induced current, thus reducing power dissipation. However, the gradient field can include energy at a much lower frequency than the RF magnetic excitation field, which can more easily penetrate through the housing of the IMD. Unlike the field from the RF excitation pulse, the gradient field can more easily induce bulk eddy currents in one or more conductors within the IMD housing, such as within one or more circuits, capacitors, batteries, or other conductors.

Aside from heating, the MRI gradient induced EMF can create, among other things, non-physiologic voltages that can cause erroneous sensing of cardiac electrical activity, or the EMF can create a voltage sufficient to depolarize cardiac tissue or render the cardiac tissue refractory, possibly affecting pacing therapy. In an illustrative example, an IMD can be connected to one or more leads, such as one or more subcutaneous or intravascular leads positioned to monitor the patient, or to provide one or more therapies to the patient. In this illustrative example, a surface area of a “circuit” including the lead, the housing of the IMD, and a path through at least partially conductive body tissue between an electrode on the lead and the IMD housing can be more than 300 square centimeters, or more than 0.03 square meters. Thus, using Faraday's law, the electromotive force (EMF) developed through the body tissue between the electrode (e.g., a distal tip or ring electrode) of the lead and the housing of the IMD can be more than 0.03 square meters times 100 t/s, or more than 3 volts.

The present inventors have recognized, among other things, that it is desirable for IMDs to include increased safety within an MRI environment. For instance, the present inventors have recognized that it is desirable for IMDs to include a decreased response to the magnetic fields present within or otherwise proximate an MRI device. Such responses include, but are not limited to, heating, vibration or other induced movement, induced voltages, and the like. In some examples, the present inventors have recognized that it is desirable to reduce the magnetic field response of capacitors present in IMDs.

Referring toFIG. 1, an example of an IMD100is shown. The IMD100, in an example, includes a header102for attaching a component, such as a lead, to the IMD. In an example, the IMD100includes an electronic module104including electronics of the IMD100associated with the operation and functioning of the IMD100within a patient. In some examples, the IMD100includes a cell or battery106. In some further examples, the IMD100includes a capacitor108. In various examples, one of more of the components102,104,106,108or other components of IMDs which are not shown inFIG. 1, such as leads, for instance, can include decreased response to magnetic fields for increased safety within the MRI environment. As such, the description herein, although describing primarily decreased MR response in capacitors, can be applied to any components or combinations of components of an IMD, including also metal or otherwise conductive enclosures of the components of the IMD or of the IMD itself. Examples of IMDs that can include metal enclosures and/or internal large surface area components include but are not limited to, cardiac pacemakers; automatic implantable cardioverter-defibrillators (ICDs); cardiac resynchronization therapy and defibrillator (CRT-D) devices; neuromodulators including deep brain stimulators (DBS), various pain control devices, and lead systems for stimulation of the spinal cord, muscles, and other nerves of the body (such as, for instance, the vagal nerve); implantable diagnostic devices for monitoring cardiac function; cochlear implants; and drug pumps for administering periodic or demand based pharmacological therapy.

In various examples, the capacitor108includes an enclosure109. In some examples, the capacitor108can include one or more anode layers, one or more cathode layers, and one or more separators, which are each in stacked alignment with one another, within the enclosure109. Some examples include layers with connection members used for interconnecting to other layers. In various examples, a connection member extends away from the stacked layers, enabling interconnection among capacitor layers. For example, a number of anode connection members can extend away from the anode layers of the capacitor108for interconnection of the anode layers. In some examples, connection members can be used for the cathode layers. It is noted that, although portions of the description below focus on only one or two electrodes, the description of those sections can be applied to capacitors including more than one anode layer and/or more than one cathode layer.

In various examples, the capacitor108can include an aluminum electrolytic (AE) capacitor. In some examples, the AE capacitor includes at least one anode layer and at least one cathode layer, with the anode and cathode layers each including aluminum. In an example, the AE capacitor includes one or more anode layers including aluminum oxide on an aluminum substrate. In a further example, the aluminum substrate is etched. In an example, the AE capacitor includes one or more cathode layers including titanium on an aluminum substrate. In further examples, an electrolyte can be disposed between each of the layers of the AE capacitor. In further examples, a separator such as capacitor paper can be disposed between layers of the AE capacitor. Although materials of electrodes or other capacitor components may not be specified in the examples described below, it is noted that at least some of the examples below can be used with respect to AE capacitors, as well as with other types of capacitors and other IMD components.

