Abstract:
In one embodiment, an ICD is provided which includes a case having a connector block and a conductor post integrally formed with the connector block and extending through a dielectric feedthrough extending through the case. A capacitor is located within the dielectric. In some embodiments, the conductor post is a straight conductor post extending from a side of the connector block facing the feedthrough directly toward the feedthrough. The conductor post and the connector block may be formed of the same material, such as titanium. In some embodiments, a plurality of straight conductor posts and connector blocks are integrally formed. In some embodiments, the dielectric may be a single matrix dielectric, such that each of the straight conductor posts extends through the single matrix dielectric. In other embodiments, each of the straight conductor posts extends through a separate dielectric portion.

Description:
BACKGROUND 
       [0001]      FIG. 1  illustrates an ICD or implantable cardiac device  10  in electrical communication with a patient&#39;s heart  12  by way of three leads,  20 ,  24 , and  30 , suitable for delivering multi-chamber stimulation and shock therapy.  FIG. 2  shows a portion of a conventional feedthrough assembly  205  of the implantable cardiac device  10 . The feedthrough assembly  205  has platinum iridium wires  225  which are welded to titanium connector blocks  235 . The platinum wires  225  extend through case  40  of the implantable cardiac device  10  via feedthrough ceramic  215 . The platinum iridium wires  225  are bent to position the connector blocks  235 . This requires manipulation of the wires  225  to form them, and multiple weld/brazing joints (not shown) to secure the wires  225  to their respective ceramic substrates  215  and to secure the flange portions  245  of the substrate  215  to the case  40 . 
         [0002]    The manufacturing process is labor intensive. It often requires rework of wires  225 , as wires  225  can move in the process of molding or casting of the header (epoxy header not shown). Moreover, the platinum iridium is very expensive. Thus, this results in an expensive feedthrough assembly  205  due to the use of platinum wires  225 , and due to a cumbersome and variable process required to form and insert the shaped wires  225 . 
         [0003]    Furthermore, sometimes an error in wire  225  formation can result in the high voltage wires  225  getting too close to the case  40 . Since typical high voltage defibrillation therapy is about 800V, positioning the wires  225  too close to the case  40  could cause shorting during delivery of defibrillation therapy, leading to catastrophic failure. 
         [0004]    What is needed is a significant reduction in costs without sacrificing reliability. In addition, what is needed is a way to reduce manufacturing complexity and at the same time increase the reliability of the header assembly. 
       SUMMARY 
       [0005]    In one implementation, an implantable cardiac device is provided which includes a case having a connector block and a conductor post integrally formed with the conductor post extending through a dielectric feedthrough which extends through the case. A capacitor is located within the dielectric. 
         [0006]    In some embodiments, the conductor post is a straight conductor post extending from a side of the connector block facing the feedthrough directly toward the feedthrough. The conductor post and the connector block may be formed of the same material, such as titanium. Other suitable materials include MP35N, stainless steel, palladium, platinum-iridium, and the like. 
         [0007]    In some embodiments, a plurality of straight conductor posts and connector blocks are integrally formed. In some embodiments, the dielectric may be a single matrix dielectric, such that each of the straight conductor posts extends through the single matrix dielectric. In other embodiments, each of the straight conductor posts extends through a separate dielectric portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Further features and advantages of the invention may be more readily understood by reference to the following description taken in conjunction with the accompanying drawings, in which: 
           [0009]      FIG. 1  illustrates a prior art implantable cardiac device in electrical communication with a patient&#39;s heart. 
           [0010]      FIG. 2  shows a portion of a conventional feedthrough header assembly of the implantable cardiac device. 
           [0011]      FIG. 3  illustrates a simplified block diagram of a prior art stimulation device. 
           [0012]      FIG. 4  shows a portion of a feedthrough header assembly of an implantable cardiac device in accordance with one embodiment of the present invention. 
           [0013]      FIG. 5  shows a perspective view of a molded header. 
           [0014]      FIG. 6  shows a perspective view of an implantable cardiac device with an attached header assembly. 
           [0015]      FIG. 7  shows a perspective view of a possible embodiment of the feedthrough assembly having individual dielectric rings for each of the conductor posts. 
