U.S. patent application number 10/776637 was filed with the patent office on 2004-12-09 for hollow tube body for medical tool and a catheter into which the hollow tube body is incorporated.
This patent application is currently assigned to Osamu Kato. Invention is credited to Kato, Osamu, Kato, Tomihisa, Ozawa, Shinji.
Application Number | 20040249277 10/776637 |
Document ID | / |
Family ID | 32821084 |
Filed Date | 2004-12-09 |
United States Patent
Application |
20040249277 |
Kind Code |
A1 |
Kato, Osamu ; et
al. |
December 9, 2004 |
Hollow tube body for medical tool and a catheter into which the
hollow tube body is incorporated
Abstract
A hollow tube body for medical tool has a plurality of metallic
wires (2) cylindrically stranded to form a flexible tube. An inner
surface of the flexible tube forms a convex-concave structure
represented by the metallic wires (2) formed semi-circular in corss
section. A leading distal end of the flexible tube is formed into a
knife-edge circle configuration to provide a knife-edge circle
front (3). The hollow tube body is used for catheters (K, K1, K2
and K3) to impart them with a perforative ability so as to improve
its quality and performance.
Inventors: |
Kato, Osamu; (Kyoto-fu,
JP) ; Ozawa, Shinji; (Aichi-ken, JP) ; Kato,
Tomihisa; (Aichi-ken, JP) |
Correspondence
Address: |
MORGAN LEWIS & BOCKIUS LLP
1111 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20004
US
|
Assignee: |
Osamu Kato
ASAHI INTECC CO., LTD.
|
Family ID: |
32821084 |
Appl. No.: |
10/776637 |
Filed: |
February 12, 2004 |
Current U.S.
Class: |
600/434 ;
606/108 |
Current CPC
Class: |
A61M 25/0068 20130101;
A61M 25/0012 20130101; A61M 25/0069 20130101; A61M 25/0043
20130101; A61M 25/008 20130101 |
Class at
Publication: |
600/434 ;
606/108 |
International
Class: |
A61F 011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 17, 2003 |
JP |
2003-037550 |
Claims
What is claimed is:
1. A hollow tube body for medical tool comprising: a plurality of
metallic wires cylindrically stranded to form a flexible tube, an
inner surface of which forms a convex-concave structure represented
by said metallic wires each formed semi-circular in corss section;
and a leading distal end of said flexible tube being formed into a
knife-edge circle configuration to provide a knife-edge circle
front.
2. The hollow tube body for medical tool according to claim 1,
wherein a blade edge of said knife-edge circle front is outwardly
arcuated in cross section, and diametrically decreases
progressively as approaching outward.
3. The hollow tube body for medical tool according to claim 1,
wherein a rigid-flexible property of said flexible tube gradually
changes in the lengthwise direction.
4. A catheter comprising: a hollow tube body for medical tool
including a plurality of metallic wires cylindrically stranded to
form a flexible tube, an inner surface of which forms a
convex-concave structure represented by said metallic wires each
formed semi-circular in corss section; and a leading distal end of
said flexible tube being formed into a knife-edge circle
configuration to provide a knife-edge circle front; said hollow
tube body being applied at least partly to a mono-layered main tube
body.
5. A catheter according to claim 4, wherein multi-layered tube
structure is formed by slidably fitting an upper-layered tube onto
a lower-layered tube of a main tube body, and at least one of said
upper-layered tube and said lower-layered tube is applied at least
partly to said hollow tube body.
6. The catheter according to claim 5, wherein an outer tube is
slidably fit onto said upper-layered to form a three-layered
structure, and a self-expansible stent mounted on said
lower-layered tube is arranged to be pushably set and detachably
released by means of said outer tube.
7. The catheter according to claim 6, wherein a stranding direction
of metallic wires of said lower-layered tube and that of said
upper-layered tube are mutually opposite, otherwise a stranding
direction of metallic wires of said upper-layered tube and that of
said outer tube are mutually opposite.
8. The catheter according to claim 6, a rigidity of which
progressively increases in such a direction from said lower-layered
tube to said upper-layered tube, otherwise said rigidity
progressively increases in such a direction from said lower-layered
tube to said outer tube.
