Optimizing energy transmission in a leadless tissue stimulation system

The present invention generally relates to the optimization of sound energy transfer or ultrasonic energy transfer and the optimization of energy conversion, and more particularly, the optimization of sound energy transfer and the optimization of sound energy conversion in implantable devices. Related to energy conversion.

Stimulation of cardiac tissue using the Leadless cardiac stimulation system has been previously disclosed by Applicants. Generally, such a system includes one or more acoustic transducers and associated networks (referred to as controller transmitters), as well as an array of one or more implantable receiver stimulator devices. The controller transmitter produces and transmits sound energy, which is received by the receiver stimulator, which in turn converts the sound energy into electrical energy, which is then passed through the electrodes. Is communicated to the organization.

The control transmitter can be externally coupled to the patient's skin, but is usually implanted, the control transmitter has a reasonable size (similar to the size of an implantable pacemaker), and the control transmitter is a battery. It may be necessary to be able to operate for a very long period of time (typically 3 years or more) with. The small size and long operating period of the controller transmitter allows the system to generate sound energy from the controller transmitter with minimal loss or scattering of energy transmitted by the receiver stimulator and efficient conversion of energy by the receiver stimulator. Is required to be used efficiently.

Charich (Patent Document 1) describes various measures for locating an acoustic receiver. Charich describes how to charge a wireless device (receiver) from a controller transmitter, which is powered through a plug and supplies more than 1000W of power. In contrast, Leadless cardiac stimulation systems, where the power flow is on the order of six orders of magnitude less, require completely different methods and systems for locating receivers, which methods and systems , Not mentioned in Charich.

In short, in its simplest aspect, the receiver stimulator comprises one or more acoustic pressure electrical receiver elements, one or more rectifier circuits and electrodes. The piezoelectric receiver element connects the power from the acoustic field generated by the controller transmitter and converts it into electric power. Even if this AC power is applied directly to the tissue, it does not stimulate the tissue because its frequency is too high for excitement / stimulation. Rectifier circuits convert all or part of the available AC power into electrical pulses to initiate a paced heartbeat or provide other healing stimuli to the tissue. Electrical pulses are applied to the tissues of the heart via electrodes. The acoustic field is generated and transmitted by either an externally located control transmitter or an implantable control transmitter, which is remote from the receiver stimulator location.

The sound energy produced by the controller transmitter, commonly referred to as an acoustic beam or ultrasonic beam, is characterized by an acoustic intensity (I) measured in watts / square meter. In order to generate an acoustic intensity of Io over the area Ao, the controller transmitter must consume at least an amount of Io * Ao watts of power. Only part of this acoustic beam that intersects the receiver echosounder is available for power. If the area Ao is larger than the area of the cross section or the aperture of the receiver Ar, the ratio Ar / Ao represents the percentage of power available to the receiver stimulator in the acoustic beam. Therefore, the optimally efficient acoustic beam is very thin and only intersects the receiver elements of the receiver stimulator.

The controller transmitter has one or more piezoelectric transducers, which convert electric power into acoustic force that produces an acoustic beam directed at the receiver stimulator. The ability of the controller transmitter to generate this acoustic beam over a small area is characterized by its focal or directional gain. Generally, the larger the cross-sectional area (called the aperture) of the controller transmitter converter, the higher the directional gain. This requires that the controller transmitter have a wide aperture transmitter that concentrates the sound energy on the receiver stimulator. It also requires the controller transmitter to direct or direct the acoustic beam to the receiver stimulator. This can be achieved by using a phase-tuned array that uses beam forming techniques to direct the acoustic beam to the receiver stimulator. Directionalization can be achieved by adjusting the phase and amplitude of the electrically driven signal to the transducer array, which adjustment will adjust the direction and focal length of the transmitted beam.

If the location of the receiver stimulator or controller transmitter does not change over time, the controller transmitter can be configured at the time of the implant to optimally select a focused beam profile, which is the implant's. Aim at the location of the time-determined receiver stimulator. However, in the case of the Leadless system, the receiver stimulator can be expected to move due to heart movement, respiration or body orientation. Moreover, the controller transmitter can move slightly due to body orientation, body movement or body movement. Therefore, in order to adapt to the movements of the controller transmitter and receiver stimulators, we have recognized that successful actions in the simplest implementations may require relatively wide beam acoustic radiation. However, in this mode of operation, most of the transmitted sound energy may pass by the receiver stimulator and not be used efficiently. Therefore, we find that the transmitted beam needs to be significantly sharpened or focused to improve efficiency and that reliable operation is continuous in the location of the receiver stimulator. I further realized that it could require clear knowledge.

For the above reasons, it is desirable to provide a leadless system that efficiently transmits and receives sound energy. It is also desirable to adjust the transmitted beam to be as focused as possible by targeting the receiving element of the receiver stimulator. It is especially desirable if the location of the receiver stimulator is known to the controller transmitter so that the focused acoustic beam can be aimed and transmitted to the receiver stimulator. It is also desirable if the receiver stimulator is located using a mechanism that minimizes the size and complexity of the receiver stimulator so that no additional network or additional energy consumption is imposed on the receiver stimulator.

