Abstract:
An patch and sensor assembly for use in an EP mapping system has two portions: a reusable portion and a disposable portion. The reusable portion houses the biosensors used in magnetic based location and mapping systems and the electrical lead necessary to communicate between the biosensor and the mapping system. The reusable portion may also contain a portion of the electrode necessary to receive electrical signals from the body of the patient. The disposable portion of the patch and sensor assembly contains an adhesive covered flexible patch having at least a portion of the electrode used to receive electrical signals form the body of the patient and may contain the electrical lead necessary to communicate such an electrical signal to the mapping system. The disposable portion contains a receptacle adapted to receive and mechanically secure the reusable portion to the disposable portion of the assembly. Such a patch and sensor assembly is useful in hybrid magnetic and impedance based location and mapping systems such as those used in electrophysiology.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of commonly owned U.S. patent application Ser. No. 12/144,826 filed Jun. 24, 2008. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to mechanisms for the attaching a reusable cable and housing containing a biosensor for magnetic field based localization to a conductive and adhesive patch assembly having at an electrode used for electrical and mechanical contact with the body surface of a patient. More particularly, the invention relates to a patch and cable attachment mechanism optimized for use in an electrophysiology mapping and ablation system using both biosensors and electrodes for magnetic and impedance or current based localization and mapping of medical devices in the human body. 
       BACKGROUND OF THE INVENTION 
       [0003]    Many abnormal medical conditions in humans and other mammals have been associated with disease and other aberrations along the lining or walls that define several different body spaces. In order to treat such abnormal conditions of the body spaces, medical device technologies adapted for delivering various therapies to the body spaces using the least invasive means possible. 
         [0004]    As used herein, the term “body space,” including derivatives thereof, is intended to mean any cavity within the body which is defined at least in part by a tissue wall. For example, the cardiac chambers, the uterus, the regions of the gastrointestinal tract, and the arterial or venous vessels are all considered illustrative examples of body spaces within the intended meaning. 
         [0005]    The term “vessel,” including derivatives thereof, is herein intended to mean any body space which is circumscribed along a length by a tubular tissue wall and which terminates at each of two ends in at least one opening that communicates externally of the body space. For example, the large and small intestines, the vas deferens, the trachea, and the fallopian tubes are all illustrative examples of vessels within the intended meaning. Blood vessels are also herein considered vessels, including regions of the vascular tree between their branch points. More particularly, the pulmonary veins are vessels within the intended meaning, including the region of the pulmonary veins between the branched portions of their ostia along a left ventricle wall, although the wall tissue defining the ostia typically presents uniquely tapered lumenal shapes. 
         [0006]    One means of treating body spaces in a minimally invasive manner is through the use of catheters to reach internal organs and vessels within a body space. Electrode or electrophysiology (EP) catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity. In use, the electrode catheter is inserted into a major vein or artery, e.g., the femoral artery, and then guided into the chamber of the heart that is of concern in order to perform mapping and ablation procedures. It is important to know and be able to map the location of the tip or other portions of such electrode catheters within the vessels or other locations in the body space. 
         [0007]    U.S. Pat. Nos. 5,391,199, 5,443,489, 6,788,967 and 6,690,963 to Ben-Haim, whose disclosures are incorporated herein by reference, describe systems wherein the coordinates of an intrabody probe are determined using one or more field sensors, such as a Hall effect device, coils, or other antennae carried on the probe. Such systems are used for generating three-dimensional location information regarding a medical probe or catheter. Preferably, a sensor coil is placed in the catheter and generates signals in response to externally applied magnetic fields. The magnetic fields are generated by three radiator coils, fixed to an external reference frame in known, mutually spaced locations. The amplitudes of the signals generated in response to each of the radiator coil fields are detected and used to compute the location of the sensor coil. Each radiator coil is preferably driven by driver circuitry to generate a field at a known frequency, distinct from that of other radiator coils, so that the signals generated by the sensor coil may be separated by frequency into components corresponding to the different radiator coils. 
         [0008]    In United States Patent Application No. 2007/0016007 filed by Govari and incorporated herein by reference, a hybrid position sensing system includes a probe adapted to be introduced into a body cavity of a subject. The probe includes a biosensor having a magnetic field transducer and at least one probe electrodes. A control unit is configured to measure position coordinates of the probe using the magnetic field transducer of the biosensor. The control unit also measures an impedance between the at least one probe electrodes and one or more points on a body surface of the subject. Using the measured position coordinates, the control unit calibrates the measured impedance. 