       
    
    
     DESCRIPTION 
       [0016]    The following description includes the best mode presently contemplated for practicing the described implementations. This description is not to be taken in a limiting sense, but rather is made merely for the purpose of describing the general principles of the implementations. The scope of the described implementations should be ascertained with reference to the issued claims. In the description that follows, like numerals or reference designators will be used to reference like parts or elements throughout. 
       Overview of Implantable Cardiac Stimulation Device 
       [0017]      FIG. 1  illustrates an implantable cardiac stimulation device  10  in electrical communication with a patient&#39;s heart  12  by way of three leads,  20 ,  24  and  30 , suitable for delivering multi-chamber stimulation and shock therapy. To sense atrial cardiac signals and to provide right atrial chamber stimulation therapy, the stimulation device  10  is coupled to an implantable right atrial lead  20  having at least an atrial tip electrode  22 , which typically is implanted in the patient&#39;s right atrial appendage, and an atrial ring electrode  23 . To sense left atrial and ventricular cardiac signals and to provide left chamber pacing therapy, the stimulation device  10  is coupled to a “coronary sinus” lead  24  designed for placement in the “coronary sinus region” via the coronary sinus or for positioning a distal electrode adjacent to the left ventricle and/or additional electrode(s) adjacent to the left atrium. As used herein, the phrase “coronary sinus region” refers to the vasculature of the left ventricle, including any portion of the coronary sinus, great cardiac vein, left marginal vein, left posterior ventricular vein, middle cardiac vein, and/or small cardiac vein or any other cardiac vein accessible by the coronary sinus. Accordingly, in some embodiments, an exemplary coronary sinus lead  24  is designed to receive atrial and ventricular cardiac signals and to deliver left ventricular pacing therapy using at least a left ventricular tip electrode  26 , left atrial pacing therapy using at least a left atrial tip electrode  27 , and shocking therapy using at least a left atrial coil electrode  28 . 
         [0018]    The stimulation device  10  is also shown in electrical communication with the patient&#39;s heart  12  by way of an implantable right ventricular lead  30  having, in this embodiment, a right ventricular tip electrode  32 , a right ventricular ring electrode  34 , a right ventricular (RV) coil electrode  36 , and a superior vena cava (SVC) coil electrode  38 . Typically, the right ventricular lead  30  is transvenously inserted into the heart  12  so as to place the right ventricular tip electrode  32  in the right ventricular apex so that the right ventricular coil electrode  36  will be positioned in the right ventricle and the SVC coil electrode  38  will be positioned in the superior vena cava. Accordingly, the right ventricular lead  30  is capable of receiving cardiac signals, and delivering stimulation in the form of pacing and shock therapy to the right ventricle. 
         [0019]      FIG. 3  illustrates a simplified block diagram of the stimulation device  10 . The stimulation device  10  is capable of treating both fast and slow arrhythmias with stimulation therapy, including cardioversion, defibrillation, and pacing stimulation. While a particular stimulation device  10  is shown, this is for illustration purposes only, and one of skill in the art could readily duplicate, eliminate or disable the appropriate circuitry in any desired combination to provide a device capable of treating the appropriate chamber(s) with cardioversion, defibrillation and pacing stimulation. 
         [0020]    The stimulation device  10  includes a case  40 . The case  40  for the stimulation device  10 , shown schematically in  FIG. 3 , is often referred to as the “housing”, “can”, or “case electrode” and may be programmably selected to act as the return electrode for all “unipolar” modes. The case  40  may further be used as a return electrode individually or in combination with one or more of the coil electrodes,  28 ,  36  and  38 , for shocking purposes. The case  40  further includes a connector (not shown) having a plurality of terminals,  42 ,  43 ,  44 ,  46 ,  48 ,  52 ,  54 ,  56 , and  58  (shown schematically and, for convenience, the names of the electrodes to which they are connected are shown next to the terminals). As such, to achieve right atrial sensing and pacing, the connector includes at least a right atrial tip terminal (A R  TIP)  42  adapted for connection to the atrial tip electrode  22  and a right atrial ring (A R  RING) terminal  43  adapted for connection to right atrial ring electrode  23 . To achieve left chamber sensing, pacing and shocking, the connector includes at least a left ventricular tip terminal (V L  TIP)  44 , a left atrial ring terminal (A L  RING)  46 , and a left atrial shocking terminal (A L  COIL)  48 , which are adapted for connection to the left ventricular tip electrode  26 , the left atrial tip electrode  27 , and the left atrial coil electrode  28 , respectively. To support right chamber sensing, pacing and shocking, the connector further includes a right ventricular tip terminal (V R  TIP)  52 , a right ventricular ring terminal (V R  RING)  54 , a right ventricular shocking terminal (RV COIL)  56 , and an SVC shocking terminal (SVC COIL)  58 , which are adapted for connection to the right ventricular tip electrode  32 , the right ventricular ring electrode  34 , the right ventricular coil electrode  36 , and the SVC coil electrode  38 , respectively. 
