Patent Description:
The invention relates to a system as defined in claim <NUM>. Systems and methods for optimizing evoked response signal generation during an electrode lead insertion procedure are described herein. For example, a diagnostic system may direct an acoustic stimulation generator to apply acoustic stimulation having a stimulus frequency to a recipient of a cochlear implant during an insertion procedure in which an electrode lead communicatively coupled to the cochlear implant is inserted into a cochlea of the recipient. The diagnostic system may direct the cochlear implant to use an electrode disposed on the electrode lead to record an evoked response signal during the insertion procedure. The evoked response signal represents amplitudes of a plurality of evoked responses that occur within the recipient in response to the acoustic stimulation applied to the recipient. The evoked responses may each be an ECoG potential (e.g., a cochlear microphonic potential, an action potential, a summating potential, etc.), an auditory nerve response, a brainstem response, a compound action potential, a stapedius reflex, and/or any other type of neural or physiological response that may occur within a recipient in response to application of acoustic stimulation to the recipient. Evoked responses may originate from neural tissues, hair cell to neural synapses, inner or outer hair cells, or other sources.

As the electrode lead is inserted into the cochlea, the diagnostic system may step the stimulus frequency through a sequence of decreasingly lower values starting with an initial value and ending with a final value lower than the initial value. As described herein, this stepping of the stimulus frequency through decreasingly lower values is based on an intracochlear positioning of the electrode used to record the evoked responses.

For example, the diagnostic system may maintain data representative of a sequence of decreasingly lower values to which the stimulus frequency may be set. An exemplary sequence of decreasingly lower values includes <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. These values are merely exemplary, and additional or alternative values may be included in the sequence as may serve a particular implementation.

Prior to a commencement of the electrode lead insertion procedure, the diagnostic system may set the stimulus frequency to be equal to an initial value (e.g., <NUM>) included in the sequence of decreasingly lower values. As the electrode lead is being inserted (e.g., by a surgeon or other user) into the cochlea of a recipient of a cochlear implant, the diagnostic system may direct an acoustic stimulation generator to apply acoustic stimulation having the initial stimulus frequency value to the recipient while a distal-most electrode disposed on the electrode lead (or any other designated electrode on the electrode lead) records evoked responses that occur in response to the acoustic stimulation. As the electrode lead is advanced further into the cochlea, the diagnostic system may determine that the electrode passes a characteristic frequency location within the cochlea that corresponds to the initial stimulus frequency value. This characteristic frequency location may be based, for example, on a cochlear tonotopic map.

In response to determining that the electrode passes the characteristic frequency location corresponding to the initial stimulus frequency value, the diagnostic system may decrease the stimulus frequency from the initial value to a next lower value (e.g., <NUM>) in the sequence of decreasingly lower values. Once the diagnostic system determines that the electrode lead passes a characteristic frequency location within the cochlea that corresponds to this next lower value, the diagnostic system may again decrease the stimulation frequency to a next lower value (e.g., <NUM>) in the sequence of decreasingly lower values. This process may be repeated for the remaining values included in the sequence of decreasingly lower values as the electrode lead is inserted further into the cochlea.

By incrementally stepping the stimulus frequency through a sequence of decreasingly lower values while the electrode lead is inserted further into the cochlea and/or by applying acoustic stimulation having a plurality of stimulus frequencies and plotting the graph as described above, the systems and methods described herein may optimize evoked response signal generation during an electrode insertion procedure in a manner that conveys more accurate, useful, and effective feedback to a user compared to techniques that only use a single stimulus frequency value (e.g., <NUM>) for the entire electrode lead insertion procedure. For example, a graph of the evoked response signal may be presented to the user in substantially real time during the insertion procedure, which may allow the user to visually ascertain electrode positioning within the cochlea, trauma that may occur to the cochlea during the insertion procedure, and/or various other factors associated with the insertion procedure. To illustrate, each time the electrode passes a characteristic frequency location associated with a current value of the stimulus frequency, the evoked response signal should peak and begin decreasing. However, if the decrease occurs before the electrode passes the characteristic frequency location, this may indicate that the electrode lead is causing damage to the cochlea. Such information may not be ascertainable in techniques that only use a single stimulus frequency value (e.g., <NUM>) for the entire electrode lead insertion procedure. These and other benefits and advantages of the systems and methods described herein will be made apparent herein.

<FIG> illustrates an exemplary cochlear implant system <NUM>. As shown, cochlear implant system <NUM> may include a microphone <NUM>, a sound processor <NUM>, a headpiece <NUM> having a coil disposed therein, a cochlear implant <NUM>, and an electrode lead <NUM>. Electrode lead <NUM> may include an array of electrodes <NUM> disposed on a distal portion of electrode lead <NUM> and that are configured to be inserted into a cochlea of a recipient to stimulate the cochlea when the distal portion of electrode lead <NUM> is inserted into the cochlea. One or more other electrodes (e.g., including a ground electrode, not explicitly shown) may also be disposed on other parts of electrode lead <NUM> (e.g., on a proximal portion of electrode lead <NUM>) to, for example, provide a current return path for stimulation current generated by electrodes <NUM> and to remain external to the cochlea after electrode lead <NUM> is inserted into the cochlea. As shown, electrode lead <NUM> may be pre-curved so as to properly fit within the spiral shape of the cochlea. Additional or alternative components may be included within cochlear implant system <NUM> as may serve a particular implementation.

