WO2024182632A2

WO2024182632A2 - Systems and methods for optimizing communication with an implantable device

Info

Publication number: WO2024182632A2
Application number: PCT/US2024/017909
Authority: WO
Inventors: Yin-Jui Chang; Albert YOU; Suraj GOWDA
Original assignee: Iota Biosciences, Inc.
Priority date: 2023-03-02
Filing date: 2024-02-29
Publication date: 2024-09-06
Also published as: WO2024182632A3

Abstract

A method for improving communication with an implantable device in a subject can include determining, by a computing system, for a plurality of sampling times, a current position and a current orientation of an interrogator. The interrogator may include a transducer configured to communicate with the implantable device and an inertial measurement unit. The current position and the current orientation of the interrogator may be determined relative to a target contact location on the subject using interrogator location data received from the inertial measurement unit. The target contact location may be associated with a location of the implantable device in the subject. The computing system may then generate control information indicating to a user how to move the interrogator in order to improve communication with the implantable device based on the target contact location, the current position and current orientation of the interrogator, and the location of the implantable device.

Description

Attorney Docket No.: 78895-20030.40 SYSTEMS AND METHODS FOR OPTIMIZING COMMUNICATION WITH AN IMPLANTABLE DEVICE CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims the priority benefit of United States Provisional Patent Application Serial No.63/449,545, filed March 2, 2023, the contents of which are incorporated herein by reference in its entirety. FIELD [0002] The present disclosure relates to systems and methods for improving wireless communication quality between a medical device and an external device, in particular between an implantable medical device and a medical interrogator external to the implant. BACKGROUND [0003] Many medical devices, particularly implantable medical devices, can be used to provide insight into the subject’s health (e.g., by collecting physiological signal data) and, in some cases, to provide treatment for various diseases (e.g., by stimulating tissue within the subject). For example, implantable devices for monitoring intraocular pressure may be used to monitor the health of patients with glaucoma. [0004] The capability of certain implantable devices to store energy and information for extended periods of time may be limited due to the size of said devices. External devices outside of such implants may be used to provide the implants with power and to transfer data collected by the implants to users through wireless communication links. Maintaining such communication links can, however, be challenging. Relative motion between an external device and an implant during communication (e.g., due to hand motions of an operator of the external device or due to natural shifting of the implant within the subject’s body) may significantly impact the quality of the communication link and, as a result, may severely affect the implant’s ability to function. SUMMARY [0005] Creating and maintaining strong, high quality communication links between implantable devices and the external devices that power and harvest information from the implants is critical to the implants’ functionality. Accordingly, provided are systems and methods for optimizing communication between an implantable device and a second device (referred to hereinafter as an “interrogator”) outside of the implant that provides power to and Attorney Docket No.: 78895-20030.40 collects information from the implant. The systems and methods leverage an inertial measurement unit mounted within or on the interrogator to provide a computing system with movement data associated with the interrogator as the interrogator is moved by an operator. At any given point in time, the computing system can estimate the current position and the current orientation of the interrogator relative to a target location at which communication between the implant and the interrogator is optimized. The computing system can then generate control information that indicates to the interrogator’s operator how the interrogator should be moved (e.g., by adjusting the position or orientation of the interrogator) in order to improve transfer of energy or communication of information between the interrogator and the implant. [0006] The control information generated by the computing system may take a variety of forms. For instance, the information may include instructions (e.g., text-based instructions) that suggest adjustments to the interrogator’s position or orientation. The computing system may also generate and provide the operator with visual indicators (for example, using a user interface with a display) that show the operator the interrogator’s current position and orientation relative to the target location. The visual indicators may be continuously updated as the operator moves the interrogator, allowing the operator to easily determine whether they are adjusting the interrogator’s location in a manner that improves communication between the interrogator and the implant. [0007] In addition to facilitating the tracking and controlling the motion of the interrogator as the interrogator is moved to the target location, the described systems and methods may enable users to monitor and verify communication strength and quality between the interrogator and the implant once the interrogator is at the target location. Specifically, after the interrogator operator has successfully placed the interrogator at the target location using the control information and communication between the interrogator and the implant has commenced, the computing system may evaluate the quality level of signals transmitted from the implant. A low communication quality level may indicate, for example, that the target location requires updating. A high communication quality level, on the other hand, may indicate that the target location is accurate, in which case it may be stored by the computing system for use in future interrogation sessions. The quality level evaluations may also be used by the computing system to generate images that indicate locations within the cross-section of the implantable device at which signal quality levels exceed a threshold value. [0008] A method for improving communication with an implantable device in a subject may comprise determining, by a computing system comprising one or more memories and Attorney Docket No.: 78895-20030.40 one or more processors, for a plurality of sampling times, a current position and a current orientation of an interrogator comprising: a transducer configured to communicate with the implantable device, and an inertial measurement unit. The current position and the current orientation of the interrogator may be determined relative to a target contact location on the subject using interrogator location data received from the inertial measurement unit. The target contact location may be associated with a location of the implantable device in the subject. The method may further comprise generating, by the computing system, control information indicating to a user how to move the interrogator in order to improve communication with the implantable device based on the target contact location, the current position and the current orientation of the interrogator, and the location of the implantable device. [0009] In some embodiments, the method comprises determining the target contact location. [0010] In some embodiments of the method, determining the target contact location comprises: transmitting, using the transducer, a plurality of signals to the subject, receiving, using the transducer, signals of the plurality of signals that are reflected by the implantable device, and identifying, using the computing system, a peak in reflected signal data received from the transducer, wherein the peak corresponds to a point in time at which a location of the interrogator was most closely aligned with the location of the implantable device in the subject. [0011] In some embodiments, the method comprises removing interference data from the reflected signal data prior to identifying the peak in the reflect signal data. [0012] In some embodiments of the method, the interference data is removed from the reflected signal data using high-pass filtering. [0013] In some embodiments, the method comprises storing the determined target contact location in a memory of the one or more memories of the computing system. [0014] In some embodiments of the method, the interrogator location data received from the inertial measurement unit comprises acceleration measurements associated with each of the plurality of sampling times, and wherein the current position of the interrogator at each sampling time is determined based on the acceleration measurement for the sampling time and a position of the interrogator at a previous sampling time. [0015] In some embodiments, the method comprises removing noise data from the acceleration measurements using the computing system prior to determining the current position of the interrogator. Attorney Docket No.: 78895-20030.40 [0016] In some embodiments of the method, the noise data is removed from the acceleration measurements using a polynomial detrending algorithm. [0017] In some embodiments of the method, the noise data is removed from the acceleration measurements using high-pass filtering. [0018] In some embodiments of the method, the interrogator location data received from the inertial measurement unit comprises gyroscope measurements associated with each of the plurality of sampling times, and wherein the current orientation of the interrogator at each sampling time is determined based on the gyroscope measurement for the sampling time. [0019] In some embodiments of the method, generating the control information comprises determining a first error value indicating a difference between the current position of the interrogator and the target contact location and a second error value indicating a deviation of the current orientation of the interrogator from a target orientation. [0020] In some embodiments of the method, the target orientation depends on the location of the implantable device in the subject. [0021] In some embodiments of the method, the target orientation is normal to a contact surface on the subject. [0022] In some embodiments of the method, the control information comprises instructions for adjusting the current position or the current orientation of the interrogator in order to reduce a magnitude of the first error value or a magnitude of the second error value. [0023] In some embodiments of the method, the computing system comprises a display, and the method comprises generating, by the computing system, for each of the plurality of sampling times, one or more maps indicating the current position and the current orientation of the interrogator relative to the target contact location and displaying, by the computing system, the one or more maps. [0024] In some embodiments of the method, the one or more maps for each sampling time indicate one or more positions or one or more orientations of the interrogator at previous sampling times. [0025] In some embodiments, the method comprises moving the interrogator based on the control information, receiving, by the transducer, a signal transmitted from the implantable device, and evaluating, by the computing system, a quality level of the signal received from the implantable device. [0026] In some embodiments, the computing system comprises a display and the method comprises generating, by the computing system, a two-dimensional image of a cross-section of the implantable device that indicates one or more locations within the cross section where Attorney Docket No.: 78895-20030.40 quality levels of a plurality of signals received by the transducer from the implantable device exceed a threshold quality level, and displaying, by the computing system, the two- dimensional image of the cross-section of the implantable device. [0027] In some embodiments of the method, a quality level of a signal received from the implantable device is a signal-to-noise ratio of the signal. [0028] In some embodiments, the method comprises iteratively repeating the steps of determining the current position and the current orientation of the interrogator and generating the control information until the control information indicates that the interrogator should not be moved. [0029] In some embodiments, the method comprises receiving, by the transducer, physiological signal data from the implantable device. [0030] In some embodiments of the method, the transducer is an ultrasonic transducer, and the physiological signal data is received from ultrasonic backscatter emitted by the implantable device. [0031] In some embodiments of the method, the transducer is a radio frequency (RF) antenna, and the physiological signal data is received from radio wave backscatter emitted by the implantable device. [0032] In some embodiments of the method, the physiological signal data comprise a pressure. [0033] In some embodiments of the method, the pressure is an intraocular pressure. [0034] In some embodiments of the method, the physiological signal data comprise a concentration of an analyte. [0035] In some embodiments of the method, the physiological signal data comprise a pH. [0036] In some embodiments of the method, the physiological signal data comprise a local field potential in a brain or an evoked action potential in a brain. [0037] In some embodiments of the method, the physiological signal data comprise an electrophysiological pulse. [0038] In some embodiments, the method comprises transmitting to the implantable device, using the transducer, a powering signal configured to provide energy to the implantable device. [0039] In some embodiments of the method, the transducer is an ultrasonic transducer, and the powering signal comprises ultrasonic waves. [0040] In some embodiments of the method, transducer is a radio frequency (RF) antenna, and the powering signal comprises radio waves. Attorney Docket No.: 78895-20030.40 [0041] A system for improving communication with an implantable device in a subject may comprise an interrogator comprising a transducer configured to communicate with the implantable device and an inertial measurement unit, and a computing system comprising one or more memories and one or more processors communicatively coupled to the interrogator and configured to: determine, for a plurality of sampling times, a current position and a current orientation of the interrogator relative to a target contact location on the subject using interrogator location data received from the inertial measurement unit, wherein the target contact location is associated with a location of the implantable device in the subject, and generate control information indicating to a user how to move the interrogator for improving communication with the implantable device based on the target contact location, the