Patent Publication Number: US-2022212018-A1

Title: Temperature sensing of implanted wireless recharge coil

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     n/a. 
     FIELD 
     The present technology is generally related to a system for measuring temperature in a transcutaneous energy transfer system (TETS). 
     BACKGROUND 
     Many implantable medical devices have significant energy requirements. A transcutaneous energy transfer system (“TETS”) may be used to power implantable devices including artificial hearts, defibrillators, and electrical systems. Generally, a TETS can transfer energy from an external transmission coil to a receiving coil that is implanted under the skin. A TETS may be used to supplement, replace, or charge an implanted power source such as a rechargeable battery. Using a TETS to power these vital implantable devices can significantly lessen the potential of infection as the TETS does not require constant puncturing of the skin and/or wires that pass through the skin. Also, a patient may have increased mobility with the implantable device as power may be transmitted over a range of skin thicknesses. 
     Proper alignment of the external transmission coil and the implanted receiving coil is critical to transfer energy from the external transmission coil to the receiving coil through an area of the skin that separates the two coils. If sufficient alignment is not maintained between these two coils, interrupted operation of the implanted medical device may occur. Patient movement may cause the position of the external transmission coil and the receiving coil to shift and not be properly positioned to allow for the desired or required transfer of energy to power the implantable device and/or recharge an implantable battery. Misalignment between the external transmission coil and the receiving coil may further result in undesirable heating of the receiving coil. 
     SUMMARY 
     The techniques of this disclosure generally relate to implantable blood pumps, and in particular, measuring temperature during power transfer. 
     In one aspect, the present disclosure provides a transcutaneous energy transfer system (TETS) having an implantable receiving coil in communication with an implantable controller and a hermetically sealed package encased by the implantable receiving coil. The hermetically sealed package including a plurality of tuning capacitors and at least one temperature sensor. The at least one temperature sensor being configured to measure a temperature of the hermetically sealed package. The hermetically sealed package further including scavenging circuitry configured to scavenge power from the plurality of tuning capacitors and a temperature measuring circuit in communication with the at least one temperature sensor and the scavenging circuitry. The temperature measuring circuit being configured to transmit the measured temperature to the implantable controller. 
     In another aspect of this embodiment, the implantable receiving coil is configured for transcutaneous inductive communication with an external transmission coil. 
     In another aspect of this embodiment, the measured temperature of the hermetically sealed package is indicative of a degree of alignment between the hermetically sealed package and the external transmission coil. 
     In another aspect of this embodiment, one selected from the group consisting of at least one connector and at least one cable extends from the implantable receiving coil to the implantable controller. 
     In another aspect of this embodiment, the measured temperature is transmitted on an RF modulated carrier signal through the one selected from the group consisting of the at least one connector and the at least one cable. 
     In another aspect of this embodiment, a frequency of the RF modulated carrier signal is higher than a power transfer frequency between the implantable receiving coil and the external transmission coil. 
     In another aspect of this embodiment, an external controller in communication with the external transmission coil, the implantable controller being configured to perform at least one operation selected from the group consisting of: reduce battery charging, disable battery charging, and transmit an alert to the external controller, when the measured temperature of the hermetically sealed package exceeds a predetermined threshold temperature. 
     In another aspect of this embodiment, the predetermined threshold temperature is a temperature between 43° C. and 65° C. 
     In another aspect of this embodiment, the alert is at least one selected from the group consisting of an audible alert notification, a visual alert notification, and a tactile alert notification to correct the degree of alignment between the implantable receiving coil and the external transmission coil. 
     In another aspect of this embodiment, the hermetically sealed package is composed of at least one selected from the group consisting of titanium, glass, sapphire and ceramic materials. 
     In another aspect of this embodiment, the alert is transmitted from the implantable controller to the external controller via a Bluetooth signal. 