         [0009]    Thus, in such a hybrid magnetic and impedance based systems, a biosensor and electrode must be placed at multiple points on the boy surface of the patient. Because the biosensors and the electrical cabling connecting them to the EP mapping system are relatively expensive, it is ideal that the biosensors and the associated cable be reusable. The portion attached to the skin is preferably disposable, therefore, a disposable patch is necessary for affixing the reusable biosensor and possibly a portion of the electrode to the skin of the patient. 
         [0010]    Existing patches comprises one or more stainless steel studs, foam and a conductive adhesive gel that is in contact with the skin of the patient. The matching patch cable in existing systems primarily comprise one ore more matching stainless steel snaps into which the studs of the patch mate, a biosensor and the associated electrical cable all housed in an epoxy shell. Existing biosensor cable and patch mechanisms are radiopaque, i.e., the stainless steel snaps and studs appear on fluoroscopy. When multiple snaps are used which is often the case in order to provide a secure and non-rotating connection between the patch and the sensor cable, the multiple snaps do not allow the patch to take the shape of the body. Also, the patches are often large and conflict with other patches used on the body for ECG, defibrillators, intra-cardiac echograms, etc. 
         [0011]    Prior art mechanisms do not provide an adequate solution. For example, U.S. Pat. No. 3,606,881, relates to a disposable patch having a metallic terminal with an enlarged head which permits a squeeze activated clip to be secured around the metallic terminal. U.S. Pat. No. 3,829,826 provides a mechanical mechanism for attaching to the standard male metallic snap of the standard ECG patch. U.S. Pat. No. 4,490,005 relates to a patch in which the central stud is a metal coated non-metallic substrate and which permits rotation of the sensor cable while reducing the effect of rotation on the metal to metal connection. U.S. Pat. No. 4,635,642 relates to a disposable pad in which a conductive, preferably, silver coated metallic stud is inserted in order to make electrical conduct with a gel matrix that is in contact with the skin of the patient. 
         [0012]    A similar conductively coated electrically conductive plastic is provided in U.S. Pat. No. 5,499,628 as an eyelet that is press fit into a terminal made of a resilient nonmetallic composition such as polypropylene blended with carbon fiber. 
         [0013]    U.S. Pat. No. 5,615,674 relates to a clamping contact connection for contacting a fetal scalp probe. 
         [0014]    U.S. Pat. No. 5,782,761 relates to a molded electrode one-piece and two-piece constructions for a molded electrode made of a conductive material such as a carbon-filled plastic. 
         [0015]    U.S. Pat. No. 6,650,922 relates to an electrode element made of an electrode made of a biodegradable material that is also electro conductive. 
         [0016]    U.S. Pat. No. 6,780,065 relates to a device for electrical connection of the power lead to an electrode for use on the skin. 
         [0017]    U.S. Pat. No. 7,226,299 relates to a circular electrical connector that engages the socket of a female connector that may include a locking device having resilient prongs. 
         [0018]    Design Pat. 240,166 relates to a medical electrode with a rectangular cube portion. 
         [0019]    U.S. Patent Application Publication No. 2006/0167354 relates to a system for connecting an electrode to a conductive cable. 
         [0020]    U.S. Patent Application Publication No. 2006/0149146 relates to a device having an electrode for contact with the patient and a pressure sensor. 
         [0021]    U.S. Pat. No. 5,978,693 relates to an electrode having a deformation sensor such as a strain gauge. 
         [0022]    It is an object of the present invention to provide a patch that is generally not visible under fluoroscopy. 
         [0023]    It is a further object of the present invention that the patch be capable of being smaller than currently used patches so as to minimize the amount of space used on the skin of the patient and reduce potential conflict with other patches. 
         [0024]    Additionally, it is an object of the present invention to provide a patch and sensor cable that will not rotate as would previous designs utilizing a single snap. 
         [0025]    Furthermore, it is an object of the present invention to have a patch and sensor cable attachment mechanism that is easy to attach. 
         [0026]    Additionally, it is an object of the present invention to have a patch and sensor cable design that could be used for ECG or other instrument systems. 
         [0027]    Finally, it is an object of the present invention to have a patch and sensor cable attachment mechanism that enables repeated reuse of the biosensor and sensor cable without any degradation in performance. 