<p><patcit num="1"><text>U.S. Pat. No. 6,798,716</text></patcit></p>

<p num="0011"> Systems and methods are provided that efficiently transfer acoustic energy from an implanted or externally applied acoustic transmitter to an implanted acoustic receiver. Sound energy is converted into electrical energy by the receiver, which can be used for a variety of purposes. Electrical energy is typically transmitted to electrodes in contact with the tissue to stimulate the tissue in pacing the heart for, for example, bradycardia, termination of irregular tachycardia, or biventricular resynchronization therapy for heart failure. Be done. The systems and methods of the present invention also include applications for nerve stimulation, brain stimulation, voluntary muscle stimulation, stomach stimulation, bone growth stimulation, pain improvement, sensing and communication of local diagnostic information, and the like. It can be used for other purposes, where the acoustic transmitter must efficiently transfer energy to the implanted receiver. The implanted acoustic receiver can act as a tissue stimulator (receiver stimulator) or, more generally, as a sound energy transducer (receiver transducer). Efficient transmission can be achieved by locating the receiver and then transmitting a focused acoustic beam specifically aimed at the receiver, thereby improving the effective efficiency of the system. .. These systems and methods are particularly useful when the transmitter is an implantable device that relies on a limited source of energy, such as a battery.</p><p num="0012"> "Locator signal" means an acoustic signal for deriving a "location signal" transmitted by a transducer element in a controller transmitter assembly.</p><p num="0013"> "Location signal" means a signal that is passively or actively generated by a receiver stimulator. The location signal can respond to a "locator signal" transmitted by the controller transmitter, or the location signal can be transmitted periodically by the receiver stimulator. The location signal is used by the control transmitter to determine the location of the receiver with respect to the control transmitter, thus allowing the control transmitter to direct a focused and efficient acoustic beam to the receiver stimulator. To.</p><p num="0014"> One exemplary embodiment of the invention is a system that concentrates sound energy into the human body. The system receives an array of acoustic converters configured to transfer acoustic energy into the body, a network that concentrates the acoustic energy in specific areas within the body, and the acoustic energy. An acoustic receiver adapted to convert the acoustic energy into electrical energy, and a pair of electrodes connected to the acoustic receiver that are adapted to transfer the electrical energy to the body. The network is further configured to determine whether the acoustic energy is concentrated on the acoustic receiver by detecting the electrical energy transmitted through the body by the electrodes. .. The network may have one or more pairs of electrodes configured to determine if the sound energy is concentrated in the acoustic receiver. The network may also be configured to sequentially transmit the sound energy.</p><p num="0015"> Another exemplary embodiment of the invention described herein is a tissue stimulating system that includes an array of acoustic converters configured to transfer concentrated sound energy. The receiver stimulator comprises an implantable sound controller transmitter and one or more implantable sound receiver stimulators that receive the sound energy and are adapted to convert the sound energy into electrical energy. Further comprising electrodes configured to be in electrical contact with the tissue, the electrical energy is transmitted between the electrodes, and the controller transmitter transfers the concentrated sound energy to the controller transmitter. It is configured to determine the location of one or more of the receiver stimulators relative to the controller transmitter so that it can be directed to one or more of the receiver stimulators.</p><p num="0016"> Another embodiment of the invention is a method and system for determining the location of an acoustic receiver within a body. An array of acoustic transducers is used to transfer acoustic energy to specific locations within the body. The acoustic receiver is adapted to have an electrode, which produces an electrical location signal each time the electrode receives acoustic energy. A separate detection electrode may detect an electrical location signal that indicates when the array of acoustic transducers is concentrated on the acoustic receiver and reveals the location of the receiver. The transducer array may be configured to sequentially direct the sound energy until the location signal is detected or the preset time limit is reached. The transmitted sound energy can be a focused sound beam. The location signal can be detected by a sensing circuit on the controller transmitter.</p><p num="0017"> In another embodiment of the invention, the controller transmitter further tunes the transducer array to transfer concentrated sound energy to that region of the tissue associated with the detection of the location signal. Can be configured. This concentrated energy can be sufficient to stimulate tissues and especially heart tissue. In yet another embodiment, this concentrated energy can be generated based on the characteristics of the location signal.</p><p num="0018"> In yet another embodiment of the invention, the implantable sound controller transmitter comprises an adjustable converter array configured to transfer sound energy to the tissue, the implantable sound receiver transducer. A transducer assembly adapted to receive sound energy, including a transducer assembly adapted to convert the sound energy to electrical energy, the transmitter transmits a sound locator signal towards the receiver. The receiver is configured to generate a location signal. The location signal can be either electrical output or acoustic transmission in response to the locator signal. The locator signal can be focused sound energy. Alternatively, the concentrated sound energy transmitted by the transmitter can be converted into electrical energy by the receiver transducer and stored in the receiver transducer as electrical energy to be discharged at the appropriate time. The electrical energy can also be used to operate various networks such as control networks, diagnostic sensing networks, or communication networks.</p><p num="0019"> Another exemplary embodiment of the invention is a tissue stimulating system with an implantable sound controller transmitter having a sound converter array adapted to transfer sound energy to the tissue. A first implantable acoustic receiver stimulator that receives acoustic energy, including an acoustic receiver stimulator that converts the acoustic energy into electrical energy, the acoustic receiver stimulator being connected to the receiver stimulator. The first electrode assembly is adapted to be in electrical contact with the tissue, the receiver stimulator periodically transmits a location signal, and the controller transmitter is the controller transmitter. Detect location signals. The location signal can be electrical output or acoustic transmission that can be sensed by the controller transmitter. Based on the characteristics of the location signal, the transducer array can be tuned to transfer concentrated sound energy towards the receiver stimulator. Features of the location signal may include frequency, duration, amplitude, phase and flight time of the location signal. The present invention is also a method of optimizing the transfer of sound energy in a tissue between an implantable transducer transmitter and one or more implantable receiver stimulators, wherein the acoustic locator signal is transmitted to the controller. To transmit from the transmitter to the receiver stimulator, the controller transmitter includes an adjustable transducer array and, in response to reception of the locator signal, sends a location signal to the receiver stimulus. Includes producing from a vessel. The method may include detecting the location signal with the controller transmitter and adjusting the transducer array. The transducer array may transfer concentrated sound energy towards the receiver stimulator. In addition, the method is a centralized locator until the location signal of the receiver stimulator is detected by the controller transmitter or the preset time limit is reached. The transducer array is sequentially tuned to transmit the signal to the region of the tissue and the transducer array to transmit concentrated sound energy to the region associated with the detected location signal. It may include adjusting. The method may further include converting the sound energy with the receiver stimulator and applying the converted energy to the tissue. The energy can be large enough to stimulate the tissue. For example, the present invention provides the following items. (Item 1) A system that concentrates acoustic energy into a human body, in which an array of acoustic converters configured to transmit acoustic energy into the body and the inside of the body. With a network that concentrates the acoustic energy in a specific region of, an acoustic receiver that receives the acoustic energy and is adapted to convert the acoustic energy into electrical energy, and a pair of electrodes connected to the acoustic receiver. The acoustics include a pair of electrodes adapted to transfer the electrical energy to the body, by detecting the electrical energy transmitted through the body by the electrodes. A system further configured to determine if energy is concentrated on the acoustic receiver. (Item 2) A system that stimulates tissue, in which an implantable sound controller transmitter containing an array of sound converters configured to transmit concentrated sound energy and the sound energy are transferred. With one or more implantable sound receiver stimulators that receive and are adapted to convert the sound energy into electrical energy The receiver stimulator further comprises two electrodes configured to be in electrical contact with the tissue, the electrical energy being transferred between the two electrodes, and the controller transmitter. To determine the location of one or more of the receiver stimulators relative to the controller transmitter so that the controller transmitter can direct the concentrated sound energy to one or more of the receiver stimulators. The system consists of. (Item 3) A system that stimulates tissue, the system is an implantable acoustic controller transmitter containing an array of acoustic transducers configured to transfer acoustic energy to the tissue, and the acoustic energy. With one or more implantable acoustic receiver stimulators that receive and are adapted to convert the acoustic energy to electrical energy, and a first electrode assembly that is connected to the receiver stimulator to receive the electrical energy. The controller transmitter is configured to transmit an acoustic locator signal towards the receiver stimulator, including a first electrode assembly that is adapted to be in electrical contact with the tissue. A receiver stimulator is a system configured to generate a location signal in response to the locator signal. (Item 4) The controller transmitter is further configured to detect the location signal, and the converter array delivers the locator signal until the location signal is detected or the preset time limit is reached. The system according to item 3, wherein the