     In one aspect, a transcutaneous energy transfer system (TETS), comprises an external transmission coil in communication with an external controller and an implantable receiving coil in communication with an implantable controller. The implantable receiving coil being configured for transcutaneous inductive communication with the external transmission coil and the implantable controller being configured to receive power from the implantable receiving coil. The TETS further including a hermetically sealed package encased by the implantable receiving coil. The hermetically sealed package including a plurality of tuning capacitors and at least one temperature sensor. The at least one temperature sensor being configured to measure a temperature of the hermetically sealed package. The hermetically sealed package further including scavenging circuitry configured to scavenge power from the plurality of tuning capacitors and a temperature measuring circuit in communication with the at least one temperature sensor and the scavenging circuitry. The temperature measuring circuit being configured to transmit the measured temperature to the implantable controller. 
     In another aspect of this embodiment, the measured temperature of the hermetically sealed package is indicative of a degree of alignment between the hermetically sealed package and the external transmission coil. 
     In another aspect of this embodiment, one selected from the group consisting of at least one connector and at least one cable extends from the implantable receiving coil to the implantable controller. 
     In another aspect of this embodiment, the measured temperature is transmitted on an RF modulated carrier signal through the one selected from the group consisting of the at least one connector and the at least one cable. 
     In another aspect of this embodiment, the implantable controller is configured to perform at least one operation selected from the group consisting of: reduce battery charging, disable battery charging, and transmit an alert to the external controller, when the measured temperature of the hermetically sealed package exceeds a predetermined threshold temperature. 
     In another aspect of this embodiment, the predetermined threshold temperature is a temperature between 43° C. and 65° C. 
     In another aspect of this embodiment, the alert is at least one selected from the group consisting of an audible alert notification, a visual alert notification, and a tactile alert notification to correct the degree of alignment between the implanted receiving coil and the external transmission coil. 
     In another aspect of this embodiment, a frequency of the RF modulated carrier signal is higher than a power transfer frequency between the implantable receiving coil and the external transmission coil. 
     In one aspect, a transcutaneous energy transfer system (TETS) includes an external transmission coil in communication with an external controller, an implantable receiving coil in communication with an implantable controller, and a hermetically sealed package encased by the implantable receiving coil. The implantable receiving coil being configured for transcutaneous inductive communication with the external transmission coil and the implantable controller being configured to receive power from the implantable receiving coil. The hermetically sealed package being composed of at least one selected from the group consisting of glass, titanium, sapphire, and ceramic materials. The hermetically sealed package including a plurality of tuning capacitors, scavenging circuitry, a temperature measuring circuit, and at least one temperature sensor being configured to measure a temperature of the hermetically sealed package. The measured temperature of the hermetically sealed package being indicative of a degree of alignment between the implantable receiving coil and the external transmission coil. The scavenging circuitry being configured to scavenge power from the plurality of tuning capacitors. The temperature measuring circuit being in communication with the at least one temperature sensor and the scavenging circuitry. The temperature measuring circuit being configured to transmit the measured temperature to the implanted controller on an RF modulated carrier signal through one selected from the group consisting of at least one connector and at least one cable. The RF modulated carrier signal having at least one frequency band selected from the group consisting of ISM frequency bands and MICS frequency bands. The selected at least one frequency band being higher than a power transfer frequency between the implantable receiving coil and the external transmission coil. The implantable controller being further configured to perform at least one operation selected from the group consisting of: reduce battery charging, disable battery charging, and transmit an alert to the external controller, when the measured temperature of the hermetically sealed package exceeds a predetermined threshold temperature between 43° C. and 65° C. The alert being at least one selected from the group consisting of an audible alert notification, a visual alert notification, and a tactile alert notification to correct the degree of alignment between the implanted receiving coil and the external transmission coil. 
     The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
         FIG. 1  is an internal system view of an implantable blood pump with a TETS receiver source constructed in accordance with the principles of the present application; 
