Method and system for artefact mitigation of a neural response
There is provided a method and implantable device for controlling a neural stimulus, the neural stimulus being defined by an artefact mitigation status. The method comprises generating a first neural stimulus for delivery to neural tissue, sensing a first signal subsequent to the first neural stimulus, generating a second neural stimulus for delivery to the neural tissue, and sensing a second signal subsequent to the second neural stimulus. The method further comprises determining an artefact mitigation measure (AMM) effect level based on the first sensed signal and the second sensed signal, and setting, in response to comparing the AMM effect level with an AMM effect threshold, the artefact mitigation status of a third neural stimulus to active.
1 . A method of controlling delivery of neural stimuli, the delivery being defined by an artefact mitigation status, the method comprising:
generating a first neural stimulus for delivery to neural tissue;
sensing a first sensed signal subsequent to the first neural stimulus;
generating a second neural stimulus for delivery to the neural tissue;
sensing a second sensed signal subsequent to the second neural stimulus;
determining an artefact mitigation measure (AMM) effect level based on the first sensed signal and the second sensed signal, the AMM effect level comprising a measure of an effect of an artefact mitigation measure on an artefact component of the first sensed signal or the second sensed signal; and
setting, in response to comparing the AMM effect level with an AMM effect threshold, the artefact mitigation status of a third neural stimulus to active.
2 . The method of claim 1 , further comprising generating the third neural stimulus for delivery to the neural tissue according to the artefact mitigation status.
3 . The method of claim 1 , wherein the artefact mitigation status of the first neural stimulus is active, and the artefact mitigation status of the second neural stimulus is inactive.
4 . The method of claim 1 , wherein the first neural stimulus is generated at supra-threshold intensity and the second neural stimulus is generated at supra-threshold intensity.
5 . The method of claim 1 , further comprising repeating generating the first neural stimulus and sensing the first sensed signal to generate a plurality of first sensed signals before determining the AMM effect level.
6 . The method of claim 1 , further comprising repeating generating the second neural stimulus and sensing the second sensed signal to generate a plurality of second sensed signals before determining the AMM effect level.
7 . The method of claim 1 , wherein determining the AMM effect level comprises:
determining an artefact-to-evoked compound action potential (ECAP) ratio of the first sensed signal;
determining an artefact-to-ECAP ratio of the second sensed signal; and
comparing the artefact-to-ECAP ratio of the first sensed signal to the artefact-to-ECAP ratio of the second sensed signal.
8 . The method of claim 7 , wherein determining the artefact-to-ECAP ratio of the first sensed signal comprises applying basis element signal separation to the first sensed signal.
9 . The method of claim 7 , wherein determining the artefact-to-ECAP ratio of the first sensed signal comprises fitting a growth curve model to the first sensed signal.
10 . The method of claim 7 , wherein determining the artefact-to-ECAP ratio of the first sensed signal comprises fitting an artefact-aware growth curve model to the first sensed signal.
11 . The method of claim 1 , wherein the first neural stimulus is generated at sub-threshold intensity, and the second neural stimulus is generated at sub-threshold intensity.
12 . The method of claim 1 ,
wherein the first neural stimulus is defined by a first stimulus electrode configuration defining a first subset of stimulus electrodes from a plurality of stimulus electrodes of an electrode array, and
wherein the second neural stimulus is defined by a second stimulus electrode configuration defining a second subset of stimulus electrodes from the plurality of stimulus electrodes of the electrode array,
the first subset differing from the second subset.
13 . The method of claim 1 , further comprising, in response to the artefact mitigation status being active, controlling an electrical condition of the neural tissue.
14 . The method of claim 13 , wherein controlling an electrical condition of the neural tissue comprises:
providing a plurality of electrodes including at least one nominal feedback sense electrode and at least one nominal compensation electrode, the electrodes being positioned proximate to the neural tissue and being in electrical contact with the neural tissue;
connecting a feedback signal from the feedback sense electrode to an input of a feedback amplifier, and referencing the amplifier to a desired electrical value; and
connecting an output of the feedback amplifier to the compensation electrode such that the feedback amplifier drives the neural tissue via the compensation electrode in a feedback arrangement which seeks to drive the feedback signal to the desired electrical value.
15 . The method of claim 14 , wherein the desired electrical value is electrical ground referenced to a patient ground electrode distant from the feedback sense electrode.
16 . An implantable device for controllably delivering neural stimuli, the delivery being defined by an artefact mitigation activation status, the device comprising:
a stimulus source configured to generate neural stimuli to be delivered via one or more stimulus electrodes of an electrode array to neural tissue;
measurement circuitry configured to sense signals of the neural tissue via one or more measurement electrodes of the electrode array subsequent to respective neural stimuli; and
a controller configured to:
control the stimulus source to generate a first neural stimulus for delivery to the neural tissue;
sense, by the measurement circuitry, a first sensed signal of the neural tissue, subsequent to the first neural stimulus;
control the stimulus source to generate a second neural stimulus for delivery to the neural tissue;
sense, by the measurement circuitry, a second sensed signal of the neural tissue, subsequent to the second neural stimulus;
determine an AMM effect level based on the first sensed signal and the second sensed signal, the AMM effect level comprising a measure of an effect of an artefact mitigation measure on an artefact component of the first sensed signal or the second sensed signal; and
set, in response to comparing the AMM effect level with an AMM effect threshold, the artefact mitigation status of a third neural stimulus to active.
17 . The device of claim 16 , wherein the controller is further configured to control the stimulus source to generate the third neural stimulus for delivery to the neural tissue according to the artefact mitigation status.
