WO2001089629A1 - Sacral root stimulating system by means of a radio-frequency powered implant - Google Patents

Sacral root stimulating system by means of a radio-frequency powered implant Download PDF

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Publication number
WO2001089629A1
WO2001089629A1 PCT/ES2001/000213 ES0100213W WO0189629A1 WO 2001089629 A1 WO2001089629 A1 WO 2001089629A1 ES 0100213 W ES0100213 W ES 0100213W WO 0189629 A1 WO0189629 A1 WO 0189629A1
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WO
WIPO (PCT)
Prior art keywords
implant
stimulation
portable
current
external unit
Prior art date
Application number
PCT/ES2001/000213
Other languages
Spanish (es)
French (fr)
Inventor
David MARÍN LOZANO
Isaac MARTÍNEZ SABATÉ
Enrique CALDERÓN OLIVERAS
Original Assignee
Consejo Superior De Investigaciones Científicas
VILLA SANZ, Rosa, María
Aguilo Llobet, Jorge
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Application filed by Consejo Superior De Investigaciones Científicas, VILLA SANZ, Rosa, María, Aguilo Llobet, Jorge filed Critical Consejo Superior De Investigaciones Científicas
Priority to AU62357/01A priority Critical patent/AU6235701A/en
Publication of WO2001089629A1 publication Critical patent/WO2001089629A1/en

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/18—Applying electric currents by contact electrodes
    • A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
    • A61N1/372—Arrangements in connection with the implantation of stimulators
    • A61N1/37211—Means for communicating with stimulators
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/18—Applying electric currents by contact electrodes
    • A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
    • A61N1/36007—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation of urogenital or gastrointestinal organs, e.g. for incontinence control
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/18—Applying electric currents by contact electrodes
    • A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
    • A61N1/372—Arrangements in connection with the implantation of stimulators
    • A61N1/37211—Means for communicating with stimulators
    • A61N1/37235—Aspects of the external programmer
    • A61N1/37247—User interfaces, e.g. input or presentation means

