Patent Publication Number: US-2022218354-A1

Title: Embolization devices and methods of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 17/264,441, filed Jan. 29, 2021, which is a National Stage Entry of International Patent Application No. PCT/EP2019/060106, filed Apr. 18, 2019, the details of which are incorporated by reference herein in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure generally relates to embolization devices for promoting clot formation in a bodily lumen. The present disclosure also generally relates to methods of manufacturing embolization devices for promoting clot formation in a bodily lumen. 
     BACKGROUND OF THE DISCLOSURE 
     An embolization device is a permanent or semi-permanent implantable device which may be received within a bodily lumen so as to promote clot formation therein. Such embolization devices may have a contracted delivery configuration and an expanded deployed configuration. The contracted delivery configuration may be such that the device may be loaded into a delivery device, such as a delivery catheter. Various embolization devices are disclosed in WO  2014 / 140325  and WO  2016 / 041961 , both of which are incorporated herein by reference in their entirety. 
     Embolization devices may be deployed in the vasculature at a particular location by a medical practitioner so as to promote clot formation and ultimately occlude the blood vessel. However, typical embolization devices may be prone to migration within the vasculature which may cause serious adverse effects. 
     To reduce migration, some known embolization devices comprise a number of bristles or fibers extending radially outwardly from a central core. The bristles are configured to contact the bodily lumen and anchor the embolization device in the lumen due to friction between the bristles and the wall of the bodily lumen. 
     However, in these known embolization devices, the bristles may become disconnected from the central core which results in a reduction in the anchoring force and therefore increases the chances of migration of the device. 
     In addition to bristles, certain embolization devices further include a flow restrictor which acts to restrict flow in the bodily lumen and may further act to provide an additional anchoring force. In these devices, the flow restrictor is typically a separate membrane which is disposed over the central core of the embolization device. During assembly of the device, the flow restrictor must therefore be manipulated such that it is attached to the central core. However, this may result in an unreliable attachment and deformations or irregularities in the attached flow restrictor. 
     Accordingly, such flow restrictors may not reliably expand to their expanded deployed configuration in the bodily lumen, and, therefore, the additional anchoring force provided by the flow restrictor may not reliably come about when the device is deployed. Again, this increases the chances of migration of the device. 
     In view of the above, there is a need for an improved embolization device which is capable of achieving and maintaining an anchoring force more reliably. There is also a need for an improved method of manufacturing an embolization device which is capable of achieving and maintaining an anchoring force more reliably. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present disclosure, and to show how the same may be carried into effect, reference will be made, by way of example only, to the following drawings, in which: 
         FIG. 1  shows an embolization device in an unconstrained configuration; 
         FIG. 2  shows the embolization device of  FIG. 1  in a contracted delivery configuration within a delivery catheter; 
         FIG. 3  shows the embolization device of  FIGS. 1 and 2  in an expanded deployed configuration in a bodily lumen; 
         FIGS. 4 to 8  each show a cross-section along part of the length of various embodiments of the embolization device; 
         FIGS. 9 and 10  each show a transverse cross-section along the length of certain embodiments of the embolization device; 
         FIGS. 11 to 13  each show a cross-section along part of the length of various embodiments of the embolization device; 
         FIGS. 14 to 16  each show a cross-section along part of the length of various embodiments of the embolization device which comprise a flow restricting membrane; and 
         FIGS. 17 and 18  each show a transverse cross-section along the length of certain embodiments of the embolization device which comprise a flow restricting membrane. 
     
    
    
     DETAILED DESCRIPTION 
     There is provided an embolization device for promoting clot formation in a lumen. The embolization device may have a contracted delivery configuration and an expanded deployed configuration. The embolization device may comprise a stem comprising a tube having a tube wall. The embolization device may comprise a plurality of flexible bristles extending radially outwardly from the tube. At least one of the plurality of flexible bristles may penetrate through the tube wall. 
     Throughout this disclosure, the term ‘embolization device’ may refer to a device which may be permanently or semi-permanently implanted in a bodily lumen. Accordingly, the ‘embolization device’ may be configured to be disposed within the bodily lumen for a period of time, such as a number of days, or disposed in the bodily lumen indefinitely. To this end, the ‘embolization device’ may be configured to be selectively detached from a delivery element so that it may be implanted in the bodily lumen in isolation. 
     Throughout this disclosure, a ‘contracted delivery configuration’ of an element may refer to a configuration of the element which has a smaller radial extent than an ‘expanded deployed configuration’ of the element. 
     Throughout this disclosure, the term ‘tube wall’ may refer to the wall of a tube which extends along the longitudinal axis of the tube. The tube wall may be continuous or discontinuous. 
     Throughout this disclosure, the term ‘tube’ may refer to any element which has a tube wall in which different portions of the tube wall oppose each other across a longitudinal axis. For example, the tube wall may be curved (e.g. having a circular cross-section) around the longitudinal axis of the tube such that opposite sides of the tube wall oppose each other. The tube may or may not have a lumen extending along any portion of its longitudinal axis. 
     The tube wall may have one or more slits extending along part or all of the longitudinal length of the tube. 
     The tube may be an elongate tube. 
     The tube may not comprise a coil. 
     The tube may have a lumen extending along its longitudinal axis. A portion of the at least one of the plurality of flexible bristles that penetrates through the tube wall is disposed in the lumen. 
     The tube may have two or more lumens extending along its longitudinal axis. At least some of the two or more lumens are substantially isolated from one another. At least some of the two or more lumens are spaced apart along the longitudinal axis of the tube. A portion of the at least one of the plurality of flexible bristles is disposed in one of the two or more lumens. 
     The tube may have a smaller radial extent in a portion adjacent to at least one of the two or more lumens than the radial extent of the tube at a portion corresponding to the at least one of the two or more lumens. The portion adjacent to at least one of the two or more lumens may be disposed between two portions of the tube corresponding to two lumens. 
     The portion of the at least one of the plurality of flexible bristles that penetrates through the tube wall substantially fills a lumen of the tube. 
     Throughout this disclosure, as would be understood by the skilled person, the term ‘stem’ refers to an elongate element which extends longitudinally along the length of the embolization device to act as a backbone for the device, and has a significantly smaller radial extent than the further elements of the embolization device (for example, the plurality of flexible bristles). The stem may extend along substantially the whole longitudinal extent of the plurality of flexible bristles (e.g. when the embolization device is in an unrestrained configuration, contracted delivery configuration and/or expanded deployed configuration). The stem may extend along substantially the whole length of the embolization device. 
     In any of the embodiments described herein, as would be understood by the skilled person, the term ‘bristle’ may refer to an elongate strand of material formed substantially a single piece. The ‘bristle’ may be a resilient bristle. The resilient bristle may be biased towards a particular curvature. 
     Throughout this disclosure, the term ‘radially outwardly’ does not exclude the element additionally extending in the longitudinal direction of the device. For example, the plurality of flexible bristles may extend radially outwardly and longitudinally from the tube. 
     The plurality of flexible bristles may have a contracted configuration in the contracted delivery configuration. The plurality of flexible bristles may have an expanded configuration in the expanded deployed configuration. 
     In the expanded configuration, the plurality of flexible bristles may be configured to anchor the device in the bodily lumen. The plurality of flexible bristles may be configured to provide substantially all of the anchoring force for the embolization device in the bodily lumen. 
     In the expanded configuration, the plurality of flexible bristles may be configured to contact the bodily lumen. 
     Throughout this disclosure, the term “penetrates through’ refers to an object passing into and through another object. 
     A portion of the at least one of the plurality of flexible bristles is clamped between two opposing sides of the tube wall. 
     Throughout this disclosure, an element referred to as being ‘clamped between’ two clamping elements, refers to the two clamping elements directly or indirectly providing forces (for example, opposing forces) on the element so as to restrain the element. The clamping elements may directly or indirectly contact the clamped element. 
     The tube may be formed from a shrinkable material. The tube may be formed from a heat shrinkable material. The tube may be formed of a chemically shrinkable material. 
     Throughout this disclosure, a ‘shrinkable material’ may refer to a material which shrinks in a particular direction upon a particular treatment. Such a treatment may be a heat and/or or chemical treatment. As would be understood by the skilled person, the shrinkable materials themselves shrink without an external force being applied to them, for example, by crimping. 
