Location sensing system and method

Abstract

Determining the position of multiple medical devices and / or their instruments during a medical procedure. [Solution] A positioning system is disclosed which is adapted to determine the position of a medical device / instrument from position signals acquired by at least a first and second signal acquisition device that sample outputs from different position sensors of a medical device and transmit them in packets. The system includes a calibration signal generator which is connectable to each of the acquisition devices and generates a calibration signal whose frequency is switched between a plurality of frequencies. A synchronization processor processes simultaneous packets containing the calibration signals sampled by the first and second acquisition devices, thereby determining synchronization parameters for synchronizing position signals sampled by different acquisition devices.

Description

[Technical Field]

[0001] The present invention relates to the field of medical devices, and more particularly to determining the position of multiple medical devices and / or their instruments during a medical procedure. [Background technology]

[0002] In a wide range of medical procedures, multiple medical devices are used on and / or inside a patient's body. These medical devices may be, for example, one or more catheters, and often a single catheter includes multiple parts / sections, which may be, for example, one or more flexible sections (such as its flexible arms / splines) and / or medical instruments that can be distributed on the flexible sections (e.g., sensors / probes, electrodes such as EEG electrodes, ablation devices, and / or other instruments). During medical procedures, it is often desirable to track the location of multiple medical devices / catheters and / or multiple flexible sections of a medical device that can be bent / curved to approach / contact (sens / treat) different parts of the patient's anatomical structure. One medical procedure in which the use of catheters containing multiple catheters and / or multiple flexible sections / parts has proven extremely useful is in the treatment of cardiac arrhythmias. Cardiac arrhythmias and atrial fibrillation, in particular, remain dangerous medical conditions that are common, especially in the elderly population.

[0003] Diagnosis and treatment of cardiac arrhythmias include mapping the electrical properties of cardiac tissue, particularly the endocardium and cardiac volume, and selectively ablating cardiac tissue by applying energy. In many cases, such procedures involve inserting one or more catheters, each having multiple parts such as flexible sections / splines, into the patient's body. In some cases, medical devices positioned in multiple parts are operated to perform multiple interrelated actions, such as electrocardiogram (ECG) mapping, tissue ablation, temperature sensing / mapping, and / or imaging / ultrasound sensing. Some catheters are designed specifically for placement in particular parts of anatomical structures, e.g., cardiac chambers, coronary sinuses, esophagus, atria, and ventricles, and contain multiple flexible sections / parts that can conform to the shape of the anatomical structure of the body part being treated, and optionally have multiple devices positioned in different parts. [Brief explanation of the drawing]

[0004] To better understand the subject matter disclosed herein and to illustrate how it can actually be put into practice, embodiments are described here by non-limiting examples with reference to the accompanying drawings. [Figure 1] This is a schematic diagram of a catheter 14A having multiple parts / medical devices at its distal end, and a position sensor associated with it. [Figure 2] This is a schematic diagram showing a catheter-based mapping and ablation system 10 according to one embodiment of the present invention. [Figure 3] This is a block diagram showing the configuration of a positioning system 100 according to a simplified model. [Figure 4A] This flowchart illustrates a method 200 for determining the positions of multiple position sensors in one or more medical devices connected to different (e.g., first and second) signal acquisition devices, according to embodiments of the present invention. [Figure 4B]This is a flowchart of a synchronization method 250 used in some embodiments of method 200 in Figure 4A to determine synchronization parameters and thereby synchronize between the signal outputs of position sensors of one or more medical devices sampled / acquired by different (e.g., first and second) signal acquisition devices.

[0005] In the drawings, similar reference numerals are used to indicate similar modules / elements of the present invention, or elements / modules having similar functions. Therefore, unless otherwise specified, descriptions of modules / elements relating to specific embodiments of the present invention should be understood to apply to all embodiments of the present invention in which such modules / elements are incorporated. [Modes for carrying out the invention]

[0006] With advances in medical technology, the number of medical devices and instruments involved in medical procedures, placed in or moved within a patient's body, has increased significantly. For example, in some medical procedures, two or more catheters, such as intracardiac ECG mapping catheters and / or ablation catheters, are used simultaneously in the same procedure. Furthermore, some catheters may have multiple movable / flexible sections (e.g., splines) on which medical instruments are used. The term medical instrument is used herein to encompass medical devices and / or parts / parts of medical devices that provide specific medical functions, such as exploring / sensing and / or treating a particular medical condition. For example, medical instruments are often located on various movable / flexible sections of the distal end of a catheter, such as shafts, distal end effectors, and splines, and / or various other sections of its distal end effector. The movable / flexible sections of a catheter can be adapted to bend / expand during a medical procedure (e.g., to accommodate the volume of an anatomical structure of the body being treated / monitored, and / or to bring the medical instrument on it into contact with or close to the wall / boundary of an anatomical structure of the body being treated / monitored). Such techniques are used, for example, to enable the mapping and / or treatment of several tissue regions of an anatomical structure substantially simultaneously. For this purpose, numerous medical devices, such as ECG electrodes, ablation utilities / instruments, or other devices, can be placed on multiple movable / flexible sections of a catheter and may be used, for example, by a physician to simultaneously capture / map electrical activity from multiple locations within the cardiac chambers and / or to simultaneously ablate those specific tissue regions.

[0007] Figure 1 shows a perspective view illustrating such a medical device 14, in this non-limiting case, an ablation catheter 14A. The ablation catheter 14A includes a distal end 28 of a shaft / body 29 having multiple medical instruments 26 in its distal end portion / region 28. In this particular example of a multi-instrument catheter, the distal end 28 includes multiple flexible sections 22 (hereinafter also called splines) to which multiple position sensors 34 (typically at least one sensor located on the shaft 29 and several sensors located on the splines 22 from the inside) are positioned / connected at multiple locations. In this non-limiting case, the flexible sections 22 are connected to each other in a “basket”-like configuration.

[0008] The distal end 28 includes a plurality of medical devices 26 (e.g., ablation electrodes in this particular non-limiting example). The medical devices 26 or some of them are positioned on a flexible section 22 that forms an expandable assembly which may be deflected outward from the catheter 14A (e.g., by moving a pusher rod) so that the medical devices 26 can be moved to approach / contact the tissue wall of the heart for ablation of a desired area of ​​tissue. The position of at least some of the medical devices 26 can be tracked based on location signals sensed by position sensors 34. For clarity, below the term distal end portion of medical device / catheter is used to specify a part / element / section of medical device located on the distal end 28 of medical device / catheter whose position should be determined during a medical procedure. In this regard, it should be understood that the term distal end portion may encompass any one of the position sensors 34 that can provide data / signals indicating the position of the shaft / body 29 of the medical device, the medical devices 26 on its flexible / movable section 22 if present thereto, and / or any of these elements. The term "position" is used herein to specify the location, orientation, or both of the location, orientation, or orientation of a medical device and / or medical instrument or other distal end portion. For example, in some cases, it may not be necessary to determine the location of a medical device or medical instrument, only its orientation, or vice versa, and the system of the present invention may be adapted / operable to achieve the same.

[0009] Catheter 14A (shown in Figure 1) presents a non-limiting example of a multi-device medical device. Other medical devices that can be used in the present invention include, for example, other catheters (with or without a flexible / movable section) that may have one or more medical devices on them, such as an intracardiac electrogram (IEGM) sensing catheter such as 14B illustrated in Figure 2, which includes an IEG sensing catheter in which a medical device 26 includes a near-field intracardiac electrogram sensor / electrode positioned on a flexible / movable section 22.

[0010] To accurately perform medical procedures involving multiple medical devices / instruments, the positions of these devices / instruments should be monitored / tracked within the patient's anatomical structure. In particular, their relative positions to each other should often be precisely determined. A position sensor 34 of a medical device 14 can receive location signals (e.g., electromagnetic / magnetic signals), thereby determining the position of each of them and / or the positions of its multiple medical instruments 26. Thus, valuable information regarding the positions of different medical devices 14 and / or their instruments 26, especially their relative positions to each other, can be determined and provided / presented to the physician during the medical procedure (e.g., in real time).

[0011] Therefore, there is a need in the art for systems and methods that enable the determination of the position of a number of position sensors positioned on one or more distal end portions of one or more catheters or other medical devices. Conventional hardware for determining the position of medical devices / instruments is often limited in the capacity of the number of position sensors that can be used to determine the position. For this purpose, conventional hardware for medical device position sensing is generally not suitable for connecting to medical devices such as catheters that have a relatively large number of position sensors whose position needs to be determined. In fact, conventional hardware typically includes a transmitter for transmitting location signals that can be received by multiple position sensors of such catheters or other medical devices, but has limited channels for collecting received location signals sensed by multiple position sensors of such devices and cannot accommodate simultaneous processing of location signals provided from a number of position sensors embedded in some types of advanced medical devices such as spline or basket catheters.

[0012] The present invention provides novel systems and methods for solving these problems. The technology of the present invention facilitates the extension of the capabilities of existing medical device positioning hardware to enable the determination of the positions of multiple distal end portions of medical devices / medical instruments (e.g., simultaneously) by selectively utilizing and synchronizing with location signals collected through channels of conventional medical device positioning hardware that may already be in use / deployed in an operating room (e.g., eliminating the need to replace or decommission existing hardware). Advantageously, the present invention facilitates the positioning of a relatively large number of position sensors that may not be facilitated by conventional already deployed positioning hardware without the need to replace existing location signal transmitters in use, without transmitting additional location signals, and without replacing existing position signal acquisition devices. The technology of the present invention facilitates the extension of the number of position signal acquisition channels of already deployed positioning hardware by adding additional signal acquisition devices that can acquire position signals from additional position sensors while operating in synchronization with existing / already deployed position signal acquisition devices. Thus, the positions of numerous medical instruments can be determined in a cost-effective manner during medical procedures without overcrowding medical facilities with additional electromagnetic signals and without expensive replacement of existing devices.

[0013] Refer to Figure 2, which shows an exemplary catheter-based mapping and ablation system 10 deployed in a medical operating room. The system 10 includes a positioning system 100 according to the present invention, which includes or is connectable to a plurality of medical devices 14, such as catheters 14A and 14B, and the positions of the device and / or its various medical instruments 26 should be determined by the positioning system 100.

[0014] During surgery, one or more of the medical devices (e.g., catheters) 14 may be percutaneously inserted by a physician 24 into a cardiac chamber or vascular structure of the heart 12 via the patient's vascular system. Typically, the delivery sheath catheter is inserted into the left or right atrium near the desired location in the heart 12. One or more of the medical devices 14 can then be inserted into the delivery sheath catheter to reach the desired location within the heart 12. The physician 24 may position the distal end 28 of either of the medical devices / catheters 14 so that the medical instrument 26 approaches / contacts the heart wall to explore / treat a target site within the heart 12 (if the medical instrument 26 is positioned on a flexible / movable section 22, the latter can be moved / bent to become the medical instrument 26 to contact tissue). For example, as described above, the system 10 may include a dedicated medical device / catheter 14B for sensing intracardiac electrogram (IEGM) signals and a dedicated medical device / catheter 14A for tissue ablation. It should be understood that the system 10 of the present invention is not limited to the specific medical devices 14A and 14B shown in the figure, and may be implemented with additional and / or other medical devices, such as catheters dedicated to both sensing and ablation, and / or medical devices serving other purposes such as imaging.

