Patent Publication Number: US-2023157882-A1

Title: Scanning laser ophthalmoscope laser guidance for laser vitreolysis

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to ophthalmic laser surgical systems, and more particularly to scanning laser ophthalmoscope laser guidance for laser vitreolysis. 
     BACKGROUND 
     In ophthalmic laser surgery, a surgeon may direct a laser beam into the eye to treat the eye. For example, a laser beam may be directed into the vitreous to treat eye floaters. Eye floaters are clumps of collagen proteins that form in the vitreous. These clumps can disturb vision with moving shadows and distortions. The laser beam may be used to fragment the floaters to improve vision. 
     BRIEF SUMMARY 
     In certain embodiments, an ophthalmic laser surgical system for treating a floater in an eye includes a scanning laser ophthalmoscopy (SLO) device, a treatment laser device, an xy-scanner, and a computer. The SLO device includes a fast photodiode and a confocal filter. The SLO device: directs an SLO beam along an SLO beam path towards a retina of the eye, receives the SLO beam reflected from the eye using the fast photodiode, generates an image from the reflected SLO beam, the image including a floater shadow cast by the floater on the retina, determines an xy-location of the floater shadow according to an xy-scanner, and determines a z-location of the floater relative to the retina using the confocal filter. The treatment laser device directs a laser beam along a laser beam path towards the z-location of the floater. The xy-scanner receives the SLO beam from the SLO device and directs the SLO beam along the SLO beam path towards the xy-location of the floater shadow. The xy-scanner also receives the laser beam from the treatment laser device and directs the laser beam along the SLO beam path towards the xy-location of the floater shadow. The computer controls the SLO device and the treatment laser device. 
     Embodiments may include none, one, some, or all of the following features:
         The ophthalmic laser surgical system includes an xy-encoder that detects a position of the xy-scanner corresponding to an xy-location expressed in encoder units and reports the xy-location expressed in encoder units as the xy-location of the floater shadow.   The treatment laser device includes a z-focusing component that receives the z-location of the floater and directs a focal point of the laser beam towards the z-location of the floater along an angular direction of the xy-location of the floater shadow.   The SLO device scans over a larger angular range of 40 degrees or greater. The SLO device may also scan over a smaller angular range that is smaller than the larger angular range.   The computer predicts next xy-locations of the floater shadow, including a first xy-location and a second xy-location later than the first xy-location. The computer may instruct the SLO device to direct the SLO beam at the first xy-location of the floater shadow, and to determine the z-location of the floater. The computer may instruct the SLO device to direct the SLO beam at the second xy-location, and may instruct the treatment laser device to direct the laser beam at the z-location of the floater.       

     In certain embodiments, an ophthalmic laser surgical system for treating a floater in an eye comprises a scanning laser ophthalmoscopy (SLO) device, a treatment device, and a computer. The SLO device comprises a confocal filter with a lens and a pinhole. The SLO device directs an SLO beam along an SLO beam path towards the eye, generates an image of the retina of the eye, where the image shows the floater shadow of the floater cast on the retina, and determines an xy-location of the floater shadow. The SLO device adjusts the position of the focal point of the lens relative to the pinhole of the confocal filter to generate an image of the floater, and determines the z-location of the floater relative to the retina according to the position of the focal point of the lens relative to the pinhole. The treatment laser device directs a laser beam along a laser beam path towards the xy-location and the z-location of the floater. The computer controls the SLO device and the treatment laser device. 
