Patent Publication Number: US-2023149670-A1

Title: Medical device for septal crossing with trapping features

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/245,893, filed Jan. 11, 2019, now U.S. Pat. No. 11,554,255; which claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 62/616,848, filed Jan. 12, 2018, the entire disclosure of which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure pertains to medical devices, and methods for manufacturing medical devices. More particularly, the present disclosure pertains to medical device for septal crossing with trapping features. 
     BACKGROUND 
     A wide variety of intracorporeal medical devices have been developed for medical use, for example, intravascular use. Some of these devices include guidewires, catheters, and the like. These devices are manufactured by any one of a variety of different manufacturing methods and may be used according to any one of a variety of methods. Of the known medical devices and methods, each has certain advantages and disadvantages. There is an ongoing need to provide alternative medical devices as well as alternative methods for manufacturing and using medical devices. 
     BRIEF SUMMARY 
     This disclosure provides design, material, manufacturing method, and use alternatives for medical devices. A medical device is disclosed. The medical device comprises: an elongate shaft having a proximal end region and a distal end region; a first lumen defined in the shaft; a second lumen defined in the shaft; wherein the distal end region includes a common lumen region in fluid communication with the first lumen and the second lumen; and a deflectable member disposed within the shaft, the deflectable member being designed to shift between a first configuration where the deflectable member directs a first medical device disposed within the common lumen region into the first lumen and a second configuration where the deflectable member allows a second medical device to move between the common lumen region and the second lumen. 
     Alternatively or additionally to any of the embodiments above, the deflectable member includes a spring ribbon wire. 
     Alternatively or additionally to any of the embodiments above, the deflectable member includes a one-way valve. 
     Alternatively or additionally to any of the embodiments above, the first lumen, the second lumen, or both have a constant diameter. 
     Alternatively or additionally to any of the embodiments above, along at least a portion of the length of the shaft, the first lumen, the second lumen, or both have a variable diameter. 
     Alternatively or additionally to any of the embodiments above, the deflectable member is biased to be in the first configuration. 
     Alternatively or additionally to any of the embodiments above, further comprising a trapper balloon disposed within the first lumen. 
     Alternatively or additionally to any of the embodiments above, the shaft defines a third lumen in fluid communication with the trapper balloon. 
     Alternatively or additionally to any of the embodiments above, the shaft defines a fourth lumen and wherein a shapeable member is disposed within the fourth lumen. 
     Alternatively or additionally to any of the embodiments above, further comprising a distal balloon coupled to the distal end region of the shaft. 
     Alternatively or additionally to any of the embodiments above, the shaft defines a fifth lumen in fluid communication with the distal balloon. 
     Alternatively or additionally to any of the embodiments above, the distal balloon includes a compliant material. 
     A dilator is disclosed. The dilator comprises: an elongate shaft having a proximal end region and a distal end region; a guidewire lumen defined in the shaft; a needle lumen defined in the shaft; wherein the guidewire lumen and the needle lumen merge into a common lumen along the distal end region of the shaft; and a deflectable member disposed within the shaft, the deflectable member being designed to shift between a first configuration where the deflectable member is configured to direct a guidewire device from the common lumen into the guidewire lumen and a second configuration where the deflectable member is deflected in order to allows a needle device to move between the common lumen and the needle lumen. 
     Alternatively or additionally to any of the embodiments above, the deflectable member includes a spring ribbon wire. 
     Alternatively or additionally to any of the embodiments above, the deflectable member includes a one-way valve. 
     Alternatively or additionally to any of the embodiments above, the deflectable member is biased to be in the first configuration. 
     Alternatively or additionally to any of the embodiments above, further comprising a trapper balloon disposed within the guidewire lumen and wherein the shaft defines a third lumen in fluid communication with the trapper balloon. 
     Alternatively or additionally to any of the embodiments above, the shaft defines a fourth lumen and wherein a shapeable member is disposed within the fourth lumen. 
     Alternatively or additionally to any of the embodiments above, further comprising a compliant balloon coupled to the distal end region of the shaft and wherein the shaft defines a fifth lumen in fluid communication with the compliant balloon. 
     A method for medical treatment is disclosed. The method comprises: advancing a medical device into body lumen, wherein the medical device comprises: an elongate shaft having a proximal end region and a distal end region, a first lumen defined in the shaft, a second lumen defined in the shaft, wherein the distal end region includes a common lumen region in fluid communication with the first lumen and the second lumen, and a deflectable member disposed within the shaft; wherein a needle is disposed in the second lumen, passes through the common lumen region, and extends distally beyond a distal end of the shaft; proximally retracting the needle into the second lumen; wherein proximally retracting the needle shifts the deflectable member from an open configuration to a closed configuration; and extending a guidewire between the first lumen and the common lumen region. 