As shown, cochlear implant system <NUM> may include various components configured to be located external to a recipient including, but not limited to, microphone <NUM>, sound processor <NUM>, and headpiece <NUM>. Cochlear implant system <NUM> may further include various components configured to be implanted within the recipient including, but not limited to, cochlear implant <NUM> and electrode lead <NUM>.

Microphone <NUM> may be configured to detect audio signals presented to the user. Microphone <NUM> may be implemented in any suitable manner. For example, microphone <NUM> may include a microphone that is configured to be placed within the concha of the ear near the entrance to the ear canal, such as a T-MIC™ microphone from Advanced Bionics. Such a microphone may be held within the concha of the ear near the entrance of the ear canal during normal operation by a boom or stalk that is attached to an ear hook configured to be selectively attached to sound processor <NUM>. Additionally or alternatively, microphone <NUM> may be implemented by one or more microphones disposed within headpiece <NUM>, one or more microphones disposed within sound processor <NUM>, one or more beam-forming microphones, and/or any other suitable microphone as may serve a particular implementation.

Sound processor <NUM> may be configured to direct cochlear implant <NUM> to generate and apply electrical stimulation (also referred to herein as "stimulation current") representative of one or more audio signals (e.g., one or more audio signals detected by microphone <NUM>, input by way of an auxiliary audio input port, input by way of a clinician's programming interface (CPI) device, etc.) to one or more stimulation sites associated with an auditory pathway (e.g., the auditory nerve) of the recipient. Exemplary stimulation sites include, but are not limited to, one or more locations within the cochlea, the cochlear nucleus, the inferior colliculus, and/or any other nuclei in the auditory pathway. To this end, sound processor <NUM> may process the one or more audio signals in accordance with a selected sound processing strategy or program to generate appropriate stimulation parameters for controlling cochlear implant <NUM>. Sound processor <NUM> may be housed within any suitable housing (e.g., a behind-the-ear ("BTE") unit, a body worn device, headpiece <NUM>, and/or any other sound processing unit as may serve a particular implementation).

In some examples, sound processor <NUM> may wirelessly transmit stimulation parameters (e.g., in the form of data words included in a forward telemetry sequence) and/or power signals to cochlear implant <NUM> by way of a wireless communication link <NUM> between headpiece <NUM> and cochlear implant <NUM> (e.g., a wireless link between a coil disposed within headpiece <NUM> and a coil physically coupled to cochlear implant <NUM>). It will be understood that communication link <NUM> may include a bi-directional communication link and/or one or more dedicated uni-directional communication links.

Headpiece <NUM> may be communicatively coupled to sound processor <NUM> and may include an external antenna (e.g., a coil and/or one or more wireless communication components) configured to facilitate selective wireless coupling of sound processor <NUM> to cochlear implant <NUM>. Headpiece <NUM> may additionally or alternatively be used to selectively and wirelessly couple any other external device to cochlear implant <NUM>. To this end, headpiece <NUM> may be configured to be affixed to the recipient's head and positioned such that the external antenna housed within headpiece <NUM> is communicatively coupled to a corresponding implantable antenna (which may also be implemented by a coil and/or one or more wireless communication components) included within or otherwise associated with cochlear implant <NUM>. In this manner, stimulation parameters and/or power signals may be wirelessly transmitted between sound processor <NUM> and cochlear implant <NUM> via communication link <NUM>.

Cochlear implant <NUM> may include any suitable type of implantable stimulator. For example, cochlear implant <NUM> may be implemented by an implantable cochlear stimulator. Additionally or alternatively, cochlear implant <NUM> may include a brainstem implant and/or any other type of cochlear implant that may be implanted within a recipient and configured to apply stimulation to one or more stimulation sites located along an auditory pathway of a recipient.

In some examples, cochlear implant <NUM> may be configured to generate electrical stimulation representative of an audio signal processed by sound processor <NUM> (e.g., an audio signal detected by microphone <NUM>) in accordance with one or more stimulation parameters transmitted thereto by sound processor <NUM>. Cochlear implant <NUM> may be further configured to apply the electrical stimulation to one or more stimulation sites (e.g., one or more intracochlear regions) within the recipient via electrodes <NUM> disposed along electrode lead <NUM>. In some examples, cochlear implant <NUM> may include a plurality of independent current sources each associated with a channel defined by one or more of electrodes <NUM>. In this manner, different stimulation current levels may be applied to multiple stimulation sites simultaneously by way of multiple electrodes <NUM>.

<FIG> illustrates a schematic structure of the human cochlea <NUM> into which electrode lead <NUM> may be inserted. As shown in <FIG>, cochlea <NUM> is in the shape of a spiral beginning at a base <NUM> and ending at an apex <NUM>. Within cochlea <NUM> resides auditory nerve tissue <NUM>, which is denoted by Xs in <FIG>. The auditory nerve tissue <NUM> is organized within the cochlea <NUM> in a tonotopic manner. Relatively low frequencies are encoded at or near the apex <NUM> of the cochlea <NUM> (referred to as an "apical region") while relatively high frequencies are encoded at or near the base <NUM> (referred to as a "basal region"). Hence, electrical stimulation applied by way of electrodes disposed within the apical region (i.e., "apical electrodes") may result in the recipient perceiving relatively low frequencies and electrical stimulation applied by way of electrodes disposed within the basal region (i.e., "basal electrodes") may result in the recipient perceiving relatively high frequencies. The delineation between the apical and basal electrodes on a particular electrode lead may vary depending on the insertion depth of the electrode lead, the anatomy of the recipient's cochlea, and/or any other factor as may serve a particular implementation.

