Abstract:
Catheterization employing a cable extending from the catheter to a fixed point of attachment is performed by providing a sensor to detect rotation of the catheter about its longitudinal axis, the rotation causing the cable to form a twist. The cable extends through a cable arranger that operates to remove the twist. A controller receives signals from the sensor and generates control signals to actuate the cable arranger responsively to the signals from the sensor.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to medical devices. More particularly, this invention relates to placement and operation of probes within the body of a subject. 
         [0003]    2. Description of the Related Art 
         [0004]    When a physician manipulates a catheter during a medical procedure, the catheter may become twisted or tangled. Several methods and systems have been proposed in order to detect or avoid such situations. For example, U.S. Pat. No. 5,921,978, whose disclosure is incorporated herein by reference, describes a catheter that includes fluoroscopic marker components. Some of the disclosed catheter configurations are used for providing visual information to the physician regarding the direction and degree of twist of the catheter distal end. 
         [0005]    U.S. Pat. No. 5,352,197, whose disclosure is incorporated herein by reference, describes a turn limiter for a catheter with a twistable tip. The catheter has a flexible wall for use in complex twisting anatomy, and contains a torque wire or a torquable guide wire lumen. The torque wire or torquable guide wire lumen extends through the length of the catheter and is attached to the catheter at or near the distal end thereof. The proximal end of the torque wire protrudes from the proximal end of the catheter and is attached to a turn limiter. The turn limiter allows limited rotation of the proximal end of the torque wire or torquable guide wire lumen without axial dislocation. 
         [0006]    U.S. Patent Application Publication No. 2012/0035467, commonly assigned herewith and herein incorporated by reference, describes a catheter entanglement limiter. An operator of an elongated probe manipulates the proximal end of the probe so as to move the distal end within a body of a patient, automatically measuring a cumulative angle of rotation that is applied by the operator to the proximal end. An indication of the cumulative angle of rotation is presented to the operator. 
       SUMMARY OF THE INVENTION 
       [0007]    There is provided according to embodiments of the invention a catheter adapted for insertion into a living subject, the catheter having a longitudinal axis, a cable having one end attached to the catheter and another end to a fixed point, a sensor for detecting rotation of the catheter about the longitudinal axis, the rotation causing a portion of the cable to form a twist, a cable arranger for removing the twist from the portion of the cable, and a controller receiving signals from the sensor and operative for generating control signals to actuate the cable arranger responsively to the signals of the sensor. 
         [0008]    According to an aspect of the apparatus, the sensor is a magnetic field sensor. 
         [0009]    According to another aspect of the apparatus, the sensor is an accelerometer adapted to measure tangential acceleration of the catheter about the longitudinal axis. 
         [0010]    According to another aspect of the apparatus, the sensor is a rotary torque transducer. 
         [0011]    According to one aspect of the apparatus, the cable arranger includes a shaft holding a segment of the cable, and a drive motor for rotating the shaft. 
         [0012]    According to a further aspect of the apparatus, the shaft has a lumen, the cable passing through the lumen and is in contact with the shaft for rotation therewith. 
         [0013]    An additional aspect of the apparatus includes a gear train linked to the drive motor and the shaft. 
         [0014]    According to another aspect of the apparatus, the gear train includes a drive gear attached to the drive motor, two linking gears meshing with the drive gear, and a shaft gear meshing with the two linking gears. The shaft gear is concentric with the shaft and has a radial slot for insertion and removal of the cable therethrough. The cable is wound about the shaft. 
         [0015]    According to still another aspect of the apparatus, spiral grooves are formed in the shaft for carrying the cable therein. 
         [0016]    One aspect of the apparatus includes a drive gear attached to the drive motor that meshes with gear teeth formed on the shaft. The cable is urged into contact with grooves in the drive gear when the spiral grooves and the grooves of the drive gear are in alignment. 
         [0017]    There is further provided according to embodiments of the invention a method, which is carried out by inserting a catheter into a living subject, connecting a cable between the catheter and a fixed point of attachment, forming a twist in a portion of the cable by rotating the catheter about its longitudinal axis, automatically detecting rotation of the catheter about the longitudinal axis, and responsively to detecting rotation removing the twist from the portion of the cable. 
         [0018]    According to a further aspect of the method, detecting rotation is performed using a magnetic field sensor. 
         [0019]    According to one aspect of the method, detecting rotation is performed using an accelerometer adapted to measure tangential acceleration of the catheter about the longitudinal axis. 
