Patent Publication Number: US-2022225960-A1

Title: Pull-cable management for steerable catheter

Description:
FIELD OF THE INVENTION 
     This invention relates to the field of medical instruments, and in particular to a method and system for managing articulation pull-cables in a steerable catheter or other steerable instruments, such as endoscopes, gastroscopes, and transesophageal echocardiography (TEE) probes. 
     BACKGROUND OF THE INVENTION 
     Catheters are commonly used for situating elements within passages in a patient&#39;s body, to monitor particular biometrics, perform surgical procedures, administer medication, and so on. To navigate through the passages, steerable catheters having an articulating distal end have been developed. 
       FIGS. 1A-1C  illustrate an example prior-art steerable catheter  100 . The catheter  100  comprises a handle  110 , an insertion tube  120 , a flexible distal end  130 , and a transducer  170 . The transducer  170  acquires imaging data via ultrasound. Other devices may be substituted for transducer  170 , these devices may receive biometrics of a patient and/or optical images of internal passages, or it may execute tasks such as making incisions, clearing blockages, administering medication, and so on. To perform these actions, the handle  110  is coupled to a medical-instrument controller (not shown) and is coupled to the transducer  170  via one or more transducer cables  150  within the insertion tube  120 . In the example of the ultrasound transducer  170  above, the steerable catheter  100  may be an ultrasound probe, such as a transesophageal echocardiography (TEE) ultrasound probe, a transvaginal ultrasound probe, for use with an ultrasound system. 
       FIG. 1B  illustrates the catheter  100  in a ‘neutral’ state wherein the flexible distal end  130  is not bent or twisted. The handle  110  includes an articulation controller  115  that is coupled to the flexible distal end  130  via articulation pull-cables  160   a ,  160   b  (collectively, articulation pull-cables  160 ) that extend through the insertion tube  120  to the flexible distal end  130 . 
     As illustrated in cross-section  2 A, these articulation pull-cables  160  are fixedly attached to a terminator  175  that is situated at the transducer-end of the flexible distal end  130 , and can be selectively tensioned/pulled by the articulation controller  115 . 
     As illustrated, the articulation pull-cables  160   a ,  160   b  are situated opposite each other at an outer perimeter area of the terminator  175 . This enables two degrees of freedom for adjusting the orientation of the flexible distal end  130 . In some embodiments, the flexible distal end  130  includes structural details that limit the bending of the flexible distal end  130  in the two opposite directions. When the upper cable  160   b  is pulled via the articulation controller  115 , and the lower cable  160   a  is correspondingly slackened, via rotation  118  of the articulation controller  115 , the tension causes the flexible distal end  130  to twist upwards, as illustrated in  FIG. 1A . Reversing the rotation  119  on the articulation controller  115  causes the lower cable  160   a  to be pulled and the upper cable  160   b  to be slackened, causing the flexible distal end  130  to twist downward, as illustrated in  FIG. 1C . 
     Although two articulation pull-cables  160   a ,  160   b  are illustrated, a steerable catheter may include a larger plurality of cables situated on the perimeter of the terminator  175  to provide additional degrees of freedom of movement. Typically, four articulation pull-cables are provided to provide horizontal and vertical bending of the flexible distal end  130 . 
     In some embodiments, as illustrated in  FIG. 3 , pull-cable lumens  165  are provided through the flexible distal end  130  to provide a more uniform tension within the flexible distal end  130  as the articulation pull-cables  160  are tensioned/pulled. 
     For proper articulated steering, the flexible distal end  130  should be more flexible than the insertion tube  120 , yet the insertion tube  120  must provide sufficient flexibility to minimize a patient&#39;s discomfort as the insertion tube  120  travels within the patient&#39;s internal vessels. Accordingly, a single lumen  190  is provided for routing the transducer cables  150  and articulation pull-cables  160 , as illustrated in the cross-section of  FIG. 2B , so that the flexibility of the insertion tube  120  may be determined primarily by the dimensions and composition of the material forming the cylindrical insertion tube  120 . The single lumen  190  also facilitates the insertion/routing of the cables  150 ,  160  within the insertion tube  120 . However, this structure-less lumen  190  introduces issues that affect the reliability and longevity of the steerable catheter  100 , as detailed below. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide a more robust catheter or similar elongated medical instrument device design by providing structure for cable routing within the insertion tube of a steerable catheter or (elongated) device without significantly affecting the flexibility of the insertion tube. 
     To better address one or more of these concerns, in an embodiment of this invention, the insertion tube may include a plurality of inserts that are spaced along the insertion tube from the handle to the distal end. Each insert of the plurality of inserts may include a plurality of lumens comprising one or more transducer-cable lumens and a plurality of pull-cable lumens, wherein the plurality of lumens isolate the transducer cable and each of the plurality of articulation pull-cables from each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in further detail, and by way of example, with reference to the accompanying drawings wherein: 
         FIGS. 1A-1C  illustrate an example prior art steerable catheter. 
         FIGS. 2A-2B  illustrate example cross-sections of the prior art steerable catheter. 
