Patent Publication Number: US-11646113-B2

Title: Systems and methods for determining magnetic location of wireless tools

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 62/489,019, filed on Apr. 24, 2017, which is incorporated herein by reference. 
    
    
     SUMMARY 
     A method for locating a tool in a three dimensional (3D) space is provided. The method includes determining whether location data, corresponding to a location of the tool, is available. If the location data is available, the method includes providing the location data for presenting the location of the tool. If the location data is not available, the method includes determining an estimated location of the tool based on a velocity of the tool and an acceleration of the tool, generating estimated location data corresponding to the estimated location of the tool and providing the estimated location data for presenting the estimated location as the location of the tool. The method also includes determining whether accelerometer data is available. If accelerometer data is available, the method includes using the accelerometer data to estimate the location of the tool. 
     An electromagnetic navigation system for locating a tool in a 3D space is provided. The system includes memory configured to store data and a processor, in communication with the memory. The processor is configured to determine whether location data, corresponding to a location of the tool, is available. If the location data is available, the processor is configured to provide the location data for presenting the location of the tool. If the location data is not available, the processor is configured to determine an estimated location of the tool based on a velocity of the tool and an acceleration of the tool, generate estimated location data corresponding to the estimated location of the tool and provide the estimated location data for presenting the estimated location as the location of the tool. 
     A non-transitory computer readable medium is provided. The computer readable medium has instructions which when executed cause a computer to perform a method of locating a tool in a 3D space. The method includes determining whether location data, corresponding to a location of the tool, is available. If the location data is available, the method includes providing the location data for presenting the location of the tool. If the location data is not available, the method includes determining an estimated location of the tool based on a velocity of the tool and an acceleration of the tool, generating estimated location data corresponding to the estimated location of the tool and providing the estimated location data for presenting the estimated location as the location of the tool. The method also includes determining whether accelerometer data is available. If accelerometer data is available, the method includes using the accelerometer data to estimate the location of the tool. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more detailed understanding can be had from the following description, given by way of example in conjunction with the accompanying drawings wherein: 
         FIG.  1    is an illustration of an example medical system for navigating a tool in a 3-D space within which embodiments disclosed herein may be implemented; 
         FIG.  2    is a block diagram illustrating components of an example medical system for use with embodiments described herein; 
         FIG.  3    is an illustration of an example wireless tool for use with embodiments described herein; and 
         FIG.  4    is a flow diagram illustrating an example method of locating the tool in 3-D space according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electromagnetic navigation systems are used to determine the location of medical tools in a 3-D space during a medical procedure. During the procedures, medical tools generate and transmit signals (e.g., electrical signals based on the amplitude and phase of magnetic fields) to facilitate the determination of their locations. In some conventional systems, the signals are transmitted to system components via a wired medium (e.g., cable). 
     Due to the advancement in short-range radio technology, however, some systems utilize tools that are wirelessly connected to the system components and the signals are wirelessly transmitted to the system components via various short range wireless protocols (Institute of Electrical Engineers (IEEE) 802.11g IrDA (infrared data) and Ericsson Bluetooth™. For example, medical personnel (e.g., ear, nose and throat (ENT) physicians and cardiologists) use battery-powered tools, such as catheters, for performing the medical procedures on patient anatomy. Based on the determined locations of the tools, anatomical information of a patient is presented (e.g., displayed) to the medical personnel. Accordingly, the efficiency and success of the procedures rely on continually providing the locations of the tools. 
