CONFIGURATION OF IMPLANTED DEVICES

Abstract: An arrangement for implanted medical devices in which the implant (20) includes certain parameters (21) stored in memory. Upon initialisation, these parameters are downloaded to the external component (30). This allows for simpler changes to the external device, or for a generic external device to be used. A particular application is to Cochlear implants.

Description: CONFIGURATION OF IMPLANTED DEVICES Field of the Invention The present invention relates to implanted medical devices, for example cochlear implants, which combine an implanted device with an external, continuously linked device to provide the required functionality. Background Art Medical devices of various types operate using an implanted component, and an external unit which is required to be linked to the implanted component, for example by an RF or inductive link, to provide the required functionality. The following discussion will be principally in the context of cochlear implants, but other similar issues arise for devices such as spinal, visual or other neural stimulators, and other medical implant applications. In the case of cochlear implants, the system is generally configured as an external speech processor, and an implanted receiver / stimulator device. The internal device includes an electrode array for providing electrical stimuli to the cochlea, electrical circuitry to generate the stimuli, and a means for receiving signals and power from the external speech processor. One arrangement, generally used in devices manufactured by the applicant, uses an inductive link to transfer power and data between the external speech processor unit and the implanted receiver/stimulator device. For the purposes of this invention however, the precise mechanism used is not presently relevant. Conventionally cochlear implant devices have been arranged such that the implanted unit responds to commands from a compatible processor, but does not store patient specific data or identification codes in such a way so as to exclude the implanted unit responding to any processor unit. In conventional systems the patient specific data and programming is stored in the external speech processor and there is no data retained in the implant when it is powered down. One issue with such devices is that in some situations, for example in a facility for the hearing impaired, it is possible for users to inadvertently swap speech processors. Each speech processor will contain a set of data specific to each individual - for example, speech processing strategies, stimulus coding strategies and electrode mapping parameters. If the wrong speech processor is used for a patient, then the use of the incorrect parameters will cause at best poor speech perception by the user, and at worst may cause pain and discomfort. Present cochlear implant systems do not incorporate mechanisms to prevent such a problem arising. Similarly, if the speech processor is lost or damaged, the only record of the appropriate parameters for the patient is stored at the clinic which provided the programming for the processor. The clinician needs to then access the patients records and identify the implant serial number to initiate a programming session. If this is not readily available, then a new speech processor must be programmed from the beginning, which is a complex and time consuming process. Similar issues arise for other implanted devices which use an external component to provide ongoing data to an implant. With this in mind, one object of the present invention is to provide an implanted device which allows for desired operation of the device through use of a compatible generic external component. A further object of the present invention is a system which prevents inadvertent operation of an implanted medical device with incorrect parameters. Yet a further object of the present invention is a system which allows for a simple process of exchanging external processors and accessing of patient specific data. Summary of the Invention Broadly, the present invention provides a change in the paradigm of where the patient specific data is stored. Instead of the implanted device being essentially undifferentiated and the external processor customised, the implanted device is used to store the user specific parameters, which are downloaded by the external processor each time it is first brought into operational mode. As a consequence, the external processor need not be customised, and in a preferred implementation is essentially a generic device, which is customised by the parameters downloaded from the implant each time it is turned on. Additionally, during operation the external processor is preferably continually checking that it is still connected to the same implant, for example by periodic interrogation of the implant and receiving an expected serial number. This approach allows for the external processor to be customised to the active implant, regardless of which user currently is in possession, subject of course to compatibility of the external processor and the implant. This also allows, for example, simplified use of a replacement external processor. The necessary parameters are carried in a suitable memory device in the implant, and uploaded at the start of operation to the external processor. This may be readily achieved by using the telemetry link which already exists in many available devices. The processor may also detect the type or model of the implant, and so select the appropriate operational mode. Brief Description of Drawings Figure 1 is an illustration of a typical cochlear implant system; Figure 2A illustrates the division of function within a prior art cochlear implant; and Figure 2B illustrates the division of function within a cochlear implant device according to the present invention. Detailed Description The present invention will be explained principally in the context of cochlear implants. However, it will be appreciated by those skilled in the art that the same principle is readily implemented in other applications. Figure 1 illustrates a typical cochlear implant system having an external component, including a speech processor 1 , and an internal component including an implanted receiver and stimulator unit 6. The external component includes a microphone 2. The speech processor is in this illustration