U.S. patent application number 10/701223 was filed with the patent office on 2004-05-13 for radiopaque surgical implement.
This patent application is currently assigned to Scimed Life Systems, Inc.. Invention is credited to Mraz, Dion, Weaver, Timothy J..
Application Number | 20040092818 10/701223 |
Document ID | / |
Family ID | 24864603 |
Filed Date | 2004-05-13 |
United States Patent
Application |
20040092818 |
Kind Code |
A1 |
Weaver, Timothy J. ; et
al. |
May 13, 2004 |
Radiopaque surgical implement
Abstract
X-ray imageable articles, for instance surgical implements or
parts therefore which are used in minimally invasive surgical
procedures, may be prepared by a process including the steps of:
(a) preparing a mixture composition comprising: i) radiolucent
particulate material selected from ceramic materials, metallurgic
materials, and combinations thereof and having a particulate size
of no more than 40 microns, ii) radiopaque particulate material
selected from ceramic materials, metallurgic materials, and
combinations thereof and having a particulate size of no more than
40 microns, and (iii) at least one polymeric binder material; (b)
injection molding the mixture composition into a preform; (c)
optionally removing the binder material from the preform; and (d)
sintering the preform.
Inventors: |
Weaver, Timothy J.; (Duvall,
WA) ; Mraz, Dion; (Mercer Island, WA) |
Correspondence
Address: |
VIDAS, ARRETT & STEINKRAUS, P.A.
6109 BLUE CIRCLE DRIVE
SUITE 2000
MINNETONKA
MN
55343-9185
US
|
Assignee: |
Scimed Life Systems, Inc.
Maple Grove
MN
|
Family ID: |
24864603 |
Appl. No.: |
10/701223 |
Filed: |
November 4, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10701223 |
Nov 4, 2003 |
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09713064 |
Nov 15, 2000 |
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6641776 |
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Current U.S.
Class: |
600/431 ;
424/9.42; 623/1.34 |
Current CPC
Class: |
A61L 29/18 20130101;
A61L 31/18 20130101 |
Class at
Publication: |
600/431 ;
623/001.34; 424/009.42 |
International
Class: |
A61K 049/04; A61F
002/06 |
Claims
1. A method for preparing an X-ray imageable article comprising:
(a) preparing a mixture composition comprising: i) radiolucent
particulate material selected from ceramic materials, metallurgic
materials, and combinations thereof and having an average
particulate size of no more than 40 microns, ii) radiopaque
particulate material selected from ceramic materials, metallurgic
materials, and combinations thereof and having an average
particulate size of no more than 40 microns, and (iii) at least one
polymeric binder material; (b) injection molding the mixture
composition into a preform; (c) optionally removing the binder
material from the preform; and (d) sintering the preform.
2. A method as in claim 1 wherein said article is a surgical
implement or component thereof, said implement adapted to be
disposed on a catheter and conveyed thereon a remote site within
the body and operated at such site to perform a surgical
procedure.
3. A method as in claim 1 wherein said radiolucent material is
selected from the group consisting of alumina, aluminum nitride,
silica, silicon, silicon carbide, silicon nitride, sialon,
zirconia, zirconium nitride, zirconium carbide, zirconium boride,
titania, titanium nitride, titanium carbide, barium titanate,
titanium boride, boron nitride, boron carbide, magnesium oxide,
calcium oxide, stainless steel, iron, nickel, titanium, nitinol,
and metallic oxides which can be converted to metals when sintered
in a reducing environment, and combinations thereof.
4. A method as in claim 1 wherein said radiopaque material is
selected from the group consisting of tungsten carbide, tungsten
boride, the metals platinum, tantalum, iridium, tungsten, rhenium
and gold, alloys of said metals, and combinations thereof.
5. A method as in claim 1 wherein the radiopaque material (ii)
constitutes at least 2% and no more than about 75% by volume of the
total volume of the components (i) and (ii).
6. A method as in claim 1 wherein the radiolucent material is
selected from the group consisting of alumina, zirconia and
stainless steel and the radiopaque material is selected from the
group consisting of platinum, tungsten, rhenium and tantalum, and
the radiopaque material constitutes from about 10 to about 50% by
volume of the total volume of the components (i) and (ii).