18 . The device of claim 16 , further comprising the electrode array, the electrode array comprising a plurality of electrodes including the one or more stimulus electrodes and the one or more measurement electrodes.
19 . The device of claim 16 , wherein the artefact mitigation status is defined by an artefact mitigation configuration setting of the implantable device.
20 . The device of claim 16 , wherein the controller is configured to, in response to the AMM effect level exceeding the AMM effect threshold, set the artefact mitigation status to active.
21 . A neuromodulation system comprising:
an implantable device for controllably delivering neural stimuli, the delivery being defined by an artefact mitigation activation status, the device comprising:
a stimulus source configured to generate neural stimuli to be delivered via one or more stimulus electrodes of an electrode array to neural tissue;
measurement circuitry configured to sense signals of the neural tissue via one or more measurement electrodes of the electrode array subsequent to respective neural stimuli; and
a controller configured to control the stimulus source to generate the neural stimuli; and
a processor configured to:
instruct the controller to control the stimulus source to generate a first neural stimulus for delivery to the neural tissue;
instruct the measurement circuitry to sense a first sensed signal of the neural tissue, subsequent to the first neural stimulus;
instruct the controller to control the stimulus source to generate a second neural stimulus for delivery to the neural tissue; and
instruct the measurement circuitry to sense a second sensed signal of the neural tissue, subsequent to the second neural stimulus;
determine an AMM effect level based on the first sensed signal and the second sensed signal, the AMM effect level comprising a measure of an effect of an artefact mitigation measure on an artefact component of the first sensed signal or the second sensed signal; and
set, in response to comparing the AMM effect level with an AMM effect threshold, the artefact mitigation status to active.
22 . The neuromodulation system of claim 21 , further comprising the electrode array, the electrode array comprising a plurality of electrodes including the one or more stimulus electrodes and the one or more measurement electrodes.
23 . The neuromodulation system of claim 21 , wherein the artefact mitigation status is defined by an artefact mitigation configuration setting of the implantable device.
24 . The neuromodulation system of claim 21 , wherein the processor is configured to, in response to the AMM effect level exceeding the AMM effect threshold, set the artefact mitigation status to active.
25 . The neuromodulation system of claim 21 , wherein the processor is part of the implantable device.
26 . The neuromodulation system of claim 21 , further comprising an external computing device in communication with the implantable device.
27 . The neuromodulation system of claim 26 , wherein the processor is part of the external computing device.
28 . A method of controlling delivery of neural stimuli, the delivery being defined by an artefact mitigation status, the method comprising:
determining an impedance of a recording electrode;
determining an impedance of a reference electrode;
determining an expected artefact level based on the impedance of the recording electrode and the impedance of the reference electrode;
setting, in response to comparing the expected artefact level with a threshold artefact level, the artefact mitigation status of neural stimuli to active; and
generating the neural stimulus for delivery to neural tissue according to the artefact mitigation status.
29 . The method of claim 28 , wherein the expected artefact level comprises an expected artefact magnitude.
30 . The method of claim 29 , wherein the threshold artefact level comprises a threshold artefact magnitude.
31 . The method of claim 28 , wherein the expected artefact level comprises an impedance difference between the impedance of the recording electrode and the impedance of the reference electrode.
32 . The method of claim 31 , wherein the threshold artefact level comprises a threshold impedance difference.
33 . The method of claim 28 , wherein determining the expected artefact level is further based on an input capacitance of an amplifier to which the recording electrode and the reference electrode are connected.
34 . An implantable device for controllably delivering neural stimuli, the delivery being defined by an artefact mitigation activation status, the device comprising:
a stimulus source configured to generate neural stimuli to be delivered via one or more stimulus electrodes of an electrode array to a neural tissue;
measurement circuitry configured to sense signals of the neural tissue via one or more measurement electrodes of the electrode array subsequent to respective neural stimuli; and
a controller configured to:
determine an impedance of a recording electrode of the one or more measurement electrodes;
determine an impedance of a reference electrode of the one or more measurement electrodes;
determine an expected artefact level based on the impedance of the recording electrode and the impedance of the reference electrode; and
set, in response to comparing the expected artefact level with a threshold artefact level, the artefact mitigation status of neural stimuli to active.
35 . The device of claim 34 , wherein the controller is further configured to control the stimulus source to generate a neural stimulus for delivery to the neural tissue according to the artefact mitigation status.
36 . A neuromodulation system comprising:
an implantable device for controllably delivering neural stimuli, the delivery being defined by an artefact mitigation activation status, the device comprising:
a stimulus source configured to generate neural stimuli to be delivered via one or more stimulus electrodes of an electrode array to neural tissue;
measurement circuitry configured to sense signals of the neural tissue via one or more measurement electrodes of the electrode array subsequent to respective neural stimuli; and
a controller configured to control the stimulus source to generate the neural stimuli; and
a processor configured to:
determine an impedance of a recording electrode of the one or more measurement electrodes;
determine an impedance of a reference electrode of the one or more measurement electrodes;
determine an expected artefact level based on the impedance of the recording electrode and the impedance of the reference electrode; and
set, in response to comparing the expected artefact level with a threshold artefact level, the artefact mitigation status of neural stimuli to active.
37 . The neuromodulation system of claim 36 , wherein the controller is further configured to control the stimulus source to generate a neural stimulus for delivery to the neural tissue according to the artefact mitigation status.
38 . The neuromodulation system of claim 36 , wherein the processor is part of the implantable device.
39 . The neuromodulation system of claim 36 , further comprising an external computing device in communication with the implantable device.
40 . The neuromodulation system of claim 39 , wherein the processor is part of the external computing device.