     The tube may be shrunk such that a portion of the at least one of the plurality of flexible bristles is clamped between two opposing sides of the tube wall. 
     The tube may be shrunk in a radial direction of the tube. Additionally or alternatively, the tube may be shrunk in an axial direction of the tube. 
     The tube may be mechanically compressed in a radial direction such that a portion of the at least one of the plurality of flexible bristles is clamped between two opposing sides of the tube wall. The tube may be mechanically compressed by crimping. 
     Throughout this disclosure, the term ‘mechanically compressing’ an element refers to a compression which is caused by a mechanical interaction between an external device and the element. 
     The tube may be formed from a meltable or melted material. 
     At least a portion of the tube or substantially the whole tube may have been melted such that a portion of the at least one of the plurality of flexible bristles is secured to the tube. 
     At least a portion of the tube or substantially the whole tube may have been melted to allow the melted material of the tube to surround a portion of the flexible bristle(s). Thereafter, the melted material may have been allowed to solidify such that the portion is secured. 
     A filler material may be disposed within a lumen of the tube to secure the at least one of the plurality of flexible bristles to the tube. 
     The filler material may be an adhesive. 
     The filler material may be a curable material or a settable material. The filler material may be curable or settable upon heating, solvent flashing and/or irradiating. 
     The filler material may adhere or bond to the at least one of the plurality of flexible bristles. Additionally or alternatively, the filler material may mechanically anchor the at least one of the plurality of flexible bristles. 
     Throughout this disclosure, the term ‘mechanically anchor’ refers to the anchoring of an element substantially by mechanical forces caused by the macroscopic properties of the anchoring element, rather than intermolecular forces and/or chemical bonds between the anchoring element and the anchored element which are responsible for adhering/bonding. 
     The filler material may substantially fill the lumen of the tube. 
     The embolization device may further comprise a securing piece disposed within a lumen of the tube. The securing piece may be configured to secure the at least one of the plurality of flexible bristles to the tube. 
     A portion of the at least one of the plurality of flexible bristles may be clamped between the securing piece and an inner surface of the tube wall. 
     The securing piece may be an inner mandrel. 
     The securing piece may be an inner mandrel, where a portion of the at least one of the plurality of flexible bristles may be clamped between an outer surface of the inner mandrel and an inner surface of the tube wall. 
     A portion of the at least one of the plurality of flexible bristles which penetrates through the tube wall may have a greater radius than a hole in the tube wall through which the bristle penetrates the tube wall. 
     The portion of the at least one of the plurality of flexible bristles that penetrates through the tube wall may be a portion which is disposed within a lumen of the tube. 
     The portion of the least one of the plurality of flexible bristles disposed within a lumen of the tube may have a greater radius than a hole in the tube wall through which the bristle penetrates the tube wall. 
     A portion of the at least one of the plurality of flexible bristles which penetrates through the tube wall may comprise and anchoring section. 
     A portion of the at least one of the plurality of flexible bristles which penetrates through the tube wall may comprise a rough portion. 
     The rough portion may be rougher than another portion of the flexible bristle. The another portion may be a portion of the flexible bristle which extends radially outwardly from the tube wall. 
     The tube wall may have one or more holes defined therein. Each of the one or more holes may be configured to receive one or more of the plurality of flexible bristles. 
     The tube wall may have one or more pre-machined holes. The pre-machined hole(s) may be configured to receive one or more of the plurality of flexible bristles. 
     Throughout this disclosure, a ‘pre-machined hole’ refers to a hole which is created in a piece of material. For example, a pre-machined hole may be a hole which is machined in a continuous wall of the tube. The ‘machining’ may be carried out in various ways, for example, drilling or lasering. 
     The hole or pre-machined hole may receive only one of the at least one of the plurality of flexible bristles. The hole or pre-machined hole receives only two, three or four of the at least one of the plurality of flexible bristles. 
     The hole(s) or pre-machined hole(s) may have substantially the same diameter as the flexible bristle which passes therethrough. 
     The holes in the tube wall described anywhere herein may be arranged so as to arrange the flexible bristles in a prescribed manner. For example, the holes may be oriented such that the flexible bristles are distributed substantially evenly around the circumference of the stem. Additionally or alternatively, the plurality of holes may be arranged in spaced-apart segments. Optionally, a space between two spaced-apart segments may accommodate a flow restrictor. 
     The at least one of the plurality of flexible bristles may penetrate through the tube wall at a first location and penetrate through the tube wall at a second location. 
     The first location is different from the second location. 
     The first location and the second location may be on substantially opposite sides of the circumference of the tube. 
     The first location and the second location may be on the same half, third, quarter, fifth or sixth of the circumference of the tube. 
     The first location and the second location may be substantially axially aligned. 
     There is provided a method of manufacturing an embolization device for promoting clot formation in a lumen having a contracted delivery configuration and an expanded deployed configuration. The method may comprise providing a stem comprising a tube having a tube wall. The method may comprise providing a plurality of flexible bristles such that they extend radially outwardly from the tube. At least one of the plurality of flexible bristles may penetrate through the tube wall. 
     The method may comprise clamping the at least one of the plurality of flexible bristles between two opposing sides of the tube wall. 
     The method may comprise shrinking or mechanically compressing the tube such that a portion of the at least one of the plurality of flexible bristles is clamped between two opposing sides of the tube wall. 
     The tube may be shrunk or compressed in a radial direction of the tube. Additionally or alternatively, the tube may be shrunk or compressed in an axial direction of the tube. 
     The method may comprise melting at least a portion of the tube or substantially the whole of the tube such that a portion of the at least one of the plurality of flexible bristles is secured to the tube. 
     At least a portion of the tube or substantially the whole tube may be melted to allow the melted material of the tube to surround a portion of the flexible bristle(s). Thereafter, the melted material may be allowed to solidify such that the portion is secured. 
     The method may comprise disposing a filler material within a lumen of the tube to secure the at least one of the plurality of flexible bristles to the tube. The filler material may be disposed within the lumen before or after penetrating the at least one of the plurality of flexible bristles through the tube wall. 
     The filler material may be an adhesive. 
     The filler material may be cured or set. The filler material may be cured or set upon heating, solvent flashing and/or irradiating. 
     The filler material may adhere or bond to the at least one of the plurality of flexible bristles. Additionally or alternatively, the filler material may mechanically anchor the at least one of the plurality of flexible bristles. 
     The filler material may substantially fill the lumen of the tube. 
     The method may comprise disposing a securing piece within a lumen of the tube so as to secure the at least one of the plurality of flexible bristles to the tube. 
     A portion of the at least one of the plurality of flexible bristles may be clamped between the securing piece and an inner surface of the tube wall. 
     The securing piece may be an inner mandrel. A portion of the at least one of the plurality of flexible bristles may be clamped between an outer surface of the inner mandrel and an inner surface of the tube wall. 
     The tube may be shrunk or mechanically compressed. Additionally or alternatively, the securing piece may be radially expanded once the securing piece is disposed within the lumen such that the portion of the at least one of the plurality of flexible bristles is clamped between the securing piece and an inner surface of the tube wall. 
     The method may comprise machining a hole in the tube wall and receiving one or more of the at least one of the plurality of flexible bristles in the hole. 
     A portion of the at least one of the plurality of flexible bristles which penetrates through the tube wall has a greater radius than a hole in the tube wall through which the bristle penetrates the tube wall. 
     The method may comprise penetrating the at least one of the plurality of flexible bristles through the tube wall at a first location and penetrating the flexible bristle through the tube wall at a second location. 
     The method may comprise inserting a guide into a lumen of the tube such that a portion of the flexible bristle may be guided from the inside of the lumen through a hole to the outside of the tube. 
     There is provided an embolization device for promoting clot formation in a lumen and having a contracted delivery configuration and an expanded deployed configuration. The embolization device may comprise a stem formed from a material. The embolization device may comprise a plurality of flexible bristles extending radially outwardly from the stem. A portion of at least one of the plurality of flexible bristles may be disposed within a volume of the material of the stem such that the material surrounds and secures the portion of the flexible bristle. 
     Throughout this disclosure, reference to the ‘volume of the material’ may refer to a bulk or homogenous volume of the material. The volume of material is formed from a continuous portion of the material rather than two substantially individual elements (such as two opposing individual wires). 
     A portion of the flexible bristle is disposed within this ‘volume of material’. Accordingly, the portion is disposed within a bulk or homogenous volume of the material rather than between two substantially individual elements (for example, a flexible bristle held between two opposing individual wires). 
     Throughout this disclosure, as would be understood by the skilled person, a ‘stem being formed from a material’ refers to a stem where a significant portion of the stem&#39;s volume along which the bristles are attached is formed of the material. The stem&#39;s structural properties may be largely dictated by the material and its form rather than any other components of the stem. Accordingly, the stem may be formed substantially of the material. 
     The material need not be uniform. The material may have different properties and/or compositions in different portions of the stem. For example, the composition of the stem may change gradually from one part of the stem to another. 
     The material may adhere or bond to the portion of the at least one of the plurality of flexible bristles. 
     The material may mechanically anchor the portion of the at least one of the plurality of flexible bristles. 
     The material may be a curable material or settable material. The material may be curable or settable upon heating, solvent flashing and/or irradiating. 
     The material may be cured or set such that the material surrounds and secures the portion of the flexible bristle. 
     As used throughout herein, the ‘material’ may refer to the ‘filler material’ which is described herein. 
     The portion may comprise a rough portion. 
     The rough portion may be rougher than some or all other portions of the flexible bristle, and, in particular, the free portion which extends radially outwardly. 
     The portion may comprise a thick portion or anchoring portion. 
     The thick portion may be thicker than some or all other portions of the flexible bristle, and, in particular, the free portion which extends radially outwardly. 
     The stem may further comprise a covering element disposed on at least a portion of an outer surface of the material. 
     The covering element may be a tube. The material may be disposed within the tube. 
     The covering element may be in the form of a sheet. The sheet may be a curved sheet. 
     The stem may further comprise an inner element. The inner element may be disposed at last partially within the material. The inner element may extend along at least a portion of the length of the material. 
     The inner element may be elongated. The inner element may be rod-shaped. 
     The embolization device may further comprise a flow restrictor integral to the material of the stem. The flow restrictor may be formed from the material. 
     The flow restrictor may be a flow restricting membrane. 
     Any of the ‘flow restrictors’ or ‘flow restricting membranes’ disclosed herein may have a contracted configuration in the contracted delivery configuration. Any of the ‘flow restrictors’ or ‘flow restricting membranes’ disclosed herein may have an expanded configuration in the expanded deployed configuration. 
     In the expanded configuration, any of the ‘flow restrictors’ or ‘flow restricting membranes’ disclosed herein may be configured to anchor the device in the bodily lumen. The ‘flow restrictor’ or ‘flow restricting membrane’ may be configured to provide substantially all of the anchoring force for the embolization device in the bodily lumen. 
     In the expanded configuration, any of the ‘flow restrictors’ or ‘flow restricting membranes’ disclosed herein may be configured to contact the bodily lumen. 
     The material may be a polymer. The material may be a nylon. The material may be a resin. The material may be a metal and/or an alloy. 
     The portion of the at least one of the plurality of flexible bristles disposed within the material of the stem may extend substantially in a radially outward direction. 
     The portion of the at least one of the plurality of flexible bristles disposed within the material of the stem may extend substantially transversely to the longitudinal axis of the stem. 
     The at least one of the plurality of flexible bristles may substantially perpendicularly intersect the stem, preferably, at least in the unconstrained configuration of the embolisation device. 
     There is provided a method of manufacturing an embolization device for promoting clot formation in a lumen and having a contracted delivery configuration and an expanded deployed configuration. The method may comprise providing a stem formed from a material. The method may comprise providing a plurality of flexible bristles extending radially outwardly from the stem. A portion of at least one of the plurality of flexible bristles may be disposed within a volume of the material of the stem such that the material surrounds and secures the portion of the flexible bristle. 
     The method may comprise adhering or bonding the material to the portion of the at least one of the plurality of flexible bristles. 
     The method may comprise mechanically anchoring the portion of the at least one of the plurality of flexible bristles to the material. 
     The method may comprise curing or setting the material such that it surrounds and secures the portion of the flexible bristle. The curing or setting may be upon heating, solvent flashing and/or irradiating. 
     The method may comprise molding the material in a mold. 
     The method may comprise disposing the portion of the flexible bristle inside the mold such that the flexible bristle penetrates through a wall of the mold. 
     The step of disposing the portion of the flexible bristle inside the mold may occur before or after molding the material in a mold. 
     At least a portion of the mold may be a tube having a tube wall. 
     The tube may not be removed such that it forms a part of the final embolization device. 
     The embolization device may comprise the tube forming at least part of the mold. 
     The method may comprise shaping the material into the stem. 
     The method may comprise inserting the portion into the shaped stem. The method may comprise curing or setting the material. 
     The method may further comprise providing an inner element disposed at last partially within the material. 
     The inner element may be disposed within the material before the material is cured or set. 
     The inner element may be disposed within the material after the material is cured or set. The inner element may be inserted into a hole within the material. The hole may be created by the inner element itself and/or another device, such as a drill. 
     There is provided an embolization device for promoting clot formation in a lumen and having a contracted delivery configuration and an expanded deployed configuration. The embolization device may comprise a stem formed from a material. The embolization device may comprise a plurality of flexible bristles extending radially outwardly from the stem. The embolization device may comprise a flow restrictor extending radially outwardly from the stem. The flow restrictor may be formed from the material. The flow restrictor may be integrally formed with the material of the stem. 
     Throughout this disclosure, as would be understood by the skilled person, an element referred to as being ‘integrally formed with the material’ of another element means that the two elements are formed in such a way that there is no distinct, identifiable connection between the two elements. 
     The two elements may be formed form the same material. The two elements may be considered as one and the same. 
     The material may be a curable material or settable material. The material may be a curable material or settable material which is curable or settable upon heating, solvent flashing and/or irradiating. 
     The material may be a moldable material. 
     The material may be molded to integrally form the flow restrictor and the stem. 
     At least a portion of at least one of the plurality of flexible bristles may be disposed within a volume of the material of the flow restrictor and/or stem. 
     The at least a portion may be disposed within the volume of the material of the flow restrictor and/or stem such that the material surrounds and secures the portion of the flexible bristle. 
     The entirety of the at least one of the plurality of flexible bristles may be disposed within a volume of the material of the flow restrictor and/or stem. 
     The flow restrictor may be resilient and/or pre-curved. 
     The flow restrictor may be a flow restricting membrane. 
     The flow restrictor may comprise two or more individual segments. 
     The two or more individual segments may not be directly connected. Each of the two or more individual segments may be directly connected to the stem. 
     The stem may further comprise a covering element disposed on at least a portion of an outer surface of the material of the stem. The covering element may be a tube. The material may be disposed within the tube. 
     The covering element may be in the form of a sheet. The covering element may be a curved sheet. 
     The flow restrictor may further comprise a covering element disposed on at least a portion of an outer surface of the material of the flow restrictor. 
     The covering element may comprise two membranes. The material may be disposed between the two membranes. Each of the two membranes may extend radially outwardly from the stem. 
     The covering element may additionally or alternatively cover at least partially a surface of the material of the flow restrictor which extends substantially longitudinally. 
     There is provided a method of manufacturing an embolization device for promoting clot formation in a lumen and having a contracted delivery configuration and an expanded deployed configuration. The method may comprise providing a stem formed from a material. The method may comprise providing a plurality of flexible bristles extending radially outwardly from the stem. The method may comprise providing a flow restrictor extending radially outwardly from the stem. The flow restrictor may be formed from the material. The flow restrictor may be integrally formed with the material of the stem. 
     The stem and the flow restrictor may be molded in a mold. 
     The mold may be a single mold. The mold may define a single, continuous mold cavity. 
     The method may comprise disposing a portion of at least one of the flexible bristle inside the mold such that the at least one of the flexible bristles penetrates through a wall of the mold. 
     At least a portion of the mold may be a tube having a tube wall. 
     The embolization device may comprise the tube. 
     The tube may not be removed such that it forms a part of the final embolization device. 
     The embolization device may comprise the tube forming at least part of the mold. 
     A portion of the mold cavity defining the flow restrictor may be curved. 
