WO2004045460A1

WO2004045460A1 - Implant comprising a closed loop and an insulated insert

Info

Publication number: WO2004045460A1
Application number: PCT/NL2003/000821
Authority: WO
Inventors: Eugène Christian OLGERS; Patrick Michael Olgers; Lambertus Wilhelmus Bartels; Christian Johannes Gerardus Bakker
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-11-21
Filing date: 2003-11-21
Publication date: 2004-06-03
Anticipated expiration: 2005-05-21
Also published as: AU2003284841A1; NL1021969C2

Abstract

The invention relates to a device which can be introduced into a body, such as a stent or electrode, and is formed from a metal-containing material. The drawbacks of the known art are obviated or at least alleviated in that the device comprises at least one closed loop, wherein the loop comprises an insert of insulating material.

Description

IMPLANT COMPRISING A CLOSED LOOP AND AN INSULATED INSERT

The present invention relates to a device which can be introduced into a body, such as a stent, a filter or an electrode, and is formed from a metal-containing material, which device comprises at least one closed loop. Such devices are generally known and comprise, as said, for instance stents, filters and electrodes.

A significant drawback of such devices is that, in the vicinity thereof and in particular in the interior thereof, no imaging is possible during for instance RI ("Magnetic Resonance Imaging") when a volume is enclosed. This is because an electric current is induced in the loop or loops under the influence of the RF field applied in MRI. Regions in the interior of the device, or in any case in the vicinity thereof, are thereby screened, just as in a Faraday cage. The currents induced in the loop or loops create counter fields, thereby impeding or even preventing effective imaging.

The present invention has for its object to obviate or at least alleviate said drawbacks of the known art, for which purpose a device according to the present invention is distinguished in that the loop comprises an insert of insulating material. This is understood to mean electrically insulating properties of the material used for the insert. In such a device according to the present invention a circuit in a loop thereof is effectively interrupted and no counter fields are generated as long as no currents can flow. It has hereby become possible using imaging techniques to map regions in the close vicinity of the device, and even in the interior thereof, when a determined space is enclosed. It is noted that this can be particularly favourable in the case of a stent, where this is being used to remedy narrowing of an artery. Such artery narrowing can be combatted with a stent but can continue to grow through or along the stent, about which no information can be obtained as long as the stent prevents effective imaging. The same is substantially the case for a filter, where it is for instance used to at least catch a clot. In such a case the quantity of clot intercepted by the filter can be imaged when a filter, which must normally comprise a number of loops and according to the invention has inserts, does not impede such imaging.

It is further noted that devices are known which are formed entirely from insulating materials. These do not however have any action at all as electrode.

Furthermore, such devices of insulating material are considerably less effective as stent, this in respect of the expansion and form-retention after expansion thereof. Devices are also known in which use is made of insulating connecting parts between and for the connection of metal parts of a device. In order to avoid the presence of current loops, if this were an objective, connections must be made at positions where this is not even necessary or desirable for the mutual interconnection of the parts, and/or a design of such a device must be modified to take into account where the insulating connections have to be arranged.

The present invention also relates to diverse preferred embodiments.

It is thus possible that a device according to the invention can be stretched in order to be expanded after insertion and then retain the expanded form, whereby the device is for instance formed from a memory material, metal etc. As noted above, memory materials are for instance generally formed mainly from metal-containing materials, particularly in the case of stents, which makes such devices particularly sensitive to loss of imaging in the interior and the immediate vicinity thereof.

The device can also be produced in diverse ways. It is thus possible for the insert to be arranged in a substantially tubular or plate-like basic element, from which the device can be formed by arranging incisions therein. This is per se a standard method of forming stents, even though in the known art no use is made of tubular basic elements having therein at least one insert, the production and final design of which follows by making the incisions in the tubular element. Particularly because of the fact that insulating materials generally have an inadequate form-retention after expansion thereof, a device according to the present invention preferably comprises the feature that the insert is arranged in a part of this device which is not subject to stretch when it expands. The choice of usable materials is hereby increased considerably, and even ceramic materials, silicon and the like can be applied for the insert.