Definitions

  • Sacral root stimulation system by implant fed by radio frequency.
  • Implantable medical product for the control of urination, defecation and erection in patients with neuropathies.
  • the present invention relates to the use of stimulation systems based on implants fed by radio frequency for the control of urination, defecation and erection in patients with neuropathies and, in particular, for spinal cord injuries.
  • the application of electrical impulses to the sacral roots allows patients with neuropathies to control the anal and bladder sphincters. Such stimulation allows emptying of urine from the bladder or its controlled retention. On the other hand, it is also possible to control defecation and in the case of men, erection.
  • the main advantage of controlled stimulation of the sacral roots is the decrease in the necessary currents and their greater dissociation from the sensory fibers whose stimulation is normally associated with pain sensation.
  • the state of the art associated with the present invention focuses on urinary control based on the stimulation of the sacral roots that Brindley developed in the 70s described in patent US3870051.
  • the implantable stimulator generates stimulation pulses in voltage of width and duration related to the radio frequency signal that it receives from an inductive coupling between coils.
  • Each stimulation channel is associated with a coil, the voltage stimulation being dependent on the inductive coupling between the implant coils and the external unit and on the impedance of the electrode-tissue interface itself.
  • the inductive coupling depends on the position and distance between the external coils and the implanted ones, obtaining a non-linear relationship between the programming of the pulses in the external unit and the pulses that are generated in the implant.
  • the position between coils basically depends on how the patient adjusts the external coils with the internal coils that he does not see.
  • the distance depends on the place of the implant and the thickness of the tissue.
  • the object of the invention shares with patent US3870051, the sacral root stimulation technique based on the control of stimulation pulses and stimulation frequencies and the use of implanted electrodes, although not limited to this.
  • the system object of the invention of this patent solves the problems derived from voltage stimulation by generating current stimulation pulses starting from a voltage high enough to guarantee the injection of controlled charge.
  • the generation of the stimulation pulses does not depend on the telemetric link between coils, this being independent of the position and distance between the implanted and external coils.
  • the accuracy and repeatability of the pacing waveforms is ensured by digital programming of the pacing parameters and generation of the pacing pulses in the implant using a 7-bit digital-to-analog (D / A) converter and a crystal controlling the duration of the pulses.
  • the impedance of the electrode-tissue interface can be monitored to determine its variations after implantation and subsequently during the years that the implant must remain in the patient's body. It also incorporates a system to ensure that the energy received in the implant is sufficient for the stimulation requested according to the stimulation parameters that are transmitted from the outside. This system allows the reduction of the power to be transmitted through the skin according to the frequencies and characteristics of the stimulation pulses that are being used. 4. Description of the invention
  • Said system is constituted according to the diagram of figure 1, by two subsystems, one implanted and the other external to the patient.
  • the implanted or implantable system is made up of an implantable stimulator (1) with connection to electrodes (11).
  • the external system is made up of a portable external unit (15) and programming hardware (13) of the portable external unit using specific software (12).
  • the programming software and hardware (12,13) allow the physician to adjust the stimulation and configuration parameters of the portable external unit.
  • the set of stimulation parameters definable by the doctor regarding the stimulation waveforms are at least the following: stimulation frequencies, amplitude of the stimulation current, slope of the stimulus current pulses and duration of the pulses. These parameters are independent between the various stimulation channels of the implantable stimulator (1). Furthermore, it is possible to control time bursts with or without pacing pulses and the maximum time that the patient can use these sequences.
  • the set of stimulation sequences defined by the doctor are associated with different programs which, in turn, are related to the independent control of urination, defecation or erection. Said parameters are sent and stored in the portable external unit (15) by means of non-volatile memory.
  • the portable external unit (15) has the capacity to store the programs defined by the software (12) and transferred from the programming hardware (13) to the portable external unit through the link (14).
  • Said link (14) can be by cable, infrared or wireless data transmission systems.
  • This portable external unit is used by the patient to control his urination, defecation or erection, at his own discretion using the programs and parameters defined by his medical team.
  • the activation and activation of the buttons (17) of the portable external unit supposes the start of the transmission of energy to the implant by inductive coupling between the coils of said unit (18) and the coils (7) of the stimulator implantable (1). The correct alignment between said coils, is notified to the patient by means of light signals or hums coming from the portable external unit.
  • the transmission of the stimulation parameters and the control of the stimulation sequences begins, initiating the stimulation sequence.
  • the patient can end the stimulation sequence using the buttons or moving the portable external unit away from the vicinity of the implantable stimulator.
  • the implantable stimulator (1) is responsible for generating the current stimulation pulses, and the measurements of the electrode-tissue impedance for each of the channels. stimulation and measurement of the induced voltage in the implant coils (7) to ensure that the current stimulation is correct.
  • Most of these electronic circuits are implemented in a specific application integrated circuit that we call with the generic name of ASIC (8). This has the advantage of reducing the area allocated to electronic components as well as consumption and increasing benefits.
  • the system object of the invention has as advantages over other implantable stimulators, the use of step-down type DC DC power converters in a single coil system for receiving energy. This supposes a decrease in the power necessary to achieve, on the one hand, the regulated voltage or voltages necessary for current stimulation circuits and, on the other hand, the regulated voltage for components that do not require a high supply voltage such as the integrated circuit specific application.
  • FIG. 1 It is an overview of the stimulation system object of this patent. Three major blocks are distinguished: 1) The part implanted in the patient consisting of the implantable stimulator (1) and the electrodes (11), 2) the portable external unit (15) and 3) the programming software and hardware (12, 13). - Implantable stimulator (1) - Fabric (3)
  • FIG. 2 It is a block level diagram of the implantable stimulator (1) and the electrodes (11). In this scheme, some of the basic elements for the control of the stimulation are shown (37, 38, 39), the regulation system of the supplies necessary for the operation of the stimulator (29, 30 and 9) and the blocks associated with wireless communication via telemetry for data reception and transmission (7, 33 and 34).
  • Figure 3 Shows the possible implementation of the current output D / A converter (37) based on a stable current source controlled by a stable voltage reference VBG and multiplexing (38) of the output current of the D / A converter he made the output stages of each stimulation channel (II, 12, 13).
  • the control for switching between channels appears in the multiplexer, consisting of the CtrlP switch and the Rp resistance, preventing the appearance of current peaks at the output due to the variation in the impedance that the converter A at each moment has. .
  • Figure 4 Shows the current amplification stage of one of the stimulation channels. This stage amplifies the current coming from the D / A converter in figure 3.
  • a regulated voltage (Vstim) greater than the regulation voltage with which the A / D converter works is used due to the impedance of the electrodes and the electrode interface. tissue, and by the necessary currents of stimulation.
  • the SI and S2 switches are used for the injection of the current to the electrode and for its recovery.
  • the output node Vmeasured refers to the node whose voltage is measured to characterize the electrode-tissue impedance.
  • Figure 5 It is a simplification of the scheme for the impedance meter (40).
  • the stimulation channels are multiplexed to decrease the necessary circuitry, using only a voltage comparator whose supply is that of the amplification stage of Figure 4, and a level displacer connected to the digital control logic (36).
  • FIG. 6 It is a simplified diagram of the implantable stimulator's voltage regulation system (1).
  • the energy receiving coil system (7) is connected to an AC / DC rectifier (29) whose maximum voltage is limited by a voltage limiter (30) connected to a voltage meter (31) that It compares according to a programmable value from the digital control logic (36) and whose objective is to control the power transmission from the portable external unit.
  • the voltage limited by (30) is regulated by a normally linear type regulator
  • Figure 7 Shows the connection between the coil system (7) of the implantable stimulator (1) and the transmitter (33) and receiver (34) included in it, responsible for the transmission and reception of data, respectively, between the implantable stimulator (1) and the portable external unit (15) of figure 1. It goes without saying that the receiver is It is connected to the same coil as the one used in figure 6 for energy reception.
  • a control system of the functions of urination, defecation and erection is described, which we will call control functions, in patients with neuropathies and specifically, for spinal cord injuries.
  • Said system (figure 1) is based on three parts: portable external unit (15), programming software and hardware (12, 13) and implantable stimulator (1) with connection to electrodes (11) through a connector (10).
  • the software (12) is used by the medical equipment for the adjustment of the stimulation parameters and is executed on a hardware (13), this being normally a personal computer.
  • one or more pacing programs defined by one or more pacing sequences are defined for the control functions.
  • the stimulation sequences are characterized by: a) the definition of the stimulation pulses for each of the stimulation channels of the implantable stimulator (1), b) the stimulation frequencies, whether or not they are independent for each stimulation channel and c ) the duration of these sequences.
  • the definition of the pulses is characterized, although not limited, to the definition of the type of current pulse to be applied, containing a monophasic pulse with exponential recovery or a biphasic pulse. Additionally, each stimulation pulse may have one or more controlled current and step slopes associated, forming trapezoidal-looking pulses. For each pulse, the duration and amplitude of the current to be applied are specified.
  • Each pacing channel has an associated pacing rate also definable in the software (12).
  • the stimulation sequences allow specifying durations for each stimulation channel or a set of them, without containing stimulation pulses constituting burst stimulation.
  • the software (12) allows to visualize on a screen associated with the programming hardware (13), the waveforms of the pulses in current and to maintain an associated database to the sequences defined for the control functions for each of the patients using the system object of the invention of this patent.
  • the stimulation control parameters defined by the software (12) are transferred to the outdoor unit (15) via the link (14).
  • Said link allows data transfer from the programming hardware (13) and the portable external unit (15) using a wired, infrared or wireless link by telemetry, or any combination of the mentioned methods.
  • the software (12) allows the medical team to interrogate the implantable stimulator (1) to check the impedance of the interface between the electrodes and the tissue, detecting, when this happens, the total or partial breakage of the electrode or the connector associated with said electrode by large variation of measured impedance. This measure also allows evaluating the evaluation of the electrodes after implantation during the maturation time of the implant and its evolution with implantation time.
  • the interrogation of the electrode impedance measurement is carried out by means of a command transmitted from the programming hardware (13) to the portable external unit (15) through the link (14) and the interrogation from the portable external unit (15) the implantable stimulator (1) by inductive coupling (19).
  • the response from the implantable stimulator follows the opposite path.
  • the external portable unit (15) is the command that the patient uses at will to initiate control functions and which, in turn, is used by the medical team to determine the most appropriate parameters and stimulation sequences.
  • Said unit is of reduced size and light weight powered by one or more batteries (16), these being rechargeable or not as required. In the case of rechargeable batteries, it allows the connection of a battery charger through a conventional connector that makes it impossible to use the external portable unit to control the implantable stimulator (1) during recharging.
  • the external portable unit (15) contains several pushbuttons (17) and switches allowing its ignition and the start of the transfer of energy and information to and from the implantable stimulator (1) by means of the inductive coupling (19) between coil or coils (18 ) of the portable external unit (15) and coil or coils (7) of the implantable stimulator (1), through the skin and tissue that separate the two subsystems. Said inductive coupling is carried out using LC type series or parallel resonant circuits.
  • the portable external unit (15) is normally controlled by a low consumption microprocessor that also manages the writing and reading of non-volatile memory. Said memory stores the information regarding the sequences that must be controlled according to the control functions and statistical information on the use of the implant by the patient.
  • control that the patient has over his control functions does not depend on the programming software or hardware (12 and 13). Additional characteristics of this unit are LEDs indicating the required control functions and the indication by LED or buzzer of a correct positioning of the command (15) with respect to the implantable stimulator (1) guaranteeing sufficient energy in the implant and correct bidirectional communication.
  • the implantable part of the system constitutes the controller for the stimulation of sacral roots.
  • the different stimulation channels of the implantable stimulator (1) are connected to the electrodes by means of a connector or connectors (10), preferably of the pacemaker type, which makes it easier for the medical team in charge of implantation of the implantable stimulator (1).
  • Said stimulator is encapsulated using biocompatible materials, preferably using a ceramic encapsulation allowing the electronic components to be together with the coil system or coils (7) for energy reception and data reception and transmission, reducing the total size of the implant.
  • the coil or coils for the reception of energy in the implantable stimulator must be located in such a way that the possible effect of energy reduction is diminished due to the interference of the magnetic field with titanium in the inductive coupling between the coil system (18) of the portable external unit and the coil system for receiving energy from the implantable stimulator (1).
  • the electronic components of the implantable stimulator are positioned on a printed circuit board or substrate (6).
  • the communication control and control of the stimulation channels are governed by an integrated circuit of specific application, which we call with the generic name of ASIC (8).
  • Said ASIC may contain part or all of the regulation system (9), transmitter and receiver, and stimulation circuit.
  • the implantable stimulator (1) is not limited to the use of specific application circuits or integrated circuits and one or more microcontrollers can be used additionally or as a complement. In any case, it is necessary that the controller be of low consumption to decrease the energy transfer from the portable external unit (15) to the implantable stimulator (1).
  • the main advantages of using an ASIC to control the implant are, in addition to the possible low consumption, the reduction of the total size of the implant.
  • the design of the ASIC using CMOS technologies compatible with bipolar processes (BiCMOS) and DMOS allows a greater integration of the components of the implantable stimulator (1) by allowing higher control voltages in the devices.
  • the maximum currents necessary for stimulation of the sacral roots and the electrode-tissue impedance implies the use of relatively high voltages with respect to the maximum drain-jet voltage of conventional CMOS technologies.
  • the implantable stimulator (1) is characterized, according to figure 2, by a system of coil or coils (7) that constitute typically coil-inductor (LC) resonant circuits that are used for receiving energy and data.
  • the radiofrequency signal generated from the portable external unit through a power amplifier connected to the coil system (18), is received in the coil system (7) of the implant and rectified by a rectifier bridge (29) connected to capacity or capacities. of storage.
  • the bridge rectifier is a full wave rectifier or a voltage bender.
  • a voltage limiter (30) Associated with this voltage at the output of the rectifier bridge (29) we have a voltage limiter (30) that protects the devices, including the associated capacities, from overvoltage.
  • the voltage limiter (30) is characterized by having a behavior similar to a zener and its implementation may vary.
  • the implantable stimulator (1) Due to the control for the reduction of energy transmitted through the skin carried out by the portable external unit (15), the implantable stimulator (1) has a system for measuring the voltage (31) associated with the rectifier bridge. Said system allows comparing with one or several reference levels, notifying by communication from the implantable stimulator (1) to the external portable unit, the result of said comparison.
  • the programming or setting of the comparison levels used in the voltage meter (31) as well as the interrogation of said levels by the external portable unit allows to decrease and control the necessary transmission power according to the operation in each case that has the implantable stimulator and in the distance and alignment situation between coils (7 and 19) that exist.
  • said control allows the patient to know, by means of a buzzer or a led, that the coils have been correctly aligned, being the power received in the implant sufficient for its operation.
  • the implantable stimulator (1) although it may be partially powered by a rechargeable battery, requires the transmission of energy from the portable external unit (15), it has a power-on-reset circuit to ensure its power on.
  • the implementation of said system could be, using a simple RC resistor-capacitor circuit connected to the ASIC reset signal.
  • the circuitry guarantees, although the control logic (36) is not sufficiently powered, voltages that do not exceed the maximum voltages allowed by the devices.
  • the implantable stimulator (1) has a transmitter (33) and receiver (34).
  • the receiver (34) demodulates and decodes the transmitted information, being interpreted by the control logic (36) as commands to control the stimulation, configuration parameters of the implanted system, and requests for information from the implantable stimulator (1).
  • the commands for stimulation control are basically: the start of the generation of the current stimulation pulses for one or more stimulation channels, enabling and disabling channels, definition of the stimulation waveforms and, enabling and disabling of the impedance measurement of the electrode-tissue interface.
  • the configuration commands are mainly intended to control the comparison levels of the voltage meter (31) to control the power delivered to the implant and to fine-tune the stable reference voltage (35) used in analog parts of the ASIC ( 8).
  • the bidirectional communication between the implantable stimulator (1) and the portable external unit (15) is defined synchronously between both systems so that the demodulation and decoding circuits are simplified and avoids or reduces possible interferences between both transmission channels.
  • it is modulated in both cases by modulation in carrier amplitude.
  • the carrier for the transfer of information and data from the external portable unit (15) to the implantable stimulator (1) is of a higher frequency than that used for data transmission from the implantable stimulator. Said system prevents the high power signal transmitted from the portable external unit and / or its harmonics from interfering with the demodulation process of the low power signal transmitted from the implantable stimulator.
  • the voltage regulation system (9) in the implantable stimulator (1) is made up of linear regulators and step-down DC / DC power converters.
  • the regulated voltage for the output stage of the stimulation circuit (90) comes from the output of the rectifier bridge (29) and limited by (30). In this regulation, linear regulators and storage and filtering capacities are used at the output.
  • Control of the voltage at the output of the rectifier bridge (29) by means of the voltage meter (31) and control of the output power of the transmitter of the external portable unit (15) allows the increase in power efficiency of the stimulator regulator (90).
  • the output of the stimulator regulator (90) is associated with one or more step-down type DC / DC power converters (91) to regulate the voltages necessary for the control logic (36) and analog parts of the ASIC (8) or necessary discrete components, and there may be, between said regulated voltages, other regulation systems or level shifters for the control of parts of the implantable stimulator (1).
  • step-down type DC / DC power converters increases the power efficiency of the system due to the difference in voltage between the voltage necessary to generate the current stimulation and the voltage necessary to supply the control logic, this being typically greater than 10 Volts.
  • the generation of the current stimulation pulses is controlled by the control logic (36).
  • Said logic has the information coming from the portable external unit (15) regarding the waveform of the pulses.
  • the pulses in current are controlled by a D / A converter with current output based on a stable current reference dependent on the reference voltage (35).
  • the output current of the D / A converter (37) is multiplexed according to the stimulation channel to be selected by means of an analog multiplexer (38) towards a current amplifier (39) per channel.
  • Said amplifier constitutes the output stage of each channel and is connected to connector (10) by means of decoupling capabilities, avoiding DC voltages at the electrodes.
  • the pacing pulses may contain slopes forming trapezoidal pacing pulses.
  • pulses are generated by steps increasing the output current based on a programmable factor by means of a simple counter implemented in the control logic (36).
  • the recovery of the charge injected through the electrodes is carried out using controlled current or exponential recovery.
  • the resolution of the duration of the pulses and the output current steps is fixed by the clock frequency of the ASIC (8) or a divisor of this. Said clock comes from a crystal connected to the ASIC (8), usually being 1 MHz in frequency.
  • the parameters that define the stimulation pulses are at a minimum: the duration of the pulses, the magnitude of the output current and the existence or not of current steps and their definition. These parameters are independent for each of the stimulation channels.
  • the control of the stimulation frequencies is controlled by the external portable unit (15) reducing the control logic (36).
  • said command specifies more than one channel to stimulate and the architecture of the implantable stimulator is based on a single D / A converter (37), the stimulation pulses are multiplexed in time. In this case, the priority is set by the order (number) associated with the stimulation channels.
  • - External portable unit (15) powered by a single 9V battery in a plastic box containing three buttons (17) associated with each of the three system control functions and two LEDs.
  • the LEDs indicate that the energy transfer is sufficient and that the data transmission is correct.
  • It incorporates a non-volatile memory of EEPROM type for the storage of programs and stimulation sequences.
  • the management of said memory as well as the communication with the programming hardware and the frequency control is implemented in a microprocessor.
  • There is a second microcontroller in charge of generating the data packets to be transmitted and receiving data from the implantable stimulator (1) communicated with the first one and which also manages the indicator LEDs.
  • Step-down type DC DC power converter supplying regulated 5V for the control logic (36) and analog parts of the ASIC (8).
  • the ASIC (8) clock frequency is 1.00 MHz from a crystal and the duration of the stimulation pulses are defined by 8 bits defining stimulation pulses between 4 us and 1024 us with a step of 4 us set by dividing the crystal frequency by four.
  • the stimulation pulses are single phase with exponential load recovery and the duration of the steps in the trapezoidal pulses are calculated based on an increment defined also with 8 bits.
  • the duration of each step is exactly 4 us and the increase in current is the specified one, the duration being limited by the maximum amplitude or by the duration of the stimulation pulse.
  • the independent information for each channel controlled in the ASIC is the existence or not of steps constituting trapezoidal stimulation pulses, the amplitude or increase of the step and the duration of the pulse.
  • the external portable unit controls the stimulation frequencies and the burst times, enabling or disabling the channels by means of a command through the inductive coupling (19).
  • the stimulation frequencies are based on a 32,768 Khz crystal connected to the first of the microcontrollers, setting stimulation frequencies between 1Hz and 120Hz with a step of lHz.
  • the transmission of power from the portable external unit to the implantable stimulator is carried out by means of an E-class power amplifier using a 6 MHz carrier whose maximum supply voltage is controlled according to the required power control and whose minimum supply voltage is 0V modulating the carrier in amplitude with modulation index 100%.
  • the encoding of the pulses is by pulse width.
  • Figure 3 shows the implementation of the D / A converter with current output whose reference current depends on the stable reference voltage (35), called bandgap voltage (VBG).
  • Switches B6 through B0 are the control bits for the output current.
  • the channel multiplexer (38) is implemented using low resistance analog switches (Chl, Ch2 and Ch3).
  • the resistance Rp and CtrlP allow maintaining an impedance equivalent to what the output of the A / D converter will have when one of the Chl, Ch2 or Ch3 channels is activated.
  • the control sequence is to turn on the current reference, apply the control code with B6 .. B0 and activate Ctrlp. Subsequently, it is switched between CtrlP and one of the Chl, Ch2 or Ch3 channels. This reduces current peaks at the output of the D / A converter.
  • the current outputs II, 12 and 13 are connected to three current amplifiers such as those shown in figure 4. Thus, each stimulation channel has an associated 1: n ratio current mirror implemented with bipolars whose multiplication factor of the current is sufficient to supply 40mA.
  • Figure 4 also shows the connection diagram of said stimulation channel to the bipolar connector used.
  • the SI switch is connected when the input current (Channel) is enabled, while S2 remains disconnected. In this situation, the input current is maintained for the duration set by the channel parameters, and may also contain variations in channel due to changes in the B6..B0 code of the D / A converter, generating current steps at the output.
  • load recovery SI goes off and switch S2 short circuits both ends of the electrode.
  • the anodes and cathodes of the electrodes are connected to the connector (10).
  • said channel has the electrode anode connected to the midpoint of switches SI and S2.
  • the cathode is associated with the decoupling capacity.
  • the SI switch connects the regulated supply for the 16V stimulator (Vstim) to the anode.
  • the Vmeasure node is used to measure the impedance according to the diagram in figure 5.
  • FIG 5 it is shown how each channel has its own Vmeasure associated and how these are multiplexed by means of three other switches SI, S2 and S3.
  • the impedance measurement can only be performed on a single stimulation channel at a time.
  • the Soff switch ensures the initial input level to the high voltage comparator (16V).
  • Said comparator compares the selected V measurement with a stable voltage that depends on the stable reference voltage (35) of the ASIC (8).
  • the level adapter converts the comparator output into a CMOS compatible logic level signal.
  • Disabling the impedance measurement supposes the disconnection of SI, S2 and S3 and the activation of Soff, as well as the disabling of the comparator and the level adapter. This mechanism supposes the reduction of the consumption of the ASIC. Since the comparator is in fact a 1-bit converter, the measurement of the impedance is made by programming a sequence of stimuli of different amplitude by sweeping and detecting for which current pulse the comparator has switched its result. Impedance measurements are controlled by software (12) using a personal computer (13) connected to the portable external unit by means of a cable through RS-232C serial communication. The software displays and stores the impedance measurements for each of the three channels.
  • the energy receiver circuit It is based on a 6MHz resonant parallel circuit forming part of the coil system (7) of the implantable stimulator (1).
  • the radio frequency signal coming from the class E power amplifier of the portable external unit, is rectified by means of a full-wave rectifier (29), said rectifier has associated with at least a 47uF / 25V storage capacity whose voltage limiter ( 30) avoid voltages greater than 23-24V.
  • the voltage limiter architecture is based on a bipolar chain acting as zeners and a power NMOS. The resistance has a much higher impedance than that of the equivalent zener when the voltage is higher than the limiting one (around 22 V).
  • a node of the bipolar chain of the power limiter is chosen so that it offers a voltage directly proportional and approximately linear to the rectified voltage in the rectifier bridge and whose voltage is below 5V for the maximum voltage allowed by the limiter.
  • This voltage is used by the voltage meter (31) to compare with a variable and selectable reference voltage between two levels that indicate a voltage at the rectifier bridge output less than 14V or greater than 18V. The result of such comparison is sending to the portable external unit when requested.
  • the indication of a voltage not lower than 14V guarantees that the digital and analog part of the ASIC works and the transmitted parameters have not been lost due to lack of power.
  • the voltage indication above 18V indicates that the implant has enough energy to guarantee the wide range of output currents.
  • the output voltage of the rectifier bridge is the input of the 16V linear regulator. This voltage is used for the current stimulator output stage (Vstim). From the Vstim node we connect a step-down type DC / DC power converter whose output feeds the non-power parts in the ASIC.
  • a scheme for the control of reception and transmission of data in the implantable stimulator is shown in Figure 7.
  • the coil associated with the reception of data is the same as that used for the reception of energy.
  • the ASIC incorporates a low pass filter to eliminate the 6MHZ carrier transmitted from the portable external unit.
  • Said filter associated with a comparator, outputs a signal of 0-5V voltage levels depending on the existence or not of the carrier, respectively.
  • the suppression of the carrier supposes a change in the output level of the filter and the count is started in the counter- 1.
  • Each one of the counters in figure 7 has as its output level a logical 'Y' during non-activation and a logical level '0' after the end of the count.
  • the implementation of said counters can be either by means of a counter at the ASIC clock frequency, 1MHZ, or by controlled discharges of a certain capacity at constant current and comparator at its output.
  • figure 7 also shows the connection to a second coil of the coil system (7) of the implantable stimulator with which information is transmitted to the portable external unit.
  • a simple class B power amplifier is used as a transmitter.
  • the logic at the transmitter input ensures that the transmitter is turned off during the ASIC power-on-reset time.
  • the CLK signal references the 1MHz clock itself obtained from the crystal associated with the ASIC.
  • the data to be transmitted enables the transmitter for a certain time set by counter-5.
  • Data from the implantable stimulator is coded using Manchester code. Synchronization between the portable external unit and the implantable stimulator allows the microprocessor of the portable external unit to limit the time to wait for a response and to control transmission and reception errors by forwarding the data packets.

Abstract

The invention relates to a control system to control urination, defecation and also erection in the case of men, in patients suffering from neuropathies, more particularly patients with medullar injuries. According to the diagram in figure (1), said system comprises two sub-systems, one of which is implanted and the other one is external to the patient. The implanted or implantable system comprises an implantable stimulator (1) having connections to electrodes (11). The external system comprises a portable external unit (15) and a hardware for programming (13) said portable external unit using a specific software (12). The software and the programming hardware (12, 13) make it possible for the doctor to adjust the stimulation parameters and the configuration of the portable external unit.

