Magnetic flexible catheter tracking system and method using digital magnetometers

BACKGROUND

0001Known Electromagnetic (EM) localization systems are sometimes used in the Medical field for tracking a small catheter inside the body. The reason EM systems are highly suitable for such applications, is because the body is transparent to EM near-fields. This allows for a catheter or any other tool to be tracked in real-time inside (or outside) the body without the need for a line-of-sight and without the use of any potentially harmful imaging modalities such as X-ray or Computed Tomography (CT).

0002Some known system may include an EM field sensor/receiver and an EM field generator/transmitter that transmits multiple different alternating (“AC”) EM fields, for example sinusoidal EM fields. The receiver usually receives a combination of the multiple EM fields from the transmitter, and differentiates between the different fields, for example by performing a Fast Fourier Transform (FFT) and/or a Discrete Fourier Transform (DFT) or any other suitable method. By analyzing the phases and/or amplitudes, the receiver identifies a unique EM signature associated with a specific position and orientation, e.g. a specific six-degrees-of-freedom (6DOF) state, for example three coordinates of position and three angles of orientation. In other systems the EM signature is used to recover only five-degrees-of-freedom (5DOF). In these systems the roll angle of the sensor is usually absent. In other systems only the position may be solved (3DOF) and the orientation of the sensor remains unknown.

0003In order to enable decomposition of the received combination of fields and/or distinguishing between the received fields and identification of a unique 6DOF (or 5DOF) state of the monitored object, the transmitter needs to transmit multiple EM sinusoidal field signals in carefully chosen frequencies, for example so that the sinusoidal field signals are orthogonal to each other. Some systems may include N transmitting coils which generate EM fields of different geometry. The number N should be large enough to enable identification of the 6DOF (or 5DOF) state of the monitored object. In other systems, there may be a smaller number of coils that generate orthogonal (at the source) and/or otherwise highly distinctive EM field signals. In order to ease the separation between the fields, and increase the operation rate of the system, the system may usually use high-frequency EM fields, in the kHz scale.

0004In a traditional EM-tracked catheter setting, a catheter would have one or more micro coils placed at its tip. For example, three micro-sized coils need to be placed at the tip of the catheter, traditionally in an orthogonal manner, and wires need to be pulled outside to an external DSP. In some specialized systems a single coil is used rather than three orthogonal coils, but this requires a specialized EM field generator to generate many different unique fields, and in addition it can only provide localization of up to five degrees-of-freedom (with roll angle missing). In general, one-coil systems are inferior in terms of accuracy and overall stability. The EM field generator would generate a high-frequency (>1 kHz, for example) alternating magnetic field which would induce electromotive force (EMF) on the catheter's coils (by Faraday's law of induction). The coils are connected through wires to an external digital signal processor (DSP) unit which is responsible for amplifying the induced voltage, then sampling it, for example by using an analog-to-digital (AMD) converter. A dedicated processor would then analyze the sensed signal, decompose it using FFT or DFT (or any other suitable method) into separate sine wave amplitudes and pass the DFT results to another processing stage which is responsible for translating the computed field amplitudes into a position and orientation of the sensor in three-dimensional space, relative to the field generator.

0005The DSP unit should contain high-quality low-noise amplifiers in order to be able to enhance the tiny voltages which are picked up on the micro coils for the A2D converter to be able to sample them with good SNR (Signal-Noise Ratio). Every such coil requires a separate processing channel with a dedicated high-quality amplifier and A2D input. In addition, good signal-noise ratio (SNR) is hard to maintain; the tiniest noise might be amplified and obscure the signal of interest. For example, the wires connecting the coils to the DSP might form a loop through which some magnetic flux flows and which therefore picks up some amount of parasitic, undesired signal from the transmitted fields. This requires the wires to be wound across the catheter in a twisted pair fashion. In addition to the wires, the connector which connects the catheter to the DSP might also form an undesired loop which is able to pick up some amount of parasitic signal. A traditional EM catheter therefore involves a complex design, with a special, complicated and expensive, complementary DSP unit. The complexity of such system grows almost linearly with the number of desired sensors (the number of coils, number of twisted-pair wires, number of DSP input channels which include more expensive amplifiers and A2D). For all these reasons, one should appreciate why constructing a traditional EM catheter with more than just a very few EM sensors is virtually impractical.

0006Some devices such as mobile phones include an Inertial Measurement Unit (IMU) that provides information of the device's motion and pose. Usually, the IMU includes digital sensors such as a 3-axis accelerometer and a 3-axis gyroscope, and in many cases it also includes a 3-axis magnetometer. The accelerometer senses accelerations in local 3D coordinates. In a normal setting the accelerometer mainly senses the gravity force vector (plus some local, linear acceleration which can be filtered out using various sensor-fusion methods) and therefore may enable detection of partial orientation, for example of the device's screen (landscape/portrait). The gyroscope senses angular velocity of the device. In many applications, the data received from the accelerometer and the gyroscope are combined to provide robust orientation tracking of the device. Since these two sensors have no reference except for the gravity force (which points to the sky), the orientation computed from the accelerometer and the gyroscope usually drifts slowly around the gravity vector. In this sense, orientation tracking based on accelerometer and gyroscope alone is considered “drifting”, since it has no stable reference. The magnetometer may be used to sense the DC Earth's magnetic field, for example using Hall effect sensors, magneto-resistive sensors, magneto-inductive sensors, and/or by any other suitable sensor type. The sensed DC Earth's magnetic field may be used to correct drifting of the accelerometer and gyroscope orientation detection in Earth coordinates. However, the magnetometer readings are often distorted by various elements in its environment, such as nearby metals (soft-iron, hard-iron distortion). In addition, low-cost magnetometer sensors are prone to bias calibration problems, where the internal bias of the sensor drifts over time. Therefore, in many applications the magnetometer data is ignored and orientation is detected by the accelerometer and gyroscope only, although the identified orientation usually drifts over time with respect to Earth's North, since the magnetometer data is dismissed and no other sensor is used as an additional reference for orientation. While the IMU is mostly used for orientation detection, it may also be used for relative positioning. Using sensor fusion methods, the local acceleration may be extracted from the accelerometer readings (subtracting the gravity force). It can be then integrated over short time periods to compute the velocity of the device. Double integration gives relative position of the device. These methods, however, are highly sensitive to bias noise and are therefore usually only used with high-end highly accurate IMU sensors or over very short time periods (for example, for motion gesture detection). While the IMU can be used in a normal setting for computing absolute orientation of a device relative to Earth's coordinates (by using data from all 3 sensors: accelerometer, gyroscope and magnetometer), none of the IMU readings provide any information of device's position relative to any absolute reference. In order to use the IMU for accurate absolute positioning, some external reference must be added.

SUMMARY

0007An aspect of some embodiments of the present invention provides a method for magnetic tracking of a flexible catheter device or another flexible elongated device, the method comprising: receiving by a host server a plurality of sensed values of a local magnetic field, sensed by a respective plurality of sensors, wherein the host server is optionally included in a controller of the sensors, the sensors are located along a flexible tube of a device, wherein the sensed values are at least partially due to at least one alternating magnetic field generated by at least one magnetic field generator, the source amplitude and frequency of each generated magnetic field are given to the host server; and calculating by the host server, based on the sensed magnetic field values and the given source amplitude and frequency of each generated magnetic field, a localization of the flexible tube.

0008Optionally, the method includes receiving by a host server, from at least one generator of an alternating magnetic field, a momentary phase value of the generated magnetic field; associating by the host server between the momentary phase value and at least some of the sensed magnetic field values received from the sensors; and calculating by the host server, based on the magnetic field values and the associated phase value, a localization of the flexible tube.

0009Optionally, the associating is based on a corresponding clock reading shared or synchronized among the magnetic field generator, the controller of the sensors and the host server.

0010Optionally, the phase data is received from the at least one generator in full rate of a magnetometer located at the at least one generator.

0011Optionally, the clock reading is shared by the magnetic field generator or by a clock source shared among the field generator, a controller of the sensors and the host server.

0012Optionally, the method includes receiving from the at least one generator an amplitude value of the generated magnetic field at the source.

0013Optionally, the calculating includes calculation of position and orientation of each of the plurality of sensors.

0014Optionally, the calculating includes using an Extended Kalman filter for fusing sensor data and imposing a motion model or shape constraints on the calculations.

0015Optionally, wherein at least one of the sensors is a sensor bundle, and the calculation incorporates accelerometer or gyroscope readings of corresponding sensors included in the sensor bundle.

0016Optionally, the calculation incorporates known structural relationships between the sensors to calculate an estimation of the position, orientation or curve of the tube as a whole.

0017Optionally, the sensed values are at least partially due to at least two generated magnetic fields generated by at least two corresponding generators.

0018Optionally, the at least two generated magnetic fields operate at different frequencies.

0019Optionally, the at least two generators share the same clock or have synchronized clocks or share a clock source.

0020Another aspect of some embodiments of the present invention provides a system for magnetic tracking of a flexible catheter device or another flexible elongated device, the system comprising: at least one generator, each configured to generate an alternating magnetic field wherein each generated magnetic field has a determined source amplitude and frequency; a device comprising: a flexible tube; a plurality of sensors, the sensors are located along the flexible tube, each configured to communicate sensed values of a local magnetic field, wherein the sensed values are at least partially due to the generated magnetic field; and a host server configured to: receive the sensed local magnetic field values from the corresponding sensors; and calculate, based on the magnetic field values and the determined source amplitude and frequency, a localization of the flexible tube, wherein the host server is optionally included in a controller of the sensors.

0021Optionally, the host server is configured to receive, from at least one generator of an alternating magnetic field, a momentary phase value of the generated magnetic field; associate by the host server between the momentary phase value and at least some of the sensed magnetic field values received from the sensors; and calculate by the host server, based on the magnetic field values and the associated phase value, a localization of the flexible tube.

0022Optionally, the associating is based on a corresponding clock source reading shared among the magnetic field generator, a controller of the sensors and the host server.