current position of the interrogator, the current orientation of the interrogator, and the location of the implantable device. [0042] In some embodiments of the system, the computing system is configured to determine the target contact location. [0043] In some embodiments of the system, the transducer is configured to receive signals reflected by the implantable device, and determining the target contact location comprises identifying, using the computing system, a peak in reflected signal data received from the transducer, wherein the peak corresponds to a point in time at which a location of the interrogator was most closely aligned with the location of the implantable device in the subject. [0044] In some embodiments of the system, interference data is removed from the reflected signal data prior to identifying the peak in the reflect signal data. [0045] In some embodiments of the system, the interference data is removed from the reflected signal data using high-pass filtering. [0046] In some embodiments of the system, the computing system is configured to store the determined target contact location in a memory of the one or more memories. [0047] In some embodiments of the system, the interrogator location data received from the inertial measurement unit comprises acceleration measurements associated with each of the plurality of sampling times, and wherein the current position of the interrogator at each sampling time is determined based on the acceleration measurement for the sampling time and a position of the interrogator at a previous sampling time. [0048] In some embodiments of the system, noise data is removed from the acceleration measurements using the computing system prior to determining the current position of the interrogator. Attorney Docket No.: 78895-20030.40 [0049] In some embodiments of the system, the noise data is removed from the acceleration measurements using a polynomial detrending algorithm. [0050] In some embodiments of the system, the noise data is removed from the acceleration measurements using high-pass filtering. [0051] In some embodiments of the system, the interrogator location data received from the inertial measurement unit comprises gyroscope measurements associated with each of the plurality of sampling times, and wherein the current orientation of the interrogator at each sampling time is determined based on the gyroscope measurement for the sampling time. [0052] In some embodiments of the system, generating the control information comprises determining a first error value indicating a difference between the current position of the interrogator and the target contact location and a second error value indicating a deviation of the current orientation of the interrogator from a target orientation. [0053] In some embodiments of the system, the target orientation depends on the location of the implantable device in the subject. [0054] In some embodiments of the system, the target orientation is normal to a contact surface on the subject. [0055] In some embodiments of the system, the control information comprises instructions for adjusting the current position or the current orientation of the interrogator in order to reduce a magnitude of the first error value or a magnitude of the second error value. [0056] In some embodiments of the system, the computing system comprises a display, and the computing system is configured to generate, for each of the plurality of sampling times, one or more maps indicating the current position and the current orientation of the interrogator relative to the target contact location and display the one or more maps on the display. [0057] In some embodiments of the system, the one or more maps for each sampling time indicate one or more positions or one or more orientations of the interrogator at previous sampling times. [0058] In some embodiments of the system, the computing system comprises a display, wherein the computing system is configured to generate a two-dimensional image of a cross- section of the implantable device that indicates one or more locations within the cross section where quality levels of a plurality of signals received from the implantable device by the transducer exceed a threshold quality level and display the two-dimensional image of the cross-section of the implantable device on the display. Attorney Docket No.: 78895-20030.40 [0059] In some embodiments of the system, a quality level of a signal received from the implantable device is a signal-to-noise ratio of the signal. [0060] In some embodiments of the system, the transducer is an ultrasonic transducer. [0061] In some embodiments of the system, the transducer is a radio frequency (RF) antenna. [0062] In some embodiments of the system, the transducer is configured to receive physiological signal data from the implantable device. [0063] In some embodiments of the system, the transducer is configured to transmit, to the implantable device, a powering signal configured to provide energy to the implantable device. [0064] In some embodiments of the system, the implantable device is fully implanted in the subject. [0065] In some embodiments of the system, the implantable device is implanted in an eye. [0066] In some embodiments of the system, the implantable device is implanted on or in nervous tissue. [0067] In some embodiments of the system, the nervous tissue is brain tissue. [0068] In some embodiments of the system, the nervous tissue is a peripheral nerve. [0069] In some embodiments of the system, the peripheral nerve is a splenic nerve. [0070] In some embodiments of the system, the implantable device is implanted on or in organ tissue. [0071] In some embodiments of the system, the organ is a bladder. [0072] In some embodiments of the system, the organ is a heart. [0073] In some embodiments of the system, the organ is a muscle. [0074] In some embodiments of the system, the organ is a stomach. [0075] A non-transitory computer readable storage medium may store instruction for improving communication with an implantable device in a subject, wherein, when executed by one or more processors of a computing system, the instructions are configured to cause the computing system to determine, for a plurality of sampling times, a current position and a current orientation of an interrogator comprising a transducer configured to communicate with the implantable device and an inertial measurement unit, wherein the current position and the current orientation of the interrogator are determined relative to a target contact location on the subject using interrogator location data received from the inertial measurement unit, wherein the target contact location is associated with a location of the Attorney Docket No.: 78895-20030.40 implantable device in the subject, and generate control information indicating to a user how to move the interrogator in order to improve communication with the implantable device based on the target contact location, the current position and the current orientation of the interrogator, and the location of the implantable device. [0076] In some embodiments of the non-transitory computer readable storage medium, the instructions are configured to cause the computing system to determine the target contact location. [0077] In some embodiments of the non-transitory computer readable storage medium, the transducer is configured to receive signals reflected by the implantable device, and determining the target contact location comprises identifying, using the computing system, a peak in reflected signal data received from the transducer, wherein the peak corresponds to a point in time at which a location of the interrogator was most closely aligned with the location of the implantable device in the subject. [0078] In some embodiments of the non-transitory computer readable storage medium, interference data is removed from the reflected signal data prior to identifying the peak in the reflect signal data. [0079] In some embodiments of the non-transitory computer readable storage medium, the interference data is removed from the reflected signal data using high-pass filtering. [0080] In some embodiments of the non-transitory computer readable storage medium, the computing system comprises one or more memories, and wherein the instructions are configured to cause the computing system to store the determined target contact location in a memory of one or more memories. [0081] In some embodiments of the non-transitory computer readable storage medium, the interrogator location data received from the inertial measurement unit comprises acceleration measurements associated with each of the plurality of sampling times, and wherein the current position of the interrogator at each sampling time is determined based on the acceleration measurement for the sampling time and a position of the interrogator at a previous sampling time. [0082] In some embodiments of the non-transitory computer readable storage medium, noise data is removed from the acceleration measurements prior to determining the current position of the interrogator. [0083] In some embodiments of the non-transitory computer readable storage medium, the noise data is removed from the acceleration measurements using a polynomial detrending algorithm. Attorney Docket No.: 78895-20030.40 [0084] In some embodiments of the non-transitory computer readable storage medium, the noise data is removed from the acceleration measurements using high-pass filtering. [0085] In some embodiments of the non-transitory computer readable storage medium, the interrogator location data received from the inertial measurement unit comprises gyroscope measurements associated with each of the plurality of sampling times, and wherein the current orientation of the interrogator at each sampling time is determined based on the gyroscope measurement for the sampling time. [0086] In some embodiments of the non-transitory computer readable storage medium, generating the control information comprises determining a first error value indicating a difference between the current position of the interrogator and the target contact location and a second error value indicating a deviation of the current orientation of the interrogator from a target orientation. [0087] In some embodiments of the non-transitory computer readable storage medium, the target orientation depends on the location of the implantable device in the subject. [0088] In some embodiments of the non-transitory computer readable storage medium, the target orientation is normal to a contact surface on the subject. [0089] In some embodiments of the non-transitory computer readable storage medium, the control information comprises instructions for adjusting the current position or the current orientation of the interrogator in order to reduce a magnitude of the first error value or a magnitude of the second error value. [0090] In some embodiments of the non-transitory computer readable storage medium, the computing system comprises a display, and the instructions are configured to cause the computing system to generate, for each of the plurality of sampling times, one or more maps indicating the current position and the current orientation of the interrogator relative to the target contact location and display the one or more maps on the display. [0091] In some embodiments of the non-transitory computer readable storage medium, the one or more maps for each sampling time indicate one or more positions or one or more orientations of the interrogator at previous sampling times. [0092] In some embodiments of the non-transitory computer readable storage medium, the instructions are configured to cause the computing system to evaluate a quality level of a signal received by the transducer from the implantable device. [0093] In some embodiments of the non-transitory computer readable storage medium, the instructions are configured to cause the computing system to generate a two-dimensional image of a cross-section of the implantable device that indicates one or more locations within Attorney Docket No.: 78895-20030.40 the cross section where quality levels of a plurality of signals received by the transducer from the implantable device exceed a threshold quality level, and display the two-dimensional image of the cross-section of the implantable device on the display. [0094] In some embodiments of the non-transitory computer readable storage medium, a quality level of a signal received from the implantable device is a signal-to-noise ratio of the signal. [0095] In some embodiments of the non-transitory computer readable storage medium, the implantable device is fully implanted in the subject. [0096] In some embodiments of the non-transitory computer readable storage medium, the implantable device is implanted in an eye. [0097] In some embodiments of the non-transitory computer readable storage medium, the implantable device is implanted on or in nervous tissue. [0098] In some embodiments of the non-transitory computer readable storage medium, the nervous tissue is brain tissue. [0099] In some embodiments of the non-transitory computer readable storage medium, the nervous tissue is a peripheral nerve. [0100] In some embodiments of the non-transitory computer readable storage medium, the peripheral nerve is a splenic nerve. [0101] In some embodiments of the non-transitory computer readable storage medium, the implantable device is implanted on or in organ tissue. [0102] In some embodiments of the non-transitory computer readable storage medium, the organ is a bladder. [0103] In some embodiments of the non-transitory computer readable storage medium, the organ is a heart. [0104] In some embodiments of the non-transitory computer readable storage medium, the organ is a muscle. [0105] In some embodiments of the non-transitory computer readable storage medium, the organ is a stomach. BRIEF DESCRIPTION OF THE FIGURES [0106] Various aspects of the disclosed systems and methods are set forth with particularity in the appended claims. A better understanding of the features and advantages of the disclosed systems and methods can be obtained by reference to the detailed description of illustrative embodiments and the accompanying drawings. Attorney Docket No.: 78895-20030.40 [0107] FIG.1 shows a method for improving communication with an implantable device in a subject, according to some embodiments. [0108] FIG.2 shows a system for improving communication with an implantable device in a subject, according to some embodiments. [0109] FIG.3 shows a block diagram of an interrogator with an inertial measurement unit, according to some embodiments. [0110] FIG.4 shows internal and external views of an interrogator with an inertial measurement unit, according to some embodiments. [0111] FIG.5 shows internal and external perspective views of an interrogator with an inertial measurement unit, according to some embodiments. [0112] FIG.6 shows a representation of an interrogator communicating with an intraocular implant, according to some embodiments. [0113] FIG.7 shows a method for determining a target contact location on a subject, according to some embodiments. [0114] FIG.8 shows reflected signal data received by