Description

1. Título de la invención1. Title of the invention
Sistema de estimulación de raíces sacras mediante implante alimentado por radio frecuencia.Sacral root stimulation system by implant fed by radio frequency.
2. Sector de la técnica2. Technical sector
Sector médico dedicado a rehabilitación mediante productos sanitarios implantables. Producto médico implantable para el control de la micción, defecación y erección en pacientes con neuropatías.Medical sector dedicated to rehabilitation using implantable medical devices. Implantable medical product for the control of urination, defecation and erection in patients with neuropathies.
3. Estado de la técnica3. State of the art
La presente invención hace relación a la utilización de sistemas de estimulación basados en implantes alimentados por radio frecuencia para el control de la micción defecación y erección en pacientes con neuropatías y en particular, para lesionados medulares. La aplicación de impulsos eléctricos en las raíces sacras permite a pacientes con neuropatías el control de los esfínteres anal y vesical. Dicha estimulación permite el vaciado de la orina de la vejiga o su retención controlada. Por otro lado, también es posible controlar la defecación y en el caso de hombres la erección. La principal ventaja de la estimulación controlada de las raíces sacras es la disminución de las corrientes necesarias y su mayor desvinculación de las fibras sensoriales cuya estimulación se asocia normalmente a sensación de dolor.The present invention relates to the use of stimulation systems based on implants fed by radio frequency for the control of urination, defecation and erection in patients with neuropathies and, in particular, for spinal cord injuries. The application of electrical impulses to the sacral roots allows patients with neuropathies to control the anal and bladder sphincters. Such stimulation allows emptying of urine from the bladder or its controlled retention. On the other hand, it is also possible to control defecation and in the case of men, erection. The main advantage of controlled stimulation of the sacral roots is the decrease in the necessary currents and their greater dissociation from the sensory fibers whose stimulation is normally associated with pain sensation.
El estado de la técnica asociado a la presente invención se centra en el control urinario basado en la estimulación de las raíces sacras que Brindley desarrolló en los años 70 descrito en la patente US3870051. Existe un dispositivo comercial para el control de la defecación, micción y erección en lesionados medulares denominado Vocare Bladder NeuroControl System distribuido por NeuroControl Corporation (Cleveland, USA) y fabricado por la empresa FineTech Ltd que tiene como origen la patente US3870051. En dicho sistema, el estimulador implantable genera pulsos de estimulación en tensión de anchura y duración relacionados a la señal de radio frecuencia que recibe desde un acoplo inductivo entre bobinas. Cada canal de estimulación está asociado a una bobina, siendo la estimulación en tensión dependiente del acoplo inductivo entre las bobinas del implante y la unidad externa y de la propia impedancia de la interficie electrodo-tejido. El acoplo inductivo depende de la posición y distancia entre las bobinas externas y las implantadas, obteniendo una relación no lineal entre la programación de los pulsos en la unidad externa y los pulsos que se generan en el implante. La posición entre bobinas básicamente depende de en que forma el paciente ajusta las bobinas externas con las bobinas internas que no ve. Por otro lado, la distancia depende del lugar del implante y del grosor del tejido. Por lo tanto, no es posible el ajuste por parte del equipo médico de unos parámetros que disminuyan la transferencia de energía a través de la piel ni tampoco el ajuste de las corrientes de estimulación mínimas necesarias, disminuyendo la inyección de cargas en los electrodos. La disminución de las corrientes inyectadas a través de los electrodos para las mismas condiciones de duración de pulso y frecuencia de estimulación supone una mayor duración para los electrodos implantados.The state of the art associated with the present invention focuses on urinary control based on the stimulation of the sacral roots that Brindley developed in the 70s described in patent US3870051. There is a commercial device for the control of defecation, urination and erection in spinal cord injuries, called the Vocare Bladder NeuroControl System distributed by NeuroControl Corporation (Cleveland, USA) and manufactured by FineTech Ltd, which originates from patent US3870051. In this system, the implantable stimulator generates stimulation pulses in voltage of width and duration related to the radio frequency signal that it receives from an inductive coupling between coils. Each stimulation channel is associated with a coil, the voltage stimulation being dependent on the inductive coupling between the implant coils and the external unit and on the impedance of the electrode-tissue interface itself. The inductive coupling depends on the position and distance between the external coils and the implanted ones, obtaining a non-linear relationship between the programming of the pulses in the external unit and the pulses that are generated in the implant. The position between coils basically depends on how the patient adjusts the external coils with the internal coils that he does not see. On the other hand, the distance depends on the place of the implant and the thickness of the tissue. Therefore, the setting by the medical team of parameters that decrease the energy transfer through the skin is not possible, nor is the adjustment of the minimum necessary stimulation currents, reducing the injection of charges into the electrodes. Decreasing the currents injected through the electrodes for the same conditions of pulse duration and pacing rate means a longer duration for the implanted electrodes.
El objeto de la invención comparte con la patente US3870051, la técnica de estimulación de las raíces sacras basada en el control de los pulsos de estimulación y frecuencias de estimulación y la utilización de electrodos implantados, aún no estando limitado a ésta. El sistema objeto de la invención de esta patente, soluciona los problemas derivados de la estimulación en tensión mediante la generación de pulsos de estimulación en corriente partiendo de una tensión suficientemente alta como para garantizar la inyección de carga controlada. Por otro lado, la generación de los pulsos de estimulación no depende del enlace telemétrico entre bobinas siendo ésta independiente de la posición y distancia entre las bobinas implantadas y externas. Además, la precisión y repetición de las formas de onda de estimulación se garantiza mediante la programación digital de los parámetros de estimulación y la generación de los pulsos de estimulación en el implante utilizando un convertidor digital-analógico (D/A) de 7 bits y un cristal controlando la duración de los pulsos. Además, se puede monitorizar la impedancia de la interfase electrodo-tejido para determinar sus variaciones después de la implantación y posteriormente durante los años que debe permanecer el implante en el cuerpo del paciente. Incorpora además, un sistema para asegurar que la energía recibida en el implante es suficiente para la estimulación solicitada según los parámetros de estimulación que se transmiten desde el exterior. Dicho sistema, permite la reducción de la potencia a transmitir a través de la piel según las frecuencias y características de los pulsos de estimulación que se estén utilizando. 4. Descripción de la invenciónThe object of the invention shares with patent US3870051, the sacral root stimulation technique based on the control of stimulation pulses and stimulation frequencies and the use of implanted electrodes, although not limited to this. The system object of the invention of this patent, solves the problems derived from voltage stimulation by generating current stimulation pulses starting from a voltage high enough to guarantee the injection of controlled charge. On the other hand, the generation of the stimulation pulses does not depend on the telemetric link between coils, this being independent of the position and distance between the implanted and external coils. In addition, the accuracy and repeatability of the pacing waveforms is ensured by digital programming of the pacing parameters and generation of the pacing pulses in the implant using a 7-bit digital-to-analog (D / A) converter and a crystal controlling the duration of the pulses. In addition, the impedance of the electrode-tissue interface can be monitored to determine its variations after implantation and subsequently during the years that the implant must remain in the patient's body. It also incorporates a system to ensure that the energy received in the implant is sufficient for the stimulation requested according to the stimulation parameters that are transmitted from the outside. This system allows the reduction of the power to be transmitted through the skin according to the frequencies and characteristics of the stimulation pulses that are being used. 4. Description of the invention
4.1 Breve descripción de la invención.4.1 Brief description of the invention.
Se trata de un sistema de control de la micción, defecación y en el caso de hombres también del control de la erección, para personas con neuropatías y en particular para lesionados medulares, basado en la estimulación de las raíces sacras según el método, aunque no limitado, propuesto porBrindley (US3870051). Dicho sistema está constituido según el esquema de la figura 1, por dos subsistemas, uno implantado y otro externo al paciente. El sistema implantado o implantable está compuesto por un estimulador implantable (1) con conexión hacía unos electrodos (11). El sistema externo está compuesto por una unidad externa portátil (15) y un hardware de programación (13) de la unidad externa portátil utilizando un software específico (12).It is a system of control of urination, defecation and in the case of men also of control of erection, for people with neuropathies and in particular for spinal cord injuries, based on the stimulation of the sacral roots according to the method, although not Limited, proposed by Brindley (US3870051). Said system is constituted according to the diagram of figure 1, by two subsystems, one implanted and the other external to the patient. The implanted or implantable system is made up of an implantable stimulator (1) with connection to electrodes (11). The external system is made up of a portable external unit (15) and programming hardware (13) of the portable external unit using specific software (12).
El software y hardware de programación (12,13) permiten al médico el ajuste de los parámetros de estimulación y configuración de la unidad externa portátil. El conjunto de parámetros de estimulación definibles por el médico referentes a las formas de onda de estimulación son como mínimo los siguientes: frecuencias de estimulación, amplitud de la corriente de estimulación, pendiente de los pulsos de corriente de los estímulos y duración de los pulsos. Dichos parámetros son independientes entre los diversos canales de estimulación del estimulador implantable (1). Además, es posible controlar ráfagas de tiempo con o sin pulsos de estimulación y el tiempo máximo que el paciente puede utilizar estas secuencias. El conjunto de secuencias de estimulación definidas por el médico se asocian a distintos programas los cuales, a su vez, están relacionados con el control independiente de la micción, defecación o erección. Dichos parámetros son enviados y almacenados en la unidad externa portátil (15) mediante memoria no volátil. La unidad externa portátil (15) dispone de capacidad para almacenar los programas definidos mediante el software (12) y transferidos desde el hardware de programación (13) hacía la unidad externa portátil mediante el enlace (14). Dicho enlace (14) puede ser por cable, infrarrojos o sistemas de transmisión de datos sin cable. Esta unidad externa portátil es utilizada por parte del paciente para controlar su micción, defecación o erección, según su propio criterio utilizando los programas y parámetros definidos por su equipo médico. El encendido y activación de los pulsadores (17) de la unidad externa portátil supone el inicio de la transmisión de energía hacía el implante mediante acoplo inductivo entre las bobinas de dicha unidad (18) y las bobinas (7) del estimulador implantable (1). El correcto alineamiento entre dichas bobinas, es notificado al paciente mediante señales luminosas o zumbidos provenientes de la unidad externa portátil. En esta situación, se inicia la transmisión de los parámetros de estimulación y el control de las secuencias de estimulación, iniciándose la secuencia de estimulación. En cualquier momento el paciente puede finalizar la secuencia de estimulación mediante los pulsadores o alejando la unidad externa portátil de las proximidades del estimulador implantable. En función de los parámetros que se reciben desde la unidad externa portátil, el estimulador implantable (1) es el responsable de la generación de los pulsos de estimulación en corriente, y de las medidas de la impedancia electrodo-tejido para cada uno de los canales de estimulación y de la medida de la tensión inducida en las bobinas del implante (7) para asegurar que la estimulación en corriente es correcta. La mayor parte de estos circuitos electrónicos se encuentra implementada en un circuito integrado de aplicación específica al que denominamos con el nombre genérico de ASIC (8). Esto tiene como ventaja la reducción del área destinada a componentes electrónicos así como el consumo y el incremento de prestaciones.The programming software and hardware (12,13) allow the physician to adjust the stimulation and configuration parameters of the portable external unit. The set of stimulation parameters definable by the doctor regarding the stimulation waveforms are at least the following: stimulation frequencies, amplitude of the stimulation current, slope of the stimulus current pulses and duration of the pulses. These parameters are independent between the various stimulation channels of the implantable stimulator (1). Furthermore, it is possible to control time bursts with or without pacing pulses and the maximum time that the patient can use these sequences. The set of stimulation sequences defined by the doctor are associated with different programs which, in turn, are related to the independent control of urination, defecation or erection. Said parameters are sent and stored in the portable external unit (15) by means of non-volatile memory. The portable external unit (15) has the capacity to store the programs defined by the software (12) and transferred from the programming hardware (13) to the portable external unit through the link (14). Said link (14) can be by cable, infrared or wireless data transmission systems. This portable external unit is used by the patient to control his urination, defecation or erection, at his own discretion using the programs and parameters defined by his medical team. The activation and activation of the buttons (17) of the portable external unit supposes the start of the transmission of energy to the implant by inductive coupling between the coils of said unit (18) and the coils (7) of the stimulator implantable (1). The correct alignment between said coils, is notified to the patient by means of light signals or hums coming from the portable external unit. In this situation, the transmission of the stimulation parameters and the control of the stimulation sequences begins, initiating the stimulation sequence. At any time the patient can end the stimulation sequence using the buttons or moving the portable external unit away from the vicinity of the implantable stimulator. Depending on the parameters received from the portable external unit, the implantable stimulator (1) is responsible for generating the current stimulation pulses, and the measurements of the electrode-tissue impedance for each of the channels. stimulation and measurement of the induced voltage in the implant coils (7) to ensure that the current stimulation is correct. Most of these electronic circuits are implemented in a specific application integrated circuit that we call with the generic name of ASIC (8). This has the advantage of reducing the area allocated to electronic components as well as consumption and increasing benefits.
El sistema objeto de la invención tiene como ventajas respecto a otros estimuladores implantables, la utilización de convertidores de potencia DC DC de tipo step-down en un sistema con una única bobina para la recepción de energía. Esto supone una disminución de la potencia necesaria para conseguir, por un lado, la tensión o tensiones reguladas necesarias para los circuitos de estimulación en corriente y por otro lado, la tensión regulada para los componentes que no requieren elevada tensión de alimentación como el circuito integrado de aplicación especifica.The system object of the invention has as advantages over other implantable stimulators, the use of step-down type DC DC power converters in a single coil system for receiving energy. This supposes a decrease in the power necessary to achieve, on the one hand, the regulated voltage or voltages necessary for current stimulation circuits and, on the other hand, the regulated voltage for components that do not require a high supply voltage such as the integrated circuit specific application.