7. A method as in claim 1 wherein the binder component (iii) is
selected from the group consisting of polyolefins; olefin
copolymers such as ethylene vinyl acetate copolymers;
poly(meth)acrylates; styrene group resins; polyvinyl chloride;
polyamides; polyesters; polyethers; polyacetals; and waxes.
8. A method as in claim 1 wherein the binder component (iii) is
employed in said mixture composition in an amount of from about 2%
to about 30% by weight thereof.
9. A method as in claim 1 wherein the binder removal step c) is
preformed.
10. An article comprising a sintered mixture of at least two
inorganic powder materials at least one of which is a radiolucent
and at least one of which is radiopaque.
11. A medical device comprising an article as in claim 10.
12. A medical device as in claim 11 wherein said device comprises a
catheter and said article is a surgical implement which can be
carried on the catheter to a remote site within the body.
13. A medical device as in claim 12 wherein said radiolucent
material is selected from the group consisting of alumina, aluminum
nitride, silica, silicon, silicon carbide, silicon nitride, sialon,
zirconia, zirconium nitride, zirconium carbide, zirconium boride,
titania, titanium nitride, titanium carbide, barium titanate,
titanium boride, boron nitride, boron carbide, magnesium oxide,
calcium oxide, stainless steel, iron, nickel, titanium, nitinol,
and metallic oxides which can be converted to metals when sintered
in a reducing environment, and combinations thereof.
14. A medical device as in claim 12 wherein said radiopaque
material is selected from the group consisting of tungsten carbide,
tungsten boride, the metals platinum, tantalum, iridium, tungsten,
rhenium and gold, alloys of said metals, and combinations
thereof.
15. A medical device as in claim 12 wherein the radiopaque material
constitutes at least 2% and no more than about 75% by volume of the
total volume of the radiolucent and the radiopaque materials.
16. A medical device as in claim 12 wherein the radiolucent
material is selected from the group consisting of alumina, zirconia
and stainless steel and the radiopaque material is selected from
the group consisting of platinum, tungsten, rhenium and tantalum,
and the radiopaque material constitutes from about 10 to about 50%
by volume of the total volume of the radiolucent and the radiopaque
materials.
17. A composition useful for preparing radiopaque components of a
medical device structure, the composition comprising a mixture of
i) radiolucent particulate material selected from ceramic
materials, metallurgic materials, and combinations thereof and
having an average particulate size of no more than 40 microns, ii)
radiopaque particulate material selected from ceramic materials,
metallurgic materials, and combinations thereof and having an
average particulate size of no more than 40 microns, and (iii) at
least one polymeric binder material.
18. A composition as in claim 17 wherein: the radiolucent material
is selected from the group consisting of alumina, aluminum nitride,
silica, silicon, silicon carbide, silicon nitride, sialon,
zirconia, zirconium nitride, zirconium carbide, zirconium boride,
titania, titanium nitride, titanium carbide, barium titanate,
titanium boride, boron nitride, boron carbide, magnesium oxide,
calcium oxide, stainless steel, iron, nickel, titanium, nitinol,
and metallic oxides which can be converted to metals when sintered
in a reducing environment, and combinations thereof; the radiopaque
material is selected from the group consisting of tungsten carbide,
tungsten boride, the metals platinum, tantalum, iridium, tungsten,
rhenium and gold, alloys of said metals, and combinations thereof;
the radiopaque material constitutes at least 2% and no more than
about 75% by volume of the total volume of the radiolucent and the
radiopaque materials; and. the binder material is present in said
composition in an amount of from about 2% to about 30% by weight
thereof.
19. A composition as in claim 17 wherein the radiolucent material
is selected from the group consisting of alumina, zirconia and
stainless steel and the radiopaque material is selected from the
group consisting of platinum, tungsten, rhenium and tantalum, and
the radiopaque material constitutes from about 10 to about 50% by
volume of the total volume of the radiolucent and the radiopaque
materials.
20. A composition as in claim 17 wherein the average particle sizes
of the radiolucent and radiopaque materials are from about 0.5 to
about 10 micrometers.