         FIG. 3  illustrates an example prior art flexible distal end of a steerable catheter. 
         FIG. 4  illustrates an example insert for placement within an insertion tube. 
         FIG. 5  illustrates a plurality of inserts in an insertion tube. 
         FIGS. 6 and 7  illustrate alternative insert structures. 
         FIG. 8  illustrates a string of components for insertion into an insertion tube. 
         FIG. 9  illustrates an alternative insert structure. 
     
    
    
     Throughout the drawings, the same reference numerals indicate similar or corresponding features or functions. The drawings are included for illustrative purposes and are not intended to limit the scope of the invention. 
     DETAILED DESCRIPTION 
     In the following description, for purposes of explanation rather than limitation, specific details are set forth such as the particular architecture, interfaces, techniques, etc., in order to provide a thorough understanding of the concepts of the invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments, which depart from these specific details. In like manner, the text of this description is directed to the example embodiments as illustrated in the figures, and is not intended to limit the claimed invention beyond the limits expressly included in the claims. For purposes of simplicity and clarity, detailed descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail. 
     It is understood that the implementation of the following-described inventions in a catheter used in blood vessels is merely exemplary. The scope of the invention encompasses any steerable devices, such as elongated medical devices, including catheters, which are intended to be inserted into bodily vessels, canals, passageways and cavities, and which have steerable distal portions for use in imaging, medical procedures, placement of implants, removal of implants and the like. 
     Non limiting examples of other such medical devices falling within the scope of the invention are endoscopes, gastroscopes, transvaginal ultrasound probes, and transesophageal echocardiography (TEE) ultrasound probes. In an embodiment including a TEE, transducer  170  is of course an ultrasound transducer. The inventions as described below for use in the exemplary catheters may be readily implemented in these other elongated medical devices as well, and thus enjoy similar benefits and improvements over the prior art arrangements. 
     As mentioned above, the prior art catheter is prone to premature failure due to the structure-less lumen  190  of the insertion tube  120 , illustrated in  FIG. 2B . After repeated usage, the cables  150 ,  160  often become entangled with each other, causing an increased resistance in the tensioning and slackening of the articulation pull-cables  160 . This increased resistance can often lead to a premature failure of the catheter  100  due to an inability to pull or slacken one of the articulation pull-cables  160 . This increase of resistance can be lessened by encasing each articulation pull-cable  160  in a protective sleeve that is sized to enable the articulation pull-cable  160  to be pulled and slackened, and sufficiently rigid to withstand deformation by the other cables. However, such a protective shield on each articulation pull-cable  160  would significantly affect the overall flexibility of the insertion tube  120 . 
       FIG. 4  illustrates an example insert  400  that provides structure within an insertion tube  420 . The example insert  400  includes a transducer lumen  450  through which one or more transducer cables  150  transit, and a plurality of pull-cable lumens  460 , through which a plurality of steering cables  160  transit. As illustrated, the pull-cable lumen  460  is C-shaped, and forms an enclosed volume when situated within the insertion tube  420 . 
     As in a conventional catheter as illustrated in  FIG. 1 , the transducer cables  150  are coupled to a transducer  170  at a flexible distal end  130  of the catheter, and to the handle  110  for coupling to a medical control device (not illustrated) in the handle  110  or external to the handle  110 . The articulation pull-cables  160  are fixedly attached to a terminator  175  at the far end of the flexible distal end  130 , and coupled to an articulation control element  115  in the handle  110 . Depending upon the structure of the control element  115 , the articulation pull-cables  160  may be fixedly attached to the control element  115 , or moveably attached to the control element  115 , such as a pair of articulation pull-cables  160  comprising a continuous cable on a perimeter of a wheel that is rotated by the control element  115 , exerting tension on one articulation pull-cable of the pair and slackening the other articulation pull-cable. The insertion tube  120  is attached to the handle  110  and the flexible distal end  130 . 
     Non limiting examples of the transducer  170  according to the present disclosure are an electromechanical transducer, an electroacoustic transducer such as an ultrasonic (or ultrasound) transducer. 
     The lumens  450 ,  460  provide isolation of the articulation pull-cables  160  from the transducer cables  150 , and from each other. The pull-cable lumens  460  are sized to enable free travel of the articulation pull-cables  160 . In embodiments of this invention, the articulation pull-cables  160  or the pull-cable lumen  460 , or both, may be coated with a lubricous material that facilitates travel of the articulation pull-cable through the pull-cable lumen. In some embodiments, the insert comprises lubricous material to facilitate insertion of the insert into the insertion tube  420 . In some embodiments, the insert comprises a high-temperature resilient material. 
     Although the insert  400  may extend the entire length of the insertion tube  420 , such a structure is likely to interfere with the flexibility of the insertion tube  420 . Accordingly, in embodiments of this invention, a plurality of inserts  400  are situated along the length of the insertion tube, as illustrated in  FIG. 5 . To prevent displacement or rotation of each insert, the inserts  400  may be attached to the insertion tube  420  using heat staking, RF welding, or other attachment techniques. 
