Abstract:
A catheter is provided with improved position and/or location sensing with the use of single axis sensors that are mounted directly along a length or portion of the catheter whose position/location is of interest. The magnetic based, single axis sensors are provided on a single axis sensor (SAS) assembly, which can be linear or nonlinear as needed. A catheter of the present invention thus includes a catheter body and a distal member of a particular 2D or 3D configuration that is provided by a support member on which at least one, if not at least three single axis sensors, are mounted serially along a length of the support member. In one embodiment, the magnetic-based sensor assembly including at least one coil member that is wrapped on the support member, wherein the coil member is connected via a joint region to a respective cable member adapted to transmit a signal providing location information from the coil member to a mapping and localization system. The joint region advantageously provides strain relief adaptations to the at least one coil member and the respective cable member from detaching.

Description:
FIELD OF INVENTION 
       [0001]    This invention relates to a catheter, in particular, a catheter whose shaft portion is adapted for position sensing to provide visualization of the shaft portion. 
       BACKGROUND 
       [0002]    Electrode 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. Atrial fibrillation is a common sustained cardiac arrhythmia and a major cause of stroke. This condition is perpetuated by reentrant wavelets propagating in an abnormal atrial-tissue substrate. Various approaches have been developed to interrupt wavelets, including surgical or catheter-mediated atriotomy. Prior to treating the condition, one has to first determine the location of the wavelets. Various techniques have been proposed for making such a determination, including the use of catheters with a distal mapping and/or ablation electrode assembly that is adapted to measure activity within a pulmonary vein, coronary sinus or other tubular structure about the inner circumference of the structure. For visualization of a distal electrode assembly, one or more single Axis Sensors (SAS) may be mounted on a support member of the distal electrode assembly, as described in U.S. Pat. No. 8,792,962, issued Jul. 29, 2014, entire content of which is incorporated herein by reference. 
         [0003]    Visualization of a catheter shaft proximal of a distal electrode assembly, including any portion of the catheter shaft, such as a proximal portion or a distal deflectable portion, may also be helpful to an operator during mapping and/or ablation procedures. It is therefore desirable for a catheter shaft to enable visualization, and especially where such visualization can be accomplished for catheter shafts with smaller diameters without increasing shaft diameter. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention is directed to a catheter with improved position and/or location sensing with the use of magnetic-based, single axis sensors (SAS) that are embedded in a multi-layered sidewall of catheter tubing to enable position sensing and visualization of the catheter tubing. 
         [0005]    In some embodiments of the present invention, a catheter comprises an elongated body having a multi-layered portion with a magnetic-based sensor subassembly, a control handle proximal of the elongated body, and a distal section distal of the elongated body, the distal section having an electrode. Advantageously, the multi-layered portion has a first layer, a braided mesh over the first layer, and a second layer, the first layer defining an inner lumen, the second layer having a reflowed construction over the braided mesh and the first layer, and the first and second layers being of similar thermoplastic materials. Mounted on top of the second layer is the magnetic-based sensor subassembly with a first wire sensor with a first wire coil portion wounded on the second layer at a first location, and a first wire distal portion and a first wire proximal portion extending longitudinally toward a proximal end of the elongated body. 
         [0006]    In detailed embodiments, the magnetic-based sensor subassembly has a second wire sensor with a second wire coil portion, a second wire distal portion and a second wire proximal portion, the second wire coil portion wounded on the second layer at a second location proximal of the first location, the second wire distal portion and the second wire proximal portion extending longitudinally toward a proximal end of the elongated body. 
         [0007]    In detailed embodiments, the first wire distal portion and the first proximal portion of the first wire sensor pass between the second layer and the second wire coil portion. 
         [0008]    In detailed embodiments, the magnetic-based sensor assembly includes a nonconductive sleeve fitted on the second layer separating the first wire distal and proximal portions from contacting the second wire coil portion. 
         [0009]    In other embodiments, the magnetic-based sensor assembly has a third wire sensor with a third wire coil portion, a third wire distal portion and a third wire proximal portion, the third wire coil portion being at a third location on the second layer of the elongated body, the third location being proximal of the first and second locations, the third wire distal portion and the third wire proximal portion extending longitudinally toward a proximal end of the elongated body. 
