WO1999040962A1

WO1999040962A1 - Radiation centering catheter with blood perfusion capability

Info

Publication number: WO1999040962A1
Application number: PCT/US1999/003360
Authority: WO
Inventors: Jessica G. Chiu; Frank R. French; Eric D. Peterson
Original assignee: Advanced Cardiovascular Systems, Inc.
Priority date: 1998-02-17
Filing date: 1999-02-17
Publication date: 1999-08-19

Abstract

The invention is directed to a radiation delivery catheter with blood perfusion capability suitable for maintaining patency of a body lumen for a period of time sufficient to prevent delivery of a radiation source to the body lumen. The catheter utilizes an inflatable region which maintains and centers the catheter in the body lumen while allowing blood to perfuse therethrough. The inflatable region can be made up of a plurality of balloon elements having inflatable lobes which create a passageway for blood to flow when the balloon elements are inflated. A thin layer of elastic or non-elastic material (referred to as a membrane) can be placed around the multiple balloon elements to create a smoother surface for blood to flow and to prevent possible blockage caused by dissection or other surface abnormalities found on the wall of the artery. Alternatively, the membrane can be placed over the multiple balloon elements to encapsulate them, preventing blood flow between the passageways formed by the individual lobes. This embodiment is utilized in the event that there is a risk of blood clotting between the individual balloon elements.

Description

- 1 - RADIΛTION CENTERING CATHETER

WITH BLOOD PERFUSION CAPABILITY

BACKGROUND OF THE INVENTION

This invention generally relates to intravascular catheters and particularly to an intravascular catheter assembly for delivering radiation treatment to a body lumen while providing blood perfusion through the body lumen past and around the catheter. In percutaneous transluminal coronary angioplasty (PTCA) procedures, a guiding cathc r having a preshaped distal tip is pcrcutaneously introduced into the cardiovascular system of a patient through the brachial or femoral artery and is advanced therein until the preshaped distal tip is disposed within the aorta adjacent to the ostium of the desired coronary artery. The guiding catheter is then twisted and torqued from its proximal end to turn its distal tip so that it can be guided into the coronary ostium. In an over-the-wire dilatation catheter system, a guide wire and a dilatation catheter having an inflatable balloon on the distal end thereof are introduced into, and advanced through, the proximal end of the guiding catheter to the distal tip of the guiding catheter seated within the coronary ostium. The distal tip of the guide wire is usually manually shaped (i.e. curved) by the physician or one of the attendants before it and the dilatation catheter are introduced into the guiding catheter. The guide wire is usually first advanced out of the distal end of the guiding catheter and is maneuvered into the patient's coronary vasculature containing the stenosis to be dilated, and is then advanced beyond the stenosis. Thereafter, the dilatation catheter is advanced over the guide wire until the dilatation balloon is positioned across the stenosis. Once the dilatation catheter is in position, the balloon of the catheter is filled with radiopaque liquid at relatively high pressures (e.g., generally about 4-12 atmospheres) to inflate it to a predetermined size (preferably the same as the inner diameter of the artery at that particular location ) in order to radially compress the atherosclerotic plaque of the stenosis against the inside of the wall of the arterv. therebv -2- increasing the diameter of the occluded area. The balloon can then be deflated so that the catheter can be removed and blood flow resumed through the dilated artery.

One common problem that sometimes occurs after an angioplasty procedure has been performed is the development of restenosis at, or near, the original site of the stenosis. When restenosis occurs, a second angioplasty procedure or even bypass surgery may be required, depending upon the degree of restenosis. In order to reduce the likelihood of the development of restenosis and thereby prevent the need to perform bypass surgery or subsequent angioplasty procedures, various devices and procedures have been developed for preventing restenosis after arterial intervention. For example, an expandable cage (commonly termed "stent") designed for long term implantation with the body lumen has been utilized to help prevent the occurrence of restenosis.