9. The catheter according to claim 6, wherein a manipulating
portion of said lower-layered tube and said upper-layered tube, or
a manipulating portion of said lower-layered tube, said
upper-layered tube and said outer tube are connected in a row to a
handling section.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a flexible tube body used as a main
wire material for a catheter, and particularly concerns to a
catheter into which the flexible tube body is incorporated.
[0003] 2. Description of Prior Art
[0004] As a general usage, a catheter is inserted into a tourtous
blood vessel or a somatic cavity to be introduced into a diseased
area. In this situation, the catheter is manipulated outside a
patient's body by pushing, pulling and rotating a handling section
of the catheter. During the manipulating process, the catheter
advances its leading distal end toward the diseased area to provide
it with a necessary treatment.
[0005] In order to ensure a smooth insertion and treatment for the
catheter, it is important to provide the catheter with a high
linearity in free state, a pliable flexiblity through its entire
length and a good restorability from a bendng deformation. It is
also desirable that the catheter has a gradient property
represented by a high flexibility at the leading distal end and a
reasonable rigidity at a rear portion. At the same time, a high
torque transmissibility and good steerability are required for the
catheter as mechanical properties so that the leading distal end
can precisely respond to manipulating action of the handling
section.
[0006] Prior references have been introduced as having a flexible
tube for medical tool which can cope with the above mechanical
properties. The prior references are Laid-open Japanese Patent
Application No. 2002-275774 and Japanese Domestic Publication No.
2000-51.3235 in which a group of metallic wires circular in cross
section are cylindrically stranded to form a flexible tube
structure.
[0007] When the prior references are used as a catheter and medical
guide wire, they have a technological advantages to reduce a weight
per unit length based on a hollow tube structure, a high flexiblity
and good torque transmissibility brought by a wire-stranded body in
which a group of metallic wires are stranded hollow. However, both
the prior references leave rooms for improvements in quality and
performance because they are short of a drilling (perforative)
ability against a hard clot area (e. g., fibrous cap), a
stent-retaining ability and an insertion-slidability advancing into
the blood vessel when treating an obstruction area of the blood
vessel.
[0008] Therefore, the present invention has been made with the
above drawbacks in mind, it is a main object of the invention to
provide a high quality hollow tube body for medical tool and a
catheter in which the hollow tube body is incorporated.
SUMMARY OF THE INVENTION
[0009] According to the present invention, there is provided a
hollow tube body for medical tool in which a plurality of metallic
wires cylindrically stranded to form a flexible tube. An inner
surface of the flexible tube forms a convex-concave structure
represented by the metallic wires formed semi-circular in corss
section. A leading distal end of the flexible tube is formed into a
knife-edge circle configuration to provide a knife-edge circle
front. A catheter is provided which uses a mono-layered tube in
which the hollow tube body is employed at least partly as a main
tube.
[0010] According to other aspect of the present invention, there is
provided a catheter in which a multi-layered tube structure is
formed by slidably fitting an upper-layered tube onto a
lower-layered tube of a main tube body, and at least one of the
upper-layered tube and the lower-layered tube is used as the hollow
tube body.
[0011] Due to the former aspect of the invention, a drilling
(perforative) ability is imparted to a distal end of the flexible
tube, while rendering an outer surface of the flexible tube highly
smooth. This improves a performance of the catheter when inserting
it into the blood vessel and the somatic cavity for the purpose of
providing an appropriate treatment.
[0012] With the knife-edge circle front outwardly arcuated in cross
section and a rigid-flexible property of the flexible tube
gradually changing in the lengthwise direction, it is intended to
stablize the performance obtained from the basic structure of the
invention.
[0013] With the latter aspect of the invention, the catheter is
formed by two-or three-layered tube body. The catheter has the
multi-layered tube body in which the stranding direction of the
metallic wires is opposite among each layer of the tube bodies. The
rigidity progressively changes from the inner-layered tube to the
outer-layered tube.
[0014] With the catheter formed by the hollow tube body, the
catheter is rotated so that the knife-edge circular front advances
to serve as a drill so as to perforate or push a hard clot area
open when the guide wire, which introduces the catheter, confronts
the hard clot area of a completely obstructed region in the blood
vessel. This helps smoothly advance the catheter into a true lumen
to facilitate the proper treatment against the diseased area.