0023Optionally, the device further comprises a flexible PCB along the tube, wherein the sensors are located along the flexible PCB.

0024Optionally, the flexible PCB is wrapped in a helix manner on a wall of the tube.

0025Optionally, the device further comprises a communication bus configured to carry the sensed values data digitally from the plurality of sensors towards the server.

0026Optionally, the communication bus includes up to four wire lines that may carry the sensed values digital data from and provide power to the plurality of sensors.

0027Optionally, the at least one generator comprises an internal clock and is configured to share its clock readings with the sensors and with the host server.

0028Optionally, the at least one generator comprises a magnetometer configured to detect the phase data.

0029Optionally, at least one of the sensors is a sensor bundle comprising accelerometer or gyroscope sensors.

0030Optionally, the system includes at least two generators that generate at least two respective magnetic fields that operate at different frequencies.

0031Optionally, the at least two generators share the same clock or have synchronized clocks or share a clock source.

0032Optionally, the at least one generator comprises at least one permanent magnet and a motor device that rotates the magnet in a determined frequency.

0033Optionally, the at least one generator comprises an electromagnetic coil that generates a sinusoidal electromagnetic field at a specific known frequency.

0034Optionally, the device includes a plurality of dipole magnets positioned between the sensors.

0035Optionally, the dipole magnets are positioned in equal distances and oriented so that two magnets located at two sides of a sensor have opposite dipole directions, when the tube is in a straight state.

BRIEF DESCRIPTION OF THE DRAWINGS

0036Some non-limiting exemplary embodiments or features of the disclosed subject matter are illustrated in the following drawings.

0037In the drawings:

0038<figref idref="DRAWINGS">FIG. 1</figref> is a schematic illustration of a catheter tracking system for tracking by digital magnetometers, according to some embodiments of the present disclosure;

0039<figref idref="DRAWINGS">FIG. 2</figref> is a schematic illustration of an exemplary magnetic field generator/transmitter for tracking by digital magnetometers, according to some exemplary embodiments of the present disclosure;

0040<figref idref="DRAWINGS">FIG. 3</figref> is a schematic flowchart illustrating a method for tracking by digital magnetometers according to some embodiments of the present disclosure;

0041<figref idref="DRAWINGS">FIG. 4</figref> is a schematic illustration of a catheter according to some embodiments of the present disclosure;

0042<figref idref="DRAWINGS">FIG. 5</figref> is a schematic illustration of a catheter device, according to some other embodiments of the present disclosure; and

0043<figref idref="DRAWINGS">FIG. 6</figref> is a schematic illustration of a catheter device, according to some other embodiments of the present disclosure.

0044With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the disclosure. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the disclosure may be practiced.

0045Identical or duplicate or equivalent or similar structures, elements, or parts that appear in one or more drawings are generally labeled with the same reference numeral, optionally with an additional letter or letters to distinguish between similar entities or variants of entities, and may not be repeatedly labeled and/or described. References to previously presented elements are implied without necessarily further citing the drawing or description in which they appear.

0046Dimensions of components and features shown in the figures are chosen for convenience or clarity of presentation and are not necessarily shown to scale or true perspective. For convenience or clarity, some elements or structures are not shown or shown only partially and/or with different perspective or from different point of views.

DETAILED DESCRIPTION

0047Before explaining at least one embodiment of the disclosure in detail, it is to be understood that the disclosure is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or the Examples. The disclosure is capable of other embodiments or of being practiced or carried out in various ways.

0048Some embodiments of the present disclosure provide a magnetic full-curve catheter tracking system. A magnetic field generator/transmitter according to some embodiments of the present disclosure may induce electromagnetic field on a plurality of magnetometers placed along a flexible catheter tube. In some embodiments, the provided system may include at least one special magnetic field generator and/or use a special magnetic field generation and/or transmission method. A magnetic field generator/transmitter provided according to some embodiments of the present invention may consist of low-cost components.

0049The provided system may receive sensor readings of local electromagnetic field values from the plurality of magnetometers, and based on the received readings calculate a full-curve localization of the catheter tube along its length. This is in contrast to traditional EM catheter tracking systems in which, usually, only the catheter tip is tracked. In some embodiments, the provided system may calculate and/or identify 6DOF localization, e.g. three-dimensional position and orientation, of each magnetometer based on its magnetic sensor reading, relative to the magnetic field generator(s). In some embodiments, the sensing radius of the magnetometers is up to about 50 centimeters. Accordingly, in some embodiments, the distance of the at least one magnetic field generator from the plurality of magnetometers is up to 50 centimeters.

0050According to some embodiments, the provided system includes a plurality of digital magnetometers, for example off-the-shelf magnetic sensors, for example similar to or the same magnetometers included in IMUs. In some embodiments, full IMU sensor bundles are used. The digital magnetometers may have a small footprint and/or size, suitable for catheters for insertion into various body cavities. For example, the magnetometers are insertable to a catheter tube and/or to a body cavity and/or on the catheter tube wall. For example, the plurality of magnetometers may be placed, for example in an integrated circuit and/or silicon die, on a flexible printed circuit board (PCB) along the catheter tube. The plurality of magnetometers may be packaged, for example in an Ultra-Small Wafer Level BGA (Ball grid array) package. This may allow for placing them on a very thin flexible PCB.

0051A magnetometer, as referred to throughout the present description, usually operates at a sampling rate of an order of magnitude of hundreds of Hz, for example of about 100 Hz and/or up to 500 Hz-1000 Hz. In order to use a direct-current (DC) magnetometer (one that measures DC magnetic fields) as an alternate-current (AC) magnetic sensor (one that is intended for use with AC magnetic fields), the sensed AC magnetic field may be of a frequency significantly smaller than the magnetometer's sampling rate, e.g. an order of magnitude smaller. The sensed magnetic fields should be in a range detectable by the DC magnetometer. For example, the sensed magnetic field should be about ten times the magnetometer's sensitivity when generated, and take into account also the noise level, in order to be detected by the magnetometer. For example, a DC magnetometer can detect magnetic fields of between a few μT to a few thousands of μT (For example, between 1 to 4000 μT) with sensitivity, e.g. resolution, of about 0.1μT. Since a magnetic field's strength is inversely proportional to the cube of the distance between the dipole source and the receiver, the sensing range should have a factor −10 between the minimal to the maximal distances, for example 10 cm to 1 m or 1 m to 10 m, etc.

0052According to some embodiments, the plurality of magnetometers are placed along and transmit the sensed values by a same data bus, requiring, for example, as few as four or less electrical wires pulled along the catheter tube, no matter how many magnetometers are placed along and/or transmitting the data by the data bus. This is in contrast to traditional analog catheter tracking systems, that may require a number of wires that grows linearly with the number of magnetic sensors.

0053Some embodiments of the present disclosure provide a method for localization calculation that may calculate the full-curve localization of the catheter curve in a rate greater than 30 Hz. This rate is suitable for most real-time medical applications. Therefore, some embodiments of the present invention provide a solution to the problem of acquiring real-time full-curve localization of a small-diameter catheter, without the high costs of traditional EM sensors and DSPs. Additionally, in some embodiments the provided system has low power consumption, for example both on the receiving and the transmitting end, which may allow for a wireless and/or battery operated full-curve catheter localization system of a significantly small footprint.

0054The ability to construct a full curve tracked catheter at low costs and uncomplicated configuration, as provided by some embodiments of the present disclosure, is important for many potential medical applications.

0055Reference is now made to <figref idref="DRAWINGS">FIG. 1</figref>, which is a schematic illustration of a catheter tracking system <b>100</b> for tracking by digital magnetometers, according to some embodiments of the present disclosure. According to some embodiments of the present disclosure, system <b>100</b> provide a solution for full-curve catheter localization. System <b>100</b> may include a catheter <b>30</b>, a hardware host server <b>10</b> and at least one magnetic field generator/transmitter <b>20</b>, for example, magnetic field generators/transmitters <b>20</b><i>a </i>and <b>20</b><i>b</i>. As described herein, system <b>100</b> may provide a full curve localization of catheter <b>30</b> to its length. In some embodiments of the present disclosure host server <b>10</b> is included in a controller in catheter <b>30</b>, e.g. all the functionalities of host server <b>10</b> described herein are performed by a controller in catheter <b>30</b>. The terms controller and microcontroller are sometimes used interchangeably throughout the present disclosure and may also mean or include a microprocessor.

0056Transmitter <b>20</b> may generate a magnetic field. For example, transmitter <b>20</b> is an electromagnetic generator of magnetic fields, for example including at least one electromagnetic coil. Each generator <b>20</b> may generate an alternating magnetic field. Each generated magnetic field has a determined source amplitude and frequency. In some embodiments, transmitter <b>20</b> may include a sensor that senses a momentary phase of the generated EM field or computes the momentary phase of the generated EM field by using a synchronized EM field generator driver and communicates to host server <b>10</b>, for example, periodically, the momentary phase value along with a timestamp.

0057In some embodiments of the present disclosure, transmitter <b>20</b> may include at least one rotating magnet, as shown in more detail in <figref idref="DRAWINGS">FIG. 2</figref>. As described in more detail herein, in some embodiments, transmitter <b>20</b> may include a sensor that senses a momentary phase of the rotating magnet or computes the momentary phase of the rotating magnet by using a synchronized motor driver and communicates to host server <b>10</b>, for example, periodically, the momentary phase value along with a timestamp.

0058Catheter <b>30</b> may include a microcontroller <b>32</b>, a flexible tube <b>36</b> and a plurality of magnetometer sensors <b>31</b>, for example implemented upon a flexible PCB (shown in more detail in <figref idref="DRAWINGS">FIG. 4</figref>) along tube <b>36</b>. Magnetometer sensors <b>31</b> may be placed in predefined locations along tube <b>36</b> and/or in predefined distances between them. According to some embodiments, magnetometer sensors <b>31</b> may be or include off-the-shelf magnetic sensors, for example similar to or the same magnetometers included in IMUs or standalone off-the-shelf magnetic sensors. In some embodiments, each of magnetometer sensors <b>31</b> may be or include a full IMU sensor bundle.