More recent devices and procedures for preventing restenosis after arterial intervention employ the use of a radiation source to destroy the proliferation of smooth muscle cells which are believed to be the primary cause of restenosis. Balloon catheters have been used to deliver and maintain the radiation source in the area where arterial intervention has taken place, exposing the area to a sufficient radiation dose to abate cell growth. Two devices and methods are described in U.S Patent No. 5,302,168 (Hess) and U.S. Patent No. 5,503,613 (Weinberger). Other devices and methods which utilize radiation treatment delivered by an intravascular catheter are disclosed in commonly-owned and assigned co-pending application U.S. Serial No. 08/654,698, filed May 29, 1996, entitled Radiation-Emitting Flow-Through Temporary Stent and co-pending application Serial No.08/705,945, filed August 29, 1996, entitled Radiation Dose Delivery Catheter with Reinforcing Mandrel, which are incorporated herein by reference. Another medical device for the treatment of a body vessel by radiation is disclosed in European Patent App. 0 688 580 Al (Schneider).

One problem common to many of the balloon catheters which provide radiation treatment to a particular part of a patient's vascular system is that it is sometimes preferable to treat the target area with a lower radiation dosage over a longer -3- period of time rather than a higher dosage of radiation over a shorter period of time.

If conventional balloon catheters are utilized to hold open the area of an artery where restenosis is likely to occur to allow delivery of a radiation source, then the inflated balloon may inhibit or restrict the flow of blood through the artery, which can pose serious risk of damage to tissue downstream from the occluded portion of the artery since the tissue will express a deprivation of oxygenated blood. As a result, the time in which the balloon can remain expanded within the artery would be diminished, effecting the time period in which the radiation dosage can be maintained in the area of the artery where restenosis may occur. Thus, a higher dosage of radiation may have to be administered over a shorter period of time due to the occlusion of the vessel caused by the inflated balloon catheter, which again, may not be as advantageous as providing a lower dosage over a longer period of time.

What has been needed and heretofore generally unavailable in catheters which provide treatment of the body vessel with a radiation source is an intravascular catheter assembly which allows delivery of a radiation source to the area where restenosis may occur for a period of time sufficient to exhibit the cell growth and prevent development of restenosis while still allowing blood to perfuse pass the occluded region during the radiation procedure. Such a catheter assembly should prevent possible restriction of blood flow which may be caused by any dissection or other surface irregularity found on the artery wall. Additionally, the catheter assembly should be capable of centering the radiation source within the body lumen to more evenly administer the radiation to the surrounding tissue and to prevent or reduce the development of radiation burns or "hot spots" on tissue which is placed too close to the radiation source. Further, such an intravascular catheter assembly should be relatively easy and inexpensive to manufacture, have an expandable region that is strong and reliable under pressure, and the capability of being formed in a variety of shapes to allow flexibility in the amount and pattern of expansion and deformation of the portion of the catheter which centers and maintains the radiation source within the body lumen. The present invention satisfies these and other needs as will be described hereinafter. -4- SUMMARY OF THE INVENTION

The present invention is directed to an intravascular catheter with an expandable region located at the distal end of the catheter body which can hold open a body lumen for a sufficient period of time to permit delivery of a radiation source to the body lumen while permitting perfusion of blood through the vessel.

The intravascular catheter in accordance with the present invention includes an elongated catheter body having proximal and distal ends, a guide wire lumen extending at least partly through the elongated catheter body and an inflatable region located near the distal end of the elongated catheter body which communicates with an inflation lumen that extends from the proximal end of the catheter body.

The inflation region is configured to be flexible so that it can be expanded on a curved portion of a body lumen, such as a coronary artery. It is also configured to center a radiation source wire within the body lumen, even if the inflatable region is positioned on a curved section of the body lumen. The inflation region performs all of these features while still allowing blood to flow past it to supply oxygenated blood to tissue downstream from the catheter when the inflated region is in its expanded position.