       SUMMARY OF THE INVENTION 
       [0028]    The present invention generally relates to a patch and sensor assembly for use in an electrophysiology mapping and ablation system. More specifically, the present invention relates to a patch and sensor assembly in which a magnetic-based biosensor is housed in a reusable portion that connects to the mapping and localization system whereas at least a portion of the electrode is in a disposable patch assembly. 
         [0029]    More specifically the present invention discloses a patch and sensor assembly for use in a device mapping system used to map the location of a device within the body of a patient comprising a reusable portion and a disposable portion. The reusable portion includes a magnetic-based biosensor for providing location information about the location of the device within the body of the patient to the device mapping system, a housing adapted to house the biosensor and a first electrical lead for communicating an electrical signal from the biosensor to the device mapping system. The disposable portion comprises an adhesive hydrogel layer for adhering the electrode to the body of the patient, an electrode layer disposed on the adhesive hydrogel layer, a foam layer disposed on a portion of the electrode layer, a second electrical lead for communicating an electrical signal from the electrode layer to the device mapping system and an engagement element adapted to detachably receive at least a portion of the housing of the reusable portion. 
         [0030]    In a preferred embodiment the sensor engagement element adapted to detachably receive at least a portion of the housing of the reusable portion wherein the engagement element comprises a first engagement element for engaging an indentation in the top portion of the housing of the reusable portion and a second engagement element for engaging an indentation in the proximal end of the bottom portion of said housing. 
         [0031]    The electrode layer comprises carbon composite, preferably carbon fibers in polyvinyl chloride (PVC) coated on at least one dimension with a metallic material such as silver chloride. Preferably, an additional layer of silver is disposed on the silver chloride. 
         [0032]    The disposable portion of the patch and sensor assembly further includes a second foam layer disposed on the first foam layer and comprising at least one indentation adapted to receive the first electrical lead. The second electrical lead comprises a plurality of wires having a distal end and a proximal end and the distal ends of the plurality of wires are arrayed in a fan and positioned between the electrode layer and the foam layer. 
         [0033]    The first foam layer is comprised of polyethylene foam with a medical grade acrylic pressure sensitive adhesive on the patient facing side. The first foam layer has an opening for receiving a portion of the sensor engagement element. 
         [0034]    The reusable portion of the patch and sensor assembly further comprises a strain relief element for reducing mechanical strain on the connection between the biosensor and the sensor cable. 
         [0035]    The sensor engagement element may be made of a polycarbonate, preferably Lexan® polycarbonate. 
         [0036]    The disposable portion of the patch and sensor assembly further includes a release liner on which the hydrogel layer is disposed. The release liner is preferably made of polyethylene terephthalate (PET) with a silicone coating on the side facing the hydrogel layer. 
         [0037]    The electrical leads of the disposable patch assembly and the reusable sensor assembly are connected to a device mapping and localization system such as the Carto® system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]      FIG. 1  is a planar view of the top of the patch and sensor cable assembly in accordance with a first embodiment of the present invention. 
           [0039]      FIG. 2  is a partial cross-sectional view of the patch and sensor cable assembly of  FIG. 1  through line A-A. 
           [0040]      FIG. 3  is a perspective view of the strain relief element for use in patch and sensor cable assembly of  FIG. 1 . 
           [0041]      FIG. 4  is a perspective view of a second embodiment of a patch and sensor cable connector in accordance with the present invention. 
           [0042]      FIG. 5  is a planar view of the top of a further embodiment of a patch and sensor cable assembly in accordance with the present invention. 
           [0043]      FIG. 6  is a cross-sectional view of the embodiment of the patch and sensor cable assembly of  FIG. 5 . 
           [0044]      FIG. 7  is a planar view of another embodiment of the disposable portion of a patch and sensor cable assembly in accordance with the present invention. 
           [0045]      FIG. 8  is an exploded view of the embodiment of the disposable portion of the patch and sensor cable assembly of  FIG. 7 . 
           [0046]      FIG. 9  is a cross-sectional view of the embodiment of the disposable portion of the patch and sensor cable assembly of  FIG. 7  through line L-L. 