[0015] System 10 may also include a recorder 11 adapted to record and display electrocardiograms 21 captured by surface electrocardiogram (ECG) electrodes 18 and intracardiac electrocardiograms (IEGM) captured by ECG electrodes of a medical device / catheter such as 14B (e.g., instrument 26), which are adapted to sense IEG signals. The recorder 11 may include pacing capability for pacing the rhythm of the heart and / or may be electrically connected to a standalone pacer. System 10 may also include an ablation energy generator 50 adapted to conduct ablation energy to one or more electrodes at the distal end of a medical device / catheter such as 14A configured for ablation. The energy generated by the ablation energy generator 50 may include, but is not limited to, radiofrequency (RF) energy or pulsed-field ablation (PFA) energy, or a combination thereof, including unipolar or bipolar high-voltage DC pulses that can be used to induce irreversible electroporation (IRE).

[0016] Often, in the case of medical devices including complementary medical devices 26, such as medical devices for IEGM sensing and tissue ablation (for example, as in the example of 14B and 14A), it may be important to accurately determine the relative positions of the medical devices 26 (e.g., those with different functions) in order to enable precise tissue ablation (e.g., by device 14A) in a specific area where an abnormal IEGM has been sensed (e.g., by device 14B).

[0017] A magnetic-based position sensor 34 located on the distal end 28 of the medical device / catheter 14A and 14B may operate to provide data indicating the real-time position of the distal end portion 35 of the catheter during a medical procedure. The magnetic-based position sensor 34 operates in conjunction with a location pad 25 which includes multiple location signal transmitters 32 (e.g., magnetic coils) that generate / transmit electromagnetic location signals (e.g., magnetic fields) within a predetermined working volume surrounding the patient. The position of the distal end 28 and / or its distal end portion 35 of the catheter 14A or 14B may then be tracked (e.g., in real time) based on electromagnetic location signals generated using the location pad 25 and sensed by the magnetic-based position sensor 34. The position of other types of medical devices (e.g., catheters having only a single distal end portion or a single medical instrument inside) and / or other types of medical devices may also be tracked by the system 10. Details of magnetic-based position sensing technology are described in U.S. Patents No. 5,391,199, No. 5,443,489, No. 5,558,091, No. 6,172,499, No. 6,239,724, No. 6,332,089, No. 6,484,118, No. 6,618,612, No. 6,690,963, No. 6,788,967, and No. 6,892,091.

[0018] System 10 typically includes a patient interface unit (PIU) 30, which is an interface configured to establish electrical communication between medical devices such as catheters and / or other electrophysiological devices and a workstation 55 for controlling the operation of System 10. The medical devices of System 10 may include, for example, one or more catheters 14, a location pad 25, a surface ECG electrode 18, an electrode patch 38, an ablation energy generator 50, and an electrophysiological device such as a recorder 11. The workstation 55 includes memory, a processor unit having memory or storage device in which appropriate operating software is stored, and user interface functions. The workstation 55 may optionally provide several functions, including (1) modeling the endocardial anatomical structure in three dimensions (3D) and rendering the model or anatomical map 20 for display on the display device 27; (2) displaying the activation sequence (or other data) compiled from the recorded electrophoresis diagram 21 on the display device 27 as a representative visual representation or image superimposed on the rendered anatomical map; (3) displaying the real-time location and orientation of multiple catheters within the cardiac chambers; and (4) displaying areas of interest, such as the locations where ablation energy has been applied, on the display device 27. One commercially available product embodying the elements of System 10 is available as the CARTO® 3 System, commercially available from Biosense Webster, Inc., 31A Technology Drive, Irvine, CA, 92618.

[0019] As described above, typically the PIU30 implements processing capabilities to implement real-time calculation of the location of a portion of a medical device / catheter 14 connected to the system 10. To achieve this, the PIU30 typically includes a location signal generation unit (e.g., a transmitter, not specifically shown in Figure 2, but 132 in Figure 3), which is connected to a location pad 25 and transmits a location signal TR (e.g., a predetermined frequency F1~F n Electromagnetic / magnetic location signals TR1~TR k These are adapted to generate and are provided to the location pad 25 so as to be sensed by the position sensor 34 of the medical device 14 and transmitted by the location pad 25. The PIU 30 also typically includes a signal acquisition device (e.g., a receiver, not specifically shown in Figure 2, but in Figure 3), which transmits the location signal TR1~TR k In response, location signals sensed by one or more of the position sensors 34 are acquired, real-time processing / preprocessing such as digitization / sampling is applied, and the signals are packaged into communication packets (optionally, preprocessing operations such as filtering and / or amplification are also applied), and the location signal packets are adapted for communication to the workstation 55.

[0020] Next, the workstation 55 is adapted to receive location signals sensed in packets from the signal acquisition device of the PIU 30, and includes a positioning utility (e.g., 190 in Figure 3, not specifically shown in Figure 2, typically implemented by software within the workstation 55) to process the sensed location signals to determine data indicating the position of the position sensor 34, thereby deriving the position of the medical device 14 or the medical instrument 26 on it. As will be understood by those skilled in the art, the position of the position sensor 34 is determined by transmitting location signals TR1~TR k Different frequencies F1~F in the sensed position signal relative to the phase of each frequency in nThe relative phase of may be determined from the sensed location signal, and optionally, different frequencies F1~F in the sensed location signal may be determined. n It may be determined with improved accuracy based on the amplitude.

[0021] However, in some implementations of system 10 (e.g., systems already deployed in medical surgical facilities), the PIU 30 may have a limited number of input channels (CH1 in Figure 3) for collecting and / or simultaneously sampling sensed location signals, and is not adapted to accommodate a sufficient number of input channels for a large number of location sensors implemented in an advanced medical device 14 having multiple medical instruments 35 whose individual positions should be determined.

[0022] Accordingly, according to the present invention, system 10 includes an additional interface unit (AIU) 31 which includes an additional number of input channels (CH3 in Figure 3) for collecting and / or simultaneously sampling sensed location signals from additional medical devices / instruments. The additional interface unit 31 is configured and operable to complement / extend the functionality of PIU 30 with additional location sensing channels (CH3 in Figure 3). The additional location sensing channels (CH3 in Figure 3) of AIU 31 allow connection of multiple location sensors to system 10, which may not be sufficiently handled by the channels of PIU 30. Thus, in some implementations / medical operations, as illustrated in Figure 3, some of the location sensors 34 of one or more medical devices (e.g., 14B) may be connected to the input channels (CH1 in Figure 3) of PIU 30, and some of the location sensors 34 of one or more medical devices (e.g., 14A) may be connected to the input channels (CH3 in Figure 3) of AIU 31. Thus, both PIU 30 and AIU 31 implement signal processing (e.g., sampling) for location signals from different location sensors.

[0023] In this regard, it should be noted that in some embodiments, the PIU 30 may be part of an already deployed system 10, and the AIU 31 may be an addition to the deployed system 10, which may be added to facilitate position sensing from additional position sensors 34 not accommodated by the PIU 30. Therefore, unless the PIU 30 and AIU 31 are synchronized with each other, the respective samplers may operate with a clock delay (clock skew) between them and / or may introduce somewhat different amplitude gains into the position signals sampled thereby. Such a lack of synchronization may make it difficult to determine the precise positions of the position sensors 34 processed by the PIU 30 and / or AIU 31. In particular, the lack of synchronization may prevent the relative positions between position sensors connected to the PIU 30 and AIU 31 (e.g., 34.1 and 34.2 in Figure 3) from being determined with sufficient accuracy. This can be problematic, for example, if the medical device 26 whose position signals are processed by PIU30 and AIU31 is a complementary device (e.g., IEGM sensing and ablation device) where relative position is important for the accurate execution of the medical procedure.

[0024] Accordingly, according to the present invention, the system 10 includes a synchronization processor and a synchronization device, which are adapted to determined synchronization parameters and synchronize between position signals sampled by different sampling utilities PIU30 and AIU31 (see, for example, Figure 3, by the signal acquisition devices 110 and 120 of PIU30 and AIU31, respectively). In the non-limiting example of Figure 2, the positioning system 100 includes PIU 30 and AIU 31, both of which implement / include their respective signal acquisition devices (110 and 120 in Figure 3) and synchronous processors and synchronous devices (150 and 160 in Figure 3). The positioning system 100 may also typically include a positioning utility (not specifically shown in Figure 2, but 190 in Figure 3), which is adapted to process position signals and thereby determine the position of the position sensor 34 or the medical device associated with it. The synchronous processor 150 and synchronous device 160, as well as the positioning utility 190, are implemented as part of the workstation 55 in the non-limiting example of Figure 2, although not specifically shown in Figure 2.

[0025] In this regard, it should be noted that the workstation 55 may be implemented by a computerized system with appropriate software installed (for example, by a general-purpose computer). To this end, advantageously, the deployment of the system 10 and / or 100 of the present invention on an already deployed medical system such as 10 that lacks a sufficient number of channels for position sensor signals may be achieved by optionally updating the software of the workstation 55 on the deployed medical system to include / implement an additional interface unit 31, a synchronization processor 150, and / or a synchronization device 160. In some embodiments, the positioning utility 190 may not require updates and may operate periodically to determine the position of the position sensor based on the synchronization signal.

[0026] For example, an additional interface unit 31 can facilitate the connection of additional medical devices such as catheters 14A and / or 14B, the position of which or some distal end portion 35 thereof (e.g., medical instrument 26) should be tracked by the system 10. Next, a synchronization processor (150 in Figure 3) is adapted to determine a synchronization parameter (SP in Figure 3) between the position signals collected / sampled by the respective signal acquisition devices (110 and 120 in Figure 3) of the PIU 30 and AIU 31, using the calibration signals sampled by them. The synchronization device (160 in Figure 3) then uses the synchronization parameter SP to synchronize between the position signals collected from the position sensors 34 by the respective signal acquisition devices (110 and 120 in Figure 3), so that the positions of the medical instruments 26 associated with each can be accurately presented in appropriate relative spatial and temporal relationships (e.g., displayed to the physician 24). The positioning utility (190 in Figure 3) utilizes the process of synchronization signals acquired from the synchronization device and is adapted to determine, based on the synchronization signals, the positions of the position sensors 34 connected to the PIU 30 and AIU 31, or the position of the distal end portion 35 of interest of the medical device 14, and to provide them to the physician on the display 27.

[0027] Next, with reference to Figures 3 and 4A, which illustrate positioning systems 100 and methods 200 according to several embodiments of the present invention, respectively. Figure 3 is a block diagram of a positioning system 100 according to one embodiment of the present invention, which may be implemented by the system 10 illustrated in Figure 2. Figure 4A shows a flowchart of a method 200 according to an embodiment of the present invention, implemented by the positioning system 100, for determining the positions of multiple position sensors 34A-34S in one or more medical devices 14. More specifically, these systems and methods provide for accurately determining the relative positions between multiple position sensors that may be connected to different (e.g., first and second) signal acquisition devices.