0059Each of magnetometer sensors <b>31</b> may sense a corresponding local magnetic field value resulting from the magnetic field generated by transmitter <b>20</b>. Host server <b>10</b>/microcontroller <b>32</b> may receive the magnetic field value from sensors <b>31</b> and/or microcontroller <b>32</b> may communicate to host server <b>10</b>/microcontroller <b>32</b> the sensed value along with a timestamp. Microcontroller <b>32</b> may be located at a proximal end of catheter <b>30</b>, e.g. in a communication path between sensors <b>31</b> and host server <b>10</b>. For example, microcontroller <b>32</b> may receive and/or gather at least one local and momentary magnetic field values from respective at least one sensor <b>31</b>, for example values sensed in a certain moment, and transmit the gathered values along with a corresponding timestamp, for example, over USB, wireless communication, etc. For example, microcontroller <b>32</b> may communicate the gathered sensed values along with identification of the respective sensing sensors <b>31</b>, for example for each sensed value. As described in more detail herein, sensors <b>31</b> may be communicationally connected by a same data bus <b>34</b> placed along tube <b>36</b>, to microcontroller <b>32</b> and/or to host server <b>10</b>. In some embodiments of the present disclosure, at least some of the functionalities of host server <b>10</b> described throughout the present description are performed by microcontroller <b>32</b>. In some embodiments, all functionalities of host server <b>10</b> are performed by microcontroller <b>32</b> and/or processor/controller <b>27</b> described with reference to <figref idref="DRAWINGS">FIG. 2</figref>.

0060Flexible tube <b>36</b> may be positioned in various positions and may have various momentary curve shapes, for example according to a shape of a body organ it is inserted into and/or according to obstacles the catheter tube encounters.

0061Host server <b>10</b>/microprocessor <b>32</b> may include at least one hardware processor <b>12</b> and/or at least one hardware memory <b>14</b>. Memory <b>14</b> may include a tangible non-transitory processor readable storage medium, storing processor readable program instructions thereon, for causing processor <b>12</b> to carry out aspects of the present disclosure. System <b>100</b> may include a display device <b>16</b>, configured to receive data and/or instructions from host server <b>10</b> and display information according to the received data and/or instructions. Display device <b>16</b> may show, for example, navigational instructions for instructing the physician to reach a certain point of interest inside the body.

0062Magnetometer sensors <b>31</b> may be and/or include digital magnetometers configured to provide sensor digital output, may be low-cost and/or may have a small footprint. In some embodiments, each of sensors <b>31</b> may be or include a standard IMU, which may include a magnetometer, an accelerometer and/or a gyroscope. The plurality of sensors <b>31</b> may be placed along a same digital communication bus <b>34</b> and/or communicate the sensor digital output by same digital communication bus <b>34</b> to microcontroller <b>32</b> and/or to server <b>10</b>. For example, sensors <b>31</b> may sense along the curve of tube <b>36</b> local electromagnetic field values simultaneously or within a very short period of milliseconds, and/or may transmit these values by the same bus <b>34</b> to microcontroller <b>32</b> and/or to server <b>10</b>, for example simultaneously or within a very short period of up to a few milliseconds or a few tens of milliseconds. Host server <b>10</b>/microprocessor <b>32</b> may receive the sensed local magnetic field values from the corresponding sensors <b>31</b>, and/or may calculate a localization of flexible tube <b>36</b>, for example based on the sensed magnetic field values and the determined source amplitude and frequency of the magnetic field generated by transmitter <b>20</b>

0063Each sensor <b>31</b> may be identified separately by microcontroller <b>32</b> and/or server <b>10</b>. For example, microcontroller <b>32</b> and/or server <b>10</b> may relate each received electromagnetic field value to the respective sensor <b>31</b> that sensed this value. For example, microcontroller <b>32</b> may transmit the sensed value to server <b>10</b> along with an identifier code that identifies the sensor that sensed this value. In some embodiments, the sensed value and/or identifier code is sent along with a timestamp which, for example, attests to the reading time of the sample. As described in more detail herein, host server <b>10</b>/microprocessor <b>32</b> may calculate 6DOF localization of the respective sensor based on the received sensed value and/or timestamp and/or the phase data received from at least one generator <b>20</b>, and/or calculate a full-curve position of catheter tube <b>36</b> based on the plurality of sensed values received from the plurality of sensors <b>31</b>. For example, the calculation is made by imposing some shape and/or curvature constraints. In some embodiments of the present invention, system <b>100</b> may include any suitable number of sensors <b>31</b> along tube <b>36</b>, for example with no substantial increase to the complexity of the system, for example since sensors <b>31</b> transmit the sensed values by the same data bus <b>34</b>. For example, in some embodiments, no DSP input channels are required in order to amplify, sample and transmit the magnetic values from sensors <b>31</b> to microcontroller <b>32</b> and/or server <b>10</b>.

0064In some embodiments, system <b>100</b> is synchronous, e.g. shares a single clock between its components. For example, generator/transmitter <b>20</b> may include an inner clock, and/or may share its clock readings with sensors <b>31</b>, microcontroller <b>32</b> and/or with server <b>10</b> and/or with other generator/transmitters, as described in more detail herein. In some embodiments of the present disclosure, at least some of the components of system <b>100</b> synchronize their respective clocks with an external clock. Microcontroller <b>32</b> may receive from sensors <b>31</b> their respective sensed values. For example, microcontroller <b>32</b> may receive via data bus <b>34</b> the sense data sampled by sensors <b>31</b> and written on data bus <b>34</b>. In some embodiments, microcontroller <b>32</b> transmits the data to host <b>10</b>, for example along with a corresponding timestamp. For example, the timestamp corresponds to respective clock readings received from transmitter <b>20</b>, or is based on another shared clock. Server <b>10</b> may receive the data from transmitter <b>20</b> and sensors <b>31</b> and/or synchronize the data according to the timestamps. For example, the shared or external clock may include a dedicated crystal oscillator physically connected to all devices, a USB hub clock shared among all devices connected to the USB hub, a clock generated by an RF (radio-frequency) main source and shared wirelessly among RF devices, or a GPS clock, sensed by at least some devices in system <b>100</b>.

0065In some exemplary embodiments, transmitter <b>20</b> may use electromagnetic coils to generate low-frequency magnetic fields. The frequency may be low enough (for example, lower than 500 Hz) to be fully matched by the sampling rate of sensors <b>31</b>, e.g. sensors <b>31</b> may sample the magnetic fields in at least a minimum rate required for retaining all the required information, for example amplitude, frequency and/or phase, about the sensed magnetic field. The generated magnetic fields may be strong enough within the sensing radius (for example, stronger than 1 uT) to get quality samples, in magnetometer's sensitivity and/or signal-to-ratio (“SNR”) sense. Sensor <b>31</b> may collect enough samples to perform discrete Fourier transform (“DFT”) or similar algorithms to separate between the generated magnetic fields and solve for 6DOF localization of sensors <b>31</b> and/or tube <b>36</b>. In some cases, in order to provide low-latency, high-rate 6DOF solutions, phase information may be provided by transmitter <b>20</b> and synced between transmitter <b>20</b> and sensor <b>31</b> and/or microcontroller <b>32</b>. This way, microcontroller <b>32</b> and/or host server <b>10</b> may be aware of a momentary phase of the generated magnetic field, and may be able to produce rapid 6DOF solutions by using the synchronized phase information and timestamps in an extended Kalman filter setting (as explained herein).

0066As described in more detail herein, for example with reference to <figref idref="DRAWINGS">FIG. 2</figref>, according to some embodiments of the present invention, magnetic field generator/transmitter <b>20</b> includes a rotating magnet and a rotary sensor, e.g. a magnetometer, that senses the momentary phase of the magnet rotation, e.g. where the magnet is located in its rotational orbit in a given moment. For example, the rotary sensor is configured to communicate to server <b>10</b> the momentary phase information, for example along with respective timestamps of the clock readings, for example in full rate.

0067For example, according to their matching timestamps, server <b>10</b> may relate a certain phase state of the generated magnetic field(s) to corresponding local magnetic field readings received from sensors <b>31</b>, which were sensed and/or transmitted at the same time as the phase reading. Based on the magnetic field readings and the related momentary phase reading(s), server <b>10</b>/microprocessor <b>32</b> may calculate the full-curve catheter localization, for example in real time. For example, host server <b>10</b>/microprocessor <b>32</b> may receive from at least one generator <b>20</b> of an alternating magnetic field, a momentary phase value of the generated magnetic field, may associate between the momentary phase value and at least some of the sensed magnetic field values received from sensors <b>31</b>, and/or may calculate, based on the magnetic field values and the associated phase value, a localization of flexible tube <b>36</b>.

0068It will be appreciated that system <b>100</b> may include a plurality of catheters <b>30</b>, and that server <b>10</b> may calculate the full-curve catheter localizations for a plurality of catheters <b>30</b>, for example concurrently.

0069Reference is now made to <figref idref="DRAWINGS">FIG. 2</figref>, which is a schematic illustration of an exemplary magnetic field generator/transmitter <b>20</b> for tracking by digital magnetometers, according to some exemplary embodiments of the present disclosure. Generator/transmitter <b>20</b> may include at least one permanent magnet <b>22</b>, a processor/controller <b>27</b> having an inner clock <b>28</b> and a communication interface <b>29</b>, a motor device <b>21</b>, a magnetometer <b>25</b>, and a power source <b>24</b>.

0070The configuration of generator/transmitter <b>20</b> as shown in <figref idref="DRAWINGS">FIG. 2</figref> and described herein is not required by some embodiments of the present invention, and other suitable configurations, components and/or structures of generator/transmitter <b>20</b> are possible, according to some embodiments of the present invention.