21. A composition as in claim 17 wherein the radiopaque material
has a melting point which is greater than or equal to the melting
point of the radiolucent material.
22. A surgical method comprising conveying a surgical implement via
a catheter to a remote site within the body, using said implement
to perform a surgical procedure at said site and observing the
implement fluoroscopically during at least a portion of the time it
is in the body, wherein the implement comprises an article as in
claim 10.
23. A surgical method as in claim 22 wherein the radiolucent and
the radiopaque powder materials are present in relative amounts
which renders the article bright enough during X-ray fluoroscopy to
be seen using an X-ray intensity which allows visualization of the
surrounding tissue, but dim enough to be seen through.
24. A method as in claim 2 wherein the radiolucent and the
radiopaque powder materials are present in relative amounts which
renders the article, when in the body, bright enough during X-ray
fluoroscopy to be seen using an X-ray intensity which allows
visualization of the surrounding tissue, but dim enough to be seen
through.
25 A medical device as in claim 12 wherein the radiolucent and the
radiopaque powder materials are present in relative amounts which
renders the article, when in the body, bright enough during X-ray
fluoroscopy to be seen using an X-ray intensity which allows
visualization of the surrounding tissue, but dim enough to be seen
through.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to medical devices which are inserted
into the body and located by X-ray imaging.
[0002] Various types of minimally invasive surgical techniques have
been developed in recent years in which catheters or similar
devices are used to convey a operative implement through a body
passage, including such passages as the blood vessels,
gastrointestinal tract, urethral and urethral tracts, bronchial and
esophageal tracts, to a specific location where the implement is
operatively employed or delivered. Catheters are used to perform
balloon angioplasty, to deliver and lodge stent devices, to deliver
drugs, to abrade or volatilize lesions, to remove temporary,
misplaced or dislodged stents, and the like. For such activities,
X-ray imaging is often used to follow the catheter or the operative
implement as it traverses the body channel and/or to monitor the
actual employment or deployment of the implement.
[0003] For materials which are transparent to X-ray, or are only
weakly radiopaque, it has been conventional to provide radiopaque
marker bands, coatings or laminates of more intensely radiopaque
materials on the devices or implements in order to achieve the
necessary contrast for a readily observable image.
[0004] A number of the implements, used or delivered by such
techniques, or parts thereof may be made of metal or ceramic
materials. Traditionally such implements are, or are made up of,
small complex machined parts. Stents are an example of such an
implement which is typically made by machining metal.
[0005] A technique which is known for manufacturing metal and
ceramic parts utilizes injection molding and sintering of composite
formulations. This technique, designated "CIM" for ceramic articles
and "MIM" for metal articles utilizes formulations which are
mixtures of a resinous binder material and a very fine powder of
the respective ceramic or metal material, which is injection molded
to produce a desired shaped article, the molded article typically
being somewhat larger than the desired size. The binder is then
typically removed by extraction, heating, or both, leaving a shaped
structure of the powder material. This structure is sintered to
form the final article, typically shrinking by a reproducible
amount.
[0006] Similar products can be prepared from combining ceramic
materials with metallurgic materials to form what is known as a
"cermet."
[0007] A porous stent formed by a powdered metal sintering process
is disclosed in U.S. Pat. No. 5,972,027, incorporated herein by
reference in its entirety. A perfulsion tip for an ablation
catheter is described in U.S. 6,017,338, incorporated herein by
reference in its entirety.
SUMMARY OF THE INVENTION
[0008] The present invention is directed to articles which can be
made using a CIM or MIM process, preferably articles which are, or
are part, of surgical implement structures such as catheters,
forcepts, stents, perfusion heads, electrodes, and the like used in
minimally invasive surgical procedures and. The invention also
relates to CIM or MIM processes for preparing such implements, or
parts thereof, in which the ceramic or metal powder material used
to form the article comprises a radiolucent material and a
radiopaque material.
