This application relates to Implantable Medical Devices (IMDs), and more specifically to circuitry to assist with calibrating stimulation in an implantable stimulator device.
Implantable neurostimulator devices are devices that generate and deliver electrical stimuli to body nerves and tissues for the therapy of various biological disorders, such as pacemakers to treat cardiac arrhythmia, defibrillators to treat cardiac fibrillation, cochlear stimulators to treat deafness, retinal stimulators to treat blindness, muscle stimulators to produce coordinated limb movement, spinal cord stimulators to treat chronic pain, cortical and deep brain stimulators to treat motor and psychological disorders, and other neural stimulators to treat urinary incontinence, sleep apnea, shoulder subluxation, etc. The description that follows will generally focus on the use of the invention within a Spinal Cord Stimulation (SCS) system, such as that disclosed in U.S. Pat. No. 6,516,227. However, the present invention may find applicability with any implantable neurostimulator device system.
An SCS system typically includes an Implantable Pulse Generator (IPG) 10 shown in
In the illustrated IPG 10, there are thirty-two electrodes (E1-E32), split between four percutaneous leads 15, or contained on a single paddle lead 19, and thus the header 23 may include a 2×2 array of eight-electrode lead connectors 22. However, the type and number of leads, and the number of electrodes, in an IPG is application specific and therefore can vary. The conductive case 12 can also comprise an electrode (Ec). In a SCS application, the electrode lead(s) are typically implanted in the spinal column proximate to the dura in a patient's spinal cord, preferably spanning left and right of the patient's spinal column. The proximal contacts 21 are tunneled through the patient's tissue to a distant location such as the buttocks where the IPG case 12 is implanted, at which point they are coupled to the lead connectors 22. In other IPG examples designed for implantation directly at a site requiring stimulation, the IPG can be lead-less, having electrodes 16 instead appearing on the body of the IPG 10 for contacting the patient's tissue. The IPG lead(s) can be integrated with and permanently connected to the IPG 10 in other solutions. The goal of SCS therapy is to provide electrical stimulation from the electrodes 16 to alleviate a patient's symptoms, such as chronic back pain.
IPG 10 can include an antenna 27a allowing it to communicate bi-directionally with a number of external devices discussed subsequently. Antenna 27a as shown comprises a conductive coil within the case 12, although the coil antenna 27a can also appear in the header 23. When antenna 27a is configured as a coil, communication with external devices preferably occurs using near-field magnetic induction. IPG 10 may also include a Radio-Frequency (RF) antenna 27b. In
Stimulation in IPG 10 is typically provided by pulses each of which may include a number of phases such as 30a and 30b, as shown in the example of
In the example of
IPG 10 as mentioned includes stimulation circuitry 28 to form prescribed stimulation at a patient's tissue.
Proper control of the PDACs and NDACs allows any of the electrodes 16 to act as anodes or cathodes to create a current through a patient's tissue, R, hopefully with good therapeutic effect. In the example shown, electrode E1 has been selected as an anode electrode to source current to the tissue R and E2 as a cathode electrode to sink current from the tissue R. Thus PDAC1 and NDAC2 are activated and digitally programmed to produce the desired current, I, with the correct timing (e.g., in accordance with the prescribed frequency F and pulse widths PWa and PWb). Power for the stimulation circuitry 28 is provided by a compliance voltage VH, as described in further detail in U.S. Patent Application Publication 2013/0289665. As shown the compliance voltage may be coupled to the source circuitry (e.g., the PDAC(s)), while ground may be coupled to the sink circuitry (e.g., the NDAC(s)), such that the stimulation circuitry is coupled to and powered between the compliance voltage and ground. More than one anode electrode and more than one cathode electrode may be selected at one time, and thus current can flow through the tissue R between two or more of the electrodes 16. Stimulation circuitry 28 can differ. In an example not shown, a switching matrix can intervene between the one or more PDACs and the electrode nodes ei 39, and between the one or more NDACs and the electrode nodes, to allow any of the PDACs or NDACs to be connected to any of the electrode nodes. Various examples of stimulation circuitries can be found in U.S. Pat. Nos. 6,181,969, 8,606,362, 8,620,436, 10,912,942, and U.S. Patent Application Publication 2018/0071520. Much of the stimulation circuitry 28 of
Also shown in
Referring again to
External controller 60 can be as described in U.S. Patent Application Publication 2015/0080982 for example, and may comprise a controller dedicated to work with the IPG 10. External controller 60 may also comprise a general purpose mobile electronics device such as a mobile phone which has been programmed with a Medical Device Application (MDA) allowing it to work as a wireless controller for the IPG 10, as described in U.S. Patent Application Publication 2015/0231402. External controller 60 includes a user interface, preferably including means for entering commands (e.g., buttons or selectable graphical icons) and a display 62. The external controller 60's user interface enables a patient to adjust stimulation parameters, although it may have limited functionality when compared to the more-powerful clinician programmer 70, described shortly. The external controller 60 can have one or more antennas capable of communicating with the IPG 10. For example, the external controller 60 can have a near-field magnetic-induction coil antenna 64a capable of wirelessly communicating with the coil antenna 27a in the IPG 10. The external controller 60 can also have a far-field RF antenna 64b capable of wirelessly communicating with the RF antenna 27b in the IPG 10.