Breve descripción de los dibujos La invención podría tener forma de varios componentes y conjuntos de componentes. Los dibujos son sólo propósitos de ilustración del texto de la patente y no limitan la invención.Brief Description of the Drawings The invention could be in the form of various components and component assemblies. The drawings are for purposes of illustration of the patent text only and do not limit the invention.
Figura 1: Es una visión general del sistema de estimulación objeto de esta patente. Se diferencian tres grandes bloques: 1) La parte implantada en el paciente constituida por el estimulador implantable (1) y los electrodos (11), 2) la unidad externa portátil (15) y 3) el software y hardware de programación (12,13). - Estimulador implantable (1) - Tejido (3)Figure 1: It is an overview of the stimulation system object of this patent. Three major blocks are distinguished: 1) The part implanted in the patient consisting of the implantable stimulator (1) and the electrodes (11), 2) the portable external unit (15) and 3) the programming software and hardware (12, 13). - Implantable stimulator (1) - Fabric (3)
- Piel (4)- Leather (4)
- Encapsulado (5)- Encapsulated (5)
- Substrato (6) - Bobinas (7)- Substrate (6) - Coils (7)
- ASIC (8)- ASIC (8)
- Regulación tensiones (9)- Voltage regulation (9)
- Conectar (10)- Connect (10)
- Electrodos (11) - Software (12)- Electrodes (11) - Software (12)
- Hardware programación (13)- Hardware programming (13)
- Enlace (14)- Link (14)
- Unidad portátil (15)- Portable unit (15)
- Batería (16) - Pulsadores (17)- Battery (16) - Push buttons (17)
- Bobinas (18)- Coils (18)
- Acoplo inductivo (19)- Inductive coupling (19)
Figura 2: Es un esquema a nivel de bloques del estimulador implantable (1) y de los electrodos (11). En dicho esquema, se muestran algunos de los elementos básicos para el control de la estimulación (37, 38, 39), el sistema de regulación de las alimentaciones necesarias para el funcionamiento del estimulador (29, 30 y 9) y los bloques asociados a la comunicación sin cables mediante telemetría para la recepción y transmisión de datos (7, 33 y 34). - Estimulador implantable (1)Figure 2: It is a block level diagram of the implantable stimulator (1) and the electrodes (11). In this scheme, some of the basic elements for the control of the stimulation are shown (37, 38, 39), the regulation system of the supplies necessary for the operation of the stimulator (29, 30 and 9) and the blocks associated with wireless communication via telemetry for data reception and transmission (7, 33 and 34). - Implantable stimulator (1)
- Encapsulado (5)- Encapsulated (5)
- Bobinas (7)- Coils (7)
- Regulación tensiones (9)- Voltage regulation (9)
- Conectar (10) - Electrodos (11)- Connect (10) - Electrodes (11)
- Puente rectificador (29)- Bridge rectifier (29)
- Limitador tensión (30) - Medidor tensión (31 )- Voltage limiter (30) - Voltage meter (31)
- Power on Reset (32)- Power on Reset (32)
- Transmisor (33)- Transmitter (33)
- Receptor (34) - Tensión referencia (35)- Receiver (34) - Reference voltage (35)
- Lógica control (36)- Control logic (36)
- Conversor D/A (37)- D / A converter (37)
- Multiplexación canales (38)- Channel multiplexing (38)
- Amplificador corriente (39) - Medidor impedancia (40)- Current amplifier (39) - Impedance meter (40)
- Regulador estimulador (90)- Stimulator regulator (90)
- Regulador lógica (91)- Logic controller (91)
Figura 3: Muestra la posible implementación del convertidor D/A de salida en corriente (37) basado en una fuente de corriente estable controlada por una referencia de tensión estable VBG y la multiplexación (38) de la corriente de salida del convertidor D/A hacía las etapas de salida de cada canal de estimulación (II, 12, 13). Además aparece en el multiplexor, el control para la conmutación entre canales, formado por el interruptor CtrlP y la resistencia Rp, evitando la aparición de picos de corriente a la salida debido a la variación de la impedancia que tiene en cada momento el convertidor A D.Figure 3: Shows the possible implementation of the current output D / A converter (37) based on a stable current source controlled by a stable voltage reference VBG and multiplexing (38) of the output current of the D / A converter he made the output stages of each stimulation channel (II, 12, 13). In addition, the control for switching between channels appears in the multiplexer, consisting of the CtrlP switch and the Rp resistance, preventing the appearance of current peaks at the output due to the variation in the impedance that the converter A at each moment has. .
- Conversor D/A (37) Multiplexación canales (38)- D / A converter (37) Channel multiplexing (38)
Figura 4: Muestra la etapa de amplificación de corriente de uno de los canales de estimulación. Dicha etapa amplifica la corriente proveniente del convertidor D/A de la figura 3. Se utiliza una tensión regulada (Vstim) mayor que la tensión de regulación con la que trabaja el convertidor A/D debido a la impedancia de los electrodos e interfase electrodo-tejido, y por las corrientes necesarias de estimulación. Los interruptores SI y S2 se utilizan para la inyección de la corriente hacía el electrodo y para su recuperación. El nodo de salida Vmedida hace referencia al nodo cuya tensión se mide para caracterizar la impedancia electrodo-tejido.Figure 4: Shows the current amplification stage of one of the stimulation channels. This stage amplifies the current coming from the D / A converter in figure 3. A regulated voltage (Vstim) greater than the regulation voltage with which the A / D converter works is used due to the impedance of the electrodes and the electrode interface. tissue, and by the necessary currents of stimulation. The SI and S2 switches are used for the injection of the current to the electrode and for its recovery. The output node Vmeasured refers to the node whose voltage is measured to characterize the electrode-tissue impedance.
- Conector canal (10) - Amplificador corriente (39)- Channel connector (10) - Current amplifier (39)
Figura 5: Es una simplificación del esquema para el medidor de impedancia (40). Se multiplexan los canales de estimulación para disminuir la circuitería necesaria, utilizando únicamente un comparador de tensión cuya alimentación es la propia de la etapa de amplificación de la figura 4, y un desplazador de nivel conectado a la lógica digital de control (36).Figure 5: It is a simplification of the scheme for the impedance meter (40). The stimulation channels are multiplexed to decrease the necessary circuitry, using only a voltage comparator whose supply is that of the amplification stage of Figure 4, and a level displacer connected to the digital control logic (36).
Figura 6: Es un esquema simplificado del sistema de regulación de tensiones del estimulador implantable (1). En dicha figura, el sistema de bobina (7) de recepción de energía se conectada a un rectificador AC/DC (29) cuya tensión máxima se encuentra limitada por un limitador de tensión (30) conectado a un medidor de tensión (31) que compara según un valor programable proveniente de la lógica digital de control (36) y cuyo objetivo es el control de la transmisión de potencia desde la unidad externa portátil. La tensión limitada por (30) se regula mediante un regulador normalmente de tipo linealFigure 6: It is a simplified diagram of the implantable stimulator's voltage regulation system (1). In said figure, the energy receiving coil system (7) is connected to an AC / DC rectifier (29) whose maximum voltage is limited by a voltage limiter (30) connected to a voltage meter (31) that It compares according to a programmable value from the digital control logic (36) and whose objective is to control the power transmission from the portable external unit. The voltage limited by (30) is regulated by a normally linear type regulator
(90) cuya salida Vstim es la utilizada por el amplificador de corriente según figura 4.(90) whose Vstim output is the one used by the current amplifier according to figure 4.
Además se muestra la conexión a un convertidor DC/DC de tipo step-down para la obtención de la tensión o tensiones de regulaciones necesarias para la lógica de control y partes analógicas (Vdd). - Bobina (7)In addition, the connection to a step-down type DC / DC converter is shown to obtain the voltage or regulation voltages necessary for the control logic and analog parts (Vdd). - Coil (7)
- Regulación tensiones (9)- Voltage regulation (9)
- Puente rectificador (29)- Bridge rectifier (29)
- Limitador tensión (30)- Voltage limiter (30)
- Medidor tensión (31) - Regulador estimulador (90)- Voltage meter (31) - Stimulator regulator (90)
- Step-down (91)- Step-down (91)
Figura 7: Muestra la conexión entre el sistema de bobinas (7) del estimulador implantable (1) y el transmisor (33) y receptor (34) incluidos en él, encargados de la transmisión y recepción de datos, respectivamente, entre el estimulador implantable (1) y la unidad externa portátil (15) de la figura 1. Se sobreentiende que el receptor se encuentra conectado a la misma bobina que la utilizada en la figura 6 para la recepción de energía.Figure 7: Shows the connection between the coil system (7) of the implantable stimulator (1) and the transmitter (33) and receiver (34) included in it, responsible for the transmission and reception of data, respectively, between the implantable stimulator (1) and the portable external unit (15) of figure 1. It goes without saying that the receiver is It is connected to the same coil as the one used in figure 6 for energy reception.
- Bobinas (7)- Coils (7)
- Transmisor (33) - Receptor (34)- Transmitter (33) - Receiver (34)
4.2 Descripción detallada de la invención.4.2 Detailed description of the invention.
En la presente invención se describe un sistema de control de las funciones de micción, defecación y erección, que denominaremos funciones de control, en pacientes con neuropatías y en concreto, para lesionados medulares. Dicho sistema (figura 1) se basa en tres partes: unidad externa portátil (15), software y hardware de programación (12, 13) y estimulador implantable (1) con conexión hacía electrodos (11) mediante un conector (10). El software (12) es utilizado por el equipo médico para el ajuste de los parámetros de estimulación y es ejecutado en un hardware (13) siendo éste normalmente un ordenador personal. En dicho software, se definen uno o varios programas de estimulación formados por una o varias secuencias de estimulación para las funciones de control. Las secuencias de estimulación están caracterizadas por : a) la definición de los pulsos de estimulación para cada uno de los canales de estimulación del estimulador implantable (1), b) las frecuencias de estimulación, sean éstas independientes o no para cada canal de estimulación y c) la duración de dichas secuencias. La definición de los pulsos viene caracterizada, aunque no limitada, a la definición del tipo de pulso en corriente a aplicar conteniendo un pulso monofásico con recuperación exponencial o un pulso bifásico. Adicionalmente, cada pulso de estimulación puede tener asociadas una o varias pendientes de corriente y paso controladas formando pulsos de aspecto trapezoidal. Para cada pulso, se especifica la duración y amplitud de la corriente a aplicar. Cada canal de estimulación tiene asociado una frecuencia de estimulación también definible en el software (12). Las secuencias de estimulación permiten especificar duraciones para cada canal de estimulación o un conjunto de ellos, sin contener pulsos de estimulación constituyendo estimulación por ráfagas.In the present invention a control system of the functions of urination, defecation and erection is described, which we will call control functions, in patients with neuropathies and specifically, for spinal cord injuries. Said system (figure 1) is based on three parts: portable external unit (15), programming software and hardware (12, 13) and implantable stimulator (1) with connection to electrodes (11) through a connector (10). The software (12) is used by the medical equipment for the adjustment of the stimulation parameters and is executed on a hardware (13), this being normally a personal computer. In said software, one or more pacing programs defined by one or more pacing sequences are defined for the control functions. The stimulation sequences are characterized by: a) the definition of the stimulation pulses for each of the stimulation channels of the implantable stimulator (1), b) the stimulation frequencies, whether or not they are independent for each stimulation channel and c ) the duration of these sequences. The definition of the pulses is characterized, although not limited, to the definition of the type of current pulse to be applied, containing a monophasic pulse with exponential recovery or a biphasic pulse. Additionally, each stimulation pulse may have one or more controlled current and step slopes associated, forming trapezoidal-looking pulses. For each pulse, the duration and amplitude of the current to be applied are specified. Each pacing channel has an associated pacing rate also definable in the software (12). The stimulation sequences allow specifying durations for each stimulation channel or a set of them, without containing stimulation pulses constituting burst stimulation.
El software (12) permite visualizar en una pantalla asociada al hardware de programación (13), las formas de onda de los pulsos en corriente y mantener una base de datos asociada a las secuencias definidas para las funciones de control para cada uno de los pacientes utilizando el sistema objeto de la invención de esta patente.The software (12) allows to visualize on a screen associated with the programming hardware (13), the waveforms of the pulses in current and to maintain an associated database to the sequences defined for the control functions for each of the patients using the system object of the invention of this patent.
Los parámetros de control de la estimulación definidos mediante el software (12) son transferidos a la unidad exte a portátil (15) mediante el enlace (14). Dicho enlace permite la transferencia de datos desde el hardware de programación (13) y la unidad extema portátil (15) utilizando conexión por cable, infrarrojos o enlace sin cables por telemetría, o cualquier combinación de los métodos mencionados. El software (12) permite al equipo médico la interrogación del estimulador implantable (1) para comprobar la impedancia de la interfase entre los electrodos y el tejido, detectando, cuando así sucediera, la rotura total o parcial del electrodo o del conector asociado a dicho electrodo mediante una variación grande de la impedancia medida. Esta medida permite además evaluar la evaluación de los electrodos después de su implantación durante el tiempo de maduración del implante y su evolución con el tiempo de implantación. La interrogación de la medida de impedancia de los electrodos se realiza mediante un comando transmitido desde el hardware de programación (13) hacía la unidad extema portátil (15) mediante el enlace (14) y la interrogación desde la unidad extema portátil (15) hacía el estimulador implantable (1) mediante acoplo inductivo (19). La respuesta desde el estimulador implantable sigue el camino contrario. La unidad extema portátil (15) es el mando que el paciente utiliza a su voluntad para el inicio de las funciones de control y que a su vez, es utilizado por el equipo médico para la determinación de los parámetros y secuencias de estimulación más adecuadas. Dicha unidad, es de tamaño reducido y ligero peso alimentado por una o varias baterías (16) siendo éstas recargables o no según se requiera. En el caso de baterías recargables, permite la conexión de un cargador de baterías mediante un conector convencional que imposibilita la utilización de la unidad extema portátil para controlar el estimulador implantable (1) durante la recarga.The stimulation control parameters defined by the software (12) are transferred to the outdoor unit (15) via the link (14). Said link allows data transfer from the programming hardware (13) and the portable external unit (15) using a wired, infrared or wireless link by telemetry, or any combination of the mentioned methods. The software (12) allows the medical team to interrogate the implantable stimulator (1) to check the impedance of the interface between the electrodes and the tissue, detecting, when this happens, the total or partial breakage of the electrode or the connector associated with said electrode by large variation of measured impedance. This measure also allows evaluating the evaluation of the electrodes after implantation during the maturation time of the implant and its evolution with implantation time. The interrogation of the electrode impedance measurement is carried out by means of a command transmitted from the programming hardware (13) to the portable external unit (15) through the link (14) and the interrogation from the portable external unit (15) the implantable stimulator (1) by inductive coupling (19). The response from the implantable stimulator follows the opposite path. The external portable unit (15) is the command that the patient uses at will to initiate control functions and which, in turn, is used by the medical team to determine the most appropriate parameters and stimulation sequences. Said unit is of reduced size and light weight powered by one or more batteries (16), these being rechargeable or not as required. In the case of rechargeable batteries, it allows the connection of a battery charger through a conventional connector that makes it impossible to use the external portable unit to control the implantable stimulator (1) during recharging.