[0028] System 100 includes a first signal acquisition device 110 and a second signal acquisition device 120, each configured and operable to receive, sample, and pack outputs from one or more position sensors 34 via one or more respective channels, and provide the packets for further processing by System 100, which then determines the position of each sensor 34. In some embodiments, the first signal acquisition device 110 is incorporated as part of a PIU 30 of System 10, which may already be deployed in a medical facility, and the second signal acquisition device 120 is incorporated as part of an additional interface unit 31, which may be added to an already deployed System 10 to expand, at least among other things, the number of channels through which sensed position signals can be received and processed from position sensors 34 of multiple medical devices. System 100 also includes a calibration signal generator 134 adapted to generate a calibration signal CS in the form of a continuous wave (CW) whose frequency is switched between multiple frequencies. Optionally, the calibration signal generator 134 may be incorporated as part of an additional interface unit 31. As will be described in more detail below, the calibration signal CS helps to synchronize the outputs (sensed position signals) RS1 and RS2 of one or more position sensors 34.1 and 34.2, respectively, which are received by the first signal acquisition device 110 and the second signal acquisition device 120, respectively. For this purpose, system 100 also includes a synchronization processor 150 adapted to utilize the calibration signal CS to determine a synchronization parameter SP for synchronizing between the sensed position signals RS1 and RS2, which are sampled and packed by the two signal acquisition devices 110 and 120, respectively. System 100 further includes a synchronization device 160 that synchronizes the position signals RS1 and RS2 acquired by the first signal acquisition device 110 and the second signal acquisition device 120 according to the synchronization parameter SP and generates a synchronized position signal SS.System 100 also includes a positioning utility 190 adapted to process a synchronous position signal SS to determine the relative position of the position sensors 34 (e.g., synchronized with each other regardless of the specific acquisition devices 110 and / or 120 from which they are sampled and packed). The relative position may be the simultaneous position of position sensors 34.1 and 34.2 and / or their positions at different times (e.g., at a first time point, one medical device, e.g., 14B, is to acquire IEGM measurements from one or more locations, and at another time point, a second medical device, e.g., 14A, is to operate to ablate a specific location among these locations). In some embodiments, the positioning utility 190 is further adapted to stream data indicating the simultaneous / relative position of the position sensors 34 and / or associated medical instruments 26 to a display 27 of System 10. In some embodiments, a synchronous processor 150 and / or synchronous device 160 is incorporated as part of a workstation 55 of System 10, which may already be deployed in the medical facility. In some implementations, the positioning utility 190 is also integrated as part of the workstation 55.

[0029] In a specific non-limiting example in Figure 3, the system 100 is shown connected to several medical devices, including 14A and 14B, and optionally to 14C and 14D. Medical devices 14A, 14C, 14B, and 14D optionally include a plurality of position sensors 34A through 34K, 34L, 34M through 34R, and 34S, respectively. In this example, the outputs of one or more position sensors 34M through 34R and 34S, collectively referred to herein as the first position sensor 34.1, are respectively connected via a first input channel CH1 to a first signal acquisition device 110 (e.g., of PIU 30) (e.g., these first channels are typically associated with the respective input ports of PIU 30). The first signal acquisition device 110 is also connected via a second channel CH2 (e.g., a channel associated with another input port of PIU 30) to a calibration signal generator 134 to receive a calibration signal CS. Optionally, in some embodiments, the PIU30 having the first signal acquisition device 110 as described above is an already deployed module of the system 10, which was not pre-designed to be connected to the calibration signal generation unit 134. Thus, in such embodiments, the second channel CH2 to which the calibration signal generation unit 134 is connected is one of the existing channels of the first signal acquisition device 110, which may have been originally designed to receive the output of a particular position sensor.

[0030] In this example, the outputs 34K and 34L from one or more position sensors 34A, collectively referred to herein as the second position sensor 34.2, are connected, respectively, to the second signal acquisition device 120 (e.g., of an additional interface unit 31) via a third input channel CH3 (for example, these third channels are typically associated with the respective input ports of the additional interface unit 31). The second signal acquisition device 110 is also connected to a calibration signal generator 134 via a fourth channel CH4 to receive a calibration signal CS. Optionally, as described above, the additional interface unit 31 includes both the second signal acquisition device 120 and the calibration signal generator 134, and therefore the fourth channel CH4 connecting them may be an internal channel of the additional interface unit 31 and may not be associated with an external input port of the additional interface unit 31, for example.

[0031] It will be understood that the number of medical devices 14 connected to the system and the number of position sensors contained in each are provided herein only as non-limiting examples. For example, system 100 may be connected to multiple medical devices, each having only one position sensor, or each having multiple position sensors.

[0032] The operation of system 100 will be described in more detail with reference to method 200 for determining the position of a medical device or a part thereof, for example, a medical instrument on it, or the position of the part thereof to which the position sensor 14 is connected, according to one embodiment of the present invention shown in Figure 4A. Method 200 particularly facilitates the synchronization between the position signals of the first position sensor 34.1 and the position signals of the second position sensor 34.2, thereby determining their respective simultaneous / relative positions, or the respective simultaneous / relative positions of medical instruments 26 associated with or inferred from them, and presenting them accurately to the physician 24 (for example, on the display 27).

[0033] Optionally, before method 200, the signal sampling rate of at least one of the first signal acquisition device 110 and the second signal acquisition device 120 is adjusted (equalized) so that the signal sampling rates of the first signal acquisition device 110 and the second signal acquisition device 120 are substantially equal. In some embodiments, this operation is performed, for example, by an optional pre-rate controller 121 that may be included in one of the signal acquisition devices, or may be included in the second signal acquisition device 120 that may be added to the already deployed system 10, for example. In this regard, it should be noted that the first signal acquisition device 110 and the second signal acquisition device 120 are each associated with their respective first signal clock CLK1 and second signal clock CLK2, whereby their respective sampling rates are determined. The PIU 30 (of the already deployed system 10, for example) typically includes the first signal acquisition device 110 and the location signal generation unit 132, and the first signal clock CLK1. The first signal clock CLK1 is used both to adjust / determine the sampling rate of the first signal acquisition device 110 and to control the generation of the location signal TR transmitted by the location signal generation unit 132 to be generated at predetermined frequencies F1 to Fn relative to / based on the rate of the first signal clock CLK1. Thus, in some embodiments, the pre-rate controller 121 determines the rate R1 of the first signal clock CLK1 using one or more of the sensed location signals RS2 received via channel CH3. The pre-rate controller 121 of the second signal acquisition device 120 processes the second signal clock CLK2 and, based thereon, processes one or more of their received signals and, based on the rate R2 of the second signal clock CLK2, the received frequencies F r 1 to F r nThe process determines one or more of the following. The process may include spectral analysis of one or more of those received signals (for example, by Fast Fourier Transform, FFT, and / or any other spectral analysis process that can be considered more appropriate / efficient for this purpose by those skilled in the art). The pre-rate controller 121 determines the received frequency F with respect to the rate R2 of the second signal clock CLK2. r 1~F r n at least one of the receiving frequencies F r i The transmitted signal TR uses a predetermined frequency F1~F that utilizes the rate R1 of the first clock CLK1. n Among the corresponding predetermined frequencies F i Based on the ratio between the rate R1 of the first clock and the rate R2 of the second clock,

[0034]

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[0035]

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[0036]

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[0037] It should be noted that, optionally, instead of pre-adjusting the sampling rates R1 and R2 of the first signal acquisition device 110 and the second signal acquisition device 120, post-adjustment / compensation of the sampling rates can be applied to at least one signal sample of the first signal acquisition device 110 and the second signal acquisition device 120 to compensate for the difference in sampling rates (for example, this can be done by re-interpolating at least one signal sample of the signal acquisition device). In this case, the signal samples in packets PC1 and / or PC2 sampled by at least one of the first signal acquisition device 110 and the second signal acquisition device 120 are adjusted to compensate for the difference in their respective sampling rates R1 and R2. For example, in some implementations,

[0038]

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[0039]

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[0040] It should be noted that equalizing / compensating for different sampling rates R1 and R2, either through a pre- or post-process as described above, may be performed only once, and / or may be performed occasionally to re-equalize sampling rates R1 and R2 if they drift over time.

[0041] In operation 210 of method 200, the calibration signal CS (also referred to herein as a dummy signal) is generated by the calibration signal generator 134 in the form of a continuous wave (CW) having a frequency that can be switched between a plurality of frequencies. For example, typically, the plurality of frequencies between which the frequency of the calibration signal CS can be switched are predetermined frequencies F1~F generated in the location signal TR by the location signal generator 132 that transmits it. nThis includes one or more or all of the following. The calibration signal generation unit 134 may be pre-configured to generate a calibration signal CS having those frequencies, and / or may be adapted to utilize reference data indicating it, which may be stored in a data repository 140 accessible by the calibration signal generation unit 134.

[0042] In operations 220 and 230, location signal outputs RS1 and RS2 from the first position sensor 34.1 and the second position sensor 34.2, respectively, as well as the calibration signal CS, are received, sampled, and packed by the first signal acquisition device 110 and the second signal acquisition device 120. More specifically, in 220, the first signal acquisition device 110 (e.g., its sampler 113, such as an A / D converter) simultaneously samples the location signal output RS1 of at least one first position sensor 34.1 received via at least one first channel CH1, and the calibration signal CS received via the second channel CH2. The first signal acquisition device 110 (e.g., its network communication device 115) then packs data representing the sampled signals from at least one first channel CH1 and the second channel CH2 into a packet PC1. The data packed into packet PC1 may include, for example, actual samples of the signals. Alternatively or additionally, the first signal acquisition device 110 may apply spectral processing to the sampled signal and be adapted to specify the characteristics of the frequency components contained in the sampled signal, such as the respective frequencies, amplitudes, and phases within packet PC1. Similarly, in 230, the second signal acquisition device 120 (e.g., its sampler 123, such as its A / D converter) simultaneously samples the location signal output RS2 from at least one second position sensor 34.2 received via at least one third channel CH3 and the calibration signal CS received via a fourth channel CH4. The second signal acquisition device 120 (e.g., its network communication device 125) then packs data representing the sampled signals from at least one third channel CH3 and the fourth channel CH4 into packet PC2. Furthermore, the data packed in packet PC2 may include, for example, actual samples of the signal, and / or the second signal acquisition device 120 may apply spectral processing to the sampled signal to specify the characteristics of the frequency components in packet PC2 (e.g., the frequency, amplitude, and phase of each frequency component).Packets PC1 and PC2 are then communicated to the synchronous processor 150 from the first signal acquisition device 110 and the second signal acquisition device 120, respectively (for example, by their respective network communication devices 115 and 125). The packet communication may be carried out over a network such as a TCP-based network (e.g., LAN, WAN, WiFi, or other network), and may optionally be directed to a workstation 55, where the synchronous processor 150 may optionally be implemented (for example, via its associated communication device 145).