Clinician programmer 70 is described further in U.S. Patent Application Publication 2015/0360038, and can comprise a computing device 72, such as a desktop, laptop, or notebook computer, a tablet, a mobile smart phone, a Personal Data Assistant (PDA)-type mobile computing device, etc. In
To program stimulation programs or parameters for the IPG 10, the clinician interfaces with a clinician programmer graphical user interface (GUI) 82 provided on the display 74 of the computing device 72. As one skilled in the art understands, the GUI 82 can be rendered by execution of clinician programmer software 84 stored in the computing device 72, which software may be stored in the device's non-volatile memory 86. Execution of the clinician programmer software 84 in the computing device 72 can be facilitated by control circuitry 88 such as one or more microprocessors, microcomputers, FPGAs, DSPs, other digital logic structures, etc., which are capable of executing programs in a computing device, and which may comprise their own memories. Such control circuitry 88, in addition to executing the clinician programmer software 84 and rendering the GUI 82, can also enable communications via antennas 80a or 80b to communicate stimulation parameters chosen through the GUI 82 to the patient's IPG 10.
The user interface of the external controller 60 may provide similar functionality because the external controller 60 can include similar hardware and software programming as the clinician programmer. For example, the external controller 60 includes control circuitry 66 similar to the control circuitry 88 in the clinician programmer 70, and may similarly be programmed with external controller software stored in device memory.
A method is disclosed for determining one or more first thresholds for therapeutic stimulation provided to a patient by an implantable neurostimulator. The method may comprise: (a) providing the therapeutic stimulation to the patient via the implantable neurostimulator, wherein the therapeutic stimulation comprises a plurality of stimulation parameters; (b) determining a value for a neural response, wherein the neural response is formed in response to the therapeutic stimulation; and (c) determining one or more first thresholds for the therapeutic stimulation using the determined value for the neural response, wherein each first threshold is determined using a first mathematical relationship that models each first threshold as a function of values of the neural response.
In one example, the one or more first thresholds comprise thresholds for one of the stimulation parameters that causes a physiological response in the patient. In one example, the physiological response comprises one or more of paresthesia and discomfort. In one example, the one or more first thresholds comprise physiological thresholds. In one example, the one or more physiological thresholds comprise one or more of a perception threshold and a discomfort threshold. In one example, the one or more first thresholds comprise thresholds for an amplitude of the therapeutic stimulation. In one example, the therapeutic stimulation is provided to the spinal column of the patient, and wherein the neural response comprises an Evoked Compound Action Potential. In one example, the value for the neural response comprises a value of one of the stimulation parameters. In one example, the value for the neural response comprises a minimum value of the one of the stimulation parameters at which the neural response is detectable. In one example, the one of the stimulation parameters comprises an amplitude of the therapeutic stimulation. In one example, the first mathematical relationship that models each first threshold is a linear function of the values of the neural response. In one example, the value for the neural response comprises an extracted neural threshold. In one example, an external device communicates with the implantable neurostimulator. In one example, the value for the neural response is determined in the external device. In one example, the method is initiated at a user interface of the external device. In one example, the first mathematical relationship for each of the first thresholds is stored in the external device. In one example, the one or more first thresholds is determined in the external device. In one example, the method may further comprise transmitting the one or more first thresholds to the implantable neurostimulator or to another external device. In one example, the method may further comprise prior to step (a), providing test stimulation to the patient via the implantable neurostimulator, wherein the test stimulation is provided at a plurality of different test pulse widths. In one example, the method may further comprise determining values for a neural response at each of the test pulse widths, wherein the neural response is formed in response to the test stimulation. In one example, the method may further comprise determining a second mathematical relationship that models values for the neural response as a function of pulse width using the values for the neural response as determined at each of the test pulse widths. In one example, in step (a) the therapeutic stimulation is provided to the patient at a therapeutic pulse width. In one example, in step (b) the value for the neural response is determined using the second mathematical relationship determined at the therapeutic pulse width.