Referring toFIG. 2, in various examples, a capacitor (such as the capacitor108of the IMD100ofFIG. 1) can include an electrode210. An arrow212is depicted on the electrode210to portray an example radial current or eddy current of the electrode210, such as could be induced by a gradient field of an MRI device. In an example, an induced eddy current can interact with the static magnetic field and can result in vibration or other movement of the electrode210(and, in turn, the capacitor). In another example, the induced eddy current can be dissipated as heat to elevate the temperature of the electrode210(and, in turn, the capacitor). For a given time varying gradient field, the induced torque and/or generated heat are functions of the material and the geometry of the electrode210. For instance, the eddy current induced heating and vibration are generally proportional to the square of the surface area of the conductor, or, in the example ofFIG. 2, generally the area encompassed by the induced eddy current shown by arrow212. Because of the relatively large surface area (and the relatively large loop212of the eddy current) of the example electrode210, a capacitor of an IMD can be a substantial source of heat and/or vibration when placed within an MRI environment. Accordingly, reduction of the loop size of an induced eddy current present in, for instance, an electrode of a capacitor of an IMD, is contemplated herein to reduce heating and/or movement induced in an IMD subjected to an MRI environment.

For instance, in AE capacitor examples, due, at least in part, to the relatively high conductivity of aluminum, an electrode of the AE capacitor can be relatively highly responsive to magnetic fields of an MRI environment, such as the gradient field of an MRI device. Moreover, in some examples, because thin aluminum foils can be used for electrodes of the AE capacitor, the electrodes can have a limited thermal mass, which can contribute to such electrodes heating up relatively quickly. Heating and/or vibration of components of implanted devices can be hazardous to a patient having an implanted device and being subjected to an MRI environment. For instance, heating and/or vibration of components of implanted devices can result in tissue damage to the patient. As such, the present inventors have recognized that it can be desirable to reduce surface areas of one or more components of implantable devices to limit the response (for instance, heating and/or vibration) of such implantable devices to an MRI environment, thereby making the implantable device MRI Safe. In some examples, as described in more detail below, the present inventors have recognized that a component of an implantable device can be segmented to reduce a surface area of the component, thereby decreasing the size of the radial current loop and reducing the response of the component to an MRI environment. Several examples of such segmented components are described below.

Referring toFIG. 3, a segmented electrode310of a capacitor (such as, for instance, the capacitor108ofFIG. 1) in accordance with some examples is shown. In some examples, the electrode310includes an opening or slot314extending from a perimeter of the electrode310to an interior of the electrode310. In other examples, the electrode can include more than one slot. In the example shown inFIG. 3, the slot314provides a break in the surface area of the electrode310, which can result in smaller radial current loops of eddy currents (relative to the loop size of the eddy current of an unsegmented electrode, such as the example electrode210ofFIG. 2), as depicted by arrows312A,312B. By reducing the loop size of the eddy currents in the electrode310, in an example, the heating and/or movement induced by an MRI environment can be reduced to a level at which the IMD and/or the capacitor of the IMD are deemed MRI Safe. Because removal of electrode material can generally adversely affect performance and effectiveness of the capacitor, a consideration in segmentation of the electrode310is minimal material removal. In an example, by optimizing a pattern of the segmentation of the electrode310, the performance of the capacitor can be minimally impacted while, at the same time, sufficiently minimizing eddy current loop size to result in an MRI Safe capacitor.

Referring toFIG. 4, an example of an unsegmented electrode410includes an interconnection area416. In various examples, the interconnection area416can allow for connection of the electrode410with one or more similar electrodes of a capacitor. For instance, as described above, two or more anode layers of a capacitor can be connected, and/or two or more cathode layers of a capacitor can be connected. However, in an example, if the electrode410ofFIG. 4were to be segmented with an opening or slot414(shown in phantom), current during charge and/or discharge of the capacitor would have to flow through a reduced cross section, as illustrated by arrow X inFIG. 4. Such “funneling” of current through the reduced cross section X of the electrode410, in some examples, can increase equivalent series resistance (ESR) of the capacitor, which can be detrimental to the performance of the capacitor. As such, the present inventors have recognized that it can be desirable to reposition the interconnection area of the electrode.