[0043] In operation 250, the synchronization processor 150 determines the synchronization parameter SP required to synchronize between the position sensor signals RS1 and RS2 sampled by different signal acquisition devices. More specifically, in this example, it determines the synchronization parameter for synchronizing between the signals sampled from each of at least one first channel CH1 of the first acquisition device 110 and at least one third channel CH3 of the second acquisition device 120.

[0044] Figure 4B is a flowchart of a novel synchronization method 250 that can be implemented in the method 200 of Figure 4A (for example, by the synchronization processor 150) to determine synchronization parameters based on calibration signals CS sampled by the first acquisition device 110 and the second acquisition device 120, respectively (i.e., by each of at least the second channel CH2 and the fourth channel CH4).

[0045] In this regard, it should be noted that the sampling and packing 220 and 230 of position signals RS1 and RS2 by the first acquisition device 110 and the second acquisition device 120 are not necessarily simultaneous and / or may not be sufficiently time-aligned due to clock skew (e.g., clock delay) that may occur, for example, due to a lack of synchronization between the signal clocks CLK1 and CLK2 of the first acquisition device 110 and the second acquisition device 120. For example, even if the clock rates of the sampling clock CLK1 and the sampling clock CLK2 are adjusted to match, a timing difference ΔT may occur, where the ticks of one sampling clock lead or lag behind the ticks of the other clock. For this purpose, in some embodiments, one of the synchronization parameters determined and compensated by the synchronization processor 150 is the timing difference ΔT between the sampling and packing of signals processed by the first acquisition device 110 and the second acquisition device 120. In some embodiments, the synchronous processor 150 operates to determine the timing shift ΔT with subpacket resolution by performing operations 251, 252, and 253 of method 250 shown in Figure 4B. In this regard, it should be noted that the term subpacket resolution is used herein to specify a time resolution having a finer precision than the temporal duration / range of packets PC1 and PC2. Optionally, in some embodiments, the synchronous processor 150 further performs optional operations 255 and 256 to determine the timing shift ΔT with even more improved resolution, for example, with a resolution on the order of the signal sampling rate. The timing shift ΔT may also be determined by the synchronous processor 150 by processing a calibration signal CS, which is received and sampled in common by the first acquisition device 110 and the second acquisition device 120 via their respective second channel CH2 and fourth channel CH4.The timing difference ΔT determined in this way forms at least a part of the synchronization parameter SP, which in operation 260 is used by the synchronization processor 150 to synchronize between position signals RS1 and RS2, which are sampled from the first channel CH1 and the third channel CH3, respectively, of the first acquisition device 110 and the second acquisition device 120.

[0046] In addition to timing differences, it should be noted that the acquisition devices 110 and 120 (e.g., their respective samplers 113 and 123, and / or their amplifiers, optionally) may also introduce somewhat different amplitude gains into the sampled position signals RS1 and RS2, respectively, sampled by sampling the first acquisition device 110 and the second acquisition device 120 (e.g., due to hardware variations between samplers 113 and 123, and / or variations in the amplifiers, and / or the input voltage / power received for their operation). For this purpose, in embodiments in which the amplitudes of various frequency components in the position signals RS1 and RS2 are used by the positioning utility 190 to determine the positions of position sensors 34.1 and 34.2, the synchronous processor 150 may also perform an optional operation 258 of method 250 to determine the difference ΔG in amplitude gains introduced by the first acquisition device 110 and the second acquisition device 120. In such embodiments, the difference in amplitude gain ΔG also forms part of the synchronization parameter SP, which is then used in operation 260 to synchronize the position signals RS1 and RS2. Thus, in some embodiments, by processing the calibration signal CS, the difference in amplitude gain ΔG introduced by the respective samplers 113 and 123 of the first acquisition device 110 and the second acquisition device 120, which are sampled in common across the second channel CH2 and the fourth channel CH4, can be determined, and this gain difference ΔG can be further used to adjust the position signals RS1 and RS2, which are also sampled by the same respective samplers 113 and 123, in order to compensate for this gain difference ΔG.

[0047] Next, with reference to Figure 4B, the synchronous operation 250 in Figure 4A will be described in more detail. The operation / method 250 may optionally include several processes for determining one or more synchronization parameters for synchronizing between position signals RS1 and RS2. The first process, also referred to herein as packet synchronization, may include, for example, operations 251 to 253 (which may be performed, for example, by a packet synchronization device module 152 of the synchronization processor 150). The synchronization processor 150, for example, the packet synchronization device module 152, may be adapted to perform operations 251 to 253 as follows.

[0048] In packets PC1 and PC2, a pair of substantially simultaneous packets is identified that have samples from the second channel CH2 and the fourth channel CH4 (thereby the calibration signal CS is received and sampled by the first acquisition device 110 and the second acquisition device 120), and as a result, in both packets of the pair, there is a transition between at least the first and second frequencies of the switched frequencies of the calibration signal CS (251). Here, a pair of substantially simultaneous packets refers to a pair of packets that both contain / show samples of the common portion of the calibration signal CS. A pair of simultaneous packets may be identified, for example, based on the count, order, and / or ordinal / index of packets PC1 and PC2 received from the first acquisition device 110 and the second acquisition device 120 (for example, it is not necessarily required to specifically examine the contents of the packets).

[0049] As described above, the calibration signal CS is a CW signal whose frequency is switched periodically between multiple frequencies (252). In operation 252, a pair of simultaneous packets is processed to determine the transition time between at least a first frequency and a second frequency in the calibration signal CS in each of the simultaneous packets. In other words, the frequency switching acts as a time reference, and based on this, the time difference (clock skew) between the timing of packaging packets PC1 and PC2 can be estimated by the first acquisition device 110 and the second acquisition device 120. Generally, the transition time between at least a first frequency and a second frequency in each packet can be determined by various signal processing techniques (for example, by processing a sample of the signal in the packet to identify the sample index where the sampled frequency of the CW signal is the first frequency and the second frequency is ahead of the second frequency). However, in some embodiments, this process can be efficiently performed by determining the respective powers of the first frequency and the second frequency of the sampled calibration signal portion in each of the simultaneous packets and taking their ratio. For example, considering a packet that represents a portion of the total duration T of a calibration signal CS, which contains only two frequencies F1 and F2 of the CS calibration signal, the transition time t between those two frequencies relative to the start of the packet duration can be estimated based on the relative powers P(F1) and P(F2) of the first and second frequency components in the packet, as follows:

[0050]

number

[0051] Therefore, once the transition times t1 and t2 between at least two frequency components F1 and F2 of the calibration signal CS are determined for a simultaneous packet having subpacket resolution, the subpacket resolution time shift / temporal lag Δt between simultaneous packets is determined. P This is typically done by tracking the difference between the respective transition times t1 and t2, for example, Δt P This can be determined by =t2-t1 (253).

[0052] In some embodiments, the subpacket resolution time shift Δt PThis can be sufficiently accurate, and for example, in some implementations, it can be determined with a resolution sufficiently high on the order of the sampling time resolution. Therefore, in such embodiments, the total time difference (clock skew) Δt between sampling and packing of the respective location signals RS1 and RS2 by the first acquisition device 110 and the second acquisition device 120 is the subpacket resolution time shift.

[0053]

number

[0054] However, in some other embodiments, the subpacket resolution time shift Δt P The resolution is not high enough to facilitate accurate determination of the simultaneous positions of position sensors 34.1 and 34.2. For example, as described above, in some embodiments, an efficient implementation of the time shift between packets PC1 and PC2 can be determined at subpacket resolution based on the ratio of powers of the frequency components of the calibration signal, such as those sampled by the first acquisition device 110 and the second acquisition device 120. However, this exemplary technique does not allow for a time shift Δt P Decomposing it is efficient, but in some implementations, the time shift Δt is of an order smaller than the characteristic periodicity of the frequency in the position signal. P The resolution may not be sufficiently high (e.g., substantially lower than the sampling rate). In other words, in some embodiments, the synchronization of the subpacket resolution may be finer than the characteristic time period of the frequency components in the location signal RS (e.g., on the order of the time period of the frequency components of the location signal RS, sufficient to compensate for the time difference between the “unwrapped” phases of the location signals RS1 and RS2 of the first position sensor 34.1 and the second position sensor 34.2).

[0055] For this purpose, the determined subpacket resolution time shift Δt PHowever, in embodiments where accuracy is only on the order of the characteristic period of the frequency in the position signal RS, there is some residual time difference Δt between the first location signal RS1 and the second location signal RS2, each having a duration shorter than the characteristic period of the frequency in the position signal RS. S In other words, in such embodiments, the total time difference Δt clock skew between sampling and packing of the respective location signals RS1 and RS2 is determined by the subpacket resolution time shift Δt determined by 250A. P Asserting that it is approximately equal to may not be sufficient, and the total time difference Δt

[0056]

number

[0057] This residual time difference Δt S Since this is shorter than the characteristic period of the frequency in the position signal RS, it can be inferred from the difference between the wrapped phases of a particular signal component sampled simultaneously by both the first acquisition device 110 and the second acquisition device 120 (as used herein, the term wrapped phase refers to the phase between -π and π, i.e., a phase smaller than one wavelength period). Therefore, in some implementations, a further temporal synchronization process, including operations 255 and 256, may be performed (e.g., with a resolution on the order of sampling / clock rate) to determine the total temporal shift Δt between the location signals RS1 and RS2. This further temporal synchronization process, which may be implemented by, for example, the phase-locking device 154 module of the synchronization processor 150, may include, for example:

[0058] The substantially simultaneous packet pair of packets PC1 and PC2 is processed, including samples of the calibration signal CS sampled by the first acquisition device 110 and the second acquisition device 120 from the second channel CH2 and the fourth channel CH4, respectively, and the residual time difference Δt is calculated. S Determine (255). A pair of substantially simultaneous packets may be, for example, the same pair of simultaneous packets identified in operation 250A(a), or another pair of such simultaneous packets (e.g., from different timings). The simultaneous packets are processed, for example by spectral analysis / processing, and the phase difference Δφ between the phases of at least one frequency component Fi that is commonly contained therein is determined. Fi The phase difference Δφ is determined. Spectral analysis / processing can generally be performed by any suitable technique known in the art (e.g., by any suitable Fourier transform processing algorithm) to determine the phases φ1 and φ2 of the frequency components Fi in the simultaneous packets of packets PC1 and PC2, respectively, but preferably, in some embodiments, it is performed using the Goertzel process. In this regard, since the frequencies included in the calibration signal CS are generally known / predetermined, it should be understood that using the Goertzel process allows us to leverage predetermined frequency information to efficiently determine the phase of the common frequency component Fi of the simultaneous packets. Thus, the phase difference Δφ Fi This is based on the difference between the phases φ1 and φ2 of the frequency components Fi in each simultaneous packet, for example, Δφ Fi This can be determined by =φ1-φ2.