acoustic beam is configured to sequentially direct the acoustic beam so as to transmit to the region of the tissue. (Item 5) The system according to item 4, wherein the converter array is configured to transmit the locator signal as a concentrated acoustic beam. (Item 6) The system of item 4, wherein the controller transmitter is further configured to tune the transducer array to transmit concentrated sound energy to the region of the tissue associated with the detection of the location signal. .. (Item 7) The system according to item 6, wherein the sound energy is sufficient to stimulate the tissue. (Item 8) The system according to item 7, wherein the tissue is a heart tissue. (Item 9) The system according to item 3, wherein the location signal is an electrical output applied to the first electrode assembly. (Item 10) The system of item 9, further comprising a sensing circuit and a second electrode assembly adapted to be in electrical contact with the body, wherein the location signal is detected by the sensing circuit. (Item 11) The system of item 10, wherein the sensing circuit and the second electrode assembly are located on the implantable controller transmitter. (Item 12) The system of item 10, wherein the sensing circuit is located on a separate implantable device. (Item 13) The system according to item 10, wherein the sensing circuit and the second electrode assembly are located on a device having the second electrode assembly that is in electrical contact with the outer surface of the body. (Item 14) The system according to item 10, wherein the sensing circuit is a spike detector circuit. (Item 15) The system of item 10, wherein the sensing circuit and the second electrode assembly include a spike detector assembly on the implantable controller transmitter. (Item 16) The system according to item 10, wherein the locator signal is a concentrated sound energy, and the detected electrical output indicates that the transducer array is concentrated on the receiver stimulator. (Item 17) Characterizing the electrical output detected by the spike detector assembly and providing sound energy to the receiver stimulator with one or more parameters including amplitude and polarity to determine the location of the receiver stimulator. 15. The system of item 15, comprising a network configured to perform the tuning of the converter array based on the parameters to be concentrated towards. (Item 18) The system of item 17, wherein optimal energy transfer is indicated by the electrical output above a predetermined threshold or detection within a predetermined time frame. (Item 19) The converter array is further sequentially adjusted to transmit concentrated sound energy as a locator signal toward a series of regions of the organization, and the above-mentioned one after any one of the transmissions. The system of item 18, wherein detection of the electrical output by the spike detector assembly indicates that the sound energy has been concentrated on the receiver stimulator. 20. The system of item 18, wherein the electrical output is less than the amplitude required to stimulate the tissue, which is the tissue of the heart. 21. The system of item 18, wherein the electrical output is sufficient to stimulate tissue, which is the tissue of the heart. (Item 22) A system that efficiently transmits sound energy, the system comprises an implantable sound controller transmitter including an acoustic transducer array configured to transmit sound energy to a tissue, and the sound. The controller transmitter includes an implantable acoustic receiver transducer that receives energy and is adapted to convert the sound energy to electrical energy so that the controller transmitter transmits a sound locator signal towards the receiver transducer. A system configured such that the receiver converter is configured to generate a location signal in response to the locator signal. (Item 23) 22. The system of item 22, wherein the transducer array is configured to transmit a wide beam acoustic locator signal. (Item 24) The converter array is configured to sequentially transmit a concentrated acoustic locator signal until the receiver transducer produces a location signal or reaches a preset time limit, item 22. Described system. (Item 25) The location signal is an electrical output, the electrical output being detected by a sensing circuit, the sensing circuit using an electrode assembly adapted to be in electrical contact with the tissue, item 22. Described system. 26. The system of item 22, wherein the receiver transducer is adapted to produce an acoustic output and the location signal is acoustic transmission. (Item 27) The concentrated sound energy is transmitted by the controller transmitter and converted into electrical energy by the receiver transducer, which is adapted to store the electrical energy. 24. (Item 28) The concentrated sound energy is transmitted by the controller transmitter and converted into electrical energy by the receiver converter, and the receiver converter converts the electrical energy into a control network and a diagnostic sensing network. 24. The system of item 24, adapted to be used to operate one or more of the and communication networks. 29. The system of item 28, wherein the receiver transducer is further adapted to convey sensed diagnostic data. (Item 30) A system that stimulates tissue, the system being implantable with an implantable sound controller transmitter containing a sound converter array adapted to transfer sound energy to the tissue and implantable to receive sound energy. A sound receiver stimulator that converts the sound energy into electrical energy. The acoustic receiver stimulator has a first electrode assembly connected to the receiver stimulator, the first electrode assembly is adapted to be in electrical contact with the tissue and the receiver. A system in which a stimulator periodically transmits a location signal and the controller transmitter detects the location signal. (Item 31) The location signal is an electrical output, which is detected by a sensing circuit, which uses a second electrode assembly adapted to be in electrical contact with the tissue. The system according to item 30. 32. The system of item 30, wherein the receiver stimulator is adapted to produce an acoustic output and the location signal is acoustic transmission. (Item 33) The transducer array uses an electrically driven signal to transmit concentrated sound energy towards the receiver stimulator based on the characteristics of the location signal detected by the controller transmitter. The system according to item 30, which is adjusted. (Item 34) The system of item 33, wherein the concentrated energy is at a level sufficient to stimulate the tissues of the heart. (Item 35) The electric drive signal to the converter array transmits the concentrated sound energy toward the receiver stimulator so that the frequency, duration, amplitude, phase, and flight time of the location signal are transmitted. 33. The system of item 33, which is adjusted based on one or more parameters including. (Item 36) A method of optimizing sound energy transfer in a tissue between an implantable transducer transmitter and one or more implantable receiver stimulators, wherein the acoustic locator signal is transmitted to the controller. To transmit from the transmitter to the receiver stimulator, the controller transmitter includes an adjustable transducer array and, in response to reception of the locator signal, sends a location signal to the receiver stimulus. Methods, including producing from a vessel. (Item 37) 36, further comprising detecting the location signal with the controller transmitter and adjusting the transducer array to transmit concentrated sound energy towards the receiver stimulator. the method of. (Item 38) The transformation to transmit the concentrated locator signal to the area of the tissue until the location signal of the receiver stimulator is detected by the controller transmitter or the preset time limit is reached. 36. The method of item 36, further comprising sequentially adjusting the transducer array and adjusting the transducer array to transfer concentrated sound energy to the region associated with the detected location signal. .. 39. The method of item 36, further comprising adjusting the transducer array to transmit a wide beam acoustic locator signal. (Item 40) The method according to item 36, wherein the location signal is an electrical output, and the electrical output is further detected using a sensing circuit. (Item 41) The method according to item 36, wherein the location signal is an acoustic output. (Item 42) Detecting the location signal using the controller transmitter, adjusting the converter array based on the location signal, and transmitting concentrated sound energy to the receiver stimulator. 36. The method of item 36, further comprising: (Item 43) The receiver stimulator is adapted to have a first electrode assembly, which is in electrical contact with the tissue and the receiver stimulator is used to convert the sound energy. 38. The method of item 38, further comprising applying the converted energy to the first electrode assembly. (Item 44) The method of item 43, further comprising stimulating the tissue. (Item 45) The method according to item 44, wherein the tissue is heart tissue. (Item 46) Characterizing the location signal with one or more features of the location signal, including frequency, duration, amplitude, phase, and time of flight, and including the receiver stimulator based on the location signal. , Determining the region of the tissue, adjusting the converter array towards the receiver stimulator based on the location signal, and effectively directing efficient sound energy towards the receiver stimulator. 37. The method of item 37, further comprising communicating with. 47. The system of item 1, wherein the network further comprises one or more pairs of electrodes configured to determine if the sound energy is concentrated in the acoustic receiver. (Item 48) The system according to item 47, wherein the network is further configured to sequentially transmit the acoustic energy. (Item 49) The controller transmitter is further configured to tune the transducer array to transfer concentrated sound energy to the region of the tissue associated with the detection of the location signal. The system described in. (Item 50) The system according to item 49, wherein the sound energy is sufficient to stimulate the tissue. (Item 51) The system according to item 50, wherein the tissue is the tissue of the heart. 47. The system of item 47, wherein the network is further configured to sequentially transmit the acoustic energy. (Item 49) The controller transmitter is further configured to tune the transducer array to transfer concentrated sound energy to the region of the tissue associated with the detection of the location signal. The system described in. (Item 50) The system according to item 49, wherein the sound energy is sufficient to stimulate the tissue. (Item 51) The system according to item 50, wherein the tissue is the tissue of the heart. 47. The system of item 47, wherein the network is further configured to sequentially transmit the acoustic energy. (Item 49) The controller transmitter is further configured to tune the transducer array to transfer concentrated sound energy to the region of the tissue associated with the detection of the location signal. The system described in. (Item 50) The system according to item 49, wherein the sound energy is sufficient to stimulate the tissue. (Item 51) The system according to item 50, wherein the tissue is the tissue of the heart.</p>