     The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The Figures, and Detailed Description, which follow, more particularly exemplify these embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure may be more completely understood in consideration of the following detailed description in connection with the accompanying drawings, in which: 
         FIG.  1    is a partial cross-sectional side view of an example medical device. 
         FIG.  2    is a partial cross-sectional side view of an example medical device. 
         FIG.  3 A  is a partial cross-sectional side view of an example medical device. 
         FIG.  3 B  is a partial cross-sectional side view of an example medical device. 
         FIGS.  4 A- 4 B  are partially cut away side view of a portion of an example medical device. 
         FIGS.  5 A- 5 B  are partially cut away side view of a portion of an example medical device. 
         FIGS.  6 A- 6 B  are partially cut away side view of a portion of an example medical device. 
         FIGS.  7 A- 7 B  are partially cut away side view of a portion of an example medical device. 
         FIGS.  8 A- 8 B  are partially cut away side view of a portion of an example medical device. 
         FIGS.  9 A- 9 B  are partially cut away side view of a portion of an example medical device. 
         FIG.  10    is a partial cross-sectional side view of an example medical device. 
         FIG.  11    is a cross-sectional view taken through line  11 - 11  in  FIG.  10   . 
         FIG.  12    is a partial cross-sectional side view of an example medical device. 
     
    
    
     While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure. 
     DETAILED DESCRIPTION 
     For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification. 
     All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (e.g., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure. 
     The recitation of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). 
     As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. 
     It is noted that references in the specification to “an embodiment”, “some embodiments”, “other embodiments”, etc., indicate that the embodiment described may include one or more particular features, structures, and/or characteristics. However, such recitations do not necessarily mean that all embodiments include the particular features, structures, and/or characteristics. Additionally, when particular features, structures, and/or characteristics are described in connection with one embodiment, it should be understood that such features, structures, and/or characteristics may also be used connection with other embodiments whether or not explicitly described unless clearly stated to the contrary. 
     The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention. 
     A number of medical devices may be used in various medical interventions. Some of these interventions may include providing access to the vascular system, providing access to various chambers of the heart, septal crossings, and the like. Typical, such interventions may involve a number of steps such wire/needle exchanges. Disclosed herein are medical devices that may be used for number of different interventions, may help reduce or simplify an intervention (e.g., by reducing or eliminating steps such as wire/needle exchanges), and the like as well as methods for using such devices. 
       FIG.  1    is a partial cross-sectional view that schematically depicts an example medical device  10 . In this example, the medical device  10  may be considered to be a catheter or dilator. The medical device  10  may include an elongate shaft  12  having a proximal end region  14  and a distal end region  16 . One or more lumens may be defined in the shaft  12 . For example, the shaft  12  may define a first lumen  18  and a second lumen  20 . A common lumen region  21  may be defined in the shaft  12  where the first lumen  18  and the second lumen  20  merge. The common lumen  21  may be in fluid communication with both the first lumen  18  and the second lumen  20 . 
     A deflectable member  22  may be disposed within the shaft  12 . The deflectable member  22  may be coupled to the shaft  12  in a number of different ways. For example, the deflectable member  22  may extend along a portion of the first lumen  18 , may extend along a portion of the second lumen  20 , may be attached to an internal region of the shaft  12 , may be embedded in a portion of the shaft  12 , or the like. In general, the deflectable member  22  may be designed to direct a device passing through the elongate shaft  12  into one of the first lumen  18  and/or the second lumen  20 . For example,  FIGS.  2 - 3    illustrate the function of the deflectable member  22 . For example, a first medical device  26  may be disposed in the first lumen  18 . In some instances, the first medical device  26  may take the form of a guidewire. A second medical device  24  may be disposed in the second lumen  20 . In some instances, the second medical device  24  may take the form of a needle or trocar. 
     The deflectable member  22  may be designed to shift between a first configuration (e.g., as shown in  FIG.  2   ) and a second configuration (e.g., as shown in FIG.  3 A). When the deflectable member  22  is in the first configuration, at least a portion of the deflectable member  22  may obstruct, block, or cover at least a portion of the second lumen  20 . This may be desirable for a number of reasons. For example, the deflectable member  22  may help to direct a device (e.g., such as the guidewire  26 ) to enter into the desired lumen (e.g., the first lumen  18 ) when the guidewire  26  is backloaded into the shaft  12 . For example, when the deflectable member  22  is in the first configuration, the deflectable member  22  may direct the guidewire  26  (e.g., which may be disposed within the common lumen region  21 ) into the first lumen  18 . When the deflectable member  22  is in the second configuration, the deflectable member  22  may allow the needle  24  to move between the common lumen region  21  and the second lumen  20 . In addition, the deflectable member  22  may also limit distal migration of the needle  24  within the second lumen  20 , which may help to contain the relatively sharp point of the needle  24  within the shaft  12 . Other desirable benefits are contemplated. 