         [0021]    At the core of the stimulation device  10  is a programmable microcontroller  60 , which controls the various modes of stimulation therapy. As is well known in the art, the microcontroller  60  (also referred to herein as a control unit) typically includes a microprocessor, or equivalent control circuitry, designed specifically for controlling the delivery of stimulation therapy and may further include RAM or ROM memory, logic and timing circuitry, state machine circuitry, and I/O circuitry. Typically, the microcontroller  60  includes the ability to process or monitor input signals (data) as controlled by a program code stored in a designated block of memory. The details of the design and operation of the microcontroller  60  are not critical to the invention. Rather, any suitable microcontroller  60  may be used that carries out the functions described herein. The use of microprocessor-based control circuits for performing timing and data analysis functions are well known in the art. 
         [0022]    As shown in  FIG. 3 , an atrial pulse generator  70  and a ventricular pulse generator (Vtr. Pulse Generator)  72  generate pacing stimulation pulses for delivery by the right atrial lead  20 , the right ventricular lead  30 , and/or the coronary sinus lead  24  via an electrode configuration switch  74 . It is understood that in order to provide stimulation therapy in each of the four chambers of the heart, the atrial and ventricular pulse generators,  70  and  72 , may include dedicated, independent pulse generators, multiplexed pulse generators, or shared pulse generators. The pulse generators,  70  and  72 , are controlled by the microcontroller  60  via appropriate control signals,  76  and  78 , respectively, to trigger or inhibit the stimulation pulses. 
         [0023]    The microcontroller  60  further includes a timing control circuit  79  which is used to control the timing of such stimulation pulses (e.g., pacing rate, atrio-ventricular (AV) delay, atrial interconduction (A-A) delay, or ventricular interconduction (V-V) delay, etc.) as well as to keep track of the timing of refractory periods, blanking intervals, noise detection windows, evoked response windows, alert intervals, marker channel timing, etc., which is well known in the art. Switch  74  includes a plurality of switches for connecting the desired electrodes to the appropriate I/O circuits, thereby providing complete electrode programmability. Accordingly, the switch  74 , in response to a control signal  80  from the microcontroller  60 , determines the polarity of the stimulation pulses (e.g., unipolar, bipolar, combipolar, etc.) by selectively closing the appropriate combination of switches (not shown) as is known in the art. 
         [0024]    In one embodiment, the stimulation device  10  may include an atrial sensing circuit (Atr. Sense)  82  and a ventricular sensing circuit (Vtr. Sense)  84 . The atrial sensing circuit  82  and ventricular sensing circuit  84  may also be selectively coupled to the right atrial lead  20 , coronary sinus lead  24 , and the right ventricular lead  30 , through the switch  74  for detecting the presence of cardiac activity in each of the four chambers of the heart. Accordingly, the atrial sensing circuit  82  and ventricular sensing circuit  84  may include dedicated sense amplifiers, multiplexed amplifiers, or shared amplifiers. The switch  74  determines the “sensing polarity” of the cardiac signal by selectively closing the appropriate switches, as is also known in the art. In this way, the clinician may program the sensing polarity independent of the stimulation polarity. Each sensing circuit,  82  and  84 , may employ one or more low power, precision amplifiers with programmable gain and/or automatic gain control, bandpass filtering, and a threshold detection circuit, as known in the art, to selectively sense the cardiac signal of interest. The bandpass filtering may include a bandpass filter that passes frequencies between 10 and 70 Hertz (Hz) and rejects frequencies below 10 Hz or above 70 Hz. The automatic gain control enables the stimulation device  10  to deal effectively with the difficult problem of sensing the low amplitude signal characteristics of atrial or ventricular fibrillation. The outputs of the atrial and ventricular sensing circuits  82  and  84  are connected to the microcontroller  60  which, in turn, is able to trigger or inhibit the atrial and ventricular pulse generators,  70  and  72 , respectively, in a demand fashion in response to the absence or presence of cardiac activity in the appropriate chambers of the heart. 