<FIG> illustrates an exemplary diagnostic system <NUM> that may be configured to perform any of the operations described herein. As shown, diagnostic system <NUM> may include, without limitation, a storage facility <NUM> and a processing facility <NUM> selectively and communicatively coupled to one another. Facilities <NUM> and <NUM> may each include or be implemented by hardware and/or software components (e.g., processors, memories, communication interfaces, instructions stored in memory for execution by the processors, etc.). In some examples, facilities <NUM> and <NUM> may be distributed between multiple devices and/or multiple locations as may serve a particular implementation.

Storage facility <NUM> may maintain (e.g., store) executable data used by processing facility <NUM> to perform any of the operations described herein. For example, storage facility <NUM> may store instructions <NUM> that may be executed by processing facility <NUM> to perform any of the operations described herein. Instructions <NUM> may be implemented by any suitable application, software, code, and/or other executable data instance. Storage facility <NUM> may also maintain any data received, generated, managed, used, and/or transmitted by processing facility <NUM>.

Processing facility <NUM> may be configured to perform (e.g., execute instructions <NUM> stored in storage facility <NUM> to perform) various operations. For example, processing facility <NUM> may direct an acoustic stimulation generator to apply acoustic stimulation having a stimulus frequency to a recipient of a cochlear implant during an insertion procedure in which an electrode lead communicatively coupled to the cochlear implant is inserted into a cochlea of the recipient, direct the cochlear implant to use an electrode disposed on the electrode lead to record (e.g., detect) an evoked response signal during the insertion procedure (e.g., during all or only a portion of the insertion procedure), and incrementally step, as the electrode lead is inserted into the cochlea, the stimulus frequency through a sequence of decreasingly lower values starting with an initial value and ending with a final value lower than the initial value. Data representative of the recorded evoked response signal may be stored by processing facility <NUM> in storage facility <NUM> and/or in any other suitable storage medium as may serve a particular implementation.

Additionally or alternatively, processing facility <NUM> may direct an acoustic stimulation generator to apply acoustic stimulation having a plurality of stimulus frequencies to a recipient of a cochlear implant during an insertion procedure in which an electrode lead communicatively coupled to the cochlear implant is inserted into a cochlea of the recipient, direct the cochlear implant to use an electrode disposed on the electrode lead to record a plurality of evoked response signals during the insertion procedure, the evoked response signals each corresponding to a different stimulus frequency included in the plurality of stimulus frequencies, and plot, by way of a display device, a graph of the evoked response signals in substantially real time as the insertion procedure is being performed by switching between displaying each evoked response signal included in the plurality of evoked response signals such that, at any given time, only a single evoked response that has a highest amplitude compared to other evoked response signals in the plurality of evoked response signals is displayed by the display device. These and other operations that may be performed by processing facility <NUM> are described in more detail herein.

Diagnostic system <NUM> may be implemented in any suitable manner. For example, <FIG> shows an exemplary configuration <NUM> in which diagnostic system <NUM> is implemented by a computing system <NUM> configured to communicatively couple to sound processor <NUM>. As shown, computing system <NUM> may include an acoustic stimulation generator <NUM> communicatively coupled to a speaker <NUM>. Computing system <NUM> is also communicatively coupled to a display device <NUM>.

Computing system <NUM> may be implemented by any suitable combination of hardware (e.g., one or more computing devices) and software. For example, computing system <NUM> may be implemented by a computing device programmed to perform one or more fitting operations with respect to a recipient of a cochlear implant. To illustrate, computing system <NUM> may be implemented by a desktop computer, a mobile device (e.g., a laptop, a smartphone, a tablet computer, etc.), and/or any other suitable computing device as may serve a particular implementation.

Acoustic stimulation generator <NUM> may be implemented by any suitable combination of components configured to generate acoustic stimulation. In some examples, the acoustic stimulation may include one or more tones having one or more stimulus frequencies. Additionally or alternatively, the acoustic stimulation may include any other type of acoustic content that has at least a particular stimulus frequency of interest. Speaker <NUM> may be configured to deliver the acoustic stimulation generated by acoustic stimulation generator <NUM> to the recipient. For example, speaker <NUM> may be implemented by an ear mold configured to be placed in or near an entrance to an ear canal of the recipient.

Display device <NUM> may be implemented by any suitable device configured to display graphical content generated by computing system <NUM>. For example, display device <NUM> may display one or more graphs of evoked responses recorded by an electrode disposed on electrode lead <NUM>. In some alternative embodiments, display device <NUM> is integrated into computing system <NUM>.

<FIG> shows another exemplary configuration <NUM> in which diagnostic system <NUM> is implemented by computing system <NUM>. In configuration <NUM>, acoustic stimulation generator <NUM> is included in sound processor <NUM>. For example, sound processor <NUM> may be implemented by a bimodal sound processor (i.e., a sound processor configured to direct cochlear implant <NUM> to apply electrical stimulation to a recipient and acoustic stimulation generator <NUM> to apply acoustic stimulation to the recipient). In some examples, speaker <NUM> may be implemented by an audio ear hook that connects to sound processor <NUM>.

<FIG> illustrate an exemplary insertion procedure in which an electrode lead <NUM> is inserted into a cochlea <NUM> of a recipient. For illustrative purposes, cochlea <NUM> is depicted in <FIG> as being "unrolled" instead of its actual curved, spiral shape. Lead <NUM> may be similar to lead <NUM> and may include a plurality of electrodes (e.g., electrodes <NUM>-<NUM> through electrode <NUM>-<NUM>) disposed thereon. Electrode <NUM>-<NUM> is a distal-most electrode on lead <NUM> and electrode <NUM>-<NUM> is a proximal-most electrode on lead <NUM>.