0071In some embodiments, generator/transmitter <b>20</b> generates a low-frequency electromagnetic field of, for example, less than 60 Hz, having strength of, for example, about 1 uT or stronger at, for example, about 1 meter from the transmitter. Usually, in order to produce such a strong field by an AC current according to Ampere's law, a very large transmitter with very high-power consumption is required. However, according to some embodiments of the present invention, generator/transmitter <b>20</b> includes at least one permanent magnet <b>22</b> that generates the magnetic field. By producing the magnetic field by at least one permanent magnet, the magnetic field produced by generator/transmitter <b>20</b> may be about a hundred times stronger than a magnetic field produced by AC electric current, by a transmitter of similar dimensions, and results in an extremely low-power transmitter. The material of the magnet is chosen to maximize the generated magnetic field strength compared to the size of generator/transmitter <b>20</b>. For example, generator/transmitter <b>20</b> may include a rare-Earth magnet, for example a Neodymium magnet or magnet of another suitable material.

0072In order to produce an AC magnetic field, in some embodiments of the present invention, magnet <b>22</b> is mounted on an axis rotated, for example, by a motor device <b>21</b>, for example a direct-current (DC) motor, or by electromagnetic coils wound around magnet <b>22</b> which produce a weak AC field, strong enough to rotate the magnet at their center with their applied torque, or by off-the-shelf electromagnetic single-axis coils placed near magnet <b>22</b> which produce a weak AC field, strong enough to rotate the magnet with their applied torque, or any other suitable device, at a desired operating frequency f. Thus, for example, rotating magnet <b>22</b> results in an AC magnetic field in the surrounding space. The magnetic field generated by the rotating magnet <b>22</b> may be expressed as the superposition of two AC magnetic fields of frequency f and orthogonal phases and generated by two separate virtual coils x and y:

0000<br /><i>B</i>(<i>{right arrow over (r)},t</i>)=<i>B</i>_x(<i>{right arrow over (r)}</i>)cos(ϕ(<i>t</i>))+<i>B</i>_y(<i>{right arrow over (r)}</i>)sin(ϕ(<i>t</i>))

0000where ϕ(t) is the phase within the rotation of the magnet <b>22</b>. In a perfect setting ϕ(t)=ωt, that is, the transmitter produces perfectly fixed frequency ω=2ζf, but in more practical scenarios this is just an approximation which can be expressed as: ϕ(t)≈ω. B_xis the magnetic dipole field due to the ‘x’ virtual coil and B_yis the magnetic dipole field due to the ‘y’ virtual coil. In other words, B_x, B_yare two magnetic fields corresponding to virtual ‘x’ and ‘y’ axes of the rotating magnet <b>22</b>, respectively. It will be appreciated that according to some embodiments of the present invention, magnet <b>22</b> may be controlled to move according to other, for example more complicated, motion models. For example, magnet <b>22</b> may be rotated about a time-varying axis direction. For example, the movement of magnet <b>22</b> may include a combination of rotational motion about a fixed axis and a periodic linear motion parallel to the fixed axis. Other motion models are also in the scope of the present invention. In some embodiments, the more complicated motion models may add an additional orthogonal virtual coil ‘z’ whose dipole field is denoted B_z({right arrow over (r)}) and that may enhance the position and orientation calculations. This is while keeping the ability of magnetometer <b>25</b> to detect the momentary position, e.g. phases, of magnet <b>22</b>.

0073In some embodiments, magnet <b>22</b> may be controlled by generator <b>20</b> to rotate about an additional, secondary, axis, to obtain a more complex magnetic field sensed by receiver <b>20</b> and thus, for example, provide more information for the position and orientation calculation. Magnetometer <b>25</b> may sense the corresponding generated magnetic fields and accordingly calculate momentary phases of magnet <b>22</b>, in the rotational motions about the first axis and the secondary axis, and transmit the calculated momentary phases to receiver <b>20</b>. For example, the cyclic motion of magnet <b>22</b> is produced by mounting magnet <b>22</b> and/or a first motor on a camshaft of a second motor. For example, the cyclic motion about the first and second axes is applied to magnet <b>22</b> by mounting magnet <b>22</b> on a shaft, the shaft is free to rotate and move axially and includes a radial pin engaged in a groove in a surrounding sleeve. Optionally, the groove is in the shaft and the pin extends from the sleeve radially into the groove.

0074Processor/controller <b>27</b>, for example a microcontroller/controller, may maintain a permanent desired frequency f, in which motor <b>21</b> operates and/or magnet <b>22</b> rotates. For example, a desired frequency f is inherent to and/or embedded in the hardware of controller <b>27</b> and/or transmitter <b>20</b>. For example, motor device <b>21</b> may be a highly stable motor and/or or a specially designed motor, for example, operating according to a clock <b>28</b> of controller <b>27</b>, or otherwise maintaining a substantially constant frequency. In some embodiments, controller <b>27</b> may switch between various possible frequencies to maintain, for example by maintaining corresponding voltage levels provided to motor <b>21</b>, in a closed feedback loop with the transmitter's magnetometer <b>25</b> (rotary sensor), causing transmitter <b>20</b> to generate AC field in a desired maintained frequency f. In some embodiments, controller <b>27</b> may include hardware and/or software components to change the frequency f. The maintained frequency f may be communicated to receiver/sensor <b>20</b>, for example by controller <b>27</b>, for example by communication interface <b>29</b>. Communication interface <b>29</b> may include a low-power radio transmitter/receiver, for example a 2.4 GHz transmitter/receiver, and/or a Low-Energy Bluetooth device, a WiFi communication device, a USB cable, or any other suitable communication device.

0075According to some embodiments of the present invention, magnetometer <b>25</b> may be located at a fixed location relative to rotating magnet <b>22</b>. Magnetometer <b>25</b> may sense the rotation periods of magnet <b>22</b> and where in the period magnet <b>22</b> is located, e.g. the momentary rotational phase ϕ(t) of magnet <b>22</b>. As indicated in more detail herein, the rotational phase of magnet <b>22</b> may include one or two rotation phases about corresponding one or two axes. For example, magnetometer <b>25</b> may provide an estimation of the phase of magnet <b>22</b>, for example by principle component analysis (PCA) of magnetic samples collected over many rotation periods, for example to extract the axes of an ellipse drawn in a local coordinate system centered at transmitter <b>20</b> by rotating magnet <b>22</b>, or any other suitable method for detecting the phase of magnet <b>22</b>, for example, by fitting an ellipse to samples collected over many periods of the rotating magnet by means of optimization. According to some embodiments of the present invention, magnetometer <b>25</b> is placed at and/or on the rotation axis of the rotating magnet. Due to symmetry, the sensed magnetic field forms an approximate circle or ellipse at the location of magnetometer <b>25</b> while the magnet is rotating. The formed ellipse/circle may be identified, for example by server <b>10</b>/microcontroller <b>32</b>. For example, an ellipse/circle may be fitted to the periodic curve shape of the sensed magnetic field, for example by host server <b>10</b>/microprocessor <b>32</b>. For example, server <b>10</b>/microprocessor <b>32</b> may approximate the periodic curve shape of the sensed magnetic field to a circle and/or compute the momentary phase state of the generated magnetic field within this circle.

0076The rotation frequency of the magnet <b>22</b> may be significantly lower relative to the sampling rate of magnetometer <b>25</b>, e.g. a sampling rate in the range of about 100 Hz-1000 Hz, for example so that the rotation phase of magnet <b>22</b> can be estimated more accurately. Therefore, in some embodiments of the present invention, the rotation frequency of magnet <b>22</b> is much lower than the sampling rate of magnetometer <b>25</b>, for example an order of magnitude lower, for example up to about 10 Hz-100 Hz, according to the sampling rate of magnetometer <b>25</b>. Accordingly, processor/controller <b>27</b> may calculate the rotation phase of magnet <b>22</b> and/or communicate the calculated phase to receiver server <b>10</b>, for example by interface <b>29</b>. Magnetometer <b>25</b> may, in some embodiments, be included in a sensor bundle, for example an IMU chip.

0077According to some embodiments of the present disclosure, unlike traditional magnetic/electromagnetic field transmitter units, transmitter <b>20</b> may generate the magnetic field without using electric current to induce magnetic field. Transmitter <b>20</b> utilizes the already existing field generated by permanent magnet <b>22</b>. Therefore, the power consumption of transmitter <b>20</b> is much lower compared to traditional transmitter units, the lower consumption allows it to operate, for example, tens of hours on a few standard batteries. Thus, for example, power source <b>24</b> that may provide power to transmitter <b>10</b> may be a low-power source such as disposable and/or rechargeable batteries and/or any other suitable low-power source. Rotating the magnet either using a standard DC motor or by weak AC fields produced by coils at the proximity of the magnet, which apply torque on the magnet and cause it to rotate, consumes much less power than generating the same AC field using a standard EM transmitter.

0078Reference is now made to <figref idref="DRAWINGS">FIG. 3</figref>, which is a schematic flowchart illustrating a method <b>300</b> for tracking by digital magnetometers according to some embodiments of the present disclosure. As indicated in block <b>310</b>, server <b>10</b> may receive from generator/transmitter <b>20</b> data about a momentary phase of a generated alternating magnetic field, for example a momentary rotation phase of permanent magnet <b>22</b>, for example along with a corresponding clock reading of clock <b>28</b>. For example, server <b>10</b> may receive the phase data from generator/transmitter <b>20</b> in predetermined periods and/or each time magnetometer <b>25</b> detects a phase of the generated alternating magnetic field. Additionally, server <b>10</b> may receive and/or extract the amplitude and/or of the generated magnetic field at the source, i.e. at transmitter <b>20</b>, for example from magnetometer <b>25</b> and/or by pre-defined calibration data stored in server <b>10</b>.

