Recognition of implantable medical device

Abstract

Controlling the interaction between an external device and an implanted device, including a method of controlling interaction between an external device and an implanted device, the method including at least the steps of: establishing communications between the implanted device and the external device; the external device determining an identification of the implant and comparing the identification with identifications in a stored list; if the device matches one of said identifications, then using a corresponding set of operating parameters to interact with said implant; and otherwise, not interacting with said device.

Description

BACKGROUND

1. Field of the Invention

The present invention relates to implantable medical devices, and more particularly, to recognition of implantable medical devices.

2.Related Art

Implantable hearing prostheses provide the benefit of hearing to individuals suffering from severe to profound sensorineural hearing loss. Sensorineural hearing loss is due to the absence or destruction of the hair cells in the cochlea which transduce acoustic signals into nerve impulses. An implantable hearing prosthesis essentially simulates the cochlear hair cells by delivering electrical stimulation to the auditory nerve fibers. This causes the brain to perceive a hearing sensation resembling the natural hearing sensation.

The present invention is particularly concerned with situations where a user, patient or recipient, “recipient” herein has an external processing device that communicates with an implanted device. For example, in a modern, conventional cochlear implant, an external speech processor transmits power and data to the implanted device via an inductive coil arrangement. The implanted device includes an electrode array to deliver the desired electrical stimuli to the cochlea of the recipient.

Once implanted, the implant system is typically adjusted to suit the specific needs of the recipient. As the dynamic range for electrical stimulation is relatively narrow and varies across recipients and electrodes, there is a need to individually tailor the characteristics of electrical stimulation for each recipient. This procedure, often referred to as “fitting,” “programming,” “mapping” (“mapping” herein) involves measuring and controlling the amount of electrical current delivered to the cochlea. Typically, a clinician, audiologist or other medical practitioner (generally and collectively referred to as “audiologist” herein) uses interactive software and computer hardware to create individualized programs, commands, data, settings, parameters, instructions, and/or other information (generally and collectively referred to as a “MAP” herein) that define the specific characteristics used to generate the electrical stimulation signals presented to the electrodes of the implanted electrode assembly. It is increasingly common for recipients to have a cochlear implant for each ear, which is commonly known as bilateral implantation. The advantages of bilateral implantation vary from recipient to recipient, and may include improved speech perception, and the ability to localize sounds. However, due to differences in the anatomy and physiology of recipients, and in the need to precisely place the electrode array, there will almost always be differences in the map between the left and right ears. The recipient will have two speech processor devices, each operating according to a different MAP. The speech processor devices are typically identical in appearance, and may inadvertently be swapped. This is a particular issue for very young and elderly recipients, as well as those with conditions such visual impairment. The use of the incorrect speech processor device will at best lead to reduced speech perception, as the incorrect MAP is applied, and potentially to pain for the recipient as excessive stimulation values are utilized for that ear.

SUMMARY

In a broad form, the present invention provides multiple set of operating parameters (maps or the like) within each external device, each set being associated with an identified implant. Before the external device begins to transmit stimulation or other operational data to the implant, it determines the identity of the implant, and then uses the corresponding set.

According to one aspect, the present invention provides a method of controlling interaction between an external device and an implanted device, the method including at least the steps of:

establishing communications between the implanted device and the external device;

the external device determining an identification of the implant and comparing the identification with identifications in a stored list;

if the device matches one of said identifications, using a corresponding set of operating parameters to interact with said implant; and

otherwise, not interacting with said device.

According to another aspect, the present invention provides an external device adapted to interact with an implanted device, the external device being adapted to detect an identification from an implanted device, determine if the identification corresponds to one of a plurality of identifications, and if the identification does correspond, utilise a stored set of operating parameters corresponding to said identification.

According to another aspect, the present invention provides an external hearing device adapted to interact with an implanted device, the external device being able to be operatively positioned to interact with either a left ear or right ear implanted device, said external device including sensor means operatively adapted to detect whether the external device is positioned to interact with the left ear or the right ear implanted device, and in response to said sensor utilise a stored set of operating parameters corresponding to the left ear or the right ear implanted device.