     Embodiments may include none, one, some, or all of the following features:
         The treatment laser device directs the focal point of the laser beam towards the z-location of the floater along an angular direction of the xy-location of the floater shadow.   The ophthalmic laser surgical system further comprises an xy-scanner. The xy-scanner receives the SLO beam from the SLO device and directs the SLO beam along the SLO beam path towards the xy-location of the floater shadow. The xy-scanner also receives the laser beam from the treatment laser device and directs the laser beam along the SLO beam path towards the xy-location of the floater shadow. The ophthalmic laser surgical system may include an xy-encoder. The xy-encoder detects the position of the xy-scanner, which corresponds to an encoder xy-location expressed in encoder units, and reports the encoder xy-location as the xy-location of the floater shadow.   The computer predicts next xy-locations of floater shadow, including a first xy-location and a second xy-location later than the first xy-location. The computer may instruct the SLO device to direct the SLO beam at the first xy-location of the floater shadow and to determine the z-location of the floater. The computer may instruct the SLO device to direct the SLO beam at the second xy-location and may instruct the treatment laser device to direct the laser beam at the z-location of the floater.   The SLO device scans the SLO beam over a larger angular range of 40 degrees or greater. The SLO device may scan the SLO beam over a smaller angular range that is smaller than the larger angular range.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates an example of an ophthalmic laser surgical system that may be used to treat an eye, according to certain embodiments; 
         FIG.  2    illustrates an example of an image that may be generated by the system of  FIG.  1   ; 
         FIG.  3    is an example of scanning laser ophthalmoscope (SLO) device that may be used in the system of  FIG.  1   , according to certain embodiments; 
         FIG.  4    is a graph illustrating an example of tracking and predicting the xy-location of a floater shadow, which may be used by the system of  FIG.  1   , according to certain embodiments; and 
         FIG.  5    illustrates an example of a method for treating a floater that may be performed by the system of  FIG.  1   , according to certain embodiments. 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Referring now to the description and drawings, example embodiments of the disclosed apparatuses, systems, and methods are shown in detail. The description and drawings are not intended to be exhaustive or otherwise limit the claims to the specific embodiments shown in the drawings and disclosed in the description. Although the drawings represent possible embodiments, the drawings are not necessarily to scale and certain features may be simplified, exaggerated, removed, or partially sectioned to better illustrate the embodiments. 
     Certain imaging systems may use an optical coherence tomography (OCT) device to image and determine the z-location of floaters in the eye. However, OCT devices are expensive. Accordingly, the systems described herein use a scanning laser ophthalmoscope (SLO) device to measure the z-location of the floater, as well as the xy-location of the floater shadow. The SLO device includes a confocal filter that can be used to determine the z-location of the floater. 
       FIG.  1    illustrates an example of an ophthalmic laser surgical system  10  that may be used to treat an eye, according to certain embodiments. As an overview, system  10  includes a scanning laser ophthalmoscope (SLO) device  21 , a treatment laser device  22 , one or more shared components  24 , and a computer  26 , coupled as shown. Treatment laser device  22  includes a laser  30  and a z-focusing component  32 , coupled as shown. Shared components  24  include an xy-scanner  40 , an xy-encoder  41 , and optical elements (such as a mirror  42  and lenses  44  and  46 ), coupled as shown. Computer  26  includes logic  50 , a memory  52  (which stores a computer program  54 ), and a display  56 , coupled as shown. 
     As an overview of operation of system  10 , SLO device  21  directs an SLO beam along an SLO beam path towards a floater shadow and/or floater within an eye and determines an xy-location of the floater shadow according to an xy-scanner and/or a z-location of the floater relative to the retina. Treatment laser device  22  directs a laser beam along a laser beam path towards the z-location of the floater. Shared component xy-scanner  40  receives the SLO beam and the xy-location of the floater shadow and directs the SLO beam along the SLO beam path towards the xy-location of the floater shadow. Xy-scanner  40  also receives the laser beam from treatment laser device  22  and directs the laser beam along the laser beam path aligned with the SLO beam path towards the xy-location of the floater shadow. 
     Turning to the parts of the system, SLO device  21  detects, locates, and/or images a floater and/or floater shadow in the vitreous. To image a floater shadow, SLO device  21  directs an SLO beam along an SLO beam path towards the retina, onto which the shadow is cast. SLO device  21  detects the reflected beam and generates an image from the reflected beam, which may be displayed on display  56  as a video. SLO device  21  determines (and may with the help of computer  26 ) the xy-location of the floater shadow from the image of the shadow. SLO device  21  has a higher image frame rate (e.g., 30 to 60, such 45 to 55, or approximately 50, frames per sec (frames/s)) than that of an interferometer device, which allows for faster tracking of the floater shadow. In addition, SLO device  21  includes a confocal filter that includes a z-focusing component (e.g., a tunable confocal lens) that can be used to measure the z-location of a floater, as described with reference to  FIG.  3   . 
     Turning to treatment laser device  22 , ultrashort pulse laser  30  generates a laser beam with any suitable wavelength, e.g., in a range from 400 nm to 2000 nm. Treatment laser device  22  delivers laser pulses at any suitable repetition rate (e.g., a single pulse to 200 megahertz (MHz)). A laser pulse has any suitable pulse duration (e.g., 20 femtoseconds (fs) to 1000 nanoseconds (ns)), any suitable pulse energy (e.g., 1 nanojoule (nJ) to 10 millijoule (mJ)), and a focal point of any suitable size (e.g., 1 to 30 microns (μm)). In a particular embodiment, the laser is a picosecond or femtosecond laser with a repetition rate that exceeds 100 pulses per second (pps). 