0079As indicated in block <b>320</b>, server <b>10</b> may receive a sensed value of local magnetic field, sensed by at least one of sensors <b>31</b> along flexible tube <b>36</b> that senses the magnetic field generated by generator/transmitter <b>20</b>. Since sensor <b>31</b> senses the generated magnetic field in its local coordinate system, the magnetic field reading is rotated according to its orientation with respect to generator/transmitter <b>20</b>, yielding, for example, the following magnetic field measurement by sensor <b>31</b>:

0000<br /><i>M</i>_RX(<i>t</i>)=<i>R</i>^t(<i>t</i>)<i>M</i>(<i>t</i>)+<i>M</i>₀

0000Where R is a 3×3 matrix, representing the orientation of sensor <b>31</b> in coordinates of generator/transmitter <b>20</b>, M₀is a sensor bias of sensor <b>31</b>, and M(t) is the generated magnetic field, for example plus environmental magnetic field at the location of sensor <b>31</b>, in coordinates of the generator/transmitter <b>20</b>.

0080In case of a single generator/transmitter <b>20</b> included in system <b>100</b>, in some embodiments of the present invention, the local magnetic field at the location of one of sensors <b>31</b> can be expressed as the superposition of two AC magnetic fields of frequency f and orthogonal phases and generated by two separate virtual coils x and y of transmitter <b>20</b>:

0000<br /><i>M</i>(<i>t</i>)=<i>B</i>₀<i>+B</i>_x(<i>{right arrow over (r)}</i>(<i>t</i>))cos(ϕ(<i>t</i>))+<i>B</i>_y(<i>{right arrow over (r)}</i>(<i>t</i>))sin(ϕ(<i>t</i>))

0000Where B₀is environmental magnetic field (e.g. Earth's magnetic field), B_x, B_yare the magnetic fields due to the virtual coils of generator/transmitter <b>20</b>, {right arrow over (r)}(t) is the position at time t of sensor <b>31</b> and ϕ(t) is the sensed phase of generator/transmitter <b>20</b> at time t (sensed, for example by magnetometer <b>25</b>). Accordingly, the sensed magnetic field M_RX(t) conveys and/or enables extraction, for example by server <b>10</b>, of the position and orientation of sensor <b>31</b>, wherein the phase ϕ(t) is received from generator/transmitter <b>20</b>, and wherein time t is the shared reading of clock <b>28</b> or of an external clock source shared among at least some of the components of system <b>100</b>.

0081As indicated in block <b>330</b>, server <b>10</b> may associate between a sensed momentary phase of magnet <b>22</b>, sensed and/or communicated by magnetometer <b>25</b> and/or generator/transmitter <b>20</b>, and sensed magnetic field values received from sensors <b>31</b>, based on the corresponding shared clock reading of clock <b>28</b> or of an external clock source shared between components of system <b>100</b>, such as server <b>10</b> and sensors <b>31</b> and/or microcontroller <b>32</b>.

0082As indicated in block <b>340</b>, server <b>10</b> may calculate, based on the received sensed magnetic field values and the associated phase of magnet <b>22</b>, position and orientation of sensors <b>31</b> that provided a sensed magnetic field value, for example the 6DOF or 5DOF localization of each of sensors <b>31</b> and/or an overall position, orientation and/or curve of tube <b>36</b>. According to some embodiments, server <b>10</b> may use for the localization calculations accelerometer and/or gyroscope readings of corresponding sensors included in sensors <b>31</b>, in some embodiments of the present disclosure.

0083According to some embodiments of the present disclosure, sensors <b>31</b> are required to have minimal size and thus, for example, may not include gyroscope and/or accelerometer and/or other additional sensors. In such cases, system <b>100</b> may include more than one generators/transmitters <b>20</b>, for example generators/transmitters <b>20</b><i>a </i>and <b>20</b><i>b</i>, for example in order to enable a more accurate calculation of 6DOF or 5DOF localizations.

0084Generators/transmitters <b>20</b><i>a </i>and <b>20</b><i>b </i>may both generate alternating magnetic fields, for example in different frequencies (which are not necessarily orthogonal). Generators/transmitters <b>20</b><i>a </i>and <b>20</b><i>b </i>may be located in a fixed position and orientation relative to each other, and/or the relative position and/or orientation of generators/transmitters <b>20</b><i>a </i>and <b>20</b><i>b </i>may be computed and/or adjusted, for example by manual and/or computerized calibration.

0085Similarly to a single generator/transmitter <b>20</b>, generators/transmitters <b>20</b><i>a </i>and <b>20</b><i>b </i>may generate magnetic fields M₁(t) and M₂(t), respectively, that may be expressed by:

0000<br /><i>M</i>₁(<i>t</i>)=<i>B</i>_x1(<i>{right arrow over (r)}</i>₁(<i>t</i>))cos(ϕ₁(<i>t</i>))+<i>B</i>_y1(<i>{right arrow over (r)}</i>₁(<i>t</i>))sin(ϕ₁(<i>t</i>))

0000<br /><i>M</i>₂(<i>t</i>)=<i>B</i>_x2(<i>{right arrow over (r)}</i>₂(<i>t</i>))cos(ϕ₂(<i>t</i>))+<i>B</i>_y2(<i>{right arrow over (r)}</i>₂(<i>t</i>))sin(ϕ₂(<i>t</i>))

0000Wherein {right arrow over (r)}₁(t), {right arrow over (r)}₂(t) are the position of sensor <b>31</b> in coordinates of transmitter <b>20</b><i>a </i>and <b>20</b><i>b</i>, respectively, ϕ₁(t),ϕ₂(t) are the phases tracked by magnetometers <b>25</b> of transmitter <b>20</b><i>a </i>and <b>20</b><i>b</i>, respectively, B_x1, B_y1are magnetic fields due to virtual coils of transmitter <b>20</b><i>a </i>and B_x2, B_y2are magnetic fields due to virtual coils of transmitter <b>20</b><i>b</i>. Generators/transmitters <b>20</b><i>a </i>and <b>20</b><i>b </i>may share the same clock and/or have synchronized clocks.

0086The magnetic field sensed by sensor <b>31</b> may be expressed by:

0000<br /><i>M</i>_RX^(DUAL)(<i>t</i>)=<i>M</i>₀<i>+R</i>₁^t(<i>t</i>)<i>B</i>₀<i>+R</i>₁^t(<i>t</i>)<i>M</i>₁(<i>t</i>)+<i>R</i>₂^t(<i>t</i>)<i>M</i>₂(<i>t</i>)

0000Where R₁and R₂are 3×3 matrices, representing the orientation of sensor <b>31</b> in coordinates of generator/transmitter <b>20</b><i>a </i>and <b>20</b><i>b</i>, respectively, B₀is the environmental magnetic field (e.g. Earth's magnetic field) and M₀is a sensor bias of sensor <b>31</b>. Since the positions of generators/transmitters <b>20</b><i>a </i>and <b>20</b><i>b </i>are fixed with respect to each other, R₂and/or {right arrow over (r)}₂can be easily derived from R₁and/or {right arrow over (r)}₁, or vice versa, for example, by the simple relation:

0000<br /><i>T</i>₁₂·[<i>R</i>₁<i>;r</i>₁]=[<i>R</i>₂<i>;r</i>₂]

0000where T₁₂is a known rigid transform which converts the coordinates of transmitter <b>20</b><i>a </i>to the coordinates of transmitter <b>20</b><i>b</i>, or vice versa. Therefore, when system <b>100</b> includes two generators/transmitters <b>20</b><i>a </i>and <b>20</b><i>b</i>, there may be no need for solving corresponding two relative positions and two relative orientations for each sensor <b>31</b>. It may suffice to solve position and orientation relative to a first transmitter, which may be converted to the second transmitter's coordinate system. Hence, server <b>10</b> may calculate the 6DOF position and orientation of sensor <b>31</b> based on the received sensed magnetic field M_RX^(DUAL)and the sensed magnetic field phases and clock readings received from generators/transmitters <b>20</b><i>a </i>and <b>20</b><i>b</i>, for example be a catheter localization algorithm implemented in server <b>10</b>/microcontroller <b>32</b>.

0087It will be appreciated that the solution for the 6DOF localization of sensors <b>31</b> and/or tube <b>36</b> is flexible enough and does not rely on any specific implementation, structure and/or configuration of transmitters <b>20</b>, as long as the momentary generated magnetic field at various locations in space is known. In a general setting, the magnetic field reading by a sensor <b>31</b> can be described as:

0000<br /><i>M</i>_RX(<i>t</i>)=<i>M</i>₀<i>+R</i>^t(<i>t</i>)<i>B</i>₀<i>+R</i>^t(<i>t</i>)<i>M</i>(<i>{right arrow over (r)},t</i>)

0000where M({right arrow over (r)}, t) is the known generated magnetic field in coordinates of the generator transmitter <b>20</b> at point {right arrow over (r)} and time t. For example, M({right arrow over (r)}, t) can be modeled as the superposition of general sinusoidal electromagnetic coil fields with different frequencies, for example:

0000<maths id="MATH-US-00001" num="00001"><math overflow="scroll"><mrow><mrow><mi>M</mi><mo>⁡</mo><mrow><mo>(</mo><mrow><mover><mi>r</mi><mo>→</mo></mover><mo>,</mo><mi>j</mi></mrow><mo>)</mo></mrow></mrow><mo>=</mo><mrow><munder><mo>∑</mo><mi>i</mi></munder><mo>⁢</mo><mrow><mrow><msub><mi>B</mi><mi>i</mi></msub><mo>⁡</mo><mrow><mo>(</mo><mover><mi>r</mi><mo>→</mo></mover><mo>)</mo></mrow></mrow><mo>⁢</mo><mi>sin</mi><mo>⁢</mo><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle><mo>⁢</mo><mrow><mo>(</mo><mrow><mn>2</mn><mo>⁢</mo><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle><mo>⁢</mo><mi>π</mi><mo>⁢</mo><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle><mo>⁢</mo><msub><mi>f</mi><mi>i</mi></msub><mo>⁢</mo><mi>t</mi></mrow><mo>)</mo></mrow></mrow></mrow></mrow></math></maths><img file="US2022175468A1_D0001.tif" />

0000where B_i({right arrow over (r)}) is the magnetic field due to the i-th electromagnetic coil and f_iis the operating frequency of the i-th EM coil.