an interrogator while a target contact location on a subject is being determined, according to some embodiments. [0115] FIG.9A shows a method for determining current interrogator position and orientation, according to some embodiments. [0116] FIG.9B shows data comparing the performance of a high-pass filter and a polynomial detrending algorithm for noise removal, according to some embodiments. [0117] FIG.10A shows locations of an interrogator, an inertial measurement unit, and an implantable device in a subject relative to a reference frame of the subject, according to some embodiments. [0118] FIG.10B shows reference frames of a contact surface of an interrogator and an inertial measurement unit, according to some embodiments. [0119] FIG.11A shows interrogator position data, according to some embodiments. [0120] FIG.11B shows interrogator position data, according to some embodiments. [0121] FIG.11C shows interrogator position data, according to some embodiments. [0122] FIG.11D shows interrogator position data, according to some embodiments. [0123] FIG.12 shows acceleration and orientation data collected by an inertial measurement unit in an interrogator, according to some embodiments. [0124] FIG.13 shows interrogator position and orientation data, according to some embodiments. Attorney Docket No.: 78895-20030.40 [0125] FIG.14 shows a method for displaying images of interrogator position and orientation, according to some embodiments. [0126] FIG.15 shows a visualization of interrogator control information, according to some embodiments. [0127] FIG.16 shows a method for evaluating a quality level of communication between an implant and an interrogator, according to some embodiments. [0128] FIG.17 shows a method for generating a visualization of locations within an implantable device at which communication between the implant and an interrogator is strongest, according to some embodiments. [0129] FIG.18 shows an image of locations within an implantable device at which communication between the implant and an interrogator is strongest, according to some embodiments. [0130] FIG.19 shows a method for optimizing communication with an implantable device, according to some embodiments. DETAILED DESCRIPTION [0131] Described herein are methods and systems for improving communication between an interrogator and a separate implantable device in a subject. The interrogator may be an external device (for example external to the subject), while the implantable device may be implanted in the subject. The communication may be performed using ultrasonic or radiofrequency (RF) waves, for example ultrasonic or RF waves generated by the interrogator and delivered to the implantable device and/or backscatter waves emitted from the implantable device and received by the interrogator. Optimal communication relies on communication signals being directly targeted from the interrogator. Thus, the methods and systems described herein can allow the interrogator to be repositioned to optimize the ultrasonic or RF connection between the implantable device and the interrogator. [0132] A method for improving communication with an implantable device can include, for example, determining, for a plurality of sampling times, a current position and a current orientation of an interrogator, and generating control information indicating to a user how to move the interrogator in order to improve communication with the implantable device based on a target contact location, a current position and orientation of the interrogator, and the location of the implantable device. The current position and orientation of the interrogator are determined relative to the target location on the subject using interrogator location data received from an internal measurement unit on the interrogator. Attorney Docket No.: 78895-20030.40 [0133] Also described herein is a system for improving communication with an implantable device in a subject. The system can include an interrogator and a computing system. The interrogator includes a transducer configured to communicate with the implantable device and an inertial measurement unit. The computing system can include one or more memories and one or more processors communicatively coupled to the interrogator. Further, the computing system is configured to determine, for a plurality of sampling times, a current position and a current orientation of the interrogator relative to a target contact location on the subject using interrogator location data received from the inertial measurement unit, wherein the target contact location is associated with a location of the implantable device in the subject; and generate control information indicating to a user how to move the interrogator for improving communication with the implantable device based on the target contact location, the current position of the interrogator, the current orientation of the interrogator, and the location of the implantable device. Definitions [0134] As used herein, the singular forms “a”, “an”, and “the” include the plural reference unless the context clearly dictates otherwise. [0135] Reference to “about” a value or parameter herein includes (and describes) variations that are directed to that value or parameter per se. For example, description referring to “about X” includes description of “X”. [0136] It is understood that aspects and variations of the invention described herein include “consisting” and/or “consisting essentially of” aspects and variations. [0137] When a range of values or values is provided, it is to be understood that each intervening value between the upper and lower limit of that range, and any other stated or intervening value in that stated range, is encompassed within the scope of the present disclosure. Where the stated range includes upper or lower limits, ranges excluding either of those included limits are also included in the present disclosure. [0138] The section headings used herein are for organization purposes only and are not to be construed as limiting the subject matter described. The description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the described embodiments will be readily apparent to those persons skilled in the art and the generic principles herein may be applied to other embodiments. Thus, the present invention is not Attorney Docket No.: 78895-20030.40 intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein. [0139] The figures illustrate processes according to various embodiments. In the exemplary processes, some blocks are, optionally, combined, the order of some blocks is, optionally, changed, and some blocks are, optionally, omitted. In some examples, additional steps may be performed in combination with the exemplary processes. Accordingly, the operations as illustrated (and described in greater detail below) are exemplary by nature and, as such, should not be viewed as limiting. [0140] Finally, it is to be understood that features and preferences described in relation to “embodiments” are distinct preferences and are not limited only to that particular embodiment; they may be freely combined with features from other embodiments, where technically feasible, and may form preferred combinations of features. The description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the described embodiments will be readily apparent to those persons skilled in the art and the generic principles herein may be applied to other embodiments. Thus, the present invention is not intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein. Method for improving communication [0141] The methods for improving communication between an implantable device and an interrogator outside of the implant may be employed whenever the interrogator is used to communicate with the implantable device. Such interrogation sessions may occur, for example, when the implantable device requires energy to conduct a measurement of a physiological signal in a subject or to provide treatment to the subject, or when a user wishes to extract information related to the implantable device’s function from the implantable device. The provided methods may allow interrogator operators to create and maintain high quality communication links that can efficiently communicate energy and accurately communicate information between the interrogator and the implantable device and may, as a result, significantly improve the quality of treatment that the implantable device is capable of providing to the subject. [0142] An exemplary method 100 for improving communication between an implantable device in a subject and an interrogator is shown in FIG.1. Method 100 may be executed by a computing system that is communicatively coupled to the interrogator. The interrogator may Attorney Docket No.: 78895-20030.40 comprise a transducer (e.g., an ultrasonic transducer or an antenna) configured to wirelessly communicate with a second transducer in the implantable device. Additionally, the interrogator may include an inertial measurement unit. [0143] During an interrogation session, the interrogator may be moved (e.g., relative to the subject in which the implantable device is implanted) by the interrogator operator. The inertial measurement unit may collect interrogator location or movement data for a plurality of sampling times during the interrogation session. The interrogator location or movement data may include triaxial acceleration data indicating the triaxial acceleration of the interrogator at each sampling time as well as triaxial gyroscope data indicating the angular velocity of the interrogator at each sampling time. The computing system may receive the interrogator location data from the inertial measurement unit and determine, for each sampling time, a current position and a current orientation of the interrogator using the interrogator location data (step 102). This can be accomplished using, for example, a dead- reckoning algorithm. [0144] The current position and the current orientation of the interrogator may be determined relative to a target contact location on the subject. The target contact location may be associated with a location of the implantable device within the subject and may indicate a location on the subject at which the interrogator should be placed in order to create a high- quality communication link between the interrogator and the implantable device. For instance, the target contact location may be a location on an outer surface of the subject’s body that is the shortest distance from the location of implantable device inside of the subject’s body. In some situations, the computing system may determine the target contact location prior to the initiation of an interrogation session; in other situations, computing system may retrieve a previously identified or determined target contact location that is stored in a memory of the computing system. In addition to identifying a location on the subject at which the interrogator should be placed, the target contact location can also provide information about how the interrogator should be oriented in order to optimize interrogator- implant communication. [0145] After the computing system determines the current position and the current orientation of the implantable device relative to the target contact location, the computing system may generate control information that indicates to a user (e.g., the interrogator operator) how to move the interrogator in order to improve communication with the implantable device (step 104). The control information may, for example, indicate that the user should move the interrogator in a certain direction by a certain amount, or may indicate Attorney Docket No.: 78895-20030.40 that the user should orient the interrogator by a certain angle. The control information can include visual data that provides users with a visual reference indicating differences between the interrogator’s current position and orientation and the target contact location. In such cases, the computing system may be configured to control a display and may automatically update the display at each sampling time, allowing users to easily determine whether the interrogator movements being performed are bringing the interrogator closer to the target contact location. [0146] It should be noted that monitoring of the interrogator location relative to the target contact location may persist even after the interrogator has been placed at the target contact location. Since, for example, the interrogator may be hand-operated, the precise position and orientation of the interrogator may change throughout an interrogation session due to minute movements by the operator (e.g., hand tremors). Method 100 may, therefore, be continuously repeated, in whole or in part, throughout any interrogation session in order to provide users with up-to-date information about the location of the interrogator and, in turn, the quality of communication between the interrogator and the implant. System with optimized communication [0147] The methods for optimizing communication with an implantable device may be executed by a computing system and may require interrogator location data received from the interrogator. FIG.2 illustrates a system 200 for improving communication between an interrogator 202 and an implantable device 206 that is implanted in a subject 218. As shown, interrogator 202, which can comprise an inertial measurement unit (IMU) 208 and a transducer 210, may be communicatively coupled to a computing system 204, which may include one or more memories 212, one or more processors 214. Computing system 204 may be coupled to a display 216 (e.g., a monitor or a screen). [0148] As described, IMU 208 may be configured to collect interrogator location data as interrogator 202 is operated by a user. IMU 208 may include an accelerometer 208a configured to measure triaxial acceleration of interrogator 202 and a gyroscope 208b configured to measure triaxial angular velocity of interrogator 202. In other examples, IMU 208 may include additional sensors configured to conduct measurements associated with interrogator movement, for example a magnetometer configured to allow absolute orientation drift to be reset in an inertial reference frame. During an interrogation session, IMU 208 may be configured to conduct interrogator location measurements at a predefined frequency. For example, upon initiation of an interrogation session, IMU 208 may be configured to collect Attorney Docket No.: 78895-20030.40 interrogator location data at least once per second, at least once every five seconds, at least once every 10 seconds, at least once every 15 seconds, at least once every 20 seconds, at least once every 25 seconds, at least once every 30 seconds, at least once every minute, at least once every 5 minutes, or at least once every 10 minutes. In other examples, IMU 208 may collect interrogator location data at higher rates, for example at a rate greater than or equal to 5 Hz, 10 Hz, 15 Hz, 20 Hz, 25 Hz, 30 Hz, 35 Hz, 40 Hz, 45 Hz, 50 Hz, 55 Hz, 60 Hz, 65 Hz, 70 Hz, 75 Hz, 80 Hz, 85 Hz, 90 Hz, 95 Hz, 100 Hz, or 105 Hz. In other examples, IMU 208 may conduct interrogator location measurements at random or arbitrarily determined times