         FIG. 2  is an external view of a TETS transmitter, and a controller of the system shown in  FIG. 1 ; 
         FIG. 3  is a perspective view of an implantable receiving coil of the system as show in  FIGS. 1 and 2 ; and 
         FIG. 4  is a top view of a silicone housing that encompasses the implantable receiving coil of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a medical device. 
     In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include non-transitory computer-readable media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer). 
     Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” as used herein may refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements. 
     Referring now to the drawings in which like reference designators refer to like elements there is shown in  FIGS. 1 and 2  an exemplary transcutaneous energy transfer system (“TETS”) constructed in accordance with the principles of the present application and designated generally as “10.” The TETS  10  may be fully implantable within a patient, whether human or animal, which is to say there are no percutaneous connections between the implanted components of the TETS  10  and the components outside of the body of the patient. In the configuration shown in  FIG. 1 , the TETS  10  includes an implantable controller  12  implanted within the body of the patient. The implantable controller  12  includes a control circuit having processing circuitry configured to control operation of an implantable blood pump  14 . The implantable controller  12  may include an internal power source  16 , configured to power the components of the implantable controller  12  and provide power to one or more implantable medical devices, for example, the implantable blood pump, such as a ventricular assist device (“VAD”)  14  implanted within the left ventricle of the patient&#39;s heart. The power source  16  may include a variety of different types of power sources including an implantable battery. VADs  14  may include centrifugal pumps, axial pumps, or other kinds electromagnetic pumps configured to pump blood from the heart to blood vessels to circulate around the body. One such centrifugal pump is the HVAD and is shown and described in U.S. Pat. No. 7,997,854, the entirety of which is incorporated by reference. One such axial pump is the MVAD and is shown and described in U.S. Pat. No. 8,419,609, the entirety of which is incorporated herein by reference. In an exemplary configuration, the VAD  14  is electrically coupled to the implantable controller  12  by one or more implanted conductors  18  configured to provide power to the VAD  14 , relay one or more measured feedback signals from the VAD  14 , and/or provide operating instructions to the VAD  14 . 
     Continuing to refer to  FIG. 1 , an implantable receiving coil  20  may be coupled to the implantable controller  12  by, for example, at least one connector and/or cable  22 . In an exemplary configuration, the receiving coil  20  may be implanted subcutaneously proximate the thoracic cavity, although any subcutaneous position may be utilized for implanting the receiving coil  20 . The receiving coil  20  is configured to be inductively powered through the patient&#39;s skin by an external transmission coil  24  (seen in  FIG. 2 ) disposed opposite the receiving coil  20  on the outside/exterior of the patient&#39;s body. As shown in  FIG. 2 , the transmission coil  24  may be coupled to an external controller  26  having a power source  28  such as, for example, a portable battery carried by the patient or wall power. In one configuration, the battery is configured to generate a radiofrequency signal for transmission of energy from the transmission coil  24  to the receiving coil  20 . The receiving coil  20  may be configured for transcutaneous inductive communication with the transmission coil  24 . 
     Referring now to  FIG. 3 , the implantable receiving coil  20  is shown. The receiving coil  20  includes a hermetically sealed package  30  encased by an exterior surface  32  of the receiving coil  20 . The hermetically sealed package  30  includes a plurality of tuning capacitors  34 , at least one temperature sensor  36 , and a temperature measuring circuit  40 , disposed on a circuit board  38 . The receiving coil  20  further includes a transient voltage suppression (TVS) diode (not shown) disposed within the hermetically sealed package  30  to protect the implantable receiving coil  20  from spikes in voltage that may occur during the power transfer phase. The at least one temperature sensor  36  is configured to measure the temperature of the hermetically sealed package  30  during a power transfer phase between the transmission coil  24  and the receiving coil  20  wherein the internal power source  16  is charged. 
     As a non-limiting example, the hermetically sealed package  30  may be composed of glass, ceramic materials, titanium, sapphire, or any other type of metal with conductive properties that would protect the components contained within the hermetically sealed package  30  from corrosion. Excess heating of the hermetically sealed package  30  may result from a misalignment between the receiving coil  20  and transmission coil  24  during charging of the internal power source  16 . Increased eddy current heating may also affect the temperature of the receiving coil&#39;s  20  silicone housing  42  (as shown in  FIG. 4 ) which can lead to discomfort or harm to the patient. To protect the patient from discomfort or harm, the at least one temperature sensor  36  continuously and/or periodically measures the temperature of the hermetically sealed package  30 . 