     The present application discloses systems, apparatuses and methods of using magnetic fields to calculate the location of medical tools in a 3-D space. Each tool is configured to wirelessly send data (e.g., location data using the magnetic fields (hereinafter “location data”), velocity data and acceleration data) to a processing device for mapping the location of the tool in the 3-D space. When the location data, corresponding to the location of the tool in the 3-D space at a point in time or time period, is not available (e.g., the location data is not received at the processing device, the data is inaccurate) for processing, the processing device uses previously calculated data to estimate the tool&#39;s location in a 3-D space. For example, the processing device uses previously calculated data corresponding to the tool&#39;s velocity and acceleration at different locations over time. The velocity and acceleration of the tool may be continually calculated during operation such that calculated data is available for processing to estimate the location of the tool when the location data is not available for processing. The processing device may also determine whether accelerometer data (i.e., acceleration data from an accelerometer at the tool) is available for processing and use the accelerometer data, in addition to or alternative to the previously calculated data, to estimate the tool&#39;s location in the 3-D space. 
     Referring now to  FIG.  1   , an illustration of an example medical system  20  is shown that may be used to generate and display information  52  (e.g., a chart, anatomical models of a portion of a patient and signal information). The system  20  and the tool  22  shown in  FIG.  1    are merely by example. Medical tools, such as tool  22 , can be any tool used for diagnostic or therapeutic treatment, such as for mapping electrical potentials in a heart  26  of a patient  28 . Alternatively, tools may be used, mutatis mutandis, for other therapeutic and/or diagnostic purposes of different portions of anatomy, such as in the heart, lungs or other body organs, such as the ear, nose, and throat (ENT). Tools may include, for example, probes, catheters, cutting tools and suction devices. 
     An operator  30  may insert the tool  22 , which may include a non-tip section  54  and a tip  56  into a portion of patient anatomy, such as the vascular system of the patient  28  so that the tip  56  of the tool  22  enters a chamber of the heart  26 . The control console  24  may use magnetic position sensing to determine position coordinates of the tool  22  (e.g., coordinates of the tip  56 ) in 3-D space inside the heart  26 . To determine the position coordinates, a driver circuit  34  in the control console  24  may drive, via connector  44 , field generators  36  to generate magnetic fields within the anatomy of the patient  28 . 
     The field generators  36  include one or more emitter coils (not shown in  FIG.  1   ), placed at known positions external to the patient  28 , which are configured to generate magnetic fields in a predefined working volume that contains a portion of interest of the patient anatomy. Each of the emitting coils is driven by a different frequency to emit a constant magnetic field in 3-D space. For example, in the example medical system  20  shown in  FIG.  1   , one or more emitter coils can be placed below the torso of the patient  28  and each configured to generate magnetic fields in a predefined working volume that contains the heart  26  of the patient. 
     As shown in  FIG.  1   , a magnetic field location sensor  38  is disposed at the tip  56  of tool  22 . The magnetic field location sensor  38  is used to determine the position of the receiving coil in 3-D space and generate electrical signals based on the amplitude and phase of the magnetic fields. Although the magnetic field location sensor  38  is disposed at the tip  56  of tool  22 , a tool can include one or more magnetic field location sensors each disposed at any portion of the tool. 
     The signals are wirelessly communicated to the control console  24  via a wireless communication interface at the tool  22  that may communicate with a corresponding input/output (I/O) interface  42  in the control console  24 . The wireless communication interface and the I/O interface  42  may operate in accordance with any suitable wireless communication standard that is known in the art, such as for example, infrared (IR), radio frequency (RF), Bluetooth, one of the IEEE 802.11 family of standards (e.g., Wi-Fi), or the HiperLAN standard. The body surface electrodes  46  may include one or more wireless sensor nodes integrated on a flexible substrate. The one or more wireless sensor nodes may include a wireless transmit/receive unit (WTRU) enabling local digital signal processing, a radio link, and a miniaturized rechargeable battery, as described in more detail below. 
     The I/O interface  42  may enable the control console  24  to interact with the tool  22 , the body surface electrodes  46  and the position sensors (not shown). Based on the electrical impulses received from the body surface electrodes  46  and the electrical signals received from the tool  22  via the I/O interface  42  and other components of medical system  20 , the processor  40  may determine the location of the tool in 3-D space and generate the display information  52 , which may be shown on a display  50 . Although display information  52  is shown on a display  50 , it is possible to generate and present the location of the tool  22  in any known manner such as audibly. 