The present invention accordingly provides an arrangement whereby, for the bilateral implantee, it does not matter which SP is selected for which ear—both can store the map for each ear, and deliver the correct stimulation instructions for the respective implant. If the implant is not identified, the SP will not operate. The invention can be applied in any form of implanted device where multiple external devices may be inadvertently associated with the wrong implanted device.

The invention is also applicable to implanted devices where the external device may only be periodically connected, for example, a totally implantable auditory prosthesis.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described with reference to the accompanying figures, in which:

FIG. 1 illustrates schematically a bilateral implant situation;

FIG. 2 is a conceptual block diagram of the operation of one implementation of the present invention;

FIG. 3 is a flowchart illustrating the operation of the required software of one implementation;

FIG. 4 illustrates the general operation of a cochlear implant system;

FIG. 5 illustrates the operation of another implementation of the identification system; and

FIG. 6 is a graph illustrating how the characterisation of a predefined subset of parameters can be used to differentiate between two similar implants.

DETAILED DESCRIPTION

The present invention is capable of implementation in any desired type of implantable device which interacts with an external device. For example, the present invention may be used in conjunction with any acoustic or electrical auditory device, such as a middle ear implant, intracochlear array implant, brain stem implant, implanted acoustic device or any combination, for example combined electrical and acoustic stimulation. The external device may be continuously, intermittently or occasionally in communication with the implanted device. The present invention may also be used in non-auditory applications where a component is implanted and interacts with an external device. However, embodiments of the invention are described with reference to an embodiment in a cochlear implant system.

FIG. 1 illustrates conceptually a recipient 10 having an intracochlear device 11, 12 implanted in each ear 13, 14, respectively. For each implant 11, 12, a corresponding external device 17, 18 is required. The external device incorporates one or more microphones, batteries, processor and the necessary software to process sound signals and transmit them via coils 15, 16 to the implanted device.

A more detailed description of typical external and implant devices of a cochlear implant is provided in FIG. 4. It is noted that such devices are in widespread commercial use, and well understood by those skilled in the art, so that only a general overview of their structure and operation will be provided. Moreover, various structural variations and alternatives exist, as will be well known to those skilled in the art.

FIG. 4 illustrates an overview of the components of one form of implantable hearing prosthesis, a cochlear implant. The external component of the cochlear implant, generally indicated as 142, includes a behind the ear (BTE) device 116, designed to sit behind the pinna 122. This houses the required electronics and software (not shown), and batteries to power the external component as well as transfer power to the implanted device 144. BTE device 116 is connected via a lead 118 to the antenna transmitter coil 106, which is generally disc shaped and includes housing 108 for the coil itself (not shown). A magnet 110 is provided to assist in correctly locating the antenna transmitter coil 106 relative to the implanted device, to optimize efficiency of power and data transfer.

The implanted component 144 includes receiver/stimulator unit 112 and electrode lead 130. Receiver stimulator unit 112 includes a sealed electronics package 128, and a coil 124 to receive the RF signals sent from transmitter coil 106. There may also be a back transmission mechanism, to transfer telemetry data to the external device 142. A magnet 140 provides assistance in alignment of the transmission coil 106. Electrode lead 130 passes stimuli to the electrodes 134 for delivery within the cochlea 132, so as to produce a neural response in auditory nerve 138.

In operation, the electronics within the BTE device 116 convert sound detected by microphone(s) 120 into a coded signal. The external antenna coil 106 transmits the coded signals, together with power, to the receiver/stimulator unit 112 via a radio frequency (RF) link.

Once implanted, the parameters for stimulation are typically adjusted to suit the specific needs of the recipient. As the dynamic range for electrical stimulation is relatively narrow and varies across recipients and electrodes, there is a need to individually tailor the characteristics of electrical stimulation for each recipient. Audiology measurements may be used to establish the useful range for each electrode, and such parameters can be stored within the recipient's BTE device 116 for continual use. As noted, this procedure is often referred to as “mapping” and is the term commonly given to the process of measuring and controlling the amount of electrical current delivered to each electrode, as well as selecting which electrodes to stimulate corresponding to the respective sound signal. Other operational issues which may differ between ears include the speech processing strategy or parameters of that strategy, when to switch between different strategies, and other functions and parameters. Different “MAPS” may be applied in different situations/environments such as home, car, classroom, theatre etc, so each external device may store many maps. It will be appreciated that the present invention is applicable to the selection of all such functions and parameters as may be customizable for each patient or implant according to the particular requirements and options of the implant and external device in question.