     Continuing to refer to  FIG. 3 , the receiving coil  20  further includes scavenging circuitry  44  encased within the hermetically sealed package  30 . The scavenging circuitry  44  and the temperature measuring circuit  40  are in communication with the at least one temperature sensor  36  and the plurality of tuning capacitors  34 . The scavenging circuitry  44  scavenges power from the AC voltage present across the plurality of tuning capacitors  34  and converts the AC voltage to DC voltage in order to power the temperature measuring circuit  40  and Radio Frequency (RF) modulating circuitry (not shown). Once powered, the temperature measuring circuit  40  then transmits the measured temperature to the implantable controller  12  via a radio antenna, transducer, transmitter, receiver, transceiver  46 , or the like by modulating the data on an RF modulated carrier signal via the RF modulating frequency and coupling the carrier signal to the at least one connector and/or cable  22  extending between the receiving coil  20  and the implantable controller  12 . The carrier frequency of the RF modulated carrier signal may be higher than a power transfer frequency between the receiving coil  20  and the transmission coil  24  so that the temperature signal does not interfere with charging of the internal power source  16 . In one exemplary embodiment, the carrier frequency is a frequency selected from the following: 13.56 MHz, 433 MHz, 900 MHz, or 2.4 GHz and may be sent using a unidirectional or bidirectional communication channel. Additionally, the implantable controller  12  may also have an antenna, transducer, transmitter, receiver, transceiver, or the like to receive the temperature signal from the receiving coil  20 . After receiving the temperature signal, the implantable controller  12  then compares the measured temperature of the hermetically sealed package  30  against a predetermined threshold temperature. Further, the carrier signal may also be wirelessly transmitted to an external radio (not shown) in the external transmission coil  24  and then wirelessly relayed to the external controller  26  from the external radio of the transmission coil  24 . 
     Additionally, it should be noted that although  FIG. 3  illustrates the plurality of tuning capacitors  34 , at least one temperature sensor  36 , temperature measuring circuit  40 , scavenging circuitry  44 , and transceiver  46  as being located within the hermetically sealed package  30 , any or all of these components may also be disposed outside of the hermetically sealed package  30  if desired by a clinician. 
     Now referring to  FIGS. 3-4 , in an exemplary embodiment, it may be preferable to keep the temperature of the silicone housing  42  below 43° C. Temperatures of the silicone housing  42  above 43° C. may result in discomfort or harm to the patient. Additionally, due to the difference in thermal resistance between the hermetically sealed package  30  and the silicone housing  42 , the temperature of the hermetically sealed package  30  may be higher than 43° C. when the temperature of the silicone housing  42  is 43° C. For example, the hermetically sealed package  30  may have a measured temperature between 43° C. and 65° C. when the silicone housing  42  has a temperature around 43° C. As such, the predetermined threshold temperature may be a temperature between 43° C. and 65° C. depending on the level of thermal resistance between the hermetically sealed package  30  and the surface of the silicone housing  42 . 
     The implantable controller  12  is configured to generate at least one alert if the measured temperature of the hermetically sealed package  30  is greater than the predetermined threshold temperature. Alternatively, the implantable controller  12  may also be configured to reduce and/or disable charging of the internal power source  16  when the temperature of the hermetically sealed package  30  exceeds the predetermined threshold temperature. The at least one alert may be at least one audible, visual, and/or tactile notification transmitted wirelessly, or along at least one cable and/or connector, via Bluetooth or radio frequency to the external controller  26  and/or an external alert device  48 . Transmitting the Bluetooth or radio frequency along a cable to the external controller  26  may be a more efficient method of transmitting the signal and reduce the amount of signal loss when passing the signal through the patient&#39;s tissue. Also, clinicians may be able to further mitigate signal loss by transmitting the signals at Industrial, Scientific, and Medical (ISM) band frequencies such as, for example, 433 MHz, 6.78 MHz, 13.56 MHz, 27.12 MHz, 40.68 MHz, 915 MHz, 403.5 MHz and other similar ISM band frequencies, and/or Medical Implant Communication System (MICS) band frequencies such as, for example, 401 MHz-406 MHz. A full list of ISM frequency bands that are available to clinicians can be found in Table 1 below: 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Center  
                   