Further, a smooth outer surface of the hollow tube body improves an
insertion-slidability against the blood vessel and the somatic
cavity so as to produce a catheter of high quality.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] A preferred form of the present invention is illustrated in
the accompanying drawings in which:
[0016] FIG. 1 is a plan view of a hollow tube body for medical tool
according to a first embodiment of the invention but partly
sectioned;
[0017] FIG. 2 is an enlarged latutidinal cross sectional view of
the hollow tube body taken along the line II-II of FIG. 1;
[0018] FIG. 3 is an enlarged longitudinal cross sectional view of a
front portion of the hollow tube body taken along the line III-III
of FIG. 1;
[0019] FIG. 4 is an explanatory view showing how the hollow tube
body is formed;
[0020] FIG. 5 is a plan view of a catheter according to a second
embodiment of the invention but partly sectioned;
[0021] FIG. 6 is an explanatory view showing how the catheter is
manipulated;
[0022] FIG. 7 is a plan view of a catheter according to a third
embodiment of the invention but partly sectioned;
[0023] FIG. 8 is a plan view of a front portion of a catheter
according to a fourth embodiment of the invention but partly
sectioned;
[0024] FIG. 9 is an explanatory view showing how the catheter is
manipulated;
[0025] FIG. 10 is a plan view of a front portion of a catheter
according to a fifth embodiment of the invention;
[0026] FIGS. 11 and 12 are explanatory views showing how a catheter
is manipulated according to a sixth embodiment of the
invention;
[0027] FIG. 13 is a plan view of a hollow tube body according to a
seventh embodiment of the invention;
[0028] FIGS. 14 and 15 are explanatory views showing how the hollow
tube body is formed;
[0029] FIG. 16 is an explanatory view showing how a hollow tube
body is formed according to an eighth embodiment of the invention;
and
[0030] FIG. 17 is a view of a handling section of the catheter.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] Referring to FIGS. 1 through 3, a hollow tube body 1 for
medical tool is shown according to a first embodiment of the
invention. The hollow tube body 1 (referred simply to as "tube
body" hereinafter) is formed by cylindrically stranding a group of
austenitic stainless steel wires 2 along a predetermined circle
line to provide a flexible tube which has a certain length (L). An
inner surface of the tube body 1 forms a convex-concave structure
represented by the stainless steel wires 2 generally formed
semi-circular in corss section. An outer surface of the tube body 1
is rendered smooth cosecutively in the lengthwise direction while
the inner surface forms a hollow space 4 in which the
convex-concave structure resides. A leading distal end of the tube
body 1 is formed into a knife-edge circle configuration to provide
a knife-edge circle front 3. The knife-edge circle front 3 is
outwardly arcuated in cross section, and diametrically decreases
progressively as approaching outward.
[0032] The tube body 1 has 8-12 numbers of metallic wires 2, and
measures approx. 0.61 mm in outer diameter (D1) and approx. 0.45 mm
in inner diameter (D2).
[0033] The tube body 1 is formed as shown in FIG. 4. Namely, a wire
rope R is provided by stranding the metallic wires 2 around an
elongated core (not shown). One end of the wire rope R is secured
to a rotational chuck 11 of a twisting device 10. The other end of
the wire rope R is secured to a slidable chuck 12 from which a
weight 13 is depended. The wire rope R is twisted under the tensile
stress caused from the weight 13. A current generating device 14
draws electric currents to the chucks 11 and 12 through an electric
wire code 15 so that the wire rope R is heated by its electric
resistance to remove the residual stress appeared on the wire rope
R during the twisting process. Then, the outer surface of the tube
body 1 is smoothly ground so that the metallic wires 2 forms
semi-circular in cross section. The elongated core is withdrawn
from the wire rope R to provide a hollow tube structure.
[0034] FIG. 5 shows a catheter K into which the tube body 1 is
incorporated. The catheter K has a flexible hollow tube body as a
main structure in which a plurality of the metallic wires 2 are
stranded according to the method as depicted in FIG. 4. The tube
body 1 has a front section in the lengthwise direction as an X-zone
in which the knife-edge circle front 3 is situated on the leading
distal end. A rear length portion of the catheter K belongs to a
Z-zone, and serves as a diameter-increased portion (denoted at D3
as its diameter) in which the metallic wires 2 forms circular in
cross section with its outer surface not ground. A middle length
portion of the catheter K diametrically increases progressively
from its front end (D1) to rear end (D3) to serve as a Y-zone
between the front section and the rear length portion. The
structure is such that the catheter K is flexible in the front
portion and rigid in the rear portion as is the necessary property
given to the catheter K. A connector 5 and a marker M are provided
as is well known for those versed in the art. The knife-edge circle
front 3 is provided by plasma-welding a coil element of the
metallic wire 2, and formed to be outwardly arcuated in cross
section by means of grinder or the like. A circumferential surface
of the knife-edge circle front 3 is rendered smooth. By
appropriately determining a distance between the plasma-welded top
end and the marker M, a rigid-flexible degree of the leading end of
the catheter K is rendered adjustable.