     While the deflectable member  22  may be capable of shifting between configurations, in at least some instance the deflectable member  22  is biased to be in the first configuration. For the purposes of this disclosure, being “biased” may be understood to mean that the deflectable member  22  in its native state or in a state when not subjected to forces that would be capable of shifting the deflectable member  22 , the deflectable member  22  is in the first configuration. In order to have this bias, the deflectable member  22  may be elastically deformable/deflectable between the first configuration and the second configuration. This may include forming at least a portion of the deflectable member  22  out of an elastic material, a super-elastic and/or shape memory material, combinations thereof, or the like. 
     The deflectable member  22  may shift to the second configuration when subject to a force. For example, the needle  24  may be advanced distally into contact with the deflectable member  22  and cause the deflectable member  22  to move or “open” the second lumen  20  (e.g., as shown in  FIG.  3 A ). When the needle  24  is proximally retracted, the deflectable member  22  may shift back to the first configuration (e.g., as shown in  FIG.  2   ). 
     In other instances, rather than the deflectable member  22  being deflectable, the deflectable member  22  may be replaced by a septum member  22 ′ that makes up part of a medical device  10 ′ similar to other devices disclosed herein. The septum member  22 ′ may extend across the second lumen  20  and be secured to the wall of the shaft  12 . Advancing the needle  24  may include advancing the needle  24  through the septum member  22 ′. 
     In some instances, the shaft  12  may include additional features. For example, an interior portion of the shaft  12  (e.g., a wall surface along the first lumen  18 , the second lumen  20 , or both) may have a ridge or ledge  30  that can engage a flange region  28  on the needle  24 . This may limit how far the needle  24  can distally migrate within the shaft  12 . Because of the shape difference in the wall along one or both of the lumen  18 ,  20 , the first lumen  18 , the second lumen  20 , or both may have a variable diameter. In some instances, the first lumen  18 , the second lumen  20 , or both have a substantially constant diameter. 
     In use, the medical device  10  may be used to provide access to a vascular region. For example, the first lumen  18  may contain the guidewire  26  and the second lumen  20  may contain the needle  24 . The needle  24  may be advanced distally to shift the deflectable member  22  to the second configuration (e.g., as shown in  FIG.  3 A ). When doing so, the distal end of the needle  24  may extend out from the end of the shaft  12 . When so arranged, the needle  24  can be used to puncture the skin of a patient and gain access to a vascular region. The medical device  10  (which may function as a dilator) can also be advanced into the vascular region. When the medical device  10  is positioned in the vascular region in the desired manner, the needle  24  can be proximally retracted into the second lumen  20 , thereby allowing the deflectable member  22  to shift to the first configuration (e.g., as shown in  FIG.  2   ). When so arranged, the guidewire  26  can be advanced out from the shaft  12 , into the vascular region, and along the vascular region to a target site. 
     In other used, the medical device  10  (either loaded with the needle  24  or not loaded with the needle  24 ) can be backloaded with the guidewire  26 . In other words, the proximal end of the guidewire  26  can be pushed through the distal end of the shaft  12  and into the first lumen  18 . The deflectable member  22  may help to guide or steer the guidewire  26  into the first lumen  18 . This use may allow the medical device  10  to be loaded with the guidewire  26  either for packaging or as part of preparing the medical device for an intervention. 
     The form, arrangement, and design of the deflectable member  22  may vary.  FIGS.  4 A- 4 B  to  FIGS.  9 A- 9 B  illustrate some of the alternative deflectable members contemplated. For example,  FIG.  4 A  illustrates an example deflectable member  122  disposed within a shaft  112 . In this example, the deflectable member  122  may take the form of a valve or a “squish valve”. The deflectable member  122  may be designed to shift between a first configuration (e.g., as shown in  FIG.  4 A ) and a second configuration (e.g., as shown in  FIG.  4 B ). For example, the deflectable member  122  may be designed to be in the first configuration in a native state and when subjected to forces, the deflectable member  122  may be deform into a flattened second configuration. 