La unidad extema portátil (15) contiene varios pulsadores (17) e interruptores permitiendo su encendido y el inicio de la transferencia de energía e información hacía y desde el estimulador implantable (1) mediante el acoplo inductivo (19) entre bobina o bobinas (18) de la unidad extema portátil (15) y bobina o bobinas (7) del estimulador implantable (1), a través de la piel y el tejido que separan ambos subsistemas. Dicho acoplo inductivo se realiza mediante circuitos resonantes serie o paralelo de tipo LC. La unidad extema portátil (15) está controlada normalmente mediante un microprocesador de bajo consumo que gestiona además la escritura y lectura de una memoria no volátil. Dicha memoria almacena la información referente a las secuencias que deben controlarse según las funciones de control e información estadística sobre el uso del implante por parte del paciente. Por lo tanto, el control que el paciente tienen sobre sus funciones de control no depende ni del software ni hardware de programación (12 y 13). Características adicionales de esta unidad son leds indicando la funciones de control requerida y la indicación mediante led o zumbido de un correcto posicionamiento del mando (15) respecto al estimulador implantable (1) garantizando energía suficiente en el implante y comunicación bidireccional correcta.The external portable unit (15) contains several pushbuttons (17) and switches allowing its ignition and the start of the transfer of energy and information to and from the implantable stimulator (1) by means of the inductive coupling (19) between coil or coils (18 ) of the portable external unit (15) and coil or coils (7) of the implantable stimulator (1), through the skin and tissue that separate the two subsystems. Said inductive coupling is carried out using LC type series or parallel resonant circuits. The portable external unit (15) is normally controlled by a low consumption microprocessor that also manages the writing and reading of non-volatile memory. Said memory stores the information regarding the sequences that must be controlled according to the control functions and statistical information on the use of the implant by the patient. Therefore, the control that the patient has over his control functions does not depend on the programming software or hardware (12 and 13). Additional characteristics of this unit are LEDs indicating the required control functions and the indication by LED or buzzer of a correct positioning of the command (15) with respect to the implantable stimulator (1) guaranteeing sufficient energy in the implant and correct bidirectional communication.
La parte implantable del sistema constituye el controlador para la estimulación de raíces sacras. Los distintos canales de estimulación del estimulador implantable (1) están conectados a los electrodos mediante un conector o conectares (10) preferiblemente de tipo marcapasos lo cual supone una mayor facilidad por parte del equipo médico encargado de la implantación del estimulador implantable (1). Dicho estimulador se encuentra encapsulado utilizando materiales biocompatibles preferiblemente utilizando un encapsulado cerámico permitiendo que los componentes electrónicos se encuentren junto al sistema de bobina o bobinas (7) para la recepción de energía y recepción y transmisión de datos reduciendo el tamaño total del implante. En el caso de utilizar un encapsulado de titanio, la bobina o bobinas para la recepción de energía en el estimulador implantable deben situarse de tal forma que se disminuya el posible efecto de reducción de energía debido a las interferencias del campo magnético con el titanio en el acoplo inductivo entre el sistema de bobinas (18) de la unidad extema portátil y el sistema de bobinas para la recepción de energía del estimulador implantable (1). Los componentes electrónicos del estimulador implantable están posicionados en una placa de circuito impreso o substrato (6). El control de la comunicación y control de los canales de estimulación vienen gobernados por un circuito integrado de aplicación específica, al que denominamos con el nombre genérico de ASIC (8). Dicho ASIC puede contener parte o totalidad del sistema de regulación (9), transmisor y receptor, y circuito de estimulación. El estimulador implantable (1) no está limitado a la utilización de circuito o circuitos integrados de aplicación específica pudiendo utilizarse adicionalmente o como complemento, uno o varios microcontroladores. En cualquier caso, es necesario que el controlador sea de bajo consumo para la disminución de la transferencia de energía desde la unidad extema portátil (15) hacía el estimulador implantable (1). Las ventajas principales de utilizar un ASIC para controlar el implante son, además del posible bajo consumo, la reducción del tamaño total del implante. Por otro lado, el diseño del ASIC utilizando tecnologías CMOS compatibles con procesos bipolares (BiCMOS) y DMOS permite una mayor integración de los componentes del estimulador implantable (1) al permitir tensiones de control mayores en los dispositivos. Las corrientes máximas necesarias para la estimulación de las raíces sacras y la impedancia electrodo-tejido implica la utilización de tensiones relativamente altas respecto a la tensión máxima drenador-surtidor de las tecnologías CMOS convencionales.The implantable part of the system constitutes the controller for the stimulation of sacral roots. The different stimulation channels of the implantable stimulator (1) are connected to the electrodes by means of a connector or connectors (10), preferably of the pacemaker type, which makes it easier for the medical team in charge of implantation of the implantable stimulator (1). Said stimulator is encapsulated using biocompatible materials, preferably using a ceramic encapsulation allowing the electronic components to be together with the coil system or coils (7) for energy reception and data reception and transmission, reducing the total size of the implant. In the case of using a titanium encapsulation, the coil or coils for the reception of energy in the implantable stimulator must be located in such a way that the possible effect of energy reduction is diminished due to the interference of the magnetic field with titanium in the inductive coupling between the coil system (18) of the portable external unit and the coil system for receiving energy from the implantable stimulator (1). The electronic components of the implantable stimulator are positioned on a printed circuit board or substrate (6). The communication control and control of the stimulation channels are governed by an integrated circuit of specific application, which we call with the generic name of ASIC (8). Said ASIC may contain part or all of the regulation system (9), transmitter and receiver, and stimulation circuit. The implantable stimulator (1) is not limited to the use of specific application circuits or integrated circuits and one or more microcontrollers can be used additionally or as a complement. In any case, it is necessary that the controller be of low consumption to decrease the energy transfer from the portable external unit (15) to the implantable stimulator (1). The main advantages of using an ASIC to control the implant are, in addition to the possible low consumption, the reduction of the total size of the implant. On the other hand, the design of the ASIC using CMOS technologies compatible with bipolar processes (BiCMOS) and DMOS allows a greater integration of the components of the implantable stimulator (1) by allowing higher control voltages in the devices. The maximum currents necessary for stimulation of the sacral roots and the electrode-tissue impedance implies the use of relatively high voltages with respect to the maximum drain-jet voltage of conventional CMOS technologies.
El estimulador implantable (1) vienen caracterizado, según figura 2, por un sistema de bobina o bobinas (7) que constituyen circuitos resonantes típicamente de tipo bobina- inductor (LC) que son utilizados para la recepción de energía y datos. La señal de radiofrecuencia generada desde la unidad extema portátil mediante un amplificador de potencia conectado al sistema de bobinas (18), es recibida en el sistema de bobinas (7) del implante y rectificada mediante un puente rectificador (29) conectado a capacidad o capacidades de almacenamiento. El puente rectificador es un rectificador de onda completa o un doblador de tensión. Asociado a esta tensión a la salida del puente rectificador (29) tenemos un limitador de tensión (30) que protege a los dispositivos, incluidos las capacidades asociadas, de sobretensión. El limitador de tensión (30) se caracteriza por tener un comportamiento similar a un zener pudiendo variar su implementación.The implantable stimulator (1) is characterized, according to figure 2, by a system of coil or coils (7) that constitute typically coil-inductor (LC) resonant circuits that are used for receiving energy and data. The radiofrequency signal generated from the portable external unit through a power amplifier connected to the coil system (18), is received in the coil system (7) of the implant and rectified by a rectifier bridge (29) connected to capacity or capacities. of storage. The bridge rectifier is a full wave rectifier or a voltage bender. Associated with this voltage at the output of the rectifier bridge (29) we have a voltage limiter (30) that protects the devices, including the associated capacities, from overvoltage. The voltage limiter (30) is characterized by having a behavior similar to a zener and its implementation may vary.
Debido al control para la reducción de energía transmitida a través de la piel que realiza la unidad extema portátil (15), el estimulador implantable (1) dispone de un sistema para la medición de la tensión (31) asociada al puente rectificador. Dicho sistema permite comparar con uno o varios niveles de referencia, notificando mediante comunicación desde el estimulador implantable (1) hacía la unidad extema portátil, el resultado de dicha comparación. La programación o fijación de los niveles de comparación utilizados en el medidor de tensión (31) así como la interrogación de dichos niveles por parte de la unidad extema portátil permite disminuir y controlar la potencia de transmisión necesaria según el funcionamiento en cada caso que tenga el estimulador implantable y en la situación de distancia y alineamiento entre bobinas (7 y 19) que haya. Por otro lado, dicho control permite al paciente conocer, mediante un zumbido o un led, que las bobinas han sido correctamente alineadas siendo la potencia recibida en el implante suficiente para su funcionamiento.Due to the control for the reduction of energy transmitted through the skin carried out by the portable external unit (15), the implantable stimulator (1) has a system for measuring the voltage (31) associated with the rectifier bridge. Said system allows comparing with one or several reference levels, notifying by communication from the implantable stimulator (1) to the external portable unit, the result of said comparison. The programming or setting of the comparison levels used in the voltage meter (31) as well as the interrogation of said levels by the external portable unit allows to decrease and control the necessary transmission power according to the operation in each case that has the implantable stimulator and in the distance and alignment situation between coils (7 and 19) that exist. On the other hand, said control allows the patient to know, by means of a buzzer or a led, that the coils have been correctly aligned, being the power received in the implant sufficient for its operation.
Debido a que el estimulador implantable (1), aún pudiendo estar alimentado parcialmente por una batería recargable, necesita de la transmisión de energía desde la unidad externa portátil (15), dispone de un circuito power-on-reset para asegurar su encendido. La implementación de dicho sistema pudiera ser, utilizando un simple circuito resistencia- capacitor RC conectado a la señal de reset del ASIC. Durante la fase de encendido del estimulador del implante (1), la circuitería garantiza, aunque la lógica de control (36) no este suficientemente alimentada, tensiones que no sobrepasan las tensiones máximas que permiten los dispositivos.Because the implantable stimulator (1), although it may be partially powered by a rechargeable battery, requires the transmission of energy from the portable external unit (15), it has a power-on-reset circuit to ensure its power on. The implementation of said system could be, using a simple RC resistor-capacitor circuit connected to the ASIC reset signal. During the ignition phase of the implant stimulator (1), the circuitry guarantees, although the control logic (36) is not sufficiently powered, voltages that do not exceed the maximum voltages allowed by the devices.
Por otro lado, la comunicación entre la unidad extema portátil (15) y el estimulador implantable (1) se realiza mediante acoplo inductivo entre el sistema de bobinas (18) y el sistema de bobinas (7). Para ello, el estimulador implantable (1) dispone de un transmisor (33) y receptor (34). El receptor (34) demodula y decodifica la información transmitida siendo interpretada por la lógica de control (36) como comandos para el control de la estimulación, parámetros de configuración del sistema implantado y peticiones de información del estimulador impíantable (1). Los comandos para el control de la estimulación son básicamente: el inicio de la generación de los pulsos de estimulación en corriente para uno o varios canales de estimulación, habilitación y deshabilitación de canales, definición de las formas de onda de estimulación y, habilitación y deshabilitación de la medida de impedancia de la interfase electrodo-tejido.On the other hand, communication between the portable external unit (15) and the implantable stimulator (1) is carried out by inductive coupling between the coil system (18) and the coil system (7). For this, the implantable stimulator (1) has a transmitter (33) and receiver (34). The receiver (34) demodulates and decodes the transmitted information, being interpreted by the control logic (36) as commands to control the stimulation, configuration parameters of the implanted system, and requests for information from the implantable stimulator (1). The commands for stimulation control are basically: the start of the generation of the current stimulation pulses for one or more stimulation channels, enabling and disabling channels, definition of the stimulation waveforms and, enabling and disabling of the impedance measurement of the electrode-tissue interface.
Los comandos de configuración principalmente están destinados al control de los niveles de comparación del medidor de tensión (31) para el control de la potencia entregada al implante y al ajuste fino de la tensión de referencia estable (35) utilizada en partes analógicas del ASIC (8).The configuration commands are mainly intended to control the comparison levels of the voltage meter (31) to control the power delivered to the implant and to fine-tune the stable reference voltage (35) used in analog parts of the ASIC ( 8).
