Note: Descriptions are shown in the official language in which they were submitted.
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A MINIMALLY INVASIVE MEDICAL DEVICE
FOR PROVIDING A RADIATION TREATMENT
Technical Field
This invention relates to minimally invasive medical
devices and, in particular, a minimally invasive medical device
having an expandable distal portion for providing a radiation
treatment in a body passageway or vessel.
Backaround of the Invention
Occlusion of the coronary arteries can decrease blood
flow to the extent that a myocardial infarction occurs. This
typically occurs due to cholesterol or plaque depositing on the
vessel walls and subsequently building up to occlude the vessel.
As a result, several minimally invasive procedures such as
balloon angioplasty or laser ablation are utilized to reopen or
enlarge the lumen of the vessel. A problem with these
procedures is that abrasion or dissection of the vessel wall may
occur during the therapeutic procedure to reopen or enlarge the
lumen of the vessel. As a result, thrombi formation and
occlusion of the vessel lumen may also occur.
In addition to balloon angioplasty or laser ablation
procedures, a coronary stmt is typically positioned in the
treated vessel to maintain the patency of the vessel. A problem
with the use of a stmt is that smooth muscle proliferates or
intimal hyperplasia occurs in response to the presence of the
stmt in the vessel. As a result, restenosis of the vessel
typically occurs within a period of six months.
An approach to decreasing smooth muscle proliferation or
intimal hyperplasia is the use of a stmt with a radioisotope
source for irradiating tissue at the stmt site. The
radioisotope source is contained in the surface coating of the
stmt or contained in the metal alloy that forms the stmt. In
use, the stmt is embedded into the plaque on a blood vessel
wall. A problem with the use of this radioactive stmt is that
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the stent is a permanent implant in the blood vessel. As a
result, smooth muscle proliferation or intimal hyperplasia may
occur in response to the presence of the stmt in the vessel
over the entire life of a patient, causing chronic restenosis
of the vessel. A limitation of the use of this stmt is that
the radiation exposure to the stmt site is controlled by the
half-life of the radioisotope. Once implanted, the radiation
dosage of the stent cannot be increased or decreased in response
to the changing needs of the patient. Not only are these
problems associated with the coronary vessels but are applicable
to other parts of the vascular system, such as the occlusion of
the femoral or iliac vessels.
Summarv of the Invention
The foregoing problems are solved and a technical
advance is achieved in an illustrative minimally invasive
medical device for providing a radiation treatment in a body
passageway such as a vessel in the vascular system. The
preferred minimally invasive medical device includes an outer
sheath with an inner elongated member having an expandable
distal portion slidably disposed in the passage of the outer
sheath. The expandable distal portion also includes a radiation
source for advantageously providing a controlled radiation
treatment to a blood vessel.
The expandable distal portion includes spring wires
looped about a distal end of the inner elongated member for
expanding and contacting the wall of the blood vessel when
extended from the distal end of the outer sheath. The radiation
source comprises a radioactive material such as iridium and the
like, which in the preferred embodiment is combined with the
spring wires to form radioactive metal alloy spring wires. In
another aspect, the radiation source forms a radioactive surface
coating or layer disposed on the outer surface of the spring
wires. In yet another aspect, the radiation source comprises
radioactive material sleeves attached to the spring wires.
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In another aspect of the invention, the medical device
includes a wire guide extendable through the distal portion of
the expandable spring wire basket. To advantageously affect a
greater mass of radioactive material, the spring wires are
helically shaped. The medical device also includes a coil
extending distally from and rotatable with respect to the spring
wire arrangement, frame, or basket. To minimize trauma to the
vessel wall, the coil has a distal end with a greater
flexibility than that of the proximal end and further includes a
tapered mandril positioned longitudinally within the coil.
In yet another aspect of the invention, the inner elongated
member includes a catheter with the expandable distal portion
including an inflatable balloon. Advantageously, the radiation
source comprises a radioactive fluid for inflating the balloon
and treating the affected blood vessel. A second lumen is also
included in the catheter for blood to perfuse therethrough.
The radiation dosage is preferably selected to be of a
magnitude such that within a reasonable exposure time, for
example 5 to 10 minutes or possibly even longer, the exposure of
the wall of the vessel is sufficient that the wall moves away
from the enlargement means, i.e., a balloon or a wire frame as
shown in FIGs. 1 to 11 except FIG 9. Furthermore, the wall is
expanded further by the radiation exposure. The strength of the
radiation is thus predetermined.