     Processor  40 , which may include one or more processors, is configured to process the signals (e.g. process information contained in signal packets) to determine the position coordinates of the tip  56  in 3-D space, including both location and orientation coordinates. The location data can include points in 3-D space, strength of the magnetic field and a time stamp. The processor  40  may be also used to implement any portion of the methods for locating a tool in a 3D space described herein, such as determining the availability of location data and accelerometer data, determining the location of the tool  22  based on the location data, estimating the location of the tool  22  based on accelerometer data and previously calculated data (e.g., velocity and acceleration data), filtering (e.g., via a Kalman filter) estimated location data and generating the display information  52 , which may be shown on a display  50 . 
     The method of position sensing described hereinabove is implemented in the CART mapping system produced by Biosense Webster Inc., of Diamond Bar, Calif., and is described in detail in the patents and the patent applications cited herein. 
     The magnetic field location sensor  38  transmits a signal to the control console  24  which indicates the location data of the tool  22  (e.g., location coordinates of the tip  56 ) in 3-D space. The magnetic field location sensor  38  may include one or more miniature receiving coils and may include multiple miniature coils oriented along different axes. Alternatively, the magnetic field location sensor  38  may include another type of magnetic sensor or position transducers of other types, such as impedance-based or ultrasonic location sensors. Although  FIG.  1    shows the tool  22  having a single location sensor, embodiments may include tools with more than one location sensor. Magnetic position tracking techniques are described, for example, in U.S. Pat. Nos. 5,391,199, 5,443,489, 6,788,967, 6,690,963, 5,558,091, 6,172,499 6,177,792, whose disclosures are incorporated herein by reference. 
     The tool  22  may also include an electrode  48  coupled to the tip  56  and configured to function as an impedance-based position transducer. Additionally or alternatively, the electrode  48  may be configured to measure a certain physiological property, for example the local surface electrical potential (e.g., of cardiac tissue) at one or more locations. The electrode  48  may be configured to apply RF energy to ablate endocardial tissue in the heart  26 . 
     The processor  40  may be included in a general-purpose computer, with a suitable front end and interface circuits for receiving signals from the tool  22  and controlling the other components of the control console  24 . The processor  40  may be programmed, using software, to perform the functions that are described herein. The software may be downloaded to the control console  24  in electronic form, over a network, for example, or it may be provided on non-transitory tangible media, such as optical, magnetic or electronic memory media. Alternatively, some or all of the functions of the processor  40  may be performed by dedicated or programmable digital hardware components. 
     In the example shown at  FIG.  1   , the control console  24  is connected, via cable  44 , to body surface electrodes  46 , each of which are attached to patient  28  using patches (e.g., indicated in  FIG.  1    as circles around the electrodes  46 ) that adhere to the skin of the patient. In addition or alternative to the patches, body surface electrodes  46  may also be positioned on the patient using articles worn by patient  28  which include the body surface electrodes  46  and may also include one or more position sensors (not shown) indicating the location of the worn article. For example, body surface electrodes  46  can be embedded in a vest that is configured to be worn by the patient  28 . During operation, the body surface electrodes  46  assist in providing a location of the tool (e.g., catheter) in 3-D space by detecting electrical impulses generated by the polarization and depolarization of cardiac tissue and transmitting information to the control console  24 , via the cable  44 . The body surface electrodes  46  can be equipped with magnetic location tracking and can help identify and track the respiration cycle of the patient  28 . 
     Additionally or alternatively, the tool  22 , the body surface electrodes  46  and other sensors (not shown) may communicate with the control console  24  and one another via a wireless interface. For example, U.S. Pat. No. 6,266,551, whose disclosure is incorporated herein by reference, describes, inter alia, a wireless catheter, which is not physically connected to signal processing and/or computing apparatus and is incorporated herein by reference. Rather, a transmitter/receiver is attached to the proximal end of the catheter. The transmitter/receiver communicates with a signal processing and/or computer apparatus using wireless communication methods, such as IR, RF, Bluetooth, or acoustic transmissions. 