[0035] Upon inserting the catheter K into a completely obstructed
area 25 in a blood vessel 20 to cure the obstructed area 25 as
shown in FIG. 6, a guide wire C which introduces the catheter K may
meet a calcified hard clot area 26 (fibrous cap) of the completely
obstructed area 25. In this situation, the guide wire G is
manipulated so that it detours the completely obstructed area 25 to
be introduced between the media 22 and the adventitial coat 23
through the intima 21 of the blood vessel 20. However, the guide
wire G meets a hard clot area 26a again at the other side beyond
the completely obstructed area 25 so as to hinder an advancement of
the guide wire G.
[0036] In order to eliminate the hindrance, the catheter K is
advanced from the guide wire G, and rotated to use the knife-edge
circle front 3 as a drill to perforate or push the hard clot area
26a open, thus helping the guide wire G smootly advance into the
true lumen. Hard clot powder pulverized by the knife-edge circle
front 3 is carried away rearward along helical grooves inside the
tube body 1. This eliminates an inconvenience caused due to the
fact that the pulverized hard clot powder remains.
[0037] The catheter K is such that its rear end decreases
diametrically as approaching the front end portion of the catheter
K. This amplifies the rotational force of the front end portion
which udergoes the rotational torque from the handling section of
the catheter K. This ensures a good drilling function of the
knife-edge circle front 3 when the rear end of the catheter K is
rotated. The smooth outer surface of the front end portion (X-zone)
of the catheter K enables a manipulator to readily insert it into
the blood vessel and easily rotate it in the blood vessel.
[0038] The group of the metallic wires 2 is twisted under the
tensile stress along the lengthwise direction in accordance with
the method as shown in FIG. 4. This gives the tube body 1 a high
linearity property and a twist-deforming property. Each of the
metallic wires 2 uniformly slides smoothly without variations to
develop no gap between the helical line elements of the tube body
1, the gap of which often appears on an outer tensile side of a
single-wound helical coil tube body when the tube body is bent in
the blood vessel with a minimun diameter. This improves an
insertability against the blood vessel, a rotation-following
ability of the handling section and a torque transmissibility so as
to ensure a precise treatment with a high efficiency. The knife
edge circle front 3 forms an outwardly tapered fashion and
facilitates its insertion against the blood vessel.
[0039] FIGS. 7 through 9 shows a third embodiment of the invention.
In the third embodiment of the invention, a catheter K1 has a
lower-layered tube 1A provided as a main tube by the tube body 1
identical to that of the catheter K in FIG. 5. An upper-layered
tube 1B has the knife-edge circle front 3 at its leading distal
end, and is diametrically increased to be slidably fit onto the
catheter K of FIG. 5.
[0040] FIG. 8 shows a catheter K2 according to a fourth embodiment
of the invention in which a stranding direction of the
lower-layered tube 1A and that of the upper-layered tube 1B are
mutually opposite by approx. 90 degrees (intersection angle between
the lower metallic wires and the upper metallic wires). For this
reason, upon perforating the hard clot area 26a of the completely
obstructed area 25 as shown in FIG. 9, the lower-layered tube 1A is
manipulated first to provide a small hole on the hard clot area
26a, and then the upper-layered tube 1B is manipulated to advance
from the lower-layered tube 1A to diametrically enlarge the small
hole, thus easily perforating the hard clot area 26a with a
sufficient-sized hole.
[0041] In general, the blood-dilatation treatment has been
implemented with the use of balloon catheters which are replaced in
turn from diametrically smaller ones to diametrically larger ones.
The replacing operation of the balloon catheters is done only by
sliding the upper-layered tube 1B, thus facilitating the
blood-dilatation treatment with a high efficiency.