         [0025]    For arrhythmia detection, the stimulation device  10  may utilize the atrial and ventricular sensing circuits  82  and  84  to sense cardiac signals to determine whether a rhythm is physiologic or pathologic. The timing intervals between sensed events (e.g., P-waves, R-waves, and depolarization events associated with fibrillation which are sometimes referred to as “F-waves” or “Fib-waves”) are then classified by the microcontroller  60  by comparing them to a predefined rate zone limit (i.e., bradycardia, normal, low rate VT, high rate VT, and fibrillation rate zones) and various other characteristics (e.g., sudden onset, stability, physiologic sensors, and morphology, etc.) in order to determine the type of remedial therapy that is needed (e.g., bradycardia pacing, antitachycardia pacing, cardioversion shocks or defibrillation shocks, collectively referred to as “tiered therapy”). Similar capabilities would exist on the atrial channel with respect to tachycardias occurring in the atrium. These would be atrial tachycardias (AT), more rapid atrial tachycardias (Atrial Flutter) and atrial fibrillation (AF). 
         [0026]    In another embodiment, the stimulation device  10  may include an analog-to-digital (A/D) data acquisition circuit  90 . The data acquisition circuit  90  is configured to acquire an intracardiac signal, convert the raw analog data of the intracardiac signal into a digital signal, and store the digital signals for later processing and/or telemetric transmission to an external device  102 . The data acquisition circuit  90  is coupled to the right atrial lead  20 , the coronary sinus lead  24 , and the right ventricular lead  30  through the switch  74  to sample cardiac signals across any pair of desired electrodes. As shown in  FIG. 3  the microcontroller  60  generates a control signal  92  to control operation of the data acquisition circuit  90 . 
         [0027]    The microcontroller  60  includes an arrhythmia detector  77 , which operates to detect an arrhythmia, such as tachycardia and fibrillation, based on the intracardiac signal. The arrhythmia detector  77  senses R-waves in the intracardiac signal, each of which indicates a depolarization event occurring in the heart  12 . The arrhythmia detector  77  may sense an R-wave by comparing a voltage amplitude of the intracardiac signal with a voltage threshold value. If the voltage amplitude of the intracardiac signal exceeds the voltage threshold value, the arrhythmia detector  77  senses the R-wave. The arrhythmia detector  77  may also determine an event time for the R-wave occurring at a peak voltage amplitude of the R-wave. The arrhythmia detector  77  may receive an analog intracardiac signal from the sensing circuits  82  and  84  or a digital intracardiac signal from the data acquisition circuit  90 . Alternatively, the arrhythmia detector  77  may use the digitized intracardiac signal stored by the data acquisition circuit  90 . 
         [0028]    The microcontroller  60  may include a morphology detector  99  for confirming R-waves. The morphology detector  99  compares portions of the intracardiac signal with templates of known R-waves to confirm R-waves sensed in the intracardiac signal. In various embodiments, the morphology detector  99  is optional. 
         [0029]    The microcontroller  60  is further coupled to a memory  94  by a suitable computer bus  96  (e.g., an address and data bus), wherein the programmable operating parameters used by the microcontroller  60  are stored and modified, as required, in order to customize the operation of the stimulation device  10  to suit the needs of a particular patient. Such operating parameters define, for example, pacing pulse amplitude, pulse duration, electrode polarity, rate, sensitivity, automatic features, arrhythmia detection criteria, and the amplitude, waveshape and vector of each shocking pulse to be delivered to the patient&#39;s heart  12  within each respective tier of therapy. Other pacing parameters include base rate, rest rate and circadian base rate. 
         [0030]    Advantageously, the operating parameters of the stimulation device  10  may be non-invasively programmed into the memory  94  through a telemetry circuit  100  in telemetric communication with the external device  102 , such as a programmer, transtelephonic transceiver, or a diagnostic system analyzer. The telemetry circuit  100  is activated by the microcontroller  60  by a control signal  106 . The telemetry circuit  100  advantageously allows intracardiac electrograms and status information relating to the operation of the stimulation device  10  (as contained in the microcontroller  60  or memory  94 ) to be sent to the external device  102  through an established communication link  104 . 