Importantly for the present invention, the MAP for each implant will differ due to variations in the patient's anatomy and physiology, and in the precise placement of the electrode array, there will almost always be differences in the MAP between the left and right ears.

FIG. 2 illustrates one implementation of the present invention. Microphone(s) 120 receives ambient sound signals which are then processed by a digital signal processor (DSP) 31. The signals are processed according to any one of the known speech processing strategies to produce a set of signals which are intended as the basis for stimulation. The signals are then converted into specific sets of stimuli for specific electrodes at specific times and for specific amplitudes. The set of MAPS (that is, the MAPS corresponding to different environments) for the appropriate implanted component 144 is required to perform this process. According to this implementation, multiple sets of MAPS are stored, each set of MAPS corresponding to a particular implant identifier. Embodiments of the implant identifier are described in further detail below. Module 33 selects the appropriate MAP, and other parameters as required, based on the implant ID identified by module 33. Once the stimuli have been determined, the appropriate coded signals are transmitted via the bidirectional communications interface 34 to interface 44 of implanted component 144. From the perspective of implanted component 144, it is not necessary to change the mode of operation. The receiver/stimulator 41 receives the signal, converts it to a set of stimuli, for example using an optional digital signal processor (DSP) 42, and sends the stimuli to electrodes 134.

Implanted component 144 may contain a module to provide the require ID signal. This may be any arrangement capable of providing an appropriate ID signal which is not shared with other implants. It is ideally unique, but need not be. One option would be to send a specific electrical signal after power up or after detection that the external device is in operation. This type of ID is used in some commercially available devices. Any alternative form of implant identification can be employed with the present invention.

One alternative would be to provide some form of specific automatic identification of which side of the recipient's head an external device, such as a BTE device, has been placed. This could be done by the use of a proximity or thermal sensor such as is shown as reference 200 on FIG. 4. In the thermal case, the sensor will operatively either be placed near adjacent the user's head, or facing away, with a substantial difference in heat. This allows the appropriate left or right map to be selected. However, this does not prevent the recipient from using a completely wrong device, as may occur in a classroom situation.

Another alternative would be to provide a source localization algorithm on the microphone in external device 17, 18. If the device is on the left ear, most sound will come from the right side and vice versa allowing determination of which ear the device has been placed and therefore allowing the appropriate selection of left or right map.

If no sensor is working and the implanted component is one that cannot transmit internal voltages, external device 17, 18 may still have MAPS for the left and right which the recipient 10 may select themselves, for example by pressing a selection button at start-up.

An approach suitable for use for an implant which has not been designed to produce a specific ID signal will be described with reference to FIGS. 5 and 6. The general approach is in principle applicable to any implant which is capable of sending the required parameters via a telemetry system to the external device. The principle of this approach is that each device has internal operating values that vary from device to device. The present example uses certain internal voltages which can be output using existing telemetry arrangements, and which as a statistical measure allow for accurate identification of particular implants. However, any suitable subset of internal parameters could be used as may be appropriate for a particular implant device.

FIG. 5 illustrates the statistical basis used. In any real system, manufacturing variations result in various parameters having a normally distributed range of values about a nominal value. The parameters are required to fall within minimum and maximum ranges to be acceptable from a quality perspective. However, some of these values are relatively constant over time, and are a specific value of that parameter for the particular implant. When a number of these parameters are considered separately, then if there is a sufficient overall match, the implant can be sufficiently identified.

The choice of the suitable subset of parameters for use in device identification will depend on device design and the normal variance of the parameters. Most active implantable devices have a range of internal parameters that may be suitable, such as regulated supply voltages, reference voltages and programmable currents.

For example, referring to FIGS. 6A and 6B, the following parameters might be selected:

Parameter 1=Regulated analogue supply voltage (Vdda)

Parameter 2=Regulated digital supply voltage (Vddd)

Parameter 3=Reference voltage (Vref)

Parameter 4=Voltage measured across internal load for stimulus level A1

Parameter 5=Voltage measured across internal load for stimulus level A2, where the value of the internal load resistor and the two current levels A1 and A2 will vary between implants.