0088In some embodiments of the present disclosure, Kalman filter may be used to track a position and/or orientation state of sensor <b>31</b>. By using Kalman filter algorithm, a faster refresh rate for updating the detected state of sensor <b>31</b> and better overall tracking performance may be obtained. It will be appreciated that in a low-frequency magnetometer-based localization system, in which the sampling rate of sensor <b>31</b> may be, for example, between 100 Hz-1000 Hz, the magnetic field frequency of transmitter <b>20</b> may be constrained to about 10-100 Hz. In this case, a localization algorithm which relies on the decomposition of full periods of the sine waves to field amplitudes, is doomed to have a slow refresh rate and inferior overall tracking performance, which is unacceptable for most medical applications. In some embodiments of the present disclosure, server <b>10</b> solves the problem of slow refresh rate by using a Kalman filter algorithm incorporated in its catheter localization algorithm, which may yield, in some embodiments, a refresh rate of at least 100 Hz, fast enough for most medical applications.

0089Server <b>10</b> may use a mathematical model to describe motion of catheter tube <b>36</b>. In some embodiments, server <b>10</b> may track each sensor <b>31</b> independently. For example, server <b>10</b> may predict the state of sensor <b>31</b> of a next timeframe, for example based on the state in a current timeframe, and/or based on IMU sensor bundle measurements that may be used to correct the prediction. For example, a motion model may use a constant and/or damped velocity for a position and/or orientation of sensor <b>31</b>. For example, server <b>10</b> may use for a Kalman filter algorithm a state vector for sensor <b>31</b>. The state vector may be composed of parameters such as, for example, M₀, B₀, {right arrow over (r)}, Q, {right arrow over ({dot over (r)})}, {right arrow over (ω)}, which may be the sensor bias, environmental magnetic bias, position in coordinates of transmitter <b>20</b>/<b>20</b><i>a</i>, orientation in coordinates of transmitter <b>20</b>/<b>20</b><i>a </i>(expressed as a quaternion), velocity in coordinates of transmitter <b>20</b>/<b>20</b><i>a</i>, angular-velocity in local coordinates (not to be confused with the frequency of the transmitted magnetic field, also sometimes denoted by ω), respectively. M₀, B₀may vary slow enough to be modeled as constant or nearly constant. Deviation from constant velocities, e.g. existence of linear and angular accelerations, and/or deviation from constant environmental magnetic field and sensor bias, can be modeled, for example, as process noise, with corresponding covariance matrices.

0090After defining the state vector and its dynamic model, server <b>10</b> may predict a state vector of sensor <b>31</b> and/or state covariance between consecutive timeframes. Then, the state vector may be corrected according to the prediction to yield a better fit to the newly obtained sensor magnetic field reading. For example, the tracked state vector, whose magnetic measurement is modeled as M_RX^(DUAL)(t), may yield a vector which deviates from the latest sensed magnetic reading only by a small amount of random noise, whose standard deviation can be set according to its typical value, for example from a datasheet of the respective magnetometer.

0091In some embodiments, the motion model used by server <b>10</b> is modular and/or extendable. For example, with the presence of optional accelerometer or gyroscope sensors, for example in sensor <b>31</b>, the Kalman filter can be extended to include an additional state for linear acceleration, {right arrow over ({umlaut over (r)})}. The accelerometer-gyroscope readings can be processed in an IMU-fusion filter to separate between gravitational acceleration and linear acceleration. The computed linear acceleration can then be fed into the Kalman filter as measurements for {right arrow over ({umlaut over (r)})} when correcting the state vector, while the gyroscope readings can serve as measurements for {right arrow over (ω)}. The extra accelerometer-gyroscope readings may significantly reduce the filter's latency and provide even higher-rate, more stable localization.

0092In another configuration, for example instead of separating between “classical” IMU-fusion orientation tracking and magnetometer-based 6DOF tracking, additional IMU data (accelerometer, gyroscope) can be combined with magnetometer readings in a single unified extended Kalman filter. The states of this filter may be: M₀, B₀, {right arrow over (r)}, Q, {right arrow over ({dot over (r)})}, {right arrow over (ω)}, {right arrow over ({umlaut over (r)})} (as explained above). This unified filter may use a constant (or damped) acceleration model for its position. Each sensor <b>31</b> (magnetometer, optional accelerometer &amp; gyroscope) may contribute a measurement for the “update” step, in which all measurements need to be explained using the filter's states. For example, magnetic measurements may be explained with M_RX^(DUAL)using M₀, B₀, {right arrow over (r)}, Q, accelerometer measurements (which are a superposition between gravitational acceleration and linear acceleration) may be expressed by combining Q, {right arrow over ({umlaut over (r)})}, and gyroscope measurements can be explained directly by {right arrow over (ω)}.

0093Using an extended Kalman filter for solving for 6DOF localization of sensors <b>31</b> and/or tube <b>36</b> can be easily generalized for any type of transmitter <b>20</b>, not limited to the transmitter <b>20</b> described with reference to <figref idref="DRAWINGS">FIG. 2</figref>. As long as each magnetic measurement can be explained using the states of the filter, the filter may be fully functional and provide fast 6DOF solutions. This is an excellent property of the extended Kalman filter, where all is needed for high-quality solutions of the states is to be able to model the measurements using those states.

0094For example, in case of using an electromagnetic generator transmitter <b>20</b> that generates magnetic field by electromagnetic coils, M_RX^(DUAL)(t) may be replaced with the more general formula:

0000<br /><i>M</i>_RX(<i>t</i>)=<i>M</i>₀<i>+R</i>^t(<i>t</i>)<i>B</i>₀<i>+R</i>^t(<i>t</i>)<i>M</i>(<i>{right arrow over (r)},t</i>)

0095Where M({right arrow over (r)}, t) depends on the magnetic field generated by the transmitter <b>20</b> being used. This makes the use of an extended Kalman filter for a 6DOF localization solution of sensors <b>31</b>/tube <b>36</b> invariant to the choice of transmitter, which is extremely powerful and flexible for many general purposes.

0096According to some embodiments of the present disclosure, server <b>10</b> may use in its catheter localization algorithm known structural relationships between sensors <b>31</b> to calculate an estimation of the position, orientation and/or curve of tube <b>36</b> as a whole, for example rather than calculating position and/or orientation for each of sensors <b>31</b> separately.

0097Reference is now made to <figref idref="DRAWINGS">FIG. 4</figref>, which is a schematic illustration of catheter <b>30</b>, according to some embodiments of the present disclosure. Catheter <b>30</b> may include a flexible PCB <b>33</b> within and/or placed along catheter tube <b>36</b>. PCB <b>33</b> may be communicationally connected to microcontroller <b>32</b>, for example by the same data bus <b>34</b> that may include few wire lines <b>35</b>, for example two to four wires <b>35</b>. For example, inter-integrated circuit (I2C) is used as a digital connection interface between microcontroller <b>32</b> and sensors <b>31</b> installed along PCB <b>33</b>. In some embodiments, it only requires two wires <b>35</b> for exchange of data between the sensors and microcontroller <b>32</b>, which may be beneficial for a small catheter where wire count should be kept small.

0098In exemplary configurations, flexible PCB <b>33</b> may have eight, five, ten, or any suitable number of sensors <b>31</b> installed thereon, for example all connected to the same I2C bus (for example serial data and serial clock lines). In some embodiments, microcontroller <b>32</b> is connected to flexible PCB <b>33</b> using a 4-wires shielded cable, for example including voltage and/or ground wires. Microcontroller <b>32</b> may provide the voltage and/or ground for digital sensors <b>31</b>, for example additionally to two data lines for the readings of digital measurements by sensors <b>31</b>. Microcontroller <b>32</b> may read sensors <b>31</b>, for example, sequentially and send the sensor readings to server <b>10</b>, for example over wired and/or wireless communication. In a slightly different configuration, five wires <b>35</b> may be used to connect between microcontroller <b>32</b> and flexible PCB <b>33</b> and/or sensors <b>31</b>. For example, additional data line(s) may be added. For example, some of sensors <b>31</b> may use a first data line wire, and other sensors <b>31</b> may use a second data line wire. Accordingly, for example, microcontroller <b>32</b> may sample and/or read some of sensors <b>31</b>, simultaneously, thus, for example, reducing the overall I2C sampling time. For example, in case of two parallel data line wires, the sampling time may be reduced by half.

0099The design of flexible PCB <b>33</b> and/or positioning of sensors <b>31</b> thereon may provide the positions and/or orientations of sensors <b>31</b>, for example, when PCB <b>33</b> is straight. For example, during the manufacturing process, PCB <b>33</b>, may be attached inside and/or along tube <b>36</b>, for example in a manner that determines the positions and/or orientations of sensors <b>31</b>, for example, with respect to tube <b>36</b>. Server <b>10</b> may be calibrated to provide to server <b>10</b> the initial 6DOF orientation and/or position of sensor <b>31</b>, for example 6DOF orientation and/or position of sensor <b>31</b> when tube <b>36</b> is straight. The initial 6DOF orientation and/or position data, along with information about rigidity and/or flexibility limitations of tube <b>36</b>, may be incorporated in the catheter localization algorithm as shape constraints. For example, based on incorporated shape constraints, two neighboring sensors <b>31</b> cannot point to opposite directions.

0100This way, a more sophisticated localization algorithm, which takes shape constraints into account, can enable system <b>100</b> to be both compact and robust. Solving for the 6DOF position and/or orientation of all sensors <b>31</b> while imposing physical shape constraints on catheter tube <b>36</b> full-curve shape may essentially reduce the number of parameters of the motion model and thus, for example, may prevent over-fitting of the measured data. By using the shape constraints, server <b>10</b> may refrain from erroneously calculating a position and/or orientation of sensor <b>31</b> due to a noisy or distorted measurement, because the position and/or orientation solution must comply, for example, with position and/or orientation solutions of neighboring sensors <b>31</b>, for example so they would together describe a smooth, physically plausible catheter tube <b>36</b>.