         [0010]    In detailed embodiments, the first distal portion and the second proximal portion of the second wire sensor pass between the second layer and the second wire coil portion at the second location and between the second layer and the third wire coil portion at the third location. 
         [0011]    In detailed embodiments, the magnetic-based sensor assembly includes a nonconductive sleeve fitted on the second layer separating the first and second wire distal and proximal portions from contacting the third wire coil portion. 
         [0012]    In other embodiments, the elongated body has a third layer covering at least the multi-portion of the elongated body to seal the magnetic-based sensor subassembly. 
         [0013]    In some embodiments of the present invention, a catheter comprises an elongated body having a multi-layered portion with a magnetic-based sensor subassembly, a control handle proximal of the elongated body, and a distal section distal of the elongated body, the distal section having an electrode. Advantageously, the multi-layered portion has a first layer with multiple lumens, a braided mesh over the first layer, and a second layer, the first layer defining an inner lumen, the second layer having a reflowed construction over the braided mesh and the first layer, and the first and second layers being of similar thermoplastic materials. Mounted on top of the second layer is the magnetic-based sensor subassembly with a first wire sensor with a first wire coil portion wounded on the second layer at a first location, and a first wire distal portion and a first wire proximal portion extending longitudinally toward a proximal end of the elongated body. 
         [0014]    In detailed embodiments, the first wire distal portion and the second wire proximal portion pass through respective through-holes formed in the multi-layered portion in communication with the inner lumen, wherein the first wire distal portion and the first wire proximal portion extend longitudinally toward a proximal end of the elongated body through the inner lumen. 
         [0015]    The present invention is also directed to a method of method of manufacturing a catheter tubing with improved position and/or location sensing with the use of magnetic-based, single axis sensors (SAS) that are embedded in a multi-layered sidewall of catheter tubing to enable position sensing and visualization of the catheter tubing. 
         [0016]    In some embodiments, the method comprises extruding the first layer, placing the braided mesh on the first layer, placing a first heat shrink tubing as the second layer over the braided mesh and the first layer, and heating the first heat shrink tubing to reflow the second layer over the braided mesh and the first layer. 
         [0017]    In some embodiments, the method further comprises placing a second heat shrink tubing over at least the first coil portion, and heating the second heat shrink tubing to form a seal over at least the first coil portion. 
         [0018]    In other embodiments, method of manufacturing comprising extruding the first layer, placing the braided mesh on the first layer, placing a first heat shrink tubing as the second layer over the braided mesh and the first layer, heating the first heat shrink tubing to a temperature within the overlapping temperature ranges of the first and second thermoplastic materials, and wrapping the first wire sensor on the second layer. 
         [0019]    In some embodiments, the method further comprises supporting the first layer with a mandrel that remains with the first layer during at least the wrapping the first wire sensor on the second layer. 
         [0020]    In yet other embodiments, a method of manufacturing comprises extruding the first layer, placing the braided mesh on the first layer, placing a first heat shrink tubing over the braided mesh and the first layer, heating the first heat shrink tubing to a temperature to sufficiently melt the first and second layers to adhere to each other, placing a respective sleeve on the second layer for each wire sensor, and wrapping each wire sensor on the second layer with a mandrel supporting the first layer, the braided mesh and the second layer. 
         [0021]    In detailed embodiments, the method further comprises placing a second heat shrink tubing as a third layer over each wire sensor, and heating the second heat shrink tubing to seal each wire sensor on the elongated body. 
         [0022]    In detailed embodiments, the method further comprises injecting epoxy through the second heat shrink tubing to encase each wire sensor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings. It is understood that selected structures and features have not been shown in certain drawings so as to provide better viewing of the remaining structures and features. 
           [0024]      FIG. 1  is a top plan view of a catheter of the present invention, in accordance with one embodiment. 
           [0025]      FIG. 2A  is a side view of a catheter tubing of the catheter of  FIG. 1 , with parts broken away. 
           [0026]      FIG. 2B  is an end cross-sectional view of the catheter tubing of  FIG. 2A , taken along line B-B. 