<figref num="1">FIG. 1 is a block diagram illustrating a tissue stimulation system.</figref><figref num="2A">2A-B illustrate one embodiment of the present invention.</figref><figref num="2B">2A-B illustrate one embodiment of the present invention.</figref><figref num="3">FIG. 3 illustrates an acoustic array that scans the area for a location signal in response to a locator signal.</figref><figref num="4">FIG. 4 shows the phases that are decomposed into different components.</figref><figref num="5A">5A-5C show various electrode configurations.</figref><figref num="5B">5A-5C show various electrode configurations.</figref><figref num="5C">5A-5C show various electrode configurations.</figref><figref num="6A">6A-6D show how to minimize scan time for target detection.</figref><figref num="6B">6A-6D show how to minimize scan time for target detection.</figref><figref num="6C">6A-6D show how to minimize scan time for target detection.</figref><figref num="6D">6A-6D show how to minimize scan time for target detection.</figref><figref num="7A">7A-7C illustrate embodiments that use frequency shift for optimizing acoustic beam directing and energy transfer.</figref><figref num="7B">7A-7C illustrate embodiments that use frequency shift for optimizing acoustic beam directing and energy transfer.</figref><figref num="7C">7A-7C illustrate embodiments that use frequency shift for optimizing acoustic beam directing and energy transfer.</figref>

Leadless's tissue stimulation system is shown in FIG. 1 as System 100. The implantable controller transmitter module 110 or the external controller transmitter module 110 produces acoustic waves 120 of sufficient amplitude, frequency, duration and duration so that the receiver stimulator module 150 electrically stimulates tissue. To do. The external programmer 170 wirelessly communicates with the implantable controller transmitter module 110, typically by radio frequency telemetry means 116, thereby adjusting operating parameters. The implantable controller transmitter module includes a telemetry receiver 115 that adjusts the characteristics of transmitted sound, a control network 140, a signal generator 117, a power amplifier 118, and an acoustic beam 120 transmitted to a receiver stimulator 150. Includes an output converter assembly 119 to generate. Unsurprisingly, the controller transmitter 110 transfers sound energy to the receiver stimulator 150 and to the leadless. The control network 140 is an electrical signal sensing circuit that is connected to one or more sensing electrodes 145 located on the outer case of the controller transmitter or is connected to the controller transmitter via a cable. Includes element 141. Alternatively, the electrical sensing circuit 141 can be a typical electrogram sensing circuit or an electrical spike detection circuit.

