Abstract:
The present invention involves a magnetic embolization apparatus and method for embolizing an aneurysm of a blood vessel. The magnetic embolization apparatus includes a catheter having a distal portion adapted for insertion within an aneurysm of a blood vessel, a permanent magnet carried by the distal portion of the catheter to internally induce a magnetic field from within the aneurysm to control a magnetic field controllable embolic to embolize the aneurysm, and an electromagnet carried by the distal portion of the catheter to internally induce a magnetic field to control delivery of the magnetic field controllable embolic. The method includes delivering a magnetic-field controllable embolic into an aneurysm, inducing a magnetic field in the aneurysm to control the magnetic-field controllable embolic to embolize the aneurysm with the permanent magnet of the catheter, and controlling the delivery of the magnetic-field controllable embolic into the aneurysm with an electromagnet.

Description:
FIELD OF THE INVENTION 
     The invention relates, in general, to an apparatus and method for forming an occlusion in a mammalian body, and, in particular, to an apparatus and method for controlling a magnetically controllable substance in the embolization of an aneurysm. 
     BACKGROUND 
     Like all parts of the body, the brain is composed of living cells that require a blood supply to provide oxygen and nutrients. A hemorrhage in a blood vessel in the brain or in the space closely surrounding the brain is a common cause of strokes. Hemorrhage refers to bleeding into the brain, usually because of a problem with a blood vessel. The problem is often an aneurysm. 
     An aneurysm is an abnormal bulging outward of blood vessel wall. The wall may smoothly bulge outward in all directions (a fusiform aneurysm) or it may form a sack arising from one wall (a saccular aneurysm). If the aneurysm ruptures, a hemorrhage occurs. This can compress and irritate the surrounding blood vessels, resulting in a reduced supply of oxygen and nutrients to the cells, possibly causing a stroke. 
     Aneurysms can be treated from outside the blood vessel using surgical techniques or from inside the blood vessel using endovascular techniques. Endovascular treatment of an aneurysm is performed using a catheter. X-ray, magnetic resonance imaging (MRI) equipment, or other visualization equipment may be used to view the progress during the procedure. 
     A magnetically directable embolic such as an acrylic, iron-containing glue has been proposed to fill or obliterate aneurysms. The embolic is delivered by means of a catheter and is directed into an aneurysm with an external magnetic field generated by a permanent magnet or electrogmanetic device used for Stereotaxis prcedures such as a prototype device made by Steteotaxis Inc. of St. Louis, Mo. An example of such a device is shown and described in U.S. Pat. No. 6,014,580 to Blume, et al. Excess embolic delivered to the aneurysm could enter the bloodstream and cause serious complications downstream, e.g., stroke. The inventors of the present invention have recognized that a need exists to precisely control embolic delivery at the delivery end of the catheter to prevent excess embolic being delivered to the aneurysm. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention involves a magnetic embolization apparatus for embolizing an aneurysm of a blood vessel. The magnetic embolization apparatus includes a catheter having a distal portion adapted for insertion within an aneurysm of a blood vessel, a permanent magnet carried by the distal portion of the catheter to internally induce a magnetic field from within the aneurysm to control a magnetic field controllable embolic to embolize the aneurysm, and an electromagnet carried by the distal portion of the catheter to internally induce a magnetic field to control delivery of the magnetic field controllable embolic. 
     Implementations of the aspect of the invention described immediately above may include one or more of the following. The permanent magnet is located circumferentially outside or inside the electromagnet. A wall of the catheter includes the permanent magnet. The electromagnet is adapted to induce a magnetic field in a first direction to embolize the aneurysm and in a second direction to counteract the magnetic field of the permanent magnet. 
     An additional aspect of the invention includes a method of embolizing an aneurysm of a blood vessel. The method includes delivering a magnetic-field controllable embolic into an aneurysm, inducing a magnetic field in the aneurysm to control the magnetic-field controllable embolic to embolize the aneurysm, and controlling delivery of the magnetic-field controllable embolic into the aneurysm by actuating an electromagnet adjacent the aneurysm. 
     Implementations of the aspect of the invention described immediately above may include one or more of the following. A catheter includes a distal portion with a permanent magnet and the electromagnet located therein, and the permanent magnet is located circumferentially outside the electromagnet and is used to induce the magnetic field in the aneurysm. A catheter includes a distal portion with a permanent magnet and the electromagnet located therein, and the permanent magnet is located circumferentially inside the electromagnet and is used to induce the magnetic field in the aneurysm. A catheter includes a wall with a permanent magnet located therein and the permanent magnet is used to induce the magnetic field in the aneurysm. 
     The method further includes strengthening the magnetic field induced by the permanent magnet to embolize the aneurysm by actuating the electromagnet, and stopping the delivery of the magnetic-field controllable embolic by reversing polarity in the electromagnet to produce a magnetic field that counteracts the magnetic field of the permanent magnet. 
     A further aspect of the invention involves a method of embolizing an aneurysm of a blood vessel. The method includes delivering a magnetic-field controllable embolic into an aneurysm with a lumen of a catheter, internally inducing a magnetic field from within the aneurysm to control the magnetic-field controllable embolic to embolize the aneurysm with a permanent magnet of the catheter, and counteracting the magnetic field induced by the permanent magnet with a magnetic field induced by an electromagnet to remove the catheter from the aneurysm without removing the embolic. 
     Implementations of the aspect of the invention described immediately above may include one or more of the following. The catheter is a dual-lumen catheter having a first lumen and a second lumen, a guide wire is slidably disposed in the first lumen and carries the permanent magnet, the second lumen is adapted to deliver the magnetic field controllable embolic, and the method further includes delivering the magnetic field controllable embolic into the aneurysm through the second lumen and introducing the permanent magnet of the guide wire into the aneurysm to internally induce the magnetic field from within the aneurysm to control the magnetic-field controllable embolic to embolize the aneurysm. The first lumen is defined by a first lumen wall, and the electromagnet is located in the first lumen wall. The catheter is a dual-lumen catheter having a first lumen and a second lumen, the first lumen carries the permanent magnet, the second lumen is adapted to deliver the magnetic field controllable embolic, and the method further includes delivering the magnetic field controllable embolic into the aneurysm through the second lumen. 
     An additional aspect of the invention involves a magnetic embolization apparatus for embolizing an aneurysm of a blood vessel. The apparatus includes a catheter having a distal portion, a detachable permanent magnetic element and pusher wire carried by the catheter, and an electromagnet carried by the distal portion of the catheter to induce a magnetic field for controlling delivery of the magnetic field controllable embolic. 
     A further aspect of the invention involves a method of embolizing an aneurysm of a blood vessel. The method includes deploying a detachable permanent magnetic element into the aneurysm; delivering a magnetic-field controllable embolic into the aneurysm so that the detachable permanent magnetic element draws the magnetic-field controllable embolic into the aneurysm to embolize the aneurysm; and controlling delivery of the magnetic-field controllable embolic with an electromagnet. 
     Other features and advantages of the invention will be evident from reading the following detailed description, which is intended to illustrate, but not limit, the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings illustrate the design and utility of preferred embodiments of the present invention, in which similar elements are referred to by common reference numerals. 
     FIG. 1 is a side-elevational view of an embodiment of a catheter that may be used with the magnetic embolization apparatus. 
     FIG. 2 is a side-elevational view of a distal portion of the catheter illustrated in FIG. 1 in a blood vessel with an embodiment of the magnetic embolizaton apparatus shown disposed in an aneurysm. 
     FIG. 3 is a side-elevational view of a distal portion of a catheter with an additional embodiment of a magnetic embolization apparatus shown. 
     FIG. 4 is a cross-sectional view of a distal portion of a catheter including a further embodiment of a magnetic embolization apparatus shown. 
     FIG. 5 is a cross-sectional view of a distal portion of a catheter including a still further embodiment of a magnetic embolization apparatus shown. 
     FIG. 6 is a cross-sectional view of a distal portion of a catheter including an additional embodiment of a magnetic embolization apparatus shown disposed in an aneurysm. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIG. 1, an exemplary multi-section catheter  100  that may be used to deliver a magnetic embolization apparatus  105 , which is constructed in accordance with an embodiment of the invention, at a targeted aneurysm  107  (FIG. 2) will now be described. The magnetic embolization apparatus  105  induces a magnetic field in the aneurysm  107  to draw and retain a magnetically controllable embolic in the aneurysm  107  and controls delivery of the embolic so that excess embolic is not delivered to the aneurysm  107 . Although the invention will be described in terms of aneurysm treatment, it may also be adaptable for endovascular occlusion in arteries, veins, vascular malformations, and arteriovenous fistulas. The invention may also be used for forming an occlusion in other areas of a mammalian body. 
     The catheter  100  includes a distal section  110 , an intermediate section  120 , and a proximal section  130 . The sections decrease in flexibility from the proximal section  130  to the distal section  110 . 
