Patent Publication Number: US-2022218881-A1

Title: Interventional Medical Devices Useful in Performing Treatment under Magnetic Resonance Imaging and Related Methods

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 63/135,918, filed Jan. 11, 2021. The entire contents of this related application are hereby incorporated by reference into this disclosure. 
    
    
     FIELD 
     The disclosure relates generally to the field of medical devices. More particularly, the disclosure relates to interventional medical devices useful in performing treatment under magnetic resonance imaging (MRI), imaging methods, methods of performing interventional medical treatment under MRI, and methods of making medical devices. 
     BACKGROUND 
     Interventional procedures conducted under MRI have several benefits over X-Ray-guided interventions. For example, the patient is not exposed to ionizing radiation. Also, MRI provides the ability to characterize tissue and fluid flow during an interventional procedure. For at least these reasons, the use of interventional MRI is gaining wider acceptance and the number of procedures that can be performed under MRI is generally increasing. 
     The art provides only a limited number of interventional medical devices suitable for use under MRI, however, which continues to limit growth of the use of interventional MRI procedures. As a result, patients have not yet benefitted fully from interventional MRI technologies and, indeed, are often still limited to less convenient, and potentially less effective, options for certain treatments. 
     For example, without interventional MRI, addressing some conditions requires the use of multiple imaging modalities over the clinical path from initial testing to treatment. On a practical level, this use of multiple imaging modalities can require multiple patient visits to a healthcare facility. A conventional approach to the treatment of prostate cancer is illustrative —visualization, biopsy, and treatment are performed over the course of three separate patient visits. At a first visit, a scan is completed using a magnetic resonance scanner to produce an image showing the prostate and any abnormalities. The patient then leaves the facility and awaits a review of the image. If abnormalities exist, a second patient visit will occur such that a biopsy sample of the abnormal tissue can be completed. Software is used to merge magnetic resonance images with the procedural ultrasound to provide guidance in conducting the biopsy. This fusion decreases the value of the diagnostic magnetic resonance image. The patient then leaves the facility again and awaits a review of the biopsy sample to determine whether further treatment is required (e.g., if the review results in a positive prostate cancer diagnosis). If further treatment is required, the patient must visit the facility a third time for delivery of the treatment. Completion of these three patient visits often extends over months, prevents the patient from receiving rapid treatment, and increases the overall costs associated with treatment, both to the patient and to the healthcare providers involved. Furthermore, the use of software to merge images from multiple imaging modalities, such as magnetic resonance images and ultrasound images, has drawbacks, such as image overlay or alignment issues and the potential for compression shifting of tissues. Ultimately, these drawbacks of current treatment approaches can limit the overall effectiveness of the treatment. Interventional MRI has the potential to overcome these drawbacks by enabling 
     A need exists, therefore, for new and improved interventional medical devices useful in performing treatment under MRI, imaging methods, methods of performing interventional medical treatment under MRI, and methods of making medical devices. 
     BRIEF SUMMARY OF SELECTED EXAMPLES 
     Various example interventional medical devices useful in performing treatment under MRI, imaging methods, methods of performing interventional medical treatment under MRI, and methods of making medical devices are described herein. 
     An example interventional medical device useful in performing treatment under MRI includes a main body that has a central lengthwise axis, a proximal end, a distal end, and an axial length. The main body is formed of a first MRI compatible material. A marker is disposed along the entire axial length of the main body and parallel to the lengthwise axis. The marker is formed of a second MRI compatible material that is different than the first material. 
     Another example interventional medical device useful in performing treatment under MRI includes an elongate tubular member and a plurality of markers. The elongate tubular member has a main body that has a central lengthwise axis, a proximal end, a distal end, an axial length, and defines a proximal opening, a distal opening, and a lumen that extends from the proximal opening to the distal opening. The plurality of markers is disposed along a portion of the axial length of the main body and parallel to the lengthwise axis. Each marker of the plurality of markers is attached to the main body. The elongate tubular member is formed of a first material and each marker of the plurality of markers is formed of a second material that is different than the first material and incorporated into the first material. 
     Another example interventional medical device useful in performing treatment under MRI includes and elongate tubular member and a marker attached to the elongate tubular member. The elongate tubular member has a first main body and a second main body. The first main body has a central lengthwise axis, a proximal end, a distal end, and defines a proximal opening, a distal opening, and a lumen that extends from the proximal opening to the distal opening. The second main body has a central lengthwise axis, a proximal end, a distal end, and defines a proximal opening, a distal opening, and a lumen that extends from the proximal opening of the second main body to the distal opening of the second main body. The marker is disposed along a portion of the axial length of the first main body and parallel to the central lengthwise axis of the first main body. The marker is attached to an external surface of the first main body and is formed of Gadolinium. The second main body is bonded over the external surface of the first main body such that the marker is completely disposed between the first and second main bodies. 
     Another example interventional medical device useful in performing treatment under MRI includes and elongate tubular member and a marker attached to the elongate tubular member. The elongate tubular member has a main body that has a central lengthwise axis, a proximal end, a distal end, and defines a proximal opening, a distal opening, and a lumen that extends from the proximal opening to the distal opening. The main body is formed of 304 Stainless Steel. The marker is disposed along a portion of the axial length of the main body and parallel to the central lengthwise axis of the main body. The marker comprises a portion of the main body that includes dimpling or peening such that individual areas of the main body have been hardened. 
     An example imaging method comprises selecting an interventional medical device that has a main body that has proximal and distal ends and a marker attached to the main body; advancing the distal end of the interventional medical device to a first location within a bodily passage of a patient and until the marker is disposed at a second location within the bodily passage; scanning a portion of the bodily passage that includes the first and second locations within the bodily passage using a magnetic resonance scanner; obtaining a magnetic resonance image of the portion of the bodily passage such that the image includes an artifact indicative of the presence of the marker within the portion of the bodily passage; and withdrawing the interventional medical device from the bodily passage. 
     An example method of performing an interventional medical treatment comprises selecting an interventional medical device having a main body that has proximal and distal ends and a marker attached to the main body; advancing the distal end of the interventional medical device to a first location within a bodily passage of a patient and until the marker is disposed at a second location within the bodily passage; scanning a portion of the bodily passage that includes the second location within the bodily passage using a magnetic resonance scanner; obtaining a magnetic resonance image of the portion of the bodily passage such that the image includes an artifact indicative of the presence of the marker within the portion of the bodily passage; viewing an artifact in the image generated by the presence of the marker; manipulating the interventional medical device based on the location of the artifact relative to the bodily passage; and withdrawing the interventional medical device from the bodily passage. 
     An example method of making a medical device comprises selecting a first material to form an interventional medical device; selecting a second material to form a marker to be included in a portion of the interventional medical device; incorporating the second material into a portion of the first material; and forming the first and second materials into a desired structure to form the interventional medical device. 
     Another example method of making a medical device comprises selecting an interventional medical device precursor that has a main body that has proximal and distal ends; selecting a marker; and attaching the marker to the main body. 
     An example method of performing an interventional medical treatment comprises selecting an interventional medical device having a main body that has proximal and distal ends and a marker attached to the main body; advancing the distal end of the interventional medical device to a first location within a bodily passage of a patient and until the marker is disposed at a second location within the bodily passage; scanning a portion of the bodily passage that includes the second location within the bodily passage using a magnetic resonance scanner; obtaining a magnetic resonance image of the portion of the bodily passage such that the image includes an artifact indicative of the presence of the marker within the portion of the bodily passage; viewing an artifact in the image generated by the presence of the marker; manipulating the interventional medical device based on the location of the artifact relative to the bodily passage; and withdrawing the interventional medical device from the bodily passage. 
     Additional understanding of these example interventional medical devices, imaging methods, methods of performing interventional medical treatment under MRI, and methods of making medical devices can be obtained by review of the detailed description of selected examples, below, and the references drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a first example interventional medical device. 
         FIG. 2  is a perspective view of a second example interventional medical device. 
         FIG. 3  is a perspective view of a third example interventional medical device. 
         FIG. 4  is a perspective view of a fourth example interventional medical device. 
         FIG. 5  is a schematic illustration of an example method of making a medical device. 
         FIG. 6  is a schematic illustration of another example method of making a medical device. 
         FIG. 7  is a partial perspective view of an example system useful in incorporating a marker into a main body of an interventional medical device. 
         FIG. 8  is a partial perspective view of an example marker being attached to an example main body of an interventional medical device. 
         FIG. 9  is a partial perspective view of another example interventional medical device. 
         FIG. 10  is a schematic illustration of an example imaging method. 
         FIG. 11  is a schematic illustration of an example method of performing an interventional medical treatment. 
     
    
    
     DETAILED DESCRIPTION OF SELECTED EXAMPLES 
     The following detailed description and the appended drawings describe and illustrate various example interventional medical devices, imaging methods, methods of performing interventional medical treatment under MRI, and methods of making medical devices. The description and illustration of these examples are provided to enable one skilled in the art to make and use an interventional medical device and to perform imaging methods, methods of performing interventional medical treatment under MRI, and methods of making interventional medical devices. They are not intended to limit the scope of the invention, or its protection, in any manner. The invention is capable of being practiced or carried out in various ways and the examples described and illustrated herein are not considered exhaustive. 
     As used herein, the term “attached” refers to one member being secured to another member such that the members do not completely separate from each other during use performed in accordance with the intended use of an item that includes the members in their attached form. 
     As used herein, the term “circumference” refers to an external enclosing boundary of a body, element, or feature and does not impart any structural configuration on the body, element, or feature. 
     As used herein, the term “marker” refers to a discrete deposit of a first material on a second material such that the first material is visible under MRI and is distinguishable from the second material under MRI, a portion of an interventional device in which a first material has been incorporated into a second material such that the combination of the first and second materials is visible under MRI and is distinguishable from the second material under MRI, and a portion of an interventional device in which a material that forms a portion of an interventional device has been manipulated such that the portion is visible under MRI and is distinguishable from the remainder of the interventional device under MRI. 
     As used herein, the term “passive,” in relation to a marker, refers to a marker that is either unpowered or powered exclusively by the electromagnetic field of a magnetic resonance scanner. 
     As used herein, the term “treatment” refers to a medical procedure performed on or in a portion of a body of a patient. Examples of treatments include delivery of an agent to a site within a body vessel, modification of a local environment inside of a body vessel such as by heating or cooling, and removal of a tissue or portion of a tissue from a site within a body of a patient (i.e., biopsy). 
       FIG. 1  illustrates a first example interventional medical device  10 . In this example, the interventional medical device  10  is a guidewire  12 . 
     The guidewire  12  has a main body  14  that has a central lengthwise axis  15 , a proximal end  16 , a distal end  18 , and an axial length  19 . The axial length  19  extends from the proximal end  16  to the distal end  18 . The guidewire  12  is a flexible member, can comprise any suitable structure, and can be formed of any suitable material. In the illustrated embodiment, the guidewire is an elongate tubular member formed of a polymer and defining an internal lumen. Additional components, such as coils and the like, can be included in the guidewire  12  in conventional manner. 
     In this example, a marker  50  is disposed along the entire axial length  19  of the main body  14  and parallel to the lengthwise axis  15 . The marker  50  comprises a magnetically susceptible material and is disposed on and attached to an external surface of the main body  14 . In some embodiments, the marker  50  is incorporated into the material forming the main body  14 . For example, a ferromagnetic or paramagnetic compound can be incorporated into the material that forms the main body  14  during manufacture and at a desired location on the main body  14 . Examples of materials considered suitable to incorporate into a material that forms a main body  14  include ferromagnetic and paramagnetic compounds, such as those in powder form, Tantalum powder, Barium Sulfate, Bismuth Oxychloride, Tungsten, Iron Oxide nanoparticles, functionalized magnetite, Gadolinium, Stainless Steel, Ferritic Stainless Steel, Ferritic Stainless Steel powders, 316 Stainless Steel, and any other material considered suitable for a particular embodiment. Alternative to incorporating a marker into the material that forms an interventional medical device, alternative embodiments can include a marker disposed on a surface of the main body, such as an internal or external surface. For example, a marker can be printed onto, adhered to, or electroplated onto a surface of a main body forming the interventional medical device, such as an internal or external surface. For example, in embodiments in which an interventional medical device is formed of a metal, an ink containing a magnetically susceptible material, such as an ink containing magnetic particles, an ink containing Iron Oxide nanoparticles, or an ink containing Iron Oxide nanoparticles bound to phospholipids, can be printed onto an external surface or an internal surface of a main body to form a marker. Also alternatively, a tape including a magnetically susceptible material, such as magnetic tape, can be adhered to an external surface or an internal surface of a main body of the interventional medical device. Also alternatively, a magnetically susceptible material can be electroplated onto a surface of a main body of the interventional medical device. Also alternatively, in embodiments in which an interventional medical device is formed of a metal, a portion of the main body of which it is desired to include a marker, can be hardened by cold working the material to increase magnetic susceptibility and create the marker. For example, a marker can be included on a tubular main body formed of a metal (e.g., annealed 304 Stainless Steel) by positioning a hardened wire within the inside diameter of the tubular member and against an internal surface of the tubular member, positioning a roller on an external surface of the tubular member such that it is aligned with the hardened wire, and rolling the roller along the length of the tubular member and along the hardened wire, using the hardened wire as a backing, to harden a portion of the tubular member and create a marker. Work hardening using a roller can also advantageously be performed on markers printed onto or adhered to a surface of the main body, such as an internal or external surface. Alternatively, in embodiments in which an interventional medical device is formed of a metal tubular main body, a portion of the main body of which it is desired to include a marker can include a filler material. For example, in methods of making an interventional medical device described below, a tubular main body is formed by rolling a ribbon of material longitudinally to form a c-shaped intermediate member having opposing portions and a longitudinal void disposed between the opposing portions. Subsequently, a laser is utilized to melt a filler material, such as a magnetically susceptible material, and fill the void between the edges of the opposing portions of the c-shaped main body. 
     While the marker  50  has been described as a material incorporated into the material forming the main body  14  and as extending along the entire axial length  19  of the main body  14 , a marker can comprise any suitable material, in any form, having any suitable configuration, and can be attached to a main body in any suitable manner. Selection of a suitable material for a marker, a suitable configuration for a marker, and of a method or technique to attach a marker to a main body of an interventional medical device can be based on various considerations, including the type of material forming a main body and/or a marker. Examples of various materials considered suitable to form a markers, configurations considered suitable for a marker, and of methods and techniques for attaching a marker to a main body of an interventional medical device are described herein. 
     In this example, a marker extending the entire length of the main body, such as marker  50  in the embodiment illustrated in  FIG. 1 , can be obtained. Alternative lengths can be used, such as a length that is less than fifty percent of the axial length of the main body, a length that is about fifty percent of the axial length of the main body, a length that is more than fifty percent of the axial length of the main body, a length that is less than seventy-five percent of the axial length of the main body, a length that is about seventy-five percent of the axial length of the main body, and a length that is more than seventy-five percent of the axial length of the main body. A length that is more than fifty percent of the axial length of the main body is considered advantageous at least because of the advantageous imaging properties it provides. A length that is equal to the entire axial length of the main body is considered advantageous at least because of the desirable manufacturability it provides. 
     Any suitable number of markers can be included in an interventional medical device according to an embodiment. While the first example interventional medical device includes one marker  50 , an interventional medical device according to a particular embodiment can include any number of markers considered suitable for the intended use of the particular interventional medical device and a skilled artisan will be able to identify a suitable number of markers based on various considerations, including the overall size and configuration of the interventional medical device, the intended use of the interventional medical device, and any desired goals or objectives for visualizing the medical device under MRI. Examples of suitable numbers of markers for inclusion in an interventional medical device according to an embodiment include one marker, two markers, a plurality of markers, three markers, four markers, five markers, six markers, seven markers, eight markers, nine markers, ten markers, more than ten markers, and any other number considered suitable for a particular embodiment. Furthermore, in embodiments that include two or more markers, the markers can be spaced from each other by a desired distance. For example, in an interventional medical device having three markers, the first marker can be spaced from the second marker by a first distance and the second marker can be spaced from the third marker by a second distance. The first and second distances can be the same or can be different. 
       FIG. 2  illustrates a second example interventional medical device  110 . In this example, the interventional medical device  110  is an elongate tubular member  112 . 
     The elongate tubular member  112  has a main body  114  that has a central lengthwise axis  115 , a proximal end  116 , a distal end  118 , an axial length  119 , and defines a proximal opening  120 , a distal opening  122 , and a lumen  124  that extends from the proximal opening  120  to the distal opening  122 . A plurality of markers  150  is disposed along a portion of the axial length  119  of the main body  114  and parallel to the lengthwise axis  115 . Each marker of the plurality of markers  150  is attached to the main body  114 . In the illustrated embodiment, the elongate tubular member  112  is formed of a polymer and each marker  150  of the plurality of markers comprises a material incorporated into the material forming the main body  114 . 
     In the illustrated embodiment, the plurality of markers  150  include a first marker  152 , a second marker  154 , and a third marker  156 . The first marker  152  is spaced from the second marker  154  by a first distance  153  and the second marker  154  is spaced from the third marker  156  by a second distance  155 . The first distance  153  is greater, and different, than the second distance  155 . Each marker of the plurality of markers  150  is parallel to the lengthwise axis  115  of the main body  114 . The first marker  152  and the third marker  156  are disposed along a first axis  157  that is disposed parallel to the lengthwise axis  115  and the second marker  152  is disposed along a second axis  159  that is disposed parallel to the lengthwise axis  115 . The first and second axes  157 ,  159  are offset from one another on the main body  114  relative to the lengthwise axis  115 . 
     The markers  152 ,  154 ,  156  of the plurality of markers  150  can be identical to each other with respect to physical properties, characteristics, and magnetic susceptibility. Alternatively, though, the markers  152 ,  154 ,  156  of the plurality of markers  150  can differ from each other, or from at least one other marker in the plurality of markers, in one or more of their physical properties, characteristics, and magnetic susceptibility. For example, each of the markers  152 ,  154 ,  156  of the plurality of markers  150  can have the same physical dimensions, including length, width, and thickness, and, as a result, the same volume. Alternatively, the markers  152 ,  154 ,  156  of the plurality of markers  150  can differ from each other, or from at least one other marker in the plurality of markers, in one or more of their physical properties, characteristics, and magnetic susceptibility. For example, discrete markers having different physical dimensions can be used in a plurality of markers in an embodiment. Also, discrete markers having different geometries can be used in a plurality of markers in an embodiment. Also, discrete markers having different magnetic susceptibilities can be used in a plurality of markers in an embodiment. For example, markers in a plurality of markers can be subjected to different degrees of work hardening to provide different magnetic susceptibilities to the markers. This is considered advantageous at least because it provides an ability to distinguish the markers of a plurality of markers in an interventional medical device when used under MRI. 
       FIG. 3  illustrates a third example interventional medical device  210 . In this example, the interventional medical device  210  is an elongate tubular member  212 . 
     The elongate tubular member  212  has a first main body  214  and a second main body  230 . The first main body  214  has a central lengthwise axis  215 , a proximal end  216 , a distal end  218 , and defines a proximal opening  220 , a distal opening  222 , and a lumen  224  that extends from the proximal opening  220  to the distal opening  222 . The second main body  230  has a central lengthwise axis  232 , a proximal end  234 , a distal end  236 , and defines a proximal opening  238 , a distal opening  240 , and a lumen  242  that extends from the proximal opening  238  to the distal opening  240 . A marker  250  is disposed along a portion of the axial length of the first main body  214  and parallel to the central lengthwise axis  215  of the first main body  214 . The marker  250  is attached to an external surface of the first main body  214 . In the illustrated embodiment, the marker  250  is formed of Gadolinium. Also in this embodiment, the marker  250  comprises an elongate strip of material having an axial length that is greater than half the axial length of the first main body  214 . The marker  250  has an axial length that is greater than three-fourths the axial length of the first main body  214 . The second main body  230  is bonded over the external surface of the first main body  214  such that the marker  250  is shielded from contact with blood or a bodily passages during use. 
       FIG. 4  illustrates a fourth example interventional medical device  310 . In this example, the interventional medical device  310  is an elongate tubular member  312 . 
     The elongate tubular member  312  has a main body  314  that has a central lengthwise axis  315 , a proximal end  316 , a distal end  318 , and defines a proximal opening  320 , a distal opening  322 , and a lumen  324  that extends from the proximal opening  320  to the distal opening  322 . In the illustrated embodiment, the main body  314  is formed of 304 Stainless Steel. A marker  350  is disposed along a portion of the axial length of the main body  314  and parallel to the central lengthwise axis  315  of the main body  314 . In the illustrated embodiment, the marker  350  comprises a portion of the main body  314  that includes dimpling or peening such that individual areas of the main body  314  have been work hardened and, as a whole, result in the marker  350 . A localized section of the main body  314  can be work hardened by cold working the main body axially, such as by using a rotary swaging machine. In an alternative embodiment, an elongate tubular member can comprise first and second tubular members. The first tubular member formed of a first material (e.g., Inconel) is disposed within the second tubular member, which is formed of a second, different material (e.g., 304 Stainless Steel). The second tubular member can include dimpling or peening, as described herein, to provide discrete areas of increased hardness to increase the magnetic susceptibility. 
     The example interventional medical devices described herein are considered advantageous at least because they provide passive trackability of the device during treatment and under MRI. For example, in embodiments in which the interventional medical device has a marker disposed along its entire axial length, the entire device length is visible during use and under MRI. In procedures in which several devices are being used simultaneously during treatment, the interventional medical devices described herein allow for the interventional medical devices to be distinguished from the other devices. Furthermore, the inclusion of a marker along a portion, or the entirety, of the axial length of an interventional medical device, as described herein, provides conspicuity along the length of the device without interfering with the visualization of anatomical features during use. Moreover, since the markers described herein are passive, they eliminate any need to include long conductive structures necessary for functioning of active MR visualization devices, which are complex electronic components that must be connected to the accessory coil ports on the MR scanner. 
     A main body of an interventional medical device can be formed of any suitable material and selection of a suitable material to form a main body of an interventional medical device can be based on various considerations, including the intended use of the interventional medical device. Examples of MRI compatible materials considered suitable to form a main body of an interventional medical device include biocompatible materials, materials that can be made biocompatible, metals, electrically insulating materials, electrically non-conducting materials, non-magnetic materials, shape memory alloys, including nickel-titanium alloys such as Nitinol, stainless steel, including Austenitic stainless steel, stainless steel containing Iron, stainless steel including austenitic nickel-chromium-based alloys (e.g., Inconel, a registered trademark of Special Metals Corporation), 304 Stainless Steel, 316 stainless steel, cobalt chromium, cobalt chromium alloys, titanium, thermoplastics, polymers, PEEK, carbon-filled PEEK, ceramics, magnetized recording wire, polymers, the materials described herein, combinations of the described herein, and any other material considered suitable for a particular embodiment. 
     Any marker included in an interventional medical device, such as those described herein, has properties that produce visual artifacts during MRI procedures in which the interventional medical device is imaged. These visual artifacts can be used to determine placement of the interventional medical device relative to other portions of an MRI image, such as portions of a body vessel into which the interventional medical device has been advanced. An interventional medical device can include any suitable type and number of markers that allow for visualization of the main body in a magnetic resonance image and for device conspicuity without obscuring target tissue during treatment (e.g., biopsy, removal). A marker included in a main body of an interventional medical device can be attached to the main body using any suitable technique and be formed of any suitable material. Examples of techniques considered suitable to attach a marker to a main body of an interventional medical device include pressing, welding, using adhesives, including a marker material within the material forming a main body, and any other method or technique considered suitable for a particular embodiment. Examples of materials considered suitable to form a marker include biocompatible materials, materials that can be made biocompatible, MRI compatible materials, magnetically susceptible materials, including paramagnetic and ferromagnetic materials, metals, electrically insulating materials, electrically non-conducting materials, shape memory alloys, including nickel-titanium alloys such as Nitinol, Nickel Iron alloys such as Mu-Metal, stainless steel, including Austenitic stainless steel, stainless steel containing Iron, stainless steel including Inconel, cobalt chromium, cobalt chromium alloys, Inconel, titanium, ferromagnetic passive materials, ferromagnetic or paramagnetic compounds, such as those in powder form, Tantalum powder, Barium Sulfate, Bismuth Oxychloride, Tungsten, Iron Oxide nanoparticles, functionalized magnetite, Gadolinium, ink, ink containing magnetic particles, ink containing Iron Oxide nanoparticles, ink containing Iron Oxide nanoparticles bound to phospholipids, the materials described herein, combinations of the described herein, and any other material considered suitable for a particular embodiment. Furthermore, a marker can comprise any suitable structure attached to a main body of an interventional medical device or any suitable treatment imparted on a main body of an interventional medical device. For example, a marker can include bands of material, magnetic inks, sputtered magnetite marks of varying shapes and/or configurations, swaging, dimpling and/or peening the material that forms a main body of an interventional medical device (e.g., annealed 304 stainless steel), or a combination of these. Additional examples of markers considered suitable to include in an interventional medical device are described in U.S. patent application Ser. No. 16/454,905, filed on Jun. 27, 2019, which is hereby incorporated by reference in its entirety for the purpose of describing markers considered suitable to include in an interventional medical device. Any marker included in an interventional medical device can be identified by a unique pattern recognized and transformed into a virtual instrument within a program and displayed on a screen. 
     Various imaging methods, methods of performing interventional medical treatment under MRI, and methods of making interventional medical devices are described herein. While the methods described herein are shown and described as a series of acts, it is to be understood and appreciated that the methods are not limited by the order of acts, as some acts may in accordance with these methods may be omitted, occur in the order shown or described, occur in different orders, or occur concurrently with other acts described herein. 
       FIG. 5  is a schematic illustration of an example method  400  of making a medical device. 
     An initial step  402  comprises selecting a first material to form an interventional medical device. Another step  404  comprises selecting a second material to form a marker to be included in a portion of the interventional medical device. Another step  406  comprises incorporating the second material into a portion of the first material. Another step  408  comprises forming the first and second materials into a desired structure to form the interventional medical device. 
     Step  402  of selecting a first material can be accomplished by identifying a material for which it is desirable to form an interventional medical device that includes a marker for purposes of using the interventional medical device with MRI. The first material can comprise any material considered suitable to form an interventional medical device or an elongate member of an interventional medical device, such as those described herein. 
     Step  404  of selecting a second material can be accomplished by identifying a material for which it is desirable to form a marker to be included in an interventional medical device for purposes of using the interventional medical device with MRI. The second material can comprise any magnetically susceptible material considered suitable to form a marker, such as those described herein. 
     Step  406  of incorporating the second material into a portion of the first material can be accomplished using any suitable method or technique of incorporating a second material into a first material such that the second material provides a desired marker for the interventional medical device as described herein. Selection of a suitable method or technique can be based on various considerations, such as the properties of the first material, the second material, or both. For example, step  406  can be accomplished by dispersing a second material, such as a powdered ferromagnetic compound, a powdered paramagnetic compound, Iron oxide nanoparticles, or functionalized magnetite, into a first material, such as a polymer. This approach changes the way in which the compound behaves in a magnetic field and influences the spin of the Hydrogen protons within the vicinity of the compound allowing for conspicuity under MRI. Step  406  is advantageously performed prior to initiation of step  408 . Incorporating the second material into a portion of the first material, by performing step  406 , prior to the final step of the method  400  of making an interventional medical device is considered advantageous at least because it incorporates the material of the marker or markers, the second material, into the first material prior to the final step of the fabrication process for the medical device. 
     A second material can be incorporated into any suitable portion of a first material and selection of a suitable portion of a first material to incorporate a second material can be based on various considerations, including the intended use of the interventional medical device being formed. Examples of portions of a first material considered suitable to incorporate a second material include along an entire axial length but only a portion of a width, along a portion of an axial length and a portion of a width, along a plurality of portions of an axial length, the portions described herein, and any other portion considered suitable for a particular embodiment. 
     As an alternative to step  406  of incorporating the second material into a portion of the first material, the second material can be disposed on the first material, which can include attaching the second material to the first material. For these methods, any suitable method or technique for disposing a material onto another material, and advantageously attaching the first material to the second material, can be used, including adhering, printing, electroplating, and other suitable methods or techniques. 
     Step  406 , and optionally step  404  if additional selecting is required, can be repeated any desirable number of times if it is desired to include multiple markers, such as a plurality of markers, in an interventional medical device. In these examples, an individual instance of each of step  404  and/or  406  can be performed to provide multiple markers that have the same or different physical properties, characteristics, and magnetic susceptibility, as described above. Also in these examples, additional steps can be included to produce a desired difference in one or more the physical properties, characteristics, and magnetic susceptibility of the markers. For example, individual markers can be can be subjected to different types and/or degrees of work hardening to provide different magnetic susceptibilities to the markers. This is considered advantageous at least because it provides an ability to distinguish the markers of a plurality of markers in an interventional medical device when used under MRI. 
     Step  408  of forming the first and second materials into a desired structure to form the interventional medical device can be accomplished using any suitable method or technique of forming the first and second materials into a desired structure. Selection of a suitable method or technique can be based on various considerations, such as the properties of the first and second materials. Examples of methods and techniques considered suitable to form an interventional medical device include casting, injection molding, extruding, and any other method or technique considered suitable for a particular embodiment. 
     The methods described herein are useful in the making of a variety of interventional medical devices and precursors to such interventional medical devices, including guidewires, catheters, needles, sheaths, snares, and other interventional medical devices. 
       FIG. 6  is a schematic illustration of another example method  500  of making a medical device. 
     An initial step  502  comprises selecting an interventional medical device precursor that has a main body that has proximal and distal ends. Another step  504  comprises selecting a marker. Another step  506  comprises attaching the marker to the main body. 
     Step  502  of selecting an interventional medical device precursor can be accomplished by identifying an interventional medical device for which it is desirable to attach a marker for purposes of using the interventional medical device with MRI. The interventional medical device can be any suitable interventional medical device, or a precursor to such an interventional medical device. Examples of suitable interventional medical devices include guidewires, catheters, needles, sheaths, snares, and other suitable interventional medical devices. Also, implantable medical devices, such as stents, frames, valves, filters, occluders, and other devices can be selected in this step. 
     Step  504  of selecting a marker can be accomplished by identifying a material for which it is desirable to form a marker to be included in an interventional medical device for purposes of using the interventional medical device with MRI. The marker can comprise any material and/or structure considered suitable to form a marker, such as those described herein. Alternatively, step  504  can be accomplished by selecting a method or technique of imparting marker properties into a material that forms an interventional medical device precursor. 
     Step  506  of attaching the marker to the main body can be accomplished using any suitable method or technique of attaching a marker to a main body. Selection of a suitable method or technique can be based on various considerations, such as the properties of the interventional medical device precursor and/or the marker. For example, step  506  can be accomplished as described herein, by printing the marker (e.g., magnetic ink, magnetic ink containing magnetic particles) onto a surface of the main body, such as an external or internal surface, applying the marker (e.g., formed of Gadolinium) to a surface of the main body, such as an external or internal surface, and/or welding the marker to the main body. In embodiments in which Gadolinium, or other material, is used to form a marker, an optional step comprises attaching a second main body to the first main body such that the marker is completely covered and shielded from contact with a bodily passage and/or blood during use. In some embodiments, additional steps can be included. For example, a step of rolling a ribbon of material, such as Inconel, along a lengthwise axis of the ribbon to form a c-shaped intermediate body can be included. In these methods, a step of melting the material forming the marker (e.g., Inconel, 304 Stainless Steel) using a laser can be included. In these methods, after the step of rolling a ribbon of material and after the step of melting the material forming the marker, a step of disposing the melted material into the void to fill the void between the edges of the c-shaped tubular main body using the melted material is advantageously included. The steps of melting and filling can be performed sequentially but are advantageously performed simultaneously.  FIG. 7  illustrates an example system  610  considered suitable for incorporating a marker into a main body using this method. The system  610  includes a laser beam  612  focused by a focused optic  614 , a wire feed apparatus  616  that feeds a wire  618  of the second material  620  to a void  622  between opposing sides  624 ,  626  of the first material  628 , which has been rolled from a ribbon to a c-shaped body having the void  622  between opposing sides  624 ,  626 . A gas nozzle  630  delivers a shielding gas to the point of interaction between the laser beam  612  and the wire  618 . 
       FIG. 8  illustrates the wire  618  of the second material  620  being melted into longitudinal void  622  between opposing sides  624 ,  626  of the first material  628 , which is being rolled from a ribbon configuration to a c-shaped body having the void  622  between opposing sides  624 ,  626 . In this example, and in other example methods in which a second material is welded or otherwise attached to the first material, the welding or attaching can use another material that includes the second material  620 , or that incorporates the second material, a magnetically susceptible material, during attachment to the first material. 
     In embodiments in which a marker is welded to a tubular main body, additional steps can include rolling a ribbon of the first material longitudinally to form a c-shaped intermediate member having opposing portions and a longitudinal void disposed between the opposing portions, melting the material forming the marker (e.g., a magnetically susceptible materials such as 304 Stainless Steel) such as by using a laser; filling the void between the opposing portions of the c-shaped intermediate member to form a tubular main body; and cold working a portion, or the entirety, of the marker material to increase magnetic susceptibility of the marker in the interventional medical device. The step of cold working a portion, or the entirety, of the marker material can be accomplished, for example, by placing a hardened wire within a lumen defined by the tubular main body and rolling the marker material against the hardened wire. As one example,  FIG. 9  illustrates a marker  602  in which the second material  620  comprises stainless steel that has been disposed in a longitudinal void in a c-shaped intermediate member  630  to form tubular main body  632 . The stainless steel has been work hardened along the length of the marker, such as by rolling or a plug drawn through the lumen  634  of the main body  632 , as described above. 
     In embodiments in which a method or technique is used to impart marker properties into a material that forms an interventional medical device precursor, step  506  can include a suitable work hardening method or technique to harden areas along the length of the interventional medical device of which it is desired to include a marker to increase magnetic susceptibility. Examples of suitable work hardening methods or techniques include swaging, rotary swaging, and dimpling or peening. 