     During the diagnostic treatment, the processor  40  may present the display information  52  and may store data representing the information  52  in a memory  58 . The memory  58  may include any suitable volatile and/or non-volatile memory, such as random access memory or a hard disk drive. The operator  30  may be able to manipulate the display information  52  using one or more input devices  59 . Alternatively, the medical system  20  may include a second operator that manipulates the control console  24  while the operator  30  manipulates the tool  22 . It should be noted that the configuration shown in  FIG.  1    is exemplary. Any suitable configuration of the medical system  20  may be used and implemented. 
       FIG.  2    is a block diagram illustrating example components of an example medical system  200  in which features described herein can be implemented. As shown in  FIG.  2   , the system  200  includes tool  202 , processing device  204  and display device  206 . The display device  206  (e.g., display  50  in  FIG.  1   ) may be in wired communication, wireless communication or a combination of wired and wireless communication, via one or more networks (e.g., the Internet, a local area network (LAN), or a wide area network (WAN)) with processing device  204 . Display device  206  may include one or more displays each configured to display different information, such as the location of the tool over time and maps of patient anatomy (e.g., map of a patient heart). 
     As shown in  FIG.  2   , processing device  204  includes processor  214 , memory  212  (e.g., for storing information and instructions to be executed by processor  214 ) and storage  220  (e.g., a hard disk or a removable media drive). The processing device  204  and display device  206  may, for example, be part of the exemplary control console  24  shown in  FIG.  1   . 
     As shown in  FIG.  2   , tool  202  includes sensors  216 . Sensors  216  may include one or more sensors (e.g., magnetic field location sensor  38  shown in  FIG.  1    or sensors  316  shown in  FIG.  3   ) for providing location signals to indicate the location of the tool  202  in 3-D space. As shown in  FIG.  2   , the system  200  may also include additional sensors  210 . The additional sensors  210 , which may include one or more sensors separate from the tool  202 , such as surface electrodes  46  as shown in  FIG.  1   , for providing location signals indicating the location of the tool  202  in 3-D sp ace. 
     As shown in  FIG.  2   , processing device  204  includes processor  214 , which may include one or more processors. Processor  214  may process electromagnetic signals, record electromagnetic signals over time, filter electromagnetic signals, and generate and combine electromagnetic signal information, provide information for display and control display device  206  for displaying information on display device  206 . Processor  214  may generate and interpolate mapping information for displaying maps of the heart on display device  206 . Processor  214  may process the location information acquired from one or more sensors (e.g., one or more additional sensors  210  and one or more tool sensors  216 ) to determine location and orientation coordinates of the tool  202  (e.g., a tip portion of the tool). 
     Processor  214 , which is in communication with memory  212 , may be used to implement any portion of the methods for locating a tool in a 3D space described herein. For example, processor  214  may calculate the velocity and acceleration data based on signals acquired via sensors  216  and estimate location data based on the velocity and acceleration data. In addition, processor  214  may determine whether location data, obtained at the tool  202 , which corresponds to a location of the tool  202 , is available for processing. If the location data is available, processor  214  provides the location data for displaying the location of the tool  202 . If the location data is not available, processor  214  estimated location data, corresponding to an estimated location of the tool  202 , based on the calculated velocity and an acceleration of the tool  202 , and provides (e.g., to a display processor or to the display device  206 ) the estimated location data for displaying the location of the tool  202  according to the estimated location. Processor  214  may also drive display device  206  to display the location of the tool  202 . 
     In some embodiments, tool  202  may include an accelerometer  208 , which is shown in phantom in  FIG.  2   , for detecting the acceleration of the tool  202  over time. In some embodiments, tool  202  may also include a processor  218 , which is also shown in phantom in  FIG.  2   . 