A system is disclosed which may comprise: an external device configured to communicate with an implantable neurostimulator, wherein the external device is configured to: (a) program the implantable neurostimulator to provide therapeutic stimulation to a patient, wherein the therapeutic stimulation comprises a plurality of stimulation parameters; (b) determine a value for a neural response, wherein the neural response is formed in response to the therapeutic stimulation; and (c) determine one or more first thresholds for the therapeutic stimulation using the determined value for the neural response, wherein each first threshold is determined using a first mathematical relationship that models each first threshold as a function of values of the neural response.
In one example, the one or more first thresholds comprise thresholds for one of the stimulation parameters that causes a physiological response in the patient. In one example, the physiological response comprises one or more of paresthesia and discomfort. In one example, the one or more first thresholds comprise physiological thresholds. In one example, the one or more physiological thresholds comprise one or more of a perception threshold and a discomfort threshold. In one example, the one or more first thresholds comprise thresholds for an amplitude of the therapeutic stimulation. In one example, the therapeutic stimulation is provided to the spinal column of the patient, and wherein the neural response comprises an Evoked Compound Action Potential. In one example, the value for the neural response comprises a value of one of the stimulation parameters. In one example, the value for the neural response comprises a minimum value of the one of the stimulation parameters at which the neural response is detectable. In one example, the one of the stimulation parameters comprises an amplitude of the therapeutic stimulation. In one example, the first mathematical relationship that models each first threshold is a linear function of the values of the neural response. In one example, the value for the neural response comprises an extracted neural threshold. In one example, the system may further comprise the implantable neurostimulator. In one example, the implantable neurostimulator is configured to sense the neural response. In one example, the implantable neurostimulator is configured transmit information indicative of the sensed neural response to the external device. In one example, the first mathematical relationship for each of the first thresholds is stored in the external device. In one example, the external device is further configured to transmit the one or more first thresholds to the implantable neurostimulator or to another external device. In one example, the external device is further configured, prior to step (a), to program the implantable neurostimulator to provide test stimulation to the patient via the implantable neurostimulator, wherein the test stimulation is provided at a plurality of different test pulse widths. In one example, the external device is further configured to determinize values for a neural response at each of the test pulse widths, wherein the neural response is formed in response to the test stimulation. In one example, the external device is further configured to determine a second mathematical relationship that models values for the neural response as a function of pulse width using the values for the neural response as determined at each of the test pulse widths. In one example, in step (a) the therapeutic stimulation is provided to the patient at a therapeutic pulse width. In one example, in step (b) the value for the neural response is determined using the second mathematical relationship determined at the therapeutic pulse width.
A non-transitory computer readable medium is disclosed which may comprise instructions executable on an external device configured to communicate with an implantable neurostimulator, wherein the instructions are configured to: (a) render a user interface on the external device to allow a user program the implantable neurostimulator to provide therapeutic stimulation to a patient, wherein the therapeutic stimulation comprises a plurality of stimulation parameters; (b) determine a value for a neural response, wherein the neural response is formed in response to the therapeutic stimulation; and (c) determine one or more first thresholds for the therapeutic stimulation using the determined value for the neural response, wherein each first threshold is determined using a first mathematical relationship that models each first threshold as a function of values of the neural response.
An increasingly interesting development in pulse generator systems, and in Spinal Cord Stimulator (SCS) pulse generator systems specifically, is the addition of sensing capability to complement the stimulation that such systems provide. For example, and as explained in U.S. Patent Application Publication 2017/0296823, it can be beneficial to sense a neural response in neural tissue that has received stimulation from an SCS pulse generator.