[0009] In a first aspect of the present invention there is provided
a method for preparing an X-ray imageable article comprising:
[0010] (a) preparing a mixture composition comprising:
[0011] i) radiolucent particulate material selected from ceramic
materials, metallurgic materials, and combinations thereof and
having an average particulate size of no more than 40 microns,
[0012] ii) radiopaque particulate material selected from ceramic
materials, metallurgic materials, and combinations thereof and
having an average particulate size of no more than 40 microns,
and
[0013] (iii) at least one polymeric binder material;
[0014] (b) injection molding the mixture composition into a
preform;
[0015] (c) optionally removing the binder material from the
preform; and
[0016] (d) sintering the preform.
[0017] Articles, especially surgical implements comprising an
article composed of a sintered mixture of radiolucent and
radiopaque powders as described herein, and medical devices
comprising such implements are other aspects of the invention.
[0018] A further aspect of the invention is a surgical method in
which a surgical implement as described herein is carried via a
catheter to a remote site within the body and used in performing a
surgical procedure, wherein the article of the invention is
observed fluoroscopically during at least a portion of the time it
is in the body.
[0019] Still further aspects of the invention are described in the
detailed description below and in the claims.
BRIEF DESCRIPTION OF THE FIGURES
[0020] FIG. 2 is an orthagonal view of a ceramic tip for an RF-PMR
catheter fashioned in accordance with the present invention.
[0021] FIG. 1 is a perspective view of a single jaw of a biopsy
forceps fashioned in accordance with the present invention.
[0022] FIG. 3 is a perspective fragmentary view of a stent
fashioned in accordance with the present invention.
DETAILED DESCRIPTION
[0023] As noted above the invention is preferably practiced to
prepare articles which are, or are components of surgical
implements adapted for delivery and operation at a remote site
within the body on a catheter.
[0024] According to the invention the subject article is composed
of a mixture of at least two inorganic ceramic or metallurgic
materials, one of which is radiolucent, (i.e. invisible or only
weakly visible fluoroscopically), and the second of which is
radiopaque (readily visible fluoroscopically).
[0025] Particulate materials suitable for the radiolucent inorganic
material making up the component (i) of the moldable compositions
include:
[0026] ceramic materials such as alumina, aluminum nitride, silica,
silicon, silicon carbide, silicon nitride, sialon, zirconia,
zirconium nitride, zirconium carbide, zirconium boride, titania,
titanium nitride, titanium carbide, barium titanate, titanium
boride, boron nitride, boron carbide, magnesium oxide, calcium
oxide, and the like, and combinations thereof; and
[0027] metallurigic materials including metals, and mixtures or
alloys thereof such as stainless steel, iron, nickel, titanium,
nitinol, and metallic oxides which can be converted to metals when
sintered in a reducing environment, and combinations thereof.
[0028] Combinations of such inorganic radiolucent ceramic and
metallurgic materials may also be employed as the component (i).
Preferred radiolucent materials include alumina, zirconia, and 17-4
PH, MP35N, 316 LVM, and 304V stainless steels.
[0029] Particulate materials suitable for the inorganic radiopaque
material making up the component (ii) of the moldable compositions
include:
[0030] ceramic materials such as tungsten carbide, and tungsten
boride, and
[0031] metallurgic materials such as platinum, tantalum, iridium,
tungsten, rhenium gold and alloys of such metals.
[0032] Combinations of such inorganic radiopaque ceramic and
metallurgic materials may also be employed as the component (ii).
Preferred radiopaque materials include platinium, tungsten, rhenium
and tantalum.
[0033] The morphology of the inorganic particulate materials (i)
and (ii) is not critical but is preferably approximately spherical.
The particle sizes of the materials will both be within the range
suitable for forming sintered articles, suitably an average of
about 40 micrometers (microns) or less, more preferably an average
of from about 0.5 to about 10 micrometers in diameter.
[0034] The ratio of the radiolucent and radiopaque materials may
vary widely, depending on the desired structural properties and
radiopacity of the finished article. Generally the radiopaque
material (ii) will constitute at least 2% and no more than about
75% by volume of the total volume of the components (i) and (ii).
More typically, structural and/or cost factors will favor the
radiolucent component, so that the radiopaque component will
constitute no more than 50% by volume and preferably no more than
about 35% by volume of the two. On the other hand, if too little of
the radiopaque component is employed the fluoroscopic visibility of
the implement may not be adequately enhanced. Consequently it will
generally be desirable to employ at least 5% and often 10% or more
of the radiopaque component, based on the total volume of these two
components.