In accordance with one aspect of the present invention
there is provided a minimally invasive medical device (10, 23,
31, 40, 41, 46) for providing a radiation treatment, comprising:
an outer sheath (15, 61) having a distal end (56), a proximal
end (58), and a passage (59) extending longitudinally therein;
and an inner elongated member (55) having an expandable distal
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portion (11, 32) and a proximal portion (17) slidably disposed
in said passage of said outer sheath, said proximal portion
extending from said proximal end of said outer sheath for
extending said expandable distal portion from said distal end of
said outer sheath, said expandable distal portion having an
expanded condition when extended from said distal end of said
outer sheath, said expandable distal portion also including a
radiation source (18, 48).
In accordance with another aspect of the present invention
there is provided a minimally invasive medical device for
providing a radiation treatment, comprising: an outer sheath
having a distal end, a proximal end, and a passage extending
longitudinally therein; first and second spring wires positioned
in said passage of said outer sheath and looped about a distal
end thereof and forming a basket, said basket assuming a
collapsed condition when positioned in said passage of said
outer sheath, said basket assuming an expanded condition when
extended from said distal end of said outer sheath; and a
radiation source disposed about said spring wires.
In accordance with yet another aspect of the present
invention there is provided a minimally invasive medical device
for providing a radiation treatment, comprising: an outer
polytetrafluoroethylene sheath having a distal end, a proximal
end, and a passage extending longitudinally therein; first and
second stainless steel spring wires extending through and
slidably positioned in said passage of said outer sheath and
looped about a distal end thereof to form a basket, said basket
assuming a collapsed condition when positioned in said outer
sheath, said basket assuming an expanded condition when extended
from said distal end of said outer sheath, said first and second
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stainless steel spring wires having a proximal end extending
from said proximal end of said outer sheath to form a handle for
slidably positioning said basket in and out of said passage of
said outer sheath; and an iridium material combined with said
first and second stainless steel wires to form first and second
radioactive metal alloy spring wires.
In accordance with still yet another aspect of the present
invention there is provided a minimally invasive medical
apparatus for providing radiation treatment to the wall of a
passage in a patient, said apparatus comprising: a tube or
sheath having a distal end, a proximal end, and a passage
extending longitudinally therein: an inner elongated member
having an expandable distal portion and a proximal portion
slidably disposed relative to said passage, said proximal
portion extending from said proximal end of said outer sheath
for extending and withdrawing said expandable distal portion
from and to said distal end of said outer sheath, said
expandable distal portion having an expanded condition when
extended from said distal end of said outer sheath in order to
expand the said wall of the patient, and means for providing
radiation at said expandable distal portion in order to
irradiate the expanded wall.
Brief Description of the Drawings
FIG. 1 depicts a preferred embodiment of the minimally
invasive medical device of the present invention;
FIG. 2 depicts an enlarged cross-sectional view of the
medical device of FIG. 1 taken along the line 2-2;
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FIGs. 3-5 depict the medical device of FIG. 1 variously
positioned in a coronary artery; and
FIGS. 6-11 depict various other aspects of the minimally
invasive medical device of the present invention.
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Detailed Descr~tion
Depicted in FIG. 1 is a preferred embodiment of a
minimally invasive medical device 10 including an expandable
wire arrangement, frame, or basket 54, for providing a selective
and controlled radiation treatment in a body passageway. This
minimally invasive medical device has particular application as
a percutaneously inserted intravascular device for controllably
providing a therapeutic radiation dosage to an affected area of
a coronary vessel that is deemed likely to experience
restenosis. Restenosis typically occurs after a procedure to
open or enlarge the vessel, such as balloon angioplasty, laser
ablation, or stmt placement .
Device 10 includes an outer sheath or tube 15 with inner
elongated member 55, which is longitudinally and slidably
disposed through passage 59 of the outer sheath or tube. Inner
elongated member includes an expandable distal portion 11 such
as the expandable wire arrangement, frame, or basket 54, which
in an expanded condition extends from distal end 56 of the outer
sheath. The stranded wire basket is formed from commercially
available spring wires 12 and 13 of, for example, stainless
steel, platinum or tantalum, that are looped about distal end
14 of the inner elongated member. The expandable wire
arrangement, frame, or basket 54 can alternatively be provided
with central rod or wire attached to the distal end of the
arrangement. The rod can be pulled or pushed relative to the
arrangement, frame, or basket 54 in order to expand or contract
the arrangement. Wires 12 and 13 would not have to be of
spring material when the rod is provided.