     The method may comprise shaping the material into the stem and the flow restrictor. 
     Throughout this disclosure, the exemplary materials disclosed in relation to the ‘filler material’ are also exemplary materials for the ‘material’ referred to herein, and vice versa. 
     In any of the embodiments disclosed herein in which a flexible bristle penetrates through the tube wall, the tube wall may surround substantially the entire cross-sectional perimeter of the flexible bristle. 
     In any of the embodiments disclosed herein, the filler material may comprise or consist of: medical grade 2 part epoxy resin, polyurethane, nylon 12, Pebax 4033, liquid crystal polymer, polyether ether ketone, polycarbonate, neoprene, acrylate polymers or any combination thereof. 
     In any of the embodiments disclosed herein, the heat shrinkable material may comprise or consist of: polyolefin, Pebax, FEP, PTFE, PFA, ETFE, PET, polyether ether ketone or any combination thereof. 
       FIG. 1  shows an embolization device  100 . The embolization device  100  is configured for deployment in a bodily lumen so as to promote clot formation therein. The embolization device  100  in  FIG. 1  is shown in an unconstrained configuration. 
     The embolization device  100  comprises a stem  110 , a plurality of flexible bristles  120   a,    120   b  and a flow restricting membrane  130 . In any of the embodiments described herein, the flow restricting membrane  130  is optional. 
     The stem  110  extends along the longitudinal length of the embolization device  100 . The stem  110  may extend along substantially the whole longitudinal length of the embolization device  100  when the embolization device  100  is in the unconstrained configuration. 
     The stem  110  may be flexible, for example, flexible along substantially its entire length. The stem  110  may be flexible such that the embolization device  100  when deployed in a bodily lumen conforms to the shape of the bodily lumen. The stem  110  may have flexible sections, hinges and/or connectors (not shown) disposed along its length. Additionally or alternatively, the stem  110  may have a pre-curved shape. 
     A portion of the stem  110 , for example, a proximal portion, may have a detachment mechanism (not shown) configured to be removably attachable to a delivery element, such as a delivery wire. For example, the detachment mechanism may be female screw hole. 
       FIG. 1  shows the plurality of flexible bristles  120   a,    120   b  as two spaced-apart segments of bristles in the form of a proximal bristle segment  120   a  and a distal bristle segment  120   b  which are spaced apart along the longitudinal length of the stem  110 . However, as would be understood by the skilled person, various arrangements of the plurality of flexible bristles  120   a,    120   b  is possible, for example, in any number of segments, including a single segment. Furthermore, the plurality of flexible bristles  120   a,    120   b  need not be identical and may have, for example, different lengths, materials, flexibilities and/or thickness. 
     Each of the plurality of flexible bristles  120   a,    120   b  is secured to the stem  110  and extends radially outwardly from the stem  110 . 
     Each of the plurality of flexible bristles  120   a,    120   b  may be spaced apart along the longitudinal length of the stem  110 . In certain embodiments, at least some of the plurality of flexible bristles  120   a,    120   b  may be disposed at the same axial location along the stem  110 . 
     The flow restricting membrane  130  may be attached to the stem  110 . The flow restricting membrane  130  may have a hole therein through which the stem  110  passes, however, other arrangements are contemplated herein. 
     The flow restricting membrane  130  may extend radially outwardly from the stem  110 . The flow restricting membrane 130  may be of any shape, for example, generally circular. The flow restricting membrane  130  may be flexible, resilient and/or pre-curved. In alternative embodiments, the flow restricting membrane  130  may be any kind of flow restrictor. 
     The flow restricting membrane  130  may be disposed between some of the plurality of flexible bristles  120   a,    120   b.  In certain embodiments, the flow restricting membrane  130  may be disposed between the proximal bristle segment  120   a  and the distal bristle segment  120   b,  as shown in  FIG. 1 . 
       FIG. 2  shows the embolization device  100  in a contracted delivery configuration within a delivery catheter C. 
     As can be seen from  FIG. 2 , in the contracted delivery configuration of the embolization device  100 , the plurality of flexible bristles  120   a,    120   b  have been collapsed into a contracted configuration. 
     As also can be seen from  FIG. 2 , in the contracted delivery configuration of the embolization device  100 , the flow restricting membrane  130  has been collapsed into a contracted configuration. 
     In  FIG. 2 , both the proximal bristle segment  120   a  and the distal bristle segment  120   b  point proximally. However, as will be evident to the person skilled in the art, any arrangement in this regard is possible. In particular, the proximal bristle segment  120   a  and the distal bristle segment  120   b  may point distally. The proximal bristle segment  120   a  may point proximally and the distal bristle segment  120   b  may point distally. The proximal bristle segment  120   a  may point distally and the distal bristle segment  120   b  may point proximally. 
       FIG. 3  shows the embolization device  100  in an expanded deployed configuration in a bodily lumen L. The embolization device  100  may be disposed within the bodily lumen Lin the expanded deployed configuration by removing the delivery catheter C whilst inserted in the bodily lumen L such that the embolization device  100  is allowed to expand in the bodily lumen L. 
     The expanded deployed configuration of the embolization device  100  has a greater radial extent than the contracted delivery configuration shown in  FIG. 2 . In the expanded deployed configuration shown in  FIG. 3 , the plurality of flexible bristles  120   a,    120   b  and the flow restricting membrane  130  contact the bodily lumen L so as to anchor the embolization device  100  within the bodily lumen L. The anchoring force provided by the plurality of flexible bristles  120   a,    120   b  and the flow restricting membrane  130  may be sufficient to resist migration of the embolization device  100  in the bodily lumen L. 
     In the expanded deployed configuration shown in  FIG. 3 , the embolization device  100  may occlude the bodily lumen L and promote clot formation therein. 
       FIGS. 1 to 3  show a purely exemplary particular form of embolization device, however, aspects of the present disclosure need not be applied specifically to the form of embolization described in reference to these figures. Accordingly, various modifications may be made to the overall structure/arrangement of the described embolization device, such as a different number/arrangement of bristle segments, number of bristles in each bristle segment, types of bristles within each bristle segment. Furthermore, connections/hinges may be present along the length of the stem, for example, between some or all of the bristle segments. 
     In this regard, reference is made to the embolization devices disclosed in each of WO 2014/140325 and WO 2016/041961, both of which are incorporated herein by reference in their entirety. 
       FIG. 4  shows a cross-section along part of the length of an embodiment of the embolization device, and, in particular, the stem  210  and flexible bristles  220 . 
     The stem  210  comprises a tube having a tube wall  211 . The tube may be generally cylindrical. The tube may define a lumen along the longitudinal axis of the tube. 
     The plurality of flexible bristles  220  extend radially outwardly from the tube, and, in particular, the tube wall  211 .The plurality of flexible bristles  220  each penetrate through the tube wall  211 . 
     As shown in  FIG. 4 , the plurality of flexible bristles  220  each penetrate through the tube wall  211  such that a portion of each of the flexible bristles  220  is disposed within the lumen of the tube. 
     The tube wall  211  may have a plurality of holes therein (not shown) through which, for example, a single one or some of the plurality of flexible bristles  220  passes therethrough. The holes may each have substantially the same diameter as the flexible bristle which passes therethrough. 
     The plurality of holes in the tube wall  211  may be arranged so as to arrange the flexible bristles  220  in a prescribed manner. For example, the plurality of holes may be oriented such that the flexible bristles  220  are distributed substantially evenly around the circumference of the stem  210 . Additionally or alternatively, the plurality of holes may be arranged in spaced-apart segments. Optionally, a space between two spaced-apart segments may accommodate a flow restricting membrane. 
     The stem  210  further comprises filler material  212  disposed within the lumen of the tube. As shown in  FIG. 4 , the filler material  212  may substantially fill the lumen of the tube. 
     The filler material  212  disposed within the lumen of the tube may engage the portions of the flexible bristles  220  which are disposed within the lumen of the tube. The filler material  212  may act to secure the plurality of flexible bristles  220  to the stem  210 . 
     The filler material  212  may be an adhesive. In such embodiments, the filler material  212  may engage the flexible bristles  210  by adhering or bonding to the flexible bristles  210 . 
     The filler material may be a curable material or settable material, which is curable or settable upon heating, solvent flashing and/or irradiating. Upon curing or setting, the material may harden so as to secure the flexible bristles  220  to the stem  210 . 
     The filler material  212  may engage the flexible bristles  220  by mechanically anchoring the flexible bristles  220  to the stem  210 . 
     As one (or a sub-set) of the plurality of flexible bristles  220  passes through each hole in the tube wall  211 , the flexible bristles  220  are attached to the stem individually or in a (small) sub-set. Accordingly, if the integrity of the attachment of one of the flexible bristles becomes compromised, the integrity of the attachments of the other flexible bristles may not be compromised. For example, if one of the plurality of flexible bristles  220  is dislodged from the stem  210 , the attachment of the remaining flexible bristles may remain uncompromised, which is not the case when the majority of the attachment force for a particular bristle is provided for by surrounding/neighbouring bristles. 
     The stem  210  and flexible bristles  220  of the embolization device may be manufactured by creating, for example, by machining, a plurality of holes in the tube wall  211  of the tube. One of the plurality of flexible bristles  220  may be inserted through each of the plurality of holes in the tube wall  211  such that a portion of each of the flexible bristles  220  extends into the lumen of the tube and a free portion of each of the flexible bristles  220  extends radially outwardly from the tube wall  211 . 
     The filler material  212  may be disposed in the lumen of the tube. The filler material  212  may be disposed in the lumen of the tube before or after inserting the flexible bristles  220 . 
     In certain embodiments, the filler material  212  may be a curable of settable material such that after disposing the filler material  212  in the lumen of the tube, the filler material  212  is cured or set such that it hardens so as to secure the plurality of flexible bristles  220  to the stem  210 . 
       FIG. 5  shows a cross-section along part of the length of an embodiment of the embolization device, and, in particular, the stem  310  and flexible bristles  320 . 
     The stem  310  of the embolization device comprises a tube having a tube wall  311 . 
     As can be seen from  FIG. 5 , each of the plurality of flexible bristles  320  penetrate through the tube wall  311 . A free portion  321   a  of each of the plurality of flexible bristles  220  extends radially outwardly from the tube, and, in particular, the tube wall  311 . 
     A clamped portion  321   b  of each of the plurality of flexible bristles  320  is clamped between two opposing sides of the tube wall  311 . The opposing sides of the tube wall  311  provide a clamping force on each of the clamped portions  321   b  such that the flexible bristles  320  are secured to the stem  310 . 
     In the embodiment shown in  FIG. 5 , the tube of the stem  310  has a lumen  313  extending along substantially the entire length of the tube. In this embodiment, the lumen  313  is a continuous lumen in which the clamped portions  321   b  of the flexible bristles  320  are disposed within the lumen  313 . The opposing sides of the tube wall  311  may not contact each other at regions between the clamped portions  321   b  such that a continuous lumen is defined. 
     One portion of the lumen  313  may not be in fluid communication with another portion of the lumen  313 , for example, due to a clamped portion  321   b  entirely filling a section of the lumen  313 . 
     In certain embodiments, the portions of the tube wall  311  between some of all of the clamped portions  321   b  may be configured such that the opposing sides of the tube wall  311  contact each other (not shown in  FIG. 5 ). 
     Optionally, the portions of the tube wall  311  of the tube between each of the clamped portions  321   b  may be configured such that the opposing sides of the tube wall  311  contact each other such that the tube may comprise a number of distinct, isolated lumens disposed along the length of the tube. The lumens of the tube may be substantially filled by the clamped portions  321   b  of the plurality of flexible bristles  320 . 
     The lumen(s)  313  of the tube may be filled with any filler material disclosed herein, such as the filler material  212  of  FIG. 4 . 
     The stem  310  and flexible bristles  320  of the embolization device may be manufactured by creating, for example, by machining, a plurality of holes in the tube wall  311  of the tube. One or some of the plurality of flexible bristles  320  may be inserted through each of the plurality of holes in the tube wall  311  such that a portion  321   b  of each of the flexible bristles  320  extends into the lumen  313  of the tube. 
     The portions  321   b  of each of the flexible bristles  320  may be clamped between two opposing sides of the tube wall  311 . 
     In this regard, at least portions of the tube may be shrunk, for example, heat shrunk or chemically shrunk, in a radial direction such that the portions  321   b  of each of the flexible bristles  320  are clamped between two opposing sides of the tube wall  311 . 
     Additionally or alternatively, at least portions of the tube may be compressed (e.g. mechanically compressed), for example, by crimping, in a radial direction such that the portions  321   b  of each of the flexible bristles  320  are clamped between two opposing sides of the tube wall  311 . 
       FIG. 6  shows a cross-section along part of the length of an embodiment of the embolization device, and, in particular, the stem  410  and flexible bristles  420 . 
     The stem  410  of the embolization device comprises a tube having a tube wall  411 . 
     As can be seen from  FIG. 6 , each of the plurality of flexible bristles  420  penetrates through the tube wall  411 . A free portion  421   a  of each of the plurality of flexible bristles  420  extends radially outwardly from the tube, and, in particular, the tube wall  411 . 
     A clamped portion  421   b  of each of the plurality of flexible bristles  420  is clamped between an inner mandrel  414  disposed within the lumen of the tube and the tube wall  411 . 
     The clamped portions  421   b  of each of the flexible bristles  420  may be disposed within an annulus  415  defined between the inner mandrel  414  and the tube wall  411 . 
     The outer surface of the inner mandrel  414  and the inner surface of the tube wall  411  provide a clamping force on each of the clamped portions  421   b  such that the flexible bristles  420  are secured to the stem  410 . 
     The portions of the tube wall  411  between some or all of the clamped portions  421   b  may be configured such that the outer surface of the inner mandrel  414  and the inner surface of the tube wall  411  contact each other (not shown in  FIG. 6 ). 
     Optionally, the portions of the tube wall  411  between some or all of the clamped portions  421   b  may be configured such that the outer surface of the inner mandrel  414  and the inner surface of the tube wall  411  contact each other such that the stem  410  defines a number of distinct, isolated annuluses disposed along the length of the tube. The annuluses of the stem  410  may be substantially filled by the clamped portions  421   b.    
     The annulus  313  or annuluses of the stem  410  may be filled with any filler material disclosed herein, such as the filler material  212  of  FIG. 4 . 
     The stem  410  and flexible bristles  420  of the embolization device may be manufactured by creating, for example, by machining, a plurality of holes in the tube wall  411  of the tube. One of the plurality of flexible bristles  420  may be inserted through each of the plurality of holes in the tube wall  411  such that a portion  421   b  of each of the flexible bristles  420  extends into the lumen of the tube. 
     An inner mandrel  414  may be inserted into the lumen of the tube such that the portions  321   b  are clamped between the inner mandrel  414  and the tube wall  411 . Optionally, the tube wall  411  of the tube may be shrunk or mechanically compressed and/or the inner mandrel  414  may be radially expanded once it has been inserted into the lumen of the tube. 
       FIG. 7  shows a cross-section along part of the length of an embodiment of the embolization device, and, in particular, the stem  510  and flexible bristles  520 . 
     The stem  510  of the embolization device comprises a tube having a tube wall  511 . 
     Each of the plurality of flexible bristles  520  penetrates through the tube wall  511  such that a portion  521   b  is disposed within the lumen  513  of the tube. A free portion  521   a  of each of the plurality of flexible bristles  520  extends radially outwardly from the tube, and, in particular, the tube wall  511 . 
     As shown in  FIG. 7 , the portion  521   b  disposed within the lumen  513  of the tube is thicker than the free portion  521   a.  The portion  521   b  may be configured such that the flexible bristle is secured to the tube. Specifically, the portion  521   b  may have a larger radius than the radius of a hole in the tube wall  511  through which the flexible bristle passes. 
     Additionally or alternatively, the portion  521   b  disposed within the lumen  513  of the tube may comprise a rough portion. The rough portion may be rougher than some or all portions of the free portion  521   a.    
     The lumen  513  of the stem  510  may be filled with any filler material disclosed herein, such as the filler material  212  of  FIG. 4 . 
     Additionally or alternatively, some or all of the portions  521   b  may be clamped between two opposing sides of the tube wall  511 , in a similar manner as described in relation to  FIG. 5 . 
     Additionally or alternatively, some or all of the portions  521   b  may be clamped between an inner mandrel (not shown) disposed within the lumen  513  of the tube and the tube wall  511 , in a similar manner as described in relation to  FIG. 6 . 
     The stem  510  and flexible bristles  520  of the embolization device may be manufactured by creating, for example, by machining, a plurality of holes in the tube wall  511  of the tube. One of the plurality of flexible bristles  520  may be inserted through each of the plurality of holes in the tube wall  511  such that a portion  521   b  of each of the flexible bristles  520  extends into the lumen  513  of the tube. 
     For example, a guide may be inserted into the lumen  513  of the tube such that the free portion  521   a  may be guided from the inside of the lumen  513  through the hole to the outside of the tube. 
     Additionally or alternatively, the tube may have a thin slit along at least a portion of its length so as to facilitate insertion of the flexible bristles  520  through their respective holes from the inside of the lumen. 
     In the embodiments described with reference to  FIGS. 4 to 7 , an end of the flexible bristles terminates within the tube of the stem. However, some or all of the flexible bristles of the embodiments described with reference to  FIGS. 4 to 7  may extend through the stem such that both ends of the flexible bristles are exterior to the stem. The means and methods described in relation to  FIGS. 4 to 7  are equally applicable to such embodiments. 
     For example,  FIG. 8  shows a cross-section along part of the length of an embodiment of the embolization device, and, in particular, the stem  610  and flexible bristles  620 . 
     As in the previous embodiments, the embolization device comprises a tube having a tube wall  611 . The plurality of flexible bristles  620  each penetrate through the tube wall  611  at a first location and at a second location. Both of the ends of the flexible bristles  620  are disposed outside the tube of the stem. Both ends extend radially outwardly from the tube, and, in particular, the tube wall  611 . 
     In the embodiment shown in  FIG. 8 , the stem  610  further comprises filler material  612  disposed within the lumen of the tube in a similar manner to that described in relation to  FIG. 4 . However, as noted above, any means or methods described herein are suitable for securing the flexible bristles  620  to the stem. 
     The above-noted first location and second location may be chosen in various manners. 
     In this regard, reference is made to  FIG. 9  which shows a transverse cross-section along the length of an embodiment of the embolization device, and, in particular, the stem  710  and flexible bristles  720 . 
     As can be seen from  FIG. 9 , each of the flexible bristles  720  passes through holes  713  at first and second locations in the tube wall  711 . In a similar manner as above, purely as an example, the stem  710  further comprises filler material  712  disposed within the lumen of the tube to secure the flexible bristles  720  to the stem  710 . 
     The first and second locations of the holes  713  are on substantially opposite sides of the circumference of the tube. 
       FIG. 10  shows a transverse cross-section along the length of another embodiment of the embolization device, and, in particular, the stem  810  and flexible bristles  820 . 
     Each of the flexible bristles  820  passes through holes  813  at first and second locations in the tube wall  811 . In a similar manner as above, purely as an example, the stem  810  further comprises filler material  812  disposed within the lumen of the tube to secure the flexible bristles  820  to the stem  810 . 
     As can be seen from  FIG. 10 , the first and second locations of the holes  813  are in the same quarter of the circumference of the stem. In other embodiments, the first and second locations of the holes  813  are in the same half, third, fifth or sixth of the circumference of the stem. 
     Optionally, the first and second locations of the holes  713  are substantially axially aligned. 
     The flexible bristles  720 ,  820  may be inserted through the holes at the first and second locations using a guide disposed within the lumen of the tube. 
     Additionally or alternatively, the tube may have a thin slit along at least a portion of its length so as to facilitate insertion of the flexible bristles  720 ,  820  through their respective holes at the first and second locations. 
       FIG. 11  shows a cross-section along part of the length of an embodiment of the embolization device, and, in particular, the stem  910  and flexible bristles  920 . 
     The plurality of flexible bristles  920  extend radially outwardly from the stem  910 . In particular, a free portion  921   a  of each of the plurality of flexible bristles  920  extends radially outwardly from the stem  910 . 
     The stem  910  is formed from a material  912 . A portion  921   b  of each of the flexible bristles  920  is disposed within a volume of the material  912  of the stem  910 . The material  912  surrounds the portion  921   b  and secures the portion  921   b  to the stem  910 . 
     As shown in  FIG. 11 , the material  912  substantially entirely surrounds and contacts an end portion  921   b  of each of the flexible bristles  920 . Specifically, the material  912  may contact substantially an entire transversely extending edge surface of each of the flexible bristles  920 . 
     Referring to  FIG. 11 , the volume of the material  912  is a bulk or homogenous volume of the stem  910  formed from a continuous volume of the material  912 . 
     The material  912  of the stem  910  engages the portions  921   b  of the flexible bristles  920 . The material  912  acts to secure the plurality of flexible bristles  920  to the stem  910 . 
     The material  912  may be an adhesive. In such embodiments, the material  912  may engage the portions  921   b  of the flexible bristles  910  by adhering or bonding to the portions  921   b.    
     The material  912  may be a curable material or settable material, which is curable or settable upon heating, solvent flashing and/or irradiating. Upon curing or setting, the material may harden so as to secure the flexible bristles  920  to the stem  910 . 
     The material  912  may engage the portions  921   b  of the flexible bristles  920  to mechanically anchor the flexible bristles  920  to the stem  910 . 
     As one (or a sub-set) of the plurality of flexible bristles  920  passes into the material of the stem  910 , the flexible bristles  920  are attached to the stem individually or in a (small) sub-set. Accordingly, if the integrity of the attachment of one of the flexible bristles becomes compromised, the integrity of the attachments of the other flexible bristles may not be compromised. For example, if one of the plurality of flexible bristles  920  is dislodged from the stem  910 , the attachment of the remaining flexible bristles may remain uncompromised, which is not the case when the majority of the attachment force for a particular bristle is provided for by surrounding/neighbouring bristles. 
     Furthermore, the material  912  may be chosen so as to influence the structural properties of the stem  910 , for example, flexibility. 
     The stem  910  and flexible bristles  920  of the embolization device may be manufactured by providing a stem  910  formed from a material  912  and providing a plurality of flexible bristles  920  such that a portion  921   b  of each of the flexible bristles  920  is disposed within a volume of the material  912 . 
     For example, the portions  921   b  of the flexible bristles  920  may be inserted into the material  912 . Thereafter, the material  912  may be cured or set such that the material  912  surrounds the portions  921   b  and secures the portions  921   b  to the stem  910 , for example, by the hardening and/or contraction of the material  912 . 
     In certain embodiments, the stem  910  may be formed by molding the material  912 . For example, the portions  921   b  of the flexible bristles  920  may be inserted into a mold cavity defined by a mold. A material to be molded may be inserted into the mold cavity. The material may be allowed to set such that the material  912  surrounds and secures the flexible bristles  920 . The mold may then be removed to leave the stem  910  and flexible bristles  920  secured thereto. 
     In certain embodiments, a mold is not required. For example, the material  912  may be shaped into the stem  910 . Thereafter, the plurality of flexible bristles  920  may be inserted into the shaped material  912  such that the portions  921   b  are disposed within a volume of the material  912 . Thereafter, the material  912  may optionally be cured or set such that the material  912  surrounds the portions  921   b  and secures the portions  921   b  to the stem  910 , for example, by the hardening and/or contraction of the material  912 . 
       FIG. 12  shows a cross-section along part of the length of an embodiment of the embolization device, and, in particular, the stem  1010  and flexible bristles  1020 . 
     The embodiment shown in  FIG. 12  is similar to the embodiment of  FIG. 11  in that the embolization device has a stem  1010  formed from a material  1012 , and where a portion  1021   b  of each of the flexible bristles  1020  is disposed within a volume of the material  1012  and a free portion  1021   a  extends radially outwardly. 
     However, in the embodiment shown in  FIG. 12 , the portion  1021   b  is thicker than the free portion  1021   a.  For example, the portion  1021   b  may include a spherical anchoring section. Additionally or alternatively to the thickened region, the portion  1021   b  may comprise a rough region (not shown). The rough region may be rougher than some or all portions of the free portion  1021   a.    
     The forms of the flexible bristles  1020  are generally applicable to all embodiments described herein. 