The control circuitry 102 is programmed with a neural response algorithm 124 to evaluate a neural response of neurons that fire (are recruited) by the stimulation that the IPG 100 provides. One such neural response depicted in
The control circuitry 102 and/or the neural response algorithm 124 can also enable one or more sense electrodes (S) to sense the ECAP, either automatically or based on a user selection of the sense electrode(s) as entered into an external device (see
To assist with selection of the sensing electrode(s), and referring again to
Stimulation in IPG 100 can be provided with reference to a number of different physiological thresholds, which will different from patient to patient. Generally speaking, a physiological threshold comprises a threshold that causes a physiological response in the patient. Reaching a physiological threshold may be perceptible to the patient, such as paresthesia or discomfort.
It is normally useful for the clinician to determine at least one of these physiological thresholds for a given patient, because this can be useful to programming or controlling the patient's stimulation therapy. For example, pth can be important to determine if it is desired that a patient receive sub-perception stimulation therapy or supra-perception therapy. dth can be important to determine to ensure that stimulation therapy does not cause patient discomfort. Physiological thresholds can be determined by the clinician using the GUI 82 of the clinician programmer 70 as shown in
The GUI 82 can also include a stimulation parameters interface 132 which is used to set the stimulation parameters of the stimulation that the patient will receives. This can include means to adjust the amplitude (I), pulse width (PW) and frequency (F) of the stimulation pulses. The GUI can also include means to set the location of stimulation in the electrode array 17. This can involve selecting active electrodes (E), the polarity of those active electrodes (P; anode or cathode), and the percentage of amplitude I (X %) that each active electrode should receive. In this example, electrode E1 has been selected as an anode and E2 as a cathode, with each receiving 100% of current amplitude I as an anodic current (+I) and as a cathodic current (−I). However, and as mentioned earlier, more than one electrode can be selected as an anode and more than one electrode can be selected as a cathode at a given time by sharing the anodic or cathodic current between those anode/cathode electrodes, as dictated by percentage X %. Sharing the anodic and cathodic currents between different numbers of electrodes can set the position of anode and cathode poles (+ and −) as virtual poles between the physical location of the electrodes, as is known. Typically, the location of the stimulation in the electrode array 17 can be manipulated by the clinician, such as by using a computer mouse to move the location of the stimulation within the leads interface 130, and this is done with the goal of locating a position that treats the patient's symptoms (e.g., pain). Note that an electrode configuration algorithm can be used to automatically determine active electrodes (E), polarities (P), and percentages (X %) as the clinician positions the stimulation in the electrode array, as explained further in U.S. Pat. No. 10,881,859, which is incorporated herein by reference in its entirety. GUI 82 can also include a program interface 134 to allow a clinician to store and load stimulation programs for the patient.
Once generally optimal stimulation parameters (I, PW, F, E, P, X) have been determined for the patient, the clinician can determine one or more physiological thresholds discussed earlier. This can generally involve an amplitude “sweep” where the amplitude is set to 0 and is gradually increased until the patient first starts to perceive the stimulation (which establishes pth). Further increasing the amplitude until the patient experiences discomfort similarly establishes dth. Once these thresholds have been determined in this manner, they can be stored by the clinician in a threshold interface 136 in the GUI 82 along with the other stimulation parameters, which then allows these physiological thresholds to be used in setting or controlling the patient's stimulation. For example, once dth is set, the GUI 82 may set this as a maximum value for amplitude I, and may limit amplitude I adjustments to values lower than this maximum for patient safety. In another example, if the clinician decides that the patient should receive paresthesia-based therapy (i.e., supra-perception therapy where the patient perceives a sensation produced by the stimulation), the GUI 82 may set pth as an amplitude minimum, while also setting dth as an amplitude maximum for safety. Percentages of these values can be used as well. For example, the maximum amplitude may be set to 90% of dth to ensure some guardband against patient discomfort. Likewise, if the clinician decides that the patient should receive paresthesia-free (sub-perception) therapy, the GUI 82 may set pth as an amplitude maximum. Again, the maximum amplitude may be limited to a percentage of pth, such as 90% of pth to guardband against the possibility that the patient may feel the stimulation. The optimal stimulation parameters and any relevant physiological thresholds such as pth and/or dth can also be transmitted to and stored in the patient's external controller 60 and/or the patient's IPG 100, as shown in
While establishing physiological thresholds such as pth and dth can be useful, it does take some time for the clinician to perform. This can create problems for the clinician when trying to determine optimal stimulation parameters for the patient. As noted above, the clinician can attempt to move the location of the stimulation in the electrode array to try and find a location that best treats the patient's symptoms. Typically, the values of physiological thresholds such as pth and dth will change as the location of the stimulation changes. This can mean that the clinician may need to determine these thresholds at each new stimulation location, which as noted takes some time to manually establish.