       FIGS. 6 and 7  illustrate alternative structures for the insert  400 . In  FIG. 6 , an enclosing pull-cable lumen  460  is provided for each articulation pull-cable  160 , to facilitate assembly. In this embodiment, the transducer cables  150 , the articulation pull-cables  160 , and the inserts  400  can be pre-assembled as a string of components that are subsequently enclosed by the insertion tube  420 , as detailed further below. 
       FIG. 7  illustrates an example embodiment wherein the transducer cables  150  are embedded in the insert  400 . That is, each insert  400  is molded or otherwise formed around the transducer cables  150  such that the cables  150  are fixedly attached to each insert  400 . In this embodiment, closed transducer-cable lumens  450  are formed by the cables  150  as each insert is formed. 
       FIG. 8  illustrates an example string of components  800  comprising the transducer cables  150  embedded in each of a plurality of inserts  400 . Also embedded in each insert  400  is a draw wire  850 . The draw wire  850  may be used to pull the string  800  through the insertion tube  420  to create the assembly illustrated in  FIG. 5 . 
     If the inserts  400  include enclosing pull-cable lumens  460  as illustrated in  FIG. 6 , the articulation pull-cables  160  may be strung through the pull-cable lumens  460  of this string of components  800 . Alternatively, if the inserts  400  comprise open pull-cable lumens  460  as illustrated in  FIG. 7 , the articulation pull-cables  160  may be laid into each pull-cable lumen  460  of the inserts  400  as a string of components similar to the string of components  800  are drawn into the insertion tube  420 . 
       FIG. 9  illustrates an example insert that is structured to capture each articulation pull-cable  160  as it is laid into the pull-cable lumen  460 . As illustrated, the insert  400  includes a trough that has an opening  960  that is slightly smaller than the diameter of the articulation pull-cable  160 . In this embodiment, the insert  400  comprises a resilient material that enables the larger articulation pull-cable  160  to be inserted through the smaller opening  960 . Once inserted, the articulation pull-cable  160  is captured by the pull-cable lumen  460  within the pliable material as it returns to its original state of having a smaller opening  960  than the diameter of the articulation pull-cable  160 . 
       FIG. 10  illustrates an example flow diagram  1000  for assembling a steering catheter with articulation pull-cable support within the insertion tube. One of skill in the art will recognize that the illustrated order of steps is provided for ease of understanding, and the steps may be performed in different order, and/or some steps may be performed concurrently. One of skill in the art will also recognize that, with the exception of installing the inserts with articulation pull-cable and transducer cable lumens in the insertion tube, the assembly of the steering catheter is consistent with known prior art techniques that do not require detailed descriptions in this specification. 
     At  1010 , a plurality of inserts having pull-cable lumens are obtained. These may be pre-formed inserts, or created by extrusion or molding about a draw wire and/or transducer cables. At  1015 , a draw wire is attached to each insert, and at  1020 , one or more transducer cables are routed through each insert. As noted above, steps  1010 ,  1015 , and  1020  may be performed concurrently, as when the inserts are coextruded over the draw wire and the transducer cable(s). 
     At  1025 , the articulation pull-cables are routed through the pull-cable lumens of each insert. If the pull-cable lumens are troughs, the articulation pull-cables may be temporarily held in place until the insert is about to be drawn into the insertion tube. 
     At  1030 , the draw wire is passed through the insertion tube, and at  1035 , the draw wire is drawn to draw the assembly of inserts, transducer cable(s), and articulation pull-cables into the insertion tube. In alternative embodiments, the insertion tube may be extruded or otherwise formed over the assembly, eliminating the need for a draw wire. 
     At  1040 , the inserts are attached to the insertion tube. This attachment is optional; if the inserts are sufficiently held in place by elastic pressure from the walls of the insertion tube, or by the formation of the insertion tube upon the assembly, further attachment may be unnecessary. As noted above, if attachment is necessary, heat staking, RF welding, or other attachment techniques may be used. In some embodiments, the insertion tube may be a heat-shrink material that facilitates placement of the assembly in the insertion tube, and heat is subsequently applied to attach the insertion tube to each insert. 
     At  1045 , the transducer cables are attached at each end to couple the transducer to the handle, and at  1050 , the articulation pull-cables are attached at each end of the assembly so as to couple the flexible distal end to an articulation control in the handle. 
     Final assembly of the catheter is performed by coupling the insertion tube to the handle and the flexible distal end, at  1055 . 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. 
     For example, it is possible to operate the invention in an embodiment wherein a continuous insert is coextruded over the transducer cables, then selectively etched or otherwise reduced in diameter to create a plurality of full-size (unetched) inserts between these thinner (etched) segments. For example, the material between the pull-cable lumens  460  along the perimeter of the continuously extruded insert can be selectively removed, leaving only the transducer cables embedded in the residual material between the unmodified inserts. 
     Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Reference signs in the claims, if any, should not be construed as limiting the scope of the claims.