           [0027]      FIG. 3A ,  FIG. 3B  and  FIG. 3C  are side views of a catheter tubing of  FIG. 2A , during manufacturing, in accordance one embodiment of the present invention. 
           [0028]      FIG. 4A  is a side view of a catheter tubing, with parts broken away, in accordance with another embodiment of the present invention. 
           [0029]      FIG. 4B  is an end cross-sectional view of the catheter tubing of  FIG. 4B , taken along line B-B. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    Referring to  FIG. 1 , the present invention is directed to a catheter  10  with a multi-layered catheter shaft portion  11  adapted for position sensing for visualization of the shaft portion  11 . The shaft portion  11  may be part of an elongated catheter tubing, for example, an elongated catheter body  12 , or a shorter deflection portion  14  distal of the catheter body  12 , wherein position sensing is accomplished by one or more single axis sensors (SAS) encased in the shaft portion  11  which is constructed of multiple layers of similar materials, for example, with similar melting temperatures to promote a composite construction and adherence of the layers. 
         [0031]    Proximal of the catheter body  12  is a control handle  16  with mechanisms that are manipulated by a user to accomplish, for example, bi-directional deflection of the deflection section  14 . Distal of the deflection portion  14  is a distal electrode assembly  17  with one or more electrodes arranged in a 2-D or 3-D configuration. 
         [0032]    With reference to  FIGS. 2A and 2B , the catheter body  12  comprises a single, central or axial lumen  18 . The catheter body  12  is flexible, i.e., bendable, but substantially non-compressible along its length. As part of the catheter body  12 , the shaft portion  11  and the catheter body  12  have a similar construction comprising an inner wall or first layer  21  of a thermoplastic material, an imbedded braided mesh  22 , and a thin wall or second layer  23  of a thermoplastic material surrounding the braided mesh  22  and the first layer  21 . Suitable thermoplastic materials include, for example, thermoplastic elastomers (TPEs) and thermoplastic polyurethanes (TPUs), such as PELLETHANE or PEBAX, where PEBAX has a melting temperature ranging between about 272° F. (133° C.) and 345° F. (174° C.) and PELLETHANE has a melting temperature ranging between about 360° F. (182° C.) and 441° F. (227° C.). In some embodiments, the same thermoplastic material is used for the first layer  21  and the second layer  23 . In some embodiments, the first layer  21  comprises a first thermoplastic material and the second layer  23  comprises a second thermoplastic material similar to the first thermoplastic material. Similar thermoplastic materials are understood herein to be thermoplastic materials have melting temperatures such that heating and reflowing of at least one layer promote and enable bonding and adherence of one layer to the other layer. In some embodiments, similar thermoplastic materials have melting temperature ranges that are similar, which include thermoplastic materials with melting temperature ranges that overlap by or have in common at least about one degree in Fahrenheit (one degree in Celsius), preferably about five degrees in Fahrenheit (three degrees in Celsius), and more preferably about ten degrees in Fahrenheit (five degrees in Celsius). It is understood that “similar” can refer to the same chemical materials having the same melting temperatures, and to different chemical materials having different chemical make-ups but similar melting temperature ranges as defined herein. In some embodiments, the “different chemical materials” might include, for example, similar polymer backbones but different pendant groups, or different polymer backbones. 
         [0033]    The imbedded braided mesh  22  of stainless steel or the like is provided to increase torsional stiffness of the catheter body  12  so that when the control handle  16  is rotated the length of the catheter body  12  rotates in a corresponding manner. The single lumen  18  permits components passing therethrough (including, for example, irrigation tubing  25 , electrode lead wires  26 , puller wires  13   a ,  13   b , etc.) to float freely within the catheter body  12 . However, if desired or appropriate, the catheter body  12  may also have a multi-lumened extrusion construction. 
         [0034]    The thin wall or second layer  23  is constructed of a second thermoplastic material which is reflowed over the braided mesh  22 . With the first and second layers  21  and  23  being of the same or similar thermoplastic materials, reflowing the second layer  23  over the braided mesh  22  and the first layer  21  promotes the catheter body  12  having a composite construction and adherence of the first and second layers  21  and  23  to each other. 