     Processor  218  may be used to perform one or more functions that are performed by processor  214 . For example, processor  218  may be used to calculate the velocity and acceleration data of the tool  202  based on signals acquired via sensors  216 . The calculated velocity and acceleration data may then be transmitted to the processing device  204 . The processing device  204  may then determine the estimated location based on the velocity and acceleration data calculated by processor  218  at the tool  202 . Processor  218  may also be used to generate estimated location data, corresponding to an estimated location of the tool  202  based on the calculated velocity and acceleration data, and transmit the estimated location data to the processing device  204 . The velocity and acceleration data and the estimated location data can be transmitted from the tool  202  to processor  214  using any of a number of short range wireless transmission protocols. 
     The accelerometer  208 , processor  218 , sensors  216  and additional sensors  210  shown in  FIG.  2    may be in wired or wireless communication with processing device  204 . Display device  206  may also be in wired or wireless communication with processing device  204 . 
       FIG.  3    is an illustration of an example wireless tool  300  for use with embodiments described herein. As shown in  FIG.  3   , tool  300  includes accelerometer  208  and processor  218 . Wireless tool  300  includes a handle portion  302  and a probe portion  304 . Probe portion  304  includes a tip  306  and sensors  316  disposed at different locations on the probe portion  304 . As shown in  FIG.  3   , the accelerometer  208  and processor  218  is disposed at the handle portion  302  of the wireless tool  300 . The size and shape of tool  300  shown in  FIG.  3    is merely exemplary. In addition, the location of each component (e.g., sensors  216 , accelerometer  208  and processor  218 ) shown in  FIG.  3    is also exemplary. 
     The handle portion  302  is configured to be held by medical personnel for maneuvering the tool in 3-D space. The probe portion  304  is configured to be inserted into a patient during a medical procedure. As shown in  FIG.  3   , the handle portion  302  is attached to the probe portion  304 . The sensors  316  are, for example, used to determine the location of the tool  300  and may include an inductor (not shown) and resistors (not shown) for transmitting signals (e.g. voltage) to a processor (e.g., processor  214  in  FIG.  2   ) remote from the tool  300 . The number of sensors  316  shown in  FIG.  3    is by way of example. Embodiments include tools having any number of sensors, including one sensor, disposed at any number of tool locations. 
     The accelerometer  208 , processor  218  and sensors  316  may be in wired or wireless communication with a processing device remote from the tool  300 , such as processing device  204  shown in  FIG.  2   . 
       FIG.  4    is a flow diagram illustrating an example method  400  of locating the tool in 3-D space. As shown in block  402 , the method  400  includes obtaining location data which corresponds to a location of a tool (e.g., tool  202 ) in 3D space over time. The location data may be obtained at the tool using one or more sensors (e.g. magnetic field location sensor  38  shown in  FIG.  1   , or sensors  216  shown in  FIG.  2   ) disposed at the tool. The location data includes, for example, locations (e.g., points, coordinates) in the 3-D space, the strength of the magnetic data, times at which data is acquired (e.g., time stamps), and any other information indicating a location of the tool in the 3D space over time. 
     As shown in  FIG.  4   , the method  400  includes calculating the velocity and the acceleration of the tool, at block  404 , and estimating the location of the tool, at block  406 . The velocity and acceleration may be calculated at the tool or remote from the tool. In addition, the location of the tool may be estimated at the tool or remote from the tool. 
     For example, in one embodiment, the location data, obtained at the tool, may be transmitted from the tool and the velocity and the acceleration of the tool may be calculated remote from the tool (e.g., via processor  214 ) using the received location data. The location of the tool may then be estimated remote from the tool (e.g., via processor  214 ) from the calculated velocity and the acceleration. In another embodiment, the velocity and the acceleration of the tool may be calculated at the tool (e.g., via processor  218 ) using the obtained location data. The calculated velocity and acceleration may then be transmitted from the tool and the location of the tool may be estimated remote from the tool (e.g., via processor  214 ) from the calculated velocity and the acceleration calculated at the tool. In yet another embodiment, the velocity and the acceleration of the tool may be calculated at the tool and the location of the tool may be estimated at the tool. The estimated location of the tool may then be provided remote from the tool to be displayed. 
     In an example embodiment, the velocity of the tool is calculated using a change in location and a change in time. For example, assume that “x” is a previously acquired position of a tool acquired from block  402 . A first velocity V 1  may be calculated using the Equation 1:
 