[0059] Next, in 256, the phase difference Δφ determined with respect to frequency Fi in operation 255 is Fi And the subpacket resolution time shift Δt determined by operations 251-253. P Based on this, the total clock skew time shift Δt between the first acquisition device and the second acquisition device is determined. In this regard, in some embodiments of 255, first, the signals / samples in a pair of simultaneous packets are determined by the subpacket resolution time shift Δt between them.P To compensate for this, they are temporally shifted relative to each other, and then spectral analysis / processing (e.g., Goertzel process) is performed to determine their phases φ1 and φ2. In such embodiments, the residual time difference Δt S This can be determined by, for example, 256 as follows:

[0060]

number

[0061]

number

[0062]

number

[0063] Therefore, in the optional process of operations 255-256, the total time difference / clock skew Δt between the first acquisition device 110 and the second acquisition device 120 is (for example, the subpacket resolution time shift Δt determined by operations 251-253) P And the residual time difference Δt determined by operations 255 and 256 S By considering both, for example, Δt = Δt P +Δt S It can be determined with improved accuracy, as shown above.

[0064] For this purpose, optional operations 255 and 256 may be performed to determine the total time difference / clock skew Δt between the first acquisition device 110 and the second acquisition device 120 (e.g., between their respective signal clocks) with a resolution of the order of sampling resolution. In some embodiments, this may be based on a comparison of the phases of the calibration signal CS in the second channel CH2 and the fourth channel CH4, and thus can compensate for mismatches between the wrapped phases of the signals. In a typical embodiment, the time range of each packet PC1 and PC2 is longer than the period between characteristic wavelengths in the signals, and therefore, in such embodiments, further time synchronization operations 255-256 may be performed only after the subpacket resolution time synchronization operations 251-253 have been performed, and as a result, any unwrapped phase differences longer than the characteristic wavelength period are eliminated / accepted by these operations.

[0065] As described above, in some implementations, the first acquisition device 110 and the second acquisition device 120 may each introduce somewhat different amplitude gains to the signals being processed. Therefore, in an embodiment in which the positioning utility 190 determines the respective positions of the position sensors 34 depending on the amplitude of the sensed position signal RS, the method 200 may further include an optional operation 258 for determining the difference ΔG between the amplitude gains introduced to the position signals RS1 and RS2 by the first acquisition device 110 and the second acquisition device 120, respectively.

[0066] Operation 258 may be performed, for example, by the amplitude balancer 156 module of the synchronous processor 150. For this purpose, operation 258 may include identifying at least one pair of packets PC1 and PC2 received from the first acquisition device 110 and the second acquisition device 120, each of which includes a sample of the calibration signal CS acquired by the first acquisition device 110 and the second acquisition device 120, respectively, via the outputs of the second channel CH2 and the fourth channel CH4. Next, the pairs of packets from the first acquisition device 110 and the second acquisition device 120 are processed to identify at least one frequency component F of the calibration signal that is commonly contained in each of the pairs of packets. i The amplitudes A1 and A2 are identified. The process of determining each amplitude may be performed using any appropriate spectral analysis process (e.g., Fourier transform), and more preferably, in embodiments where the frequency components in the calibration signal are known / re-determined, a Goertzel process may be used to efficiently determine the amplitudes A1 and A2. The difference ΔG between the amplitude gains introduced into the sensed location signals RS1 and RS2 by the first acquisition device 110 and the second acquisition device 120 can then be determined, for example, based on the ratio of the amplitudes of the calibration signals sampled by the first acquisition device 110 and the second acquisition device 120, as follows: ΔG = A1 / A2.

[0067] In this regard, it should be noted that in some embodiments, the gain difference between the gains introduced into the signal by the first acquisition device 110 and the second acquisition device 120 is frequency-dependent. In other words, the gain difference between the gains introduced into the signal by the first acquisition device 110 and the second acquisition device 120 is frequency-dependent. n The different frequency components can be amplified / suppressed differently by the first acquisition device 110 and the second acquisition device 120. In such embodiments, operation 258 is performed on predetermined frequencies F1~F of the location signal RS. n Each frequency component F i The gain difference ΔG for each i It can be adapted to determine multiple gain differences ΔG, including .

[0068] For this purpose, in such embodiments, in the method operation 210 described above, the calibration signal CS is generated by the calibration signal generation unit 134 so that the frequency of the location signal RS is a plurality of predetermined frequencies F1 to F n It is generated as a CW signal that can be switched between. Therefore, in operation 258 for determining the gain difference, each gain difference ΔG i In the transmitted location signal TR, predetermined frequencies F1 to F are generated by the location signal generation unit 132. n The frequency F1~F in the transmitted location signal TR can be determined for each. n The respective gain difference ΔG for each predetermined frequency. i Determining this involves, for example, each predetermined frequency F. i Each can include the following: - Identify the packet pair of packets PC1 and PC2 received from the first acquisition device 110 and the second acquisition device 120, and determine if both packets in the pair have a frequency of a predetermined frequency F i It includes at least a portion of the CW calibration signal CS. Next, spectral processing such as the Goertzel process is used to determine the predetermined frequency F i Processing a pair of packets having a predetermined frequency F, which is acquired from the first acquisition device 110 and the second acquisition device 120, respectively, in each packet of the pair. i Each amplitude A1 i and A2 i To decide. - The predetermined frequency F i Gain difference ΔG i This is the predetermined frequency F in the calibration signal sampled by the first acquisition device 110 and the second acquisition device 120. i Amplitude A1 i and A2 i Based on the ratio between the two, ΔG i =A1 i / A2 i It can be decided as follows. Therefore, the gain difference {ΔG i} is each of the predetermined frequencies F1~F n It is determined on a case-by-case basis.

[0069] Taking the above into consideration, Method / Operation 250 provides for determining a synchronization parameter SP for synchronizing signals sampled by a first signal acquisition device 110 and a second signal acquisition device 120. The synchronization parameter SP may include a time difference / clock skew Δt between the first acquisition device 110 and the second acquisition device 120, which in some embodiments may be determined using subpacket resolution and / or higher resolution (e.g., by further implementing optional operations 255-256). In some embodiments, the synchronization parameter SP is the gain difference {ΔG} between the first acquisition device 110 and the second acquisition device 120. i This also includes data indicating}. As mentioned above, in some implementations, the frequency F1~F of a given location signal is n The difference in gain {ΔG} introduced at different frequencies. i {ΔG} is asserted to be substantially the same, and a single gain difference ΔG is determined at 258 (for example, based on a comparison of the amplitude of one frequency component between the calibration signals sampled by acquisition devices 110 and 120). Alternatively, in some embodiments, the gain difference {ΔG} i} is the frequency F1~F of the predetermined location signal. n It is determined for each of the respective frequencies.

[0070] Referring again to Figures 3 and 4A, the synchronization parameters SP determined by operation 250 are provided to the synchronization device 160, which uses them to synchronize between location signals RS1 and RS2 sampled and packed by the first acquisition device 110 and the second acquisition device 120, respectively. In this regard, it should be understood that the synchronization parameters SP are not typically determined for each pair of simultaneous packets of location signals acquired via channels CH1 and CH3, but may be determined only once during a medical procedure (e.g., during the initialization of the positioning system 100), or may be determined from time to time during the operation of the positioning system, for example, at predetermined time intervals, or the synchronization parameters SP may be re-evaluated to compensate for drift that may occur at the rates of clocks CLK1 and CLK2, or to compensate for fluctuations in the power input to the first acquisition device 110 and the second acquisition device 120, which may affect the gain difference between them. For example, in some implementations, the calibration signal generation unit 134 may be configured to generate a calibration signal CS, which is supplied to channels CH2 and CH4 only at specific time intervals, and the synchronization processor 150 may be adapted to perform an operation 250 to determine / update the synchronization parameter SP only when there is a simultaneous pair of packets in packets PC1 and PC2 containing calibration signals sampled by the first acquisition device 110 and the second acquisition device 120, respectively.

[0071] Next, each time the synchronization parameters SP are determined / updated by the synchronization processor 150, the synchronization device 160 acquires the synchronization parameters SP from the synchronization processor 150. The synchronization device 160 executes operation 260, synchronizes between the position signals RS1 and RS2 acquired by synchronizing different first acquisition devices 110 and second acquisition devices 120 using the synchronization parameters SP, and outputs a synchronized position signal SS synchronized according to the parameters accordingly. Synchronization 260 is generally / typically executed for all samples of the signals sampled from the first channel CH1 and the third channel CH3 based on the updated synchronization parameters SP associated with them. Synchronization 260 includes synchronizing the timings of the signals sampled from the first channel and the third channel based on the subpacket resolution time shift / clock skew

[0072]

Number

[0073] In operation 290 of method 200, the respective positions of the medical devices 14A and 14B, the medical instruments 26, or the position sensors 34.1 and 34.2 associated therewith, can be determined by the positioning utility 190, for example, based on a synchronous position signal obtained from operation 260. As will be readily apparent to those skilled in the art, the position determination itself for each position of a signal transmitter, e.g., 32, can be implemented by various techniques known in the art (as long as the phase of the location signal, and optionally the amplitude as well, are accurately measured with respect to the corresponding transmitted signal). In non-limiting examples, this can be performed using time of arrival (TOA), time difference of arrival (DTOA), triangulation, and / or any other suitable techniques or combinations thereof to determine the location and / or orientation of the medical module relative to a reference frame (coordinates) defined by the signal transmitter, e.g., 32. Thus, the positions of the medical devices 14A and 14B and / or their distal end portions 35 and / or the medical instruments 26 thereon can be accurately determined by system 100 based on the synchronous signal SS.

[0074] In this regard, it should be noted that the position of each medical instrument 26 or device 14 may be inferred, for example, based on measurements of the position of a position sensor 34 associated with them, and the position sensor may be, for example, a magnetic / electromagnetic based position sensor. Alternatively or additionally, the position of one or more distal end portions 35 of a medical device 14, such as the position of the body of the medical device 14 (e.g., the shaft of the catheter) 29 of the medical device 14, such as a catheter 14A or 14B, and / or the position of one or more flexible / movable sections / splines 22 thereof may be determined based on the positions of multiple position sensors. For example, in some embodiments, the position sensors 34.1 or some of them may be located near each medical instrument 26 of the medical device / catheter 14A, and may not be located with a particular proximity to any particular position sensor. The positioning utility 190 utilizes signals from a combination of position sensors 34.1 of the medical device 14A to determine / evaluate the shape of the distal end flexible / movable section 22 of the medical device 14A (for example, using predetermined data indicating the bending behavior of these movable sections 22), and based on the position of the position sensors 34.1, it can determine the bent / shifted shape of the distal end 28 of the medical device / catheter 14A, thereby also determining the position of the medical instrument 26 located thereon. Furthermore, in some embodiments, the position sensors 34.1 of a medical device such as 14A may include at least one "primary" position sensor 34A that may be located on a specific distal end portion of the medical device 14A, such as its body / shaft 29, and one or more additional position sensors, such as 34B-34K, that may be located on the flexible / movable section 22 of the medical device 14A. The "main" position sensor 34A may be implemented as a triaxial sensor (TAS) (e.g., including three magnetic coils) capable of sensing the three-dimensional (3D) location and orientation of a specific distal end portion of the medical device 14A, such as the location of its body / shaft 29, and one or more additional position sensors, e.g., 34B-34K, may be implemented as monoaxial sensors (SAS) (e.g., each including one magnetic coil capable of sensing its orientation).In such embodiments, the positioning utility 190 may be adapted to combine position signals obtained from one or more additional position sensors (which may be SAS sensors 34B-34K) with position signals obtained from the main / TAS position sensor 34A of the medical device 14A (for example, taking into account their respective self-measured orientations, the 3D location of the TAS sensor, and their deformations which may optionally be evaluated based on the geometric characteristics / shape of the medical device 14A, and optionally based on the relative orientation of the TAS and SAS position sensors of the medical device). [Examples]