The intravascular catheter assembly of the present invention allows for an over-the-wire delivery for the advancement thereof of the elongated catheter body to a location within a body lumen where the radiation dose is to be administered. The guide wire lumen is used both for advancing the elongated catheter body to the target area and for advancing a radiation source wire to the target area as well. After the catheter is in place with the inflatable region inflated to its expanded position with the artery, the guide wire is removed from the guide wire lumen to allow the radiation source wire to be advanced to the target area. The exchange may be done by first placing a protective sheath into the guide wire lumen by utilizing a support mandrel which advances the sheath into its proper position within the guide wire lumen. Thereafter the support mandrel can be removed to allow the radiation source wire to -5- be advanced from the radiation source storage facility where it could be advanced through the protective sheath to the targeted area. Once the radiation source \\ ire has been positioned to provide the necessary radiation dosage, the inflatable region can be deflated to its oπginal unexpanded state and the catheter and radiation source w ire can then be removed from the patient's vasculature

In one particular embodiment of the present invention, the inflatable region is made from the plurality of balloon elements disposed along the elongated catheter body Each balloon element includes two, three or more "lobes" which extend outwardly, when inflated, from the catheter body. Each lobe is formed by a pair of opposite facing side walls which extend from the outer surface of the elongated catheter body and terminates at an outer contact edge which is designed to contact the wall of the artery to maintain and center the inflatable region upon inflation. When deflated, each lobe can be wrapped around the elongated catheter body to provide a low profile assembly which can reach even the most distal lesions. In one particular embodiment, each balloon element is made with three lobes which are oriented approximately 120 degrees from each other along the central axis of the catheter body, providing a balloon element having three outer contact edges which will abut against the artery wall when the balloon element is inflated This particular 120 degree configuration produces a structure which sufficiently maintains and centers the balloon element withm the artery and creates three individual passageways to allow blood to flow past the balloon element when inflated Multiple balloon elements having similar lobes can be arranged along the length of the elongated catheter body to form the desired length of the inflatable region. The length of the inflatable region usually defines the working length of catheter where the radiation source is placed duπng the administration of the radiation therapy. Additionally, each individual balloon element can be segmented or spaced apart from an adjacent balloon element to allow articulation This configuration of multiple, spaced apart balloon elements provides at least three benefits, namely, ( 1) better centeπng of the inner tubular member withm the inflatable region and around bends in the arten , (2) -6- prevention of the lobes from being blown out to a circular shape when inflated, and (3) allowing blood to flow along a non-linear path in the event that one of the flow passageways should become blocked.

In other modified embodiments of the present invention, each three-lobed balloon element can be rotated approximately sixty degrees relative to an adjacent balloon element to created a seπes of lobes which are "offset" from each adjacent lobes to create non-linear passageways for blood to flow when the balloon elements are inflated. In still another embodiment, four individual lobes are formed on each balloon element to increase the number of contact edges maintaining and centering the balloon element within the body lumen, along with the number of blood flow passageways. Likewise, multiple four-lobed balloon element can be spaced apart from an adjacent element and rotated to create an offset series of passageways.

In another embodiment of the present invention, a thin layer of elastic or non-elastic material (also referred to as a membrane) can be placed around the multiple balloon elements to create a smoother surface for blood to flow and to prevent possible blockage caused by dissection or other surface abnormalities found on the wall of the artery. When the balloon elements are expanded, the membrane is stretched outward by the individual lobes to create an encircling sheath which maintains the integrity of the blood passageways that are formed between the individual lobes. This membrane also partially contacts the arterial wall to press against a surface irregularity and to maintain a smooth blood flow path. This enveloping membrane can be used on any embodiment of the balloon catheters described herein.

In an alternative embodiment, the membrane is placed over the multiple balloon elements to encapsulate them, preventing blood flow between the passageways formed by the individual lobes. This embodiment is utilized in the event that there is a risk of blood clotting between the individual balloon elements. In this particular embodiment, the balloon elements continue to perform the function of centering the inflatable region within the artery, but the encapsulating membrane prevents blood from flowing between the balloon elements. Blood perfusion past the inflatable region -7- is still possible through a perfusion lumen which can be formed within the catheter body.