or frequencies. IMU 208 may also be configured to conduct an interrogator location measurement on-demand, or, alternatively, may be configured to cease interrogator location measurements on user-demand. Each time at which an interrogator location measurement is performed may be referred to as a “sampling time” (as mentioned, e.g., in step 102 of method 100 shown in FIG.1). [0149] Transducer 210 may be a device or a circuit component configured to convert energy from one form to another form. Transducer 210 may be configured to generate and transmit energy configured to power implantable device 206. Additionally, transducer 210 may be configured to receive and extract information from signals transmitted by implantable device 206. Implantable device 206 may include a second transducer 220 that is configured to harvest energy transmitted by transducer 210 and to generate and transmit signals encoding information to be transmitted to transducer 210. [0150] In some embodiments, transducer 210 and transducer 220 are ultrasonic transducers. An ultrasonic transducer may include a piezoelectric material (e.g., a piezoelectric crystal) that mechanically moves or deforms in the presence of electric fields (e.g., due to an applied current), thereby generating ultrasonic waves. Conversely, in the presence of ultrasonic waves, vibrations induced in the piezoelectric material generate an electric current. [0151] Energy may be transferred between interrogator 202 and implantable device 206 using ultrasonic waves generated by transducer 210 and harvested by transducer 220. Receipt of the ultrasonic waves may cause transducer 220 to generate an electric current carrying energy from the ultrasonic waves. Implantable device 206 may comprise a digital control circuit 222 configured to direct the generated electric current to a power circuit 224, which may comprise circuitry configured to convert the electric current into usable power for implantable device 206 (e.g., an AC/DC rectifier for converting alternating current into direct current that can be used by other components of implantable device 206). Power circuit 224 Attorney Docket No.: 78895-20030.40 may also include energy storage circuitry, for example one or more capacitors or one or more rechargeable or non-rechargeable batteries. [0152] Ultrasonic waves generated by transducer 210 for harvesting by transducer 220 can also include encoded information, for example an encoded command configured to cause implantable device 206 to perform an action (e.g., conduct a measurement of a physiological signal). Control circuit 222 of implantable device 206 may be configured to decode information carried by ultrasonic waves generated by transducer 210 and to control various components of implantable device 206 based on the decoded information. [0153] Information may be transferred to interrogator 202 from implantable device 206 using ultrasonic backscatter. Implantable device 206 may encode information in current flowing through implantable device 206 by modulating the current as a function of the information. Modulating the current to encode information may comprise changing an amplitude, a frequency, or a phase of the current; the modulation may be performed by modulation circuitry and controlled by control circuit 222. The modulated current may be applied to transducer 220, causing transducer 220 to generate backscatter ultrasonic waves that carry the information encoded in the modulated current. These backscatter ultrasonic waves may be received by transducer 210, which may convert the backscatter ultrasonic waves into an electric current. Interrogator 202 may include circuitry configured to extract the encoded information from the electric current generated by transducer 210 as a result of the backscatter ultrasonic waves. In other examples, information may be transferred to interrogator 202 from implantable device 206 using ultrasonic pulses that are actively generated by transducer 220. [0154] In other embodiments, transducer 210 and transducer 220 are radio frequency (RF) antennas. A RF antenna may comprise an array of electrical conductors. In the presence of radio waves – i.e., electromagnetic waves oscillating at radio frequencies (e.g., frequencies less than or equal to about 300 GHz) – electric current may be induced in the conductors. Conversely, when electric current is applied to the RF antenna, the RF antenna may be configured to generate and radiate electromagnetic waves at radio frequencies. [0155] Energy may be transferred between interrogator 202 and implantable device 206 using radio waves generated by transducer 210 and harvested by transducer 220. Receipt of the radio waves may induce an electric current in transducer 220 that carries energy from the radio waves. Digital control circuit 222 of implantable device 206 may be configured to direct the generated electric current to the power circuit 224, which may convert the electric current into usable power for implantable device 206 as previously described. Attorney Docket No.: 78895-20030.40 [0156] Radio waves emitted by transducer 210 for harvesting by transducer 220 can also include encoded information, for example an encoded command configured to cause implantable device 206 to perform an action (e.g., conduct a measurement of a physiological signal). Control circuit 222 of implantable device 206 may be configured to decode information carried by radio waves emitted by transducer 210 and to control various components of implantable device 206 based on the decoded information. [0157] Information may be transferred to interrogator 202 from implantable device 206 using RF backscatter. Implantable device 206 may encode information in current flowing through implantable device 206 by modulating the current as a function of the information. The modulated current may be applied to transducer 220, causing transducer 220 to emit backscatter RF waves that carry the information encoded in the modulated current. These backscatter RF waves may be harvested by and induce an electric current in transducer 210. Interrogator 202 may include circuitry configured to extract the encoded information from the electric current generated by transducer 210 as a result of the backscatter RF waves. In other examples, information may be transferred to interrogator 202 from implantable device 206 using radio wave pulses that are actively generated by transducer 220. [0158] As described, implantable device 206 may be configured to detect physiological signals within or provide treatment to subject 218. Subject 218 may be a human patient receiving treatment for a medical issue or disease such as a cancer (e.g., colorectal cancer), an autoimmune disease (e.g., diabetes), glaucoma, or incontinence. Implantable device 206 may be configured to be fully or partially implanted in subject 218. For example, implantable device 206 may be configured to be implanted in or attached to tissue within subject 218 such as organ tissue (e.g., eye tissue, stomach tissue, heart tissue, liver tissue, bladder tissue, muscle tissue, etc.) or nervous tissue (e.g., brain tissue, peripheral nerve tissue including splenic nerve tissue, etc.). [0159] Implantable device 206 may comprise one or more sensors 226 configured to detect physiological signals. Sensors 226 may include a pressure sensor, a pH sensor, a temperature sensor, a sensor configured to detect a presence of an analyte (e.g., glucose), sensors configured to detect an electrophysiological pulse, a sensor configured to detect an evoked action potential in a brain, or a sensor configured to detect a local field potential in a brain. In some embodiments, sensors 226 comprise one or more electrodes configured to attach to and deliver stimulation current to tissue in subject 218 (e.g., nerve tissue). Physiological signal data collected by sensors 226 may be included in information transferred Attorney Docket No.: 78895-20030.40 from implantable device 206 to interrogator 202, for example using ultrasonic wave or radio wave backscatter as previously discussed. [0160] Interrogator 202 may be communicatively coupled to computing system 204. Computing system 204 may be or may comprise a desktop computer, a laptop computer, a tablet computer, a mobile device (e.g., a smart phone), or a server. Memory/memories 212 may comprise any device(s) configured to provide storage, including electrical, magnetic, or optical memory. For example, memory/memories 212 may include a random-access memory (RAM), a cache, a hard drive, a CD-ROM drive, a tape drive, or a removable storage disk. Memory/memories 212 may store software comprising programs or instructions for executing methods described herein such as method 100 shown in FIG.1. Software may be executed by processors 214, which may comprise digital circuitry, microcontrollers, microprocessors, embedded processors, central processing units (CPUs), or graphical processing units (GPUs). [0161] Communicative coupling between interrogator 202 and computer system 204 may be wired or wireless. For example, interrogator 202 and computer system 204 may be configured to communicate information through a data transfer cable (e.g., a USB cable) or via a network connection (e.g., a WiFi connection), a Bluetooth connection, or a radio frequency connection. In some embodiments, interrogator 202 and computer system 204 can communicate information through both wired and wireless connections. [0162] Display 216 may be a monitor or a screen configured to couple to and be controlled by processors 214 in computer system 204. Display 216 may be a component of a user interface configured to receive input from a user (e.g., an operator of interrogator 202). In some embodiments, display 216 can comprise an LCD display, an LED display, a display for a personal computer, or a display for a mobile device (e.g., a touch screen on a smart phone). Processors 214 may control information displayed on display 216 through a wired connection (e.g., through an HDMI cable connecting display 216 to computer system 204) or through a wireless connection (e.g., a Bluetooth connection). [0163] A block diagram of interrogator 202 is shown in FIG.3, and various views of exemplary implementations of interrogator 202 are shown in FIGS.4-5. As shown, IMU 208 may be disposed within a housing 234 of interrogator 202, for example along the longest central axis of interrogator 202. Alternatively, IMU 208 can be mounted on an external surface of interrogator 202, such as on an end portion of interrogator 202. [0164] A spacer 228 may be disposed at one end of interrogator 202 adjacent to transducer 210. During an interrogation session, spacer 228 may be placed on subject 218. Attorney Docket No.: 78895-20030.40 Spacer 228 may comprise a plastic material (e.g., a TPX plastic material) and may be configured to create space between transducer 210 and subject 218. [0165] During an interrogation session, contact medium 230 (e.g., a disposable medium such as an ultrasound gel) may be placed on or near subject 218 or on a surface of spacer 228. Contact medium 230 may facilitate transmission of signals between transducer 210 and transducer 220 in implantable device 206. [0166] One or more cables 232 may connect interrogator 202 to other devices, such as computer system 204 or a power source for interrogator 202. Interrogator 202 may be configured to be hand-held by an operator. [0167] FIG.6 shows an exemplary positioning of interrogator 202 and implantable device 206 during an interrogation session. In this example, implantable device 206 is an intraocular implant that has been implanted in an eye of subject 218. This example is only intended to be illustrative and should not be construed as limiting the invention; as previously explained, implantable device 206 may be implanted in a variety of tissue types in subject 218, including (but not limited to) an eye. [0168] As illustrated, to communicate energy or information, interrogator 202 may be positioned such that a contact point or surface of interrogator 202 (e.g., contact surface 230 shown in FIGS.3-5) is in physical contact with an outer surface of the eye. In situations where implantable device 206 is implanted in a different location within subject 218, interrogator 202 may be positioned such that the contact point or surface is in physical contact with an outer surface of the body of subject 218 that is proximal to the location of implantable device 218. After initial placement of interrogator 202 on subject 218 has been accomplished, IMU 208 may begin collecting interrogator location data. The interrogator location data collected by IMU 208 may be used by a computing system (e.g., computing system 204 shown in FIG.2) to generate control information configured to guide the interrogator operator toward a target contact location on subject 218 in order to improve communication quality between interrogator 202 and implantable device 206, as outlined in method 100 shown in FIG.1. Target contact location [0169] The target contact location, as discussed, may be a location on a subject at which communication (of energy and/or information) between an interrogator and an implantable device is optimized, e.g., a location at which the interrogator should be placed in order to ensure communication with the implantable device is efficient and accurate. For example, the Attorney Docket No.: 78895-20030.40 target contact location can be a location on an outer surface of the subject at which, when the interrogator is placed at the target contact location, the distance between the transducer in the interrogator and the transducer in the implantable device is minimized or is within a predetermined range, for example within about 3 mm, about 5 mm, about 7 mm, about 9 mm, or about 11 mm. [0170] The target contact location may be associated with, and depend upon, the location of the implantable device in the subject. However, while the general location of the implantable device may be known, the precise position and orientation of the implantable device in the subject may not be known. Over time, the implantable device may naturally move due to, for example, respiration or other action by the subject. Thus, improving communication between the implantable device and the interrogator (e.g., by executing method 100 shown in FIG.1) during an interrogation session may first require the target contact location to be determined. [0171] A method 700 for determining a target contact location at which an interrogator should be placed to communicate with an implantable device is provided in FIG.7. Method 700 may be executed by the same system that is configured to execute methods for optimizing communication between the interrogator and the implantable device, for example system 200 shown in FIG.2. [0172] The interrogator may be moved around an area on the subject that is proximal to an estimated location of the implantable device in the subject. As the interrogator is moved around the area, a plurality of signals may be transmitted from the transducer in the interrogator to the subject (step 702). The signals may, for example, comprise ultrasonic waves or radio waves, and may be transmitted at regular or