[0075] Example 1. A position sensing system 100, a. A calibration signal generation unit 134 configured to generate a calibration signal CS in the form of a continuous wave (CW) whose frequency can be switched between multiple frequencies, b. A first signal acquisition device 110 configured to sample the output from the first position sensor 34.1 via the first channel CH1, sample the calibration signal CS output from the calibration signal generation unit 134 via the second channel CH2, and transmit the sampled outputs from the first channel and the second channel in a packet PC1, c. A second signal acquisition device 120 is configured to sample the output from the second position sensor 34.2 via the third channel CH3, sample the calibration signal CS output from the calibration signal generation unit 134 via the fourth channel CH4, and transmit the sampled outputs from the third channel and the fourth channel, respectively, in a packet PC2. d. A synchronous processor 150, i. Identifying a pair of simultaneous packets on a second channel CH2 and a fourth channel CH4, which includes a transition between at least a first frequency and a second frequency among a plurality of frequencies, ii. Determining the respective transition times between the first frequency and the second frequency in the sampled output of the second channel CH2 and the fourth channel CH4, iii. A synchronous processor 150 configured to determine, with subpacket resolution, the time shift between the output sampling performed by the first signal acquisition device 110 and the output sampling performed by the second signal acquisition device 120, based on the difference between their respective transition times, e. A synchronization device 160 adapted to synchronize the outputs of the first channel CH1 and the third channel CH3 associated with the first position sensor 34.1 and the second position sensor 34.2 based on a time shift, f. A position sensing system 100, including a positioning utility 190 adapted to process the synchronized outputs of a first channel CH1 and a third channel CH3 to determine the positions of a first position sensor 34.1 and a second position sensor 34.2, and to stream position-indicating data to a display 27.

[0076] Example 2. System 100 according to Example 1, wherein determining the respective transition times between the first frequency and the second frequency in the sampled outputs of the second channel CH2 and the fourth channel CH4 includes determining the respective ratios between the power of the first frequency and the power of the second frequency in a simultaneous packet.

[0077] Example 3. The system 100 according to Example 2, comprising determining the power of the first and second frequencies in a simultaneous packet by applying spectral processing to the sampled outputs of the second channel CH2 and the fourth channel CH4, which appear in the simultaneous packet, respectively.

[0078] Example 4. The system 100 described in Example 3 is implemented using a Goertzel process based on data indicating a first frequency and a second frequency.

[0079] Example 5. The first signal acquisition device 110 and the second signal acquisition device 120 introduce different amplitude gains to the sampled outputs of the first and second channels (CH1, CH2) and the third and fourth channels (CH3, CH4), respectively, which are sampled by them, and the synchronous processor is further configured to compare the amplitudes of the sampled outputs of the second channel CH2 and the fourth channel CH4 to determine the gain difference between the amplitude gains introduced by the first signal acquisition device 110 and the second signal acquisition device 120 to the sampled outputs of the first channel CH1 and the third channel CH3, respectively, and the synchronous device 16 System 100 according to any one of Examples 1 to 4, wherein gain compensation is applied to adjust the amplitude of the signal component in at least one output of the first channel CH1 and the third channel CH3 in order to compensate for a gain difference, thereby obtaining the synchronized sampled outputs of the first channel CH1 and the third channel CH3 as gain-compensated outputs, and the positioning utility 190 is adapted to process the gain-compensated outputs from the first channel CH1 and the third channel CH3 in order to accurately determine the positions of the first position sensor 34.1 and the second position sensor 34.2 based on the adjusted amplitude.

[0080] Example 6. The amplitude gain may differ for different frequencies, and the calibration signal generation unit generates a plurality of predetermined frequencies F1 to F that are expected to be received from the first position sensor 34.1 and the second position sensor 34.2 via the first channel CH1 and the third channel CH3. n It includes the output of the second channel CH2 and the fourth channel CH4, and multiple frequencies F1~F with a frequency switching time interval longer than the duration of the packet. n System 100 according to Embodiment 5 generates a continuous wave (CW) to switch between the following. The synchronous processor 150 sets each pair of packets on the second channel CH2 and the fourth channel CH4 so that both packets in each pair are on the predetermined frequency F1 to F nadapted to identify so as to include at least one of them, and based on the amplitudes of each predetermined frequency of a pair of corresponding packets, for predetermined frequencies F1 to F n to determine the gain difference for, and the synchronization device executes gain compensation for each of the predetermined frequencies F1 to F n for each.

[0081] Example 7. The first signal acquisition device 110 and the second signal acquisition device 120 use their respective first sampling clock CLK1 and second sampling clock CLK2 to sample the outputs of their associated channels at a sampling resolution, and the first sampling clock CLK1 and the second sampling clock CLK2 are not temporally aligned, thereby introducing a clock skew between the sampled outputs of the first channel CH1 and the second channel CH2 and the sampled outputs of the third channel CH3 and the fourth channel CH4. The synchronization processor 150 is - processing at least one pair of simultaneous packets of the outputs of the second channel CH2 and the fourth channel CH4 respectively sampled by the first signal acquisition device 110 and the second signal acquisition device 120 to determine the respective phases of the frequency components included in the outputs of both the second channel CH2 and the fourth channel CH4; - further configured to determine the clock skew based on the difference between each phase and the time shift, The synchronization device 160 is further adapted to synchronize the timing of the output of the first channel CH1 and the timing of the output of the third channel CH3 in order to compensate for the clock skew between the first signal acquisition device 110 and the second signal acquisition device 120.

[0082] Example 8. The system 100 according to any one of Examples 1 to 7, further comprising a rate controller 121 adapted to match the sampling clock rate (e.g., CLK2) of one of the first signal acquisition device 110 and the second signal acquisition device 120 to the sampling clock rate (e.g., CLK1) of the other of the first signal acquisition device 110 and the second signal acquisition device 120.

[0083] Example 9. System 100 according to any one of Examples 1 to 7, further comprising a rate controller 141 adapted to adjust the sampling rate of a signal sampled by at least one of the first signal acquisition device 110 and the second signal acquisition device 120, to match the sampling rates in the signals sampled by the first signal acquisition device 110 and the second signal acquisition device 120, thereby compensating for the different clock rates of the sampling clocks CLK2 of the first signal acquisition device 110 and the second signal acquisition device 120.

[0084] Example 10. A catheter-based mapping and ablation system 10 comprising the positioning system 10 described in any one of Examples 1 to 9.

[0085] Example 11. A method 200 for sensing position, (210) Generate a calibration signal CS in the form of a continuous wave CW whose frequency can be switched between multiple frequencies. The first signal acquisition device 110 samples the output from the first position sensor 34.1 via the first channel CH1 and samples the calibration signal CS output via the second channel CH2, and transmits the sampled outputs of the first channel CH1 and the second channel CH2, respectively, in the first packet PC1 (220). The second signal acquisition device 120 samples the output from the second position sensor 34.2 via the third channel CH3 and samples the calibration signal output CS via the fourth channel CH4, and transmits the outputs sampled from the third channel CH3 and the fourth channel CH4, respectively, in the second packet PC2 (230). Determining synchronization parameters for synchronizing signals sampled from each of the first channel CH1 and third channel CH3 based on calibration signals CS sampled from each of the second channel CH2 and fourth channel CH4 (250), wherein determining the synchronization parameters is Identifying a pair of simultaneous packets containing sampled outputs of a second channel CH2 and a fourth channel CH4, each having a transition between at least a first frequency and a second frequency among multiple frequencies (251), The transition times between the first frequency and the second frequency in the sampled outputs of the second channel CH2 and the fourth channel CH4 are determined (252), (253) includes determining a time shift between the output sampling performed by the first signal acquisition device 110 and the output sampling performed by the second signal acquisition device 120, with subpacket resolution, based on the difference between the respective transition times. Based on the time shift, the outputs of the first channel CH1 and the third channel CH3 associated with the first position sensor 34.1 and the second position sensor 34.2 are synchronized (260), Method 200 includes (290) streaming data indicating the positions of a first position sensor 34.1 and a second position sensor 34.2, determined based on the synchronized outputs of a first channel CH1 and a third channel CH3, to a display 27.

[0086] Example 12. The method according to Example 11, wherein determining the respective transition times between the first frequency and the second frequency in the sampled output of the second channel CH2 and the fourth channel CH4 includes determining the respective ratios between the power of the first frequency and the power of the second frequency in the simultaneous packets PC1 and PC2, respectively.

[0087] Example 13. The method according to Example 12, further comprising determining the power of the first and second frequencies in a simultaneous packet by applying spectral processing to the sampled outputs of the second channel CH2 and the fourth channel CH4, which appear in the simultaneous packet, respectively.

[0088] Example 14. The method according to Example 13, wherein spectral processing is implemented using a Goertzel process based on data indicating a first frequency and a second frequency.

[0089] Example 15. The method according to any one of Examples 11 to 14, wherein the first signal acquisition device 110 and the second signal acquisition device 120 introduce different amplitude gains to the sampled outputs of the first channel CH1 and the second channel CH2, and the sampled outputs of the third channel CH3 and the fourth channel CH4, respectively, sampled by them, and determine the synchronization parameters (250), further comprising comparing the amplitudes of the sampled outputs of the second channel CH2 and the fourth channel CH4 to determine the gain difference between the amplitude gains introduced to the sampled outputs of the first channel CH1 and the third channel CH3 by the first signal acquisition device 110 and the second signal acquisition device 120, respectively (258). Synchronizing the sampled outputs (260) further includes performing gain compensation to adjust the amplitude of the signal component in at least one of the outputs of the first channel CH1 and the third channel CH3 to compensate for the gain difference, thereby obtaining synchronized outputs of the first channel CH1 and the third channel CH3 as gain-compensated outputs. The positions of the first position sensor 34.1 and the second position sensor 34.2 are determined by processing the gain-compensated outputs of the first channel CH1 and the third channel CH3.

[0090] Example 16. The method according to Example 15, wherein the amplitude gain may differ for different frequencies. Multiple frequencies of the calibration signal CS are a plurality of predetermined frequencies F1~F that are expected to be received from the first position sensor 34.1 and the second position sensor 34.2 via the first channel CH1 and the third channel CH3. n Method 200 includes switching the frequency of the calibration signal CS to multiple frequencies F1~F at a switching time interval longer than the duration of the packet containing the outputs of the second channel CH2 and the fourth channel CH4. n This includes switching between multiple predetermined frequencies F1~F. Determining the synchronization parameter (250) involves multiple predetermined frequencies F1~F n For each predetermined frequency, - Identifying each pair of packets having a second channel CH2 and a fourth channel CH4 that include a predetermined frequency, - This includes determining the gain difference for each predetermined frequency based on the amplitude of the corresponding pair of packets in each pair. Synchronizing (260) further includes performing gain compensation for each predetermined frequency.