These and other advantages of the invention will become more apparent from the foregoing detailed description thereof when taken in conjunction with the accompanying exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view depicting the inflatable region of an intravascular catheter embodying features of the present invention.

FIG. 2 is a cross-sectional view of the inflatable region of the catheter of FIG. 1 , in which the inflatable region is expanded within a curved section of an artery, thereby centering the radiation source wire within the artery.

FIG. 3 is a cross-sectional end view of the catheter of FIG. 1 taken along lines 3-3 showing the balloon element inflated within the artery.

FIG. 4 is a perspective view of another embodiment of an inflatable region of an intravascular catheter embodying features of the present invention.

FIG. 5 is a cross-sectional view of the inflatable region of FIG. 4 showing the balloon element inflated within an artery.

FIG. 6 is a perspective view of another embodiment of an inflatable region of an intravascular catheter embodying features of the present invention.

FIG. 7 is a cross-sectional view of the inflatable region of FIG.6 showing the balloon elements inflated within an artery. -8- FIG. 8 is a cross-sectional view of the inflatable region of another embodiment of an intravascular catheter embodying features of the present invention, showing the inflatable region fully expanded within a curved section of an artery, thereby centering the radiation source wire.

FIG. 9 is a cross-sectional view of the inflatable region of FIG. 8 taken along lines 9-9 showing the balloon element inflated within the artery.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides an intravascular catheter for delivery of and maintaining a low dose radiation source to a patient's body lumen, such as a coronary artery or other vessel, for an extended period of time. The catheter permits perfusion of blood during the radiation therapy and will center the radiation source so that equal amounts of radiation will be applied to the artery. While the invention is described in detail as applied to the coronary arteries, those skilled in the art will appreciate that it can also be used in other body lumens as well, such as peripheral arteries and veins. For example, the present invention is applicable for treating peripheral vessels after percutaneous transluminal angioplasty (PTA). Where different embodiments have like elements, like reference numbers have been used.

FIGS. 1-3 illustrate an intravascular catheter assembly 10 embodying features of the present invention. Catheter assembly 10 generally includes an elongated catheter body 1 1 with an inflatable region 12 on the distal portion thereof and an adapter 13 on a proximal end thereof. An inner tubular member 14 extends coaxially with an outer tubular member 15 and defines an annular inflation lumen 16 which extends from the proximal end of the elongated catheter body 1 1 to the inflatable region 12 and connects in fluid communication the interior of the inflatable region 12 with a source of inflation fluid at the proximal end of the catheter assembly 10. The -9- distal end of the inner and outer tubular members 14 and 15 are joined together by suitable means such as adhesive or heat bonding to seal the inflation lumen 16.

The elongated catheter body 1 1 includes a guide wire lumen 17 positioned in the distal portion of the elongated catheter body which extends from the proximal to distal end of the elongated catheter body 1 1. A guide wire (not shown) would be slidably disposed within the guide wire lumen 17 to facilitate the advancement and replacement of the catheter 10 within the artery 18. An opening 19 is provided at the distal end of the elongated catheter body 1 1 to facilitated the over- the-wire technique used to position the guide wire and catheter 10 within the body lumen.

As can be seen in FIG. 1 , the inflatable region 12 is made up of a plurality of balloon elements 20 which are attached to the elongated catheter body 1 1 and are in fluid communication with the inflation lumen 16. Openings 21 in the outer tubular member 15 allow inflation fluid to inflate or deflate each balloon element 20 as necessary.