Referring toFIG. 5, in some examples, a segmented electrode510includes an opening or slot514and an interconnection area516repositioned relative to the interconnection area410of the example electrode410ofFIG. 4. In this example, the interconnection area516is substantially centrally located between portions510A,510B of the electrode510along an edge of the electrode516and substantially proximate an end of the slot514disposed in an interior of the electrode510. That is, the interconnection area516of this example can be located at or near an area of reduced cross section between an interior end of the slot514and the edge of the electrode510so that current can flow between the interconnection area516and each of the portions510A,510B of the electrode510with little or at least decreased “funneling” of current, as can be present in the configuration of the example electrode410described above. In this way, increases in ESR and other detrimental performance effects of the capacitor due to the reduced cross section of the electrode510can be reduced.

Referring toFIGS. 6-8, in some examples, a segmented first electrode610includes a first slot614extending from a perimeter of the first electrode610to an interior of the first electrode610. In an example, the first electrode610can be used as an anode layer of a capacitor, such as, for instance, a capacitor of an IMD. In some examples, a segmented second electrode620can be separated from the first electrode610by a first distance, as shown inFIG. 8. In an example, the second electrode620can include a second slot624extending from a perimeter of the second electrode620to an interior of the second electrode620. In an example, the second electrode620can be used as a cathode layer of a capacitor, such as, for instance, a capacitor of an IMD. In an example, the first and second slots614,624can be configured to at least partially segment surface areas of the first and second electrodes610,620, respectively, to reduce a radial current loop size in each of the first and second electrodes610,620, in a manner similar to that described above with respect to the example electrode310. In an example, one or more pairs of first and second electrodes610,620can be stacked (as seen generally inFIG. 8) to form a capacitor. In a further example, the capacitor can be an AE capacitor, as described above, in which the first electrode610includes an aluminum substrate at least partially covered with aluminum oxide. In a still further example, the capacitor can be an AE capacitor, as described above, in which the second electrode620includes an aluminum substrate at least partially covered with sputtered titanium.

In another example, the first electrode610can be substantially parallel to the second electrode620in a stacked configuration, as generally shown inFIG. 8. In an example, a separator can be disposed between the first electrode610and the second electrode620. In a further example, the separator can include capacitor paper. In another example, the separator can include an electrolyte material.

In an example, the first and second slots614,624are generally aligned with one another with the first and second electrodes610,620in the stacked configuration. In a further example, the first and second slots614,624can be disposed substantially along a center of the first and second electrodes610,620, respectively. In another example, the first slot614can be offset from the second slot624with the first and second electrodes610,620in the stacked configuration. That is, the first and second slots614,624can be staggered so as not to be one on top of the other with the first and second electrodes610,620in the stacked configuration. In an example, such an offset configuration can reduce the amount of large void volumes in which electrolyte can potentially pool in the capacitor, which can potentially lead decreased performance of the capacitor. In another example, such an offset configuration can inhibit the possibility of shorting between anode and cathode layers, for instance by decreasing the likelihood of a contaminant or other object becoming positioned across and remaining in contact with each of at least one anode and one cathode. In the example including the aligned slot configuration described above, the alignment of the first and second slots614,624can provide an area for a contaminant or other object to become lodged or otherwise positioned in contact with and across each of at least one anode and one cathode. However, if, in some instances, such a configuration is considered desirable, the possibility of such contaminants shorting the capacitor can be reduced with added care during manufacturing of the capacitor.