irregular intervals. When the interrogator moves directly over the implantable device, one or more of the signals transmitted by the interrogator to the subject may be reflected back to the interrogator by the implantable device. The interrogator may receive the reflected signals as it passes over the implant (step 704) and collect information associated with the reflected signals (e.g., signal frequency data or signal amplitude data) as reflected signal data. [0173] After receiving the reflected signals, interference data may be removed from the reflected signal data (step 706). Removing interference data may comprise removing data associated with signals that are above or below a cutoff frequency, for example using a high- pass filter or a low-pass filter. Interference data can be removed by the interrogator itself using filters, including filters comprising analog circuit components, or removed algorithmically using programmed filters on the computing system. Once the interference Attorney Docket No.: 78895-20030.40 data has been removed, the computing system may identify one or more peaks in the reflected signal data corresponding to one or more points in time at which the interrogator’s location was most closely aligned with the location of the implantable device (step 708). The target contact location may then be determined based on the identified peaks in the reflected signal data and, in some cases, may be stored in a memory of the computing system (step 710). [0174] Exemplary reflected signal data received by an interrogator while a target contact location on a subject is being determined is shown in FIG.8. In particular, FIG.8 shows exemplary reflected signal data prior to interference removal (plot 800) and after interference removal (plot 802). After interference removal, a peak value of the reflected signal data may be identified. The peak value may correspond to a point in time at which the interrogator passed directly over the implantable device, as shown in plot 804. Using the points in time at which the interrogator passed over the implantable device, the location of the implantable device in the subject and, as a result, the target contact location on the subject, can be identified. [0175] Method 700, in addition being utilized to initially identify a target contact location, may be executed during the execution of a method for improving communication with an implantable device (e.g., method 100) in order to calibrate a system such as system 200. Whenever the interrogator is moved over the location of the implantable device, the current position and orientation of the interrogator may be reset to the location above the implantable device by the computing system. The computing system may then continue to track the position and orientation of the interrogator starting from the “reset” location. Calibrating the system in this manner may help reduce noise and bias in the interrogator location data. Determination of current interrogator position and orientation [0176] The computing system can generate control information for the interrogator operator by determining, at each sampling time that the IMU in the interrogator collects interrogator location data, a current position and a current orientation of the interrogator relative to the target contact location. An exemplary method for determining current interrogator position and orientation is shown in FIG.9A. [0177] The interrogator location data collected by the IMU may include acceleration data collected by an accelerometer in the IMU and gyroscope data collected by a gyroscope in the IMU. The computing system may receive acceleration data and gyroscope data from the interrogator as said data is collected by the IMU (steps 902 and 908). The current location of Attorney Docket No.: 78895-20030.40 the interrogator at a given sampling time may be determined based on an acceleration measurement conducted at the sampling time and a known position of the interrogator at a previous sampling time (step 904), for example by integrating the acceleration measurement twice over the time period between the current sampling time and the previous sampling time and adding the resulting displacement to the previous known position. [0178] In some cases, noise data may be removed from the acceleration data prior to step 904, for example using high-pass filtering or a polynomial detrending algorithm. As shown in FIG.9B, high-pass filtering and polynomial-detrending can achieve comparable performance. [0179] The current orientation of the interrogator at a given sampling time may be similarly determined, i.e., may be determined based on a gyroscope measurement conducted at the sampling time and a known orientation of the interrogator at a previous sampling time (step 910), for example by integrating an angular velocity measurement from the gyroscope data over the time period between the current sampling time and the previous sampling time and adding the resulting angular displacement to the previous known orientation. In some embodiments, the computing system may be configured to identify and balance out gravitational effects on interrogator movement data based on the current orientation. [0180] The values measured by the IMU may be measured in the reference frame of the IMU (or, more precisely, in the reference frame of the sensor in the IMU conducting the measurement, e.g., the accelerometer or the gyroscope). The reference frame of each IMU sensor may move with respect to a global reference frame, e.g., the reference frame of the subject in which the implantable device is implanted or a reference frame of the implantable device. The computing system may, therefore, be configured to automatically derive a transformation between the reference frame of the IMU and the reference frame of the subject. Such reference frames are illustrated in FIGS.10A-10B, with the subject approximated as a sphere for simplicity. [0181] As shown in FIG.10A, the subject (or global) reference frame may be defined by axes ^_^௨^, ^_^௨^, and ^_^௨^, which may meet at a subject origin point 1002. A vector ^_^௨^ may define an outer surface of subject 218. The position of implantable device 206 in the reference frame of the subject may be given by a vector ^_^^^^^^௧ between point 1002 and a point 1004 in implantable device 206. The depth ^_^^^^^^௧ at which implantable device 206 is implanted in subject 218 may, therefore, by given by the difference between the magnitude of ^_^௨^ and the magnitude of ^_^^^^^^௧:

Attorney Docket No.: 78895-20030.40 [0182] When interrogator 202 is placed on subject 218, a contact area/spacer 228 of interrogator 202 may come into physical contact with subject 218 at a point 1006. A vector ^_^^^௧^^௧ may define the location of point 1006 in the reference frame of the subject. Finally, a vector ^_ூெ^ may define the location of a point 1008 within an IMU sensor (e.g., an accelerometer or a gyroscope) in the reference frame of the subject. [0183] The polar inclination ^_^^^^^^௧ of implantable device 206 in the reference frame of the subject may be the angle between ^_^^^^^^௧ and the ^_^௨^ axis. Similarly, the polar inclination of ^_^^^௧^^௧ of contact area 228 in the reference frame of the subject may be the angle between ^_^^^^^^௧ and the ^_^௨^ axis. [0184] The azimuthal inclination ^_^^^^^^௧ of implantable device 206 in the reference frame of the subject may be the angle between the projection of ^_^^^^^^௧ on the ^_^௨^-^_^௨^ plane and the ^_^௨^ axis. Similarly, the azimuthal inclination ^_^^^௧^^௧ of implantable device 206 in the reference frame of the subject may be the angle between the projection of ^_^^^௧^^௧ on the ^_^௨^-^_^௨^ plane and the ^_^௨^ axis. [0185] FIG.10B shows the reference frame of contact surface 230 and the reference frame of IMU 208. The reference frame of contact area 228 may be defined by axes ^_^^^௧^^௧, ^_^^^௧^^௧, and ^_^^^௧^^௧, which may meet at a point 1004. The reference frame of IMU 208 may be defined by axes ^_ூெ^, ^_ூெ^, and ^_ூெ^. The origin 1008 of the reference frame of IMU 208 may be a location in IMU 208 at which an IMU sensor is located. For example, when the current position of the interrogator is being determined by the computing system, the origin 1008 may be a location of the accelerometer in IMU 208. [0186] A vector ^_{ூெ^ି^^^௧^^௧} may define a location of IMU sensor in the reference frame of contact surface 230. The polar inclination ^_{ூெ^ି^^^௧^^௧} of the IMU sensor in the reference frame of the contact surface may be the angle between ^_{ூெ^ି^^^௧^^௧} and the ^_^^^௧^^௧ axis. The azimuthal inclination ^_{ூெ^ି^^^௧^^௧} of the IMU sensor in the reference frame of the contact surface may be the angle between the projection of ^_{ூெ^ି^^^௧^^௧} on the ^_^^^௧^^௧- ^_^^^௧^^௧ plane and the ^_^^^௧^^௧ axis. [0187] The depth of the ^_^^^^^^௧ , along with the polar inclination ^_^^^^^^௧ and the azimuthal inclination ^_^^^^^^௧ of the implant in the reference frame of the subject, may be known (or estimated with high accuracy) based on how and where implantable device 206 was implanted in subject 218. The angles ^_^^^௧^^௧, ^_^^^௧^^௧, ^_{ூெ^ି^^^௧^^௧}, and ^_{ூெ^ି^^^௧^^௧} at a given sampling time may be estimated using gyroscope data collected by the IMU. Given the location of point 1002, along with the (estimated) values of ^_^^^^^^௧ , ^_^^^^^^௧, ^_^^^^^^௧, Attorney Docket No.: 78895-20030.40 ^_^^^௧^^௧, ^_^^^௧^^௧, ^_{ூெ^ି^^^௧^^௧}, and ^_{ூெ^ି^^^௧^^௧}, the locations of points 1004, 1006, and 1008, and subsequently the position and orientation of the interrogator in the reference frame of the subject, may be determined. In some embodiments, the three-dimensional positions of points 1004, 1006, and 1008 may be determined as follows:

^_^^௨ ൌ ^_^^௨ sin^^_^^௨^ cos^^_^^௨^^ ^_^^௨ ൌ ^_^^௨ sin^^_^^௨^ sin^^_^^௨^^ ^_^^௨ ൌ ^_^^௨ cos^^_^^௨^^ [0188] Based on interrogator hardware information, such as the distance ^_{^^௧^^^^^^௧^^} between the interrogator contact area 228 and IMU 208, information about the interrogator orientation relative to the surface of subject 218 may be determined, for example as follows:

ൌ ^^_^^௨ െ ^_^^^௧^^௧,^_^^௨ െ ^_^^^௧^^௧, ^_^^௨ െ ^_^^^௧^^௧^ [0189] Following the determination of the current position (step 904) and the current orientation (step 910) in method 900, a plurality of error values associated with current position and the current orientation may be determined. A first error value may indicate a difference between the current position of the interrogator and the target contact position (step 908). A second error value may indicate a deviation of the current orientation of the interrogator from a target orientation (step 912). The target contact position and target orientation may together constitute the target contact location. Specifically, the target contact position may be a position on the subject at which the interrogator should be placed to optimize communication with the implantable device, while the target orientation may indicate how the interrogator should be placed at the target contact location. For example, the target contact position may indicate a point on the subject’s eye (or on the subject’s head, chest, abdomen, etc.) and the target orientation may indicate a precise placement type of the contact surface of the interrogator (e.g., normal to the surface of the subject, tilted at a specified angle with respect to the surface of the subject, etc.). The first and second error Attorney Docket No.: 78895-20030.40 values, therefore, may together quantify a difference between a current location of the interrogator and the target contact location. [0190] In some embodiments, error values may be determined using the values indicated in FIGS.10A-10B. For example, a first error value may be a localization indicator that indicates a difference between a contact point between interrogator 202 and the surface of subject 218:

A second error value may be a normality indicator that indicates whether the contact area 228 of the interrogator is held normal to the surface of subject 218. The normality indicator may be obtained using a projection of the interrogator orientation vector ^^_{^^௧^^^^^^௧^^,௫}, ^_{^^௧^^^^^^௧^^,௬}, ^_{^^௧^^^^^^௧^^,௭}^. [0191] The control information may be generated based on these error values. For example, the control information may comprise instructions for adjusting the current position or the current orientation of the interrogator in order to reduce a magnitude of the first error value or a magnitude of the second error value (step 914). Interrogator location data [0192] FIGS.11-13 show various examples of interrogator location data. Specifically, FIGS.11A-D shows plots of a position of an interrogator as it is moved along the surface of a subject’s eye. Such movements may be observed for interrogators used to communicate with intraocular implants, for example implants used to monitor intraocular pressure in subjects with glaucoma. FIG.12 shows plots of raw measurements from an accelerometer (plot 1200) and a gyroscope (plot 1202). FIG.13 shows a reconstruction of the 3D position of an interrogator (plot 1300) as well as the orientation of the interrogator over a period of time (plot 1302). Control information and control maps [0193] The control information generated by the computing system may indicate to an operator of the interrogator one or more ways in which the interrogator should be moved in order to improve communication with the implantable device. As discussed, in some embodiments, the computing system may be configured to control a display, and the control information may include one or more visual indicators configured to show the operator how Attorney Docket No.: 78895-20030.40 the interrogator should be moved in order to improve communication with the implantable device. [0194] An exemplary method 1400 for displaying current interrogator position and orientation relative to a target contact location is shown in FIG.14. For each sampling time at which interrogator location data is collected by the IMU, the computing system may generate control information comprising one or more maps indicating the current position and the current orientation of the interrogator relative to the target contact location (step 1402). The maps may also indicate one or more previous positions or one or more previous orientations of the interrogator. The computing system may then cause the display to display the one or more maps to the operator of the interrogator (step 1404). [0195] FIG.15 shows an example of maps that may be generated by the computing system to show an interrogator operator the current position and current orientation of the interrogator. A first plot 1500 shows 3D position data for an interrogator. A second plot 1502 shows a map of interrogator orientation relative to a target orientation as the interrogator is moved through the positions shown in plot 1500. A third plot 1504 shows a map of interrogator position relative to a target position as the interrogator is moved through the positions shown in plot 1500. Plots such as plot 1502 and 1504 may be generated and displayed to the interrogator operator throughout an interrogation session in order to provide the operator with continuous visual