Another shortcoming to determining pth and dth as described is that these thresholds are typically set once at the beginning of stimulation therapy, and may thereafter only be altered by the clinician from time to time. This is unfortunate, because it may be useful to adjust such thresholds in between clinician visits. In this regard, it is known that it can be necessary to adjust a patient's stimulation, because the stimulation environment has changed. If a patient changes position, such as going from sitting to standing, this can bring the electrodes closer to or farther from the spinal neural tissue. This would suggest that the intensity of stimulation (e.g., amplitude) may need to be decreased or increased to bring about the same therapeutic effect when treating a patient's symptoms. Scar tissue or changes to the electrode/tissue interface may also naturally change over time, which would also suggest that it may be beneficial to adjust a patient's stimulation. It would be expected that such changes to the stimulation environment would suggest the need to adjust the physiological thresholds. For example, if it is necessary to generally increase the amplitude of simulation given such environmental changes, it would be expected that pth and dth should also increase. However, pth and dth as just discussed are typically set or adjusted by the clinician only infrequently, as described above.
It would be beneficial to automatically change or update physiological thresholds such as pth and dth using measurements taken from the patient. This would allow clinician to more quickly establish values for such thresholds, and would allow such thresholds to be adjusted even after leaving a clinician's office. In this disclosure, neural response measurements are used to estimate, adjust, and set therapeutic thresholds. More specifically, extracted neural thresholds (ENTs) are determined. An ENT may be expressed in terms of current amplitude I of the stimulation therapy that is provided to the patient, and comprises the minimum amplitude at which a neural response can be reliably detected, as described further below. The inventors have noticed a correlation between ENTs and physiological thresholds such as pth and dth, which allows such thresholds to be estimated and updated using measured ENT values. In particular, the inventors have noticed a parallel between the strength-duration curves for ENTs and physiological thresholds such as pth and dth, which again allows physiological thresholds to be estimated and updated using measured ENT values. This is beneficial, because ENTs can be objectively measured, which allows physiological thresholds to be automatically and quickly adjusted on the fly. This both assists the clinician in determining physiological thresholds, and also allows for updating of these thresholds without a clinician's assistance.
An extracted neural threshold (ENT) as just noted may be expressed in terms of current amplitude I of the stimulation therapy that is provided to the patient, as shown in
For these reasons, an ENT, although measured objectively, does not comprise an absolute value, but instead has a value that may be system and/or patient dependent. In this regard, and referring again to
Even though ENT values may have some variability, the inventors have noticed based on empirical measurements that ENTs as measured in a given system vary predictably with physiological thresholds such as pth and dth otherwise determined by the system. This is shown in
In step 152, an ENT value is measured using stimulation parameters determined earlier for the patient. Specifically, and assuming option 148 is used to start the algorithm 150, the external device causes the IPG 100 to increase the amplitude I starting from zero, until a neural response such as an ECAP is detectable (either using extraction or visualization). The ENT could also be determined by decreasing I until ECAPs are no longer detectable. Because step 152 implicates use of the neural response algorithm 124, and because this algorithm 124 can also operate in part in the external device, step 152 may be performed at least in part in the external device or wholly within the IPG 100. Again, the neural response algorithm 124 can determine the ENT value using extraction or visualization techniques as described earlier.
In step 154, the determined ENT value is used to determine at least one neural threshold, such as pth (using relationship 140a) or dth (using relationship 140b). These relationships may be stored in the external device in conjunction with other aspects of algorithm 150. One skilled will understand that the physiological thresholds can be determined by entering the ENT value into the relationships 140a and 140b and solving for pth and/or dth. Again, if the relationships 140a and 140b are stored in the IPG 100, this step 154 can also be performed entirely within the IPG 100.