         [0035]    The first layer  21  may have an outer diameter ranging between about 0.069″ and 0.073″, and preferably, a diameter of about 0.071″. A sidewall of the first layer  21  may have a thickness ranging between about 0.003″ and 0.006″, and preferably, a thickness of about 0.004″. 
         [0036]    The second layer  23  may have an outer diameter ranging between about 0.100″ and 0.109″, and preferably, a diameter of about 0.104″. A sidewall of the second layer  23  may have a thickness ranging between about 0.002″ and 0.006″, and preferably, a thickness of about 0.003″. 
         [0037]    As shown in  FIG. 2A , one or more linear single axis sensors (SAS)  40 A,  40 B and  40 C forming a SAS subassembly are mounted on the bonded composite catheter shaft portion  11  as part of the catheter body  12 . The SAS  40 A comprises a coil  32 A of multiple windings of an electrical conductor (e.g., very fine small gauge wire  34 A) situated on an outer surface of the second layer  23 . A distal portion  35 A of the wire passes under the coil  32 A and extends in a longitudinal direction toward a proximal end of the catheter shaft portion  11  and the control handle  16 . A proximal portion  36 A of the wire  34 A also extends in the longitudinal direction toward the proximal end of the catheter shaft  11  and the control handle  16 . The coil  32 A may incorporate strain relief adaptations, including slack and/or windings, as disclosed in U.S. Pat. No. 8,792,962, issued Jul. 29, 2014, entire content of which is incorporated herein by reference. The SAS  40 B and  40 C have a similar construction, and thus similar components thereof are identified in the Figures with similar reference numbers with letter designation of B or C. 
         [0038]    Each SAS interacts with at least one external magnetic field generated by a magnetic field generator positioned, for example, below the patient bed. Each SAS generates signals representative of the relative strengths of the field as sensed by its coil, which signals are transmitted proximally toward the control handle  16  and further to a highly accurate mapping system, such as CARTO, CARTO XP or CARTO 3, available from Biosense Webster, to provide visualization of the shaft portion  11  and to create 3-D anatomical maps of tissue chamber or region of interest in the patient, based on location and orientation of the shaft portion  11  on which the SAS subassembly is mounted. 
         [0039]    As shown in  FIG. 2A , distal SAS  40 A has wire distal portion  35 A and wire proximal portion  36 A, mid SAS  40 B has wire distal portion  35 B and wire proximal portion  36 B, and proximal SAS  40 C has wire distal portion  35 C and wire proximal portion  36 C. To insulate the wire distal and proximal portions of the more distal SAS from the more proximal SAS, a nonconductive sleeve  38  is placed and fitted on the shaft portion  11  between the second layer  23  and the coil  32 , with the wire distal and proximal portions of more distal SAS passing between the sleeve  38  and the second layer  23 . In the embodiment of  FIG. 2A , insulating sleeve  38 B is provided under the coil  32 B to insulate wire portions  35 A and  36 A from the coil  32 A, and insulating sleeve  38 C (also shown in  FIG. 2B ) is provided under the coil  32 C to insulate wire portions  35 A,  36 A,  35 B and  36 B from the coil  32 C. In that regard, the sleeves  38 B and  38 C are shaped and sized to provide sufficient and adequate insulation surfaces on which the coils  32 B and  32 C may be wounded without contacting the underpassing wire portions. The wire  34  may comprise flat ribbon wires that can lie flatter against the second layer  23  for a minimized profile when passed under the sleeves  38 B and  38 C. 
         [0040]    In some embodiments, each SAS includes an encapsulation coating or layer  42  encasing the coil  32 , surrounding it circumferentially on the catheter shaft portion  11  (also shown in  FIG. 2B ). The layer  42  may be of any suitable material, including, for example, epoxy, UV glue, or the like. The encapsulation layer  42  provides a number of benefits, including protecting the coil  32  from exposure to increased temperatures during reflow process, and providing strain relief to minimize wire breakage or damage during assembly and use. For distal SAS  40 A, the encapsulation layer  42 A encases the coil  32 A with the second layer  23 . For mid and proximal SAS  40 B and  40 C, the encapsulating layer  42 B and  42 C encases the coils  32 B and  32 C with the sleeves  38 B and  38 C, respectively. 