indications of how the interrogator should be moved in order to improve communication with the implantable device. Signal quality evaluation [0196] The interrogator operator may use control information generated by the computing system to move the interrogator toward the target contact location. Once placed at the target contact location, communication of energy or information between the interrogator and the implantable device may commence. In order to ensure that the communication link is, in fact, of a desired quality level, the quality of communication signals received from the implantable device may, at this point, be evaluated by the computing system. [0197] FIG.16 shows an exemplary method 1600 for evaluating the quality level of signals received from the implantable device by the interrogator. After the computing system generates the control information, the interrogator operator may move the interrogator based on the indications contained in the control information (step 1602). Once the interrogator has been moved as indicated, a signal (e.g., ultrasonic waves) may be transmitted from a transducer in the implantable device to a transducer in the interrogator (step 1604). The Attorney Docket No.: 78895-20030.40 computing system may receive information about the signal from the interrogator and may evaluate a quality level of said signal, for example by determining a signal-to-noise ratio (SNR) of the signal. [0198] Precisely tracking the location of the interrogator and evaluating the quality level of communication between the interrogator and the implantable device at identified locations may allow an image of the implantable device to be generated. A method 1700 for generating a two-dimensional image of a cross section of the implantable device is shown in FIG.17. The computing system may generate (step 1702) and display (step 1704) a two-dimensional image of a cross section of the implantable device by determining locations at which the quality level (e.g., the signal-to-noise ratio) of communications received by the interrogator from the implantable device exceeds a threshold quality level (e.g., threshold signal-to-noise ratio). Exemplary 2D images of a cross-section of an implantable device generated by evaluating signal quality levels are shown in FIG.18. Communication optimization method [0199] FIG.19 shows an example of a method 1900 for optimizing communication with an implantable device. Method 1900 may combine several of the previously described methods, for example method 100, method 700, method 900, method 1600, and/or method 1700. Method 1900 may be executed, in whole or in part, by a computing system such as computing system 204 shown in FIG.2. [0200] At the beginning of an interrogation session, interrogator location calibration information may be obtained by moving the interrogator around the surface of the subject to locate the implantable device (step 1902). The implantable device may be located by, for example, detecting and evaluating signals reflected to the interrogator by the implantable device, as described in method 700. If the implant location is identified (e.g., by identifying a peak in reflected signal data), the identified implant location may be identified and stored as an optimal configuration or “reset point” by the computing system (step 1904). If the implant location is not identified, the interrogator may be moved around until a peak is identified. [0201] After a peak is identified, tracking of interrogator movement may begin. For a plurality of sampling times, IMU measurements may be obtained from an IMU in the interrogator (step 1906). The computing system may balance out gravitational effects (step 1908), then estimate IMU and interrogator contact positions (step 1910). The interrogator and sensor/contact polar and azimuthal inclinations may then be estimated (step 1912). Control information may be generated (step 1914) and the interrogator may be moved based on the Attorney Docket No.: 78895-20030.40 control information. If a peak is identified, communication quality may be evaluated to determine if communication has been optimized. If a peak is not identified, the computing system may indicate whether a search for the implant should be repeated. Exemplary Embodiments [0202] Below is an enumerated listing of certain embodiments. In some embodiments, any one or more of the features of any one or more of the embodiments below may be combined with any one or more of the other embodiments, even if the dependencies of the embodiments do not explicitly indicate that the embodiments may be combined in such manner. In some embodiments, any one or more of the features of any one or more of the embodiments below may be combined with any one or more features or aspects otherwise disclosed in this application. [0203] Embodiment 1. A method for improving communication with an implantable device in a subject, the method comprising: determining, by a computing system comprising one or more memories and one or more processors, for a plurality of sampling times, a current position and a current orientation of an interrogator comprising: a transducer configured to communicate with the implantable device, and an inertial measurement unit; wherein the current position and the current orientation of the interrogator are determined relative to a target contact location on the subject using interrogator location data received from the inertial measurement unit, wherein the target contact location is associated with a location of the implantable device in the subject; and generating, by the computing system, control information indicating to a user how to move the interrogator in order to improve communication with the implantable device based on the target contact location, the current position and the current orientation of the interrogator, and the location of the implantable device. [0204] Embodiment 2. The method of embodiment 1, comprising determining the target contact location. [0205] Embodiment 3. The method of claim 2, wherein determining the target contact location comprises: transmitting, using the transducer, a plurality of signals to the subject; receiving, using the transducer, signals of the plurality of signals that are reflected by the implantable device; Attorney Docket No.: 78895-20030.40 identifying, using the computing system, a peak in reflected signal data received from the transducer, wherein the peak corresponds to a point in time at which a location of the interrogator was most closely aligned with the location of the implantable device in the subject. [0206] Embodiment 4. The method of claim 3, comprising removing interference data from the reflected signal data prior to identifying the peak in the reflect signal data. [0207] Embodiment 5. The method of claim 4, wherein the interference data is removed from the reflected signal data using high-pass filtering. [0208] Embodiment 6. The method of any one of claims 2-5, comprising storing the determined target contact location in a memory of the one or more memories of the computing system. [0209] Embodiment 7. The method of any one of claims 1-6, wherein the interrogator location data received from the inertial measurement unit comprises acceleration measurements associated with each of the plurality of sampling times, and wherein the current position of the interrogator at each sampling time is determined based on the acceleration measurement for the sampling time and a position of the interrogator at a previous sampling time. [0210] Embodiment 8. The method of claim 7, comprising removing noise data from the acceleration measurements using the computing system prior to determining the current position of the interrogator. [0211] Embodiment 9. The method of claim 8, wherein the noise data is removed from the acceleration measurements using a polynomial detrending algorithm. [0212] Embodiment 10. The method of claim 8, wherein the noise data is removed from the acceleration measurements using high-pass filtering. [0213] Embodiment 11. The method of any one of claims 1-10, wherein the interrogator location data received from the inertial measurement unit comprises gyroscope measurements associated with each of the plurality of sampling times, and wherein the current orientation of the interrogator at each sampling time is determined based on the gyroscope measurement for the sampling time. [0214] Embodiment 12. The method of any one of claims 1-11, wherein generating the control information comprises determining: a first error value indicating a difference between the current position of the interrogator and the target contact location; and Attorney Docket No.: 78895-20030.40 a second error value indicating a deviation of the current orientation of the interrogator from a target orientation. [0215] Embodiment 13. The method of claim 12, wherein the target orientation depends on the location of the implantable device in the subject. [0216] Embodiment 14. The method of claim 12 or 13, wherein the target orientation is normal to a contact surface on the subject. [0217] Embodiment 15. The method of any one of claims 12-14, wherein the control information comprises instructions for adjusting the current position or the current orientation of the interrogator in order to reduce a magnitude of the first error value or a magnitude of the second error value. [0218] Embodiment 16. The method of any one of claims 1-15, wherein the computing system comprises a display, the method comprising: [0219] generating, by the computing system, for each of the plurality of sampling times, one or more maps indicating the current position and the current orientation of the interrogator relative to the target contact location; and [0220] displaying, by the computing system, the one or more maps. [0221] Embodiment 17. The method of claim 16, wherein the one or more maps for each sampling time indicate one or more positions or one or more orientations of the interrogator at previous sampling times. [0222] Embodiment 18. The method of any one of claims 1-17, comprising: moving the interrogator based on the control information; receiving, by the transducer, a signal transmitted from the implantable device; and evaluating, by the computing system, a quality level of the signal received from the implantable device. [0223] Embodiment 19. The method of any one of claims 1-18, wherein the computing system comprises a display, the method comprising: generating, by the computing system, a two-dimensional image of a cross-section of the implantable device that indicates one or more locations within the cross section where quality levels of a plurality of signals received by the transducer from the implantable device exceed a threshold quality level, and displaying, by the computing system, the two-dimensional image of the cross- section of the implantable device. [0224] Embodiment 20. The method of claim 18 or 19, wherein a quality level of a signal received from the implantable device is a signal-to-noise ratio of the signal. Attorney Docket No.: 78895-20030.40 [0225] Embodiment 21. The method of any one of claims 1-20, comprising iteratively repeating the steps of determining the current position and the current orientation of the interrogator and generating the control information until the control information indicates that the interrogator should not be moved. [0226] Embodiment 22. The method of any one of claims 1-21, comprising receiving, by the transducer, physiological signal data from the implantable device. [0227] Embodiment 23. The method of claim 22, wherein the transducer is an ultrasonic transducer, and the physiological signal data is received from ultrasonic backscatter emitted by the implantable device. [0228] Embodiment 24. The method of claim 22, wherein the transducer is a radio frequency (RF) antenna, and the physiological signal data is received from radio wave backscatter emitted by the implantable device. [0229] Embodiment 25. The method of any one of claims 22-24, wherein the physiological signal data comprise a pressure. [0230] Embodiment 26. The method of claim 25, wherein the pressure is an intraocular pressure. [0231] Embodiment 27. The method of any one of claims 22-26, wherein the physiological signal data comprise a concentration of an analyte. [0232] Embodiment 28. The method of any one of claims 22-27, wherein the physiological signal data comprise a pH. [0233] Embodiment 29. The method of any one of claims 22-28, wherein the physiological signal data comprise a local field potential in a brain or an evoked action potential in a brain. [0234] Embodiment 30. The method of any one of claims 22-29, wherein the physiological signal data comprise an electrophysiological pulse. [0235] Embodiment 31. The method of any one of claims 1-30, comprising transmitting to the implantable device, using the transducer, a powering signal configured to provide energy to the implantable device. [0236] Embodiment 32. The method of claim 31, wherein the transducer is an ultrasonic transducer, and the powering signal comprises ultrasonic waves. [0237] Embodiment 33. The method of claim 32, wherein the transducer is a radio frequency (RF) antenna, and the powering signal comprises radio waves. [0238] Embodiment 34. A system for improving communication with an implantable device in a subject, the system comprising: Attorney Docket No.: 78895-20030.40 an interrogator comprising: a transducer configured to communicate with the implantable device; and an inertial measurement unit; and a computing system comprising one or more memories and one or more processors communicatively coupled to the interrogator and configured to: determine, for a plurality of sampling times, a current position and a current orientation of the interrogator relative to a target contact location on the subject using interrogator location data received from the inertial measurement unit, wherein the target contact location is associated with a location of the implantable device in the subject; and generate control information indicating to a user how to move the interrogator for improving communication with the implantable device based on the target contact location, the current position of the interrogator, the current orientation of the interrogator, and the location of the implantable device. [0239] Embodiment 35. The system of claim 34, wherein the computing system is configured to determine the target contact location. [0240] Embodiment 36. The system of claim 35, wherein the transducer is configured to receive signals reflected by the implantable device, and wherein determining the target contact location comprises: identifying, using the computing system, a peak in reflected signal data received from the transducer, wherein the peak corresponds to a point in time at which a location of the interrogator was most closely aligned with the location of the implantable device in the subject. [0241] Embodiment 37. The system of claim 36, wherein interference data is removed from the reflected signal data prior to identifying the peak in the reflect signal data. [0242] Embodiment 38. The system of claim 37, wherein the interference data is removed from the reflected signal data