Various characteristic frequency locations within cochlea <NUM> are depicted by vertical dashed lines in each of <FIG>. As shown, a first characteristic frequency location is associated with <NUM>. Hence, electrical stimulation applied by an electrode positioned at this characteristic frequency location may result in the recipient perceiving sound having <NUM>. <FIG> also depict characteristic frequency locations associated with <NUM>, <NUM>, <NUM>, and <NUM>. As shown, the frequencies associated with the characteristic frequency locations are tonotopically arranged, with relatively higher frequencies being located towards the entrance (or base) of cochlea <NUM> and relatively lower frequencies being located towards the distal end (or apex) of cochlea <NUM>.

<FIG> shows electrode lead <NUM> entering cochlea <NUM>. In this figure, electrode <NUM>-<NUM> is barely within cochlea <NUM>. <FIG> shows electrode lead <NUM> after electrode lead <NUM> has been advanced further into cochlea <NUM> such that electrode <NUM>-<NUM> is positioned at the characteristic frequency location corresponding to <NUM>. <FIG> show electrode lead <NUM> after electrode lead <NUM> has been advanced further into cochlea <NUM> such that electrode <NUM>-<NUM> is positioned at the characteristic frequency location corresponding to <NUM> (<FIG>), then <NUM> (<FIG>), then <NUM> (<FIG>), and then <NUM> (<FIG>).

Diagnostic system <NUM> may determine that electrode <NUM>-<NUM> passes a particular characteristic frequency location in any suitable manner. For example, diagnostic system <NUM> may determine that electrode <NUM>-<NUM> passes a particular characteristic frequency location by performing an excitation spread measurement (e.g., a cross impedance measurement) with respect to electrode <NUM>-<NUM> and at least one other electrode disposed on electrode lead <NUM>. Based on the excitation spread measurement, diagnostic system <NUM> may determine a number of electrodes disposed on electrode lead <NUM> that are located within cochlea <NUM>. Depending on the determined number of electrodes within cochlea <NUM>, diagnostic system <NUM> may determine (e.g., estimate) a positioning of electrode <NUM>-<NUM> in cochlea <NUM>.

For example, if diagnostic system <NUM> determines that three electrodes are within cochlea <NUM>, diagnostic system <NUM> may determine that electrode <NUM>-<NUM> is positioned at the characteristic frequency location corresponding to <NUM>. As another example, if diagnostic system <NUM> determines that six electrodes are within cochlea <NUM>, diagnostic system <NUM> may determine that electrode <NUM>-<NUM> is positioned at the characteristic frequency location corresponding to <NUM>. The relationship between number of electrode within cochlea <NUM> and the positioning of electrode <NUM>-<NUM> may be determined and/or defined in any suitable manner. In some examples, diagnostic system <NUM> maintains data (e.g., in the form of a lookup table) representative of this relationship.

As used herein, an "excitation spread measurement" may refer to any measurement configured to determine the extent to which stimulation (e.g., an electrical pulse) applied by one electrode at one location may spread or travel (e.g., through fluid and/or tissue at and surrounding the location) so as to be detectable (e.g., as a voltage) by another electrode at another location. As such, an excitation spread measurement as performed by the systems and methods described herein may be similar to a conventional impedance measurement in which stimulation is applied by an electrode and then detected by the same electrode (e.g., with reference to a ground electrode, with reference to another separate stimulating electrode, etc.). However, in contrast with conventional impedance measurements, excitation spread measurements as performed by the systems and methods described herein may apply stimulation with a different and distinct electrode from the electrode used to record (e.g., detect) the stimulation (e.g., a voltage resulting from the application of the stimulation) as the stimulation spreads. As such, in some examples, an excitation spread measurement may also be referred to as a "cross impedance" measurement or the like.

As one example of how an excitation spread measurement may be performed, diagnostic system <NUM> may direct a first electrode (e.g., electrode <NUM>-<NUM>) to generate an electrical pulse and, in response to the generation of the electrical pulse, may detect a voltage between a second electrode (e.g., another one of electrodes <NUM> or a ground electrode) and a reference (e.g., a ground electrode, a case ground of a cochlear implant, etc.) where both the second electrode and the reference are distinct from the first electrode. Based on the excitation spread measurement, diagnostic system <NUM> may determine whether at least one of the first electrode and the second electrode is located within cochlea <NUM>.

In certain implementations, diagnostic system <NUM> may perform one or more of the operations described above on each electrode <NUM>. In this way, diagnostic system <NUM> may detect enough information to determine not only a location for each electrode <NUM>, but also to determine an insertion depth of electrode lead <NUM> as a whole. For example, at a point in time during an insertion procedure, diagnostic system <NUM> may determine that electrode lead <NUM> is located in a position in which the first X number of electrodes <NUM> have been inserted into cochlea <NUM> while the remaining Y number of electrodes <NUM> are still external to the cochlea (where the sum of X and Y is the total number of electrodes disposed on the electrode lead).