Parameters 6 to 10=Parameters 1 to 5 but measured using a different voltage measurement range. The gains of the different measurement ranges will vary between implants, for example due to the non-linearity of the voltage amplifier in each implant.

Alternatively, other measurements such as the physiological properties of the ear, eg some aspect of the neural response with the implant or the impedance of the electrodes in the cochlea, can be used as parameters for use in device identification.

FIGS. 6A and 6B show the value of various voltages, plotting the parameter value against the parameter. It can be seen that each implant has a specific signature which is different from other implants, so as to provide a specific identification of a particular implant. It is possible that another implant could have the set of parameter values, but this is sufficiently unlikely that that the practical risk of inadvertent connection may be disregarded.

One implant will now be described. For each implant (at the time of first surgery, or first fitting) the subset of parameters listed above is measured and stored as internal ID pattern. To improve the reliability of the measurement the parameters can be averaged, which also serves to minimize the statistical variance.

Every time the speech processor is placed on an implant the same subset of parameters is measured. The ID recognition test passes if and only if all of the parameters measured lie within, say T*sd of the value of that parameter in the internal ID pattern. The parameter T is a threshold that determines the trade-off between the sensitivity and specificity of the test: a large value of T means that we have a very low probability of wrongfully rejecting the correct implant (false negative rate), a small value of T means we have a low probability of wrongfully accepting the wrong implant (false positive rate). The parameter sd in the test criteria is the standard deviation of each parameter on repetitive measurement on the same implant, which is around 0.6 for the Freedom implant. Trials have indicated that T=3.25 provides acceptable false negative and false positive outcomes. It will be understood that for each type of implant, different parameters may be appropriate, and different values for T and standard deviation will need to be applied. The standard deviation may be different for different parameters.

It will be appreciated that this is a process which will differ for different external devices and a suitable set of identification parameters can be selected as has been described.

In practice, every time the speech processor is switched on stimulation should be halted until an implant is detected. Also, when a coil-off condition occurs for longer than 3 seconds, stimulation should halt until the implant is detected again. Before starting stimulation (at switch on, or after coil-off the test should pass first.

When an implant is (re)detected, the above mentioned parameters are measured using 50 averages. This dataset is labelled D(1) . . . D(n). The speech processor should check that for I=1 . . . n:R(i)+T*sd<T(i)>R(i)−T*sd

When the test passes, stimulation can start. If the test fails, it is repeated to rule out statistical errors. When after five (5) tests, the test still fails the speech processor should refrain from stimulating and give a helper message on the LCD display of the implant.

It may be desirable in some applications that the user be able to overrule the error and start stimulation by a specific button press combination to manually select the correct operating program for the implant.

It will be understood that a different process may be used to implement the invention if desired, and that alternative processes are likely for different external devices.

FIG. 3 is a flow chart illustrating the process which can be employed in the BTE device 116 software. It is noted that it would be possible to perform the ID process primarily from the implant itself, however, in general it is preferred to minimise the complexity and processing load for the implanted device.

FIG. 3 shows the step 50 by which the identifier is detected. This will obviously differ depending upon the identifier used. Once the identifier is located, at step 51, the appropriate parameters and mode of operation will be selected, corresponding to the implant identified. It will be appreciated that the exact set of parameters will depend upon the type of implant, and apart from the map as such, may include other operating parameters, mode of stimulation, type of speech processing algorithm, and such other parameters as are desired.

It is preferred that the identification process occur as often as required to ensure safe operation. This may include, for example, at power on of the BTE device, or whenever communications between the implant and BTE are interrupted for more than some predetermined period, for example 3 seconds. In each case, the ID process should be completed before stimulation occurs.

Once the parameters are determined at step 51, operation of the device can be initiated. At step 53, operation can continue until conditions require the ID to be re-checked, as noted above.

It will be understood that the present invention may be applied to include more than two sets of operating parameters. For example, in a household where there are multiple implant users, all the SP devices could be loaded with the parameters for the implants of everyone in the house. This may be of particular benefit with small children. The present invention further provides flexibility for the user. If one SP device is not operating, for example due to low battery power, the remaining device can be used for the better ear.