       FIG.  5 A  illustrates an example deflectable member  222  disposed within a shaft  212 . In this example, the deflectable member  222  may take the form of a one-way valve. The deflectable member  222  may be designed to shift between a first configuration (e.g., as shown in  FIG.  5 A ) and a second configuration (e.g., as shown in  FIG.  5 B ).  FIG.  6 A  illustrates an example deflectable member  322  disposed within a shaft  312 . In this example, the deflectable member  322  may take the form of a deflectable valve or arm. The deflectable member  322  may be designed to shift between a first configuration (e.g., as shown in  FIG.  6 A ) and a second configuration (e.g., as shown in  FIG.  6 B ).  FIG.  7 A  illustrates an example deflectable member  422  disposed within a shaft  412 . In this example, the deflectable member  422  may take the form of a collapsible spring wire. The deflectable member  422  may be designed to shift between a first configuration (e.g., as shown in  FIG.  7 A ) and a second configuration (e.g., as shown in  FIG.  7 B ).  FIG.  8 A  illustrates an example deflectable member  522  disposed within a shaft  512 . In this example, the deflectable member  522  may take the form of a coil spring or coil spring wire. The deflectable member  522  may be designed to shift between a first configuration (e.g., as shown in  FIG.  8 A ) and a second configuration (e.g., as shown in  FIG.  8 B ).  FIG.  9 A  illustrates an example deflectable member  622  disposed within a shaft  612 . In this example, an interior portion of the shaft  612  may make up or define the deflectable member  622 . The deflectable member  622  may be designed to shift between a first configuration (e.g., as shown in  FIG.  9 A ) and a second configuration (e.g., as shown in  FIG.  9 B ). 
       FIG.  10    illustrates another example medical device  710  that may be similar in form and function to other medical devices disclosed herein. The medical device  710  may include an elongate shaft  712  having a proximal end region  714  and a distal end region  716 . One or more lumens may be defined in the shaft  712 . For example, the shaft  712  may define a first lumen  718  and a second lumen  720 . A common lumen region  721  may be defined in the shaft  712  where the first lumen  718  and the second lumen  720  merge. A deflectable member  722  may be disposed within the shaft  712 . 
     The medical device  710  may include an expandable member or trapper balloon  732 . The trapper balloon  732  may be disposed within the first lumen  718 , within the second lumen  720 , may span both lumens ( 718 ,  720 ), or both lumens ( 718 ,  720 ) may include a separate trapper balloon  732 . The trapper balloon  732  may be designed to be expanded or otherwise inflated in order to secure a device within a lumen of the shaft  712 . For example, the trapper balloon  732  may be inflated in order to secure a guidewire (e.g., the guidewire  26 ) within the first lumen  718 . Other arrangements are contemplated. It should be understood that the trapper balloon  732  may be used with any of the devices disclosed herein, in combination with any of the deflectable members disclosed herein, and in any of the lumens of the shafts disclosed herein, as appropriate. 
     A distal expandable anchor or balloon  734  may be coupled to the distal end region  716  of the shaft  712 . In at least some instance, the distal balloon  734  may be a compliant balloon that is formed from a relatively soft material such as a silicone material. Other materials are contemplated. The shape of the distal balloon  734  may also vary. For example, in some instance, the distal balloon  734  may be designed to expand to a shape that is substantially spherical. In other instances, the balloon  734  may be designed to expand to a shape that may be described as “dumbbell” or “dog bone” shaped. Other shapes are contemplated. It should be understood that the distal balloon  734  may be used with any of the devices disclosed herein, in combination with any of the deflectable members disclosed herein, and in any of the lumens of the shafts disclosed herein, as appropriate. 
     The distal balloon  734  may provide a number of desirable features. For example, distal balloon  734  may help the medical device  710  navigate or cross portions of the anatomy. For example, the medical device  710  may be used to cross interatrial septum (e.g., at or near the fossa ovalis) and into the left atrium (e.g., in an intervention where access to the left atrium, left atrial appendage, or the like is desired). When doing so, inflating or partially inflating the distal balloon  734  while crossing the septum may help to urge or pull the medical device  710  through septum. Furthermore, after crossing the septum, the distal balloon  734  (e.g., when inflated) may function as an anchor that helps secure the positon of the medical device  710  within the left atrium. 
       FIG.  11    is a cross-sectional view of the shaft  712  about line  11 - 11  in  FIG.  10   . Here it can be seen that a third lumen  736  and/or a fourth lumen  738  may be defined in the shaft  712 . The third lumen  736  may be in fluid communication with either the trapper balloon  732  or the distal balloon  734 . Likewise, the fourth lumen  738  may be in fluid communication with either the trapper balloon  732  or the distal balloon  734 . In some instances, the shaft  712  may also include a fifth lumen  740 . A shaping member  742  may be disposed within the fifth lumen  740 . The shaping member  742  may take the form of an elastically deformable wire or ribbon that is embedded within or otherwise disposed within the fifth lumen  740 . The shaping member  742  allows a user to alter the shape of the shaft  712 . For example, a user may bend the shaft  712  so that it has a curved distal portion, which may help with navigation and or use of the medical device  710 . It should be understood that the shaping member  742  may be used with any of the devices disclosed herein, in combination with any of the deflectable members disclosed herein, and in any of the lumens of the shafts disclosed herein, as appropriate. 