La comunicación bidireccional entre el estimulador implantable (1) y la unidad extema portátil (15) se define síncrona entre ambos sistemas de forma que se simplifica los circuitos de demodulación y decodificación y evita o disminuye las posibles interferencias entre ambos canales de transmisión. Preferiblemente, aunque no limitado, se modula en ambos casos mediante modulación en amplitud de portadora. La portadora para la transferencia de información y datos desde la unidad extema portátil (15) hacía el estimulador implantable (1) es de una frecuencia mayor a la utilizada para la transmisión de datos desde el estimulador implantable. Dicho sistema evita que la señal de elevada potencia transmitida desde la unidad externa portátil y/o sus armónicos interfieran en el proceso de demodulación de la señal de baja potencia transmitida desde el estimulador implantable. En el caso de una modulación en amplitud con índice 100% de modulación, la detección de supresión de portadora por parte del receptor (34) del estimulador implantable, supone el inicio de la transmisión de datos utilizando el transmisor (33), mecanismo por el cual se establece la sincronización de la comunicación. El sistema de regulación (9) de tensiones en el estimulador implantable (1) está formado por reguladores lineales y convertidores de potencia DC/DC de tipo step-down. La tensión regulada para la etapa de salida del circuito de estimulación (90) proviene de la salida del puente rectificador (29) y limitada por (30). En dicha regulación se utilizan reguladores lineales y capacidades de almacenamiento y filtrado a la salida. El control de la tensión a la salida del puente rectificador (29) mediante el medidor de tensión (31) y control de potencia de salida del transmisor de la unidad extema portátil (15) permite el incremento de la eficiencia en potencia del regulador del estimulador (90). La salida del regulador del estimulador (90) viene asociada a uno o varios convertidores de potencia DC/DC de tipo step-down (91) para regular las tensiones necesarias para la lógica de control (36) y partes analógicas del ASIC (8) o componentes discretos necesarios, pudiendo haber entre dichas tensiones reguladas, otros sistemas de regulación o level- shifters para el control de partes del estimulador implantable (1).The bidirectional communication between the implantable stimulator (1) and the portable external unit (15) is defined synchronously between both systems so that the demodulation and decoding circuits are simplified and avoids or reduces possible interferences between both transmission channels. Preferably, although not limited, it is modulated in both cases by modulation in carrier amplitude. The carrier for the transfer of information and data from the external portable unit (15) to the implantable stimulator (1) is of a higher frequency than that used for data transmission from the implantable stimulator. Said system prevents the high power signal transmitted from the portable external unit and / or its harmonics from interfering with the demodulation process of the low power signal transmitted from the implantable stimulator. In the case of amplitude modulation with a 100% modulation index, the detection of carrier suppression by the receiver (34) of the implantable stimulator, supposes the start of data transmission using the transmitter (33), mechanism by the which establishes the timing of communication. The voltage regulation system (9) in the implantable stimulator (1) is made up of linear regulators and step-down DC / DC power converters. The regulated voltage for the output stage of the stimulation circuit (90) comes from the output of the rectifier bridge (29) and limited by (30). In this regulation, linear regulators and storage and filtering capacities are used at the output. Control of the voltage at the output of the rectifier bridge (29) by means of the voltage meter (31) and control of the output power of the transmitter of the external portable unit (15) allows the increase in power efficiency of the stimulator regulator (90). The output of the stimulator regulator (90) is associated with one or more step-down type DC / DC power converters (91) to regulate the voltages necessary for the control logic (36) and analog parts of the ASIC (8) or necessary discrete components, and there may be, between said regulated voltages, other regulation systems or level shifters for the control of parts of the implantable stimulator (1).
La utilización de convertidores de potencia DC/DC de tipo step-down incrementa la eficiencia en potencia del sistema debido a la diferencia en tensión entre la tensión necesaria para la generación de la estimulación en corriente y la tensión necesaria para alimentar la lógica de control, siendo ésta típicamente superior a 10 Volts.The use of step-down type DC / DC power converters increases the power efficiency of the system due to the difference in voltage between the voltage necessary to generate the current stimulation and the voltage necessary to supply the control logic, this being typically greater than 10 Volts.
La generación de los pulsos de estimulación en corriente es controlada por la lógica de control (36). Dicha lógica dispone de la información proveniente de la unidad extema portátil (15) referente a la forma de onda de los pulsos. Los pulsos en corriente son controlados mediante un convertidor D/A con salida en corriente basado en una referencia de corriente estable dependiente de la tensión de referencia (35). La corriente de salida del convertidor D/A (37) es multiplexada según el canal de estimulación a seleccionar mediante un multiplexor analógico (38) hacía un amplificador de corriente (39) por canal. Dicho amplificador constituye la etapa de salida de cada canal y se encuentra conectado al conector (10) mediante capacidades de desacoplo evitando tensiones DC en los electrodos. Los pulsos de estimulación pueden contener pendientes formando pulsos de estimulación trapezoidales. Estos pulsos son generados mediante escalones incrementando la corriente de salida en base a un factor programable mediante un simple contador implementado en la lógica de control (36). La recuperación de la carga inyectada a través de los electrodos se realiza mediante corriente controlada o recuperación exponencial. La resolución de la duración de los pulsos y de los escalones de corriente de salida viene fijada por la frecuencia del reloj del ASIC (8) o de un divisor de ésta. Dicho reloj proviene de un cristal conectado al ASIC (8) siendo habitualmente de 1 MHz de frecuencia.The generation of the current stimulation pulses is controlled by the control logic (36). Said logic has the information coming from the portable external unit (15) regarding the waveform of the pulses. The pulses in current are controlled by a D / A converter with current output based on a stable current reference dependent on the reference voltage (35). The output current of the D / A converter (37) is multiplexed according to the stimulation channel to be selected by means of an analog multiplexer (38) towards a current amplifier (39) per channel. Said amplifier constitutes the output stage of each channel and is connected to connector (10) by means of decoupling capabilities, avoiding DC voltages at the electrodes. The pacing pulses may contain slopes forming trapezoidal pacing pulses. These pulses are generated by steps increasing the output current based on a programmable factor by means of a simple counter implemented in the control logic (36). The recovery of the charge injected through the electrodes is carried out using controlled current or exponential recovery. The resolution of the duration of the pulses and the output current steps is fixed by the clock frequency of the ASIC (8) or a divisor of this. Said clock comes from a crystal connected to the ASIC (8), usually being 1 MHz in frequency.
Los parámetros que definen los pulsos de estimulación son al mínimo: la duración de los pulsos, la magnitud de la corriente de salida y la existencia o no de escalones de corriente y su definición. Dichos parámetros son independientes para cada uno de los canales de estimulación.The parameters that define the stimulation pulses are at a minimum: the duration of the pulses, the magnitude of the output current and the existence or not of current steps and their definition. These parameters are independent for each of the stimulation channels.
El control de las frecuencias de estimulación es controlado por la unidad extema portátil (15) reduciendo la lógica de control (36). Existe un comando de datos transmitido desde la unidad extema portátil por el cual se especifican los canales que deben estimularse. Cuando dicho comando especifique más de un canal a estimular y la arquitectura del estimulador implantable se base en un único convertidor D/A (37), los pulsos de estimulación son multiplexados en el tiempo. En dicho caso, la prioridad viene fijada por el orden (número) asociado a los canales de estimulación.The control of the stimulation frequencies is controlled by the external portable unit (15) reducing the control logic (36). There is a data command transmitted from the portable external unit by which the channels to be stimulated are specified. When said command specifies more than one channel to stimulate and the architecture of the implantable stimulator is based on a single D / A converter (37), the stimulation pulses are multiplexed in time. In this case, the priority is set by the order (number) associated with the stimulation channels.
5. Ejemplo de realización de la invención5. Example of embodiment of the invention
A continuación se detalla como ejemplo de realización un sistema de estimulación de raíces sacras mediante implante alimentado por radio frecuencia, cuyas características son:The following is an example of embodiment of a sacral root stimulation system using an implant fed by radio frequency, the characteristics of which are:
- Software de programación (12) basado en Windows 98 ™ - Hardware de programación (13) basado en un ordenador personal.- Programming software (12) based on Windows 98 ™ - Programming hardware (13) based on a personal computer.
- Enlace entre el hardware de programación y la unidad extema portátil (15) mediante cable con conector RJ-45. - Unidad extema portátil (15) alimentada por una única pila 9V en caja de plástico conteniendo tres pulsadores (17) asociado a cada una de las tres funciones de control del sistema y dos leds. Los leds indican que la transferencia de energía es suficiente y que la transmisión de datos es correcta. Incorpora una memoria no volátil de tipo EEPROM para el almacenamiento de programas y secuencias de estimulación. La gestión de dicha memoria así como la comunicación con el hardware de programación y el control de frecuencias esta implementado en un microprocesador. Existe un segundo microcontrolador encargado de la generación de los paquetes de datos a transmitir y la recepción de datos desde el estimulador implantable (1) comunicado con el primero y que gestiona además los leds indicadores.- Link between the programming hardware and the portable external unit (15) by cable with an RJ-45 connector. - External portable unit (15) powered by a single 9V battery in a plastic box containing three buttons (17) associated with each of the three system control functions and two LEDs. The LEDs indicate that the energy transfer is sufficient and that the data transmission is correct. It incorporates a non-volatile memory of EEPROM type for the storage of programs and stimulation sequences. The management of said memory as well as the communication with the programming hardware and the frequency control is implemented in a microprocessor. There is a second microcontroller in charge of generating the data packets to be transmitted and receiving data from the implantable stimulator (1) communicated with the first one and which also manages the indicator LEDs.
- Acoplo inductivo entre una bobina (18) de la unidad extema portátil y una bobina (7) del estimulador implantable (1) para la recepción de energía y datos en el estimulador implantable. - Acoplo inductivo entre una bobina (18) del estimulador implantable (1) y una bobina (18) de la unidad extema portátil para la recepción de información en la unidad extema portátil. - Inductive coupling between a coil (18) of the portable external unit and a coil (7) of the implantable stimulator (1) for the reception of energy and data in the implantable stimulator. - Inductive coupling between a coil (18) of the implantable stimulator (1) and a coil (18) of the portable external unit for receiving information on the portable external unit.
- Estimulador implantable (1) con encapsulado (5) de epoxy conteniendo las dos bobinas (7) anteriormente mencionadas y con placa de circuito impreso como substrato (6) y cuyo circuito integrado de aplicación especifica, ASIC (8), contiene: - lógica de control (36),- Implantable stimulator (1) with epoxy encapsulation (5) containing the two coils (7) previously mentioned and with a printed circuit board as substrate (6) and whose specific application integrated circuit, ASIC (8), contains: - logic control (36),
- tensión de referencia estable (35),- stable reference voltage (35),
- receptor (34) y transmisor (33),- receiver (34) and transmitter (33),
- Un único convertidor D/A (37) de 7 bits con salida en corriente y multiplexación (38) hacía tres canales de estimulación mediante tres amplificadores de corriente (39) dando corrientes máxima de salida de 40mA por canal con 16V regulados para unos límites de impedancia electrodo-tejido.- A single 7-bit D / A converter (37) with current output and multiplexing (38) made three stimulation channels by means of three current amplifiers (39) giving a maximum output current of 40mA per channel with 16V regulated for limits electrode-tissue impedance.
- Limitador de tensión a la salida del puente rectificador (29) de 24V.- Voltage limiter at the output of the 24V rectifier bridge (29).
- Medidor de la tensión no regulada proveniente del puente rectificador (29) utilizando dos niveles de comparación determinando si la tensión de entrada es mayor que 14V siendo suficiente para la alimentación de la lógica de control (36) o mínima de 18 V para garantizar los 16V del sistema de regulación.- Unregulated voltage meter from the rectifier bridge (29) using two levels of comparison determining if the input voltage is greater than 14V, being sufficient to supply the control logic (36) or a minimum of 18 V to guarantee the 16V of the regulation system.
- Medidor de la impedancia (40) electrodo-tejido mediante convertidor de 1 bit.- Electrode-tissue impedance meter (40) using a 1-bit converter.
- Power-on-reset integrado con conexión adicional extema para testeo del ASIC.- Integrated power-on-reset with additional external connection for ASIC testing.
- Conector (10) para conexión de tres electrodos bipolares (11).- Connector (10) for connection of three bipolar electrodes (11).
- Regulador lineal conectado al puente rectificador (29) y cuya salida proporciona 16V regulados para los canales de estimulación.- Linear regulator connected to the rectifier bridge (29) and whose output provides regulated 16V for the stimulation channels.
- Convertidor de potencia DC DC de tipo step-down suministrando 5V regulados para la lógica de control (36) y partes analógicas del ASIC (8).- Step-down type DC DC power converter supplying regulated 5V for the control logic (36) and analog parts of the ASIC (8).
Para dicho sistema, la frecuencia del reloj del ASIC (8) es de un 1.00 MHz proveniente de un cristal y la duración de los pulsos de estimulación se definen mediante 8 bits definiendo pulsos de estimulación entre 4 us y 1024 us con paso de 4 us fijados por la división por cuatro de la frecuencia del cristal. Los pulsos de estimulación son monofásicos con recuperación de carga exponencial y la duración de los escalones en los pulsos trapezoidales son calculados en base a un incremento definido también con 8 bits. La duración de cada escalón es exactamente 4 us y el incremento en corriente el especificado siendo la duración limitada por la amplitud máxima o por la duración del pulso de estimulación.For this system, the ASIC (8) clock frequency is 1.00 MHz from a crystal and the duration of the stimulation pulses are defined by 8 bits defining stimulation pulses between 4 us and 1024 us with a step of 4 us set by dividing the crystal frequency by four. The stimulation pulses are single phase with exponential load recovery and the duration of the steps in the trapezoidal pulses are calculated based on an increment defined also with 8 bits. The duration of each step is exactly 4 us and the increase in current is the specified one, the duration being limited by the maximum amplitude or by the duration of the stimulation pulse.