using high-pass filtering. [0243] Embodiment 39. The system of any one of claims 34-38, wherein the computing system is configured to store the determined target contact location in a memory of the one or more memories. [0244] Embodiment 40. The system of any one of claims 34-39, wherein the interrogator location data received from the inertial measurement unit comprises acceleration measurements associated with each of the plurality of sampling times, and wherein the current position of the interrogator at each sampling time is determined based on the Attorney Docket No.: 78895-20030.40 acceleration measurement for the sampling time and a position of the interrogator at a previous sampling time. [0245] Embodiment 41. The system of claim 40, wherein noise data is removed from the acceleration measurements using the computing system prior to determining the current position of the interrogator. [0246] Embodiment 42. The system of claim 41, wherein the noise data is removed from the acceleration measurements using a polynomial detrending algorithm. [0247] Embodiment 43. The method of claim 41, wherein the noise data is removed from the acceleration measurements using high-pass filtering. [0248] Embodiment 44. The system of any one of claims 34-43, wherein the interrogator location data received from the inertial measurement unit comprises gyroscope measurements associated with each of the plurality of sampling times, and wherein the current orientation of the interrogator at each sampling time is determined based on the gyroscope measurement for the sampling time. [0249] Embodiment 45. The system of any one of claims 34-44, wherein generating the control information comprises determining: a first error value indicating a difference between the current position of the interrogator and the target contact location; and a second error value indicating a deviation of the current orientation of the interrogator from a target orientation. [0250] Embodiment 46. The system of claim 45, wherein the target orientation depends on the location of the implantable device in the subject. [0251] Embodiment 47. The system of claim 45 or 46, wherein the target orientation is normal to a contact surface on the subject. [0252] Embodiment 48. The system of any one of claims 45-47, wherein the control information comprises instructions for adjusting the current position or the current orientation of the interrogator in order to reduce a magnitude of the first error value or a magnitude of the second error value. [0253] Embodiment 49. The system of any one of claims 34-48, wherein the computing system comprises a display, wherein the computing system is configured to: generate, for each of the plurality of sampling times, one or more maps indicating the current position and the current orientation of the interrogator relative to the target contact location; and display the one or more maps on the display. Attorney Docket No.: 78895-20030.40 [0254] Embodiment 50. The system of claim 49, wherein the one or more maps for each sampling time indicate one or more positions or one or more orientations of the interrogator at previous sampling times. [0255] Embodiment 51. The system of any one of claims 34-50, wherein the computing system comprises a display, wherein the computing system is configured to: generate a two-dimensional image of a cross-section of the implantable device that indicates one or more locations within the cross section where quality levels of a plurality of signals received from the implantable device by the transducer exceed a threshold quality level, and display the two-dimensional image of the cross-section of the implantable device on the display. [0256] Embodiment 52. The system of claim 50 or 51, wherein a quality level of a signal received from the implantable device is a signal-to-noise ratio of the signal. [0257] Embodiment 53. The system of any one of claims 34-52 wherein the transducer is an ultrasonic transducer. [0258] Embodiment 54. The system of any one of claims 34-52, wherein the transducer is a radio frequency (RF) antenna. [0259] Embodiment 55. The system of any one of claims 34-54, wherein the transducer is configured to receive physiological signal data from the implantable device. [0260] Embodiment 56. The system of any one of claims 34-55, wherein the transducer is configured to transmit, to the implantable device, a powering signal configured to provide energy to the implantable device. [0261] Embodiment 57. The system of any one of claims 34-56, wherein the implantable device is fully implanted in the subject. [0262] Embodiment 58. The system of any one of claims 34-57, wherein the implantable device is implanted in an eye. [0263] Embodiment 59. The system of any one of claims 34-57, wherein the implantable device is implanted on or in nervous tissue. [0264] Embodiment 60. The system of claim 59, wherein the nervous tissue is brain tissue. [0265] Embodiment 61. The system of claim 59, wherein the nervous tissue is a peripheral nerve. [0266] Embodiment 62. The system of claim 61, wherein the peripheral nerve is a splenic nerve. Attorney Docket No.: 78895-20030.40 [0267] Embodiment 63. The system of any one of claims 34-57, wherein the implantable device is implanted on or in organ tissue. [0268] Embodiment 64. The system of claim 63, wherein the organ is a bladder. [0269] Embodiment 65. The system of claim 63, wherein the organ is a heart. [0270] Embodiment 66. The system of claim 63, wherein the organ is a muscle. [0271] Embodiment 67. The system of claim 63, wherein the organ is a stomach. [0272] Embodiment 68. A non-transitory computer readable storage medium storing instruction for improving communication with an implantable device in a subject, wherein, when executed by one or more processors of a computing system, the instructions are configured to cause the computing system to: determine one or more memories and one or more processors, for a plurality of sampling times, a current position and a current orientation of an interrogator comprising: a transducer configured to communicate with the implantable device, and an inertial measurement unit; wherein the current position and the current orientation of the interrogator are determined relative to a target contact location on the subject using interrogator location data received from the inertial measurement unit, wherein the target contact location is associated with a location of the implantable device in the subject; and generate control information indicating to a user how to move the interrogator in order to improve communication with the implantable device based on the target contact location, the current position and the current orientation of the interrogator, and the location of the implantable device. [0273] Embodiment 69. The non-transitory computer readable storage medium of claim 68, wherein the instructions are configured to cause the computing system to determine the target contact location. [0274] Embodiment 70. The non-transitory computer readable storage medium of claim 69, wherein the transducer is configured to receive signals reflected by the implantable device, and wherein determining the target contact location comprises: identifying, using the computing system, a peak in reflected signal data received from the transducer, wherein the peak corresponds to a point in time at which a location of the interrogator was most closely aligned with the location of the implantable device in the subject. Attorney Docket No.: 78895-20030.40 [0275] Embodiment 71. The non-transitory computer readable storage medium of claim 70, wherein interference data is removed from the reflected signal data prior to identifying the peak in the reflect signal data. [0276] Embodiment 72. The non-transitory computer readable storage medium of claim 70, wherein the interference data is removed from the reflected signal data using high-pass filtering. [0277] Embodiment 73. The non-transitory computer readable storage medium of any one of claims 69-72, wherein the computing system comprises one or more memories, and wherein the instructions are configured to cause the computing system to store the determined target contact location in a memory of one or more memories. [0278] Embodiment 74. The non-transitory computer readable storage medium of any one of claims 68-73, wherein the interrogator location data received from the inertial measurement unit comprises acceleration measurements associated with each of the plurality of sampling times, and wherein the current position of the interrogator at each sampling time is determined based on the acceleration measurement for the sampling time and a position of the interrogator at a previous sampling time. [0279] Embodiment 75. The non-transitory computer readable storage medium of claim 74, wherein noise data is removed from the acceleration measurements prior to determining the current position of the interrogator. [0280] Embodiment 76. The non-transitory computer readable storage medium of claim 75, wherein the noise data is removed from the acceleration measurements using a polynomial detrending algorithm. [0281] Embodiment 77. The non-transitory computer readable storage medium of claim 75, wherein the noise data is removed from the acceleration measurements using high-pass filtering. [0282] Embodiment 78. The non-transitory computer readable storage medium of any one of claims 68-77, wherein the interrogator location data received from the inertial measurement unit comprises gyroscope measurements associated with each of the plurality of sampling times, and wherein the current orientation of the interrogator at each sampling time is determined based on the gyroscope measurement for the sampling time. [0283] Embodiment 79. The non-transitory computer readable storage medium of any one of claims 68-78, wherein generating the control information comprises determining: a first error value indicating a difference between the current position of the interrogator and the target contact location; and Attorney Docket No.: 78895-20030.40 a second error value indicating a deviation of the current orientation of the interrogator from a target orientation. [0284] Embodiment 80. The non-transitory computer readable storage medium of claim 79, wherein the target orientation depends on the location of the implantable device in the subject. [0285] Embodiment 81. The non-transitory computer readable storage medium of claim 79 or 80, wherein the target orientation is normal to a contact surface on the subject. [0286] Embodiment 82. The non-transitory computer readable storage medium of any one of claims 79-81, wherein the control information comprises instructions for adjusting the current position or the current orientation of the interrogator in order to reduce a magnitude of the first error value or a magnitude of the second error value. [0287] Embodiment 83. The non-transitory computer readable storage medium of any one of claims 68-82, wherein the computing system comprises a display, wherein the instructions are configured to cause the computing system to: generate, for each of the plurality of sampling times, one or more maps indicating the current position and the current orientation of the interrogator relative to the target contact location; and display the one or more maps on the display. [0288] Embodiment 84. The non-transitory computer readable storage medium of claim 83, wherein the one or more maps for each sampling time indicate one or more positions or one or more orientations of the interrogator at previous sampling times. [0289] Embodiment 85. The non-transitory computer readable storage medium of any one of claims 68-84, wherein the instructions are configured to cause the computing system to evaluate a quality level of a signal received by the transducer from the implantable device. [0290] Embodiment 86. The non-transitory computer readable storage medium of any one of claims 68-85, wherein the computing system comprises a display, wherein the instructions are configured to cause the computing system to: generate a two-dimensional image of a cross-section of the implantable device that indicates one or more locations within the cross section where quality levels of a plurality of signals received by the transducer from the implantable device exceed a threshold quality level, and display the two-dimensional image of the cross-section of the implantable device on the display. Attorney Docket No.: 78895-20030.40 [0291] Embodiment 87. The non-transitory computer readable storage medium of claim 85 or 86, wherein a quality level of a signal received from the implantable device is a signal- to-noise ratio of the signal. [0292] Embodiment 88. The non-transitory computer readable storage medium of any one of claims 68-87, wherein the implantable device is fully implanted in the subject. [0293] Embodiment 89. The non-transitory computer readable storage medium of any one of claims 68-88, wherein the implantable device is implanted in an eye. [0294] Embodiment 90. The non-transitory computer readable storage medium of any one of claims 68-88, wherein the implantable device is implanted on or in nervous tissue. [0295] Embodiment 91. The non-transitory computer readable storage medium of claim 90, wherein the nervous tissue is brain tissue. [0296] Embodiment 92. The non-transitory computer readable storage medium of claim 90, wherein the nervous tissue is a peripheral nerve. [0297] Embodiment 93. The non-transitory computer readable storage medium of claim 90, wherein the peripheral nerve is a splenic nerve. [0298] Embodiment 94. The non-transitory computer readable storage medium of any one of claims 68-88, wherein the implantable device is implanted on or in organ tissue. [0299] Embodiment 95. The non-transitory computer readable storage medium of claim 94, wherein the organ is a bladder. [0300] Embodiment 96. The non-transitory computer readable storage medium of claim 94, wherein the organ is a heart. [0301] Embodiment 97. The non-transitory computer readable storage medium of claim 94, wherein the organ is a muscle. [0302] Embodiment 98. The non-transitory computer readable storage medium of claim 96, wherein the organ is a stomach. [0303] The foregoing description, for the purpose of explanation, has been described with reference to specific embodiments and/or examples. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the techniques and their practical applications. Others skilled in the art are thereby enabled to best utilize the techniques and various embodiments with various modifications as are suited to the particular use contemplated. Attorney Docket No.: 78895-20030.40 [0304] Although the disclosure and examples have been fully described with reference to the accompanying figures, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosure and examples as defined by the claims. Finally, the entire disclosure of the patents and publications referred to in this application are hereby incorporated herein by reference. [0305] Any of the systems, methods, techniques, and/or features disclosed herein may be combined, in whole or in part, with any other systems, methods, techniques, and/or features disclosed herein.