An example of excitation spread measurements is provided with respect to <FIG>. In particular, <FIG> illustrates exemplary aspects of an electrode lead <NUM> and of patient anatomy as an insertion procedure is performed. Electrode lead <NUM> may be similar to any of the electrode leads described herein. Specifically, as shown, electrode lead <NUM> includes a proximal portion <NUM> beginning at a proximal end <NUM> and a distal portion <NUM> terminating at a distal end <NUM>. Disposed on electrode lead <NUM> is a plurality of electrodes <NUM>, including, on distal portion <NUM>, a plurality of stimulating electrodes <NUM>-S (e.g., stimulating electrodes <NUM>-S1 through <NUM>-S5 and <NUM>-S16, which are explicitly labeled, and additional electrodes <NUM>-S6 through <NUM>-S15, which are not explicitly labeled in <FIG> but may be referred to herein), and including, on proximal portion <NUM>, a ground electrode <NUM>-G (e.g., a ring electrode).

<FIG> illustrates a particular position of electrode lead <NUM> during an insertion procedure in which electrode lead <NUM> (i.e., and proximal portion <NUM> in particular) is being inserted from a middle ear <NUM> of a patient into a cochlea <NUM> of the patient through a round window <NUM> associated with cochlea <NUM>. For example, the goal of the insertion procedure may be to continue inserting distal portion <NUM> into cochlea <NUM> toward an apex <NUM> of cochlea <NUM> until the entirety of distal portion <NUM> (i.e., which may include all of electrodes <NUM>-S) has passed through round window <NUM> to be located within cochlea <NUM>.

In <FIG>, various aspects of electrode lead <NUM> and the illustrated anatomical features of the patient are simplified for clarity of illustration. For instance, while cochlea <NUM> has been "unrolled" in <FIG>, it will be understood that, as illustrated in <FIG>, cochlea <NUM> has a curved, spiral-shaped structure and that electrode lead <NUM> curves to follow the spiral-shaped structure. Similarly, the anatomy of middle ear <NUM> and cochlea <NUM> omit many details and are not drawn to scale.

<FIG> does, however, illustrate at least one aspect of the patient's anatomy that allows diagnostic system <NUM> to perform excitation spread measurements. As shown, on the cochlea side of round window <NUM>, cochlea <NUM> contains conductive fluid ("fluid") that, unlike gaseous fluids (e.g., air) on the other side of round window <NUM>, is conductive to electrical currents applied to the fluid. In certain examples, diagnostic system <NUM> may distinguish between different fluids within cochlea <NUM> (e.g., perilymph in the scala vestibuli and scala tympani, endolymph in the scala media, etc.) based on different conductivities of the different fluids. In this way, diagnostic system <NUM> may not only distinguish electrodes located in the fluid of cochlea <NUM> from electrodes still located in the air of middle ear <NUM>, but may further distinguish between electrodes located in different parts of cochlea <NUM> (e.g., within one of the scala vestibuli or scala tympani, within the scala media, etc.).

The fluid within cochlea <NUM> may carry current and provide for current conduction paths for an electrical pulse (e.g., a pulse provided by a current source or voltage source) to spread to at least some extent between electrodes <NUM>-S that have been inserted into cochlea <NUM> (i.e., that are surrounded by the fluid). Thus, for example, if an electrical pulse is generated at one particular electrode <NUM>-S, such as <NUM>-S1, the fluid may provide a conduction path from electrode <NUM>-S1 to other electrodes <NUM>-S that are included within cochlea <NUM> (i.e., electrodes <NUM>-S2 through <NUM>-S10 that are surrounded by the fluid at the moment illustrated in <FIG>) and to tissue surrounding cochlea <NUM>. The electrical pulse may be generated by a cochlear implant or other device communicatively coupled to proximal end <NUM>. Thus, a return path for current associated with the electrical pulse may extend from electrode <NUM>-S1, through the fluid of cochlea <NUM>, through the tissue associated with cochlea <NUM> and middle ear <NUM>, through ground electrode <NUM>-G, back to the voltage or current source included on the cochlear implant or other device that generated the electrical pulse.

Because the fluid inside cochlea <NUM> may conduct current while air outside cochlea <NUM> (i.e., the air in middle ear <NUM> on the other side of round window <NUM>) may not effectively conduct current, only electrodes <NUM>-S that have passed through round window <NUM> into cochlea <NUM> and are surrounded by the fluid of cochlea <NUM> may be able to detect the excitation spread of the electrical pulse generated by electrode <NUM>-S1 in the example above. Electrodes <NUM>-S that have not yet been inserted through round window <NUM> (e.g., electrodes <NUM>-S11 through <NUM>-S16 at the moment illustrated by <FIG>) may therefore not have a viable conduction path connecting them with electrode <NUM>-S1, and may therefore not be able to detect the excitation spread of the electrical pulse generated at electrode <NUM>-S1.

As described above, an excitation spread measurement may be performed by generating an electrical pulse at a first electrode (e.g., electrode <NUM>-S1 in the example above), and then detecting the electrical pulse (i.e., how the electrical pulse has spread) between a second electrode (e.g., one of electrodes <NUM>-S2 through <NUM>-S16 or <NUM>-G) and a reference (e.g., ground electrode <NUM>-G, a case ground of a cochlear implant, etc.). For example, the second electrode and the reference may both be separate from the first electrode, in contrast to how impedance measurements are typically performed. By knowing how much current or voltage was applied at the first electrode (e.g., by the current or voltage source that generates the electrical pulse) and how much current or voltage is detected at the second electrode, the extent to which the electrical pulse is able to spread between the first and second electrodes (e.g., through the fluid and/or tissue of cochlea <NUM>) may be determined (e.g., using Ohm's Law and/or other similar principles). Accordingly, by detecting that the electrical pulse has spread to at least some extent from the first electrode to the second electrode by way of an excitation spread measurement involving an electrode known to be inserted into cochlea <NUM>, diagnostic system <NUM> may determine that both electrodes are inserted into cochlea <NUM>. However, when an electrical pulse is determined to not have spread from the first electrode to the second electrode by way of an excitation spread measurement involving an electrode known to be inserted into cochlea <NUM> (i.e., when the electrical pulse cannot be detected at the second electrode because no conduction path exists between the first electrode and the second electrode due, for instance, to one of the electrodes being disposed in the air of middle ear <NUM>), diagnostic system <NUM> may determine that one of the electrodes has not yet entered into cochlea <NUM>.