La información independiente para cada canal controlada en el ASIC es la existencia o no de escalones constituyendo pulsos de estimulación de forma trapezoidal, la amplitud o incremento del escalón y la duración del pulso. La unidad extema portátil controla las frecuencias de estimulación y los tiempos de ráfagas habilitando o deshabilitando los canales mediante un comando a través del acoplo inductivo (19). Las frecuencias de estimulación se encuentran basadas en un cristal de 32.768 Khz conectado al primero de los microcontroladores fijando frecuencias de estimulación entre 1Hz y 120Hz con paso de lHz. La transmisión de potencia desde la unidad extema portátil hacía el estimulador implantable se realiza mediante un amplificador de potencia de clase-E utilizando una portadora de 6 MHz cuya tensión de alimentación máxima es controlada según el control de potencia requerido y cuya tensión de alimentación mínima es 0V modulando la portadora en amplitud con índice de modulación 100%. La codificación de los pulsos es por anchura de pulso. En la figura 3, se muestra la implementación del convertidor D/A con salida en corriente cuya corriente de referencia depende de la tensión de referencia estable (35), denominada tensión de bandgap (VBG). Los interruptores B6 hasta B0 son los bits de control de la corriente de salida. El multiplexador de canales (38) está implementado utilizando interruptores analógicos (Chl, Ch2 y Ch3) de baja resistencia. La resistencia Rp y CtrlP permiten mantener una impedancia equivalente a la que tendrá la salida del convertidor A/D cuando uno de los canales Chl, Ch2 o Ch3 se active. La secuencia de control es encender la referencia de corriente, aplicar el código de control con B6 .. B0 y activar Ctrlp. Posteriormente, se conmuta entre CtrlP y uno de los canales Chl, Ch2 o Ch3. De esta forma se disminuyen los picos de corriente a la salida del convertidor D/A. Las salidas en corriente II, 12 y 13 son conectadas a tres amplificadores de corriente como los que muestra la figura 4. Así, cada canal de estimulación tiene asociado un espejo de corriente de relación 1 :n implementado con bipolares cuyo factor de multiplicación de la corriente es suficiente para suministrar los 40mA. La figura 4, también muestra el esquema de conexión de dicho canal de estimulación hacía el conector bipolar utilizado. El interruptor SI se conecta cuando se habilita la corriente de entrada (Icanal) permaneciendo S2 desconectado. En dicha situación, la corriente de entrada se mantiene durante la duración fijada por los parámetros del canal pudiendo contener además variaciones en Icanal debido a cambios del código B6..B0 del convertidor D/A generando escalones de corriente a la salida. Durante la recuperación de carga SI pasa a desconectado y el interruptor S2 cortocircuita ambos extremos del electrodo. Los ánodos y cátodos de los electrodos están conectados al conector (10). En la figura 4, dicho canal tiene el ánodo del electrodo conectado al punto medio de los interruptores SI y S2. El cátodo está asociado a la capacidad de desacoplo. El interruptor SI conecta la alimentación regulada para el estimulador (Vstim) de 16V hacía el ánodo. El nodo Vmedida es utilizado para la medida de la impedancia según el esquema de la figura 5. En la figura 5 se muestra como cada canal tiene asociado su propio Vmedida y como estos son multiplexados mediante otros tres intermptores SI, S2 y S3. La medida de impedancia sólo es posible realizarla en un único canal de estimulación a la vez. El interruptor Soff asegura el nivel de entrada inicial al comparador de alta tensión (16V). Dicho comparador compara la Vmedida seleccionada con una tensión estable que depende de la tensión de referencia estable (35) del ASIC (8). El adaptador de nivel convierte la salida del comparador en una señal de nivel lógico compatible CMOS. La deshabilitación de la medida de impedancia supone la desconexión de SI, S2 y S3 y la activación de Soff, así como la deshabilitación del comparador y el adaptador de nivel. Este mecanismo supone la reducción del consumo del ASIC. Puesto que el comparador es de hecho un convertidor de 1 bit, la medida de la impedancia se realiza programando una secuencia de estímulos de amplitud distinta haciendo un barrido y detectando para que pulso de corriente el comparador a conmutado su resultado. Las medidas de impedancia son controladas mediante el software (12) utilizando un ordenador personal (13) conectado a la unidad extema portátil mediante un cable a través de comunicación serial RS-232C. El software muestra y almacena las medidas de impedancia para cada uno de los tres canales.The independent information for each channel controlled in the ASIC is the existence or not of steps constituting trapezoidal stimulation pulses, the amplitude or increase of the step and the duration of the pulse. The external portable unit controls the stimulation frequencies and the burst times, enabling or disabling the channels by means of a command through the inductive coupling (19). The stimulation frequencies are based on a 32,768 Khz crystal connected to the first of the microcontrollers, setting stimulation frequencies between 1Hz and 120Hz with a step of lHz. The transmission of power from the portable external unit to the implantable stimulator is carried out by means of an E-class power amplifier using a 6 MHz carrier whose maximum supply voltage is controlled according to the required power control and whose minimum supply voltage is 0V modulating the carrier in amplitude with modulation index 100%. The encoding of the pulses is by pulse width. Figure 3 shows the implementation of the D / A converter with current output whose reference current depends on the stable reference voltage (35), called bandgap voltage (VBG). Switches B6 through B0 are the control bits for the output current. The channel multiplexer (38) is implemented using low resistance analog switches (Chl, Ch2 and Ch3). The resistance Rp and CtrlP allow maintaining an impedance equivalent to what the output of the A / D converter will have when one of the Chl, Ch2 or Ch3 channels is activated. The control sequence is to turn on the current reference, apply the control code with B6 .. B0 and activate Ctrlp. Subsequently, it is switched between CtrlP and one of the Chl, Ch2 or Ch3 channels. This reduces current peaks at the output of the D / A converter. The current outputs II, 12 and 13 are connected to three current amplifiers such as those shown in figure 4. Thus, each stimulation channel has an associated 1: n ratio current mirror implemented with bipolars whose multiplication factor of the current is sufficient to supply 40mA. Figure 4 also shows the connection diagram of said stimulation channel to the bipolar connector used. The SI switch is connected when the input current (Channel) is enabled, while S2 remains disconnected. In this situation, the input current is maintained for the duration set by the channel parameters, and may also contain variations in channel due to changes in the B6..B0 code of the D / A converter, generating current steps at the output. During load recovery SI goes off and switch S2 short circuits both ends of the electrode. The anodes and cathodes of the electrodes are connected to the connector (10). In figure 4, said channel has the electrode anode connected to the midpoint of switches SI and S2. The cathode is associated with the decoupling capacity. The SI switch connects the regulated supply for the 16V stimulator (Vstim) to the anode. The Vmeasure node is used to measure the impedance according to the diagram in figure 5. In figure 5 it is shown how each channel has its own Vmeasure associated and how these are multiplexed by means of three other switches SI, S2 and S3. The impedance measurement can only be performed on a single stimulation channel at a time. The Soff switch ensures the initial input level to the high voltage comparator (16V). Said comparator compares the selected V measurement with a stable voltage that depends on the stable reference voltage (35) of the ASIC (8). The level adapter converts the comparator output into a CMOS compatible logic level signal. Disabling the impedance measurement supposes the disconnection of SI, S2 and S3 and the activation of Soff, as well as the disabling of the comparator and the level adapter. This mechanism supposes the reduction of the consumption of the ASIC. Since the comparator is in fact a 1-bit converter, the measurement of the impedance is made by programming a sequence of stimuli of different amplitude by sweeping and detecting for which current pulse the comparator has switched its result. Impedance measurements are controlled by software (12) using a personal computer (13) connected to the portable external unit by means of a cable through RS-232C serial communication. The software displays and stores the impedance measurements for each of the three channels.
Para la recepción y regulación de la tensiones de estimulación y de alimentación del ASIC, se utiliza un esquema simplificado en la figura 6. El circuito receptor de energía esta basado en un circuito paralelo resonante a 6MHz formando parte del sistema de bobinas (7) del estimulador implantable (1). La señal de radio frecuencia, proveniente del amplificador de potencia de clase E de la unidad extema portátil, es rectificada mediante un rectificador de onda completa (29), Dicho rectificador tiene asociado al menos una capacidad de almacenamiento 47uF/25V cuyo limitador de tensión (30) evita tensiones mayores de 23-24V. La arquitectura del limitador de tensión está basada en una cadena de bipolares actuando como zeners y un NMOS de potencia. La resistencia tiene una impedancia mucho mayor que la del zener equivalente cuando la tensión es superior a la que limita (alrededor 22 V). En dicho estado, el NMOS actúa y el amplificador en configuración darlington conduce la corriente hacía la tierra del circuito. El lazo de control de la potencia de transmisión desde la unidad extema portátil evita que dicha situación ocurra para evitar perdida de energía innecesaria. Para ello, se elige un nodo de la cadena de bipolares del limitador de potencia de forma que ofrezca un tensión directamente proporcional y aproximadamente lineal a la tensión rectificada en el puente rectificador y cuya tensión este por debajo de 5V para la máxima tensión permitida por el limitador. Esta tensión es utilizada por el medidor de tensión (31) para comparada con una tensión de referencia variable y seleccionable entre dos niveles que indican una tensión a la salida del puente rectificador menor de 14V o superior a 18V. El resultado de dicha comparación es enviando a la unidad extema portátil cuando está lo solicita. Para este ejemplo, la indicación de una tensión no inferior a 14V garantiza que la parte digital y analógica del ASIC funciona y los parámetros transmitidos no se han perdido por falta de alimentación. Por otro lado, la indicación de tensión superior a 18V indica que el implante dispone de suficiente energía para garantizar el amplio rango de corrientes de salida. La tensión de salida del puente rectificador es la entrada del regulador lineal de 16V. Dicha tensión es utilizada para la etapa de salida del estimulador en corriente (Vstim). Del nodo Vstim conectamos un convertidor de potencia DC/DC de tipo step-down cuya salida alimenta las partes que no son de potencia en el ASIC. Un esquema para el control de recepción y transmisión de datos en el estimulador implantable es mostrado en la figura 7. La bobina asociada a la recepción de datos es la misma que la utilizada para la recepción de energía. El ASIC incorpora un filtro pasa bajos para eliminar la portadora de 6MHZ transmitida desde la unidad extema portátil. Dicho filtro que tiene asociado un comparador da como salida una señal de niveles de tensión 0-5V según la existencia o no de portadora respectivamente. La supresión de portadora supone un cambio en el nivel de salida del filtro y se inicia la cuenta en el contador- 1. Cada uno de los contadores de la figura 7, tiene como nivel de salida un 'Y lógica durante la no activación y un nivel lógico '0' después del fin de cuenta. La implementación de dichos contadores puede ser o bien mediante un contador a la frecuencia del reloj del ASIC, 1MHZ, o bien mediante descargas controladas de una cierta capacidad a corriente constante y comparador a su salida. Por lo tanto, un tiempo suficientemente corto con supresión de portadora no genera variación algunos en los contadores. Alargado el tiempo de supresión de portadora, el contador-1 pasa a '0' lógico hasta que la recepción de portadora se restablece generando entonces un flanco que es utilizado para capturar el dato recibido en un flip-flop. El dato recibido es T' cuando el tiempo ha sido suficientemente corto como para general el flanco del flip-flop o '0' cuando ha sido mayor que la cuenta en el contador-2 generada a partir del flanco en el contador- 1. El mismo proceso con supresión de portadora de duración mayor establece dos señales más indicando inicio del paquete de datos o inicio de las comunicaciones. El símbolo de inicio de comunicaciones se establece como seguridad durante la elevación de las tensiones en el estimulador implantable definiendo al menos la recepción de dos inicios de comunicaciones antes de considerar los paquetes de datos como información útil.For the reception and regulation of the stimulation and supply voltages of the ASIC, a simplified scheme is used in figure 6. The energy receiver circuit It is based on a 6MHz resonant parallel circuit forming part of the coil system (7) of the implantable stimulator (1). The radio frequency signal, coming from the class E power amplifier of the portable external unit, is rectified by means of a full-wave rectifier (29), said rectifier has associated with at least a 47uF / 25V storage capacity whose voltage limiter ( 30) avoid voltages greater than 23-24V. The voltage limiter architecture is based on a bipolar chain acting as zeners and a power NMOS. The resistance has a much higher impedance than that of the equivalent zener when the voltage is higher than the limiting one (around 22 V). In this state, the NMOS operates and the amplifier in the darlington configuration conducts the current to the circuit ground. The transmission power control loop from the portable external unit prevents this situation from occurring to avoid unnecessary energy loss. For this, a node of the bipolar chain of the power limiter is chosen so that it offers a voltage directly proportional and approximately linear to the rectified voltage in the rectifier bridge and whose voltage is below 5V for the maximum voltage allowed by the limiter. This voltage is used by the voltage meter (31) to compare with a variable and selectable reference voltage between two levels that indicate a voltage at the rectifier bridge output less than 14V or greater than 18V. The result of such comparison is sending to the portable external unit when requested. For this example, the indication of a voltage not lower than 14V guarantees that the digital and analog part of the ASIC works and the transmitted parameters have not been lost due to lack of power. On the other hand, the voltage indication above 18V indicates that the implant has enough energy to guarantee the wide range of output currents. The output voltage of the rectifier bridge is the input of the 16V linear regulator. This voltage is used for the current stimulator output stage (Vstim). From the Vstim node we connect a step-down type DC / DC power converter whose output feeds the non-power parts in the ASIC. A scheme for the control of reception and transmission of data in the implantable stimulator is shown in Figure 7. The coil associated with the reception of data is the same as that used for the reception of energy. The ASIC incorporates a low pass filter to eliminate the 6MHZ carrier transmitted from the portable external unit. Said filter, associated with a comparator, outputs a signal of 0-5V voltage levels depending on the existence or not of the carrier, respectively. The suppression of the carrier supposes a change in the output level of the filter and the count is started in the counter- 1. Each one of the counters in figure 7 has as its output level a logical 'Y' during non-activation and a logical level '0' after the end of the count. The implementation of said counters can be either by means of a counter at the ASIC clock frequency, 1MHZ, or by controlled discharges of a certain capacity at constant current and comparator at its output. Therefore, a sufficiently short time with carrier suppression does not generate any variation in the counters. With the carrier suppression time lengthened, counter-1 goes to logical '0' until carrier reception is restored, then generating an edge that is used to capture the received data in a flip-flop. The data received is T 'when the time has been short enough to generate the edge of the flip-flop or' 0 'when it has been greater than the count in counter-2 generated from the edge in counter-1. The same process with carrier suppression of longer duration establishes two more signals indicating start of the data packet or start of communications. The communications start symbol is established as security during the rise of the voltages in the implantable stimulator, defining at least the reception of two communications starts before considering the data packets as useful information.
Finalmente, la figura 7 muestra también la conexión a una segunda bobina del sistema de bobinas (7) del estimulador implantable con la que se transmite información hacía la unidad extema portátil. En este caso, un simple amplificador de potencia de clase B es utilizado como transmisor. La lógica a la entrada del transmisor permite asegurar que el transmisor está apagado durante el tiempo de power-on-reset del ASIC. La señal CLK referencia el propio reloj de 1MHz obtenido del cristal asociado al ASIC. El dato a transmitir habilita el transmisor durante un determinado tiempo fijado por el contador-5. Los datos desde el estimulador implantable son codificados utilizando código Manchester. La sincronización entre la unidad extema portátil y el estimulador implantable permite al microprocesador de la unidad extema portátil limitar el tiempo en que debe esperar una respuesta y controlar los errores de transmisión y recepción mediante el reenvío de los paquetes de datos. Finally, figure 7 also shows the connection to a second coil of the coil system (7) of the implantable stimulator with which information is transmitted to the portable external unit. In this case, a simple class B power amplifier is used as a transmitter. The logic at the transmitter input ensures that the transmitter is turned off during the ASIC power-on-reset time. The CLK signal references the 1MHz clock itself obtained from the crystal associated with the ASIC. The data to be transmitted enables the transmitter for a certain time set by counter-5. Data from the implantable stimulator is coded using Manchester code. Synchronization between the portable external unit and the implantable stimulator allows the microprocessor of the portable external unit to limit the time to wait for a response and to control transmission and reception errors by forwarding the data packets.