           [0047]      FIG. 10  is a planar top view of the reusable sensor cable assembly for use in the embodiment of patch assembly of  FIG. 7   
           [0048]      FIG. 11  is a cross-sectional view of the reusable sensor cable assembly through line A-A of  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0049]    Referring to the drawings,  FIG. 1  depicts a planar view of an embodiment of the patch and sensor cable assembly in accordance with the present invention. As shown in  FIG. 1 , the patch and sensor assembly  100  comprises two major components: a patch assembly  110  and a sensor cable assembly  130 . Sensor cable assembly  130  comprises a sensor housing  122  that is adapted to connect to the patch assembly  110  and a sensor cable  124 . In  FIG. 1  the connection between the sensor housing  122  and patch assembly  110  is a snap-fit based on the engagement of ridge  123  of sensor housing  122  and the lip of engagement element  114  of patch assembly  110 . Patch assembly  110  comprises a foam disk  112  having a plurality of indentations  113  adapted to receive the sensor cable  124 . The patch assembly in  FIG. 1  is shown with three such indentations enabling a user to attach the sensor cable assembly in one of three positions even after the disposable patch assembly has been placed on the patient. One or more such indentations  113  may be used with the upper limit constrained by the ability of the remaining engagement element  114  to securely engage the ridge  123  of sensor housing  122 . Engagement element  114  contains indentations that match those in foam disk  112 . The foam used to form foam disk  112  may be any suitable material such as thermofoam, any elastomers like rubber, santoprene, polyurethane etc. and is preferably thermofoam. 
         [0050]      FIG. 2  depicts a partial cross-section of the patch and sensor assembly of  FIG. 1  taken through line A-A. Foam disk  112  rests on a carbon film disk  116  coated with a layer of silver chloride on both sides. Carbon film disk  116  is approximately 0.5 mm in thickness and the layer of silver chloride is approximately 0.1 mm in thickness. Other thicknesses of carbon film disk  116  and silver chloride coating may be used without departing from the spirit of the invention. On the patient facing side of carbon film disk  116  is a hydrogel layer  117 . Hydrogel layer  117  is comprised of a conductive gel medium, which also has adhesive properties to the skin, preferably a hydrogel being a mix of Silver/Silver Chloride with water based compound and is approximately 1 mm mm in thickness. 
         [0051]    Foam disk  112 , carbon film disk  116  and the hydrogel layer  117  generally have approximately the same diameter which should be large enough to provide a secure attachment to the body surface of the patient and is preferably between 4 cm and 16 cm. The only other component of patch assembly  110  is the engagement element  114 . Patch assembly  110  comprises only low-cost components in order to increase the disposability of the patch assembly in this embodiment. 
         [0052]    The other component of the patch and sensor assembly  100  depicted in  FIGS. 1 and 2  is the reusable sensor cable assembly  130 . The reusable sensor cable assembly  130  comprises the aforementioned sensor housing  122 . Sensor housing  122  is a two-piece design in which upper housing portion  122   a  is design to fit together with lower housing portion  122   b.  Lower housing portion  122   b  contains the ridge  123  that engages engagement element  114  of the patch assembly although this ridge could be disposed on the upper housing portion without departing from the spirit of the present invention. Sensor housing  122  is comprised of a polymer such as ABS, nylon, polypropylene or other suitable polymer known in the art and is preferably made from polypropylene. Sensor housing  122  could be comprised of more than two parts without departing from the spirit of the invention. 
         [0053]    Sensor cable assembly  130  further comprises the sensor cable  124  which comprises a conductive ACL cable made of a conductive and flexible material, preferably 28 gauge braided copper wire, three twisted pair conductors for the biosensor has along with two Kevlar fibers for added strength inside a polymeric outer sheath. One wire in sensor cable  124  is welded or bonded using a conductive epoxy to biosensor  126 . 
         [0054]    Sensor cable assembly  130  further comprises active current location (ACL) disk  134  which may be made of a suitably conductive material and is preferably a generally circular carbon disk coated with silver chloride. Gold or platinum may also be used instead of silver chloride for the coating and the carbon disk could be replaced with a polymer such as ABS or polycarbonate with or without carbon fibers embedded therein. ACL cable  136  is attached to ACL sensor  134  using a suitable conductive epoxy, preferably any epoxy preferably embedded silver particles. In use, current flowing through the patient is conducted through the hydrogel layer  117 , carbon film disk  116  to ACL sensor  134  and through ACL cable  136  to the localization and mapping system that uses the ACL information to perform localization and mapping functions in accordance with United States Patent Application No. 2007/0016007 filed by Govari and incorporated herein by reference or other such similar system. 