       FIG. 13  shows a cross-section along part of the length of an embodiment of the embolization device, and, in particular the stem  1110  and flexible bristles  1120 . 
     The embodiment shown in  FIG. 13  is similar to the embodiment of  FIG. 11  in that the embolization device has a stem  1110  formed from a material  1112 , and where a portion of each of the flexible bristles  1120  is disposed within a volume of the material  1112  and a free portion extends radially outwardly. 
     However, in the embodiment shown in  FIG. 13 , the stem  1110  further comprises a structural member  1113 . The structural member  1113  may be disposed at least partially or entirely within the material  1112  of the stem  1110 . 
     The structural member  1113  may extend longitudinally along the length of the stem  1110 . The structural member  1113  may be elongated or rod-shaped. 
     The structural member  1113  may be disposed within the material  1112  before the material  1112  is cured or set so as to secure the structural member  1113  within the material  1112  of the stem. Alternatively, the structural member  1113  may be disposed within the material  1112  by inserting it into the material  112  after it has been cured or set, for example, by boring a hole within the material  1112  using the structural member  1113  itself and/or another device, such as a drill. 
       FIG. 14  shows a cross-section along part of the length of an embodiment of the embolization device, and, in particular, the stem  1210 , flexible bristles  1220  and flow restricting membrane  1230 . 
     The embodiment shown in  FIG. 14  is similar to the embodiment of  FIG. 11  in that the embolization device has a stem  1210  formed from a material  1212 , and where a portion of each of the flexible bristles  1220  is disposed within a volume of the material  1212  and a free portion extends radially outwardly. 
     However, as can be seen from  FIG. 14 , the embolization device further comprises a flow restricting membrane  1230 . The flow restricting membrane may extend radially outwardly from the stem  1210 . 
     The flow restricting membrane  1230  is formed from the same material  1212  as the stem  1210 . The flow restricting membrane  1230  is integrally formed with the material  1212  of the stem. As the stem  1210  and the flow restricting membrane  1230  are formed integrally, the above-noted issues relating to the attachment of a separate membrane to a core may be avoided. 
     The stem  1210 , flexible bristles  1220  and flow restricting membrane  1230  may be manufactured by providing a stem  1210  and flow restricting membrane  1230  formed integrally from the material  1212 , and providing a plurality of flexible bristles  1220  such that a portion  1221   b  of each of the flexible bristles  1220  is disposed within a volume of the material  1212 . 
     For example, the stem  1210  and flow restricting membrane  1230  may be formed by molding the material  1212 . In this regard, a continuous mold cavity defined in a single mold may have a shape which defines the stem  1210  and the flow restricting membrane  1230  connected thereto. The portions  1221   b  of the flexible bristles  1220  may be inserted into the mold cavity by inserting them through holes defined in the mold. A moldable material may be disposed in the mold cavity and allowed to set such that the material  1212  take the form of the stem  1210  and the flow restricting membrane  1230  connected thereto. The material  1212  also sets to surround and secure the flexible bristles  1220 . The mold may then be removed to leave the stem  1210 , the flexible bristles  1220  secured thereto, and the flow restricting membrane  1230 . 
     In certain embodiments, a mold is not required. For example, the material  1212  may be shaped into the stem  1210  and flow restricting membrane  1230 . Thereafter, as described above, the plurality of flexible bristles  1220  may be inserted into the shaped material  1212 . Thereafter, the material  912  may optionally be cured or set. 
       FIG. 15  shows a cross-section along part of the length of an embodiment of the embolization device, and, in particular, the stem  1310 , flexible bristles  1320  and flow restricting membrane  1330 . 
     The embodiment shown in  FIG. 15  is similar to the embodiment of  FIG. 14  in that the embolization device has a stem  1310  and flow restricting membrane  1330  formed integrally from a material  1312 , and where a portion of each of the flexible bristles  1320  is disposed within a volume of the material  1312  and a free portion extends radially outwardly. 
     However, as can be seen from  FIG. 15 , the stem  1310  further comprises two tubes each having tube walls  1311   a,    1311   b,  in a similar manner to the tube with tube wall  211  described in relation to  FIG. 4 . As can be seen from  FIG. 15 , the plurality of flexible bristles  1320  extend radially outwardly from the tubes, and, in particular, the tube walls  1311   a,    1311   b.  The plurality of flexible bristles  1320  each penetrate through the respective tube walls  1311   a,    1311   b  as detailed herein. 
     The tubes may be disposed on either side of the flow restricting membrane  1330 . 
     The stem  1310 , flexible bristles  1320  and flow restricting membrane  1330  may be manufactured in a similar manner to that described in relation to  FIG. 14 . 
     However, two tubes having tube walls  1311   a,    1311   b  are disposed over the material  1312 . In this regard, the tubes may form part of a mold used to mold the material  1312  which is not removed after molding. 
     In other embodiments, the tubes may be placed over the material  1312  of the stem  1310  once the material  1312  has been shaped by any means into the form of the stem  1310 . 
       FIG. 16  shows a cross-section along part of the length of an embodiment of the embolization device, and, in particular, the stem  1410 , flexible bristles  1420  and flow restricting membrane  1430 . 
     The embodiment shown in  FIG. 16  is similar to the embodiment of  FIG. 14  in that the embolization device has a stem  1410  and flow restricting membrane  1430  formed integrally of a material  1412 , and where a portion of each of the flexible bristles  1420  is disposed within a volume of the material  1412  and a free portion extends radially outwardly. 
     However, as can be seen from  FIG. 16 , a portion  1421   b  of at least one of the plurality of flexible bristles  1420  is disposed within a volume of the material  1412  of the flow restricting membrane  1430 . The material  1412  of the flow restricting membrane  1430  may surround and secure the portion  1421   b.    
     A free portion  1421   a  of the at least one of the plurality of flexible bristles  1420  extends freely radially outwardly from the flow restricting membrane  1430 . 
     In certain embodiments, the entirety of the at least one of the plurality of flexible bristles  1420  is disposed within the within a volume of the material  1412  of the flow restricting membrane  1430 . In such embodiments, no free portion extends radially outwardly from the flow restricting membrane  1430 . 
     The bristles may provide certain structural characteristics (such as rigidity/flexibility) to the flow restricting membrane  1430 , and may improve the integrity of the flow restricting membrane  1430  relative to the stem  1410 . 
     The stem  1410 , flexible bristles  1420  and flow restricting membrane  1430  may be manufactured in a similar manner to that described in relation to  FIG. 14 . 
     However, the at least one of the flexible bristles  1420  is received within a volume of the material  1412  of the flow restricting membrane  1430 . In this regard, the at least one of the flexible bristles  1420  may be inserted into the mold through a hole formed in the mold such that it penetrates into the part of the cavity which defines the flow restricting membrane  1430 . In other embodiments, the at least one of the flexible bristles  1420  may be inserted into the material of the flow restricting membrane after it has been formed. 
     In the embodiments described with reference to  FIGS. 11 to 16 , an end of the flexible bristles terminates within the stem and/or flow restricting membrane. 
     In this regard, reference is made to  FIG. 17  which shows a transverse cross-section along the length of an embodiment of the embolization device, and, in particular, the stem  1510 , plurality of flexible bristles  1520  and flow restricting membrane  1530 . As can be seen from this figure, each of the flexible bristles  1520  has an end section which is disposed within the stem  1510 . In certain embodiments, some of the end sections of the flexible bristles  1520  may terminate within the flow restricting membrane  1530 . 
     However, in other embodiments, some or all of the flexible bristles of the embodiments shown in  FIGS. 11 to 16  may extend through the stem and/or flow restricting membrane such that both ends of the flexible bristles are exterior to the stem and/or flow restricting membrane. The means and methods described in relation to  FIGS. 11 to 16  are equally applicable to such embodiments. 
     In this regard, reference is made to  FIG. 18  which shows a transverse cross-section along the length of an embodiment of the embolization device, and, in particular, the stem  1610 , plurality of flexible bristles  1620  and flow restricting membrane  1630 . As can be seen from this figure, each of the flexible bristles  1520  passes through the stem  1610  and/or flow restricting membrane  1630 . 
     Both of the ends of the flexible bristles  1620  are disposed outside the stem  1610  and/or flow restricting membrane  1630 . Both ends extend radially outwardly from the stem  1610  and/or flow restricting membrane  1630 . 
     As shown in  FIG. 18 , the each of the flexible bristles  1520  penetrates the surface of the stem  1610  and/or flow restricting membrane  1630  at a first location and a second location. The first and second locations of may be on substantially opposite sides of the circumference of the stem  1610  and/or flow restricting membrane  1630 . 
     In a similar manner described in relation to  FIG. 10 , various arrangements of the first and second locations are contemplated. For example, the first and second locations of may be in the same quarter of the circumference of the stem  1610  and/or flow restricting membrane  1630 . The first and second locations may be in the same half, third, fifth or sixth of the circumference of the stem  1610  and/or flow restricting membrane  1630 . 
     Optionally, the first and second locations are substantially axially aligned. 
       FIGS. 17 and 18  show an embolization device with a flow restricting membrane, but the arrangements of the flexible bristles are equally applicable to embodiments without a flow restricting membrane. 
     Although the above explanation is considered to fully clarify how the present disclosure may straight-forwardly be put into effect by those skilled in the art, it is to be regarded as purely exemplary. In particular, there are a number of variations which are possible, as may be appreciated by those skilled in the art. 
     For example, even though the embodiments described in relation to  FIGS. 4 to 10  show specific examples of securing the plurality of flexibles to the stem, such examples are preferred embodiments. Accordingly, any means of securing the plurality of flexibles to the stem, and, in particular, the tube is envisaged, so long as at least one of the plurality of flexible bristles penetrates through the tube wall of the tube. 
     Furthermore, even though the above embodiments have been described with all of the plurality of flexible bristles secured to the stem using the same means, it will be evident to the skilled person that not all of the plurality of flexible bristles need to be secured to the stem by the same means. Any combination of the above-noted means and methods may be used to attach the plurality of flexible bristles to the stem. 
     Further, even though the embodiment described in relation to  FIG. 15  comprises two tubes  1311   a,    1311   b,  any number of tubes may be used, including a single tube. Furthermore, the tubes may be any sort of covering element which is disposed on at least a portion of any outer surface of the material of the stem. 
     The above embodiments refer to a flow restricting membrane, however, other forms of flow restrictors are also envisaged in accordance with the present disclosure. In particular, any shape of flow restrictor is envisaged, so long as the flow restrictor acts to restrict flow in the bodily lumen L. 
     In the embodiments described in relation to  FIGS. 14 to 18 , at least of portion of each of the flexible bristles is disposed within the material of the stem and/or flow restrictor. However, this is optional. In particular, any means and methods, for example, conventional means and methods, may be used to secure the flexible bristles to the stem, and portions of the stem to which the flexible bristles are secured may be formed by conventional means and method, for example, using a twisted wire method, as described in WO 2014/140325 and WO 2016/041961, both of which are incorporated herein by reference in their entirety. 
     All of the above are fully within the scope of the present disclosure, and are considered to form the basis for alternative embodiments in which one or more combinations of the above described features are applied, without limitation to the specific combinations disclosed above. 
     In light of this, there will be many alternatives which implement the teaching of the present disclosure. It is expected that one skilled in the art will be able to modify and adapt the above disclosure to suit its own circumstances and requirements within the scope of the present disclosure, while retaining some or all technical effects of the same, either disclosed or derivable from the above, in light of his common general knowledge in this art. All such equivalents, modifications or adaptions fall within the scope of the present disclosure. 
     Embodiments can be described with reference to the following numbered clauses, with certain features laid out in dependent clauses: 
     Clause 1: An embolization device for promoting clot formation in a bodily lumen and having a contracted delivery configuration and an expanded deployed configuration, the embolisation device comprising: a stem comprising a tube having a tube wall and a plurality of holes in the tube wall; and a plurality of flexible bristles extending radially outwardly from the tube, wherein each hole has at least one of the plurality of flexible bristles penetrating through said hole; wherein a filler material is disposed within a lumen of the tube to secure the at least one of the plurality of flexible bristles to the tube. 
     Clause 2: The embolization device of clause 1, wherein the filler material is an adhesive. 
     Clause 3: The embolization device of clause 1 or 2, wherein the filler material is a curable material or a settable material, and, optionally, wherein the filler material is curable or settable upon heating, solvent flashing and/or irradiating. 
     Clause 4: The embolization device of clause 1, 2 or 3, wherein the filler material adheres or bonds to the at least one of the plurality of flexible bristles, and/or wherein the filler material mechanically anchors the at least one of the plurality of flexible bristles. 
     Clause 5: The embolization device of any one of clauses 1 to 4, wherein the filler material substantially fills the lumen of the tube. 
     Clause 6: An embolization device for promoting clot formation in a bodily lumen and having a contracted delivery configuration and an expanded deployed configuration, the embolisation device comprising: a stem comprising a tube having a tube wall and a plurality of holes in the tube wall; and a plurality of flexible bristles extending radially outwardly from the tube, wherein each hole has at least one of the plurality of flexible bristles penetrating through said hole; further comprising a securing piece disposed within a lumen of the tube and configured to secure the at least one of the plurality of flexible bristles to the tube. 
     Clause 7: The embolization device of clause 6, wherein a portion of the at least one of the plurality of flexible bristles is clamped between the securing piece and an inner surface of the tube wall. 
     Clause 8: The embolization device of clause 6, wherein the securing piece is an inner mandrel, and wherein a portion of the at least one of the plurality of flexible bristles is clamped between an outer surface of the inner mandrel and an inner surface of the tube wall. 
     Clause 9: The embolization device of any preceding clause, wherein a portion of the at least one of the plurality of flexible bristles which penetrates through the tube wall has a greater radius than a hole in the tube wall through which the bristle penetrates the tube wall. 
     Clause 10: The embolization device of any preceding clause, wherein a portion of the at least one of the plurality of flexible bristles which penetrates through the tube wall comprises a rough portion. 
     Clause 11: A method of manufacturing an embolization device for promoting clot formation in a lumen having a contracted delivery configuration and an expanded deployed configuration, the method comprising: providing a stem comprising a tube having a tube wall and a plurality of holes in the tube wall; and providing a plurality of flexible bristles such that they extend radially outwardly from the tube, wherein each hole has at least one of the plurality of flexible bristles penetrating through said hole; the method comprising disposing a filler material within a lumen of the tube to secure the at least one of the plurality of flexible bristles to the tube. 
     Clause 12: The method clause 11, wherein the filler material is an adhesive. 
     Clause 13: The method of clause 11 or 12, wherein the filler material is cured or set, and, optionally, wherein the filler material is cured or set upon heating, solvent flashing and/or irradiating. 
     Clause 14: The method of clause 11, 12 or 13, wherein the filler material adheres or bonds to the at least one of the plurality of flexible bristles, and/or wherein the filler material mechanically anchors the at least one of the plurality of flexible bristles. 
     Clause 15: The method of any one of clauses 11 to 14, wherein the filler material substantially fills the lumen of the tube. 
     Clause 16: A method of manufacturing an embolization device for promoting clot formation in a lumen having a contracted delivery configuration and an expanded deployed configuration, the method comprising: providing a stem comprising a tube having a tube wall and a plurality of holes in the tube wall; and providing a plurality of flexible bristles such that they extend radially outwardly from the tube, wherein each hole has at least one of the plurality of flexible bristles penetrating through said hole; the method comprising disposing a securing piece within a lumen of the tube so as to secure the at least one of the plurality of flexible bristles to the tube. 
     Clause 17: The method of clause 16, wherein a portion of the at least one of the plurality of flexible bristles is clamped between the securing piece and an inner surface of the tube wall. 
     Clause 18: The method of clause 16, wherein the securing piece is an inner mandrel, and wherein a portion of the at least one of the plurality of flexible bristles is clamped between an outer surface of the inner mandrel and an inner surface of the tube wall. 
     Clause 19: The method of any one of clauses 16 to 18, wherein a portion of the at least one of the plurality of flexible bristles which penetrates through the tube wall has a greater radius than a hole in the tube wall through which the bristle penetrates the tube wall. 
     Clause 20: The method of any one of clauses 16 to 19, comprising inserting a guide into a lumen of the tube such that a portion of the flexible bristle may be guided from the inside of the lumen through a hole to the outside of the tube.