     In other instances, rather than the deflectable member  722  being deflectable, the deflectable member  722  may be replaced by a septum member  722 ′ that makes up part of a medical device  710 ′ similar to other devices disclosed herein. The septum member  722 ′ may extend across the second lumen  20  and be secured to the wall of the shaft  12 . Advancing the needle  24  may include advancing the needle  24  through the septum member  722 ′. 
     The materials that can be used for the various components of the medical device  10  (and/or other medical devices disclosed herein) and the various components thereof may include those commonly associated with medical devices. For simplicity purposes, the following discussion makes reference to the shaft  12  of the medical device  10 . However, this is not intended to limit the devices and methods described herein, as the discussion may be applied to other catheter shaft and/or components of any of the medical devices disclosed herein. 
     The shaft  12  may be made from a metal, metal alloy, polymer (some examples of which are disclosed below), a metal-polymer composite, ceramics, combinations thereof, and the like, or other suitable material. Some examples of suitable polymers may include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, for example, DELRIN® available from DuPont), polyether block ester, polyurethane (for example, Polyurethane 85A), polypropylene (PP), polyvinylchloride (PVC), polyether-ester (for example, ARNITEL® available from DSM Engineering Plastics), ether or ester based copolymers (for example, butylene/poly(alkylene ether) phthalate and/or other polyester elastomers such as HYTREL® available from DuPont), polyamide (for example, DURETHAN® available from Bayer or CRISTAMID® available from Elf Atochem), elastomeric polyamides, block polyamide/ethers, polyether block amide (PEBA, for example available under the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA), silicones, polyethylene (PE), Marlex high-density polyethylene, Marlex low-density polyethylene, linear low density polyethylene (for example REXELL®), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polytrimethylene terephthalate, polyethylene naphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), poly paraphenylene terephthalamide (for example, KEVLAR®), polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMS American Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC), poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS 50A), polycarbonates, ionomers, biocompatible polymers, other suitable materials, or mixtures, combinations, copolymers thereof, polymer/metal composites, and the like. In some embodiments the sheath can be blended with a liquid crystal polymer (LCP). For example, the mixture can contain up to about 6 percent LCP. 
     Some examples of suitable metals and metal alloys include stainless steel, such as 304V, 304L, and 316LV stainless steel; mild steel; nickel-titanium alloy such as linear-elastic and/or super-elastic nitinol; other nickel alloys such as nickel-chromium-molybdenum alloys (e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY® C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys, and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL® 400, NICKELVAC® 400, NICORROS® 400, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 such as HASTELLOY® ALLOY B2®), other nickel-chromium alloys, other nickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-iron alloys, other nickel-copper alloys, other nickel-tungsten or tungsten alloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like); platinum enriched stainless steel; titanium; combinations thereof; and the like; or any other suitable material. 
     In at least some embodiments, portions or all of the shaft  12  may also be doped with, made of, or otherwise include a radiopaque material. Radiopaque materials are understood to be materials capable of producing a relatively bright image on a fluoroscopy screen or another imaging technique during a medical procedure. This relatively bright image aids the user of the shaft  12  in determining its location. Some examples of radiopaque materials can include, but are not limited to, gold, platinum, palladium, tantalum, tungsten alloy, polymer material loaded with a radiopaque filler, and the like. Additionally, other radiopaque marker bands and/or coils may also be incorporated into the design of the shaft  12  to achieve the same result. 
     In some embodiments, a degree of Magnetic Resonance Imaging (Mill) compatibility is imparted into the shaft  12 . For example, the shaft  12 , or portions thereof, may be made of a material that does not substantially distort the image and create substantial artifacts (e.g., gaps in the image). Certain ferromagnetic materials, for example, may not be suitable because they may create artifacts in an MRI image. The shaft  12 , or portions thereof, may also be made from a material that the MRI machine can image. Some materials that exhibit these characteristics include, for example, tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nitinol, and the like, and others. 
     It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the disclosure. This may include, to the extent that it is appropriate, the use of any of the features of one example embodiment being used in other embodiments. The invention&#39;s scope is, of course, defined in the language in which the appended claims are expressed.