Each balloon element 20 is made from a plurality of lobes 22 which extend from the surface of the outer tubular member 15. Each lobe has a pair of oppositely facing walls 23 and 24 (see FIG. 3) which terminate at an outer contact edge 25 which is designed to contact the wall 26 of the artery 18. In the particular embodiment shown in FIGS. 1 -3, each balloon element 20 includes three individual lobes 22 which are oriented approximately 120 degrees from each other along the central axis of the catheter body. This particular 120 degree configuration produces a structure which sufficiently maintains and centers the balloon element within the artery and creates three individual passageways 27 which allow blood to flow past the balloon elements when inflated. While three individual balloon elements 20 are arranged along the length of the elongated catheter body 1 1 in this particular embodiment, it should be appreciated that any number of balloon elements can be used to form the desired length of the inflatable region. The length of the inflatable region usually defines the working length of catheter where the radiation source is placed during the administration of the - 10- radiation therapy. Additionally, the three balloon elements are segmented or spaced apart from each other via tubular segments 28 to facilitate bending in curved portions of an artery. Alternatively, each balloon element can be placed adjacent to one another.

FIG. 3 shows a cross-sectional end view of a balloon element 20 in an inflated condition as positioned within the artery 18. As is shown in FIGS. 2 and 3, each balloon element 20 contacts the wall 26 of the artery 18 only along its contact edges 25. As a result, the passageways 27 created between the wall of the artery and the side walls 23 and 24 of each balloon element create a fluid conduit which allows blood to flow past each balloon element when inflated. A radiation source wire 29 which is advanced within the guide wire lumen 17 remains centered within the inflatable region 12 of the catheter body and accordingly within the artery 18. Thus, during the administration of the radioactive dosage, blood perfusion will still be permitted past the distal end of the catheter assembly allowing the radiation treatment to be delivered over a much more extended period of time.

Each balloon element 20 has a low profile configuration to form sufficiently large passageways 27 to allow blood to perfuse once the balloon elements are in the inflated or expanded condition. In the embodiment shown in FIGS. 1-3, the side walls 23 and 24 of each balloon segment are substantially square in shape and terminate at the outer contact edge 25 to create a triangular cross-section. It should be appreciated that the side walls 23 and 24 could also be configured in other shapes as well to provide proper centering of the radiation source wire within the artery. The low profile of each lobe 22 creates a sufficiently large contact edge 25 which centers and maintains the catheter within the artery, yet is small enough to create a sufficiently large passageway for blood perfusion. It should also be appreciated that the length and width of these contact edges (including side walls 23 and 24) may be varied as well. However, the profile (i.e., the distance between the two side walls) should be sufficiently large enough to support and maintain the catheter within the artery upon expansion, but small enough to create sufficient passageways for blood flow. - 1 1- Once the intravascular catheter 10 has been properly positioned within the artery 18, as shown in FIGS. 2 and 3, the guide wire ( not shown) can be removed from the guide wire lumen 17 to allow the radiation source wire 29 to be inserted into the guide wire lumen 17 for a period of time sufficient to provide the radiation dosage to the body lumen. Preferably, the radiation source wire 29 is hollow at its distal end and contains a radiation dose in the form of a radiation source 30, such as pellets, radiation gas, or radioactive liquid or paste. The radiation source wire 29 may have a radioactive source coated on its distal end. This radiation source wire 29 provides the proper doses of radiation to the areas of the artery 18 where arterial intervention has been performed, either by PTCA, PTA (for peripheral vessels), atherectomy, stenting or other means to help abate the proliferation of smooth muscle cells in this region. A protective sheath 31 , which encases the radiation source wire 29, seals the radiation source from exposure to any body fluids, such as blood, and to provide a sterile barrier between the radiation source wire 29 (which can be reusable and non-sterile) in the patient's vascular system. It is preferable that radiation source wire 29 be stored and its deployment controlled by an afterloader (not shown) which is known in the art.