[0091] Example 17. The first signal acquisition device 110 and the second signal acquisition device 120 use their respective first sampling clock CLK1 and second sampling clock CLK2 to sample the output of their associated channels with sampling resolution, and the first sampling clock CLK1 and the second sampling clock CLK2 are not temporally aligned, thereby introducing a clock skew between the sampled outputs of the first and second channels CH1 and CH2 and the sampled outputs of the third and fourth channels CH3 and CH4, and determining the synchronization parameter (250) is as follows: (255) Processing at least one pair of simultaneous packets of outputs of the second channel and the fourth channels CH2 and CH4, sampled by the first signal acquisition device 110 and the second signal acquisition device 120, respectively, to determine the phase of each of at least one frequency included in the outputs of both the second channel and the fourth channels CH2 and CH4. (256) further includes determining the clock skew based on the difference between each phase, Synchronization (260) further includes synchronizing the outputs of a first channel CH1 and a third channel CH3 to compensate for clock skew, according to the method 200 of any one of Examples 11 to 16.

[0092] Example 18. The method according to any one of Examples 11 to 17, comprising adjusting the sampling clock rate (e.g., CLK2) of one of the first signal acquisition device 110 and the second signal acquisition device 120 to match the sampling clock rate (e.g., CLK1) of the other of the first signal acquisition device 110 and the second signal acquisition device 120.

[0093] Example 19. The method according to any one of Examples 11 to 17, comprising interpolating the signals sampled by at least one of the first signal acquisition device 110 and the second signal acquisition device 120, adjusting their sampling rates so that the sample rates of the signals sampled by the first signal acquisition device 110 and the second signal acquisition device 120 match, thereby compensating for the different clock rates in the sampling clocks CLK1 and CLK2 of the first signal acquisition device 110 and the second signal acquisition device 120.

[0094] The embodiments described above are cited as examples only, and it should be understood that this disclosure is not limited to those specifically illustrated and described above. Rather, the scope of this disclosure includes both combinations and partial combinations of the various features described above in this specification, as well as variations and modifications thereof that can be conceived by those skilled in the art by reading the description of the invention and that are not disclosed in the prior art.

[0095] [Implementation Method] (1) A position sensing system, a. A calibration signal generation unit configured to generate a calibration signal in the form of a continuous wave (CW) whose frequency can be switched between multiple frequencies, b. A first signal acquisition device configured to sample the output from a first position sensor via a first channel, sample the calibration signal output from the calibration signal generation unit via a second channel, and transmit the sampled outputs from each of the first and second channels in packets. c. A second signal acquisition device configured to sample the output from the second position sensor via a third channel, sample the calibration signal output from the calibration signal generation unit via a fourth channel, and transmit the sampled outputs from each of the third and fourth channels in packets. d. A synchronous processor, i. Identifying a pair of simultaneous packets between the second channel and the fourth channel, which includes a transition between at least a first frequency and a second frequency among the plurality of frequencies, ii. Determining the respective transition times between the first frequency and the second frequency in the sampled output of the second channel and the fourth channel, iii. A synchronous processor configured to determine, using subpacket resolution, the time shift between the sampling of the output performed by the first signal acquisition device and the sampling of the output performed by the second signal acquisition device, based on the difference between the respective transition times, e. A synchronization device adapted to synchronize the outputs of the first channel and the third channel associated with the first position sensor and the second position sensor based on the time shift, f. A position sensing system comprising a positioning utility adapted to process the synchronized outputs of the first channel and the third channel to determine the positions of the first position sensor and the second position sensor, and to stream the data indicating the positions to a display. (2) The system according to Embodiment 1, wherein determining the respective transition times between the first frequency and the second frequency in the sampled output of the second channel and the fourth channel includes determining the respective ratios of power between the first frequency and the second frequency in the simultaneous packet. (3) The system according to Embodiment 2, comprising determining the power of the first frequency and the second frequency in the simultaneous packet by applying spectral processing to the sampled outputs of the second channel and the fourth channel, which appear in the simultaneous packet, respectively. (4) The system according to Embodiment 3, wherein the spectral processing is implemented using a Goertzel process based on data indicating the first frequency and the second frequency. (5) The system according to Embodiment 1, wherein the first signal acquisition device and the second signal acquisition device introduce different amplitude gains into the sampled outputs of the first channel and the second channel and the third channel and the fourth channel, respectively, which are sampled by them, the synchronous processor is further configured to compare the amplitudes of the sampled outputs of the second channel and the fourth channel to determine the gain difference between the amplitude gains introduced by the first signal acquisition device and the second signal acquisition device into the sampled outputs of the first channel and the third channel, respectively, the synchronous device is further configured to apply gain compensation to adjust the amplitude of the signal component in at least one of the outputs of the first channel and the third channel to compensate for the gain difference, thereby acquiring the synchronized sampled outputs of the first channel and the third channel as gain-compensated outputs, and the positioning utility is adapted to process the gain-compensated outputs from the first channel and the third channel to accurately determine the positions of the first position sensor and the second position sensor based on the adjusted amplitudes.

[0096] (6) The system according to Embodiment 5, wherein the amplitude gain may differ for different frequencies, the calibration signal generation unit generates the continuous wave (CW) such that the plurality of frequencies include a plurality of predetermined frequencies that are expected to be received from the first position sensor and the second position sensor via the first channel and the third channel, and switches between the plurality of frequencies with time intervals between frequency switches that are longer than the duration of the packets including the outputs of the second channel and the fourth channel, the synchronous processor is adapted to identify each pair of packets of the second channel and the fourth channel, both packets of each pair include at least one of the predetermined frequencies, and determines the gain difference of the predetermined frequencies based on the amplitude of each predetermined frequency of the corresponding pair of packets, and the synchronous device performs the gain compensation for each predetermined frequency of the predetermined frequencies. (7) The first signal acquisition device and the second signal acquisition device use their respective first sampling clock and second sampling clock to sample the output of their associated channels with sampling resolution, the first sampling clock and the second sampling clock are not temporally aligned, thereby introducing a clock skew between the sampled outputs of the first and second channels and the sampled outputs of the third and fourth channels, and the synchronous processor, - Processing at least one pair of simultaneous packets of the outputs of the second channel and the fourth channel, sampled by the first signal acquisition device and the second signal acquisition device, respectively, to determine the phase of each of the frequency components contained in the outputs of both the second channel and the fourth channel, -The system is further configured to determine the clock skew based on the difference between each of the phases and the time shift, The system according to Embodiment 1, wherein the synchronization device is further adapted to synchronize the timing of the output of the first channel with the timing of the output of the third channel in order to compensate for the clock skew between the first signal acquisition device and the second signal acquisition device. (8) The system according to Embodiment 1, further comprising a rate controller adapted to adjust the sampling clock rate of one of the first signal acquisition device and the second signal acquisition device to match the sampling clock rate of the other of the first signal acquisition device and the second signal acquisition device. (9) The system according to Embodiment 1, further comprising a rate controller adapted to adjust the sampling rate of a signal sampled by at least one of the first signal acquisition device and the second signal acquisition device to match the sampling rate in the signal sampled by the first signal acquisition device and the second signal acquisition device, thereby compensating for the different clock rates of the sampling clocks of the first signal acquisition device and the second signal acquisition device. (10) A catheter-based mapping and ablation system comprising the positioning system described in Embodiment 1.

[0097] (11) A method for determining location, a. To generate a calibration signal in the form of a continuous wave (CW) whose frequency can be switched between multiple frequencies, b. The first signal acquisition device samples the output from the first position sensor via the first channel, samples the calibration signal output from the calibration signal generation unit via the second channel, and transmits the sampled outputs of the first channel and the second channel in a first packet. c. The second signal acquisition device samples the output from the second position sensor via the third channel, samples the calibration signal output from the calibration signal generation unit via the fourth channel, and transmits the sampled outputs from the third channel and the fourth channel in a second packet. d. Determining a synchronization parameter for synchronizing the signals sampled from each of the first and third channels based on the calibration signals sampled from each of the second and fourth channels, wherein determining the synchronization parameter is: i. Identifying a pair of simultaneous packets, each containing sampled outputs of the second and fourth channels, where there is a transition between at least one first frequency and a second frequency among the plurality of frequencies, ii. Determining the respective transition times between the first frequency and the second frequency in the sampled output of the second channel and the fourth channel, iii. Based on the difference between the respective transition times, determine a time shift at subpacket resolution between the sampling of the output performed by the first signal acquisition device and the sampling of the output performed by the second signal acquisition device, e. Synchronizing the outputs of the first channel and the third channel associated with the first position sensor and the second position sensor based on the time shift, f. A method comprising streaming data indicating the simultaneous positions of the first position sensor and the second position sensor, determined based on the synchronized outputs of the first channel and the third channel, to a display. (12) The method according to Embodiment 11, wherein determining the respective transition times between the first frequency and the second frequency in the sampled output of the second channel and the fourth channel is to determine the respective ratios of power between the first frequency and the second frequency in the simultaneous packet. (13) The method of Embodiment 12, comprising determining the power of the first frequency and the second frequency in the simultaneous packet by applying spectral processing to the sampled outputs of the second channel and the fourth channel that appear in the simultaneous packet, respectively. (14) The method according to embodiment 13, wherein the spectral processing is implemented using a Goertzel process based on data indicating the first frequency and the second frequency. (15) The method according to Embodiment 11, wherein the first signal acquisition device and the second signal acquisition device introduce different amplitude gains to the sampled outputs of the first channel and the second channel and the sampled outputs of the third channel and the fourth channel, respectively, which are sampled by them, and determining the synchronization parameter further includes comparing the amplitudes of the sampled outputs of the second channel and the fourth channel to determine the gain difference between the amplitude gains introduced by the first signal acquisition device and the second signal acquisition device to the sampled outputs of the first channel and the third channel, and synchronizing the sampled outputs further includes performing gain compensation to adjust the amplitude of the signal component in at least one of the outputs of the first channel and the third channel to compensate for the gain difference, thereby acquiring the synchronized outputs of the first channel and the third channel as gain-compensated outputs, and the positions of the first position sensor and the second position sensor are determined by processing the gain-compensated outputs of the first channel and the third channel.