         [0031]    The stimulation device  10  may further include a physiologic sensor  108 , commonly referred to as a “rate-responsive” sensor because it is typically used to adjust pacing stimulation rate according to the exercise state of the patient. However, the physiologic sensor  108  may further be used to detect changes in cardiac output, changes in the physiological condition of the heart, or diurnal changes in activity (e.g., detecting sleep and wake states). Accordingly, the microcontroller  60  responds by adjusting the various pacing parameters (such as rate, AV Delay, V-V Delay, etc.) at which the atrial and ventricular pulse generators,  70  and  72 , generate stimulation pulses. (V-V delay is typically used only in connection with independently programmable RV and LV leads for biventricular pacing.) While shown as being included within the stimulation device  10 , it is to be understood that the physiologic sensor  108  may also be external to the stimulation device  10 , yet still be implanted within or carried by the patient. A common type of rate responsive sensor is an activity sensor, such as an accelerometer or a piezoelectric crystal, which is mounted within the case  40  of the stimulation device  10 . Other types of physiologic sensors are also known, for example, sensors that sense the oxygen content of blood, respiration rate and/or minute ventilation, pH of blood, ventricular gradient, etc. However, any sensor may be used which is capable of sensing a physiological parameter that corresponds to the exercise state of the patient. 
         [0032]    The stimulation device additionally includes a battery  110 , which provides operating power to all of the circuits shown in  FIG. 3 . For the stimulation device  10 , which employs shocking therapy, the battery  110  should be capable of operating at low current drains for long periods of time, and then be capable of providing high-current pulses (for capacitor charging) when the patient requires a shock pulse. The battery  110  should also have a predictable discharge characteristic so that elective replacement time can be detected. Accordingly, the stimulation device  10  may employ lithium/silver vanadium oxide batteries. As further shown in  FIG. 3 , the stimulation device  10  is shown as having a measuring circuit  112  which is enabled by the microcontroller  60  via a control signal  114 . 
         [0033]    In the case where the stimulation device  10  is intended to operate as an implantable cardioverter/defibrillator (ICD) device, the stimulation device  10  detects and confirms the occurrence of an arrhythmia, and automatically applies an appropriate antitachycardia pacing therapy or electrical shock therapy to the heart  12  for terminating the detected arrhythmia. To this end, the microcontroller  60  further controls a shocking circuit  116  by way of a control signal  118 . The shocking circuit  116  generates shocking pulses of low (up to 0.5 joules), moderate (0.5-10 joules), or high energy (11 to 40 joules), as controlled by the microcontroller  60 . Such shocking pulses are applied to the patient&#39;s heart  12  through at least two shocking electrodes, and as shown in this embodiment, selected from the left atrial coil electrode  28 , the right ventricular coil electrode  36 , and/or the SVC coil electrode  38 . As noted above, the case  40  may act as an active electrode in combination with the right ventricular coil electrode  36 , or as part of a split electrical vector using the SVC coil electrode  38  or the left atrial coil electrode  28  (i.e., using the right ventricular coil electrode as a common electrode). 
         [0034]    Cardioversion shocks are of relatively low to moderate energy level (so as to minimize the current drain on the battery) and are usually between 5 to 20 joules. Typically, cardioversion shocks are synchronized with an R-wave. Defibrillation shocks are generally of moderate to high energy level (i.e., corresponding to thresholds in the range of 5 to 40 joules), delivered asynchronously (since R-waves may be too disorganized), and pertaining exclusively to the treatment of fibrillation. Accordingly, the microcontroller  60  is capable of controlling the synchronous or asynchronous delivery of the shocking pulses. 
       Feedthrough Header Assembly 
       [0035]      FIG. 4  shows exploded view drawing showing a portion of a feedthrough assembly  405  of the implantable cardiac device  410 . The feedthrough posts  425  are straight and extend directly between the connector blocks  435  through the feedthrough dielectric  415 . The conductor posts  425  may be titanium posts manufactured to include the connector blocks  435  for electrical contact with lead pins &amp; rings (not shown). Thus, the connector blocks  435  and the conductor posts  425  are integrally formed, for example by machining, or by metal injection molding. The connector blocks  435  may include holes  435   p  and  435   r  to accept the pins and rings (not shown), respectively, as well as holes  435   s  for setscrews  575  (shown in  FIG. 5 ), to establish electrical contact and accomplish mechanical retention of leads (not shown). 