Further features and advantages of the present invention may be found in International Application No. PCT/AU2007/000142 entitled “IMPLANT ID RECOGNITION”, filed on Feb. 9, 2007, which claims priority from Australian Provisional Patent Application No. 2006900628, filed on Feb. 10, 2006, which are hereby incorporated by reference.

It will be appreciated that any other suitable identification process can be used in accordance with the present invention. Variations and additions can be readily added as will be apparent to those skilled in the art.

Claims

1. An external hearing device adapted to interact with an implanted internal device, the external device being able to be operatively positioned to interact with either a left ear or right ear implanted device, said external device including a detector operatively adapted to detect whether the external device is positioned to interact with the left ear or the right ear internal device, and in response to said detection, select and utilize a stored set of operating parameters corresponding to the left ear or the right ear internal device to allow the external device to operate with the internal device.

2. The external device according to claim 1, wherein the internal device is a cochlear implant and the external device is a speech processor.

3. The external device according to claim 1, wherein the detector includes one or more of a proximity sensor, a thermal sensor or a source localization algorithm stored in the external device.

4. The external device according to claim 1, wherein the operating parameters are selected from a group including one or more of an electrode map including stimulation levels, selection of electrodes to stimulate, speech processing strategy or algorithm, parameters of the speech processing strategy, or when to switch between different speech processing strategies.

5. The external device according to claim 1, wherein the external device is configured to allow a user to manually select whether the set of operating parameters corresponding to the left ear or the right ear internal device are utilized by the external device.

6. The external device according to claim 1, further comprising a display, wherein the display is configured to display a message indicating at least the internal device that the external device is interacting with.

7. The external device according to claim 1, wherein the detector is configured to determine at least one identifier of the left ear or the right ear internal device.

8. The external device according to claim 7, wherein the identifier is a transmitted identification signal.

9. The external device according to claim 7, wherein the identifier is determined from a set of measured parameters related to one or more of either the internal device and physiological properties of the left ear or the right ear internal device.

10. The external device according to claim 7, wherein the identifier is an identification tag or device operating independently of the normal communication path between the left ear or the right ear internal device and the external device.

11. The external device according to claim 7, wherein the detector is configured to compare the identifier of the left ear or right ear internal device to a list of known identifiers to confirm that the internal device is known.

12. The external device according to claim 11, wherein the detector is configured to select and utilize the set of operating parameters stored on the external device, the operating parameters corresponding to the internal device, and enabling the external device to operate with the internal device based on the comparison of the identifier of the left ear or right ear internal device to the list of known identifiers.

13. The external device according to claim 1, wherein the operating parameters are selected from a group including one or more of an electrode map including stimulation levels, selection of electrodes to stimulate, speech processing strategy or algorithm, parameters of the speech processing strategy, or when to switch between different speech processing strategies.

14. The external device according to claim 1, wherein the external device automatically selects a set of operating parameters to be utilized by the external device.

15. The external device according to claim 1, wherein the detector is configured to select and utilize the set of operating parameters from a plurality of operating parameter sets, wherein each operating parameter set of the plurality of operating parameter sets corresponds to a particular internal device.

16. The external device according to claim 1, wherein the external device is a behind-the-ear (BTE) external device.

17. The external device according to claim 11, wherein the detector is configured to periodically determine a new identifier and compare the new determined identifier to the list of known identifiers to confirm that the identifier is known.

18. The external device according to claim 7, wherein the detector is configured to terminate operation of the external device if the identifier is determined not to be known.

19. A method for operating an external device with an implanted device implanted in a recipient of the implanted device, comprising: establishing communications between the implanted device and the external device;determining, by the external device, a feature of the implanted device;based on an analysis of the determined feature, enabling the external device to operate with the implanted device; andselecting and utilizing, by the external device, a set of operating parameters from among a plurality of sets of operating parameters stored in the external device, the operating parameters corresponding to particular operating parameters for use with implanted device, and using those parameters during operation with the implanted device to cause the implanted device to stimulate tissue of the recipient.

20. The method of claim 19, wherein: the feature of the implanted device is a feature statistically unique to the implanted device.