[0042] The metallic wires 2 of the lower-layered tube 1A and that
of the upper-layered tube 1B come to substantially engage in a
point contact with the catheter K2 in which the stranding direction
of the lower-layered tube 1A and that of the upper-layered tube 1B
are mutually opposite. This improves the slidability of the
upper-layered tube 1B against the lower-layered tube 1A so as to
render the upper-layered tube 1B easily manipulatable.
[0043] In the two-layered catheter K2, a bending rigidity of the
upper-layered tube 1B may be determined to be greater than that of
the lower-layered tube 1A. A hydrophilic polymer (e.g.,
polyvinylpyrrolidone or the like) may be coated on sliding portions
of the upper-layered tube 1B and the lower-layered tube 1A.
[0044] In the layered structure in which the bending rigidity of
the upper-layered tube 1B is greater than that of the lower-layered
tube 1A, a bending resistivity of the latter is positively held by
the former. This can prevent harmful deformations from being
accumulated on the lower-layered tube 1A when the catheter K2 is
repeatedly bent with minimum diameters, whereby avoiding an
abnormal insertion resistivity from being induced on the catheter
K2 when inserting it into the blood vessel.
[0045] FIG. 10 shows a fifth embodiment of the invention in which a
catheter K3 of multi-layered structure is provided. In the fifth
embodiment of the invention, an outer tube 1C is slidably fit onto
the upper-layered tube 1B which is slidably fit onto the
lower-layered tube 1A in the same manner as described at the third
embodiment of the invention (referred to FIG. 7). The outer tube 1C
is structurally identical to the upper-layered tube 1B to form a
three-layered tube structure.
[0046] FIGS. 11 and 12 show a sixth embodiment of the invention in
which a frustocone-shaped chip 8 is provided with the lower-layered
tube 1A of the fifth embodiment of the invention. The chip 8 is
formed by a metallic (preferably radiopaque) material or a
synthetic resin material. The chip 8 is diametically decreases
progressively as approaching forward. Between the chip 8 and a
front section of the upper-layered tube 1B, a self-expansible stent
S is provided. The stent S is pushed by the outer tube 1C to set it
in position. Then, the stent S is placed in the diseased area of
the blood vessel. The outer tube 1C slides rearward to let the
stent S eject in itself so as to set it in the diseased area. It is
to be noted that the knife-edge circle front 3 of the upper-layered
tube 1B may be omitted to improve the sliding performance between
the lower-layered tube 1A, the upper-layered tube 1B and the outer
tube 1C when the upper-layered tube 1B is made of a synthetic resin
(e.g., polyethylene, fluoro-based plastics or the like).
[0047] The catheter K3 of the three-layered tube structure enables
a manipulator to readily retain the stent S on the diseased area of
the blood vessel. This makes it possible for the manipulator to
promptly treat the diseased area with a high efficiency, while
shortening the time period during which a subject patient suffers
so as to significantly ameriorate the curability.
[0048] An inner surface of the outer tube 1C forms a concave-convex
undulation which is consecutively in slidable contact with a zigzag
coil line of the stent S. This makes the outer tube 1C come in a
point contact with the stent S, thus enabling the manipulator to
appropriately eject the stent S with a smooth operation upon
pulling the outer tube 1C to release the stent S.
[0049] As other usage of the catheter K3, the lower-layered tube 1A
is firstly used to provide a preliminary perforation, then the
upper-layered tube 1B is used to provide a middle-sized
perforation, and the outer tube 1C is finally used to complete a
full-sized perforation against the hard clot area 26a (three-stage
perforation). This makes it possible to ensure a full-sized
perforation with a precise operation.
[0050] FIGS. 13 through 15 show a seventh embodiment of the
invention which provides another method different from the first
embodiment of the invention. During the process of forming the tube
body 1 (FIG. 4), the wire rope R is divided into the X-, Y- and
Z-zones in the lengthwise direction. A clamp device 14 is mounted
on the boundary portion between the X-, Y- and Z-zones, and has a
pair of opposed clamp plates 15 which open and close to loosen and
tighten the wire rope R as shown in FIGS. 14 and 15. The wire rope
R is twisted in different turns depending on the X-, Y- and
Z-zones. This method renders the metallic wires 2 to be twisted in
different turns so as to produce the tube body 1 as shown in FIG.