         [0041]    In some embodiments, the shaft portion  11  includes an outer wall or third layer  24  that extends over the SAS subassembly, if not also the length of the catheter body  12 . As shown in  FIG. 2A , the third layer  24  protects the coils  32 A,  32 B and  32 C, and the wire distal and proximal portions  35 A,  36 A,  35 B,  36 B,  35 C and  36 C. 
         [0042]    In construction of the catheter body  12 , including the shaft portion  11 , according to some embodiments of the present invention, as shown in  FIG. 3A , the first layer  21  is extruded from an extruder  45  over a mandrel  30  which forms the central lumen  18  ( FIG. 2A ) of the shaft portion  11 . As shown in  FIG. 3B , the mandrel  30  (in broken lines) may remain under the extruded first layer  21  as the mesh  22  is braided over the first layer  21 . As shown in  FIG. 3B , the mandrel  30  may remain under the extruded first layer  21  and the braided mesh  22  as a heat shrink tubing  52  forming the second layer  23  is extruded over or otherwise fitted on the first layer  21  and braided mesh  22 . The mandrel  30  may remain in the first layer  21  as heat is applied to the heat shrink tubing  52  to reflow over the braided mesh  22  and the first layer  21  in forming the second layer  23 . As described above, the heated tubing  52  is reflowed so that the second thermoplastic material can seep through the braided mesh  22  and bond with the first thermoplastic material of the first layer  21 . The similarity in melting temperatures of the first and second thermoplastic materials facilitates such bonding and adherence. 
         [0043]    As shown in  FIG. 3C , the distal most SAS, for example, SAS  40 A is mounted first. Wire distal portion  35 A of thin wire  34 A is laid longitudinally on the outer surface of the second layer  23  and the thin wire  34 A is coiled around the shaft portion  11 , on top of the wire distal portion  35 A. The remainder of the wire distal portion  35 A extends proximally of the coil  32 A toward a proximal end of the catheter body  12 . Proximal of the coil  32 , wire proximal portion  36 A of the wire  34 A is laid longitudinally on the outer surface of the second layer  23  also extending proximally toward a proximal end of the catheter body  12 . 
         [0044]    Before mounting the next distal SAS at a selected location proximal of the distal-most SAS  40 A, for example, the mid SAS  40 B, sleeve  38 B is mounted over the second layer  23  and the wire distal and proximal portions  35 A and  36 A at the selected location. In some embodiments, the sleeve  38 B may be a short heat-shrink tubing that is reflowed over the wire portions  35 A and  36 A, and the second layer  23 . To mount the mid SAS  40 B, wire distal portion  35 B of thin wire  34 B is laid longitudinally on the sleeve  38 B, and the thin wire  34 B is coiled around the shaft portion  11  over the wire distal portion  35 B and the sleeve  38 B (which covers and insulates the wire distal portion  35 A and the wire proximal portion  36 A from the coil  34 B). Wire proximal portion  36 B of the wire  34 B is laid longitudinally on the sleeve  38 B and further on the outer surface of the second layer  23  as it extends proximally toward a proximal end of the catheter body  12 . 
         [0045]    Additional SAS, including SAS  40 C may be mounted in the same manner as described above for SAS  40 B. 
         [0046]    As shown in  FIG. 3C , the third layer  24  may also be applied as a heat shrink tubing  54  which seals in all the components mounted and carried on the shaft portion  11 . The tubing  54  is reflowed over the second layer  23 , the coils  32 A and  32 B, the sleeves  38 B, and the wire portions  35 A,  36 A,  35 A,  35 B. The encapsulation coatings or layers  42 A,  42 B and  42 C (see  FIG. 2B ) may applied to the coils before the tubing  54  is fitted over the coils, or they may be applied via syringe injection through the heat shrink-tubing  54  before it is reflowed into forming the third layer  24 . The third layer  24  is constructed of a third thermoplastic material which may be the same as the first and/or second thermoplastic material, or be similar to the first and/or second thermoplastic material, in promoting bonding and adherence of one or more layers of the multi-layer construction of the shaft portion  11 . 