When using a protective sheath 31 with the radiation source wire 29, once the catheter assembly 10 has been advanced to the target area in the vasculature of the patient, the guide wire can be removed from the guide wire lumen 17 to allow the protective sheath 31 to be loaded into the guide wire lumen utilizing a support mandrel (not shown). Once the protective sheath 31 has been properly placed within the guide wire lumen 17, the support mandrel can be removed from the proximal end of the catheter assembly. The radiation source wire 29 can then be advanced through the protective sheath 27 by the afterloader to the target area where the radiation therapy is to be provided. It is noted that reference herein to the "target area" means that part of the body lumen that has received a PTCA, PTA, atherectomy. or similar procedure to reduce or remove a stenosis, which is subject to the development of restenosis caused, in part, by intimal hyperplasia or the proliferation of smooth muscle cells. -12- Once the required period of time for treatment has been completed, the inflatable region 12 can be deflated, allowing the entire catheter assembly and radiation source wire 29 to be removed from the body lumen. It should be appreciated that the proximal end of the protective sheath 31 can be connected to an afterloader where the radiation source wire may be stored during the initial set up procedure when the catheter assembly is being positioned in the target area. Thereafter, the radiation source wire can be advanced from the afterloader through the protective sheath to the target area, preventing or reducing possible exposure of the radiation source to personnel performing the radiation procedure. In another preferred embodiment of the invention, as shown in FIGS. 6 and 7, the intravascular catheter 10 utilizes an inflatable region 12 which is made up of a plurality of three-lobed balloon elements 20, as shown and described above, except each balloon element 20 is rotated approximately 60 degrees from an adjacent balloon element to offset the series of lobes 22 on each adjacent balloon element. Accordingly, the passageways 27 formed by the individual lobes are now non-linear, i.e., the lobes 22 on balloon elements no longer axially "line up" directly proximal to a corresponding lobe on an adjacent balloon element. As a result, centering of the inflatable region may be enhanced since there are more contact edges which now contact the wall of the artery at different offset positions. Referring now specifically to FIGS. 5 and 6, another embodiment of the inflatable region 12 of the catheter is shown in which four lobes are utilized on each balloon element 20. Each lobe is circumferentially spaced approximately 90 degrees from each other and cooperate to create four individual passageways 27 for blood perfusion. A thin layer or membrane 32 made from an elastic or inelastic material is disposed over the balloon elements 20 to form a sleeve-like member which helps prevent possible blockage of a passageway 27 caused by dissection or other surface abnormalities on the wall of the artery. This membrane 32 expands or contracts accordingly whenever the balloon elements 20 are inflated or deflated. When the balloon elements are deflated, the membrane 32 presses the lobes 22 against the surface - 13- of the catheter body to maintain a low profile to help reach distal lesions. When inflated, the membrane 32 creates a barrier which helps prevent surface abnormalities from blocking the blood passageways 27.

In another embodiment of the present invention, as shown in FIGS. 8 and 9, the catheter 10 includes an inflatable region 12 made from a plurality of balloon elements 20, each having a four-lobe structure. An enveloping membrane 33 is also disposed over each of the balloon elements; however, this membrane 33 is designed to encapsulate the balloon elements 20 from the bodily fluids within the artery, and prevents blood flow through the passageways 27 created between the individual lobes 22. This is accomplished by bonding the ends 34 and 35 of the membrane 33 to the catheter body, creating an outer balloon-like member which encapsulates the individual balloon elements. Since the membrane 33 is highly compliant, being made from a thin layer of elastic or non-elastic material, the individual balloon elements are still able to perform the task of centering and maintaining the inflatable region in the artery. The elongated catheter body 36 of the embodiment shown in FIGS. 8 and

9 is made with multiple lumen structure which allows a perfusion lumen 37 to be formed through the inflatable region 12 to allow blood flow when the balloon elements 20 are inflated in the artery. Perfusion openings 38 in the wall 39 of the catheter body 36 allow the blood to flow through the perfusion lumen and past the inflated balloon elements.

As can be seen in FIG. 9, the elongated catheter body 36 includes an inflation lumen 40 which is used to inflate the individual balloon elements. An opening 41 in the wall of the catheter body creates the fluid path to the balloon elements. A guide wire lumen 42 extending from the proximal to distal end of the elongated catheter body 36 facilitates the advancement and exchange of the catheter within the artery 18. Additionally, as described above in conjunction the other embodiments of the present invention, this guide wire lumen 42 is used to position the radiation source wire 29 to the target area.