Moreover, by determining whether each of electrodes <NUM>-S are located inside or outside cochlea <NUM> in this way, the insertion depth of the entire electrode lead <NUM> may be determined. For example, by determining that electrodes <NUM>-S1 through <NUM>-S10 are located within the fluid of cochlea <NUM> and that electrodes <NUM>-S11 through <NUM>-S16 are located within the air of middle ear <NUM>, diagnostic system <NUM> may determine that electrode lead <NUM> is a bit more than halfway into cochlea <NUM> but still needs to be inserted farther, as shown.

While the example above describes excitation spread measurements in which the electrical pulse is generated at an electrode known to already be inserted into cochlea <NUM> (i.e., electrode <NUM>-S1), the same excitation spread measurement principles may also work if the electrode known to already be inserted into cochlea <NUM> (i.e., electrode <NUM>-S1) is used to detect an electrical pulse generated at an electrode <NUM>-S that is under test. For example, diagnostic system <NUM> may determine whether electrode <NUM>-S5, for instance, is located in cochlea <NUM> (i.e., whether electrode <NUM>-S5 has a fluid conduction path with electrode <NUM>-S1) either by generating the electrical pulse at electrode <NUM>-S1 and attempting to detect the electrical pulse at electrode <NUM>-S5, or vice versa, by generating the electrical pulse at electrode <NUM>-S5 and attempting to detect the electrical pulse at electrode <NUM>-S1. Accordingly, diagnostic system <NUM> may include or have control over pulse generation and detection circuitry that is flexible to perform excitation spread measurements in these different ways.

Additional details and examples of excitation spread measurements are provided in <CIT>.

Diagnostic system <NUM> may additionally or alternatively determine that electrode <NUM>-<NUM> passes a particular characteristic frequency location by detecting, within a predetermined time period, that both an amplitude of the evoked response signal recorded by electrode <NUM>-<NUM> decreases by at least an amplitude threshold amount and a phase of the evoked response signal recorded by electrode <NUM>-<NUM> changes by at least a phase threshold amount.

To illustrate, <FIG> illustrates an exemplary lead insertion procedure in which electrode lead <NUM> is advanced into cochlea <NUM>. Reference numbers P1 through P5 indicate positions of electrode lead <NUM>. For example, at position P1, electrode lead <NUM> is at a first position in which electrode <NUM>-<NUM> is approaching the characteristic frequency location that corresponds to <NUM>. At position P2, electrode lead <NUM> is at a second position in which electrode <NUM>-<NUM> is at the characteristic frequency location that corresponds to <NUM>. At positions P3-P5, electrode lead <NUM> is at third, fourth, and fifth positions, respectively, in which electrode <NUM>-<NUM> has been advanced past the characteristic frequency location that corresponds to <NUM>.

<FIG> also shows a graph <NUM> of an amplitude of an evoked response signal recorded by electrode <NUM>-<NUM> during the lead insertion procedure and a graph <NUM> of a phase of the evoked response signal recorded by electrode <NUM>-<NUM> during the lead insertion procedure. In this example, the evoked response signal is generated in response to acoustic stimulation having a stimulus frequency of <NUM>. Hence, as shown in graph <NUM>, as electrode lead <NUM> advances towards the characteristic frequency location that corresponds to <NUM>, the amplitude of the evoked response signal increases and peaks when electrode lead <NUM> is positioned at position P2. As electrode lead <NUM> passes the characteristic frequency location that corresponds to <NUM>, the evoked response amplitude decreases until it settles at a steady state value. As shown in graph <NUM>, as electrode lead <NUM> advances towards the characteristic frequency location that corresponds to <NUM>, the phase of the evoked response remains at a relatively high level. However, the phase suddenly changes to a relatively low level as electrode lead <NUM> passes the characteristic frequency location that corresponds to <NUM>.

As shown in <FIG>, the decreasing of the evoked response amplitude and the changing of the phase from the high level to the low level occur at substantially the same time, and both occur as electrode <NUM>-<NUM> passes the characteristic frequency location that corresponds to <NUM>. Hence, diagnostic system <NUM> may determine that electrode <NUM>-<NUM> passes the characteristic frequency location that corresponds to <NUM> by detecting, within a predetermined time period, that both an amplitude of the evoked response signal recorded by electrode <NUM>-<NUM> decreases by at least an amplitude threshold amount and a phase of the evoked response signal recorded by electrode <NUM>-<NUM> changes by at least a phase threshold amount. The predetermined time period, the amplitude threshold amount, and/or the phase threshold amount may each be set by diagnostic system <NUM> to be any suitable value. For example, the predetermined time period may be set to be a relatively short time period (e.g., less than a few milliseconds) to ensure that the change in amplitude and in phase correspond to one another. In some examples, diagnostic system <NUM> may set the predetermined time period, the amplitude threshold amount, and/or the phase threshold in response to user input (e.g., by way of a graphical user interface). Additionally or alternatively, diagnostic system <NUM> may set the predetermined time period, the amplitude threshold amount, and/or the phase threshold automatically based on one or more factors, such as hearing loss, the stimulus frequency, recipient characteristics (e.g., age, gender, etc.), etc..

