Abstract:
A method of producing a miniaturized set of orthogonal inductive coils set inside a tube. The method includes providing a platform, attaching the coils to the platform and providing a tube, encompassing the coils.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The ability to accurately determine the position of a device within the body currently yields a considerable benefit for at least one medical procedure. This is the electrophysiological mapping of the heart. Such mapping frequently permits the location and treatment of the neurological disorder that has given rise to a heart arrhythmia. In order to accurately perform this mapping a transceiver head must be introduced into the heart by way (in part) of the femoral artery. The position and orientation of this transceiver head must be accurately monitored.  
           [0002]    In order to perform this monitoring a set of orthogonally positioned inductive coils are fixed at the transceiver head and conductively connected through the catheter to the outside of the body, where the current in each of the inductive coils can be read. Cooperating with these coils, powerful magnets are arrayed about the imaging station, so that the current through each coil is dependent on its orientation relative to the magnetic field created.  
           [0003]    Heretofore, the manufacture of the unit in which the coils reside has been a challenging and expensive operation. Each coil was soldered to a pair of wires and adjusted so that its position was generally correct. Next the coils and attached wires are gently placed into a polymer tube, which is then filled with epoxy to retain the coils in their generally mutual orthogonal positions and to retain the tube in its protective position.  
           [0004]    Performing this method resulted in many problems. First, there was the difficulty in maintaining the mutually orthogonal orientation of the inductive coils during their insertion into the tube and the filling of the tube with epoxy. Also, air pockets would sometimes form as the epoxy was being introduced into the tube.  
         SUMMARY  
         [0005]    In a first separate aspect, the present invention is a method of producing a miniaturized set of orthogonal inductive coils set inside a tube. The method includes providing a platform, attaching the coils to the platform and providing a tube, encompassing the coils.  
           [0006]    In a second separate aspect, the present invention is a miniaturized navigational aid, comprising a set of substantially orthogonal inductive coils. A tube, which includes a single circumferential wall, which in turn, defines at least one aperture, is set about the inductive coils. Adhesive material fills the tube, thereby fixing in place the set of substantially orthogonal inductive coils and wherein a portion of the adhesive material extends into the aperture(s) to securely anchor the tube.  
           [0007]    In a third separate aspect the present invention is a miniaturized navigational device, comprising a set of orthogonal inductive coils and a tube encompassing the inductive coils. The tube is made of a flexible sheet having a first edge and a second edge and being rolled up so that the first edge abuts the second edge. 
       
    
    
       [0008]    The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a plan view of a flex circuit adapted to be used in the method of the present invention.  
         [0010]    [0010]FIG. 2 is a plan view of a work piece, making use of the flex-circuit of FIG. 1, and constituting a stage in the method of the present invention.  
         [0011]    [0011]FIG. 3 is a perspective view of the work piece of FIG. 2.  
         [0012]    [0012]FIG. 4 is a perspective view of a miniaturized inductive navigational device, constructed according to the method of the present invention.  
         [0013]    [0013]FIG. 5 is a plan view of an alternative flex circuit adapted to be used in the method of the present invention.  
         [0014]    [0014]FIG. 6 is a plan view of an alternative work piece, making use of the flex-circuit of FIG. 5, and constituting an alternative stage in the method of the present invention.  
         [0015]    [0015]FIG. 7 is a perspective view of the work piece of FIG. 6.  
         [0016]    [0016]FIG. 8 is a perspective view of an alternative miniaturized inductive navigational device constructed according to the method of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]    Referring to FIGS.  1 - 4 , in a first preferred embodiment of a method of manufacturing a miniaturized navigational device  8  (FIG. 4), a piece of flex-circuit  10  is provided that is sized to accommodate a set of inductive coils  12 ,  14  and  16  when rolled into a tube. The flex circuit has a set of six traces  18 , each of which extends from an area adapted to a wire coming from the left in the FIGS., to a position adapted to permit the attachment of a terminal  17  of one of the inductive coils  12 ,  14  and  16 .  
         [0018]    Each of the three coils  12 ,  14  and  16  may be placed by a robot onto the flex circuit, which preferably has been readied for each with a drop of epoxy to hold the coil in place during further operations. The termini (not shown) of each coil are then soldered to the appropriate flex circuit trace  18 . A cable  20  is composed of a set of six wires  22  and a shield  24 . Each wire  22  is soldered to a circuit trace  18 . Although more soldering operations are required than would be necessary if wires  22  were directly soldered to the terminals of the inductive coils  12 ,  14  and  16 , the soldering operations are made far more repeatable and therefore may be automated. In addition the shield  24  of cable  20  is soldered to flex circuit  10  to affirmatively anchor flex circuit  10  to cable  20 .  
         [0019]    After the electrical and physical attachment of the inductive coils  12 ,  14  and  16  to the flex circuit  10 , it is rolled up so that its two side edges  32  precisely abut each other. Epoxy resin is poured in through a first one of two holes created by a set of four scallops  34  that are defined by the flex circuit  10 . The second of the two holes created by scallops  34  permits the exit of air, to accommodate the introduced epoxy and avoid the formation of air bubbles. Although both sides of the tube formed by flex circuit  10  are open, it is possible at this point in the manufacturing process that the manufacturing equipment could occlude one or both ends. The amount of epoxy poured onto assembly  10  is chosen to be slightly greater than the amount that can be accommodated by flex circuit  10  and so, as a result, some epoxy oozes through a set of apertures  30 , thereby positively anchoring flex circuit  10  to wires  22  and inductive elements  12 ,  14  and  16 .  
         [0020]    Moreover, because inductive elements  12 ,  14  and  16  are positioned and retained on flex circuit  10  prior to being connected to wires  22 , the probability that these elements will be truly orthogonal to one another is greatly increased.  
         [0021]    Referring to FIGS.  5 - 8 , in a second preferred embodiment, elements  108 ,  110 ,  112 ,  114 ,  116 ,  117 ,  118 ,  120 ,  122 ,  124  and  132  each performs the same function as the element numbered by the same reference number, minus  100 , in the first preferred embodiment. In addition, however, flex circuit  110  is laser scored along score lines  148 . A score line  148  separates inductive coils  112  and  116  from inductive coil  114 . When flex circuit  110  is folded about the score lines  148 , inductive coil  114  is placed in close proximity with coils  112  and  116  and flex circuit  110  forms a square tube. A set of slots  150  accepts a pair of tabs  152  to positively close the square tube. Slots  150  also allow air to leave device  8 . Some epoxy resin also seeps into slots  150 , thereby positively retaining flex circuit  110 .  
         [0022]    The terms and expressions which have been employed in the foregoing specification are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.