In an example, the first electrode610can include a first interconnection area616substantially centrally located along an edge of the first electrode610and substantially proximate an end of the first slot614that is disposed in the interior of the first electrode610. That is, the first interconnection area616can be located proximate the area of the first electrode610having a reduced cross section, in a manner similar to that described with respect to the example above including the interconnection area516. In a further example, the second electrode620can include a second interconnection area626substantially centrally located along an edge of the second electrode620and substantially proximate an end of the second slot624that is disposed in the interior of the second electrode620. That is, the second interconnection area626can be located proximate the area of the second electrode620having a reduced cross section, in a manner similar to that described with respect to the example above including the interconnection area516. Such interconnection areas616,626allow for two or more first electrodes610(for instance, anode layers) to be connected using a connection member and for two or more second electrodes620(for instance, cathode layers) to be connected using another connection member. By positioning the first and second interconnection areas616,626at or proximate the reduced cross sections of the segmented first and second electrodes610,620, increases in ESR and other detrimental performance effects of the capacitor due to the reduced cross section of the first and second electrodes610,620can be reduced, in a manner similar to that described with respect to the example electrode510above.

In a further example, the first interconnection area616can be offset from the second interconnection area626to allow for interconnection of two or more first electrodes610and for interconnection of two or more second electrodes620without having the first interconnection area616interfering or otherwise getting in the way of the second interconnection area626with the first and second electrodes610,620in the stacked configuration. Simply put, in an example, the first and second interconnection areas616,626cannot occupy the same area without increased manufacturing complexities.

In an effort to simplify manufacturing of the capacitor, in an example, the first interconnection area616of the first electrode610can be positioned slightly to one side of a center of the first electrode610and the second interconnection area626of the second electrode620can be positioned slightly to the other side of a center (aligned with the center of the first electrode610with the first and second electrodes610,620in the stacked configuration) of the second electrode620. In this way, two or more first electrodes610can be interconnected without interfering with the interconnection of two or more second electrodes620. In further examples, the first electrode610can include a cutout618configured to align with the second interconnection area626of the second electrode620, with the first and second electrodes610,620in the stacked configuration, wherein the cutout618can allow for a connection member from one second electrode620to another second electrode620to pass by the first electrode610without contacting the first electrode610. In this way, the cutout618reduces shorting concerns associated with interconnecting second electrodes620. In other examples, the second electrode620can include a cutout628configured to align with the first interconnection area616of the first electrode610, with the first and second electrodes610,620in the stacked configuration, to reduce shorting concerns associated with interconnecting first electrodes610in a manner similar to that described about with respect to the cutout618.

With reference toFIGS. 9 and 10, in some examples, segmented first and second electrodes910,920are shown generally in a stacked configuration. In various examples, such first and second electrodes910,920can be used in a capacitor for an IMD. In an example, the segmented first electrode910includes two first slots914each extending from a perimeter of the first electrode910to an interior of the first electrode910. In an example, the first electrode910can be used as an anode layer of a capacitor, such as, for instance, a capacitor of an IMD. In an example, the segmented second electrode920can include a second slot924extending from a perimeter of the second electrode920to an interior of the second electrode920. In an example, the second electrode920can be used as a cathode layer of a capacitor, such as, for instance, a capacitor of an IMD. In an example, the first and second slots914,924can be configured to at least partially segment surface areas of the first and second electrodes910,920, respectively, to reduce a radial current loop size in each of the first and second electrodes910,920, in a manner similar to that described in the examples above with respect to the first and second electrodes610,620.

The first electrode910can include the two first slots914for various reasons. In an example, a thickness of the first electrode910can be large enough that increased segmenting of the first electrode910is desirable to sufficiently reduce the loop size of the eddy currents in the first electrode910to reduce the heating and/or movement induced by an MRI environment to a level at which the first electrode910is deemed MRI Safe. For instance, in an example, the thickness of the first electrode910can be approximately four times the thickness of the second electrode920. In another example, the two first slots914can allow for each of the first slots914to be offset from the second slot924with the first and second electrodes910,920in the stacked configuration. That is, the first and second slots914,924can be staggered so as not to be one on top of the other with the first and second electrodes910,920in the stacked configuration. In an example, such an offset configuration can reduce the amount of large void volumes in which electrolyte can potentially pool in the capacitor, which can potentially lead decreased performance of the capacitor. In another example, such an offset configuration can inhibit the possibility of shorting between anode and cathode layers, for instance by decreasing the likelihood of a contaminant or other object becoming positioned across and remaining in contact with each of at least one anode and one cathode. In the example including the aligned slot configuration described above, the alignment of the first and second slots914,924can provide an area for a contaminant or other object to become lodged or otherwise positioned in contact with and across each of at least one anode and one cathode.