13. Among the mechanical properties needed for the catheter, the
tube body 1 has a bending property which responds in varying
hardnesses to the X-, Y- and Z-zones depending on the numbers of
twisting turns subjected. When the tube body 1 is used as a
flexible linear wire for medical tool, the most rigid section of
the flexible linear wire corresponds to the handling section
residing outside the subject patient the softer and more flexible
section of the flexible linear wire corresponds to the leading end
portion which is introduced into the blood vessel and the somatic
cavity. This produces the tube body 1 of high quality in which the
bending rigidity changes to progressively increase or successively
decrease in the lengthwise direction so as to provide a
rigid-flexible gradient property.
[0051] FIG. 16 shows an eighth embodiment of the invention in which
heating devices 16A, 16B and 16C are provided. The wire rope R is
set to the heating devices 16A, 16B and 16C in accordance with the
lengthwise x-, Y- and Z-zones. During the process of twisting the
wire rope R, otherwise after taking the wire rope R out of the
twisting device 10, the wire rope R is heat-treated individually by
the heating devices 16A, 16B and 16C. This makes it possible to
produce the tube body 1 in which the residual stress is removed in
varying degrees depending on the X-, Y- and Z-zones.
[0052] Depending on the different heating conditions of the heating
devices 16A, 16B and 16C, the X-, Y- and Z-zones come to represent
the residual stress removed in different degrees. For this reason,
the tube body 1 functions as a highly effective catheter in which
the tensile strength and the bending rigidity gradually changes in
the lengthwise direction so as to add good mechanical properties
needed for the catheter.
[0053] In the prior method of forming the flexible tube body, the
tube body is provided by winding a metallic wire around a mandrel
or using a winding machine (on paragraph 0004 of the Laid-open
Japanese Patent Application No. 2002-275774 and on page 1.4 of the
Japanese Domestic Publication No. 2000-513235). This developes a
work hardening layer on one side of the metallic wire to often
induce excessive gaps between the helical coil lines of the tube
body when the tube body is bend to its minimum diameter, thus
losing the rotational maneuverability and the torque
transmissibility.
[0054] On the contrary, the method is such that the metallic wires
2 are twisted under the uniform tension to form the work hardening
layer equally on an entire surface of the metallic wires 2. This
makes the helical lines of the tube body 1 slide equally each other
to avoid the excessive gaps from developing between the helical
coil lines when the tube body 1 is bend to its minimum diameter,
thus ensuring a good rotational maneuverability and a torque
transmissibility.
[0055] FIG. 17 shows handling sections of the catheter K3 in which
the tube body 1 is of two-or three-layered structure (referred to
FIG. 10). The catheter K3 has the lower-layered tube 1A, the
upper-layered tube 1B and the outer tube 1C, to which the
manipulating portions 6A, 6B and 6C are respectively secured in a
row. The manipulating portions 6A, 6B and 6C are individually
pushed, pulled and rotated to enable the manipulator to perforate
the hard clot area 26a and release the stent S. The manipulating
portions 6A, 6B and 6C may be formed differently from a wing-shaped
one provided around respective boss portions. Between the
manipulating portions 6B and 6C, a connector 5 is provided which
has an injector 7 to introduce contrast media into the blood
vessel. In the catheter K1 of two-layered structure (referred to
FIG. 7), only the manipulating portions 6A and 6B are provided in a
row.
[0056] It is preferable to use the austenitic stainless steel for
the present catheter. With the use of the austenitic stainless
steel, its low thermal conductivity makes it possible to avoid the
heat conduction from unnecessarily spreading upon welding the
knife-edge circle front 3 and marker M, thus preventing the
catheter from deteriorating with a limited amount of electric
currents and a shortened period of welding time.
[0057] As apparently from the foregoing description, the tube body
for medical tool enhances the performance and function of the
catheter which enables the manipulator to perforate the hard clot
area and to readily retain the stent in the diseased area so as to
significantly improve the curability and the convenience of the
subject patient.
[0058] It is to be noted that the knife-edge circle front 3 may be
formed by welding a discrete a coil or ring line to a front tip
coil end of the tube body 1, otherwise the knife-edge circle front
3 may be integrally provided by press-deforming the front tip coil
end of the tube body 1. Alternatively, the front tip coil end of
the tube body 1 may be embeded in a plastic ring which serves as
the knife-edge circle front 3.
* * * * *