constructed and arranged so that it can fit behind the outer ear 11. Alternative versions may be worn on the body. Attached to speech processor 1 is a transmitter coil 3 which transmits the electrical signals to the implanted unit 6 via an RF link 4. The implanted component includes a receiver coil 5 for receiving power and data from transmitter coil 3. A cable 7 extends from the implanted device 6 to the cochlea 12 and terminates in an electrode array 10. The signals thus received are applied by the array 10 to the basilar membrane 8 thereby stimulating the auditory nerve 9. The operation of the device shown in figure 1 is described, for example, in US patent No. 4532930. Thus, the RF link, which is in turn powered by the speech processor 1 , provides power and data to the implanted device 6. The speech processor also processes sound signals received by microphone 2, so as to send appropriate processed audio information or stimulus and/or control commands to the implanted device 6. The precise details of speech processing are not necessary for an understanding of the present invention, and the skilled worker in the art will be aware that many such schemes have been used and proposed. Virtually all such schemes rely on patient specific data. For example, post implantation it is usual for the implanted electrodes in a multi- electrode array to be tested for function, and for the sound percepts which are generated by stimuli to particular electrode pairs to be determined. These electrode specific percepts used in conjunction with a stimulation strategy to generate a patient specific map. Different patients have different speech processing strategies, and different parameters within a given speech processing strategy. Further, each user may have a unique stimulus coding strategy. Other data may also be stored, for example alternative speech processing schemes and the user specific strategy for those schemes, or data of other types. All these data will be discussed as user specific parameters for the purposes of the discussion below, and are well understood by those skilled in the art. Commercially available cochlear implant systems have in some cases a telemetry system in place. This allows for various parameters sensed by the implant to be sent back via the communications link to the speech processor. Conventional telemetry data may include data on the operation of the implant, as well as sensor data to assist in defining stimulus and speech processing strategies and for diagnostics. Figure 2A illustrates the conceptual operation of a conventional device. The user parameters 31 are stored in non-volatile memory in the external processor 30. The external processor 30 communicates via communications link 25 with the implant 20. Instructions as to the electrical stimuli to be delivered are sent to the implant, and telemetry data is sent back from the implant, via communications link 25. Figure 2B illustrates the conceptual approach of the present invention. Implant 20 includes user parameters 21 , and a serial number 22, stored in non-volatile memory. The parameters would be initially set using a programming mode using data derived from clinical and audiological tests, as is conventional. However, instead of this data being stored in the external processor 30, it is stored in the implant. It will be appreciated that the user parameters 21 could be in a coded format to minimise the data required to be downloaded during start-up. The serial number 22 could be implemented in various ways, including the use of a fixed serial number. An alternative would be a value set as a result of a handshake at start up with the external processor, so that the value is changed with each new start-up. Such mechanisms are well known in the communications field, and the exact form of interaction is not crucial. It is important however, that there is some form of on-going check, so that the external processor continues to send signals only when the correct implant is interoperating. The processor 30 according to the present invention includes a volatile memory 32 for storing the user parameters downloaded during the start-up process. This may be strictly a volatile memory, or merely one which is reused. It is highly preferred that this data is not retained by the speech processor.and the processor operates only on data that is downloaded each time it is powered up and recognizes the implant. The external processor 30 also includes code 33 necessary to perform the on-going check of serial number, as discussed above. As can be seen from figure 2, the communications link carries not only telemetry, but also serial number data and, at start up, the user parameters from the implant to the external processor. The link 25 carries processed audio information or stimulus and/or control commands, as well as signals relating to the on-going check of the connection. As it is not simply a master / slave relationship, the external processor and implant need to complete a start up procedure each time the speech processor is turned on. A suitable procedure is as follows: 1. The speech processor is not receiving back telemetry signals, and so it sends an implant interrogation sequence. 2. The implant responds to the interrogation sequence. 3. The speech processor identifies the implant, for example model and number, and requests download of user parameters. 4. The speech processor configures itself according to the user parameters and implant data downloaded. 5. The speech processor starts signal processing and mapping, stimulus and/or command encoding based upon the downloaded data. A "handshake" with the implant is maintained continuously. Step 5 may involve a simple low-rate handshake, for example an acknowledgement sequence sent for example, 100 ms or for the system at a rate low enough to identify when the communication link is broken, but not so low that the system does not recognise that a new device has been swapped. Alternatively, a higher rate handshake, such as a compliance telemetry response in each stimulus frame, could be used. It will be appreciated the present invention can be readily applied to any implanted device required to operate with an external device to provide normal function. It will be apparent to those skilled in the art that variations and additions are possible within the general inventive concept.