The receiver stimulator 150 includes a piezoelectric receiver converter 151, a rectifier network 153 and a tissue contact electrode 155. In this embodiment, the sound energy received and rectified by the receiver stimulator is applied directly to the electrode 155. Alternatively, the receiver stimulator module may include multiple transducer / rectifier channels in various combinations. The plurality of transducer / rectifier channels can be in series or parallel positions, or impedances, as previously disclosed in simultaneously pending application 11 / 315,524 (agent reference number 02834-0001010US). It can be a matching structure and / or for signal filtering, thereby improving the efficiency of the receiver transducer.

One embodiment of the present invention is shown in FIG. 2A as System 200. The controller transmitter module 210 is located either inside the body, remote from the myocardial tissue, or outside the body in contact with the surface of the body. The external programmer 170 communicates with the controller transmitter module, typically by radiofrequency telemetry 116. The telemetry module 115 inside the controller transmitter unit 210 provides bidirectional direct communication with the control network 220. The isolated continuous wave (CW) signal generator 217 inside the controller transmitter 210 provides the system with an acoustic operating frequency. Both the control network 220 and the signal generator 217 are connected to the respective channels of the two-dimensional acoustic converter array 260 (shown in FIG. 2B), where each channel is a transmit / receive transducer element 230ij, power. Includes amplifier 218ij and phase shifter module 240ij. The phase shifter module 240ij ensures that each channel transmits in the correct phase during echo transmission so as to form an efficient focused narrow acoustic beam intended to accurately intercept the receiver echosounder. Guarantee. The control signal from the control network 220 determines the transmission phase. The output of the phase shifter 240ij then transfers to the channel power amplifier 218ij, which is also under the control of the control network 220, and the power amplifier 218ij is in the OFF state, fully ON state, or beam shading. It can be any of the selected levels of intermediate power that may be required for. The output of the power amplifier is transferred directly to the channel converter element 230ij. One embodiment of using a phase shifter for each output channel has been described above. Other techniques such as direct formatting of the transmitted beam by the control network 220 may also be used.

The controller transmitter 210 can scan a spatial area by transmitting a thin acoustic beam (locator signal) and seeking a response (location signal) from the receiver stimulator. When a focused and directed acoustic beam intersects the receiver transmitter, the sound energy is converted by the receiver stimulator and output to the electrode 155 as an electrical output. This electrical output can generate an electrical signal, which can be detected by the sensing electrode 145 and the detection circuit 241 of the controller transmitter 210. If the controller transmitter does not detect an electrical signal within a reasonable time frame, it is possible that the directed acoustic beam does not intersect the receiver stimulator and the directed acoustic beam is "off target". Such a time frame can be predetermined or can be determined based on the characteristics of the location signal. The controller transmitter can then tune the focused directed beam to another part of the area, where the other part of the area is where the receiver stimulator can be located and selected near the previous area. The controller transmitter may repeatedly transmit the locator signal, thereby iteratively scanning the spatial area. In this method, electrical signals are generated and detected when the receiver stimulator is in a spatial area to be scanned. The controller transmitter then uses the parameters of the focused and directed beam as a target (transmission region) for the efficient transmission of the thin acoustic beam of acoustic energy to the receiver stimulator, and that parameter is detected. It becomes an electric signal (location signal) to be generated. Alternatively, the controller transmitter may then analyze the characteristics of the detected electrical signal to determine if the directed transmitter beam properly targeted the receiver stimulator.

The scanning process is shown in more detail in FIG. The phase array 260 of the controller transmitter consists of individual transducers 230ij. For convenience, the array is located in the xy plane at z = 0. The volume 305 of the space to be scanned contains all possible positions with respect to the receiver stimulator, and for convenience, the volume 305 of the space to be scanned is half the space relative to the phase array 260. Is located at z&gt; 0. The range of 305 is limited by structural limits and can vary depending on the particular stimulus application. The spatial volume 305 is divided into a plurality of volumes 302 kl, and the plurality of volumes 302 kl are individually scanned or tested. Volumes 302kl can overlap, but it is desirable that the entire set of volumes covers region 305. The array is aimed at the volume 302kl by setting the appropriate phase parameters for the array element 230ij.

The following method, provided as an example, can be used to determine the correct phase parameters for each of the array elements. Spatial location v1 is selected for volume 302 kl. The spatial location v1 is typically, but not necessarily, the center of the volume. Spatial location v2 is selected for array element 230ij. The spatial location v2 is typically, but not necessarily, the center of the array element. In general, v1 and v2 are 3D vectors having x, y and z components. The phase is

<maths num="1"></maths>Obtained by, there

<maths num="2"></maths>Is the standard Euclidean norm or distance function, mod is the modulo arithmetic operator, and λ is the wavelength of the acoustic wave. Alternatively, when aiming at the widest range of region 305, the phase parameters may not be calculated in modulo 2π, but rather in modulo n2π, where n is the wavelength across the elements of array 260. The maximum phase delay in units. This is somewhat more efficient and therefore preferred. This is because the first cycle of the transmitted array is targeted to the volume 302 kl, whereas the modulo 2π phase results in the first n cycles of the transmitted wave being out of focus.

Typically, the x-width and y-width of each volume 302 kl are selected as the narrowest possible acoustic beam width from the array 260. This minimum acoustic beam width w is

<maths num="3"></maths>Approximately, where λ is the wavelength of the acoustic wave, D is the horizontal magnitude of the array 260, and r is the range or distance along the z-axis from the array 260 to the volume 302 kl. Therefore, if the array 260 is rectangular, i.e., the horizontal widths for the x and y dimensions are different, then the minimum beamwidths are different and therefore the x and y dimensions of the volume 302kl are different. It should also be noted that the volume 302 kl is generally wedge-shaped and expands in the horizontal dimension with increasing range r, as the minimum acoustic beamwidth increases with range r. The acoustic beam itself tapers from the central peak rather than abruptly, and therefore it is desirable for the volume 302 kl to have some overlap (eg, 50% overlap). This provides relatively accurate targeting of the receiver stimulator and therefore relatively efficient transfer of acoustic energy.