[0035] Also, it is generally preferred that the radiopaque material
have a melting point which is not substantially lower than the
radiolucent material so that fluidization of the radiopaque
material does not occur before the radiolucent material reaches,
sintering temperature. More preferably the radiopaque material has
a melting point which is about the same or is even higher than that
of the radiolucent material.
[0036] The third component of the composition is a binder material
(iii). Any material suitable as a binder material for CIM or MIM
processes may be used. Exemplary materials include polyolefins,
such as polyethylene and propylene; olefin copolymers such as
ethylene vinyl acetate copolymers; poly(meth)acrylates including
polymethyl methacrylate, polybutyl methacrylate and the like;
polystyrene and other styrene group resins; polyvinyl chloride;
polyamides; polyesters; polyethers; polyacetals; various types of
wax, including paraffin; and the like. Exemplary binders are
described in EP-A-0 444 475, EP-A-0 446 708 and EP-A-0 444 475,
incorporated herein by reference.
[0037] The binding agents are employed in conventional amounts,
generally from about 2% to about 30% by weight of the injection
moldable composition. More preferably the binder will be employed
in an amount of from about 4 to about 15% by weight of the
composition. Generally lower amounts of binder will be preferred to
minimize shrinkage during sintering. However, with very complex
shapes, if the shrinkage is carefully controlled to give good
reproducibility and avoid shape distortion, high shrinkage may be
advantage in allowing larger molds to be used to produce the
preform.
[0038] In addition to the three components described above, various
additives known in the art may be added in conventional to the
moldable composition. Examples of such additives include
plasticizing agents, lubricating agents, antioxidants, degreasing
promotion agents, and surfactants.
[0039] The composition of the inorganic powders (i) and (ii), the
binder (iii) and any other additives are suitably blended in a
kneading machine above the melting point of the binder and the
kneaded product pelletized before use. Alternatively any other
conventional mixing technique may be used and/or the blended
mixture may be used without pelletization.
[0040] In the second step of the inventive process the composition
produced as described above is injection molded into a compacted
preform. The dimensions of the mold are set taking into account the
shrinkage that will occur from the later sintering step. Typical
molding conditions will provide the composition to the mold at a
temperature above the melting point of the binder, typically from
about 130-200.degree. C. and at injection pressure of from about
30,000 to as high as 200,000 kPa. The mold temperature suitably
will be below that of the composition, and below the glass
transition temperature of the binder, typically from about
5.degree. C. to about 50.degree. C. Alternatively the mold may be
at a higher temperature when the composition is injected and then
subsequently cooled. The preform produced in this step is then
removed from the mold.
[0041] After the preform is removed from the mold a binder
extraction process may be performed on the preform. In forming
sintered parts it is not always necessary to remove the binder as
it may vaporize/decompose during sintering. However, better
dimensional stability results are often obtained if the binder is
removed before the preform is sintered. Known binder removal
methods include solvent extraction, thermal
decomposition/vaporization at a temperature below the sintering
temperature, and chemical decompositon, for instance decomposition
of polyacetal resins by exposure to an acidic gas at elevated
temperature. Combinations of such removal methods may also be
employed. Suitable conditions for such binder extractions are known
in the art.
[0042] Next, the preform, either as obtained directly from the mold
or after binder extraction is heated under conditions suitable for
sintering the inorganic particles of the components (i) and (ii).
Typical conditions will be a temperature of from about 400.degree.
C. to about 1700.degree. C. for about 10 to about 30 hours,
although higher temperatures and longer or shorter times may be
suitable for some articles. Typically the sintering step will be
conducted in a non-oxidizing atmosphere, for example, in argon gas
or other inactive gases, under a vacuum or reduced pressure
conditions. In some instances, for instance where the metallurgic
material is a metal oxide, hydrogen will be provided to accomplish
a reduction of such oxide to the metal during sintering. A
reduction process adaptable to the present invention is described
in U.S. Pat. No. 6,080,808, incorporated herein by reference.