In an example, the first electrode910can include a first interconnection area916located along an edge of the first electrode910and substantially equidistant from an interiorly-disposed end of each of the first slots914. In this way, the first interconnection area916can be located proximate each area of the first electrode910having a reduced cross section. In a further example, the second electrode920can include a second interconnection area926substantially centrally located along an edge of the second electrode920and substantially proximate an end of the second slot924that is disposed in the interior of the second electrode920. That is, the second interconnection area926can be located proximate the area of the second electrode920having a reduced cross section. Such interconnection areas916,926allow for two or more first electrodes910(for instance, anode layers) to be connected using a connection member and for two or more second electrodes920(for instance, cathode layers) to be connected using another connection member. By positioning the first and second interconnection areas916,926at or proximate the reduced cross sections of the segmented first and second electrodes910,920, increases in ESR and other detrimental performance effects of the capacitor due to the reduced cross section of the first and second electrodes910,920can be reduced, in a manner similar to that described with respect to the example electrode510above.

In an example, the first interconnection area916can be positioned slightly to one side of a center of the first electrode910, and the second interconnection area926can be positioned slightly to the other side of a center (aligned with the center of the first electrode910with the first and second electrodes910,920in the stacked configuration) of the second electrode920. In this way, two or more first electrodes910can be interconnected without interfering with the interconnection of two or more second electrodes920. In further examples, the first electrode910can include a cutout918configured to align with the second interconnection area926of the second electrode920, with the first and second electrodes910,920in the stacked configuration, wherein the cutout918can allow for a connection member from one second electrode920to another second electrode920to pass by the first electrode910without contacting the first electrode910. In this way, the cutout918reduces shorting concerns associated with interconnecting second electrodes920. In other examples, the second electrode920can include a cutout928configured to align with the first interconnection area916of the first electrode910, with the first and second electrodes910,920in the stacked configuration, to reduce shorting concerns associated with interconnecting first electrodes910in a manner similar to that described about with respect to the cutout918.

In an example, a method can include stacking a first electrode with a second electrode, wherein the second electrode is separated from the first electrode by a first distance. In an example, the method can include placing a separator in between the first and second electrodes. In an example, the separator includes capacitor paper. In a further example, the separator includes an electrolyte. The first electrode can include a first slot extending through the first electrode from a perimeter of the first electrode to an interior of the first electrode. The second electrode can include a second slot extending through the second electrode from a perimeter of the second electrode to an interior of the second electrode. The first and second slots can be configured to at least partially segment a surface area of the first and second electrodes, respectively, to reduce a radial current loop size in each of the first and second electrodes. The method, in some examples, can include segmenting the first and second electrodes to form the first and second slots. In a further example, the first electrode is segmented to form more than one first slot.

With reference to the examples described above, various manufacturing operations are contemplated for producing the segmented electrodes. In an example, segmenting of the first and second electrodes includes die cutting the first and second electrodes to form the first and second slots. In a further example, die cutting can be used to cut the electrodes to the desired size and shape, while, at the same time, forming the one of more openings or slots in the electrode. With respect to AE capacitors, as described above, an anode layer can include aluminum oxide, which can be relatively brittle. However, the present inventors have recognized that die cutting of such a brittle material can be performed with at least an adequate success rate.

The above described examples illustrate segmented components of an IMD and methods of making such segmented IMD components, with such segmented components including a reduced response (as compared to un-segmented components) to magnetic fields present in an MRI environment. In some examples, such segmentation can be included in IMD capacitors. In further examples, electrodes, including anodes and/or cathodes, of IMD capacitors can be segmented in order to make the IMD capacitor MRI Safe. By segmenting IMD components as described above, the present inventors have recognized that eddy currents in the IMD components can be reduced, thereby resulting in reduced heating and/or vibration of the segmented components when exposed to an MRI environment. In this way, examples of the segmented IMD components and methods, such as those described above, can be used in various IMDs to make such IMDs MRI Safe.

Additional Notes