The encapsulating membrane 33 shown in FIGS. 8 and 9 -14- IS usually used if the patient has a high blood clotting factor and there is a πsk that blood clotting may occur betw een the individual balloon elements This πsk may not be present in all patients allowing the open sleeve-like membrane 32 shown in FIGS.

6 and 7 to be utilized It should be appreciated that either membrane 32 or 33 could be used with the other embodiments of the inflatable regions descπbed herein.

Generally, the dimensions of the catheter assembly of the present invention are essentially the same dimensions of vasculature catheters used in angioplasty procedures. The overall length of the catheter may be about 100 to 175 cm when a Seldinger approach through the femoral artery is employed, and preferably about 135 cm The diameter of the catheter body may range from about 0.30 to 0.065 inches. The inflatable region in its unexpanded condition has approximately the same diameter as the catheter body, but may be expanded to a maximum diameter of about one to about 5 mm for coronary arteπes and substantially larger (e.g., 10 mm) for peπpheral arteπes The diameter of the guide wire lumen should be sufficiently larger than the diameter of the guide wire and through the guide wire to allow the catheter to be easily advanced and withdrawn over the guide wire. Additionally, the diameter of the guide wire should be sufficiently larger than the diameter of the radiation source wire and protective sleeve to allow these two devices to be easily advanced and withdrawn from within the guide wire lumen. In the preferred method of using the present invention, the inflatable region is held in its expanded condition for a time sufficient to allow the radiation dosage to effect those cells which would otherwise cause restenosis to develop. Preferably, a sufficient dose of radiation can be delivered from about one minute to about sixty minutes to prevent development of restenosis In its expanded condition, the inflatable region presses against, or at least comes in close proximity to, the walls of the artery and in doing so centers the radiation source wire within the artery Centering of this radiation source wire is impoπant so that all portions of the artery receive as close to uniform and equal amounts of radiation as possible Also, centeπng - 15- helps prevent radiation burns or hot spots from developing on portions of the target area.

The catheter assemblies of the invention as described herein are generally employed after an atherectomy, PTCA or PTA procedure, or stent implantation to allow the radiation dose to be administered to an area where restenosis might otherwise develop within a coronary artery. It should be recognized by those skilled in the art that the catheter of the present invention can be used within a patient's vasculature system after vascular procedures other than a PTCA, stent implantation or atherectomy have been performed. The catheter assembly of the present invention may be formed from conventional materials of construction which are described in detail in prior art patents referenced herein. The materials forming the catheter body and protective sheath can be made out of relatively inelastic materials, such as polyethylene, polyvinyl chloride, polyesters and composite materials. The various components may be joined by suitable adhesives such as the acrylonitrile based adhesive sold as Loctite 405. Heat shrinking or heat bonding may also be employed when appropriate. Additionally, the outer membrane can be made with a material which is elastic (distensible) or non-elastic since compression of plaque by the membrane is not required. An elastic material such as latex would be suitable for use. The radiation source wire can be made from materials such as stainless steel, titanium, nickel titanium and platinum nickel alloys, or any NiTi alloys, or any polymers and composites. Variations can be made in the composition of the materials to vary properties.

As described herein, the catheter assembly will deliver a low dosage of radiation through the body lumen, such as a coronary artery, and is configured to provide the dosage over longer periods of time if necessary, due to the catheter's ability to allow blood to perfuse past the inflatable region during treatment. It is preferred that a dosage of radiation, on the order of about 0J up to about 3.0 curies be the typical radiation dose provided to treat, for example, a coronary artery. Preferably. 1 to 2 curies will provide a proper dosage level. -16- The radiation dosage delivered to a coronary artery should be in the range from about 20 to 3,000 rads in preferably not less than thirty seconds. The radiation dose can be delivered in less than thirty seconds, however, it is preferable that a longer time frame be used so that a lower dose can be administered in the target area. It is contemplated that different radiation sources be used, and the preferred radiation sources include iridium¹⁹² if alpha radiation is used, and phosphorus³² if beta particles are used. Further, it is contemplated that the radiation sources may provide beta particles or gamma rays to affect the target cells. However, alpha emitting radiation sources also can be used even though such radiation does not travel very far in human tissue. The use of beta and gamma emitting radiation sources is well known for treating and killing cancerous cells.