         [0055]    Sensor cable assembly  130  further comprises biosensor  126  which is a biosensor implemented in accordance with one or more of U.S. Pat. Nos. 5,391,199, 5,443,489, 6,788,967 and 6,690,963 to Ben-Haim, whose disclosures are incorporated herein by reference. Magnetic field based information from biosensor  126  is an electrical current induced by the magnetic field in which the patient is placed and is used in a manner similar to that used in the Carto™ EP mapping systems manufactured and sold by Biosense Webster, Inc. The electrical current from biosensor  126  is conducted through three twisted pair conductors of the sensor cable assembly  130  to biosensor cable which connects to and EP mapping and localization system where the information is used. Biosensor  126  is housed in biosensor housing  138 . Isolation layer  139  is thin piece of plastic material preferably polypropylene, ABS or polycarbonate which isolates the 4KV defibrillation pulse from ACL wire to the biosensor  126 . 
         [0056]    As can be seen from  FIGS. 1 and 2 , it is advantageous to have the biosensor  126 , ACL sensor  114  and the sensor cable  124  in the reusable sensor cable assembly  130  in order to reduce the cost of the disposable patch assembly  110 . The sensor cable assembly  130  is connected to the patch assembly using an easy to operate snap-fit connection. This force will hold the re-usable to the disposable part. The sensor cable assembly may be positioned in one of several orientations around the central axis of the patch assembly but rotation is prohibited by the combination of the engagement element  114  and the matching indentations in the foam disk  112 . 
         [0057]      FIG. 3  depicts a perspective view of the sensor housing  122  showing the upper sensor housing  122   a,  the lower sensor housing  122   b  and the ridge  123 . Sensor assembly  122  preferably includes the strain relief element  125  but may also be substantial circular without such element. Strain relief element  125  may be integral with sensor housing  122  or may comprise a separate polymeric sleeve that covers a portion of sensor cable  124 . 
         [0058]      FIG. 4  depicts a perspective view of a further embodiment of a patch and sensor cable connector in accordance with the present invention. Sensor housing  222  has a plurality of indentations  223  which are adapted to engage under flexible engagement members  215  which form a portion of engagement element  214 . As in the previous embodiment described above, sensor housing  222  forms a part of a sensor cable assembly  230  and engagement element  214  form a part of the patch assembly  110 E Engagement element  214  is made from a polymer that is sufficiently flexible to enable flexible engagement members  215  to be pushed toward the periphery while the sensor cable assembly  230  is inserted into the engagement element  214 . The snap of re-usebable to disposable part is held using a cantilever beam tab. The disposable part will have the lever which deflects during the snapping operation. The normal forces exherted from the cantilever beam hold the snap together 
         [0059]      FIGS. 5 and 6  depict a planar top view and cross sectional view of another embodiment of a patch and sensor assembly in accordance with the present invention. Patch and sensor assembly  300  comprises two portions: a patch cable assembly  310  and a sensor cable assembly  330 . Patch cable assembly  310  comprises a foam disk  312  having indentation  313  (with portions  313   a  and  313   b ) to accommodate the sensor housing  322  and engagement element  314 . Two separate cables are used to connect the biosensor and ACL sensor to the mapping and localization system. ACL cable  334  is used to connect the ACL sensor layer  316  to the system for transmittal of current information to the localization system. Alternatively, the ACL cable  334  can be substantially shorter than the length necessary to reach to the mapping and localization system and can be adapted to have a fitting that is designed to connect to a mated fitting on a cable that is collinear with the sensor cable. In the configuration, the fitting on the ACL cable is attached to the fitting on the additional cable that forms part of the sensor cable. In this manner, a substantial length of the ACL cable becomes part of the reusable sensor cable assembly. ACL cable  334  is stranded 28 gauge wire that is sandwiched between the foam disk  312  and the ACL sensor layer  316 . ACL sensor layer  316  is a silver chloride coated carbon film of approximately 1 mm with a silver chloride coating of approximately 0.5 mm. Below the ACL sensor layer  316  is a hydrogel layer  317  substantially the same as the one described above with respect to the other embodiment. 
         [0060]      FIG. 5  has the snap feature in the form of three legs. This feature also works similar to principle of cantilever beam of  FIG. 4 . The legs deflect on the reusable part conforming to the opening on the disposable side. When snapped the beam expands providing the normal force to hold the two parts together. 