     The distal section or portion  110  is very flexible and soft to allow deep penetration into the extraordinary convolutions of the neurological vasculature without trauma. The magnetic embolization apparatus  105  is located in the distal section  110  of the catheter  100  at a distal end  135 . The distal section  110  may include one or more radio-opaque bands or markers  140  to allow viewing of the position of the distal section under fluoroscopy. 
     A luer assembly  150  at the proximal section  130  of the catheter  100  accomodates a pusher, core, or guide wire  160 . The wire  160  may be made of any well-known guide wire material in the art such as stainless steel. The luer assembly  150  may also include a fluid port  165  for connecting a fluid supply for introducing and/or removing a magnetically controllable embolic and a power port  170  for connecting the catheter  100  to a power supply. The catheter  100  may also include any well-known steering assembly in the art for delivering the magnetic embolization apparatus  105  to the targeted aneurysm  107 . 
     With reference to FIG. 2, an embodiment of the magnetic embolization apparatus  105  will now be described. The apparatus  105  includes a coiled solenoid or induction electromagnet  210  located in a wall  215  of the catheter body, in the distal portion  110  of the catheter  100 . Electrical current may be supplied to the electromagnet  210  by a power source  220  via a lead wire  230  and returned by a return wire  240  to induce a first magnetic field. Polarity through the electromagnet  210  may be reversed to induce a second magnetic field in an opposite direction from the first magnetic field. A ferrous filling layer or permanent magnet layer  260  may be located in the catheter wall  215 , in the distal portion  110  of the catheter  100 . The layer  260  may be used to help generate a stronger magnetic field at the end of the catheter  100  and/or help reverse the magnetic field to remove the catheter  100  at the end of the procedure. A lumen  270  defined by an inner portion of the wall  215  delivers a magnetically controllable liquid embolic to the aneurysm  107  and may slidably receive the wire  160  for delivering the catheter  100  to the targeted aneurysm site. 
     The magnetic embolization apparatus  105  will now be described in use. The catheter  100  is introduced into the vasculature of a patient via a cannula or introducer sheath and snaked through the vasculature of the patient to the targeted aneurysm  107  by any well-known method in the art. X-ray, fluoroscopy or other well-known visualization techniques may be used to assist the physician in directing the catheter  100  to the targeted aneurysm  107 . The catheter  100  may be introduced over the guide wire  106  to facilitate delivery of the catheter  100  to the targeted aneurysm  107 . The distal end  135  of the catheter  100  may be positioned at the aneurysm site adjacent a neck  280  of the aneurysm  107 , at the neck  280  of the aneurysm  107 , or within the aneurysm  107 . Preferably, the distal end  135  of the catheter  100  is positioned into the aneurysm  107 , near a dome  290  of the aneurysm  107 . 
     An external magnetic field  300  may be induced through the aneurysm  107  by an external machine such as a Stereotaxis machine. 
     Next, a magnetically controllable embolic such as a ferrous polymer (e.g., acrylic, iron-containing glue) that hardens over time is delivered to the aneurysm  107  via the lumen  270  of the catheter  100 . In an alternative embodiment, the embolic may have a different composition. The external magnetic field lines  300  cause the iron-containing embolic to fill the aneurysm  107  and be retained within the aneurysm. 
     Once the aneurysm  107  is filled a sufficient amount, the electromagnet  210  may be actuated, inducing magnetic field lines  310  in generally the opposite direction of the external magnetic field lines  300 , to stop further delivery of the ferrous polymer into the aneurysm  107 . The electromagnet  210  is actuated by supplying current by the power source  220  through the lead wire  230  to the electromagnet  210 . The ferrous filling layer or permanent magnet layer  260  may help in inducing the magnetic field  310  for preventing further delivery of the ferrous polymer to the aneurysm  107 . The electromagnet  210  helps to provide precise control of the delivery of the magnetically controllably embolic to the aneurysm  107 . The strength of the magnetic field induced by the electromagnet  210  may be controlled by varying the power supplied to the electromagnet  210 . It is important that too much embolic does not get delivered to the aneurysm  107  because excess embolic can cause serious complications downstream, e.g., stroke. Controlling embolic shut off with the the electromagnet  210  at the distal portion  110  of the catheter  100  is more precise than controlling shut off at the supply end of the catheter  100  because of the additional volume of the embolic in the catheter lumen  270  that must be accounted for when controlling fluid delivery at the supply end. The electromagnet  210  may also be used to retrieve cured magnetically controllable embolic that may have escaped the aneurysm  107 . 
     After the electromagnet  210  is actuated, the catheter may be withdrawn from the aneurysm  107  and removed from the body. The Stereotaxis machine may be shut off and the external magnetic field  300  terminated after the embolic has hardened or polymerized a sufficient amount. 
     Alternatively or additionally, the electromagnet  210  and/or ferrous filling layer or permanent magnet layer  260  may be used to help generate a strong magnetic field  315  at the end of the catheter  100  for drawing the embolic into the aneurysm  107 . This may be done in addition to or instead of the external magnetic fields  300  generated by the Stereotaxis machine. When the aneurysm  107  has been filled a sufficient amount, the polarity of the electromagnet  210  may be reversed to inhibit further delivery of the embolic. 
     With reference to FIG.3, a magnetic embolization apparatus  350  constructed in accordance with an additional embodiment of the invention and method of use are the same as that described above with respect to FIG. 2 for the magnetic embolization apparatus  105 , except the electromagnet  210  is located circumferentially inside of the ferrous filling layer or permanent magnet layer  260  in the catheter wall  215 . Locating the electromagnet  210  circumferentially inside of the ferrous filling layer or permanent magnet layer  260  helps to enable a stronger magnetic field and, thus, higher force in the aneurysm  107  to hold the embolic in place. 
     With reference to FIG. 4, a magnetic embolization apparatus  400  constructed in accordance with another embodiment of the invention will now be described. The apparatus  400  is part of a dual-lumen catheter  410  having a first lumen  420  defined by a first lumen wall  430  and a second lumen  440  defined by a second lumen wall  450 . The apparatus  400  includes a coiled solenoid or induction electromagnet  460  located in the first lumen wall  430 , in a distal portion  470  of the catheter  410 . A guide wire  480  may be slidably disposed within the first lumen  420 . At least a distal portion  490  of the guide wire  480  includes a ferrous portion or permanent magnet  500 . Ferrous polymer is delivered to the aneurysm site through the second lumen  440 . 
     In use, the magnetic embolization apparatus  400  is snaked through the patient&#39;s vasculature to the targeted aneurysm site. The ferrous polymer is delivered to the aneurysm  107  through the second lumen  440 . Magnetic field lines  510  induced from the ferrous portion or permanent magnet  500  cause the ferrous polymer to be drawn into and retained within the aneurysm  107 . The ferrous portion or permanent magnet  500  may be maintained within the distal portion  470  of the catheter  410  or may be deployed from the catheter  410 , into the aneurysm  107 . To remove the catheter  410  from the aneurysm  107 , the solenoid  460  may be actuated to overcome, counteract, or cancel out the magnetic field  510  of the ferrous portion or permanent magnet  500 . 
     In an alternative embodiment, the solenoid  460  may be actuated to create, in conjunction with the magnetic field  510  induced from the ferrous portion or permanent magnet  500 , a strong magnetic field for drawing and retaining the ferrous polymer in the aneurysm  107 . To remove the catheter  410  from the aneurysm  107 , the polarity through the solenoid  460  may be reversed to overcome, counteract, or cancel out the magnetic field of the ferrous portion or permanent magnet  500 . 
     With reference to FIG. 5, a magnetic embolization apparatus  600  constructed in accordance with a further embodiment of the invention will now be described. The magnetic embolization apparatus  600  is similar to the magnetic embolization apparatus  400  described above, except the guide wire  480  is replaced with a ferrous portion or permanent magnet  610 . A plug  620  may be located at a distal end  630  of the first lumen  420  to prevent the ferrous polymer from entering the first lumen  420 . 
     The method of use for the magnetic embolization apparatus  600  is the same as that described above with respect to the magnetic embolization apparatus  400 , except the ferrous portion or permanent magnet  610  of the apparatus  600  can not be deployed into the aneurysm  107  apart from the catheter  410 . 
     With reference to FIG. 6, a magnetic embolization apparatus  700  constructed in accordance with a further embodiment of the invention will now be described. The magnetic embolization apparatus  700  is similar to the magnetic embolization apparatus  105  described above with respect to FIG. 2, except the apparatus  700  also includes a detachable permanent magnetic element  710  detachably connected to a pusher, guide, or core wire  720  by a detachment mechanism  730 . The element  710  includes one or more permanent Neodynium (NdFeB) or Samarium Cobalt (SmCo) magnets  740 . The element  710  is shaped to retain or secure itself within the aneurysm  107 . In the embodiment shown, the element is a multi-loop assembly  750  made of a shape memory material such as Nitinol™. The multi-loop assembly  750  may be a modified TriSpan™ coil sold by Target Therapeutics® of Freemont, Calif. The multi-loop assembly  750  preferably includes three wire wings or loops, a first wire loop  760 , a second wire loop  770 , and a third wire loop  780 . Although the assembly  750  is shown as having three wire loops, other numbers of loops may be used. The expanded wings or loops  760 ,  770 ,  780  of the multi-loop assembly  750  help to secure the element  710  in the aneurysm  107  once the assembly  750  is deployed in the aneurysm  107 . 
     The detachment mechanism  730  may be a mechanical detachment mechanism such as that described in U.S. Pat. No. 5,250,071 (“the &#39;71 patent”) to Palermo or an electrolytic detachment mechanism such as those described in U.S. Pat. No. 5,122,136 (“the &#39;136 patent”) to Guglielmi, et al. and U.S. Pat. No. 6,123,714 (“the &#39;714 patent) to Gia, et al. The &#39;71, &#39;136, and &#39;714 patents are incorporated by reference as though set forth in full. Preferably, an electrolytic detachment mechanism similar to those described in the &#39;136 patent or the &#39;714 patent is used. An electrolytic detachment mechanism includes an electrolytic, sacrificial joint that separates when a small electric current is applied therethrough. The &#39;136 patent describes a soldered electrolytic, sacrificial joint and the &#39;714 patent describes a solderless electrolytic, sacrificial joint. 
     Although the detachable magnetic element  710  has been described as having a multi-loop configuration, in alternative embodiments, the element  710  may include other configurations. Further, the detachable magnetic element  710  may come in a variety of sizes to accommodate different size aneurysms and/or a variety of configurations to accomodate aneurysms having different shapes. 
     In use, once the distal end  135  of the catheter  100  is delivered to the aneurysm  107 , the detachable permanent magnetic element  710  may be deployed within the aneurysm  107 . This may be accomplished by advancing the pusher wire  720  distally through the lumen  270  of the catheter  100 . Preferably, the magnetic element  710  has a pre-shaped memory so that the magnetic element  710  will automatically deploy into the configuration shown in FIG. 6 when the magnetic element  710  is advanced into the aneurysm  107 . In an alternative embodiment, the catheter  100  may include a sheath that is retracted to deploy the element  710 . The wire loops  760 ,  770 ,  780  hold the magnetic element  710  securely within the aneurysm  107 . 
     Next, the magnetically controllable embolic is delivered to the aneurysm  107  via the catheter  100 . The one or more permanent magnets  740  of the magnetic element  710  internally attracts, from within the aneurysm  107 , the magnetically controllable embolic to the magnet(s)  740 , filling the aneurysm  107 . The magnetic element  710  may be detached from the wire  720  using the detachment mechanism  730  before or after the embolic is delivered to the aneurysm  107 . Further, if the magnetic element  710  is detached from the wire  720  after the embolic is delivered to the aneurysm  107 , the magnetic element  710  may be detached from the wire  720  after the embolic has sufficiently hardened or polymerized in the aneurysm  107 . 
     Once the aneurysm  107  is filled a sufficient amount, the electromagnet  210  may be actuated, inducing magnetic field lines  310  in the general direction shown in FIG. 6, to stop further delivery of the ferrous polymer into the aneurysm  107 . The ferrous filling layer or permanent magnet layer  260  may help in inducing the magnetic field  310  for preventing further delivery of the ferrous polymer to the aneurysm  107 . In an alternative embodiment, as illustrated in FIG. 3, the position of the electromagnet  210  and permanent magnet layer  260  may be switched. In a further embodiment, the apparatus  700  may not include a permanent magnet layer  260 . 
     After the electromagnet  210  is actuated, the catheter may be withdrawn from the aneurysm  107  and removed from the body. 
     Thus, the embodiment of the magnetic embolization apparatus  700  illustrated in FIG. 6 replaces the Stereotaxis machine and the external magnetic field provided therefrom (may also replace the permanent magnet layer  260 ) with a detachable permanent magnetic element  710  that internally induces, from within the aneurysm  107 , a magnetic field to draw the magnetically controllable embolic into the aneurysm for embolization purposes. It should be noted, the detachable permanent magnetic element  710  may also be used with a magnetic embolization apparatus embodiments other than that illustrated in FIG. 6 such as, but not limited to, those illustrated in FIGS. 3-5. 
     While embodiments and applications of this invention have been shown and described, it would be apparent to those in the field that many more modifications are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the appended claims.