Graphs <NUM> and <NUM> assume that the stimulus frequency remains at <NUM> even after electrode <NUM>-<NUM> passes the characteristic frequency location that corresponds to <NUM>. However, the flat lines shown after the amplitude and phase settle to steady state are, in some examples, not helpful to a user performing the insertion procedure.

Hence, in accordance with the systems and methods described herein, in response to determining that electrode <NUM>-<NUM> passes a characteristic frequency location corresponding to one of the stimulus frequency values included in the sequence of decreasingly lower values, system <NUM> may decrease the stimulus frequency to a next lower value included in the sequence of decreasingly lower values. For example, with reference to <FIG>, system <NUM> may decrease the stimulus frequency to <NUM> in response to electrode <NUM>-<NUM> passing the characteristic frequency location that corresponds to <NUM>. In so doing, the amplitude of the evoked response signal recorded by electrode <NUM>-<NUM> may again increase until electrode <NUM>-<NUM> is positioned at the characteristic frequency location that corresponds to <NUM>. As electrode lead <NUM> passes the characteristic frequency location that corresponds to <NUM>, the evoked response amplitude decreases in a similar manner as shown in <FIG>. The phase of the evoked response signal likewise changes in a similar manner as shown in <FIG>. This process may be repeated as electrode <NUM>-<NUM> passes other characteristic frequency locations within cochlea <NUM>.

<FIG> shows a graph <NUM> of an amplitude of an evoked response signal recorded by electrode <NUM>-<NUM> while diagnostic system <NUM> sequentially steps through stimulus frequency values of <NUM>, <NUM>, <NUM>, and <NUM> as described above. <FIG> also shows a graph <NUM> of a phase of the evoked response signal recorded by electrode <NUM>-<NUM> while diagnostic system <NUM> sequentially steps through stimulus frequency values of <NUM>, <NUM>, <NUM>, and <NUM> as described above. As shown in graph <NUM>, the amplitude of the evoked response signal includes a series of peaks <NUM> (e.g., <NUM>-<NUM> through <NUM>-<NUM>) that temporally align with when electrode <NUM>-<NUM> passes characteristic frequency locations corresponding to the stimulus frequency values. Likewise, as shown in graph <NUM>, the phase of the evoked response signal alternates between high and low values in a periodic manner that is temporally aligned with when electrode <NUM>-<NUM> passes characteristic frequency locations corresponding to the stimulus frequency values.

Diagnostic system <NUM> may direct a display device (e.g., display device <NUM>) to display a graph of the evoked response signal recorded by electrode <NUM>-<NUM>. In some examples, diagnostic system <NUM> may direct the display device to display the graph in substantially real time as the insertion procedure is being performed.

To illustrate, <FIG> shows an exemplary graphical user interface <NUM> that may be displayed by a display device at the direction of diagnostic system <NUM>. As shown, graphical user interface includes graph <NUM> and graph <NUM>. In alternative embodiments, only one of graph <NUM> and graph <NUM> may be displayed within graphical user interface <NUM>.

By displaying a graph of the evoked response signal recorded by electrode <NUM>-<NUM> during the insertion procedure, diagnostic system <NUM> may provide real-time feedback to a user (e.g., a surgeon) performing the insertion procedure. This feedback may be used by the user to ensure proper placement of the electrode lead <NUM> within cochlea <NUM> and/or for any other purpose as may serve a particular implementation.

For example, diagnostic system <NUM> may detect, within a predetermined time period, that an amplitude of the evoked response signal decreases by at least an amplitude threshold amount without a phase of the evoked response signal changing by at least a phase threshold amount. This may indicate a possible occurrence of trauma to cochlea <NUM>. Such trauma may be caused by electrode lead <NUM> penetrating a wall of cochlea <NUM>, inadvertently being placed within a wrong duct of cochlea <NUM>, and/or in any other suitable manner. In response, diagnostic system <NUM> may provide, to the user, a notification indicating the possible occurrence of trauma.

To illustrate, <FIG> shows graphical user interface <NUM> after an amplitude of the evoked response signal decreases without a corresponding change in phase. As shown, a notification <NUM> is included within graphical user interface <NUM>. Notification <NUM> indicates a possible occurrence of trauma. In response to seeing notification <NUM> appear within graphical user interface <NUM>, a user may stop the insertion procedure and/or take other remedial action (e.g., by pulling back the electrode lead outside the cochlea, changing electrode insertion angle, etc.). Any other type of notification (e.g., audible or visible notification) may additionally or alternatively be presented to the user as may serve a particular implementation.

The sequence of decreasingly lower stimulus frequency values described in the examples provided herein are merely exemplary. Additional or alternative stimulus values may be included in the sequence as may serve a particular implementation. In some examples, the initial value included in the sequence is greater than <NUM> and the final value is less than <NUM>. To illustrate, the sequence of decreasingly lower values may include an initial value that is between <NUM> and <NUM>, a second value that is between <NUM> and <NUM>, a third value that is between <NUM> and <NUM>, a fourth value that is between <NUM> and <NUM>, and a final value that is between <NUM> and <NUM>.

As mentioned, diagnostic system <NUM> may additionally or alternatively direct an acoustic stimulation generator to apply acoustic stimulation having a plurality of stimulus frequencies (i.e., concurrently) to a recipient of a cochlear implant during an insertion procedure in which an electrode lead communicatively coupled to the cochlear implant is inserted into a cochlea of the recipient. Diagnostic system <NUM> may direct the cochlear implant to use electrode <NUM>-<NUM> to record a plurality of evoked response signals during the insertion procedure. The evoked response signals each correspond to a different stimulus frequency included in the plurality of stimulus frequencies.