Claims: CLAIMS 1. An implantable medical device system, of the type including an implant, an external processor, and a communications link operatively provided between the implant and the external processor, said system being of the type in which parameters specific to a given user or implant are required to be applied in said external processor, and the external processor operatively provides on-going information derived from said parameters to said implant, characterized in that said implant includes memory means storing at least some of said parameters, and said implant is adapted to download said parameters to said processor. 2. An implantable medical device system according to claim 1 , wherein said parameters include parameters specific to the user, and parameters specific to said implant. 3. An implantable medical device system according to claim 2, wherein operatively said communications link is active bi-directionally, so that said implant provides data to said external processor indicating its identity. 4. An implantable medical device system according to claim 1 , wherein said implant is a neural stimulation device. 5. An implantable medical device system according to claim 4, wherein said implant is an auditory neural stimulation device. 6. A medical implant, adapted to operatively communicate using a communications link with an external processor, said external processor operatively providing on-going instructions to said implant, and said processor requiring parameters specific to a given user to generate said instructions, said implant being characterized in that it includes memory means storing at least some of said parameters, and said implant is adapted to download said parameters to said processor. 7. An implant according to claim 6, wherein said parameters include parameters specific to the user, and parameters specific to said implant. 8. An implant according to claim 7, wherein operatively said communications link is active bi-directionally, so that said implant is adapted to provide data to said external processor indicating its identity. 9. An implant according to claim 6, wherein said implant is a neural stimulation device. 10. An implant according to claim 9, wherein said implant is an auditory neural stimulation device. 11. An external processor for use with an implanted medical device, of the type in which a communications link is operatively provided between the implanted medical device and the external processor, said system being of the type in which parameters specific to a given user are required to be applied in said processor, and the external processor operatively provides on-going information derived from said parameters to said implanted medical device, characterized in that said external processor is adapted to receive parameters downloaded from said implant for use in said external processor, said parameters being downloaded when said processor is placed in an operative state. 12. An external processor according to claim 11 , wherein said parameters are not retained in said processor for re-use when said processor is next placed in an operative state. 13. An external processor according to claim 12, said parameters include parameters specific to the user, and parameters specific to said implant. 14. An external processor according to claim 13, wherein operatively said communications link is active bi-directionally, said processor being adapted to receive data from said implant indicating the identity of the implant, and if said information is not received in a predefined manner, said external processor shuts down. 15. An external processor according to claim 11 , wherein the external processor is adapted for use with an implant being a neural stimulation device. 16. An external processor according to claim 15, wherein the external processor is adapted for use with an implant being an auditory neural stimulation device. 17. A method for providing implant or user specific parameters in an implantable medical device system, said system including an exernal processor, on implant, and a communications link between said implant and said external processor, said method including at least the steps of: said processor transmitting an initialisation signal; said implant receiving said initialisation signal; and transmitting from memory a set of parameters; said processor receiving said set, and processing said set so that said parameters are available for operative use. 18. A method according to claim 17, wherein said method further includes periodic signals being transmitted from said implant to said processor, and if a predetermined number of said signals are not received, said processor switches to an inoperative mode. 19. A method according to claim 17, wherein the set of parameters includes one or more of user specific parameters, and implant specific parameter.

Inventors: DALY CHRISTOPHER NEWTON, DALY, CHRISTOPHER, NEWTON
Applicants: COCHLEAR LTD, DALY CHRISTOPHER NEWTON, COCHLEAR LIMITED, DALY, CHRISTOPHER, NEWTON
Application year: 2001
Main classification: A61F11
IPC codes: A61F2, A61F11, A61N1