     Z-focusing component  32  longitudinally directs the focal point of the laser beam to a specific location in the direction of the floater shadow. In certain embodiments, z-focusing component  32  receives the z-location of the floater from computer  26  or SLO device  21 , and directs the laser beam towards the z-location of the floater. Z-focusing component  32  may include a lens of variable refractive power, a mechanically movable lens, an electrically tunable lens (e.g., Optotune lens), an electrically or mechanically tunable telescope. In certain embodiments, treatment laser device  22  or the optical delivery system also includes a fast xy-scanner used in tandem with z-focusing component  32  to, e.g., create a 3D focal spot pattern. Examples of such scanners include galvo, MEMS, resonant, or acousto-optical scanners. 
     Shared components  24  direct SLO and laser beams from SLO device  21  and treatment laser device  22 , respectively, towards the eye. Because SLO and laser beams both use shared components  24 , both beams are affected by the same optical distortions (e.g., fan distortion of scanners, barrel or pillow distortions of the scanner lens, refractive distortions from the inner eye surfaces, and other distortions). The distortions affect both beams in the same way, so the distortions are compensated for. This allows for aiming the laser beam using images generated by the SLO beam with improved accuracy. 
     As an overview of operation of shared components  24 , mirror  42  directs a beam (SLO and/or laser beam) towards xy-scanner  40 , which transversely directs the beam towards lens  44 . Lenses  44  and  46  direct the beam towards eye. Shared components  24  may also provide spectral and polarization coupling and decoupling of SLO and laser beams to allow the beams to share the same path. 
     Turning to the details of shared components  24 , in certain embodiments, xy-scanner  40  receives the xy-location of the floater shadow from SLO device  20  or computer  26 , and directs the SLO and/or laser beam towards the xy-location. Xy-scanner  40  may be any suitable xy-scanner that transversely directs the focal point of the beam in the x- and y-directions and changes the angle of incidence of the beam into the pupil. For example, xy-scanner  40  includes a pair of galvanometrically-actuated scanner mirrors that can be tilted about mutually perpendicular axes. As another example, xy-scanner  40  includes an acousto-optical crystal that can acousto-optically steer the beam. As another example, xy-scanner  40  includes a fast scanner (e.g., a galvo, resonant, or acousto optical scanner) that can create, e.g., a 2D matrix of laser spots. y-encoder  41  detects the position of xy-scanner  40  and reports the position as the xy-location. For example, xy-encoder  41  detects the angular orientations of the galvanometer mirrors of xy-scanner  40  in encoder units. Xy-encoder  41  may report the position in encoder units to SLO device  21 , treatment laser device  22 , and/or computer  26 . Since SLO device  21  and treatment laser device  22  share xy-scanner  40 , computer  26  can use the encoder units to instruct system  20  and device  22  where to aim their beams, making it unnecessary to perform the computer-intensive conversion from encoder units to a length unit such as millimeters. Xy-encoder  41  may report the positions at any suitable rate, e.g., once every 5 to 50 milliseconds (ms), such as every 10 to 30 or approximately every 20 ms. 
     Shared components  24  also include optical elements. In general, an optical element can act on (e.g., transmit, reflect, refract, diffract, collimate, condition, shape, focus, modulate, and/or otherwise act on) a laser beam. Examples of optical elements include a lens, prism, mirror, diffractive optical element (DOE), holographic optical element (HOE), and spatial light modulator (SLM). In the example, optical elements include mirror  42  and lenses  44  and  46 . Mirror  42  may be a trichroic mirror. Lenses  44  and  46  may be scanning optics of an SLO device. 
     Computer  26  controls components of system  10  (e.g., SLO device  21 , treatment laser device  22 , and/or shared components  24 ) in accordance with a computer program  54 . Computer  26  may be separated from components or may be distributed among system  10  in any suitable manner, e.g., within SLO device  21 , treatment laser device  22 , and/or shared components  24 . In certain embodiments, portions of computer  26  that control SLO device  21 , treatment laser device  22 , and/or shared components  24  may be part of SLO device  21 , treatment laser device  22 , and/or shared components  24 , respectively. 