In step 156, the physiological thresholds pth and/or dth determined in step 156 are stored in the external device. In particular, the algorithm 150 may automatically populated these determined physiological thresholds into the threshold interface 136 of the GUI (
At this point, an optional step 158 may be performed to confirm that the determined physiological thresholds are at proper values by testing them on the patient. This is simpler and faster than determining these thresholds as described above using a full amplitude sweep. For example, in a manual mode, the amplitude value is set to the determined pth value (say pth=I=4.8 mA) and tested on the patient, perhaps by manually moving the amplitude up and down a slight amount from this value. From this, a slightly different value for pth may be determined (e.g., pth=4.9 mA or 4.7 mA), and this would occur more quickly because a full range of amplitude values is not tested. This example in effect provides an estimated pth value, which can then be quickly updated based on testing. dth may be similarly tested and confirmed. In a more automated approach, a small range of amplitude values is swept around the determined thresholds (e.g., from 4.5 mA to 5.1 mA), with the patient pressing a button (e.g., at I=4.9 mA) when (in this example) he can first start to feel paresthesia. pth in this example would be calibrated from 4.8 to 4.9 mA.
At step 160, the physiological thresholds as so determined (and perhaps confirmed at step 158) are transmitted to the patient's external controller 60 or to the patient's IPG 10 directly. As noted above, these thresholds can be put to useful ends in controlling patient stimulation therapy. If algorithm 150 runs exclusively in the IPG 100, such transmission of the determined physiological thresholds would not be necessary.
This suggests to the inventor that it may be beneficial to measure ENTs at more than one pulse width. Doing so allows a mathematical relationship 170 to be determined relating ENT values and pulse widths (i.e., ENT=f(PW)). This is shown in further detail in
Establishing relationship 170 is useful in the context of the disclosed technique, because it allows physiological thresholds like pth and dth to be estimated for different pulse widths, and algorithm 180 in
In step 182, an ENT value is measured using stimulation parameters determined earlier for the patient, but with different pulse widths. Specifically, and assuming option 148 is used to start the algorithm 150, the external device may provide an instruction 200 on the GUI 82 instructing the clinician to provide stimulation at a next (first) pulse width value, as shown in
Step 184 determines the ENT=f(PW) relationship 170 using the data in data table 200. This step was described earlier with respect to
Next is step 188, a therapeutic pulse width to be used for the patient is entered into the GUI (again using stimulation parameters interface 132 for example). In the depicted example, this pulse width value is 200 μs, which is assumed here to be the pulse width that has otherwise been deemed optimal to provide therapeutic stimulation for the patient. While an ENT value could be measured at this optimal pulse width, this is not necessary, because the ENT at PW=200 μs can be estimated using relationship 170 as just determined, which occurs at step 190. In this example, it is assumed using relationship 170 that ENT=1.6 mA at PW=200 μs.
From this estimated ENT value, and at step 192, one or more physiological thresholds like pth or dth can be estimated using the relationship 140a and 140b described earlier. For example purposes, it is only assumed that a single physiological threshold (pth) is determined at step 192. Plugging ENT=1.6 mA into relationship 140a yields pth=1.50, which as before can be auto-populated in GUI 82 at threshold interface 136 (
If later the pulse width of the patient's stimulation is changed (step 196), the physiological threshold(s) can be automatically adjusted without need to take further ENT measurements, because relationships 170, 140a, and/or 140b can be used to adjust the threshold(s). In this regard, and as shown in
To summarize, algorithm 180 (
While described in the context of determining physiological thresholds such as pth and dth, it should be understood that the disclosed techniques may also be used to determine target values for stimulation. In this regard, an optimal stimulation amplitude I for a patient can relate to physiological thresholds such as pth and dth. For example, an optimal stimulation amplitude I may comprise pth, a percentage of pth (e.g., I=70% pth), or a particular value between pth and dth (e.g., a midpoint value such as pth+[dth−pth/2]). Because physiological thresholds pth and dth can be determined using ENTs as described above, and because a desired amplitude threshold I can be based on or predicted using pth and/or dth, ENTs can be used to predict and/or adjust amplitude I.
Although particular embodiments of the present invention have been shown and described, the above discussion is not intended to limit the present invention to these embodiments. It will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention. Thus, the present invention is intended to cover alternatives, modifications, and equivalents that may fall within the spirit and scope of the present invention as defined by the claims.
This is a non-provisional application of U.S. Provisional Patent Application Ser. No. 63/165,825, filed Mar. 25, 2021, to which priority is claimed, and which is incorporated by reference in its entirety.
Number | Date | Country | |
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63165825 | Mar 2021 | US |