         [0036]    Titanium conductor posts  425  may be brazed to a ceramic feedthrough dielectric  415 . The feedthrough header assembly  405  may also contain discoidal capacitors (not shown), which will connect to the posts to form an EMI filter. Typically there is one filter per conductor post  425 . The capacitors (not shown) may be embedded within the feedthrough dielectric  415 . 
         [0037]    A titanium collar  440  with flange  445  encloses the feedthrough dielectric  415  and conductor posts  425 . The flange  445  may be welded to the device case  465 , which also may be made of titanium. 
         [0038]      FIG. 5  shows a perspective view of a header  520 . Referring to  FIGS. 4 and 5 , the header  520  covers the feedthrough assembly  405 . The header  520  may be molded/cast directly on the feedthrough assembly  405 , with cavities  435   c   DF  and  435   c   IS  formed to allow connection of leads (not shown) to the connector blocks  435 . The connector blocks  435  on the conductor posts  425  will form the IS-1 and DF-1 connector cavities  435   c   DF  and  435   c   IS , respectively. Although a six pole device is shown for illustration purposes, other embodiments may have a different number of connector blocks and conductor posts. 
         [0039]      FIG. 6  shows a perspective view of an implantable cardiac device  610  with an attached header assembly  630 . 
         [0040]    Referring to  FIG. 4 , the posts  425  of the feedthrough assembly  405  may extend through the dielectric feedthrough to allow electrical connection of the feedthrough posts  425  with a printed wire board (not shown) within the case  465 , for example via a flex cable (not shown), or other know connection means. 
         [0041]    The case  465  and feedthrough  405  are typically hermetically sealed and also provide shielding from electromagnetic noise or other interference signals. The feedthrough  405  is the interface between the leads (not shown) and the electronics (not shown) inside the case  465 . 
         [0042]    With the conventional implantable cardiac device of  FIG. 2 , the feedthrough dielectrics  215  are closely spaced on an small inclined edge portion of the case  60  between a top and side edges of the case  60 . In the embodiment of  FIG. 4 , the feedthrough dielectric is a significant portion, of the upper edge of the case  465 . 
         [0043]    One benefit of having more spacing between posts  425  in the feedthrough  405  is that because there can be over 800V sent through the posts when shocking, it is helpful to space the posts  425  farther apart in the dielectric  415  to inhibit shorting and break down of the dielectric. 
         [0044]    With conventional configurations, such as shown in  FIG. 2 , the platinum iridium wires have to be formed so that the blocks are in the proper location. With the embodiment of  FIG. 4 , however, the posts are spaced within the dielectric  415  so that the connector blocks are positioned exactly where they need to be, rather than bending the platinum indium wires  225  to position the connector blocks  435 . 
         [0045]    In various embodiments, the conductor posts provide a wireless feedthrough for a header assembly. In some embodiments, the integral posts need not have a bigger diameter than the conventional wires, and may be curved in some embodiments. As disclosed above, in some embodiments, the feedthrough flange can be welded/braised to the case, so no backfilling is required. 
         [0046]      FIG. 7  shows a possible embodiment of the feedthrough assembly  705  having individual dielectric rings  715  for each of the conductor posts  725 . The dielectric rings  715  may be ceramic and further include a capacitor embedded in each of the rings  715 , i.e. a capacitor associated with each of the conductor posts  725 . In this embodiment, the collar  740  and flange  745  encircle each of the conductor posts  725  individually, rather than collectively as in the embodiment shown in  FIG. 4 . 
         [0047]    Various embodiments of the present invention allow reduced manufacturing complexity by eliminating wire forming and wire to block welding. Moreover, various embodiments may provide greater system reliability, with the possibility of shorting between wire and case virtually eliminated. Further, in various embodiments, the resistance may be reduced by decreased conductor post length and increased cross-sectional area of posts. In addition, various embodiments allow use of conductor material other than platinum iridium to significantly reduce header cost. 
         [0048]    Although exemplary methods, devices, systems, etc., have been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as exemplary forms of implementing the claimed methods, devices, systems, etc.