[0098] (16) The amplitude gain may differ for different frequencies, the plurality of frequencies of the calibration signal include a plurality of predetermined frequencies that are expected to be received from the first position sensor and the second position sensor via the first channel and the third channel, and the method includes switching the frequency of the calibration signal among the plurality of frequencies at a switching time interval longer than the duration of the packet including the outputs of the second channel and the fourth channel, The method according to Embodiment 15, wherein determining the synchronization parameters includes identifying each pair of packets having the second channel and the fourth channel containing the predetermined frequency for each predetermined frequency among the plurality of predetermined frequencies, and determining the gain difference for each predetermined frequency based on the amplitude of the predetermined frequency in the corresponding pair of packets in each pair, and the synchronization further includes performing the gain compensation for each predetermined frequency. (17) The method according to Embodiment 11, wherein the first and second signal acquisition devices use their respective first and second sampling clocks to sample the outputs of their associated channels with sampling resolution, the first and second sampling clocks are not temporally aligned, thereby introducing a clock skew between the sampled outputs of the first and second channels and the sampled outputs of the third and fourth channels, and determining the synchronization parameter further includes processing at least one pair of simultaneous packets of the outputs of the second and fourth channels sampled by the first and second signal acquisition devices, respectively, to determine the phase of each of at least one frequency contained in the outputs of both the second and fourth channels, and determining the clock skew based on the difference between the respective phases, and synchronizing further includes synchronizing the outputs of the first and third channels to compensate for the clock skew. (18) The method according to Embodiment 11, comprising adjusting the sampling clock rate of one of the first signal acquisition device and the second signal acquisition device to match the sampling clock rate of the other of the first signal acquisition device and the second signal acquisition device. (19) The method according to Embodiment 11, comprising interpolating the signal sampled by at least one of the first signal acquisition device and the second signal acquisition device to adjust their sampling rates so that the sampling rates of the signal sampled by the first signal acquisition device and the second signal acquisition device match, thereby compensating for the different clock rates of the sampling clocks of the first signal acquisition device and the second signal acquisition device.

Claims

1. A location sensing system, a. A calibration signal generation unit configured to generate a calibration signal in the form of a continuous wave (CW) whose frequency can be switched between multiple frequencies, b. A first signal acquisition device configured to sample the output from a first position sensor via a first channel, sample the calibration signal output from the calibration signal generation unit via a second channel, and transmit the sampled outputs from each of the first and second channels in packets. c. A second signal acquisition device configured to sample the output from the second position sensor via a third channel, sample the calibration signal output from the calibration signal generation unit via a fourth channel, and transmit the sampled outputs from the third channel and the fourth channel in packets. d. A synchronous processor, i. Identifying a pair of simultaneous packets between the second channel and the fourth channel, which includes a transition between at least one first frequency and a second frequency among the plurality of frequencies, ii. Determining the respective transition times between the first frequency and the second frequency in the sampled output of the second channel and the fourth channel, iii. A synchronous processor configured to determine, using subpacket resolution, the time shift between the sampling of the output performed by the first signal acquisition device and the sampling of the output performed by the second signal acquisition device, based on the difference between the respective transition times, e. A synchronization device adapted to synchronize the outputs of the first channel and the third channel associated with the first position sensor and the second position sensor based on the time shift, f. A position sensing system comprising a positioning utility adapted to process the synchronized outputs of the first channel and the third channel to determine the positions of the first position sensor and the second position sensor, and to stream the data indicating the positions to a display.

2. The system according to claim 1, wherein determining the respective transition times between the first frequency and the second frequency in the sampled outputs of the second channel and the fourth channel includes determining the respective ratios of power between the first frequency and the second frequency in the simultaneous packet.

3. The system according to claim 2, comprising determining the power of the first frequency and the second frequency in the simultaneous packet by applying spectral processing to the sampled outputs of the second channel and the fourth channel, respectively, that appear in the simultaneous packet, wherein the spectral processing is implemented using a Goertzel process based on data indicating the first frequency and the second frequency.

4. The system according to any one of claims 1 to 3, wherein the first signal acquisition device and the second signal acquisition device introduce different amplitude gains to the sampled outputs of the first channel and the second channel and the third channel and the fourth channel, respectively, sampled by them; the synchronous processor is further configured to compare the amplitudes of the sampled outputs of the second channel and the fourth channel to determine the gain difference between the amplitude gains introduced by the first signal acquisition device and the second signal acquisition device to the sampled outputs of the first channel and the third channel, respectively; the synchronous device is further configured to apply gain compensation to adjust the amplitude of the signal component in at least one of the outputs of the first channel and the third channel to compensate for the gain difference, thereby acquiring the synchronized sampled outputs of the first channel and the third channel as gain-compensated outputs; and the positioning utility is adapted to process the gain-compensated outputs from the first channel and the third channel to accurately determine the positions of the first position sensor and the second position sensor based on the adjusted amplitudes.

5. The system according to claim 4, wherein the amplitude gain may differ for different frequencies, the calibration signal generation unit generates the continuous wave (CW) such that the plurality of frequencies include a plurality of predetermined frequencies that are expected to be received from the first position sensor and the second position sensor via the first channel and the third channel, and switches between the plurality of frequencies with time intervals between frequency switches that are longer than the duration of the packets including the outputs of the second channel and the fourth channel, the synchronous processor is adapted to identify each pair of packets of the second channel and the fourth channel, both packets of each pair include at least one of the predetermined frequencies, and determines the gain difference of the predetermined frequencies based on the amplitude of each predetermined frequency of the corresponding pair of packets, and the synchronous device performs the gain compensation for each predetermined frequency of the predetermined frequencies.

6. The first signal acquisition device and the second signal acquisition device use their respective first and second sampling clocks to sample the outputs of their associated channels at a sampling resolution, and the first and second sampling clocks are not temporally aligned, thereby introducing a clock skew between the sampled outputs of the first and second channels and the sampled outputs of the third and fourth channels, and the synchronous processor, - Processing at least one pair of simultaneous packets of the outputs of the second channel and the fourth channel, sampled by the first signal acquisition device and the second signal acquisition device, respectively, to determine the phase of each of the frequency components contained in the outputs of both the second channel and the fourth channel, - Further configured to determine the clock skew based on the difference between each of the phases and the time shift, The system according to any one of claims 1 to 3, wherein the synchronization device is further adapted to synchronize the timing of the output of the first channel with the timing of the output of the third channel in order to compensate for the clock skew between the first signal acquisition device and the second signal acquisition device.

7. - Adjusting the sampling clock rate of one of the first signal acquisition device and the second signal acquisition device to match the sampling clock rate of the other of the first signal acquisition device and the second signal acquisition device, The system according to any one of claims 1 to 3, further comprising a rate controller adapted to perform at least one of the following: interpolating a signal sampled by at least one of the first signal acquisition device and the second signal acquisition device to match the sampling rate in the signal sampled by the first signal acquisition device and the second signal acquisition device, thereby compensating for different clock rates of the sampling clocks of the first signal acquisition device and the second signal acquisition device.

8. A catheter-based mapping and ablation system comprising the positioning system described in any one of claims 1 to 3.

9. A method of sensing location, a. To generate a calibration signal in the form of a continuous wave (CW) whose frequency can be switched between multiple frequencies, b. The first signal acquisition device samples the output from the first position sensor via the first channel, samples the calibration signal output from the calibration signal generation unit via the second channel, and transmits the sampled outputs of the first channel and the second channel in a first packet. c. The second signal acquisition device samples the output from the second position sensor via the third channel, samples the calibration signal output from the calibration signal generation unit via the fourth channel, and transmits the sampled outputs from the third channel and the fourth channel in a second packet. d. Determining a synchronization parameter for synchronizing the signals sampled from the first channel and the third channel based on the calibration signals sampled from the second channel and the fourth channel, wherein determining the synchronization parameter is: i. Identifying a pair of simultaneous packets containing sampled outputs of the second channel and the fourth channel, wherein each packet has a transition between at least one first frequency and a second frequency among the plurality of frequencies, ii. Determining the respective transition times between the first frequency and the second frequency in the sampled output of the second channel and the fourth channel, iii. Based on the difference between the respective transition times, determine a time shift, with subpacket resolution, between the sampling of the output performed by the first signal acquisition device and the sampling of the output performed by the second signal acquisition device. e. Synchronizing the outputs of the first channel and the third channel associated with the first position sensor and the second position sensor based on the time shift, f. A method comprising streaming data indicating the simultaneous positions of the first position sensor and the second position sensor, determined based on the synchronized outputs of the first channel and the third channel, to a display.

10. The method according to claim 9, wherein determining the respective transition times between the first frequency and the second frequency in the sampled outputs of the second channel and the fourth channel includes determining the respective ratios of power between the first frequency and the second frequency in the simultaneous packet.

11. The method according to claim 10, comprising determining the power of the first frequency and the second frequency in the simultaneous packet by applying spectral processing to the sampled outputs of the second channel and the fourth channel, respectively, that appear in the simultaneous packet, wherein the spectral processing is implemented using a Goertzel process based on data indicating the first frequency and the second frequency.

12. The method according to any one of claims 9 to 11, wherein the first signal acquisition device and the second signal acquisition device introduce different amplitude gains to the sampled outputs of the first channel and the second channel and the sampled outputs of the third channel and the fourth channel, respectively, which are sampled by them, and determining the synchronization parameter further includes comparing the amplitudes of the sampled outputs of the second channel and the fourth channel to determine the gain difference between the amplitude gains introduced by the first signal acquisition device and the second signal acquisition device to the sampled outputs of the first channel and the third channel, and synchronizing the sampled outputs further includes performing gain compensation to adjust the amplitude of the signal component in at least one of the outputs of the first channel and the third channel to compensate for the gain difference, thereby acquiring the synchronized outputs of the first channel and the third channel as gain-compensated outputs, and the positions of the first position sensor and the second position sensor are determined by processing the gain-compensated outputs of the first channel and the third channel.

13. The amplitude gain may differ for different frequencies, the plurality of frequencies of the calibration signal include a plurality of predetermined frequencies that are expected to be received from the first position sensor and the second position sensor via the first channel and the third channel, and the method includes switching the frequency of the calibration signal among the plurality of frequencies at a switching time interval longer than the duration of the packet including the outputs of the second channel and the fourth channel. The method according to claim 12, wherein determining the synchronization parameters includes identifying each pair of packets having the second channel and the fourth channel containing the predetermined frequency for each predetermined frequency among the plurality of predetermined frequencies, and determining the gain difference for each predetermined frequency based on the amplitude of the predetermined frequency in the corresponding pair of packets in each pair, and the synchronization further includes performing the gain compensation for each predetermined frequency.

14. The method according to any one of claims 9 to 11, wherein the first signal acquisition device and the second signal acquisition device use their respective first sampling clock and second sampling clock to sample the outputs of their associated channels with sampling resolution, the first sampling clock and the second sampling clock are not temporally aligned, thereby introducing a clock skew between the sampled outputs of the first and second channels and the sampled outputs of the third and fourth channels, and determining the synchronization parameter further comprises processing at least one pair of simultaneous packets of the outputs of the second and fourth channels sampled by the first signal acquisition device and the second signal acquisition device, respectively, to determine the phase of each of at least one frequency contained in the outputs of both the second and fourth channels, and determining the clock skew based on the difference between the respective phases, and synchronizing further comprises synchronizing the outputs of the first and third channels to compensate for the clock skew.

15. - Adjusting the sampling clock rate of one of the first signal acquisition device and the second signal acquisition device to match the sampling clock rate of the other of the first signal acquisition device and the second signal acquisition device, The method according to any one of claims 9 to 11, comprising at least one of: interpolating the signal sampled by at least one of the first signal acquisition device and the second signal acquisition device to adjust their sampling rates so that the sampling rates of the signal sampled by the first signal acquisition device and the second signal acquisition device match, thereby compensating for the different clock rates of the sampling clocks of the first signal acquisition device and the second signal acquisition device.

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