Claims

Attorney Docket No.: 78895-20030.40 CLAIMS 1. A method for improving communication with an implantable device in a subject, the method comprising: determining, by a computing system comprising one or more memories and one or more processors, for a plurality of sampling times, a current position and a current orientation of an interrogator comprising: a transducer configured to communicate with the implantable device, and an inertial measurement unit; wherein the current position and the current orientation of the interrogator are determined relative to a target contact location on the subject using interrogator location data received from the inertial measurement unit, wherein the target contact location is associated with a location of the implantable device in the subject; and generating, by the computing system, control information indicating to a user how to move the interrogator in order to improve communication with the implantable device based on the target contact location, the current position and the current orientation of the interrogator, and the location of the implantable device. 2. The method of claim 1, comprising determining the target contact location. 3. The method of claim 2, wherein determining the target contact location comprises: transmitting, using the transducer, a plurality of signals to the subject; receiving, using the transducer, signals of the plurality of signals that are reflected by the implantable device; identifying, using the computing system, a peak in reflected signal data received from the transducer, wherein the peak corresponds to a point in time at which a location of the interrogator was most closely aligned with the location of the implantable device in the subject. 4. The method of claim 3, comprising removing interference data from the reflected signal data prior to identifying the peak in the reflect signal data. 5. The method of claim 4, wherein the interference data is removed from the reflected signal data using high-pass filtering. Attorney Docket No.: 78895-20030.40 6. The method of any one of claims 1-5, wherein the interrogator location data received from the inertial measurement unit comprises acceleration measurements associated with each of the plurality of sampling times, and wherein the current position of the interrogator at each sampling time is determined based on the acceleration measurement for the sampling time and a position of the interrogator at a previous sampling time. 7. The method of claim 6, comprising removing noise data from the acceleration measurements using the computing system prior to determining the current position of the interrogator. 8. The method of claim 7, wherein the noise data is removed from the acceleration measurements using a polynomial detrending algorithm. 9. The method of claim 7, wherein the noise data is removed from the acceleration measurements using high-pass filtering. 10. The method of any one of claims 1-9, wherein the interrogator location data received from the inertial measurement unit comprises gyroscope measurements associated with each of the plurality of sampling times, and wherein the current orientation of the interrogator at each sampling time is determined based on the gyroscope measurement for the sampling time. 11. The method of any one of claims 1-10, wherein generating the control information comprises determining: a first error value indicating a difference between the current position of the interrogator and the target contact location; and a second error value indicating a deviation of the current orientation of the interrogator from a target orientation. 12. The method of claim 11, wherein the target orientation depends on the location of the implantable device in the subject. Attorney Docket No.: 78895-20030.40 13. The method of claim 11 or 12, wherein the target orientation is normal to a contact surface on the subject. 14. The method of any one of claims 11-13, wherein the control information comprises instructions for adjusting the current position or the current orientation of the interrogator in order to reduce a magnitude of the first error value or a magnitude of the second error value. 15. The method of any one of claims 1-14, wherein the computing system comprises a display, the method comprising: generating, by the computing system, for each of the plurality of sampling times, one or more maps indicating the current position and the current orientation of the interrogator relative to the target contact location; and displaying, by the computing system, the one or more maps. 16. The method of claim 15, wherein the one or more maps for each sampling time indicate one or more positions or one or more orientations of the interrogator at previous sampling times. 17. The method of any one of claims 1-16, comprising: moving the interrogator based on the control information; receiving, by the transducer, a signal transmitted from the implantable device; and evaluating, by the computing system, a quality level of the signal received from the implantable device. 18. The method of any one of claims 1-17, wherein the computing system comprises a display, the method comprising: generating, by the computing system, a two-dimensional image of a cross-section of the implantable device that indicates one or more locations within the cross section where quality levels of a plurality of signals received by the transducer from the implantable device exceed a threshold quality level, and displaying, by the computing system, the two-dimensional image of the cross-section of the implantable device. Attorney Docket No.: 78895-20030.40 19. The method of claim 17 or 18, wherein a quality level of a signal received from the implantable device is a signal-to-noise ratio of the signal. 20. The method of any one of claims 1-19, comprising iteratively repeating the steps of determining the current position and the current orientation of the interrogator and generating the control information until the control information indicates that the interrogator should not be moved. 21. A system for improving communication with an implantable device in a subject, the system comprising: an interrogator comprising: a transducer configured to communicate with the implantable device; and an inertial measurement unit; and a computing system comprising one or more memories and one or more processors communicatively coupled to the interrogator and configured to: determine, for a plurality of sampling times, a current position and a current orientation of the interrogator relative to a target contact location on the subject using interrogator location data received from the inertial measurement unit, wherein the target contact location is associated with a location of the implantable device in the subject; and generate control information indicating to a user how to move the interrogator for improving communication with the implantable device based on the target contact location, the current position of the interrogator, the current orientation of the interrogator, and the location of the implantable device. 22. The system of claim 21, wherein the computing system is configured to determine the target contact location. 23. The system of claim 22, wherein the transducer is configured to receive signals reflected by the implantable device, and wherein determining the target contact location comprises: identifying, using the computing system, a peak in reflected signal data received from the transducer, wherein the peak corresponds to a point in time at which a location of the interrogator was most closely aligned with the location of the implantable device in the subject. Attorney Docket No.: 78895-20030.40 24. The system of claim 23, wherein interference data is removed from the reflected signal data prior to identifying the peak in the reflect signal data. 25. The system of any one of claims 21-24, wherein the interrogator location data received from the inertial measurement unit comprises acceleration measurements associated with each of the plurality of sampling times, and wherein the current position of the interrogator at each sampling time is determined based on the acceleration measurement for the sampling time and a position of the interrogator at a previous sampling time. 26. The system of claim 25, wherein noise data is removed from the acceleration measurements using the computing system prior to determining the current position of the interrogator. 27. The system of any one of claims 21-26, wherein the interrogator location data received from the inertial measurement unit comprises gyroscope measurements associated with each of the plurality of sampling times, and wherein the current orientation of the interrogator at each sampling time is determined based on the gyroscope measurement for the sampling time. 28. The system of any one of claims 21-27, wherein generating the control information comprises determining: a first error value indicating a difference between the current position of the interrogator and the target contact location; and a second error value indicating a deviation of the current orientation of the interrogator from a target orientation. 29. The system of claim 28, wherein the control information comprises instructions for adjusting the current position or the current orientation of the interrogator in order to reduce a magnitude of the first error value or a magnitude of the second error value. 30. The system of any one of claims 21-29, wherein the computing system comprises a display, wherein the computing system is configured to: Attorney Docket No.: 78895-20030.40 generate, for each of the plurality of sampling times, one or more maps indicating the current position and the current orientation of the interrogator relative to the target contact location; and display the one or more maps on the display. 31. The system of any one of claims 21-30, wherein the computing system comprises a display, wherein the computing system is configured to: generate a two-dimensional image of a cross-section of the implantable device that indicates one or more locations within the cross section where quality levels of a plurality of signals received from the implantable device by the transducer exceed a threshold quality level, and display the two-dimensional image of the cross-section of the implantable device on the display. 32. A non-transitory computer readable storage medium storing instruction for improving communication with an implantable device in a subject, wherein, when executed by one or more processors of a computing system, the instructions are configured to cause the computing system to: determine one or more memories and one or more processors, for a plurality of sampling times, a current position and a current orientation of an interrogator comprising: a transducer configured to communicate with the implantable device, and an inertial measurement unit; wherein the current position and the current orientation of the interrogator are determined relative to a target contact location on the subject using interrogator location data received from the inertial measurement unit, wherein the target contact location is associated with a location of the implantable device in the subject; and generate control information indicating to a user how to move the interrogator in order to improve communication with the implantable device based on the target contact location, the current position and the current orientation of the interrogator, and the location of the implantable device. 33. The non-transitory computer readable storage medium of claim 32, wherein the instructions are configured to cause the computing system to determine the target contact location. Attorney Docket No.: 78895-20030.40 34. The non-transitory computer readable storage medium of claim 33, wherein the transducer is configured to receive signals reflected by the implantable device, and wherein determining the target contact location comprises: identifying, using the computing system, a peak in reflected signal data received from the transducer, wherein the peak corresponds to a point in time at which a location of the interrogator was most closely aligned with the location of the implantable device in the subject. 35. The non-transitory computer readable storage medium of any one of claims 32-34, wherein the interrogator location data received from the inertial measurement unit comprises acceleration measurements associated with each of the plurality of sampling times, and wherein the current position of the interrogator at each sampling time is determined based on the acceleration measurement for the sampling time and a position of the interrogator at a previous sampling time. 36. The non-transitory computer readable storage medium of any one of claims 32-35, wherein the interrogator location data received from the inertial measurement unit comprises gyroscope measurements associated with each of the plurality of sampling times, and wherein the current orientation of the interrogator at each sampling time is determined based on the gyroscope measurement for the sampling time. 37. The non-transitory computer readable storage medium of any one of claims 32-36, wherein generating the control information comprises determining: a first error value indicating a difference between the current position of the interrogator and the target contact location; and a second error value indicating a deviation of the current orientation of the interrogator from a target orientation. 38. The non-transitory computer readable storage medium of claim 37, wherein the control information comprises instructions for adjusting the current position or the current orientation of the interrogator in order to reduce a magnitude of the first error value or a magnitude of the second error value. Attorney Docket No.: 78895-20030.40 39. The non-transitory computer readable storage medium of any one of claims 32-38, wherein the computing system comprises a display, wherein the instructions are configured to cause the computing system to: generate, for each of the plurality of sampling times, one or more maps indicating the current position and the current orientation of the interrogator relative to the target contact location; and display the one or more maps on the display. 40. The non-transitory computer readable storage medium of any one of claims 32-39, wherein the computing system comprises a display, wherein the instructions are configured to cause the computing system to: generate a two-dimensional image of a cross-section of the implantable device that indicates one or more locations within the cross section where quality levels of a plurality of signals received by the transducer from the implantable device exceed a threshold quality level, and display the two-dimensional image of the cross-section of the implantable device on the display.