0101A common challenge in electromagnetic localization systems is to be as accurate as possible in the presence of magnetic distortion. For low frequency systems, the main distorters are objects made of ferromagnetic materials. In the hospital settings, these may be found in the frame of the patient's bed, or as part of the instruments used by physicians (e.g. surgical tools) during a medical procedure. When a localization system does not take magnetic distortion into account, it may be extremely inaccurate (position errors >1 cm) and may be unfit for medical use. Magnetic distorters can be divided to static distorters whose position relative to the system can be fixed, and dynamic distorters which can move between medical procedures and/or during a procedure. Static magnetic distorters are objects that can be fixed relative to the magnetic field generator during the deployment of a localization system, and will stay permanently fixed during the lifetime use of the localization system. In some embodiments of the present disclosure, static distortion can be addressed by a process of magnetic mapping, where the magnetic fields in the sensing radius around transmitter(s) <b>20</b> are no longer assumed to be perfect dipole fields, but are rather “mapped” in an offline process with calibrated sensors <b>31</b> and are later used by the real-time solver in order to solve for accurate 6DOF position and orientation even under the distorted fields. In some embodiments, server <b>10</b> may take into account dynamic distortion by incorporating the distortion in the localization algorithm, for example in order to provide accurate solutions.

0102Different methods can be used to compensate for dynamic magnetic distortions. One method would be to incorporate physical distortion model inside the model of the sensed magnetic field of sensor <b>31</b>. This addition of parameters may yield less robust solutions if each sensor <b>31</b> is solved independently, due to the solver's ability to over-fit the 6DOF and distortion model parameters to the measured sensor <b>31</b> data, even in case of more than one transmitter <b>20</b>. For this reason, the solver should be constrained to parameters that make “mechanical sense”, both in terms of the solved geometry of the sensors <b>31</b> in the catheter tube <b>36</b> and the geometrical properties of the distortion field. Another way of addressing dynamic distortion may include imposing shape constraints on catheter tube <b>36</b> full-curve shape. The 6DOF orientation and position solution calculated by server <b>10</b> may not deviate much from the actual position and orientation of sensor <b>31</b> along the curve of tube <b>36</b>, for example because they are regularized by shape constraints, as described above. While dynamic distortion is usually a local artifact that deforms position and orientation calculations quite differently, the imposed shape constraints will make sure that the multiple sensor <b>31</b> position and/or orientation solutions would still make sense in terms of the catheter tube <b>36</b> fully solved curve. The undesirable effect of distortion will then be naturally reduced just due to the imposed shape constraints.

0103There are several methods for imposing shape constraints in the localization algorithm. One option would be to approximate the catheter's shape as a set of line segments <b>37</b>, with a single sensor <b>31</b> at the end of each segment <b>37</b>. The orientation of each sensor <b>31</b> with respect to its surrounding catheter and its distance to its adjacent receivers are assumed to be fixed and known, for example by calibration of the localization algorithm. Hence, according to some embodiments of the present disclosure, the entire catheter curve can be modeled by a single set of 6DOF that may belong to the one of the sensors <b>31</b>, for example a first sensor <b>31</b> along tube <b>36</b>, for example the closest in the communication path to server <b>10</b> and/or to microcontroller <b>32</b>, and for each sensor <b>31</b> two spherical angles which correspond to the bend of the catheter in segment <b>37</b> between the sensor <b>31</b> and a preceding, for example neighboring, sensor <b>31</b>, and/or an additional angle to represent the internal twist of tube <b>36</b> in the corresponding line segment <b>37</b>. In some embodiments of the present invention, PCB <b>33</b> includes thinner portions <b>33</b><i>a</i>, for example in between sensors <b>31</b>, that are thinner, for example, from portions of PCB <b>33</b> where sensors <b>31</b> are located, for example in order to facilitate enhances flexibility and/or bendability of PCB <b>33</b> in portions <b>33</b><i>a. </i>

0104Reference is now made to <figref idref="DRAWINGS">FIG. 5</figref>, which is a schematic illustration of a catheter <b>30</b><i>a</i>, according to some embodiments of the present disclosure. In some embodiments, flexible PCB <b>33</b> is wrapped in a helix manner on and/or along an inner or outer wall of tube <b>36</b>, as shown in <figref idref="DRAWINGS">FIG. 5</figref>, for example in order to facilitate enhances flexibility and/or bendability of catheter <b>30</b><i>a</i>, e.g. of tube <b>36</b> together with PCB <b>33</b>. As described in more detail herein, for example with reference to <figref idref="DRAWINGS">FIG. 6</figref>, PCB <b>33</b> may carry, for example further to sensors <b>31</b> and/or data bus <b>34</b>, a plurality of dipole magnets.

0105Accordingly, in some embodiments, the number of parameters in the catheter's shape is significantly reduced from 6DOF orientation and position for each sensor <b>31</b> to 6DOF orientation and position for a first sensor <b>31</b> plus three angles for each additional sensor <b>31</b>. In this method, the solved orientation and position of sensors <b>31</b> are less prone to over-fitting, for example due to hard constraints which assume a fixed distance between sensors <b>31</b>, and, for example a fixed orientation of each sensor <b>31</b> with respect to a certain surrounding segment of tube <b>36</b>. An alternative is to use a soft model, in which the position and orientation of sensor <b>31</b> with respect to a previous, for example neighboring, sensor <b>31</b>, are parameterized with regularization terms to penalize the parameters, for example:

0000<br /><i>E</i>_dist=(∥<i>r</i>_i+1<i>−r</i>_i<i>∥−D</i>_i^(cal))²

0000Where: r_i, r_i+1—positions of two sequential sensors <b>31</b>, respectively, and D_i^(cal)—the calibrated distances between the two sequential sensors <b>31</b>. Alternatively, an inequality can be used to constrain the solved distance to a certain range, e.g.: 0.9D_i^(cal)≤∥r_i+1−r_i∥≤1.1D_i^(cal). Such a model, which takes the parameters of sensors <b>31</b> into account, can be formalized in a single Extended Kalman Filter.

0106Another possible method is to solve orientation and/or position for sensor <b>31</b>, for example with an independent solver, may include fitting of a mechanical model to the curve of catheter tube <b>36</b> in segments <b>37</b> between sensors <b>31</b>, and then force an individual sensor <b>31</b> to lie as close as possible to its relevant position and orientation along the curve of tube <b>36</b>. This could be accomplished, for example, by fitting a low degree polynomial between solved positions of sensors <b>31</b>, and then use the model's positions of sensors <b>31</b> as (noisy) position measurements to the independent solvers. Another more general way to achieve this is by describing the curve of tube <b>36</b> as a general curve with some energy function, which may encode the catheter's shape constraints (for example, position and orientation smoothness constraints, distance along the curve between sequential sensors etc.). The curve of tube <b>36</b> can then be fitted to the noisy or distorted measurements of sensors <b>31</b> by means of non-linear optimization, minimizing errors of sensors <b>31</b> and the energy function of the curve of tube <b>36</b>, simultaneously. The method of alternating between individual sensor <b>31</b> localization computations and full-curve fitting computations may be beneficial, because it may allow the computations to be executed in parallel. Instead of solving the full-curve shape of tube <b>36</b> as a whole inside a potentially gigantic Extended Kalman filter, the task may be broken into smaller subtasks, such as solving localization of each sensor <b>31</b> individually, and the sub-results may then be glued together in the form of the final catheter's curve fitting.

0107In some embodiments, it is further possible to reduce the system's number of degrees of freedom by assuming that the environmental magnetic field (e.g. Earth's magnetic field) is uniform along the curve of the catheter. The solved environmental magnetic field is denoted above by B₀and is solved for each sensor of the catheter independently (in transmitter's coordinate system). By assuming that the environmental magnetic field is uniform along the catheter, B₀can be jointly solved for all sensors of the catheter, thus reducing the degrees of freedom of the system and decreasing the risk of over-fitting. Intuitively, sharing B₀between sensors imposes constraints on the relative orientations between sensors (which together with full catheter shape-constraints, also imposes constraints on the relative positions of the sensors). Assuming that B₀is uniform along the entire catheter might not be correct in cases where magnetic distortion is present; in these cases the environmental magnetic field deforms and may vary slowly in space, and in particular along the catheter curve. In this case, a softer assumption may be utilized, assuming that B₀is almost constant between neighboring sensors. This soft assumption can be expressed as an energy function and minimized in least squares sense (as part of the full catheter solver optimization): E_env=Σ_i∥B₀ⁱ−B₀ⁱ⁺¹∥², it requires the solved environmental magnetic fields of neighboring sensors (B₀ⁱ, B₀ⁱ⁺¹) to be similar to each other. In all cases mentioned above, the solved B₀are no longer independent per-sensor, but rather tied together in order to pose some constraints on the in-between orientation of the sensors along the catheter.

0108In another embodiment, instead of just using the natural environmental magnetic field (e.g. Earth's) for imposing constraints on the solved 6DOF of the sensors, artificial constant magnetic fields can be created by incorporating small magnets along the catheter's curve. With the magnets placed at known positions and directions, B₀can be fully predicted for any given configuration of the full catheter curve. B₀may also depend on the relative positions and orientations of the sensors (which by shape smoothness constraints also uniquely define the relative positions and orientations of the incorporated magnets), since each such different configuration can potentially cast other DC magnetic fields (e.g. magnetic fields with substantially zero frequency) on each sensor along the curve by the differently positioned and oriented incorporated small magnets. By knowing the exact position and orientation of each incorporated magnet for each full curve configuration, B₀of each sensor can be predicted so that system's number of degrees of freedom may further decrease.