                   
               
               
                 Frequency Range 
                 Frequency 
                 Bandwidth 
                 Availability 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 6.765-6.795  
                 MHz 
                 6.78  
                 MHz 
                 30  
                 kHz 
                 Locally 
               
               
                   
                   
                   
                   
                   
                   
                 Administered 
               
               
                 13.553-13.567  
                 MHz 
                 13.56  
                 MHz 
                 14  
                 kHz 
                 Worldwide 
               
               
                 26.957-27.283  
                 MHz 
                 27.12  
                 MHz 
                 326  
                 kHz 
                 Worldwide 
               
               
                 40.66-40.7  
                 MHz 
                 40.68  
                 MHz 
                 40  
                 kHz 
                 Worldwide 
               
               
                 433.05-434.79  
                 MHz 
                 433.92  
                 MHz 
                 1.74  
                 MHz 
                 Region 1,  
               
               
                   
                   
                   
                   
                   
                   
                 Locally 
               
               
                   
                   
                   
                   
                   
                   
                 Administered 
               
               
                 902-928  
                 MHz 
                 915  
                 MHz 
                 26  
                 MHz 
                 Region 2  
               
               
                   
                   
                   
                   
                   
                   
                 (With 
               
               
                   
                   
                   
                   
                   
                   
                 Exceptions) 
               
               
                 2.4-2.5  
                 GHz 
                 2.45  
                 GHz 
                 100  
                 MHz 
                 Worldwide 
               
               
                 5.725-5.875  
                 GHz 
                 5.8  
                 GHz 
                 150  
                 MHz 
                 Worldwide 
               
               
                 24-24.25  
                 GHz 
                 24.125  
                 GHz 
                 250  
                 MHz 
                 Worldwide 
               
               
                 61-61.5  
                 GHz 
                 61.25 
                 GHz 
                 500  
                 MHz 
                 Locally 
               
               
                   
                   
                   
                   
                   
                   
                 Administered 
               
               
                 122-123  
                 GHz 
                 122.5  
                 GHz 
                 1  
                 GHz 
                 Locally 
               
               
                   
                   
                   
                   
                   
                   
                 Administered 
               
               
                 244-246  
                 GHz 
                 245  
                 GHz 
                 2  
                 GHz 
                 Locally 
               
               
                   
                   
                   
                   
                   
                   
                 Administered 
               
               
                   
               
            
           
         
       
     
     The external alert device  48  may be a smartwatch (seen in  FIGS. 1-2 ), tablet, smartphone, display, or any other type of mobile device capable of relaying at least one audible, visual, and tactile notification to a user that the receiving coil  20  and external transmission coil  24  have become misaligned or displaced, and/or that the hermetically sealed package  30  is experiencing elevated temperature levels. Once the implantable controller  12  has reduced or disabled charging of the internal power source  16 , or the user has corrected the alignment of the receiving coil  20  and transmission coil  24 , the alert notification may be terminated automatically or manually by the user via the external controller  26  and/or the external alert device  48 . 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims.