WO2011005955A2

WO2011005955A2 - Magnetic stent and method of use

Info

Publication number: WO2011005955A2
Application number: PCT/US2010/041362
Authority: WO
Inventors: John Mcweeney
Original assignee: Boston Endoscopic Engineering Corp.
Priority date: 2009-07-08
Filing date: 2010-07-08
Publication date: 2011-01-13
Also published as: EP2451409A2; WO2011005955A3

Abstract

Stents and methods of inserting and removing a stent from an orifice within a body of a patient are disclosed. The stent includes an elongated shaft and a first end portion that includes a first magnet member. The first end position of the stent is disposed within an opening of the orifice. The position of the stent may be manipulated via the use of a second magnet member for generating a magnetic field between the first magnet member and the second magnet member.

Description

MAGNETIC STENT AND METHOD OF USE

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority to U.S. Provisional Patent Application Serial No. 61/223,897, filed in the United States Patent and Trademark Office on July 8, 2009, the entire contents of which is incorporated herein by reference.

TECHNICAL FIELD

The invention relates to stents for maintaining a body passageway open, and more particularly, to minimally invasive stents and methods for delivering stents into a human body.

BACKGROUND INFORMATION

A stent is a tube-like structure that is inserted into a natural passage in the human body to correct or prevent any obstruction. One type of stent is known as a coronary stent, which may be inserted into a partially-blocked artery during angioplasty in order to widen the artery and promote blood flow.

The use of stents has become increasingly more common in the pancreaticobiliary system. When a biliary or pancreatic duct becomes occluded or requires bypass or prophylactic treatment, although not limited thereto, a removable stent may be inserted at the opening of the duct to promote drainage. Stents for this purpose are commonly made of plastics such polyethylene or Teflon, although not limited thereto, and may include flaps, barbs or some other mechanism at one or both ends to prevent migration of the stent after placement.

Biliary stenting is used to treat obstructions that occur in bile ducts. Bile is a substance that helps to digest fats and is produced by the liver, secreted through the bile ducts, and stored in the gallbladder. It is released into the small intestine after a fat- containing meal has been eaten. The release of bile is controlled by a muscle called the Sphincter of Oddi found at the junction of the bile ducts and the small intestine.

There are a number of conditions, both malignant and benign, that can cause obstruction of the bile duct. Pancreatic cancer is the most common malignant cause, followed by cancers of the gallbladder, bile duct, liver, and large intestine. Noncancerous causes of bile duct obstruction include: injury to the bile ducts caused by gallbladder removal surgery, pancreatitis (inflammation of the pancreas), primary sclerosing cholangitis (an inflammation of the bile ducts that may cause pain, jaundice, itching, or other symptoms), gallstones, radiation therapy, blunt trauma to the abdomen, as well as others.

In order to deal with an obstruction of the bile duct, a stent may be used to promote bile flow. A biliary stent is a thin, tube-like structure that is used to support a narrowed part of the bile duct and prevent the reformation of the obstruction. It may have a larger diameter on one end so that when it is placed at the opening of the bile duct, there is no risk of it sliding entirely into the duct. Stents may be made of plastic or metal, although not limited thereto. Typically the biliary stent is temporary and only needed for two to three days. After that time, if the obstruction has ceased to be a problem, the stent may be removed. However, removal of the stent requires another invasive procedure.

Placing a stent requires an invasive procedure such as endoscopy or traditional surgery. In many cases, a second invasive procedure has to be performed to manipulate the position of the stent, such as when a temporary stent is removed. Manipulation of the stent position requires, at a minimum, an endoscopic procedure, or potentially surgical intervention if the stent has migrated and lodged into the pancreatic or biliary ducts.

Accordingly, there is a need for an improved stent, which can be removed without an endoscopic or surgical intervention, although not limited thereto. There is also a need for a stent that can be captured after it migrates into the biliary or pancreatic ducts, although not limited thereto, without using forceps or snares for retrieval. Due to the confined space of the biliary and pancreatic duct, forceps and snares tend to be ineffective in the removal of the stents.

SUMMARY OF THE INVENTION

The invention relates to minimally invasive stents and methods for delivering stents into a passageway within a human body. A stent according to the invention is less invasive and more manipulatable relative to existing devices and methods for delivering stents into a passageway within a human body. This is accomplished, for example, by stents according to the invention having magnetically attractable portions in communication with magnetic fields acting outside a human body.

In one aspect, the invention relates to a stent that includes an elongated shaft member. The elongated shaft member is configured for placement in an orifice within a body of a patient. The elongated shaft member has a first end portion and defines a lumen that has a diameter. The elongated shaft member also has a retention portion disposed on the first end portion. The retention portion is configured such that the first end portion can be partially coupled to a sidewall of the orifice in order to retain a portion of the elongated shaft member within the orifice. The retention portion has a diameter that is greater than the diameter of the lumen. The retention portion includes a first magnet member and the first magnet member is manipulatable by a second magnet member such that the elongated shaft member can be displaced from the orifice.

In one embodiment according to this aspect of the invention, the orifice can be a biliary duct. The orifice can also be a pancreatic duct. In another embodiment according to this aspect of the invention, the elongated shaft member of the stent can be deflectable. The first end portion of the elongated shaft member can also include a flanged

configuration. The stent can also include a radio-frequency tag disposed within the elongated shaft member as well as include a plurality of magnet members.

The retention portion of the stent can have a substantially J-shaped

configuration. The retention portion can also have a substantially C-shaped

configuration, a substantially O-shaped configuration, or a substantially L-shaped configuration. The diameter of the retention portion of the stent can be greater than a diameter of the first magnet member. The retention portion can also include a self- aligning magnet member. The second magnet member of the stent can be external to the body of the patient. The second magnet member can also be internal to the body of the patient.

In a second aspect, the invention relates to a method of inserting and removing a stent from an orifice within a body of a patient. The method includes providing a stent, such as one of the stents described above, inserting the stent into an orifice within the body of the patient, securing the retention portion of the stent against an opening of the orifice, providing a second magnet member configured to create a magnetic field between the first magnet member of the stent and the second magnet member stent, and manipulating the second magnet member to displace the retention portion of the stent from the opening of the orifice.

In one embodiment according to this aspect of the invention, the orifice can be any one or more of a biliary duct and a pancreatic duct. In another embodiment according to this aspect of the invention, the second magnet member can be external to the body of the patient. In yet another embodiment according to this aspect of the invention, an endoscope can be configured to facilitate the insertion of the stent.

In a third aspect, the invention relates to a method of inserting and removing a stent from an orifice within a body of a patient. The method includes providing a stent, such as one of the stents described above, inserting the stent within an orifice within the body of the patient, securing the retention portion of the stent against an opening of the orifice, providing an external magnet member configured to create a magnetic field between each of the magnet members and the external magnet member, and manipulating the external magnet member to displace the retention portion of the stent from the opening of the orifice.

It is also contemplated that the stent according to the invention can be removed from a patient's vessel or internal lumen without the need for intubation or an invasive procedure requiring sedation. The stent can comprise an elongated, flexible tube with a magnetically attractable end designed for placement into the pancreaticobiliary system. The magnetically attractable (e.g., magnetized) end may be placed outside the biliary or pancreatic duct system, remaining at the opening of the duct and in the lumen of the duodenum (small intestine). A larger diameter or specially-shaped end assures that the stent does not migrate into the duct, although not limited thereto.

The magnetically attractable end of the stent may allow for a magnetic field to be used to manipulate the position of the stent. This may be done by a powerful magnet operating outside of the patient's body, although not limited thereto. For example, to remove the stent, a strong magnetic field may be applied external to the patient to withdraw the stent from the pancreaticobiliary system. The composition of the stent is preferably such that a very strong external magnetic force is required to manipulate its position. This allows the stent to remain in place despite normal environmental magnetic fields. After withdrawal, the stent is designed to pass naturally through the patient's digestive tract. The removal of stents without patient intubation of an endoscope or surgical access will inevitably reduce healthcare costs, patient complications and provide more efficient procedures for both the patient and provider.

The magnetically attractable end of the stent may also allow for non-invasive detection of the stent using ultrasound, X-ray, radio-frequency, or some similar method designed to detect the presence of magnetic fields and/or metal, although not limited thereto. In addition, the design of the stent may include a special shape at one end to prevent migration into the pancreatic or biliary system including, but not limited to, a J- shape, C- shape, or L-Shape. The shaped end can be rendered magnetically attractable by placing magnetic or ferromagnetic materials adjacent to it. The end may have its own magnetic field, or may simply be a metal that this magnetically attractable, allowing a magnetic field to manipulate the position of the stent.

A magnetic tip may also be placed onto a retrieval catheter designed to travel through a patient's digestive system, including the pancreaticobiliary systems. The magnetic tip would be designed to catch the stent with the magnetically attractable end. After withdrawal, the stent may be placed in an endoscope's channel for safe and easy removal.

The stent may also have an identifier of some sort, such as a small LC resonator (e.g., radio frequency tag) that could be detected using radiofrequency, although not limited thereto. Using a unique identifier, the stent can be identified without an invasive procedure. For example, this may be helpful to determine the stent's date of manufacture, type, composition, lot number, and purchaser.

These and other objects, along with advantages and features of the invention herein disclosed, will become apparent through reference to the following description, the accompanying drawings, and the claims. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations. BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the same or similar parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

FIG. IA is a plan view of an embodiment of a stent for maintaining a body passageway open including a first end portion having a substantially O-shaped configuration.

FIG. IB is a plan view of the stent similar to FIG. IA but including a first end portion having a substantially J-shaped configuration.

FIG. 1C is a plan view of the stent similar to FIG. IA but including a first end portion having a flanged configuration.

FIG. 2 A is a cross-sectional view of the stent of FIG. IA including a first magnet member disposed within the first end portion of the stent.

FIG. 2B is a cross-sectional view of another embodiment of the elongated shaft member of the stent of FIG. IA.

FIG. 3 A is a perspective view of a catheter for use with an endoscope to facilitate removal of a stent.

FIG. 3 B is an exploded perspective view of the distal portion of the catheter of FIG. 3A.

FIG. 4 is a schematic illustration of a pancreaticobiliary system within a human body.

FIG. 5 is a schematic illustration depicting an obstruction of a bile duct within a human body.

FIG. 6 is a schematic illustration depicting insertion of a stent near an obstruction in the bile duct within a human body. FIG. 7 is a schematic illustration depicting use of a stent to maintain flow in the bile duct within a human body.

FIG. 8 is a perspective view of the stent of FIG. 3 A having its position manipulated by a magnetic field.

FIG. 9 is a plan view of a method of inserting and removing a stent from an orifice within a body of a patient.

DESCRIPTION

In general, the invention relates to stents, which are less invasive and more manipulative for maintaining a body passageway open.

While the stent according to the invention is described below in various embodiment in terms of a temporary biliary stent, it is not to be interpreted as limited to any particular embodiment. Any form of stent, temporary or otherwise, manufactured of any appropriate material, and for any use, may be used with the invention. Any time where it is beneficial to be able to manipulate the position of a surgical device inside of a patient's body is also a potential use for this method and system.

Referring to FIG. IA, in one embodiment according to the invention, a stent 100 includes an elongated shaft member 102 and a first end portion 104. The elongated shaft member 102 defines a lumen that has a diameter. The elongated shaft member 102 is configured to be placed in an orifice, such as biliary duct, within a body of a patient. The first end portion 104 is configured to act as a retention portion of the stent. For example, the retention portion can be configured such that the first end portion 104 can be partially coupled to a sidewall of an orifice in order to restrain a portion of the stent 100 within the orifice. This functionality permits the stent 100 to be placed at the opening of an orifice, such as the biliary duct, without risk of the stent 100 migrating entirely down the duct.

The first end portion 104 has a substantially O-shaped or ring-shaped

configuration. The first end portion 104 can also have, for example, a substantially J- shaped or L-shaped configuration. The retention portion of the first end portion 104 can have a diameter that is greater than a diameter of the lumen of the elongated shaft member 102. The retention portion of the first end portion 104 can include a first magnet member (FIG 2A). The first magnet member can be manipulatable by a second magnet member such that the stent 100 can be displaced from the orifice.

The first end portion 104 may be manufactured by extruding plastic over material susceptible to a magnetic field, such as magnetized metal, although not limited thereto. Other forms of manufacture are also capable of obtaining the desired effect and any method of affixing a magnet or other material susceptible to magnetic fields is a potential method of manufacturing the stent 100.

Referring to FIG. IB, another embodiment according to the invention is depicted as a stent 110. The stent 110 includes an elongated shaft member 112 and a first end portion 114. The first end portion 114 has a substantially C-shaped configuration. The first end portion 114 has a substantially curved end 116 so that when the stent 110 is placed within an orifice, the stent 110 will not migrate entirely into the orifice. The first end portion 114 may be manufactured with magnetic material or some other material susceptible to magnetic fields, hi operation, stent 110 functions as does the stent 100 of FIG. IA.

Referring to FIG. 1C, another embodiment according to the invention is depicted as a stent 120. The stent 120 includes an elongated shaft member 122 and a first end portion 124. The first end portion 124 includes flanges 126. The flange 126 can have two end portions; however, a greater or lesser number of end portions may also be utilized. The flanges 126 are configured to prevent the stent 120 from migrating so that when the stent 120 is placed within an orifice, the stent 120 will not migrate entirely into the orifice. The flanges 126 may be manufactured with magnetic material or some other material susceptible to magnetic fields. In operation, stent 120 functions as do the stents 100 and 110 of FIGS. IA and IB.

Referring to FIGS. IA- 1C, the stents 100, 110, and 120 may also be composed of an extruded thermoplastic polymeric material which has been compounded with a dispersion of neodymium-iron-boron or samarium cobalt particles. These particles can be dispersed through the elongate shaft members 102, 112, and 122, or may be specifically arranged to reside at the first end portions 104, 114, or 124. The stents 100, 110, and 120 may also be manufactured via the fusion of the elongated shaft members 102, 112, and 122 comprising of tubes manufactured from conventional thermoplastic materials to a second elongate shaft member manufactured from an extrudate

compounded with a dispersion of neodymium-iron-boron or samarium cobalt particles. The second elongated shaft member can be magnetized via the incorporation of permanent magnetic particles to function in conjunction with an externally applied magnetic field source, to remove the magnetic stent embodiment from internal ductal vessels or orifices.

Referring to FIG. 2 A, a cross-sectional view of the stent 100 of FIG. IA is depicted. The first end portion 104 of the retention portion of the stent 100 includes a first magnet member 106. The first magnet member 106 is encapsulated in the wall of the first end portion 104. The wall may be comprised of polymeric materials. One purpose for providing the first magnet member 106 in this configuration is to provide a method to secure the first end portion 104 in position without migrating the stent 100 into an orifice, such as the biliary ductal system, thus allowing the stent 100 to remain in the duodenum.

The materials used for the polymeric portions of the stent 100 can be

manufactured from a thermoplastic polymer such as, but not limited to, polyurethane, polyamide, poly-ether-amide and copolymers thereof, polyvinylacetate and copolymers thereof, silicone and derivatives thereof, Poly-tetra-fluoro-ethylene (PTFE) Styrene butadiene (SBR) and copolymers thereof, or thermoplastic elastomer materials.

Encapsulating the first magnet member 106 in such a fashion, may be achieved via thermal bonding or heat forming of the polymer around the first magnet member 106 or adhesively bonding the first magnet member 106 to the internal surface of a polymeric body of the stent 100.

The first magnet member 106 may be manufactured as a single, annular, permanent magnet and manufactured from rare earth magnetic materials such as neodymium-iron-boron or samarium cobalt. The advantage of these rare earth compounds for application per the invention over other commercially known magnets is that their crystalline structures have very high magnetic anisotropy. This means that a crystal of the material is easy to magnetize in one particular direction, but resists being magnetized in any other direction. Alternately, the first magnet member 106 capsulated in the wall of the first end portion 104 may consist of a number of annular magnetic components, stacked in a cylindrical fashion on top of each other, and encapsulated within the wall of the first end portion 104.

The axis of magnetization of the first magnet member 106 or a plurality of first magnet members 106 may be axial along the longitudinal axis of the first magnet member 106. This would provide the greatest attractive force when removing the first magnet member 106 from an orifice, via the application of an external magnetic field.

Alternately, the axis of magnetization of the first magnet member 106, or the plurality of first magnet members 106 could be diametric, with "North-South" variation along the diameter of the first magnet member 106 or radially arranged with "North" on the inner diameter of the first magnet member 106 and "South" on the outer diameter of the first magnet member 106.

In one embodiment according to the invention, the stent 100 may have the following dimensions. These dimensions are merely exemplary and other dimensions may be contemplated. The outer diameter of the elongated shaft member 102 may vary from 0.010 inches to 0.150 inches, but is preferably in the range of 0.040 inches to 0.115 inches. The outer diameter of the first end portion 104 which encapsulates the first magnet member 106 may vary from 0.060 inches to 0.200 inches, but is preferably in the range of 0.070 inches to 0.150 inches. The outer diameter of the first magnet member 106 may vary from 0.070 inches to 0.150 inches, but is preferably in the range of 0.100 inches to 0.135 inches. The internal diameter of the first magnet member 106 may vary from 0.010 inches to 0.090 inches, but is preferably in the range of 0.040 inches to 0.80 inches. The latter preferred internal diameter dimensions for the first magnet member 106 may also pertain to the internal diameter of the elongated shaft member 102.

Referring to FIG. 2B, a cross-sectional view of another embodiment of the elongated shaft member 102 of the stent 100 of FIG. IA is depicted. The elongated shaft member 102 may be extruded in a star shaped profile. This profile is intended to provide an alternate construction to promote drainage of, for example, the pancreatic and common bile ducts in-situ. With reduced surface contact area with internal ducts afforded by the cross section, the star shaped profile may also provide for reduced friction between the outer surface of the elongated shaft member 102 and intra-ductal lumens of the elongated shaft member 102. This reduced factional force may result in lower stent removal forces, yielding reduced external magnetic force field requirements during stent removal.

Referring to FIGS. 3A and 3B, a catheter 200 can be provided to facilitate stent removal. The catheter 200 includes a shaft 202 and a second magnet member 204. The shaft 202 may be solid or tubular in nature. The second magnet member 204 is incorporated on the external diameter of the shaft 202.

A method of inserting and removing a stent, such as one of the stents of FIGS. IA- 1C, from an orifice within a body of a patient can be accomplished in numerous manners. In one embodiment, the method includes providing a stent, such as one of the stents of FIGS. 1 A-IC, inserting the stent into an orifice within the body of the patient, securing the retention portion of the first end portion of the stent against an opening of the orifice, providing a second magnet member 204 configured to create a magnetic field between the first magnet member, such as the first magnet member 106 of the stent 100, and the second magnet member 204, and manipulating the second magnet member 204 to displace the retention portion of the first end portion of the stent from the opening of the orifice.

Another method of inserting and removing a stent, such as one of the stents of FIGS. 1 A-IC, from an orifice within a body of a patient can also be accomplished in numerous manners. In one embodiment, the method includes providing a stent, such as one of the stents of FIGS. IA- 1C, inserting the stent within an orifice within the body of the patient, securing the retention portion of the first end portion of the stent against an opening of the orifice, providing an external second magnet member 204 configured to create a magnetic field between each of the magnet members, such as the first magnet member 106 of stent 100, and the external second magnet member 204, and manipulating the external magnet member 204 to displace the retention portion of the first end portion of the stent from the opening of the orifice. For example, in operation, to remove an in-vivo biliary or pancreatic stent, as shown in FIGS. 1 A-2B, the catheter 200 is introduced via an endoscope and placed trans- duodenally to the stent location. The attractive forces of the second magnet member 204 provide for a means for temporary coupling the second magnet member 204 and the first magnet member 106 encased in the first end portion of the stent 100. The stent 100 can thus be removed from an orifice as previously described above.

Materials used for constructing the magnetic component of the catheter 202, could be derived from, but are not limited to, neodymium-iron-boron or samarium cobalt and/or derivatives thereof.

Referring to FIG. 4, in one embodiment according to the invention, a stent of the invention may be used within a pancreaticobiliary system 300 of a body of a patient. The system 300 includes a bile duct 302 that runs adjacent to a pancreas 304. Bile is a digestive fluid secreted by the liver and stored in the gallbladder which normally is released into the duodenum 306 portion of the small intestine through the Sphincter of Oddi 308. Bile, released after a meal containing fats, aids in absorption and digestion of the fat.

Referring to FIG. 5, the bile duct 302 may become obstructed, thereby causing biliary obstruction. Biliary obstruction occurs when the bile duct 302, which transports bile from the liver to the small intestine (duodenum 306), is blocked by a stone, tumor, injury, inflammation, or some other obstruction. For example, a pancreatic tumor 308 may press in on the bile duct 302, causing a backup of bile in the gallbladder. Blood tests may indicate a high level of bilirubin, a waste product of the liver, or diagnosis may come from an endoscopic examination. Untreated biliary obstruction may cause life- threatening infection or chronic liver disease.

Referring to FIGS. 6-7, a stent, such as one of the stents of FIGS. IA-C, can be inserted into an orifice, such as the biliary duct 302, which is subject to obstruction due to blockage by a pancreatic tumor 308. One method of relieving a blockage due to the pancreatic tumor 308 is the placement of the stent 100 of FIG. IA into the biliary duct 302. An endoscope 310 (an instrument placed down the throat into the esophagus, through the stomach to the duodenum 306 of the small intestine) may be used to help a physician to see the obstruction and to place the stent 100 in the correct position. The stent 100 may be designed to be inserted over a guide wire pushed by a catheter so that it can be advanced by the physician to the correct location. The physician may then withdraw the guide catheter, which is connected to the catheter pusher, and then remove the guide wire. Dye may be injected and X-ray images may be taken to insure the stent 100 is correctly placed and the flow of bile is restored.

Once the flow of bile is restored, the threat of infection and inflammation is decreased and the stent 100 may then be removed. However, the prognosis may not be significantly altered if the pancreatic carcinoma is otherwise untreatable. Reoccurrence of the blockage (restenosis) may also occur, requiring further surgery or replacement of the stent 100.

Referring to FIG. 8, in one embodiment according to the invention, the position of the stent 100 may be manipulated through the use of a magnetic field. For example, in operation, the stent 100 can be placed within the biliary duct 302. The first end portion 104 of the stent 100 can be placed at the opening of the biliary duct 302 in order to keep bile flowing past a pancreatic tumor 308. When the stent 100 is ready to be removed, a second magnet member 320 or other device that creates a magnetic field may be used to create a magnetic field sufficient to dislodge the stent 100 from the bile duct opening 302. Using a magnetic field generated outside of the body eliminates the need for an invasive and dangerous procedure. Once dislodged, the stent 100 will pass naturally through the patient's digestive tract.

Materials used for constructing the stent 100 could be derived from, but is not limited to, neodymium-iron-boron or samarium cobalt. Such materials would assist in developing the necessary magnetic field. Although not limited thereto, non-magnetic material may be also used, which may be later magnetized in the presence of an electric magnetic field.

Referring to FIG. 9, a second magnet member 320 that is placed external to the body of a patient can be used to remove a stent 100 via the application of an external magnetic field. In one embodiment, the second magnet member 320 is a powerful handheld magnet which is used to apply an external magnetic field to the stent 100 with the first magnet member 106 incorporated therein. The second magnet member 320 may be, but not limited to, a cylindrically shaped permanent magnet, mounted with a handle for easy manipulation external to the patient. The second magnet member 320 may also be an electromagnet. The electromagnet usually is wound around an iron core. However, it could be wound around an air core, in which case it is called a solenoid. When connected to a DC voltage or current source, the electromagnet becomes energized, creating a magnetic field, thereby allowing it to be utilized in a similar fashion to a permanent magnet. The magnetic flux density is proportional to the magnitude of the current flowing in the wire of the electromagnet, while the polarity of the electromagnet is determined by the direction the current. Via manipulation of current direction, such an external second magnet member 320 can be used to extract the in-vivo magnetic stent 100. Once the in-vivo magnetic stent 100 has been removed from the biliary or pancreatic ducts, the external magnetic field is ceased. The stent 100 is then free to fall into the duodenum where it will pass through the digestive system via conventional human excretory function.

The second magnet member 320 may also incorporate an embedded RF transceiver. The RF Transceiver can use RF modules for high speed data transmission. The micro electronic circuits in the digital-RF architecture work at speeds up to 100 GHz. Such a transceiver may be wired to a real-time display (either LED or sound based) which would activate the user once the second magnet member 320 was in the vicinity of the internally placed stent 100. Such transceiver technology (Infineon Technologies, Germany) is well known to peoples skilled in the art.

The second magnet member 320 could also incorporate a Halbach permanent magnet array, whereby the array comprises a wide, flat blanket which is used for magnetic stent retrieval and placed under the patient prior to stent removal. A Halbach array is a special arrangement of magnets that augments the magnetic field on one side of the array while canceling the field to near-zero on the other side. For example, the magnetic field is enhanced on the patient side of the magnetic blanket and canceled on the physician side (a one-sided flux). This would minimize the danger of unforeseen attraction of nearby medical instruments to the second magnet member 320 and facilitate removal of the stent 100 via the inducement of a magnetic field. In various embodiments of the invention, the magnetic attraction between the stent 100 and the second magnet member 320 could be augmented by an ingestible magnetic pill having a simple North-South axis magnetic dipole. In operation, when the magnetic pill passes into at patient's small intestine, the pill would bind to the encased first magnet member 106 of the indwelling biliary or pancreatic stent 100. The mating of the magnetic pill to the magnetic stent 100 would allow for easier capture and retraction of the stent 100 by the second magnet member 320. The removed stent 100, would, as before, be freely allowed to fall into the duodenum for natural digestive tract excretion. Additionally, a stent 100 could also be retrieved with the assistance of a magnet ingested by the patient, although not limited thereto. The ingested magnet may form a connection with the stent 100 in the patient. This may facilitate stent migration and removal of the stent 100 from the pancreaticobiliary system by increasing the downward force (e.g., both gravity and intestinal peristalsis). It is envisioned that these applications may also be applied for facilitating magnetic stent removal in obese patients with excessive abdominal wall soft tissue.

It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as illustrative of some embodiments according to the invention.

Claims

WHAT IS CLAIMED IS:

1. A stent comprising:

an elongated shaft member having a first end portion and defining a lumen, the lumen having a diameter, the elongated shaft member being configured for placement in an orifice within a body of a patient, the elongated shaft member having a retention portion disposed on the first end portion, the retention portion being configured such that the first end portion can be partially coupled to a sidewall of the orifice in order to retain a portion of the elongated shaft member within the orifice, the retention portion having a diameter greater than the diameter of the lumen, the retention portion including a first magnet member, the first magnet member being manipulatable by a second magnet member such that the elongated shaft member can be displaced from the orifice.

2. The stent of claim 1 wherein the orifice is a biliary duct.

3. The stent of claim 1 wherein the orifice is a pancreatic duct.

4. The stent of claim 1 wherein the elongated shaft member is deflectable.

5. The stent of claim 1 wherein the retention portion includes a substantially J- shaped configuration.

6. The stent of claim 1 wherein the retention portion includes a substantially C- shaped configuration.

7. The stent of claim 1 wherein the retention portion includes a substantially L- shaped configuration.

8. The stent of claim 1 wherein the retention portion includes a substantially O- shaped configuration.

9. The stent of claim 1 wherein the first end portion includes a flanged

configuration.

10. The stent of claim 1 further comprising a radio-frequency tag disposed within the elongated shaft member.

11. The stent of claim 1 further comprising a plurality of magnet members.

12. The stent of claim 1 wherein the diameter of the retention portion is greater than a diameter of the first magnet member.

13. The stent of claim 1 wherein the second magnet member is external to the body of the patient.

14. The stent of claim 1 wherein the second magnet member is internal to the body of the patient.

15. The stent of claim 1 wherein the retention portion includes a self-aligning magnet member.

16. A method of inserting and removing a stent from an orifice within a body of a patient comprising:

providing a stent, the stent comprising an elongated shaft member having a first end portion and defining a lumen, the lumen having a diameter, the elongated shaft member being configured for placement in an orifice within a body of a patient, the elongated shaft member having a retention portion disposed on the first end portion, the retention portion being configured such that the first end portion can be partially coupled to a sidewall of the orifice in order to retain a portion of the elongated shaft member within the orifice, the retention portion having a diameter greater than the diameter of the lumen, the retention portion including a first magnet member, the first magnet member being manipulatable by a second magnet member such that the elongated shaft member can be displaced from the orifice;

inserting the stent into the orifice within the body of the patient;

securing the retention portion of the stent against an opening of the orifice;

providing a second magnet member configured to create a magnetic field between the first magnet member and the second magnet member; and

manipulating the second magnet member to displace the retention portion of the stent from the opening of the orifice.

17. The method of claim 16 wherein the orifice is any one or more of a biliary duct and a pancreatic duct.

18. The method of claim 16 wherein the second magnet member is external to the body of the patient.

19. The method of claim 16 further comprising an endoscope configured to facilitate the insertion of the stent.

20. A method of inserting and removing a stent from an orifice within a body of a patient comprising:

providing a stent, the stent comprising an elongated shaft member having a first end portion and defining a lumen, the lumen having a diameter, the elongated shaft member being configured for placement in an orifice within a body of a patient, the elongated shaft member having a retention portion disposed on the first end portion, the retention portion being configured such that the first end portion can be partially coupled to a sidewall of the orifice in order to retain a portion of the elongated shaft member within the orifice, the retention portion having a diameter greater than the diameter of the orifice, the retention portion including a plurality of magnet members, each of the magnet members being manipulatable by an external magnet member such that the elongated shaft member can be displaced from the orifice;

inserting the stent within the orifice within the body of the patient;

securing the retention portion of the stent against an opening of the orifice;

providing the external magnet member configured to create a magnetic field between each of the magnet members and the external magnet member; and

manipulating the external magnet member to displace the retention portion of the stent from the opening of the orifice.