         [0020]    According to another aspect of the method, detecting rotation is performed using a torque transducer. 
         [0021]    According to an additional aspect of the method, removing the twist is performed by operating a cable arranger including a shaft holding a segment of the cable, and a drive motor for rotating the shaft, and imparting a compensatory rotation about the longitudinal axis of the cable. 
         [0022]    Yet another aspect of the method includes providing a cable arranger having a drive gear, the drive gear having grooves formed therein. The drive gear is attached to a drive motor and a shaft having spiral grooves formed therein for carrying the cable, the drive gear meshing with gear teeth formed on the shaft, wherein the cable is urged into contact with the grooves of the drive gear when the spiral grooves of the shaft and the grooves of the drive gear are in alignment, wherein removing the twist comprises rotating the shaft to displace the cable through the cable arranger. 
         [0023]    A further aspect of the method includes providing a radial slot in the drive gear for ingress and egress of the cable therethrough. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0024]    For a better understanding of the present invention, reference is made to the detailed description of the invention, by way of example, which is to be read in conjunction with the following drawings, wherein like elements are given like reference numerals, and wherein: 
           [0025]      FIG. 1  is a schematic illustration of a cable arranger for use with a position tracking system, in accordance with an embodiment of the present invention; 
           [0026]      FIG. 2  is a series of images showing a progression of twists of a cable that are compensated using the embodiment of  FIG. 1 , in accordance with an embodiment of the invention; 
           [0027]      FIG. 3  is a perspective top view of a cable arranger in accordance with an embodiment of the invention; 
           [0028]      FIG. 4  is an exploded view in slight perspective of the cable arranger shown in  FIG. 3 , in accordance with an embodiment of the invention; 
           [0029]      FIG. 5  is a perspective view of the cable arranger shown in  FIG. 3  with the housing removed, in accordance with an embodiment of the invention; 
           [0030]      FIG. 6  is an elevation of a gear shown in  FIG. 4 , in accordance with an embodiment of the invention; 
           [0031]      FIG. 7  is a schematic diagram of a cable arranger, in accordance with an alternate embodiment of the invention; 
           [0032]      FIG. 8  is a schematic diagram of the cable arranger shown in  FIG. 7  with the housings removed; 
           [0033]      FIG. 9  is a schematic diagram of a control arrangement for a cable arranger, which is constructed and operative in accordance with an embodiment of the invention; and 
           [0034]      FIG. 10  is a schematic cross sectional view of a rotary torque transducer in accordance with an alternate embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0035]    In the following description, numerous specific details are set forth in order to provide a thorough understanding of the various principles of the present invention. It will be apparent to one skilled in the art, however, that not all these details are necessarily always needed for practicing the present invention. 
         [0036]    Turning now to the drawings, Reference is initially made to  FIG. 1 , which is a schematic, pictorial illustration of a position tracking system  10 , in accordance with an embodiment of the present invention. Typically, a catheter  12  that can be navigated with a handle  13  is used for diagnostic or therapeutic treatment performed by medical practitioner  16 , such as mapping electrical potentials in the heart or performing ablation of heart tissue. The catheter  12  or other intrabody device may alternatively be used for other purposes, by itself or in conjunction with other treatment devices. The catheter  12  enters a subject  14  at an insertion point  30 , which in this example is a femoral vessel. Processors and circuitry related to the medical procedure are found in a control unit  18 . The system  10  typically includes a subsystem for tracking the position of the catheter  12  within the body of the subject  14 . One tracking sub-system of the system  10  is known as an active current localization ACL subsystem  36 , in which a plurality of body-surface electrodes are placed in galvanic contact with a body-surface, e.g., the skin of the subject  14 , and receive body surface currents therefrom. Additionally or alternatively, the system  10  may include a magnetic tracking sub-system  38  comprising magnetic sensors and field generators for tracking the catheter  12 . Processors for the subsystems  36 ,  38  are typically located in the control unit  18 . Peripheral elements of the position tracking sub-systems  36 ,  38  are generally connected to the control unit  18  by a cable  32 . Operational information relating to the catheter  12  and the system  10  may be displayed on a monitor  34 . One system that embodies the above-described features of the system  10  is the CARTO® 3 System, available from Biosense Webster, Inc., 3333 Diamond Canyon Road, Diamond Bar, Calif. 91765. This system may be modified by those skilled in the art to embody the principles of the invention described herein. 