[0043] In some cases surface hardness or other desirable properties
may be imparted to the implement by providing an atmosphere
containing one or more gas(es) containing least one of C, O or N
during a portion of the sintering time. Such gases may be selected
from air, O.sub.2, CO.sub.2, CO, N.sub.2, methane, acetylene,
propane and mixtures thereof.
[0044] After sintering, the formed article may be subjected to any
necessary finishing steps. For example, lubricity coatings may be
applied, finishing machining may be performed, and/or surface
processing may be performed such as shot blasting, honing,
grinding, etching, wet plating, vacuum evaporation, ion plating,
spattering, CVD, and the like.
[0045] The powder injection molding method described above allows
complicated shapes to be formed monolithically with a tailored
radiopacity in a simple and repeatable high production rate
process.
[0046] Through adjustment of types of binding agents, added
amounts, binder extraction conditions, and sintering conditions,
various material properties of the inventive implement can be
controlled or set. Examples of such properties include the
composition of the surface layer, the pore diameter, and the number
of pores.
[0047] The invention permits the radiographic contrast range of the
article to be tailored to permit ready visualization, without
creating an X-ray artifact which masks the surrounding vessel and
tissue. This is especially important in surgical techniques
practiced via catheters, since, once the article has been delivered
to the site of treatment it is often necessary to visualize
surrounding tissue in order to successfully perform a procedure.
Still further, in the case of an implement, such as a stent, which
is left in the body as a result of the procedure, it is important
to monitor the tissue condition through the stent subsequent to
placement to verify vessel patentcy. For this reason, the implement
needs to be bright enough during X-ray fluoroscopy to be seen using
an X-ray intensity which allows visualization of the surrounding
tissue, but dim enough to be seen through.
[0048] Referring now to the Figures, there is shown in FIG. 1 a
single jaw 10 of a two-jaw biopsy forceps which may be mounted on a
catheter and transported via the vascular system from a remote
location to a diseased or transplanted heart and at that location
deployed and operated to grab a tissue sample. The forceps is then
removed from the body and the tissue sample retrieved for
inspection. Such forceps jaws (T-Rex.RTM.) are now conventionally
made by machining a blank of a medical grade stainless steel. When
made in accordance with the present invention from a mixture of
powders of a medical grade stainless steel and a radiopaque metal
such as platinum or tungsten, the delivery and removal of the
forceps, as well as its operation at the heart site, may be more
easily monitored than if the forceps jaws are made only from
machined stainless steel.
[0049] FIG. 2 shows a perspective view of a ceramic tip 20 for a
PMR catheter, conventionally made of alumina by a CIM process. The
tip serves an an insulator and mechanical stop for an RF electrode
array used to treat myocardial infarction. When made in accordance
with the present invention from a mixture of powders of a medical
grade alumina and tungsten or rhenium, the delivery and removal of
the catheter may be easily monitored without the necessity of
providing radiopaque marker bands or the like. Thus the
manufacturing process is simplified and components presenting
potential bonding issues are eliminated.
[0050] FIG. 3 shows a porous drug delivery stent 30 of the type
described in U.S. Pat. No. 5,972,027, made from sintered stainless
steel powder. When made in accordance with the present invention
from a mixture of powders of a medical grade stainless steel and a
radiopaque metal such as tantalum, platinum or tungsten, the
delivery of the stent, and its functioning to maintain vessel
patency may be more easily monitored than if the stent is made only
from sintered stainless steel powder.
[0051] While the invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiments, it is to be understood that the invention is not to be
limited to the disclosed embodiments but, on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
[0052] The above examples and disclosure are intended to be
illustrative and not exhaustive. These examples and description
will suggest many variations and alternatives to one of ordinary
skill in this art. All these alternatives and variations are
intended to be included within the scope of the attached claims.
Those familiar with the art may recognize other equivalents to the
specific embodiments described herein which equivalents are also
intended to be encompassed by the claims attached hereto. Further,
the particular features presented in the dependent claims below can
be combined with each other in other manners within the scope of
the invention such that the invention should be recognized as also
specifically directed to other embodiments having any other
possible combination of the features of the dependent claims.
* * * * *