     Computer  26  controls and may be part of the components of system  10  to allow the components to perform their operations. Computer  26  controls the components in accordance with a computer program  54 . Examples of computer programs  54  include floater shadow imaging, floater shadow tracking, image processing, floater evaluation, retinal exposure calculation, patient education, and insurance authorization programs. For example, computer  26  may use a computer program  54  to instruct and/or control SLO device  21 , treatment laser device  22 , and/or shared components  24  to image a floater shadow or a floater, determine the xy- and z-locations of the floater, and focus a laser beam at the floater. 
     In certain embodiments, computer  26  uses an image processing program  54  to perform image processing on an image, e.g., analyze the digital information of the image to extract information from the image. In certain embodiments, image processing program  54  analyzes an image of a floater shadow to obtain information about the floater. For example, program  54  may detect a floater shadow by detecting a darker shape in an image (using, e.g., edge detection or pixel analysis). As another example, program  54  may detect the shape and size of a floater shadow, which indicate the size and shape of the floater. As another example, program  54  may detect the tone or luminescence of the floater shadow, which indicates the density of the floater. 
     In certain embodiments, computer  26  uses a tracking program  54  to track and/or predict the movement of a floater shadow. For example, computer  26  may perform image analysis of retinal video from the SLO device to track the movement of the floater shadow. Tracking program  54  may predict the movement of the floater shadow and send to treatment laser device  22  the location of where the floater shadow is predicted to be when the laser beam reaches the floater. In certain embodiments, computer  26  may perform tracking and/or predicting operations as a part of SLO device  21 . Tracking and predicting floater shadow movement is described in more detail with reference to  FIG.  4   . 
       FIG.  2    illustrates an example of a retinal image  60  that may be generated by system  10  of  FIG.  1   . Image  60  shows the retina  62  of an eye, with a foveal region (or fovea)  64  and a parafoveal region (or parafovea)  66 . Generally, fovea  64  has a visual angle of approximately +/− one degree, and parafovea  66  has a visual angle of approximately +/− seven degrees. Image  60  also shows examples of floater shadows  68  ( 68   a ,  68   b ,  68   c ) that floaters cast on retina  62 . Other floater shadows may have a different size, shape, and/or optical density. 
     A floater may move when the gaze of the patient moves. Most floaters are embedded in the vitreous, a viscous substance, so the movement is relatively slow and predictable, with no unexpected accelerating or sudden stopping. Accordingly, tracking floater shadows is technically feasible. Non-moving shadows are generally not caused by floaters, and may be caused by, e.g., corneal or lens opacities or anatomical changes of the retina, so floater treatment is not concerned with non-moving shadows. 
     A floater may be regarded as clinically significant if it can cause a visual disturbance, which can be determined from any suitable features of the floater shadow, e.g., the size and/or density of the shadow, proximity of the shadow to the fovea and/or parafovea, and/or the track of the shadow relative to the fovea and/or parafovea. As an example, a floater can cause a visual disturbance if it permanently or transiently casts a shadow  68  on fovea  64  or can cause distraction or annoyance if it permanently or transiently casts a shadow  68  on parafovea  66 . Accordingly, if a floater shadow falls within or is predicted to move within fovea  64  and/or parafovea  66 , the floater may be designated as clinically significant. As another example, floater shadow  68  can be used to estimate the size and density of the floater. Larger, denser floaters are more likely to cause a visual disturbance. Thus, a shadow  68  larger than a critical shadow size can indicate a clinically significant floater. A shadow  68  with a higher contrast relative to the background may indicate a clinically significant floater. 
     In certain embodiments, a user such as a surgeon may determine significance from the displayed images (such as a video) of the floater shadow. An image processing program can assist the user in making the decision. In other embodiments, the computer can use image processing and target evaluation computer programs to determine significance from the image. 
       FIG.  3    is an example of scanning laser ophthalmoscope (SLO) device  21  that may be used in system  10  of  FIG.  1   , according to certain embodiments. SLO device  21  includes a tunable confocal lens that can measure the z-location of a floater. In the example, SLO device  21  includes a laser source  80 , a collimating lens  82 , a beam splitter  84 , a confocal filter, (comprising a z-scanner lens  86  and a pinhole  88 ), and a photodiode  90 , coupled as shown. 