For example, <FIG> illustrates an exemplary configuration in which the acoustic stimulation includes stimulus frequencies of <NUM>, <NUM>, <NUM>, and <NUM>. <FIG> also shows a graph <NUM> of an amplitude of a plurality of evoked response signals <NUM> (e.g., evoked response signals <NUM>-<NUM> through <NUM>-<NUM>) recorded by electrode <NUM>-<NUM> during the lead insertion procedure and a graph <NUM> of a plurality of phase signals <NUM> corresponding to evoked response signals <NUM>. Each evoked response signal <NUM> and phase signal <NUM> correspond to a different stimulus frequency. For example, evoked response signal <NUM>-<NUM> and phase signal <NUM>-<NUM> correspond to <NUM>, evoked response signal <NUM>-<NUM> and phase signal <NUM>-<NUM> correspond to <NUM>, evoked response signal <NUM>-<NUM> and phase signal <NUM>-<NUM> correspond to <NUM>, and evoked response signal <NUM>-<NUM> and phase signal <NUM>-<NUM> correspond to <NUM>.

In practice, graphs <NUM> and <NUM> may be difficult to interpret by a user, especially in real time during an insertion procedure. This is because all of the signals <NUM> and <NUM> are plotted concurrently. Accordingly, diagnostic system <NUM> may plot, by way of a display device, a graph of the evoked response signals in substantially real time as the insertion procedure is being performed by switching between displaying each evoked response signal included in the plurality of evoked response signals such that, at any given time, only a single evoked response that has a highest amplitude compared to other evoked response signals in the plurality of evoked response signals is displayed by the display device. This may result in the same graphs being displayed as are displayed if the acoustic stimulation has only a single stimulus frequency value at any given time, as described above. For example, by switching between displaying each evoked response signal in this manner, graph <NUM> and/or graph <NUM> being displayed by display device, as shown in <FIG>.

<FIG> illustrates an exemplary method <NUM>. The operations shown in <FIG> may be performed by diagnostic system <NUM> and/or any implementation thereof. While <FIG> illustrates exemplary operations according to one embodiment, other embodiments may omit, add to, reorder, and/or modify any of the operations shown in <FIG>.

In operation <NUM>, a diagnostic system directs an acoustic stimulation generator to apply acoustic stimulation having a stimulus frequency to a recipient of a cochlear implant during an insertion procedure in which an electrode lead communicatively coupled to the cochlear implant is inserted into a cochlea of the recipient. Operation <NUM> may be performed in any of the ways described herein.

In operation <NUM>, the diagnostic system directs the cochlear implant to use an electrode disposed on the electrode lead to record an evoked response signal during the insertion procedure, the evoked response signal representing amplitudes of a plurality of evoked responses that occur within the recipient in response to the acoustic stimulation applied to the recipient. Operation <NUM> may be performed in any of the ways described herein.

In operation <NUM>, the diagnostic system incrementally steps, as the electrode lead is inserted into the cochlea, the stimulus frequency through a sequence of decreasingly lower values starting with an initial value and ending with a final value lower than the initial value. Operation <NUM> may be performed in any of the ways described herein.

<FIG> illustrates an exemplary computing device <NUM> that may be specifically configured to perform one or more of the processes described herein. As shown in <FIG>, computing device <NUM> may include a communication interface <NUM>, a processor <NUM>, a storage device <NUM>, and an input/output ("I/O") module <NUM> communicatively connected one to another via a communication infrastructure <NUM>. While an exemplary computing device <NUM> is shown in <FIG>, the components illustrated in <FIG> are not intended to be limiting. Additional or alternative components may be used in other embodiments. Components of computing device <NUM> shown in <FIG> will now be described in additional detail.

In some examples, any of the systems, computing devices, and/or other components described herein may be implemented by computing device <NUM>. For example, storage facility <NUM> may be implemented by storage device <NUM>, and processing facility <NUM> may be implemented by processor <NUM>.

Claim 1:
A system comprising:
a memory (<NUM>) storing instructions (<NUM>);
a processor (<NUM>) communicatively coupled to the memory and configured to execute the instructions to:
direct an acoustic stimulation generator (<NUM>) to apply acoustic stimulation having a stimulus frequency to a recipient of a cochlear implant (<NUM>) during an insertion procedure in which an electrode lead (<NUM>, <NUM>, <NUM>) communicatively coupled to the cochlear implant is inserted into a cochlea (<NUM>, <NUM>, <NUM>) of the recipient;
direct the cochlear implant to use an electrode (<NUM>, <NUM>, <NUM>) disposed on the electrode lead to record an evoked response signal during the insertion procedure, the evoked response signal representing amplitudes of a plurality of evoked responses that occur within the recipient in response to the acoustic stimulation applied to the recipient; and
incrementally step, as the electrode lead is inserted into the cochlea, the stimulus frequency through a sequence of decreasingly lower values starting with an initial value and ending with a final value lower than the initial value, wherein:
the processor is further configured to execute the instructions to determine, while the stimulus frequency has the initial value, that the electrode passes a characteristic frequency location within the cochlea and corresponding to the initial value; and
the incremental stepping of the stimulus frequency comprises decreasing, in response to the determination that the electrode passes the characteristic frequency location, the stimulus frequency from the initial value to a next lower value included in the sequence of decreasingly lower values.