         [0037]    A cable arranger  40  is operative to prevent undesired twisting and entanglement of a segment  15  of cable near the handle  13  of the catheter  12 , where the twisted cable would interfere with the practitioner  16 , The cable passes from the catheter  12  through the cable arranger  40  to a fixed point of attachment, such as the control unit  18 . The cable may include or be accompanied by one or more hydraulic lines. 
         [0038]    Reference is now made to  FIG. 2 , which is a series of images showing a progression of twists of a cable  44  having one end attached to a catheter and another end attached to a fixed point, e.g., the control unit  18  ( FIG. 1 ). Such twisting can be caused by rotation of the catheter about its longitudinal axis during a catheterization session in the absence of the cable arranger  40 . In a worst case  46 , the cable  44  becomes a severe encumbrance and can greatly hinder the practitioner  16  in performing the medical procedure. 
         [0039]    Reference is now made to  FIG. 3 , which is a perspective top view of a cable arranger  48 , which is a variant of the cable arranger  40  ( FIG. 1 ) in accordance with an embodiment of the invention. A cover  50  and a base  52  comprise a housing for a drive assembly (not shown in this view). A torsion rod  54  extends outward from the cover  50  and grips a cable  56  passing through the torsion rod  54 . A clamp  58  is provided for affixing the cable arranger  48  to a convenient attachment point to assure mechanical stability. One or more hydraulic lines, e.g., irrigation tubes may be included in the cable  56  or accompany the cable  56  as separate channels to form a bundle of electrical and hydraulic channels. 
         [0040]    The torsion rod  54  comprises two portions joined together at a seam  60 . The two portions can be readily snapped together, allowing the operator to accordingly engage and disengage the cable  56  sideways through a slot  62  formed in the base  52 . 
         [0041]    Reference is now made to  FIG. 4 , which is an exploded view in slight perspective of the cable arranger  48  ( FIG. 3 ). Mounted beneath the base  52  are a motor cover  64 , motor  66  and gear train for rotating the torsion rod  54 . The gear train is a modified planetary arrangement comprising a drive gear  68  that is rotated by a drive shaft  70  of the motor  66 . 
         [0042]    Reference is now made to  FIG. 5 , which is a perspective view of the cable arranger  48  with the housing removed. The gear train is best appreciated in  FIG. 5 . The drive gear  68  meshes with linking gears  72 ,  74 , both of which mesh with a gear  76  that rotates the torsion rod  54  about its longitudinal axis. 
         [0043]    The gear  76  is provided with a slot  82 , which provides lateral egress and ingress to the cable  56  when the slot  82  is aligned with the slot  62  ( FIG. 3 ). When the gear  76  is rotated such that the slot  82  opposes one of the gears  72 ,  74  and is thus unable to mesh with its teeth, the other of the gears  72 ,  74  continues to mesh and enables further rotation of the gear  76  in either direction. 
         [0044]    Reference is now made to  FIG. 6 , which is an elevation of the gear  76 . The slot  82  extends radially from the center outward and interrupts the gear teeth. The slot  82  accommodates the cable  56  ( FIG. 5 ). 
       First Alternate Embodiment 
       [0045]    Reference is now made to  FIG. 7 , which is a schematic diagram of a cable arranger  84 , in accordance with an alternate embodiment of the invention. In this embodiment, a drive motor  86  within a housing  88  is geared to a cable collector  90 , such that actuation of the drive motor  86  causes a shaft in the cable collector  90  to rotate about its longitudinal axis within its housing  92 . 
         [0046]    A cable  94  passes into the housing  92  via a sleeve adaptor  96 , which is fitted loosely about the cable  94  and can rotate about the cable  94  and not grip the cable  94  when the drive motor  86  is actuated. Referring again to  FIG. 1 , in normal operation the cable  94  extends from the catheter  12  through the cable arranger  84  to the control unit  18 . The cable  94  can be inserted or removed through the housing via a slot  97 . 