     As an example of operation, laser source  80  generates an SLO beam, and collimating lens  82  collimates the beam. Beam splitter  84  transmits the beam from laser source  80  to shared components  24 . Xy-scanner  40  (which includes a pair of scanner mirrors) deflects the beam towards the eye. Xy-scanner  40  may scan the SLO beam over any suitable angular range, e.g., a larger range such as at least 30, 40, 50, or 120 degrees, or a smaller range less than the larger range. Lenses  44  and  46  conjugate the scanner mirrors into the pupil of the eye. The SLO beam enters the eye through the pupil. The natural lens of the eye focuses the SLO beam onto the retina of the eye. 
     The natural lens of the eye and lenses  44  and  46  collimate the back-reflected light from the retina. Xy-scanner  40  and beamsplitter  84  direct the back-reflected light towards the confocal filter, which includes lens  86  and pinhole  88 . Depending on the position of the focal point of lens  86  relative to pinhole  88 , different parts of the interior of the eye can be imaged. For example, if the focal point of lens  86  is located at pinhole  88 , the confocal filter transmits only the focused SLO beam reflected from the retina (which can show floater shadows) and suppresses the other light. As another example, the focal point of lens  86  may be placed before pinhole  88  in order to visualize a floater and suppress the other back-reflected light. Photodiode  90  measures the intensity of the back-reflected light. 
     Computer  20  records the angular orientation of the mirrors of xy-scanner  40  and the intensity of the back-reflected light as measured by photodiode  90 . Computer  20  uses this information to generate an image of the retina or floater. The speed of a computer  26  of a standard SLO is typically high enough to display the retinal image as a real-time video. 
     Turning to the components, laser source  80  may be any suitable laser that generates an SLO beam, which may comprise white light. The confocal filter directs light towards photodiode  90  and includes lens  86  and pinhole  88 . Lens  86  may be any suitable scanner or lens that can change the focus of light in the z-direction, e.g., an electrically tunable lens. The distance between the focal point of lens  86  and pinhole  88  (“ZCF distance”) can be adjusted to image different parts of the eye interior in any suitable manner. For example, the ZCF distance may be mechanically adjusted. As another example, lens  86  may be an electrically tunable lens (e.g., an Optotune lens) that can adjust its focal point. 
     Photodiode  90  may be any suitable light detector, e.g., an avalanche photodiode (APD). Photodiode  90  may be a fast photodiode, such as a photodiode with a response time in the range of 0.1 nanosecond (ns) to 1 microsecond (us), such as 1 ns to 1 us. The response time may be selected according to desired sensitivity. In certain embodiments, photodiode  90  may allow for a video frame rate of up to 25 frame/sec with a spatial resolution of approximately 20 micrometers (um)). 
     In certain embodiments, computer  20  and/or SLO device  21  can utilize information from the confocal filter to determine the distance between the floater and the retina (“FR distance”) in order to focus the treatment laser onto a floater. In the embodiments, computer  20  accesses optical software to convert the ZCF distance to the FR distance. Computer  20  uses the FR distance to adjust z-focusing component  32  of laser device  22  to focus the treatment laser beam onto the floater. 
       FIG.  4    is a graph  180  illustrating an example of tracking and predicting the xy-location of a floater shadow, which may be used by ophthalmic laser surgical system of  FIG.  1   , according to certain embodiments. In the embodiments, a computer uses a tracking program to track and/or predict the movement of a floater shadow. For example, the computer performs image analysis of retinal images to track the movement of the floater shadow to track the floater. As discussed with reference to  FIG.  2   , floater treatment is concerned with moving shadows. 
     In the example, the xy-location is given in encoder units (which may be provided by encoder  41 ). Variable t represents time t=−3, −2, −1, 0, 1, 2, where t=0 is the current time, t=−3, −2, −1 is the past time, and t=1, 2, 3 is the future time. Yt represents the y-location in encoder units at time t, and Xt represents the x-location in encoder units at time. The tracking program may predict the future xy-locations from extrapolations of past xy-locations. 
     In the example, the confocal filter, which includes lens  86  and pinhole  88 , measures the z-location of the floater at the xy-location (x1, y1) at time t=1, shown at reference number  182 . The measurement may be performed a few milliseconds prior to firing the laser. At the xy-location (x2, y2) at time t=2, shown at reference number  184 , the treatment laser device fires a laser beam comprising laser pulses. The laser beam is directed by the xy-scanner to the xy-location (x2, y2) and is focused by the z-focusing component at the z-location. In general, floaters do not move much in the z-direction, so the z-location measured at t=1 may be sufficiently close to the z-location at t=2. 