Claims

6. Reivindicaciones6. Claims
1) Sistema de estimulación en corriente para el control de la micción, defecación y erección en pacientes con neuropatías y en particular para lesionados medulares mediante la estimulación de las raíces sacras, alimentado por radiofrecuencia caracterizado porque consta de: a) Dispositivo estimulador implantable (1), al que denominaremos implante, basado en un circuito integrado de aplicación especifica (8), al que denominamos como ASIC. El implante está formado por el ASIC, una o varias bobinas (7), componentes electrónicos discretos, placa de circuito impreso o substrato (6) para la ubicación de todos los componentes electrónicos, un encapsulado de material biocompatible (5) y un conector (10) para la fijación de los electrodos para cada uno de los canales de estimulación mediante un conector preferiblemente de tipo marcapasos. El implante es alimentado por radio frecuencia mediante acoplo inductivo (19) entre una bobina del implante (7) y una o varias bobinas (18) de la unidad extema portátil (15) pudiendo ser además alimentado parcialmente mediante una batería recargable. El implante dispone de varios canales de estimulación en corriente, medidor de la impedancia de la interficie electrodo-tejido, medidor de la tensión inducida en la bobina, un sistema de comunicación bidireccional mediante radio frecuencia y un sistema de regulación de las tensiones necesarias para la circuitería de estimulación y la parte de lógica digital y parte analógica del ASIC. El ASIC (8) incluye la mayor parte o totalidad de la circuitería de estimulación, medidor de impedancia, medidor de la tensión inducida en la bobina (7), el sistema bidireccional de comunicación y el control digital de todas estas partes, pudiendo además contener parte o la totalidad del sistema de regulación (9) de las alimentaciones en el implante. b) Electrodos (11) con conexión al estimulador a través del conector del implante (10). c) Software (12) para la programación de las secuencias y programas de estimulación, control de base de datos de pacientes, interrogación del implante, análisis estadístico de las bases de datos, programación de la unidad extema portátil y verificación de los parámetros de la unidad extema portátil. d) Hardware de programación (13) capaz de ejecutar el software mencionado en el párrafo anterior y que puede recibir o enviar cualquiera de esos datos a la unidad extema portátil (15). La conexión o enlace (14) entre el hardware de programación (13) y la unidad externa portátil (15) se realiza mediante cable, enlace de radio frecuencia o enlace por infrarrojos. El hardware de programación (13) es habitualmente un ordenador personal. e) Unidad extema portátil (15) controlada por microcontrolador o cualquier otro hardware programable o circuito integrado de aplicación especifica cuya función sea el envío y recepción de los datos, secuencias y programas provenientes del hardware de programación, y el envío y recepción de información hacía y desde el implante. La unidad externa portátil incluye una o varias baterías recargables o no recargables (16) alimentado toda la circuitería, y un transmisor y receptor conectados a una o varias bobinas (18) constituyendo un enlace de radio frecuencia sin cables mediante acoplo inductivo (19) entre las bobinas de la unidad extema portátil (18) y el sistema de bobinas (7) del implante. Además, la unidad extema portátil incluye varios pulsadores (17) para la activación del envío y recepción de parámetros hacía y desde el implante (1) y memoria de tipo no volátil para almacenar los parámetros recibidos desde el hardware de programación (13). Una vez transmitidos los parámetros desde el hardware de programación (13) hacía la unidad extema portátil (15), dicha unidad es independiente del hardware de programación y es utilizada por la persona que tiene el implante (1) para la activación de los programas asociados a las funciones de micción, defecación y erección.1) Current stimulation system for the control of urination, defecation and erection in patients with neuropathies and in particular for spinal cord injuries through the stimulation of the sacral roots, fed by radiofrequency characterized in that it consists of: a) Implantable stimulator device (1 ), which we will call implant, based on a specific application integrated circuit (8), which we call as ASIC. The implant is formed by the ASIC, one or several coils (7), discrete electronic components, printed circuit board or substrate (6) for the location of all electronic components, a biocompatible material package (5) and a connector ( 10) for the fixation of the electrodes for each of the stimulation channels by means of a connector preferably of pacemaker type. The implant is fed by radio frequency by inductive coupling (19) between a coil of the implant (7) and one or several coils (18) of the external portable unit (15) and can also be partially powered by a rechargeable battery. The implant has several current stimulation channels, electrode-tissue interface impedance meter, coil induced voltage meter, a two-way radio frequency communication system and a voltage regulation system necessary for the stimulation circuitry and the digital logic and analog part of the ASIC. The ASIC (8) includes most or all of the stimulation circuitry, impedance meter, coil induced voltage meter (7), the two-way communication system and the digital control of all these parts, and may also contain part or all of the regulation system (9) of the feeds in the implant. b) Electrodes (11) with connection to the stimulator through the implant connector (10). c) Software (12) for programming sequences and stimulation programs, patient database control, interrogation of the implant, statistical analysis of the databases, programming of the portable external unit and verification of the parameters of the portable outdoor unit. d) Programming hardware (13) capable of executing the software mentioned in the previous paragraph and that can receive or send any of this data to the portable external unit (15). The connection or link (14) between the programming hardware (13) and the portable external unit (15) is made by cable, radio frequency link or infrared link. The programming hardware (13) is usually a personal computer. e) Portable external unit (15) controlled by microcontroller or any other programmable hardware or specific application integrated circuit whose function is the sending and receiving of data, sequences and programs from the programming hardware, and the sending and receiving of information to and from the implant. The portable external unit includes one or several rechargeable or non-rechargeable batteries (16) powered by the entire circuitry, and a transmitter and receiver connected to one or several coils (18) constituting a radio frequency link without wires by means of inductive coupling (19) between the coils of the portable external unit (18) and the coil system (7) of the implant. In addition, the external portable unit includes several push-buttons (17) for activating the sending and receiving of parameters to and from the implant (1) and non-volatile type memory for storing the parameters received from the programming hardware (13). Once the parameters have been transmitted from the programming hardware (13) to the external portable unit (15), said unit is independent of the programming hardware and is used by the person who has the implant (1) for the activation of the associated programs to the functions of urination, defecation and erection.
2) Sistema según reivindicación 1 caracterizado porque: en los canales de estimulación en corriente se reivindica que la generación de los pulsos de estimulación en corriente son controladas por el ASIC (8) mediante al menos un convertidor digital-analógico (DA) con salida en corriente y mediante una etapa de amplificación de dicha corriente, siendo la corriente de salida independiente del acoplo inductivo (19) entre la o las bobinas del implante (7) y las bobinas extemas de la unidad extema portátil (15). Y que en el caso de un único convertidor D/A, éste es multiplexado según el control digital del ASIC no permitiendo más de un pulso de estimulación simultáneo. Además, el inicio de los pulsos de estimulación sólo se produce cuando el sistema de recepción de datos del implante recibe un comando indicando que canales deben iniciar un pulso de estimulación. No obstante, el ASIC podría contener el control de las frecuencias de estimulación decidiendo el orden por el cual los canales deben contener pulsos de estimulación evitando de nuevo la generación de pulsos de estimulación simultáneos en varios canales. Los pulsos de estimulación en corriente son bifásicos y pueden tener o no, escalones de pendiente cuya variación en corriente de un escalón al siguiente depende de parámetros recibidos desde la unidad extema portátil. La recuperación de carga inyectada a través de los electrodos es realizada mediante corriente controlada o recuperación exponencial. La resolución de la duración de los pulsos y de los escalones es exactamente la obtenida con la frecuencia del reloj del ASIC o un divisor de ésta. El reloj obtenido en el ASIC proviene de un cristal conectado a este y dicho cristal es normalmente de 1 MHz de frecuencia. Los parámetros que definen los pulsos de estimulación son principalmente amplitud de corriente, duración y existencia o no de escalones siendo todos ellos independientes para cada uno de los canales de estimulación.2) System according to claim 1 characterized in that: in the current stimulation channels it is claimed that the generation of the current stimulation pulses are controlled by the ASIC (8) by at least one digital-analog converter (DA) with output in current and by means of an amplification stage of said current, the output current being independent of the inductive coupling (19) between the coil (s) of the implant (7) and the external coils of the portable external unit (15). And that in the case of a single D / A converter, it is multiplexed according to the ASIC digital control allowing no more than one simultaneous stimulation pulse. In addition, the beginning of the pulses Stimulation occurs only when the implant data reception system receives a command indicating which channels should initiate a stimulation pulse. However, the ASIC could contain the control of the stimulation frequencies by deciding the order in which the channels must contain stimulation pulses again avoiding the generation of simultaneous stimulation pulses in several channels. The current stimulation pulses are biphasic and may or may not have slope steps whose current variation from one step to the next depends on parameters received from the portable outdoor unit. The recovery of charge injected through the electrodes is performed by controlled current or exponential recovery. The resolution of the duration of the pulses and the steps is exactly that obtained with the frequency of the ASIC clock or a divider thereof. The clock obtained in the ASIC comes from a crystal connected to it and said crystal is normally 1 MHz in frequency. The parameters that define the stimulation pulses are mainly current amplitude, duration and existence or not of steps being all independent for each of the stimulation channels.
3) Sistema según reivindicación 1, caracterizado porque: la comunicación bidireccional entre la unidad extema portátil y el implante se realiza mediante un enlace sin cables por acoplo inductivo (19) entre bobina o bobinas (18) de la unidad externa portátil y sistema de bobinas (7) del implante. Y que dicha comunicación es síncrona utilizando en ambos casos modulación en amplitud de una portadora y cuya codificación se basa en la utilización de dos niveles de amplitud de la portadora. La sincronización se establece iniciando la transmisión de información desde el implante cuando la unidad extema portátil está utilizando su nivel de amplitud de portadora mínima. Además, la portadora del transmisor de la unidad extema portátil es siempre de una frecuencia mayor a la portadora utilizada en el transmisor del implante evitando que la señal de mayor potencia correspondiente a la del transmisor de la unidad externa portátil, interfiera en la transmisión de bajo consumo desde el implante (1) y a su recepción en la unidad extema portátil (15). Los datos enviados y recibidos desde la unidad extema portátil corresponden a los parámetros de programación de los pulsos de estimulación en corriente, comandos de inicio y paro de dichos pulsos, inicio o lectura de la medida de la impedancia, lectura de la tensión inducida en la bobina de recepción de energía del implante, control de la frecuencia de estimulación y parámetros de configuración del funcionamiento del ASIC.3) System according to claim 1, characterized in that: the two-way communication between the portable external unit and the implant is carried out by means of a wireless connection by inductive coupling (19) between coil or coils (18) of the portable external unit and coil system (7) of the implant. And that said communication is synchronous using in both cases amplitude modulation of a carrier and whose coding is based on the use of two carrier amplitude levels. Synchronization is established by initiating the transmission of information from the implant when the portable external unit is using its minimum carrier amplitude level. In addition, the transmitter carrier of the portable outdoor unit is always of a higher frequency than the carrier used in the implant transmitter preventing the higher power signal corresponding to that of the transmitter of the portable external unit, interfering with the low transmission consumption from the implant (1) and to its reception in the portable outdoor unit (15). The data sent and received from the portable external unit correspond to the programming parameters of the current stimulation pulses, start and stop commands of said pulses, start or read the impedance measurement, read of the voltage induced in the implant energy reception coil, control of the stimulation frequency and configuration parameters of the ASIC operation.
4) Sistema según reivindicación 1 caracterizado porque el sistema de regulación del implante se utilizan convertidores de potencia DC/DC de tipo step-down en dispositivos implantables cuya tensión de entrada proviene directamente de un sistema de rectificación de la señal de radio frecuencia de la bobina o bobinas utilizadas para la recepción de energía en un implante.4) System according to claim 1 characterized in that the step-down type DC / DC power converters are used in the implant regulation system in implantable devices whose input voltage comes directly from a rectification system of the radio frequency signal of the coil or coils used to receive energy in an implant.
5) Sistema según reivindicación 1 caracterizado porque el sistema de regulación del implante se utilizan convertidores DC/DC de tipo step-down en donde la tensión de entrada provenga de cualquier otro regulador de tensión o cadena de reguladores de tensión de un implante en donde alguna de las tensiones de entrada provenga de la rectificación de la señal de radio frecuencia inducida por uno o varios acoplamientos inductivos entre la o las bobinas de un implante y una unidad extema de transmisión de una señal de radio frecuencia. 5) System according to claim 1 characterized in that the step-down type DC / DC converters are used in the implant regulation system wherein the input voltage comes from any other voltage regulator or tension regulator chain of an implant where some of the input voltages comes from the rectification of the radio frequency signal induced by one or several inductive couplings between the coil (s) of an implant and an external transmission unit of a radio frequency signal.
PCT/ES2001/000213 2000-05-26 2001-05-25 Sacral root stimulating system by means of a radio-frequency powered implant WO2001089629A1 (en)

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ESP200001343 2000-05-26
ES200001343A ES2164017B1 (en) 2000-05-26 2000-05-26 SACRAS ROOT STIMULATION SYSTEM THROUGH IMPLANT POWERED BY RADIO FREQUENCY.

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WO2016007912A1 (en) * 2014-07-10 2016-01-14 Perryman Laura Tyler Circuit for an implantable device

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WO1993024176A1 (en) * 1992-05-23 1993-12-09 Keith Edward Tippey Electrical stimulation for treatment of incontinence and other neuro-muscular disorders
ES2137946T3 (en) * 1991-03-11 2000-01-01 Univ Case Western Reserve DEVICE TO HELP THE MICTION.
WO2000015293A1 (en) * 1998-09-16 2000-03-23 Axon Engineering, Inc. Combined stimulation of ventral and dorsal sacral roots for control of bladder function
WO2000025859A1 (en) * 1998-10-30 2000-05-11 Aalborg University A method to control an overactive bladder

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US3650276A (en) * 1969-03-26 1972-03-21 Inst Demedicina Si Farmacie Method and apparatus, including a flexible electrode, for the electric neurostimulation of the neurogenic bladder
US3870051A (en) * 1972-04-27 1975-03-11 Nat Res Dev Urinary control
ES2137946T3 (en) * 1991-03-11 2000-01-01 Univ Case Western Reserve DEVICE TO HELP THE MICTION.
WO1993024176A1 (en) * 1992-05-23 1993-12-09 Keith Edward Tippey Electrical stimulation for treatment of incontinence and other neuro-muscular disorders
WO2000015293A1 (en) * 1998-09-16 2000-03-23 Axon Engineering, Inc. Combined stimulation of ventral and dorsal sacral roots for control of bladder function
WO2000025859A1 (en) * 1998-10-30 2000-05-11 Aalborg University A method to control an overactive bladder

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Publication number Priority date Publication date Assignee Title
WO2016007912A1 (en) * 2014-07-10 2016-01-14 Perryman Laura Tyler Circuit for an implantable device
US9522270B2 (en) 2014-07-10 2016-12-20 Micron Devices, LLC Circuit for an implantable device
US10493279B2 (en) 2014-07-10 2019-12-03 Stimwave Technologies Incorporated Circuit for an implantable device
US11426586B2 (en) 2014-07-10 2022-08-30 Stimwave Technologies Incorporated Circuit for an implantable device

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ES2164017B1 (en) 2004-06-01
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AU6235701A (en) 2001-12-03

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