 V   1 =( x   3   −x   2 )/ dt   (Equation 1)
 
     A second velocity, V 2  may be calculated using Equation 2:
 
 V   2 =( x   2   −x   1 )/ dt   (Equation 2)
 
where, “x 1 ,” “x 2 ,” and “x 3 ” are previously acquired positions of the tool at different times based on the location data obtained at block  402 , and dt is the change in time between when two positions of the tool were acquired.
 
     The acceleration may then be calculated (e.g., via processor  218  or  214 ) using two previously calculated velocities (e.g., V 1  and V 2 ) of the tool. For example, an acceleration “a” of the tool may be calculated using Equation 3:
 
 a =( V   2   −V   1 )/ dt   (Equation 3)
 
     The calculated velocity and acceleration of the tool may then be used to estimate a location of the tool, at block  406 . For example, the estimated location of the tool may be calculated using the sum of a previous location, a calculated velocity and a calculated acceleration, such as Equation 4:
 
 x=x   0   +V   0   t+a   0 (( t*t )/2)  (Equation 4)
 
     The equations described above, used to calculate the velocity and acceleration and estimate the location, are merely used as an example. 
     The location data, obtained via the magnetic fields, is continually obtained over time such that location data, corresponding to a plurality of locations of the tool at different times, is obtained. The velocity and acceleration of the tool are also continually calculated for locations over time. As shown at block  406 , estimated location data is determined based on the continually calculated velocity and acceleration. For example, blocks  402 - 406  may be repeated, at equal intervals (e.g., 5 millisecond intervals), to continually estimate the location of the tool at the different locations over time. Each of blocks  402 - 406  may be repeated together (i.e., at the same equal intervals) or separate and independent from each other (i.e., at different intervals). Blocks  402 - 406  may also be repeated at unequal intervals, or performed upon the occurrence of an event or upon request. 
     As shown at block  408  of  FIG.  4   , a determination is made as to whether location data (e.g., most recently obtained location data corresponding to the location of the tool), obtained from block  402 , is available for processing (e.g., processing by processor  214  or  218 ). That is, a determination is made as to whether location data, obtained via the magnetic fields, is available. If the location data is determined to be available, the location data is provided (e.g., to a display, a display processor, speaker), for presentation at block  410  and the location of the tool is presented (e.g., visually displayed, aurally presented, or any other known method of presenting information) at the location indicated by the location data. After the location of the tool is provided at block  410 , the method proceeds back to block  402 . 
     Location data may be determined not to be available for a variety of reasons. For example, location data may not be available if location signals (e.g., signals from magnetic field location sensor  38 ) are not received, if location signals are not strong enough to obtain information or the location data is determined to be inaccurate. 
     If the location data is determined not to be available at block  408 , an estimation of the tool&#39;s location is performed. As shown in block  412 , a determination is made as to whether accelerometer data is available for processing (e.g., by processor  214  or  218 ). The accelerometer data may not be available for a variety of reasons. For example, the accelerometer data may not be available if the tool is not equipped with an accelerometer, if the signals are not received, strong enough to acquire information end accelerometer data, or the accelerometer data is determined to be inaccurate. 
     As shown at block  414 , if it is determined that the accelerometer data is not available, the data calculated at block  404  (e.g., one or more calculated accelerations) and the estimated location data determined at block  406 , is obtained (e.g., from the tool or from memory  212  or storage  220 ). The location of the tool estimated from the relative velocity and acceleration (i.e., time when one or more velocities and accelerations are calculated relative to the current estimation), is used at block  418  to estimate the location (e.g., the current location) of the tool. That is, in the example shown at  FIG.  4   , estimated location data of the tool is continually generated over time (e.g., at equal intervals) at block  406 , based on the calculated velocity and acceleration of the tool at block  404 , prior to determining whether the location data is available at block  408 . 
     In another example, estimated location data of the tool is generated if it is determined that the location data is not available. In this example, the calculated velocity and acceleration is obtained at  414  and then the estimated location data is generated using the relative velocity and acceleration. 
     If the accelerometer data is determined to be available, the accelerometer data is obtained at block  416  and the relative acceleration data of the accelerometer data obtained from the accelerometer is used to estimate the location of the tool at block  418 . 
     One or more previous velocity calculations performed in block  404  and one or more previous acceleration calculations, or accelerometer data, may be used to estimate the location of the tool. For example, more recently (e.g., most recent) obtained velocity data, acceleration data and accelerometer data is used to estimate the location of the tool. In addition to or alternative to the more recently obtained data, other data prior to the more recently obtained data may be used, for example, because the more recent data may be inaccurate, include errors in calculation or may not be processable (e.g., signal including the data is not strong enough or signals are not received). 
     As shown in block  420 , a filter may be applied to the relative velocity and acceleration, obtained at block  418 , to estimate the location of the tool. In one exemplary embodiment, a Kalman filter is used. For example, Equation 5 may be used to estimate the location of the tool:
 
 Pk=P ( k− 1)+ dtV ( k− 1)+1/2* adt{circumflex over ( )} 2  (Equation 5)
 
where, the location of the tool at a relative time “Pk” is based on the location at a prior relative time “k−1”, the velocity at a relative time “(V(k−1))” and a change in time of the acceleration of the tool “adt.”
 
     As shown at block  422 , the estimated location data, corresponding to an estimated location of the tool, is provided (e.g., to a display, a display processor, speaker) for presentation and the location of the tool is presented (e.g., visually displayed, aurally presented, or any other known method of presenting information) at the location indicated by the location data. After the estimated location of the tool is provided at block  422 , the method proceeds back to block  402 . 
     Any of the functions and methods described herein can be implemented in a general purpose computer, a processor, or a processor core. Suitable processors include, by way of example, a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), and/or a state machine. Such processors can be manufactured by configuring a manufacturing process using the results of processed hardware description language (HDL) instructions and other intermediary data including netlists (such instructions capable of being stored on a computer readable media). The results of such processing can be maskworks that are then used in a semiconductor manufacturing process to manufacture a processor which implements features of the disclosure. 
     Any of the functions and methods described herein can be implemented in a computer program, software, or firmware incorporated in a non-transitory computer-readable storage medium for execution by a general purpose computer or a processor. Examples of non-transitory computer-readable storage mediums include a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). 
     It should be understood that many variations are possible based on the disclosure herein. Although features and elements are described above in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements.