CA2190900C - Medical device visible when using magnetic resonance imaging - Google Patents
Medical device visible when using magnetic resonance imaging Download PDFInfo
- Publication number
- CA2190900C CA2190900C CA002190900A CA2190900A CA2190900C CA 2190900 C CA2190900 C CA 2190900C CA 002190900 A CA002190900 A CA 002190900A CA 2190900 A CA2190900 A CA 2190900A CA 2190900 C CA2190900 C CA 2190900C
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- Prior art keywords
- markers
- catheter
- magnetic resonance
- resonance imaging
- axis
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/285—Invasive instruments, e.g. catheters or biopsy needles, specially adapted for tracking, guiding or visualization by NMR
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L29/00—Materials for catheters, medical tubing, cannulae, or endoscopes or for coating catheters
- A61L29/14—Materials characterised by their function or physical properties, e.g. lubricating compositions
- A61L29/18—Materials at least partially X-ray or laser opaque
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M25/00—Catheters; Hollow probes
- A61M25/01—Introducing, guiding, advancing, emplacing or holding catheters
- A61M25/0105—Steering means as part of the catheter or advancing means; Markers for positioning
- A61M25/0127—Magnetic means; Magnetic markers
Abstract
The invention relates to a medical device for use under MRI conditions, comprising a body containing para and/or ferromagnetic material. The para and/or ferromagnetic material has been received in separate elements which have substantially equal dimensions in three directions at right angles to one another.
The relative distance between the elements is substantially such, that there is at least almost no magnetic interaction between adjoining elements.
The relative distance between the elements is substantially such, that there is at least almost no magnetic interaction between adjoining elements.
Description
The invention relates to a medical device such as a catheter, balloon, graft and stmt, which is introduced into the body of a patient either temporax-ily or for a longer period of time for the purpose of treatment and/or investigation. More particularly, this invention relates to such a device having an imaging marker for' use with rnagnetic resonance imaging.
It is known to make such a device visible by means of ferro or paramagnetic materials. The ferro or paramagnetic materia7_s disturb the magnetic field in the NMR device in a contx-olled manner, as a result of which they become visible on the accessory imaging device.
The present: invention relates to a medical device, such as a medical catheter, having an imaging marker which is preferably integral with the device and in which the imaging marker produces an equal disturbance of the nuclear magnetic resonance field regardless of the position of the medical device relative to the magnetic resonance imaging equipment. In other words, the outer dimensions of the imaging marker remain substantially the same regardless of the orientation of the catheter relative to the magne:t:ic imaging equipment. Thus, the intensity of the image presented on the imaging screen is substantially identical regardless of whether the catheter is viewed from the side of the catheter, the top of the catheter, or even the end of the catheter. With such a uniform distribution of the ferromagnetic or paramagnetic material, even an e:lomgated device may be made uniformly visible regardless of the orientation of the device.
A medical device constructed in accordance with one aspect of the present invention for use with a nuclear magnetic resonance system includes a body portion formed of a polymer material and includes at least one magnetic radiation imaging marker. The imaging marker is preferably formed of paramagnetic or ferromagnetic material. Also, the imaging marker is a configuration which exhibits the property of having substantially identical outer dimensions when the medical device is viewed by nuclear radiation imaging equipment when viewed along any one of thrE:e axes which are at right angles to each other. In other- words, the outer dimensions of the imaging marker appear to be substantially identical regardless of the angle at which the medical device i.s "viewed" by the magnetic resonance imaging equipment.
Thus, the medical device may be viewed along an x-axis, a y-axis, or a z-axis i_n which each of these axes extend at right angles to each other, and in each case the outer dimensions of the imaging marker remain the same when viewed by imaging equipment.
In accordance with another aspect of the present invention, the medical device may take the form of a medical catheter in which the body portion comprises a cylindrical tube having a predetermined outer diameter and in which t:he radiation imaging marker extends around one-half of the circumference of the cylindrical tube and extends along the length of the cylindrical tube for a length equal to the outer diameter of the tube. With this construction, the outer dimensions of the imaging marker remain the same regardless of the imaging marker remain the same regardless of the orientation of the catheter relative to the imaging system.
In accordance with still another aspect of the invention the medical catheter includes at least two magnetic radiation imaging markers in which the markers are spaced apart from each other at a distance such that there is substantially no magnetic interaction between the markers when the device is irradiated by nuclear magnetic radiation. Accordingly, each of the radiation imaging markers produces its own independent visual image which is unaffected by an adjacent marker.