         [0047]    Reference is now made to  FIG. 8 , which is a schematic diagram of the cable arranger  84  (FIG. f 7 |) with the housings removed. The drive motor  86  is connected to a cylindrical drive gear  98  by a drive shaft  100 . The drive gear  98  meshes with gear teeth formed on the surface of a cable collector  102 , causing the drive gear  98  to contrarotate about its longitudinal axis. Two series of helical grooves  104 ,  106  are formed in the cable collector  102 , one series of grooves having a right-handed and the other a left-handed winding direction. The grooves  104  align with grooves  108  in the drive gear  98 . The cable  94  is taken up in the grooves  104 , and fits into opposing series of grooves  108  as the drive gear  98  rotates and the grooves  104  align with the grooves  108 . The grooves  108  permit take-up of the cable  94  without its being compressed between the drive gear  98  and cable collector  102 . Manipulations of the cable  94  by the operator may cause a left-handed or a right-handed twist to form in a segment  116  of the cable  94 , and the cable collector  102  rotates in one direction or the other as the case may be so as to compensate. When it is necessary to rotate the cable collector  102  in the opposite direction from that shown in  FIG. 8 , the cable  94  is carried in the grooves  106  rather than the grooves  104 . The grooves  106  align with corresponding grooves  110  in the drive gear  98  and perform the same function as the grooves  108 . 
         [0048]    When the drive motor  86  is actuated, rotation of the cable collector  102  rotates the cable  94  within the sleeve adaptor  96  in a direction that tends to counteract twisting motion that it may have been subjected to by rotatory movement of the catheter  12  ( FIG. 1 ) as indicated by an arrow  112 . However, the principal effect produced by the cable collector  102  is displacement of the twist away from the operator (as indicated by arrow  114 ), such that the twisted portion of the cable  94  does not occur near the operator (in segment  116 ), but instead appears beyond the cable collector  102  in segment  118 , far enough removed from the operator so as not encumber him during the medical procedure. 
       Control 
       [0049]    Reference is now made to  FIG. 9 , which is a schematic diagram of a control arrangement for a cable arranger, which is constructed and operative in accordance with any of the embodiments of the invention described herein. A cable arranger  120 , typically located on a portion of a cable  122  proximal to the operator (not shown), acts in response to rotation of the catheter about its longitudinal axis. Rotation is sensed by a sensor  124 , which can be disposed on the shaft of the catheter  122  or near its tip  126 , or in the handle (not shown) of the catheter. 
         [0050]    When a reading of the sensor  124  by a controller  128  indicates that rotation of the catheter is occurring distal to the cable arranger  120  thereby inducing the cable to twist, a drive motor  130  of the cable arranger  120  is actuated by the controller  128 , causing the cable arranger  120  to act on the cable by imparting another rotary motion to the catheter  122  that counteracts the twisting force or displaces the twist away from the operator. 
         [0051]    In the embodiment of  FIG. 9 , the sensor  124  is a magnetic field sensor having three mutually orthogonal coils  132 . In the presence of magnetic fields generated by one or more magnetic field generators  134 . This arrangement has been implemented for location tracking in the above-described CARTO system, and is capable of detecting changes in orientation, position, and rotation of the catheter  122 . 
         [0052]    In another embodiment, the sensor  124  may be replaced by an array of three mutually orthogonal accelerometers mounted at fixed radial distances from the longitudinal axis of the catheter  122 . The angular velocity of the catheter  122  and its angular displacement from a nominal position can be derived from the tangential accelerations measured by the accelerometers. 
         [0053]    In yet another embodiment, the sensor  124  may be replaced by a strain gauge, wherein the torsion rod  54  ( FIG. 5 ) is embodied as a rotary torque transducer applied to the cable. Reference is now made to  FIG. 10 , which is a schematic cross sectional of a view of a rotary torque transducer  136  in accordance with an alternate embodiment of the invention. A cable  138  passing through the torque transducer  136  is held against a resilient upper segment  140  of a torsion rod  142 . Two preloaded strain gauges  144  are incorporated in the upper segment  140 , enabling measurement of rotational torque in positive and negative directions. 
         [0054]    A lower segment  146  The cable  138  is gripped against the upper segment  140  and lower segment  146  by clasps  148 ,  150 , respectively. The strain gauges  144  are in electrical contact with a slotted gear  152  via fixed electrical contacts  154 . The opposite face of the gear  152  has a series of moving electrical contacts  156  of stationary electrical brushes  158  that are mounted on a base  160 . 
         [0055]    In yet another embodiment, the sensor  124  may be replaced by incorporating a torque encoder in the cable arranger  40  ( FIG. 1 ). A suitable torque encoder is taught in commonly assigned, copending application Ser. No. 14/139,974, filed Dec. 24, 2013, which is herein incorporated by reference. 
         [0056]    It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.