0109Reference is now made to <figref idref="DRAWINGS">FIG. 6</figref>, which is a schematic illustration of a catheter <b>30</b><i>b</i>, according to some embodiments of the present disclosure. Catheter <b>30</b><i>a </i>may include a plurality of dipole magnets <b>38</b> which are positioned between the sensors, for example in equal distances. For example, dipole magnets <b>38</b> are oriented so that two magnets <b>38</b> located at two sides of a sensor <b>31</b> have opposite dipole directions, when tube <b>36</b> is in a straight state. When catheter tube <b>36</b> is straight, each sensor may sense the superposition of perfectly aligned positive and negative dipole fields so the contribution of two magnets located at two sides of sensor <b>31</b> may be canceled, and thus, for example, the B₀sensed by sensor <b>31</b> may substantially include only Earth's magnetic field. When the catheter starts to bend the contribution of two magnets located at two sides of sensor <b>31</b> may grow linearly as C sin(α), wherein α is the angle of bend and C is some known constant depending on the relative positions and strength of magnets <b>38</b>. In this example, it is evident how B₀encodes more information about the relative orientations between neighboring sensors. By incorporating magnets <b>38</b> along the catheter, as in this example, more efficient constraints may be achieved on the relative sensor orientations than in the case of just using Earth's magnetic field, in terms of SNR (by incorporating relatively strong magnets), reliability (the incorporated magnets are much less prone to magnetic distortion) and geometry (posing the magnets in carefully chosen orientations tunes the constraints as desired for a specific application).

0110In some embodiments of the present invention, system <b>100</b> may be used for organ deformation tracking in minimally invasive surgery. For example, a full-curve catheter localization is used in order to track the deformation which is applied to an internal organ by some external means. For example, during a laparoscopic procedure, organs may be manipulated using tools to the extent where it is hard to tell which part of the organ is visible in the live laparoscopic video. For that reason, visual markers are sometimes utilized; at the beginning of the procedure, and before applying any manipulation to the organ, markers are placed on the surface of the organ at known anatomical landmarks. They are then visually tracked throughout the procedure and used as registration fiducials in order to enable some sort of anatomical localization, even though the organ may be highly manipulated and deformed compared to its initial known state.

0111Unfortunately, in some procedures such as lung laparoscopy, where localization is critical for identifying hidden blood vessels, the surface of the lungs does not contain enough visual information for placing anatomical markers (i.e., markers whose positions in the anatomy are well known). Furthermore, due to the lung's highly flexible form, tracking anatomical features on the surface of the lung does not necessarily extend well for the tracking of important anatomical features inside the lung, such as airways and blood-vessels; the surface does not necessarily predicts well the internal state of the lung. Finally, visual markers and optical tracking systems are prone to occlusions, motion blur, three-dimensional from two-dimensional computational problems and other ills which make most optical-based systems unfit for the purpose of highly accurate laparoscopic guidance.

0112The newly invented full-curve flex catheter tracking can address the flexible registration problem quite easily: In a preoperative stage, one or more flex-track catheters are inserted into known airways using a bronchoscope. Each catheter stays stationary relative to anatomy (as described below) and provides full-curve localization for an airway which is close to some region of interest (ROI). All important anatomical features in some ROI can then be displayed in real-time by employing real-time registration between the fully tracked catheter and a preoperative CT scan. During the laparoscopic procedure, the catheter (or multiple catheters) is bent and twisted, but still holds its anatomical position inside some known airway. The catheter (or multiple catheters) can then serve as a skeleton for the lung, which is fully tracked in real-time, and can provide for a smooth, real-time flexible registration between important anatomical features taken from preoperative CT and the real-time deformed lung. By placing an additional sensor on the laparoscopic camera, those anatomical features can be displayed as an overlay on the live laparoscopic video, thus provide guidance for laparoscopic procedures in the lungs, which is fully real-time and flexible by its nature.

0113In order for the catheter to hold still relative to the anatomy, specifically in organs containing tubes (blood vessels or airways), it should be attached to the anatomical tube. Attachment should be made at the distal allowing the catheter to track organ from the distal point of the catheter and allowing the organ to stretch or shrink freely. Attachment can be achieved using a balloon or hooks, or by friction with the tissue. In order for the catheter to comply with anatomy without deforming it the catheter needs to be highly flexible. Flexibility is achieved by using flexible plastic tubing in the construction of the catheter shaft. It is also important to reduce the rigidity of the flexible PCB. The rigidity of the flexible PCB material is derived from the polyimide stiffness, the number of PCB layers and amount of copper used. The increase in flexibility can be achieved by PCB geometrical design, for example by reducing the width of PCB <b>33</b> between sensors <b>31</b>, and/or routing the conductors in tortuous way and cutting PCB <b>33</b> parallel to the tortuous path to reduce rotational rigidity.

0114In some embodiments of the present invention, system <b>100</b> may be used for electromagnetic navigation bronchoscopy (ENB). A full-curve real-time localized catheter has great advantages in terms of registration accuracies within an ENB procedure. Instead of relying on past samples of the catheter's tip alone, which are very “noisy” due to breathing and heart movement, the full catheter is always visible in the system and can be used as a whole for registration between the coordinates of transmitter <b>20</b> and the airways map. The catheter's very specific bend and shape inside the airways may teach the system about the most probable location of the catheter, as a full curve, inside the airways. Its shape can be matched to the map and be used as a unique signature for its anatomical location inside the airways. For initial registration, the full-curve localization provides many more samples during an unsupervised survey in the lungs compared to just the catheter's tip—full paths may be drawn in coordinates of transmitter <b>20</b> and can be matched to the map in an unsupervised fashion, thus improving the registration's stability and accuracy. For adaptive registration, the fully localized catheter's curve can be matched into airways inside some region of interest (ROI) until the most probable airway is found. This accommodates better for breathing and changes in body posture; the full-curve localization is immediate, unlike history-based approaches in which the accumulated samples inside the time window may undergo different deformation over time (for example, if they were taken during different phases of breathing). Another form of adaptive registration is also possible, where the full-curve localization can be used as a skeletonization of the lungs and serve as the basic ingredient for a flexible deformable lung model. By analyzing the full curve of the catheter one may understand how certain major airways, through which the catheter passes, are deformed, then conclude how surrounding areas are deformed by using some extrapolation model.

0115Furthermore, catheter steering may become easier: it's not uncommon for a physician to experience difficulties while trying to perform a sharp turn with a catheter inside the lungs. The physician would then try over and over again to pull, rotate and push the catheter based on the single-sensor feedback which they receive from the system. With a full-curve localization the physician can see the full bend of the catheter and have a better understanding of how the applied forces translate into distal catheter movement under the stress of the surrounding tissues. Based on this much more informative feedback, he can then generate more precise steering gestures which would translate into the exact desired distal motion with much less trial and error.

0116In addition, full-curve localization is much easier to register with other modalities such as fluoroscopy. During fluoroscopy the full length of the catheter is visible in the X-ray image due to the radio-opacity of the catheter. In traditional EM localization systems only the tip is visible. In such situation, it would be difficult for a physician to match between the fluoroscopic image and the image displayed by the localization system. With full catheter localization both the catheter's full length is visible both in the fluoroscopic image as well as the magnetic localization system, which makes it much easier for a physician to match between the different modalities.

0117In some embodiments of the present disclosure, system <b>100</b> may be used for electromagnetic guided colonoscopy where full catheter localization proves to be beneficial.

0118It will be appreciated that some embodiments of the present invention are applicable to any elongated flexible body and not only to a catheter, with the required changes.

0119Some embodiments of the present disclosure may include a system, a method, and/or a computer program product. The computer program product may include a tangible non-transitory computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present disclosure. Computer readable program instructions for carrying out operations of the present disclosure may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including any object-oriented programming language and/or conventional procedural programming languages.

0120In the context of some embodiments of the present disclosure, by way of example and without limiting, terms such as ‘operating’ or ‘executing’ imply also capabilities, such as ‘operable’ or ‘executable’, respectively.

0121Conjugated terms such as, by way of example, ‘a thing property’ implies a property of the thing, unless otherwise clearly evident from the context thereof.

0122The terms ‘processor’ or ‘computer’, or system thereof, are used herein as ordinary context of the art, such as a general purpose processor, or a portable device such as a smart phone or a tablet computer, or a micro-processor, or a RISC processor, or a DSP, possibly comprising additional elements such as memory or communication ports. Optionally or additionally, the terms ‘processor’ or ‘computer’ or derivatives thereof denote an apparatus that is capable of carrying out a provided or an incorporated program and/or is capable of controlling and/or accessing data storage apparatus and/or other apparatus such as input and output ports. The terms ‘processor’ or ‘computer’ denote also a plurality of processors or computers connected, and/or linked and/or otherwise communicating, possibly sharing one or more other resources such as a memory.

0123The terms ‘software’, ‘program’, ‘software procedure’ or ‘procedure’ or ‘software code’ or ‘code’ or ‘application’ may be used interchangeably according to the context thereof, and denote one or more instructions or directives or electronic circuitry for performing a sequence of operations that generally represent an algorithm and/or other process or method. The program is stored in or on a medium such as RAM, ROM, or disk, or embedded in a circuitry accessible and executable by an apparatus such as a processor or other circuitry. The processor and program may constitute the same apparatus, at least partially, such as an array of electronic gates, such as FPGA or ASIC, designed to perform a programmed sequence of operations, optionally comprising or linked with a processor or other circuitry.

0124The term ‘configuring’ and/or ‘adapting’ for an objective, or a variation thereof, implies using at least a software and/or electronic circuit and/or auxiliary apparatus designed and/or implemented and/or operable or operative to achieve the objective.

0125A device storing and/or comprising a program and/or data constitutes an article of manufacture. Unless otherwise specified, the program and/or data are stored in or on a non-transitory medium.

0126In case electrical or electronic equipment is disclosed it is assumed that an appropriate power supply is used for the operation thereof.

0127The flowchart and block diagrams illustrate architecture, functionality or an operation of possible implementations of systems, methods and computer program products according to various embodiments of the present disclosed subject matter. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of program code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, illustrated or described operations may occur in a different order or in combination or as concurrent operations instead of sequential operations to achieve the same or equivalent effect.

0128The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprising”, “including” and/or “having” and other conjugations of these terms, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

0129The terminology used herein should not be understood as limiting, unless otherwise specified, and is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosed subject matter. While certain embodiments of the disclosed subject matter have been illustrated and described, it will be clear that the disclosure is not limited to the embodiments described herein. Numerous modifications, changes, variations, substitutions and equivalents are not precluded.