21. The method of claim 19, wherein: the feature of the implanted device is an identification of the implanted device.

22. The method of claim 19, further comprising: comparing, by the external device, the identification of the implanted device to a list of known identifiers, which comparing corresponds to the analysis.

23. The method of claim 19, wherein the sets of operating parameters of the plurality of sets of operating parameters correspond respective different maps for different ears of the recipient, wherein the external device is an external device of a hearing prosthesis.

24. The method of claim 23, wherein the external device is a behind the ear device configured to be worn on a left ear of the recipient and configured to be worn on a right ear of the recipient.

25. A method for operating an external device with an implanted device implanted in a recipient of the implanted device, comprising: placing the external device on a side of a head of the recipient;automatically identifying, by the external device, indicia indicative of which side of the head the external device has been placed; andbased on the action of identifying, operating the external device using operating parameters particular for the side of the head the external device has been placed.

26. The method of claim 25, further comprising: placing the external device on another side of the head of the recipient opposite the side of the head of the recipient;automatically identifying a second time, by the external device, second indicia indicative of which side of the head the external device has been placed when placed on the another side of the head of the recipient; andbased on the action of identifying a second time, operating the external device using second operating parameters particular for the another side of the head the external device has been placed, which second operating parameters are different from those for the side of the head the external device had previously been placed.

27. The method of claim 26, further comprising: after placing the external device on the another side of the head of the recipient opposite the side of the head of the recipient, placing a second external device on the side of the head of the recipient;automatically identifying a third time, by the second external device, indicia indicative of which side of the head the second external device has been placed; andbased on the action of identifying a third time, operating the second external device using operating parameters particular for the side of the head the external device has been placed while also operating, based on the action of identifying a second time, the external device using the second operating parameters particular for the another side of the head the external device has been placed.

28. The method of claim 25, wherein the recipient is a bilateral implantee of a hearing prosthesis system, and the external device is one of two separate external devices configured so that it does not matter which of the external devices is placed on which side of the head, and wherein the hearing prosthesis system applies respective different maps for respectively different ears of the recipient when evoking hearing percepts using the two separate external devices.

29. The method of claim 25, wherein: the implant has not been designed to produce a specific implant ID signal.

30. The method of claim 25, wherein: the action of automatically identifying which side of the head the external device has been placed is executed based on latent variables unrelated to the implanted device.

31. The method of claim 25, wherein: the action of automatically identifying which side of the head the external device has been placed is executed based on telemetric data from the implanted device.

32. The method of claim 25, wherein: the action of automatically identifying indicia indicative of which side of the head the external device has been placed is executed based on telemetric data from the implanted device.

33. An external hearing device, the external device being configured to be respectively operatively positioned at a first position to interact with a left ear implant and operatively positioned at a second position to interact with a right ear implant, said external device configured to detect whether the external device is positioned to interact with the left ear implant as opposed to the right ear implant, said external device configured to detect whether the external device is positioned to interact with the right ear implant as opposed to the left ear implant, and in response to said detection, utilize a stored set of operating parameters already present before the detection in the external device corresponding to the left ear implant if the detection indicates that the external device is position to interact with the left ear implant, and utilize a stored set of operating parameters already present before the detection in the external device corresponding to the right ear implant if the detection indicates that the external device is position to interact with the right ear implant.

34. The external hearing device of claim 33, wherein the external device includes, to detect the positioning, at least one of: a sensor that is configured to detect body heat;a sensor that is configured to detect proximity;a source localization algorithm; orlogic that compares a received feature of the left ear implant and/or a received feature of the right ear implant to data stored in the hearing device.

35. The external hearing device of claim 33, wherein: the external hearing device is configured to prevent operation with an implant that is not an approved implant.

36. The external hearing device of claim 33, wherein: the external device is a behind-the-ear (BTE) device configured to be worn behind a left ear of the recipient and configured to be worn behind the right ear of the recipient.

37. The external hearing device of claim 33, wherein: the external device is configured to receive telemetric data from the implant and evaluate such to detect whether the external device is positioned to interact with the right ear implant as opposed to the left ear implant, and visa-versa.

38. The external hearing device of claim 33, wherein the external device includes, to detect the positioning, at least one of: a sensor that is configured to detect body heat;a sensor that is configured to detect proximity; ora source localization algorithm.