It is also possible for the device to be formed from at least one thread-like element, in which the insert is arranged at a location along the thread-like element corresponding with a loop. This is another standard production method with thread-like, substantially metal-containing elements, but then these thread-like elements are therefore adapted by the inserts of insulating material in a manner according to the present invention. In embodiments wherein a number of loops of different circumference formed from the same thread-like element are present in a device according to the invention, it can be particularly favourable to arrange at least the same number of inserts as loops at fixed distances in the thread-like element, wherein the distance between the inserts along the thread-like element is shorter than the circumference of the smallest of the loops. A uniform production process of thread-like elements is thus ensured, which results in a simplification compared to a situation in which inserts are arranged only at selected positions corresponding with the loops to be actually formed. Also in embodiments in which the thread-like element is produced from substantially metal-like material with a memory function, the inserts can then still be rigid and stiff and not strip-elastic, without essentially influencing the expansion function desired in the case of a stent. It is noted that, as will be immediately apparent to a skilled person, devices according to the present invention can also be applied as electrode in a method of electrophysiology based on a number of electrodes. Use can very advantageously be further made of threads and sheets, of for instance metal or other material to be used as electrode, to form the device according to the invention herefrom, if the inserts have already been provided beforehand therein - before the actual production of the device. The inserts do not then have to be arranged later, after production of a device, by cutting pieces of material out of the device and replacing these with pieces of insulating material as insert. The freedom in design for manufacturers of such devices is hereby also considerably increased and improved, particularly if the inserts are arranged with great regularity in the pieces of material serving as basic elements.

A number of embodiments of the present invention will be described hereinbelow on the basis of the annexed figures, in which a number of exemplary embodiments of devices according to the present invention are shown in non-limitative manner, in which the same or similar components are designated with substantially the same reference numeral, and in which: fig. 1 shows a side view of a stent as embodiment of the present invention; fig. 2 shows a plate-like element as possible basis from which the stent shown in fig. 1 can be formed; fig. 3 shows a thread-like element as alternative to the plate-like element shown in fig. 2; fig. 4 shows a detail of a possible embodiment such as can be designed from the thread-like element shown in fig. 3; and fig. 5 is a perspective view of production of a stent according to the invention.

Fig. 1 shows a stent 1 according to the present invention in the expanded state thereof into which this stent 1 is brought after introduction thereof into a human body. Stent 1 comprises ribs 2 of substantially metal-containing material, which is for instance favourable when it has a memory action for the purpose of retaining the assumed expanded form after expansion. Arranged in longitudinal ribs 3 of stent 1 are inserts 4, which are manufactured from an insulating material. This ensures that induced currents, which could impede a possible imaging as a result of the thereby generated counter-field, cannot flow in the loops formed along longitudinal ribs 3. Both the flow of electrical currents and the generation of counter-fields are thus effectively prevented with the inserts 4 of insulating material.

Fig. 2 shows a plate-like element 5. Incisions 6 can be arranged in plate-like element 5. When the outer ends of plate-like element 5 are connected to each other as indicated with arrow A in fig. 2, and after arranging the incisions 6, the thus formed device is ready to be used as stent and is then not (yet) expanded. After expansion such a device formed from plate-like element 5 will have approximately the form of the expanded stent shown in fig. 1.

It is noted that in fig. 2 not all incisions 6 have yet been made, and that various incisions in fig. 2 are still only indicated schematically in the form of a line where the still missing incisions 6 must be realized. It is also noted that the dimensioning in fig. 2 is not necessarily in proportion to that of fig. 1.

A strip 7 of insulating material is further arranged in plate-like element 5 prior to this latter being connected all along the sides as according to arrow A in fig. 2 and incisions 6 being arranged therein. An alternative method will be described below with reference to fig. 5. Strip 7 provides the inserts of insulating material as designated with reference numeral 4 in fig. 1 after the incisions 6 have been made, plate-like element 5 has been given a round form by connecting the outer ends along arrow A, and the thus formed stent is expanded.

The longitudinal ribs 3, in which inserts 4 of insulating material are arranged, are per se not subject to stretch or stretching when a thus formed stent is expanded. This is favourable when use is made for instance of metals or materials with a memory effect, and the insulating material for the inserts does not have such a memory action or stretchability and is for instance stiff or rigid. In such situations an insert without the required memory action and with a degree of elasticity could reduce the effectiveness of the stent itself, this being obviated by positioning inserts 4 in a manner such that such a reduction in the effectiveness of the stent is prevented. This is particularly the case for parts of the stent 1 which are not subject to stretch.

Fig. 3 shows a thread-like element 8. As an alternative to the plate-like element 5 shown in fig. 2, use can be made of such a thread-like element 8 to form therefrom a stent as shown for instance in fig. 1.

In fig. 3 the thread-like element is provided with inserts 9 of insulating material. Inserts 9 are positioned at mutual distances which can be adapted to the stents or electrodes to be finally formed therefrom. This means that an insert 9 as interruption of a circuit formed from thread-like element 8 can be realized in each case at a location specifically determined for this purpose. Alternatively however, it is also possible to place inserts 9 at a position such that any circuit can be broken with certainty.

Such a situation is shown in fig. 4. Fig. 4 shows a number of thread-like elements 8 which are mutually connected at connection 12 and each form two loops. Such a configuration can be a detail of a stent or electrode, which can be a device according to the present invention. The middle thread-like element in fig. 4 forms two loops 10 and 11, wherein loop 10 is smaller in size than loop 11. In this embodiment the inserts 9 are arranged at mutually equal distances, wherein an insert 9 is also arranged with certainty in the smaller of the two loops, i.e. loop 10, in order to break the circuit there. For this purpose the mutual distance between inserts 9 is smaller than the circumference of the smallest of the loops, again loop 10. In this manner inserts 9 can be arranged at mutually equal distances along the length of thread-like element 8, which results in a standard production process, wherein circuits in the device to be formed with thread-like element 8 are broken with certainty. The production process of thread-like element 8 can then take place in a manner not dependent on the final form of the device.

In the embodiment shown in fig. 2, use is made of a plate-like element 5 with incisions 6 therein, the edges of which are mutually connected along arrow A in order to obtain a cylindrical whole. As shown in fig. 5, it is also possible to make use of a sleeve-like or tubular element 14. This is then arranged for instance round a rod 13 in order to form the incisions therein using a knife 17 so as to produce the final, desired form of the stent. The incisions with blade 17 are arranged along the lines shown with dotted line 18.

In order to form the inserts 15, sleeve 14 is provided with at least one band 16 with a material according to the present invention. After making the incisions with blade 17, the inserts 15 then remain in the ribs of the thus formed stent.

After the foregoing it will be apparent that many additional and alternative embodiments are possible, all of which will be apparent to a skilled person who can realize these additional and alternative embodiments without inventive work of his/her own. It is thus possible in the configuration of fig. 1 to also provide ribs other than the longitudinal ribs with inserts, for instance in the loops on the left and right-hand side in fig. 1. Ceramic material is for instance mentioned as an example of materials used for the insert. It is noted that ceramic material can be a highly suitable carrier, for instance for medication, to thus enable very local and precise administering of drugs. Use can also be made of insulating materials other than the stated materials for the inserts. It could even be possible in the future to also apply insulating materials with a memory action, whereby inserts can also be positioned at positions which will be subject to stretch when the device is expanded. The present invention can also be applied in production methods other than those discussed above (plate-like and/or tubular elements with incisions and thread-like elements) , as long as circuits in the form of loops are broken at the desired positions, which circuits could otherwise impede or even prevent imaging. Devices according to the present invention can also find particular application in the field of electrophysiology, wherein a number of electrodes are applied, thus demonstrating that the present invention is not limited to the field of application of stents alone.

Claims

1. Device which can be introduced into a body, such as a stent, a filter or an electrode, and is formed from a metal-containing material, which device comprises at least one closed loop, characterized in that the loop comprises an insert of insulating material.

2. Device as claimed in claim 1, which can be stretched in order to be expanded after insertion and then retain the expanded form, and is formed substantially for this purpose from a material from the group comprising: memory material, form-retaining material, a metal etc.

3. Device as claimed in claim 2, wherein the insert is arranged in a substantially plate-like basic element, from which the device can be formed by arranging incisions therein.

4. Device as claimed in claim 2 or 3, wherein the insert is arranged in a part of the device which is not subject to stretch when it expands.

5. Device as claimed in claim 4, wherein the insert is formed from a material from the group comprising ceramic material, silicon and the like.

6. Device as claimed in any of the foregoing claims, which is formed from at least one thread-like element, in which the insert is arranged at a location along the thread-like element corresponding with a loop.

7. Device as claimed in claim 6, which comprises at least two loops of different circumference formed from the same thread-like element, and at least the same number of inserts as loops are arranged at fixed distance in the thread-like element, wherein the distance between the inserts along the thread-like element is shorter than the circumference of the smallest of the loops.

8. Device as claimed in any of the foregoing claims, which forms an electrode for applying in a method of electrophysiology based on a number of electrodes.

9. Device as claimed in any of the foregoing claims, wherein the insert is formed from a material, such as ceramic, suitable as a carrier for medication. ■

10. Device as claimed in claim 9, wherein a medicine for administering locally is arranged on the insert.

11. Device as claimed in at least one of the foregoing claims, wherein the insert is arranged at discrete locations in or along elements of basic material from which the device is formed, such as plates, threads etc.