Device 10 further includes a radiation source 18 such as
commercially available radioactive material, for example,
iridium, which is combined with spring wires 12 and 13 to form
radioactive metal alloy spring wires. Alternatively, a
commercially available radioactive material surface coating 33
or outer layer is disposed about outer surfaces 36 and 37 of
respective spring wires 34 and 35, as depicted in FIG. 8.
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Spring wires 12 and 13 extend proximally from the expandable
distal portion through end cap 16 and outer sheath 15, which is
formed from a commercially available polytetrafluoroethylene
tube. Proximal end 17 of the inner elongated member or spring
wires would extend beyond the proximal end of the sheath to
provide a convenient grip or handle for extending and
withdrawing the expandable distal portion from and into the
outer sheath. When a central rod is provided, the radioactive
material can be associated with that rod and not with the wires
12 and 13. The radioactive material can be provided by other
means internal to the arrangement, frame, basket or member.
FIG. 2 depicts an enlarged cross-sectional view of
expanded wire arrangement, frame, or basket 54 of FIG. 1 taken
along the line 2-2. Spring wires 12 and 13 are looped at
distal end 14 of the inner elongated member and affixed to one
another using, for example, suture material 57 or a suitable
medical grade adhesive. In a preferred embodiment, radiation
source 18 is commercially available iridium which has been
alloyed with stainless steel to form spring wires 12 and 13.
When device 10 is introduced into the vascular system of
a patient, it is, for example, approximately 95 cm in length and
8 French (2.7 mm or .105") in diameter when the expandable
distal portion is collapsed and retracted within the outer
sheath. Expandable distal portion 11 is approximately 7 mm long
and 3 mm in diameter when extended from the sheath to assume an
open, expanded condition that allows the device to center itself
in the vessel lumen. To accommodate coronary arteries, the
maximum outside diameter of the expandable distal portion when
in a fully expanded condition preferably falls in a range of 0.5
to 4.0 mm. However, the lengths and diameters of device 10 and
expandable distal portion 11 can be adjusted to accommodate
large or small blood vessels or any other body passageways
desired to be irradiated. The word "expandable" means either
self-expanding or being capable of expansion by other means such
as the rod.
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FIGS. 3-5 depict coronary artery 22 with artery lumen 19
partially occluded by intimal hyperplasia and smooth muscle cell
proliferation at vessel region or treatment site 20. FIG. 3
depicts device 10 positioned in the lumen of the coronary artery
with expandable distal portion 11 in the partially occluded
treatment site for providing short-term, localized irradiation
of the coronary artery wall. When sheath or tube 15 is pulled
proximally as depicted in FIG. 4, expandable distal portion 11
extends therefrom or is extended by a rod, and opens to an
expanded condition. Wires 12 and 13, which can include a
radioactive metal alloy, atraumatically rest against the inner
surface, or intimal layer, of coronary artery wall 21 and the
proliferation of cells thereon. As a result, the spring wires
are positioned away from the center of the artery lumen for
minimizing the interruption of blood flow therethrough.
FIG. 5 depicts artery 22 after a short-term, localized
radiation treatment with lumen 19 widened beyond the extent of
the wires about the treatment site. The spring wires of the
expandable frame portion are no longer in contact with the
artery wall. It is to be noted that with this form of
apparatus, the radiation of the wall of the artery has caused
the latter to expand beyond the environs of the expanded distal
portion. To remove device 10 from the coronary artery, sheath
or tube 15 is pushed distally over expandable distal portion 11
for collapsing the spring wires and containing them in the
sheath. Collapse could alternatively be achieved by initially
pushing on the central rod to collapse the arrangement, frame,
or basket and then to pull on the rod and the elongated member
so that they are confined within sheath 15 .
FIG. 6 depicts a minimally invasive medical device 23,
which includes an expandable wire arrangement, frame, or basket
such as a stranded wire basket 24 similar to device 10 except
for the radiation source. The radiation source includes a
plurality of commercially available radioactive iridium material
tubular sleeves 25 disposed around outer surfaces 26 and 27 of
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spring wires 28 and 29 using soft solder 30, as depicted in
FIG. 7. FIG. 7 is an enlarged cross-sectional view of
expandable arrangement 24 of FIG. 6 taken along the line 7-7.
Alternatively, the plurality of radioactive material tubular
sleeves 25 is affixed about the outer surface of the spring
wires by crimping.