         [0061]    Sensor cable assembly  330  comprises the engagement element  314 , sensor housing  322  with biosensor  326  mounted inside. Sensor cable  324  is used to connect the biosensor  326  that provides magnetic based localization information to the system. Sensor cable  324  is a 48 gauge braided copper wire coated with a protective polymer with an exposed end welded or bonded, preferably using a conductive epoxy to the biosensor  326 . Strain relief element  325  covers a portion of the sensor cable  324  in order to reduce mechanical stress on the connection of the sensor cable to the biosensor and sensor housing. Biosensor  326  is substantially similar to biosensor  126  for the embodiment described above. Engagement element  314  is a mechanical snap designed to engage patch cable assembly  310 . Engagement element  314  has moveable elements  314   a  and  314   b  that are depressed in order to release and/or engage the engagement element onto the patch assembly. 
         [0062]    An alternative embodiment for a patch and sensor cable assembly in accordance with the present invention is depicted in  FIGS. 7-11 .  FIGS. 7-9  depict the disposable patch cable assembly  410  comprising hydrogel layer  417  which is exposed for adhesion to the patient after removal of release liner  411 . Hydrogel layer  417  is preferably a hydrogel such as Amgel AG603 and is approximately 0.025 inch in thickness. Release liner  411  is approximately 4.5 inches square and is comprised of 0.005 inch thick polyethylene terephthalate (PET) with a silicone coating on the side facing the hydrogel layer  417 . Above hydrogel layer  417  is ACL sensor layer  416  which is a carbon silver chloride disk. More specifically, ACL sensor layer  416  has a base material of conductive carbon and medical grade polyvinyl chloride (PVC) of approximately 0.004 inch in thickness with a patient facing (bottom) coating of silver-chloride and a top coating of silver both approximately 0.001 inch in thickness. 
         [0063]    In electrical contact with ACL sensor layer  416  is the distal end of the cable assembly  434  which is placed under sensor engagement element  414 . Cable assembly  434  is comprised of a 19 strands of tin plated copper wire which are stripped at the distal end  434   a  and fanned out to provide contact with the top side of the ACL sensor layer  416 . Cable assembly  434  should be covered with a jacket and meet requirements of all ANSI standards related to cables for medical devices. The proximal end of the cable assembly  434   b  should have a socket assembly which is adapted to connect to the mapping and localization system or an interface cable for such a system for which it is adapted. The overall length of cable assembly  434  is approximately 36 inches. Sensor engagement element  414  is made of Lexan® material or other polycarbonate material and is adapted to receive the distal end of the sensor cable assembly which is adapted to fit under lip  414   a  and be secured by prongs  414   b.  Foam disk  412   a  is a circular disk of approximately 0.005 inch thick white polyethylene foam with a medical grade acrylic pressure sensitive adhesive on its patient facing side and adheres to sensor engagement element  414 , the distal end of the cable assembly  434  and a portion of the ACL sensor layer  416 . Foam disk  412   b  is a circular foam disk with a plurality of indentations for structural integrity and one for placement of the sensor cable  424 . Foam disk  412   b  has an adhesive on its patient facing side that causes it to adhere to the top side of foam disk  412   a.  Foam disk  412   b  is comprised of white volara type-A closed cell polyethylene foam or an equivalent. 
         [0064]      FIGS. 10-11  depict the reusable sensor cable assembly  430  for use with the patch cable assembly of  FIGS. 7-9 . Sensor cable assembly  430  comprises the engagement elements  414   c  and  414   d,  sensor housing  422  with biosensor  426  mounted inside. Sensor cable  424  is used to connect the biosensor  426  that provides magnetic based localization information to the mapping and localization system (such as the Carto® system described herein) through a connector  428 . Sensor cable  424  is a 48 gauge braided copper wire coated with a protective polymer with an exposed end welded or bonded, preferably using a conductive epoxy  427  to the biosensor  426 . Strain relief element  425  covers a portion of the sensor cable  424  in order to reduce mechanical stress on the connection of the sensor cable to the biosensor and sensor housing. Biosensor  426  is substantially similar to biosensor  126  for the embodiment described above. Engagement element  414   c  is an indentation in the top of the sensor housing substantially around the circumference of the housing and which is designed to engage the lip  414   a  of sensor engagement element of the patch cable assembly  410 . Engagement element  414   b  is an indentation in the proximal end of the bottom of the sensor housing  422  that are adapted to engage prongs  414   b  of patch cable assembly  410  in a snap-fit manner. 
         [0065]    The preceding description has been presented with reference to presently preferred embodiments of the invention. Workers skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structure may be practiced without meaningfully departing from the principal, spirit and scope of this invention. 
         [0066]    Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and illustrated in the accompanying drawings, but rather should be read consistent with and as support to the following claims which are to have their fullest and fair scope.