The maximum horizontal width W of the communication area 305 is

<maths num="4"></maths>Approximately, where λ is the wavelength of the acoustic wave, d is the horizontal magnitude of the individual array elements 230i, and r is the range or distance along the z-axis from the array 260 to the volume 302 kl. .. Similar to the individual volumes 302 kl, the entire scan area 305 has a wedge shape that extends outward in the horizontal dimension as the range r increases.

If the 305 extends over the fur field of the array 260, no depth concentration or z concentration is required and each volume 320 kl can extend over the entire z depth of region 305. However, if the 305 overlaps the near-field transfer region of the phase array 260, multiple layers such as volumes 302 lk, 303 kl, etc. must also be scanned for the z dimension. In general, the boundary between the near-field area and the far-field area is

<maths num="5"></maths>Given by.

Of course, z-dimensional scans may not be required in situations where the expected target location area is in the far field, or where the expected target location area moves only within a fixed focal zone.

Another method of quickly and efficiently determining the required phase for the elements of the transmission array in the controller transmitter is described below. As mentioned earlier, the required phase can be calculated. However, this is computationally expensive and consumes valuable energy and valuable time. In particular, it requires the calculation of the square root. An alternative is to pre-calculate the required phase for each element 230ij of the array 260 for each scan location 302kl. This is a quick but significant amount of memory needed. There is an additional time burden required to read the phases from memory and load them into the phase shifter 240ij for each of the array elements 230ij. This time can be reduced by increasing the clock speed of the digital electronics in the controller transmitter or by parallelizing the loading process.

FIG. 4 describes how the required phase can be subdivided into three separate components. The first two are the phase slopes in the x and y directions. These are linear functions of the x and y locations of the array elements, so they are relatively inexpensive to calculate.

If the receiver stimulator is very far from the controller transmitter, only these first two phase components are needed. However, a third component, shown as a pre-phase adjustment component, is required when the receiver stimulator is around the boundary region of the furfield of the array, and whenever the receiver stimulator is in the nearfield. Needed. This pre-phase adjustment component is not a linear function of the position of the transfer element in the array and is therefore relatively costly to calculate.

The basic method is to rarely calculate the pre-phase adjustment component and to calculate the phase linear component whenever the array needs to be oriented to a new location. There are several options for determining the phase adjustment component in advance. The first is the expected range (distance) between the controller transmitter and the receiver stimulator, which is the phase (straight perpendicular, angle) required to direct to the central target. ), The phase adjustment is calculated in advance. This can be done using the formula shown above (Formula 1). Pre-phase adjustment compensates for the fact that the receiver stimulator is not exactly present in Farfield. That fact is true only if the receiver stimulator is infinitely far from the controller transmitter. When the receiver stimulator is in the farfield, the pre-phase adjustment component is simply zero, i.e. all elements of the array transmit in the same phase. These pre-phases can be calculated, stored in read-only memory (ROM) and downloaded as part of the control transmitter manufacturing, or determined once when the control transmitter is implanted. .. The latter method has the advantage of relatively accurate knowledge of the range between the controller transmitter and receiver stimulator.

The linear phase slope can be calculated by the control network and then downloaded to each of the phase controllers 241ij, or the phase controller is linear using either a look-up table or a dedicated computer network. Can determine the phase component of.

Another alternative is to calculate the pre-phase adjustment based on the nominal location of the receiver stimulator (ie, not only the range but also the angular location). This works well when the receiver stimulator is placed at a significant angle from the perpendicular to the controller transmitter. In the absence of significant movement of the receiver stimulator relative to the controller transmitter, the pre-phase adjustment component only needs to be calculated once, eliminating significant computational overhead.

The electrical output generated through the electrode 155 as part of the scanning process can be considered a stimulating or pacing output if the output contains sufficient energy to excite the tissue in the vicinity of the electrode 155. However, the tissue is stimulated and it is not necessary to detect the electrical signal at the electrode 145. In practice, the electrical output is irritating because the energy required to generate the electrical output detectable by the electrodes 145 and the detection circuit 241 is significantly lower than the energy required to stimulate the tissue. It is advantageous that it is not a pulse. This lower energy need is primarily achieved by shortening the duration of the locator signal, resulting in a significantly lower electrical output of the electrode 155 than the value used to stimulate the tissue. For example, the duration of a signal to cardiac tissue stimulation ranges from 200 μs to 2000 μs, while typical duration ranges from 400 μs to 500 μs. The minimum lifetime of a locator signal is the various parameters (system operating frequency, Q and transmission array size of both transmitter and receiver converters, and the overall receiver if the receiver contains multiple converters. Structure) is affected. The minimum time of 10 cycles is a reasonable estimate. It sets the minimum locator signal lifetime in 10 to 20 μs (at least 20 times less than typical lifetime for tissue stimulation) for ultrasonic systems operating in the frequency range of 500 kHz to 1 MHz. To do. This makes this embodiment attractive by reducing the energy used to transmit the locator signal by at least one twentieth of the energy used to stimulate the tissue.

The short-lived locator signal requires a different detection circuit 241 as compared to the detection circuit used for conventional ECG processing or, moreover, the detection circuit used for pacing spike detection. ECG signals are typically processed with an amplifier bandwidth of 0.5 Hz to 100 Hz. The pacing spike detector typically has a bandwidth of 1 kHz to 2.5 kHz. A 10-20 μs electrical signal generated in response to a 10-20 μs locator signal requires a bandwidth of up to 100 kHz.

It is common to observe signal attenuation of 65-80 dB for pacing signals generated from inside the heart and sensed on surface ECG electrodes, both in animal models and in humans. Shown by the survey. Therefore, a 1 volt electrical pulse transmitted across the electrode 155 can be a signal from 560 microvolts to 100 microvolts on the electrode 145. State-of-the-art amplifiers have a noise figure of 20 nV / (Hertz).^１／２The noise can be achieved in the range of 6 microvolts over the 100 kHz bandwidth, and the signal-to-noise ratio is very reasonable for the detection of location signals. However, such a high bandwidth and high gain amplifier consumes more power than a conventional ECG amplifier, and a conventional ECG amplifier amplifies a high amplitude signal with a low bandwidth. Therefore, it is advantageous to simply operate these amplifiers when needed (ie, shortly after the transmission of the acoustic locator signal).