FIG. 8 depicts minimally invasive medical device 31,
which includes expandable distal portion or arrangement 32 and
the radiation source in the form of a radioactive surface
coating 33 or a radioactive outer layer disposed on outer
surfaces 36 and 37 of respective spring wires 34 and 35. The
surface coating includes a plastic material with radioactive
iridium particles dispersed throughout. The outer layer
includes radioactive iridium plated on the spring wires.
FIG. 9 depicts minimally invasive medical device 40,
which represents another aspect of the invention. The inner
elongated member of this alternative embodiment includes a dual
lumen balloon catheter 60 distally extended from outer sheath
61. The balloon catheter includes an expandable distal portion
such as an inflatable balloon 38 for expanding and
atraumatically contacting blood vessel wall 62 about a treatment
site. The balloon provides for centering the device in a blood
vessel lumen. One lumen of the catheter provides for inflating
the balloon with radioactive fluid 39, and another lumen allows
blood perfusion through the catheter to the portion of the blood
vessel lumen on the other side of the expanded balloon. The
radiation source of this device such as radioactive fluid 39 is
injected into the balloon for irradiating the treatment site.
FIG. 10 depicts a minimally invasive medical device or
apparatus 41, which represents yet another embodiment of the
invention. Device 41 includes a plurality (eight) of
interweaved wires 42 attached about distal end 43 of an inner
elongated member if the wires are of spring material, then the
distal end 43 of the wires can be soldered (44) to the inner
rod 45 or guide. If the wires are not of spring material, they
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can be expanded by moving proximally the end 43 to the end of
the sleeve thereby expanding the wires. The wire guide 45 is
depicted extending through device 41 for facilitating
advancement of the device through the vascular system and to the
treatment site of a patient. Radioactivity of the wall of the
vessel is provided by making guide 45 of radioactive material
at least partially, and/or by providing radioactive material in
or more of wires 42 in a similar manner to the previous
embodiments.
FIG. 11 depicts minimally invasive medical device 46,
which represents yet another embodiment of the invention. The
device includes expandable distal portion 47 and radiation
source 48 in the form of a surface coating or an outer layer
disposed thereon. Expandable distal portion 47 includes a
plurality (four) of helically positioned wires 49 attached about
distal end 50 using, for example, soft solder. Device 46
further includes swivel connection 51 extending between the
plurality of four helical wires 49 and flexible wire guide coil
52. The flexible coil provides a deflectable, atraumatic means
for maintaining the position of the wire basket in a body
passageway during a therapeutic procedure. The flexible wire
guide coil is positioned over a tapered mandril or,
alternatively, a straight length of round wire and a safety
wire, so that flexible wire guide coil 52 exhibits a gradual
increase in flexibility toward distal end 53 thereof. Swivel
connection 51 provides for the rotation of expandable basket
portion 46 while flexible coil 52 remains stationary.
It is to be understood that the above-described
minimally invasive intravascular medical device for providing a
radiation treatment in a body passageway is merely an
illustrative embodiment of the principles of this invention and
that other devices, instruments, or apparatus may be devised. In
particular, it is contemplated that a radioactive material other
than an iridium material may be used as a radiation source. It
is further contemplated that many commercially available
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radially expandable medical arrangements may be provided to
attach a radiation source about the expandable portion thereof
for providing the radiation treatment to a body passageway and,
in particular, preventing intimal hyperplasia and smooth muscle
proliferation which causes stenosis or restenosis of a blood
vessel passageway. Although described as being particularly
applicable to the vascular system using percutaneous insertion
techniques, it is contemplated that the minimally invasive
device is applicable for providing treatment to the pulmonary
system as well as the gastrointestinal tract. Treatment of the
biliary and urinary system are also contemplated with expandable
medical devices such as wire baskets, particularly adapted with
the radiation source for treating the particular anatomical
system.
In each of the embodiments described, the radiation
means is part of the expandable means such as frames, baskets,
and the like, that are used to expand the wall of the vessel,
and as long as the expandable means stays in position, the
radiation also stays in position and consequently radiates the
wall throughout the expansion period.
An alternative in each of these embodiments, is to only
provide the radiation arrangement once the expansion has been
achieved. That radiation can be supplied within the expandable
arrangement, frame, or basket, such as on the end of the guide
wire. It can be withdrawn prior to withdrawal of the expandable
frame or with the frame. Such alternatives provide much more
precisely controlled degrees of radiation. It enables the
operator to study the formation of the extra enlargement of the
vessel wall beyond the outer extremes of the frame, and enables
quick withdrawal once that state of affairs has been achieved.