In accordanr_e with a preferred construction, the imaging markers are :paced apart from each other such that the spacing between individual markers is greater than the length of the outer dimensions of an individual imaging marker. Preferably this spacing is equal to or greater than twice the length of the outer dimensions of an individual imaging marker.
Preferably, the medical catheter is formed by extruding a cylindrical body portion by using a controlled extrusion in which pc>lymer material is extruded without any magnetic material. and then a polymer material comprising at least a portion of which includes paramagnetic or ferrc>magnetic material is extruded to create an imaging marker section. Another way to achieve the extrusions the alternate materials is to injection mold the body at a processing temperature which is chosen to be higher than the: melting temperature of the basic polymer material but i.s lower than the melting temperature of the paramagnetic or ferromagnetic material. With this form of construction the granules of magnetic material remain in a matrix of the basic polymer material as separate elements.
Alternatively, holes may be drilled into the side walls of the body portion of the catheter by use of a laser beam. Each of these holes may be filled with an appropriate configuration of paramagnetic or ferromagnetic material.
Various paramagnetic and ferromagnetic materials may be selected for use in constructing the present invention. Paramagnetic materials such as dysprosium, gadolinium and alloy: and salts of these materials may be used, or alternative7_y, ferromagnetic materials such as iron, nickel, cobalt and alloys of these materials may be used.
The invention will be explained in greater detail in the following description with reference to the attached drawings, in which a number of examples of embodiments of the device according to the invention have been illustrated. :In the drawings, Figure 1 is a diagrammatic view of a preferred embodiment illustrating a partly cut away end of a medical catheter according to the invention;
Figure 2 is a diagrammatic view illustrating a cross section along the line .II-II of Figure 1;
Figure 3 is a diagrammatic view illustrating another embodiment of the invention;
Figure 4 is a diagrammatic view illustrating the cross-sectional view along the line IV-IV of Figure 3;
Figure 5 is a diagrammatic view illustrating yet another embodiment of a tube-l.:ike device according to the invention;
Figure 6 is a diagrarr~matic view illustrating a cross-section along the line VI-VI of Figure 5;
Figure 7 is a diagrammatic view illustrating schematically another aspect of the present invention;
Figure 8 is a diagrammatic view illustrating a wire provided with elements;
Figure 9 is a diagrammatic view illustrating a partly broken away view of an end of a catheter according to the invention, wherein the wire of Figure 8 has been employed 5 in a reinforcing layer;
Figure 10 is a diagrammatic view illustrating a cross-section along the line X-X of Figure 9;
Figure 11 is a diagrammatic view illustrating an alternative version of an embodiment corresponding to Figure 9;
Figure 12 is a diagrammatic view illustrating a cross-sectional view along the line XII-XII of Figure 11;
Figure 13 is a diagrammatic view illustrating a partly cut-away section of an end of another embodiment of the invention;
Figure 14 is a diagrammatic view illustrating a cross-section along the line XIV-XIV of Figure 13; and Figure 15 is a diagrammatic view illustrating a partly cut-away section of a~ balloon catheter in accordance with the present invention.
Referring t.o the drawings, the medical device 1 as shown in Figure 1 i.s for instance an end-section of the cylindrical tube body 2 of a catheter. The tube body 2 comprises a lumen 3 extending through the tube body 2 in a longitudinal direction.
As can be seen in Figure 1 and 2, the body 2 is made up of a number of body sections 4, 5, 6, 7 comprising paramagnetic or ferromagnetic material alternated with body sections 8 which. are made of basic polymer material.
The sections 4, 7 may for instance have been received in the basic material 8 by means of an injection moulding process. During injection moulding, the supply of basic material 8 and the supply of the material of which the sections 4-7 are made', is in that case switched on and off alternately.
The sections 4-7 provided with paramagnetic or ferromagnetic materiel have a dimension in the longitudinal direction of the basic body 2, which is substantially equal t:o the diameter thereof. Thus these sections form elements which have substantially equal.
dimensions in three directions at right angles to each other.
As a result: the disturbance of a magnetic field such as the one used with magnetic resonance imaging (MRI), caused by each of the separate elements, is at least virtually independent of the position these elements take up in this magnetic field. In other words, whether the centre lines of the elements 4-7 run parallel to the magnetic field lines or are at right-angles to them, the disturbance of the magnetic field and consequently the visibility on the sr_reen of the resultant artefact remains more or less the same.
The same is; true for the device 10 of Figure 3.
Also in this case they elements 11, 12, 13, 14 comprising the paramagnetic or ferromagnetic material are alternated with sections 15 made of basic material. The elements 11-14 have also in this case a length which is substantially equal to the diameter' of the tube body.
Additionally the elements 13, 14 which are positioned at the distal end of the device 10, have a greater density of paramagnetic or ferromagnetic material, so that they are more clearly visible on the screen of the MRI-device.
The relative distance between the elements 4-7 of the device 1 and the elements 11-14 of the device 10 is substantially such, that there is at least practically no magnetic interaction between the adjoining elements. With the embodiment of Figure 1, the relative distance between the elements is at least equal to the length and the diameter of each of t:he elements 4-7, which is to say at least equal to the outer dimensions of these imaging markers. With a suitable concentration of the paramagnetic or ferromagnetic material in the elements known as such, the relative effect on each other is very small, so that the elements function as separate elements when a nuclear magnetic resonance field is applied.
With a higher concentration of the paramagnetic or ferromagnetic material, a greater distance is required between the separate elements in order to limit the magnetic interaction between adjacent elements.
With the device 20 shown in Figure 5, the basic material 22 of the body 21 is provided with a great number of spherical element; 23 comprising paramagnetic or ferromagnetic material. Because of the spherical shape, the disturbance of the magnetic field is also independent of angle of the device within magnetic field.
The imaging marker 23 may be inserted into the basic material 22 when forming the basic body 21 by means of extrusion or injection moulding. In that case the elements are granules of a plastic material including the paramagnetic or ferromagnetic material. The magnetic material has a melt:in.g temperature which is higher than the melting temperature of the basic material 22. Thus, the elements 23 can be applied as solid particles in a flow of liquid basic: material 22. Mixing the particles 23 into the basic material 22, in which case the basic material 22 is also in granular form, can be done prior to melting the material. By mixing the different granules properly, an even di:~tribution of the elements 23 in the basic material 22 care be achieved. During the extrusion or injection moulding process, a temperature is chosen at which only the granules of basic material 22 melt. The granules 23 will remain in the basic material 22 in the form of more or less solid particles.
Figure 7 shows schematically the importance of a suitable distance between the elements 23. With the dashed and dotted line 24, an area surrounding each element 23 has been indicated, over which the magnetic field in a MRI device may be considered to be disturbed by this element 23. When the elements 23 would be positioned close to each other, so that these areas 24 would overlap to a significant degree, the two elements 23 concerned would, from an image standpoint blend together so as to form one elongated element. As can be seen in Figure 7, the elements 23 should preferably be arranged at such a distance from one another, so that there is no magnetic interaction between the adjoining elements 23.
The invention can also be employed in a suitable manner with a device according to the invention in the form of a catheter provided with a braided reinforcing layer. Such a catheter has been illustrated schematically and in a partly broken away view in Figure 9.
'the catheter 30 is made up of a first cylindrical inner layer 31, which has been extruded on a mandrel. Around this inner layer 31, a reinforcing layer of wires 33, 34 are braided. For the sake of clarity only two wires are shown in Figure 4, but in the usual manner there may be numerous reinforcing wires. Next, an outer layer 32 may be extruded around this braided reinforcing layer, so that the r~=_inforcing layer is enclosed by the inner layer 31 and the outer layer 32.
As can be seen in greater detail in Figure 8, the wire 34 of the catheter 30 is provided, at equal distances, with magnfstic elements 35 which are substantially spherical and consequently have equal dimensions in three directions at right angles to one another. The elements 35 may for instance be arranged around the wire 34 :by means of an extrusion process.
Another possibility ~L;~ to attach the elements 35 as drops of hardening materia7_ comprising the magnetic material to the wire 34. When the material has hardened, the wire 34 can be incorporated in the catheter 30.
With the embodiment of Figure 9, a satisfactory directional independency is achieved since the elements 35 are positioned on a helical path. In particular, if this helical line has a pitch angle of 45°, sections of this helical arrangement which are arranged on either side opposite each other will always be placed at right angles to one another, so that there always will be sections of the helical path which are positioned at right angles to the magnetic field.
With the device 40 of Figures 11 and 12, a braided layer has been co-extruded of which at least one wire 42 carries the magnetic elements 43 made of paramagnetic or ferromagnetic material. The device 50 of Figure 13 comprises a. tubular body 51. This tubular body 51 is made up of an inner body 52, and arranged around it, an outer layer 53. In the inner layer 52, a number of holes 54 have been formed by means of a laser device.
These holes 54 are preferably arranged on a helical path.
In the holes 54 formed, elements 56 have been fitted which either comprise or are made of paramagnetic or ferromagnetic material. The magnetic elements 56 are temporarily fixed in the holes 54, for instance by means 5 of glueing. Next t:he inner layer 52, is provided with elements 56 and is passed through an extrusion device and provided with an outer layer 53, which consequently encloses the elements 56 in the holes 54.
The device according to the invention may be any 10 medical device which is received for a shorter or longer period of time inside' the body of a patient and of which the position has to be visualized by means of MRI. Tn addition to tube-like catheters such devices may be stem s or grafts.
Another po~~sible embodiment of such a device is a balloon, such as the balloon 60 shown in Figure 15.
This balloon is arranged on a catheter, and by means of the latter, advanced to the correct position inside the body of the patient.
With the embodiment of Figure 15, the balloon 60 comprises an outer :Layer 61 and an inner layer 62, which layers 61, 62 are connected to each other by means of a layer of glue 63. The layer of glue 63 comprises in this case evenly distributed granular particles of paramagnetic or ferromagnetic material. By properly mixing the glue and the magnetic material, the elements of magnetic material formed by these granules can be enclosed in between the outer layer 61 and the inner layer 62 of the balloon 60, placed at a suitable distance from one another, so that the balloon 60, independent of the direction of the magnetic field, can be made properly visible when using twhe MRI device.
Suitable materials of which to make the elements referred to above are, for instance, paramagnetic materials, such as dysprosium and gadolinium, and alloys and salts of these materials. Ferromagnetic materia:Ls which are preferably used are iron, nickel, cobalt and alloys of these mat:e:rials. The concentration of the paramagnetic or ferromagnetic material used in the elements may vary from 0.001% in the case of strong ferromagnetic materials to 100% by weight. The concentration of the magnetic material in the elements received in the device can, as described above referring to the Figures 3 and 4, vary according to the position of these elements in thE~ device. Thus it is possible to make for instance the distal end-section of a catheter more clearly visible than :its more proximal located elements.
It is known to make such a device visible by means of ferro or paramagnetic materials. The ferro or paramagnetic materia7_s disturb the magnetic field in the NMR device in a contx-olled manner, as a result of which they become visible on the accessory imaging device.
The present: invention relates to a medical device, such as a medical catheter, having an imaging marker which is preferably integral with the device and in which the imaging marker produces an equal disturbance of the nuclear magnetic resonance field regardless of the position of the medical device relative to the magnetic resonance imaging equipment. In other words, the outer dimensions of the imaging marker remain substantially the same regardless of the orientation of the catheter relative to the magne:t:ic imaging equipment. Thus, the intensity of the image presented on the imaging screen is substantially identical regardless of whether the catheter is viewed from the side of the catheter, the top of the catheter, or even the end of the catheter. With such a uniform distribution of the ferromagnetic or paramagnetic material, even an e:lomgated device may be made uniformly visible regardless of the orientation of the device.
A medical device constructed in accordance with one aspect of the present invention for use with a nuclear magnetic resonance system includes a body portion formed of a polymer material and includes at least one magnetic radiation imaging marker. The imaging marker is preferably formed of paramagnetic or ferromagnetic material. Also, the imaging marker is a configuration which exhibits the property of having substantially identical outer dimensions when the medical device is viewed by nuclear radiation imaging equipment when viewed along any one of thrE:e axes which are at right angles to each other. In other- words, the outer dimensions of the imaging marker appear to be substantially identical regardless of the angle at which the medical device i.s "viewed" by the magnetic resonance imaging equipment.
Thus, the medical device may be viewed along an x-axis, a y-axis, or a z-axis i_n which each of these axes extend at right angles to each other, and in each case the outer dimensions of the imaging marker remain the same when viewed by imaging equipment.
In accordance with another aspect of the present invention, the medical device may take the form of a medical catheter in which the body portion comprises a cylindrical tube having a predetermined outer diameter and in which t:he radiation imaging marker extends around one-half of the circumference of the cylindrical tube and extends along the length of the cylindrical tube for a length equal to the outer diameter of the tube. With this construction, the outer dimensions of the imaging marker remain the same regardless of the imaging marker remain the same regardless of the orientation of the catheter relative to the imaging system.
In accordance with still another aspect of the invention the medical catheter includes at least two magnetic radiation imaging markers in which the markers are spaced apart from each other at a distance such that there is substantially no magnetic interaction between the markers when the device is irradiated by nuclear magnetic radiation. Accordingly, each of the radiation imaging markers produces its own independent visual image which is unaffected by an adjacent marker.
In accordanr_e with a preferred construction, the imaging markers are :paced apart from each other such that the spacing between individual markers is greater than the length of the outer dimensions of an individual imaging marker. Preferably this spacing is equal to or greater than twice the length of the outer dimensions of an individual imaging marker.
Preferably, the medical catheter is formed by extruding a cylindrical body portion by using a controlled extrusion in which pc>lymer material is extruded without any magnetic material. and then a polymer material comprising at least a portion of which includes paramagnetic or ferrc>magnetic material is extruded to create an imaging marker section. Another way to achieve the extrusions the alternate materials is to injection mold the body at a processing temperature which is chosen to be higher than the: melting temperature of the basic polymer material but i.s lower than the melting temperature of the paramagnetic or ferromagnetic material. With this form of construction the granules of magnetic material remain in a matrix of the basic polymer material as separate elements.
Alternatively, holes may be drilled into the side walls of the body portion of the catheter by use of a laser beam. Each of these holes may be filled with an appropriate configuration of paramagnetic or ferromagnetic material.
Various paramagnetic and ferromagnetic materials may be selected for use in constructing the present invention. Paramagnetic materials such as dysprosium, gadolinium and alloy: and salts of these materials may be used, or alternative7_y, ferromagnetic materials such as iron, nickel, cobalt and alloys of these materials may be used.
The invention will be explained in greater detail in the following description with reference to the attached drawings, in which a number of examples of embodiments of the device according to the invention have been illustrated. :In the drawings, Figure 1 is a diagrammatic view of a preferred embodiment illustrating a partly cut away end of a medical catheter according to the invention;
Figure 2 is a diagrammatic view illustrating a cross section along the line .II-II of Figure 1;
Figure 3 is a diagrammatic view illustrating another embodiment of the invention;
Figure 4 is a diagrammatic view illustrating the cross-sectional view along the line IV-IV of Figure 3;
Figure 5 is a diagrammatic view illustrating yet another embodiment of a tube-l.:ike device according to the invention;
Figure 6 is a diagrarr~matic view illustrating a cross-section along the line VI-VI of Figure 5;
Figure 7 is a diagrammatic view illustrating schematically another aspect of the present invention;
Figure 8 is a diagrammatic view illustrating a wire provided with elements;
Figure 9 is a diagrammatic view illustrating a partly broken away view of an end of a catheter according to the invention, wherein the wire of Figure 8 has been employed 5 in a reinforcing layer;
Figure 10 is a diagrammatic view illustrating a cross-section along the line X-X of Figure 9;
Figure 11 is a diagrammatic view illustrating an alternative version of an embodiment corresponding to Figure 9;
Figure 12 is a diagrammatic view illustrating a cross-sectional view along the line XII-XII of Figure 11;
Figure 13 is a diagrammatic view illustrating a partly cut-away section of an end of another embodiment of the invention;
Figure 14 is a diagrammatic view illustrating a cross-section along the line XIV-XIV of Figure 13; and Figure 15 is a diagrammatic view illustrating a partly cut-away section of a~ balloon catheter in accordance with the present invention.
Referring t.o the drawings, the medical device 1 as shown in Figure 1 i.s for instance an end-section of the cylindrical tube body 2 of a catheter. The tube body 2 comprises a lumen 3 extending through the tube body 2 in a longitudinal direction.
As can be seen in Figure 1 and 2, the body 2 is made up of a number of body sections 4, 5, 6, 7 comprising paramagnetic or ferromagnetic material alternated with body sections 8 which. are made of basic polymer material.
The sections 4, 7 may for instance have been received in the basic material 8 by means of an injection moulding process. During injection moulding, the supply of basic material 8 and the supply of the material of which the sections 4-7 are made', is in that case switched on and off alternately.
The sections 4-7 provided with paramagnetic or ferromagnetic materiel have a dimension in the longitudinal direction of the basic body 2, which is substantially equal t:o the diameter thereof. Thus these sections form elements which have substantially equal.
dimensions in three directions at right angles to each other.
As a result: the disturbance of a magnetic field such as the one used with magnetic resonance imaging (MRI), caused by each of the separate elements, is at least virtually independent of the position these elements take up in this magnetic field. In other words, whether the centre lines of the elements 4-7 run parallel to the magnetic field lines or are at right-angles to them, the disturbance of the magnetic field and consequently the visibility on the sr_reen of the resultant artefact remains more or less the same.
The same is; true for the device 10 of Figure 3.
Also in this case they elements 11, 12, 13, 14 comprising the paramagnetic or ferromagnetic material are alternated with sections 15 made of basic material. The elements 11-14 have also in this case a length which is substantially equal to the diameter' of the tube body.
Additionally the elements 13, 14 which are positioned at the distal end of the device 10, have a greater density of paramagnetic or ferromagnetic material, so that they are more clearly visible on the screen of the MRI-device.
The relative distance between the elements 4-7 of the device 1 and the elements 11-14 of the device 10 is substantially such, that there is at least practically no magnetic interaction between the adjoining elements. With the embodiment of Figure 1, the relative distance between the elements is at least equal to the length and the diameter of each of t:he elements 4-7, which is to say at least equal to the outer dimensions of these imaging markers. With a suitable concentration of the paramagnetic or ferromagnetic material in the elements known as such, the relative effect on each other is very small, so that the elements function as separate elements when a nuclear magnetic resonance field is applied.
With a higher concentration of the paramagnetic or ferromagnetic material, a greater distance is required between the separate elements in order to limit the magnetic interaction between adjacent elements.
With the device 20 shown in Figure 5, the basic material 22 of the body 21 is provided with a great number of spherical element; 23 comprising paramagnetic or ferromagnetic material. Because of the spherical shape, the disturbance of the magnetic field is also independent of angle of the device within magnetic field.
The imaging marker 23 may be inserted into the basic material 22 when forming the basic body 21 by means of extrusion or injection moulding. In that case the elements are granules of a plastic material including the paramagnetic or ferromagnetic material. The magnetic material has a melt:in.g temperature which is higher than the melting temperature of the basic material 22. Thus, the elements 23 can be applied as solid particles in a flow of liquid basic: material 22. Mixing the particles 23 into the basic material 22, in which case the basic material 22 is also in granular form, can be done prior to melting the material. By mixing the different granules properly, an even di:~tribution of the elements 23 in the basic material 22 care be achieved. During the extrusion or injection moulding process, a temperature is chosen at which only the granules of basic material 22 melt. The granules 23 will remain in the basic material 22 in the form of more or less solid particles.
Figure 7 shows schematically the importance of a suitable distance between the elements 23. With the dashed and dotted line 24, an area surrounding each element 23 has been indicated, over which the magnetic field in a MRI device may be considered to be disturbed by this element 23. When the elements 23 would be positioned close to each other, so that these areas 24 would overlap to a significant degree, the two elements 23 concerned would, from an image standpoint blend together so as to form one elongated element. As can be seen in Figure 7, the elements 23 should preferably be arranged at such a distance from one another, so that there is no magnetic interaction between the adjoining elements 23.
The invention can also be employed in a suitable manner with a device according to the invention in the form of a catheter provided with a braided reinforcing layer. Such a catheter has been illustrated schematically and in a partly broken away view in Figure 9.
'the catheter 30 is made up of a first cylindrical inner layer 31, which has been extruded on a mandrel. Around this inner layer 31, a reinforcing layer of wires 33, 34 are braided. For the sake of clarity only two wires are shown in Figure 4, but in the usual manner there may be numerous reinforcing wires. Next, an outer layer 32 may be extruded around this braided reinforcing layer, so that the r~=_inforcing layer is enclosed by the inner layer 31 and the outer layer 32.
As can be seen in greater detail in Figure 8, the wire 34 of the catheter 30 is provided, at equal distances, with magnfstic elements 35 which are substantially spherical and consequently have equal dimensions in three directions at right angles to one another. The elements 35 may for instance be arranged around the wire 34 :by means of an extrusion process.
Another possibility ~L;~ to attach the elements 35 as drops of hardening materia7_ comprising the magnetic material to the wire 34. When the material has hardened, the wire 34 can be incorporated in the catheter 30.
With the embodiment of Figure 9, a satisfactory directional independency is achieved since the elements 35 are positioned on a helical path. In particular, if this helical line has a pitch angle of 45°, sections of this helical arrangement which are arranged on either side opposite each other will always be placed at right angles to one another, so that there always will be sections of the helical path which are positioned at right angles to the magnetic field.
With the device 40 of Figures 11 and 12, a braided layer has been co-extruded of which at least one wire 42 carries the magnetic elements 43 made of paramagnetic or ferromagnetic material. The device 50 of Figure 13 comprises a. tubular body 51. This tubular body 51 is made up of an inner body 52, and arranged around it, an outer layer 53. In the inner layer 52, a number of holes 54 have been formed by means of a laser device.
These holes 54 are preferably arranged on a helical path.
In the holes 54 formed, elements 56 have been fitted which either comprise or are made of paramagnetic or ferromagnetic material. The magnetic elements 56 are temporarily fixed in the holes 54, for instance by means 5 of glueing. Next t:he inner layer 52, is provided with elements 56 and is passed through an extrusion device and provided with an outer layer 53, which consequently encloses the elements 56 in the holes 54.
The device according to the invention may be any 10 medical device which is received for a shorter or longer period of time inside' the body of a patient and of which the position has to be visualized by means of MRI. Tn addition to tube-like catheters such devices may be stem s or grafts.
Another po~~sible embodiment of such a device is a balloon, such as the balloon 60 shown in Figure 15.
This balloon is arranged on a catheter, and by means of the latter, advanced to the correct position inside the body of the patient.
With the embodiment of Figure 15, the balloon 60 comprises an outer :Layer 61 and an inner layer 62, which layers 61, 62 are connected to each other by means of a layer of glue 63. The layer of glue 63 comprises in this case evenly distributed granular particles of paramagnetic or ferromagnetic material. By properly mixing the glue and the magnetic material, the elements of magnetic material formed by these granules can be enclosed in between the outer layer 61 and the inner layer 62 of the balloon 60, placed at a suitable distance from one another, so that the balloon 60, independent of the direction of the magnetic field, can be made properly visible when using twhe MRI device.
Suitable materials of which to make the elements referred to above are, for instance, paramagnetic materials, such as dysprosium and gadolinium, and alloys and salts of these materials. Ferromagnetic materia:Ls which are preferably used are iron, nickel, cobalt and alloys of these mat:e:rials. The concentration of the paramagnetic or ferromagnetic material used in the elements may vary from 0.001% in the case of strong ferromagnetic materials to 100% by weight. The concentration of the magnetic material in the elements received in the device can, as described above referring to the Figures 3 and 4, vary according to the position of these elements in thE~ device. Thus it is possible to make for instance the distal end-section of a catheter more clearly visible than :its more proximal located elements.
Claims (9)
1. A medical catheter for use with magnetic resonance imaging, comprising:
a body portion formed from a polymer material, and a plurality of cylindrical tubular magnetic resonance imaging markers including paramagnetic material, in which said imaging marker have constant outer and inner diameters and a constant longitudinal length, the markers being separated by and affixed to catheter body portions formed from a polymer material, such that the markers are spaced apart by a sufficient distance that there is substantially no magnetic interaction between the markers when an image of the catheter is viewed with magnetic resonance imaging equipment, wherein the length of each marker is selected such that the image of each marker has substantially the same maximum outer dimensions and is of substantially the same length and width when the catheter is viewed by magnetic resonance imaging equipment along and x-axis, a y-axis and a z-axis, in which such axes are each at right angles to each other.
a body portion formed from a polymer material, and a plurality of cylindrical tubular magnetic resonance imaging markers including paramagnetic material, in which said imaging marker have constant outer and inner diameters and a constant longitudinal length, the markers being separated by and affixed to catheter body portions formed from a polymer material, such that the markers are spaced apart by a sufficient distance that there is substantially no magnetic interaction between the markers when an image of the catheter is viewed with magnetic resonance imaging equipment, wherein the length of each marker is selected such that the image of each marker has substantially the same maximum outer dimensions and is of substantially the same length and width when the catheter is viewed by magnetic resonance imaging equipment along and x-axis, a y-axis and a z-axis, in which such axes are each at right angles to each other.
2. The medical catheter as defined in claim 1, wherein the medical device includes at least two magnetic resonance imaging markers and said markers are spaced apart at a distance from each other so that there is substantially no magnetic interaction between the marker when the device is irradiated by nuclear magnetic radiation.
3. The medical catheter as defined in claim 2, wherein the spacing between the imaging markers is equal to or greater than the outer dimensions of the imaging marker.
4. The medical catheter as defined in claim 3, wherein the spacing between the imaging markers is equal to or greater than twice the outer dimensions of the imaging markers.
5. The medical catheter as defined in claim 4, wherein the imaging markers are of a length along the longitudianl axis of the catheter substantially equal to such outer diameter of the catheter.
6. An intravascular medical catheter having proximal and distal ends for use with magnetic resonance imaging, comprising:
a body portion near the catheter distal end formed of a polymer material, the body portion defining an x-axis, a y-axis, and a z-axis which are mutually orthogonal; and a plurality of cylindrical tubular markers including paramagnetic material. visible under magnetic resonance imaging, wherein the markers have constant outer and inner diameters and a constant longitudinal length, the markers being separated by arid affixed to catheter body portions formed from a polymer material, wherein the length of each marker is selected such that each marker has substantially the same maximum outer dimensions when the body portion is viewed with magnetic resonance imaging equipment along the x-axis, y-axis, and z-axis successively, whereby each marker provides substantially the same size image regardless of perspective.
a body portion near the catheter distal end formed of a polymer material, the body portion defining an x-axis, a y-axis, and a z-axis which are mutually orthogonal; and a plurality of cylindrical tubular markers including paramagnetic material. visible under magnetic resonance imaging, wherein the markers have constant outer and inner diameters and a constant longitudinal length, the markers being separated by arid affixed to catheter body portions formed from a polymer material, wherein the length of each marker is selected such that each marker has substantially the same maximum outer dimensions when the body portion is viewed with magnetic resonance imaging equipment along the x-axis, y-axis, and z-axis successively, whereby each marker provides substantially the same size image regardless of perspective.
7. The medical catheter as defined in claim 6, wherein the image of each marker is of substantially the same length and width when the body portion is viewed by magnetic resonance imaging equipment along and x-axis, a y-axis, in which such axes are each at right angles to each other.
8. The medical catheter as defined in claim 7, wherein the markers are spaced apart at a sufficient distance from each other so that there is substantially no magnetic interaction between the markers when the catheter is viewed with magnetic resonance imaging equipment.
9. A medical catheter for use with magnetic resonance imaging, comprising:
a body portion formed from a polymer material, a plurality of magnetic resonance imaging markers including paramagnetic material, said imaging markers each having preselected dimensions such that an image of the catheter has substantially the same maximum outer dimensions and is of substantially the same length and width, when the image of the catheter is viewed with magnetic resonance imaging equipment along each of three orthogonal axes, wherein said markers are spaced apart at a sufficient distance from each other so that there is substantially no magnetic interaction between the markers when an image of the catheter is viewed with magnetic resonance imaging equipment.
a body portion formed from a polymer material, a plurality of magnetic resonance imaging markers including paramagnetic material, said imaging markers each having preselected dimensions such that an image of the catheter has substantially the same maximum outer dimensions and is of substantially the same length and width, when the image of the catheter is viewed with magnetic resonance imaging equipment along each of three orthogonal axes, wherein said markers are spaced apart at a sufficient distance from each other so that there is substantially no magnetic interaction between the markers when an image of the catheter is viewed with magnetic resonance imaging equipment.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL1001736A NL1001736C2 (en) | 1995-11-23 | 1995-11-23 | Medical device visible in magnetic resonance imaging (MRI). |
| NL1001736 | 1995-11-23 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2190900A1 CA2190900A1 (en) | 1997-05-24 |
| CA2190900C true CA2190900C (en) | 2006-02-07 |
Family
ID=19761912
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002190900A Expired - Lifetime CA2190900C (en) | 1995-11-23 | 1996-11-21 | Medical device visible when using magnetic resonance imaging |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5908410A (en) |
| EP (1) | EP0775500B1 (en) |
| CA (1) | CA2190900C (en) |
| DE (1) | DE69631408T2 (en) |
| NL (1) | NL1001736C2 (en) |
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-
1995
- 1995-11-23 NL NL1001736A patent/NL1001736C2/en not_active IP Right Cessation
-
1996
- 1996-10-21 US US08/734,273 patent/US5908410A/en not_active Expired - Lifetime
- 1996-11-21 CA CA002190900A patent/CA2190900C/en not_active Expired - Lifetime
- 1996-11-22 EP EP96203274A patent/EP0775500B1/en not_active Expired - Lifetime
- 1996-11-22 DE DE69631408T patent/DE69631408T2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| EP0775500A1 (en) | 1997-05-28 |
| US5908410A (en) | 1999-06-01 |
| DE69631408T2 (en) | 2004-10-14 |
| EP0775500B1 (en) | 2004-01-28 |
| DE69631408D1 (en) | 2004-03-04 |
| NL1001736C2 (en) | 1997-05-27 |
| CA2190900A1 (en) | 1997-05-24 |
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