Furthermore, it is important to note that location signals are generated and sensed from two electrodes that are spatially close to each other. The positions of both the receiver stimulator electrode 155 and the controller transmitter electrode 145 are limited by practical limits. Therefore, the electrical signal generated by the electrode 155 has a dipole radiation pattern, and the sensitivity of the electrode 145 also has a dipole pattern. FIG. 5a shows a typical dipole arrangement. The sensing electrode 145 is input to the differential amplifier 410. The dashed line 401 indicates the region "blind spot", where the signal source cannot be sensed by the electrode 145. This is because the signal sources located along this line are equidistant to both electrodes 145 and the differential amplifier subtracts these two equal signals to produce a zero output. Correspondingly, the dashed line 402 indicates the region where the signal source is sensed with the maximum output from the amplifier 410. Similar behavior occurs as a result of the transmission of electrical signals through the electrodes 155. Therefore, the overall attenuation is the result of the superposition of the two dipole patterns. It is therefore advantageous to use more than two electrodes 145 on the controller transmitter to avoid potential "blind spots" in these dipole patterns. FIG. 5b shows how the addition of a third electrode eliminates this "blind spot" problem. The two amplifiers 420a and 420b are used to amplify the signals from two separate dipoles directed 90 degrees apart. The two signal outputs, 242a of 420a and 242b of 420b, are then analyzed for the presence of a location signal, respectively. Even relatively significant improvements can be brought about by the addition of more electrodes, which are spatially separated from the first three electrodes, as shown in FIG. 5c. This has the added benefit of avoiding any "blind spots" in the dipole pattern produced by the electrode 155 in the receiver stimulator. Have. One electrode 146 is selected as a reference, all other electrodes 145 are amplified relative to this reference using an amplifier 410i, and each amplifier 410i produces a signal 420i. The dipole signal 244 from any pair of electrodes can then be calculated using 243 to take the difference between two of the output signals 420i, and 243 can be implemented as a hardware differential amplifier or It can be implemented in software as a subtraction of two digitized signals. As mentioned above, the amplifier 410i is necessarily a high gain amplifier with high bandwidth and therefore consumes significant power. Therefore, it is advantageous to use only the amplifier that provides the location signal with the largest amplitude. Receiver and Controller Assuming that the operation of the transmitter significantly changes the amplitude of the location signal, once the electrode pair that produces the largest location signal is determined, the amplifier used to generate this signal. Only need to be used, significantly reducing power consumption.

An important consideration is the time spent in determining the location of the receiver stimulator. Obviously, this time should be as short as possible. If this time is comparable to the cycle of the heart, the movement of the heart between the determination of the location and the subsequent transfer of stimulating energy is problematic. It is also advantageous to minimize the scan time required when a leadless stimulator is used with a standard pacemaker to achieve healing biventricular pacing. In this case, as disclosed in pending application 11 / 315,023 (agent reference number 021834-000820US), the controller transmitter is a right ventricular (RV) pacing artifact in the accompanying implanted device. Immediately after the detection of, the sound energy is transmitted, thereby stimulating the heart. Preferably, the receiver stimulator positioning is performed after the detection of the RV pacing artifact, minimizing the effect of cardiac movement between the positioning and the stimulus.

FIG. 6 shows several ways to minimize the scan time required. FIG. 6a shows partitions of space that are scanned into different target areas. This partition assumes that there is no depth target and therefore the scan space is in the xy plane at a fixed z location. The method can be easily extended to the case of depth targets. In soft tissue and in blood, the velocity of sound is about 1.5 mm / μsec. Considering the large distance between the controller transmitter and receiver stimulator of 200 mm, the maximum flight time is about 133 μsec. FIG. 6b shows a simple scanning method in which the time P between locator signals is selected to be longer than the expected flight time. The method of processing the output signal 244 is described as follows. Detection of the location signal 510 following the locator signal 505 indicates that the receiver stimulator is included in the volume corresponding to the locator signal 505 (volume 15 in FIG. 6a). In addition, the time of flight proportional to the range between the controller transmitter and receiver stimulator can be measured by the time delay between the transmission of the locator signal and the detection of the location signal.

FIG. 6c illustrates a relatively fast scanning method. In this case, the time P between the transmitted pulses (locator signals) is shorter than the actual flight time, the duration of each individual locator signal, and the setup that the controller transmitter prepares for the next locator signal. Limited by time only. This results in multiple locator signals flying between the controller transmitter and receiver stimulator at the same time, significantly reducing scan time. Once the location signal is detected, determining the actual locator signal that produced the location signal, as shown in Figure 6c, requires knowledge of the nominal time of flight between the controller transmitter and receiver stimulator. .. This optimized method is applicable if the previous location is known and therefore the time of flight to the receiver stimulator is known and only small movements of the receiver stimulator are expected relative to the controller transmitter. .. The time P between locator signals can be set to the maximum expected range of motion. For example, if the maximum expected movement is 40 mm, then P should be at least 40 / 1.5 or 27 μsec.

Hybrid techniques such as those shown in FIG. 6d can be used when the location of the receiver stimulator is not known at all during the initial operation and therefore the nominal time of flight is not known at all. A rapid scan of the entire area is performed using a technique similar to that shown in FIG. 6c until a location signal is detected. Once the location signal is detected, a relatively slow scan similar to the technique shown in FIG. 6b is performed on a volume near the detected location signal (starting at volume 13, then volume 14, etc.). .. This accurately aims at the correct volume (15 in this case) and allows the back calculation of the actual time of flight.

In some cases, a time between locator signals that is longer than the time between locator signals used in FIG. 6b may be required. This can happen if there is sufficient sound energy from the locator signals, the locator signals are reflected by the anatomical structures in the body, and the receiver stimulator responds to these reflected locator signals. This is generally addressed by increasing the time between locator signals so that any reverberations or reflections from the previous locator signal are attenuated before transmitting another locator signal. However, the likelihood of this problem occurring can be substantially reduced by prior knowledge of the nominal time of flight. This allows the controller transmitter to look for location signals in a narrow time window, eliminating false detections due to reflected locator signals.