         [0047]    As shown in  FIG. 3A ,  FIGS. 3B and 3C , the mandrel  30  may remain in the first layer  21  during at least the winding of the coil of the one or more SASes on the second layer  23 , and if not also during the application/reflow of the third layer  24 , so as to maintain the structural shape of the shaft portion  11  and the central lumen  18 . It is understood that the mandrel supporting the structural shape need not be the same mandrel used throughout the manufacturing of the shaft portion  11  but that the mandrel  30  may be removed and replaced with one or more mandrels as suitable or appropriate during the winding of the coil of the one or more SAS on the second layer  23 , and/or any of the reflow stages during manufacturing of the shaft portion  11 . 
         [0048]    It is understood that  FIG. 3A ,  FIG. 3B  and  FIG. 3C  are representative illustrations demonstrating various steps of constructing a multi-layered catheter body with an embedded SAS subassembly within the side wall of the catheter body, in accordance with some embodiments of the present invention. Although the steps illustrated may be performed in an assembly line fashion, with progression from  FIG. 3A , to  FIG. 3B  to  FIG. 3C , the steps may also be performed discretely, in different assembly lines, by different machinery and/or at different locations. For example, while  FIG. 3B  illustrates the reflowing of the heat shrink tubing  52  at one location on the catheter body as occurring simultaneously with the application of the braided mesh  22  at another location on the catheter body, it is understood that the application of the braided mesh may be completed entirely along the length of the catheter body  12  before the heat shrink tubing  52  is fitted over the catheter body  12  and before heat is applied to reflow the tubing  52 . 
         [0049]    At the proximal end of the catheter body  12  that is received in a distal end of the control handle, the proximal and distal portions  35 A,  36 A,  35 B,  36 B,  35 C,  36 C which have extended longitudinally along the catheter shaft  12  between the second layer  23  and the third layer  24  enter the interior of the control handle  16  for connection to a printed circuit board for processing, including, for example, amplification, as known in the art. 
         [0050]    In other embodiments of the present invention, the wire distal and proximal portions  35 A,  36 A,  35 B,  36 B,  35 C,  36 C of each coil  32 A,  32 B and  32 C may extend proximally through a lumen  61  of the catheter shaft, as shown in  FIG. 4A  and  FIG. 4B . A through-hole  70  is formed into the lumen through the sidewall of the catheter shaft portion (through the first layer  21 , the braided mesh  22  and the second layer  23 ) for each wire portion  35 A,  36 A,  35 B,  36 B,  35 C and  36 C. As such, sleeves  38 B and  38 C are not needed. As shown in  FIG. 4A , the extruded first layer  21  may be formed as a multi-lumened tubing with lumens  50 ,  51 ,  52  and  53  (with use of one or more suitable mandrels). The through-hole  70  may be formed to communicate with the lumen  61 , such that the wire portions  35 A,  36 A,  35 B,  36 B,  35 C and  36 C all pass through the dedicated lumen  61  along the length of the catheter shaft. 
         [0051]    In some embodiments, lumen  62  may be provided for irrigation tubing  25  and lumen  65  may be provided for tip electrode lead wires  26 . Diametrically opposing lumens  63  and  64  may be suitable for a pair of puller wires  13   a  and  13   b  to provide the catheter with bi-directional deflection. In that regard, the shaft portion  11  with the one or more embedded SAS in its layered construction is suitable as segment of the deflection portion  14  (as shown in  FIG. 1 ), for example, that extends distal of a single lumened catheter body through which the pair of puller wires extends. Each puller wire has a proximal end anchored in the control handle  16  and a distal end anchored at or near a distal end of the deflection portion  14 . Surrounding each puller wire is a compression coil (now shown) having a proximal end at a proximal end of the catheter body, and a distal end at or near a proximal end of the deflection portion  14 , as known in the art and understood by one of ordinary skill in the art. 
         [0052]    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. Any feature or structure disclosed in one embodiment may be incorporated in lieu of or in addition to other features of any other embodiments, as needed or appropriate. It is understood that a feature of the present invention is applicable to multiplying linear motion of a puller wire, contraction wire, or any other object requiring insertion, removal, or tensioning within a medical device, including the disclosed electrophysiology catheter. As understood by one of ordinary skill in the art, the drawings are not necessarily to scale. 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.