       FIG.  5    illustrates an example of a method for treating a floater that may be performed by system  10  of  FIG.  1   , according to certain embodiments. The method starts at step  110 , where the SLO device scans over a larger angular range to generate images of the retina. For example, the SLO may scan an angular range of 40 degrees or greater with a frame rate of 50 frame per second (frame/s) or greater. 
     The computer identifies the xy-location of the floater shadow from the images at step  112 . The SLO device tracks the floater shadow at step  114 . The SLO device scans over a smaller angular range at step  116 . For example, the SLO may scan a smaller angular range of 5 to 20 degrees. The smaller angular range allows for a faster frame rate. 
     The computer predicts the xy-locations of the floater shadow at step  118  at future SLO frames during which the z-location of the floater can be measured and laser pulses can be directed to the floater. For example, the computer may predict the xy-locations at the next 2 to 5 frames, e.g., the xy-locations (x1, y1) and (x2, y2) at the next frames 1 and 2 may be predicted. In certain embodiments, an encoder provides the location of the shadow in encoder units, and the computer may predict future shadow locations from past shadow locations. 
     The SLO device directs the SLO beam at predicted location (x1, y1) and the confocal filter measures the z-location of the floater at step  120 . The treatment laser device focuses laser pulses at the z-location of the floater at step  122 . For example, the computer instructs the z-focusing component of the laser device to focus pulses at the z-location. The SLO device directs the SLO beam at the predicted location (x2, y2) at step  124 . During the duration of steps  120  and  124 , floaters typically move in the xy-direction, with negligible movement in the z-direction. 
     The treatment laser device directs laser pulses at the floater at step  126  to fragment the floater. Floaters have a volume with dimensions of typically a few millimeters. In certain embodiments, the laser pulses may form a two-dimensional (2D) or three-dimensional (3D) pattern of any suitable number of pulses, which may range from a few tens to a few thousand pulses, and may depend in the size of the floater. Any suitable repetition rate may be used. For example, a repetition rate of several kHz may yield a treatment time that is less than one second. 
     A component (such as the control computer) of the systems and apparatuses disclosed herein may include an interface, logic, and/or memory, any of which may include computer hardware and/or software. An interface can receive input to the component and/or send output from the component, and is typically used to exchange information between, e.g., software, hardware, peripheral devices, users, and combinations of these. A user interface is a type of interface that a user can utilize to communicate with (e.g., send input to and/or receive output from) a computer. Examples of user interfaces include a display, Graphical User Interface (GUI), touchscreen, keyboard, mouse, gesture sensor, microphone, and speakers. 
     Logic can perform operations of the component. Logic may include one or more electronic devices that process data, e.g., execute instructions to generate output from input. Examples of such an electronic device include a computer, processor, microprocessor (e.g., a Central Processing Unit (CPU)), and computer chip. Logic may include computer software that encodes instructions capable of being executed by an electronic device to perform operations. Examples of computer software include a computer program, application, and operating system. 
     A memory can store information and may comprise tangible, computer-readable, and/or computer-executable storage medium. Examples of memory include computer memory (e.g., Random Access Memory (RAM) or Read Only Memory (ROM)), mass storage media (e.g., a hard disk), removable storage media (e.g., a Compact Disk (CD) or Digital Video or Versatile Disk (DVD)), database, network storage (e.g., a server), and/or other computer-readable media. Particular embodiments may be directed to memory encoded with computer software. 
     Although this disclosure has been described in terms of certain embodiments, modifications (such as changes, substitutions, additions, omissions, and/or other modifications) of the embodiments will be apparent to those skilled in the art. Accordingly, modifications may be made to the embodiments without departing from the scope of the invention. For example, modifications may be made to the systems and apparatuses disclosed herein. The components of the systems and apparatuses may be integrated or separated, or the operations of the systems and apparatuses may be performed by more, fewer, or other components, as apparent to those skilled in the art. As another example, modifications may be made to the methods disclosed herein. The methods may include more, fewer, or other steps, and the steps may be performed in any suitable order, as apparent to those skilled in the art. 
     To aid the Patent Office and readers in interpreting the claims, Applicants note that they do not intend any of the claims or claim elements to invoke 35 U.S.C. § 112(f), unless the words “means for” or “step for” are explicitly used in the particular claim. Use of any other term (e.g., “mechanism,” “module,” “device,” “unit,” “component,” “element,” “member,” “apparatus,” “machine,” “system,” “processor,” or “controller”) within a claim is understood by the applicants to refer to structures known to those skilled in the relevant art and is not intended to invoke 35 U.S.C. § 112(f).