Another way to minimize the scan time and the energy spent on the scan itself is to perform an intelligent search. One approach is to initiate the scan by transmitting a locator signal to a previously known location for the receiver stimulator. Therefore, if the receiver stimulator does not move out of the scan volume, only one locator signal is needed. If more scans are needed, another strategy is to extend the search out of the most up-to-date position known for the receiver stimulator. Another approach is to memorize a previous history of receiver stimulator movement and use it to intelligently scan against it. This greatly reduces the number of scans whenever the main movement of the receiver stimulator is periodic (eg, mainly due to heart movements and respiratory movements).

Note that more than one receiver stimulator can be implanted and operated using a different approach to optimizing energy transfer as described above. The location of each receiver stimulator relative to other receiver stimulators can be registered throughout the time of the implant. After the implant, when the receiver stimulators move due to heart movements, breathing, etc., they will move together with each other. However, the relative location of the receiver stimulator to the controller transmitter, which affects optimal energy transfer by the controller transmitter, will change due to heart movement, respiration, and so on. To address this issue, if the location of the first receiver stimulator is identified using one of the approaches described above, then relative to the other receiver stimulators registered between the implants. The location of other receiver stimulators is calculated immediately based on the location.

Alternatively, each receiver stimulator (when multiple receiver stimulators are implanted) can be "addressed" using a locator signal with a unique frequency or unique phase. The approach described above can then be applied sequentially to each receiver stimulator, thereby optimizing energy transfer from the controller transmitter. That is, more simply, to the fact that if multiple receiver stimulators are implanted with sufficient difference in location, the knowledge of the previous location and the relative location between the devices will not change significantly. Based on this, each can be directly located by the method described above.

Although the location signal is detailed as an electrical signal, it should be understood that the location signal can have any kind of property that can be detected by the controller transmitter. For example, it can be a passive echo from the device, or it can be adapted for the receiver to carry an acoustic signal in response to the locator signal.

Another embodiment of the invention described herein for optimizing energy transfer from a controller transmitter is described in FIGS. 7A-7C. In FIG. 7A, one element of the controller transmitter array ("CT array") transmits a wide beam acoustic burst (locator signal), which is transmitted by a receiver stimulator ("RS"). Received. While the signal is received at the receiver stimulator, the signal is frequency-shifted and isotropically retransmitted back to the controller transmitter, as depicted in FIG. 7B. This retransmission occurs while the locator signal is received by the receiver stimulator. The location of the receiver stimulator for each element of the CT array is recorded in the memory of the controller transmitter as a detected phase received for each channel. The controller transmitter then uses the recorded phase measurements to transfer acoustic energy as a focused beam to the receiver stimulator and to the electrodes for tissue stimulation, as shown in FIG. 7C. , Communicate at a clinically appropriate time.

The amount of energy contained in the locator signal generated from a single element in the phase measurement mode described above can be substantially greater than the amount of energy used for the stimulus. However, now that the correct phase measurements have been obtained, the entire array stimulates significantly less energy than could be required to achieve the same level of energy transmitted to the tissue using the wide beam. Is transmitted for. Here, each element of the array can transmit a fairly efficient focused beam as compared to a wide beam that each element of the array can transmit in the absence of the correct phase measurements. Moreover, by the method described above, phase measurements were obtained without further calculation. In this way, energy consumption is further minimized.

Not all array elements need to be driven with the same amplitude when generating a focused beam used for stimulation. If one path or all other paths from the receiver stimulator to the array of elements show either relatively high attenuation or relatively low attenuation, this is either relatively high energy or relatively low energy, respectively. It can be overcome by either transmitting with relatively little energy or by stopping the extremely affected array elements. In addition, aperture shading (relatively low amplitude emission from the edges of the array) has the effect of flattening the acoustic beam for relatively good uniformity within the acoustic beam, which is common in the technical field of array design. Are known. This can also be accomplished guided by pre-programmed calculations in the controller transmitter.

Further aspects of the invention are described below. In one embodiment where no locator signal is required, the receiver stimulator first receives the sound energy from the controller transmitter, stores some of the received energy, and directs the rest to the tissue. The stored energy can be somewhere from 0 to 100% of the received energy, ideally about 5% of the received energy. However, based on a variable timeout, fixed timeout, or periodic timeout inside the receiver stimulator, the stored energy prior to the next transfer of sound energy from the control transmitter is the receiver stimulus. Used by the instrument to generate a location signal. The location signal can be an electrical signal, or the location signal is an acoustic responder signal transmitted to the controller transmitter, or a similar generated by the receiver stimulator as a homing beacon that signals the location of the receiver stimulator. It can be a signal. The controller transmitter receives a location signal and calculates the location of the receiver stimulator from the location signal using information such as amplitude, phase or arrival time. By identifying the location of the receiver stimulator, the control transmitter can then focus the transmitted acoustic beam on the location or region of the receiver stimulator, thereby optimally transmitting energy or Or exchange communications optimally.

Alternatively, the controller transmitter transmits the locator signal to the passive receiver stimulator in the form of sufficient sound energy, which uses all the energy received to generate the location signal. .. In this embodiment, the receiver stimulator can be adapted to have a state machine, which uses sound energy for the location signal and for practical purposes such as stimulation. Switch to using. The location signal is received by the controller transmitter, which determines the location of the receiver stimulator based on the characteristics of the signal contained in the location signal, and then the concentration targeted to the location or area of the receiver stimulator. Generate a beam.

It should be noted that, as shown above, the acoustic receiver of the present invention can act as a receiver stimulator or transmitter transducer, where the receiver transducer can act as a diagnostic tool. Examples describe receiver stimulator embodiments, but the energy optimization techniques described above can be applied to receiver transducers as well.

The above is a complete description of preferred embodiments of the invention, but various alternatives, various modifications and various equivalents can be used. Therefore, the above description should not be taken as limiting the scope of the invention, the invention is defined by the appended claims.