     All methods can include appropriate finishing steps. For example, for methods that result in formation of tubular members, a plug can be passed through the internal lumen of the tubular member to flatten the region of the tubular member that includes the weld. Inclusion of a step of passing a plug through the internal lumen of the tubular member is considered advantageous at least because it removes any inwardly directed material that may have resulted from the weld or attachment process. Furthermore, the step of passing a plug through the internal lumen of the tubular member is considered advantageous because it flattens the portion of the tubular member containing the weld or attachment, which can contribute to the work hardening of this portion of the tubular member. In some example methods in which a ribbon of a first material is rolled into a c-shaped elongate member, a side of the ribbon that becomes disposed in the internal of the resulting c-shaped member can be electroplated, such as with Nickel, before a welding step or attaching step is performed. 
       FIG. 10  is a schematic illustration of an example imaging method  700 . 
     An initial step  702  comprises selecting an interventional medical device having a main body that has proximal and distal ends and a marker attached to the main body. Another step  704  comprises advancing the distal end of the interventional medical device to a first location within a bodily passage of a patient and until the marker is disposed at a second location within the bodily passage. Another step  706  comprises scanning a portion of the bodily passage that includes the first and second locations within the bodily passage using a magnetic resonance scanner. Another step  708  comprises obtaining a magnetic resonance image of the portion of the bodily passage such that the image includes an artifact indicative of the presence of the marker within the portion of the bodily passage. For this step  708 , a single still image can be obtained. Also, and optionally, this step  708  can be repeated any desired number of times to obtain multiple magnetic resonance images that can be grouped as a cine to show motion and/or step  708  can comprise obtaining a live image, such as being completed under live real-time MRI visualization. Another step  710  comprises withdrawing the interventional medical device from the bodily passage. 
     Step  702  of selecting an interventional medical device can be accomplished by selecting any suitable interventional medical device, such as those described herein, or those formed using the methods described herein. A bodily passage can include any suitable portion of a body, including existing bodily passages, bodily lumens, and/or bodily passages created through tissues layers and/or fascia using a device described herein. 
       FIG. 11  is a schematic illustration of an example method  800  of performing an interventional medical treatment. 
     An initial step  802  comprises selecting an interventional medical device having a main body that has proximal and distal ends and a marker attached to the main body. Another step  804  comprises advancing the distal end of the interventional medical device to a first location within a bodily passage of a patient and until the marker is disposed at a second location within the bodily passage. Another step  806  comprises scanning a portion of the bodily passage that includes the second location within the bodily passage using a magnetic resonance scanner. Another step  808  comprises obtaining a magnetic resonance image of the portion of the bodily passage such that the image includes an artifact indicative of the presence of the marker within the portion of the bodily passage. Another step  810  comprises viewing an artifact in the image generated by the presence of the marker. Another step  812  comprises manipulating the interventional medical device based on the location of the artifact relative to the bodily passage. Another step  814  comprises withdrawing the interventional medical device from the bodily passage. 
     Step  812  is performed in a manner that achieves, or that contributes to the achievement of, a desired clinical outcome of the method  800  of performing an interventional medical treatment. As such, the nature of the step  812  of manipulating the interventional medical device will depend on the nature of the interventional medical device and the desired clinical outcome. Examples of suitable actions that can be performed for this step include, but are not limited to, axially advancing the interventional medical device within the bodily passage, rotating the interventional medical device within the bodily passage, radially expanding the interventional medical device within the bodily passage, and axially withdrawing a portion of the interventional medical device to allow another portion of the interventional medical device, or a second medical device associated with the interventional medical device, to radially expand within the bodily passage. In alternative embodiments, step  812  can be omitted from method  800  when manipulation of the interventional medical device is not desired. 
     Any of the steps being performed by a magnetic resonance scanning can be accomplished using any suitable magnetic resonance scanner, such as conventional magnetic resonance scanners, magnetic resonance scanners that utilize 0.55 T fields, 1.5 T fields, 3 T fields, fields between about 0.055 T and 1.5 T, fields less than 1 T, and any other magnetic resonance scanner considered suitable for a particular embodiment. 
     Any of the steps being performed within a bodily passage can be accomplished utilizing any suitable portion of a patient and selection of a suitable portion of a patient to scan can be based on various considerations, including the treatment intended to be performed. Examples of portions of a patient considered suitable include bodily passages disposed within the extremities (e.g., arms, legs), chest, breast, spine, neck, head, abdomen, pelvis, prostate, peri-prostatic structures, tissue surrounding the portions described herein, and/or any other portion of the patient considered suitable for a particular embodiment. 
     Those with ordinary skill in the art will appreciate that various modifications and alternatives for the described and illustrated examples can be developed in light of the overall teachings of the disclosure, and that the various elements and features of one example described and illustrated herein can be combined with various elements and features of another example without departing from the scope of the invention. Accordingly, the particular arrangement of elements and steps disclosed herein have been selected by the inventor(s) simply to describe and illustrate examples of the invention and are not intended to limit the scope of the invention or its protection, which is to be given the full breadth of the appended claims and any and all equivalents thereof.