Other modifications can be made to the present invention without departing from the spirit and scope thereof. The specific dimensions, doses, times and materials of constructions are provided as examples and substitutes are readily contemplated which do not depart from the invention.

Claims

- 17- WHAT IS CLAIMED IS:

1. An intravascular catheter for maintaining the patency of a body lumen for a period of time sufficient to permit delivery of a radiation dose to the body lumen while permitting blood perfusion. comprising: an elongated catheter body having a proximal end and a distal end; an inflation lumen extending within the elongated catheter body to a location within a distal portion of the elongated body; a guide wire lumen extending through at least a portion of the elongated catheter body for receiving a guide wire; an inflatable region located near the distal end of the elongated catheter body in fluid communication with the inflation lumen, the inflatable region being expandable to contact a portion of the body lumen while permitting perfusion of blood past and over the inflatable region, the inflatable region having a plurality of balloon elements, each balloon element including a plurality of extending lobes adapted to contact the wall of the body lumen to center the inflatable region therein; and a radiation source wire being insertable within the guide wire lumen to provide a radiation source to the body lumen.

2. The catheter of claim 1 , wherein the individual lobes are spaced apart to create a passageway for blood to flow therebetween.

3. The catheter of claim 1. wherein the plurality of balloon elements extend axially along the elongated catheter body, each balloon element having three lobes.

- 18- 4. The catheter as defined in claim 3, wherein each lobe on each balloon element is disposed approximately 120 degrees from an adjacent lobe.

5. The catheter as defined in claim 4, wherein each balloon element and its respective lobes are disposed axially in line with an adjacent balloon element and its associated lobes.

6. The catheter as defined in claim 3, wherein each balloon element is spaced apart from an adjacent balloon element.

7. The catheter as defined in claim 4, wherein each balloon element and its associated lobes are angularly disposed on the catheter body 60 degrees from an adjacent balloon element and its associated lobes.

8. The catheter as defined in claim 1 , wherein each balloon element has four lobes which are circumferentially disposed approximately 90 degrees from one another.

9. The catheter as defined in claim 1 , further including a protective sheath adapted to encase the radiation source wire to protect the radiation source wire from any bodily fluids in the body lumen, the protective sheath being insertable within the elongated catheter body.

-19- 10. An intravascular catheter for maintaining the patency of a body lumen for a period of time sufficient to permit delivery of a radiation dose to the body lumen while permitting blood perfusion. comprising: an elongated catheter body having a proximal end and a distal end; an inflation lumen extending within the elongated catheter body to a location within a distal portion of the elongated body; a guide wire lumen extending through at least a portion of the elongated catheter body for receiving a guide wire; an inflatable region located near the distal end of the elongated catheter body in fluid communication with the inflation lumen, the inflatable region being expandable to contact a portion of the body lumen while permitting perfusion of blood past and over the inflatable region; a thin membrane enveloping the inflatable region while still permitting perfusion of blood past and over the inflatable region; and a radiation source wire being insertable within the guide wire lumen to provide a radiation dose to the body lumen.

1 1. The catheter as defined in claim 10, wherein the inflatable region comprises a plurality of balloon elements, each balloon element including a plurality of lobes adapted to contact the wall of the body lumen to center the inflatable region within the body lumen.

12. The catheter as defined in claim 10, wherein the space between individual lobes on each balloon element creates a passageway for blood to flow therebetween.

-20- 13. The catheter as defined in claim 10, wherein the membrane includes a pair of openings to permit blood to flow therethrough.

14. The catheter as defined in claim 10, wherein the membrane encapsulates the plurality of balloon elements.

15. The catheter as defined in claim 10, wherein the membrane encapsulates the plurality of balloon elements and the catheter body includes a perfusion lumen for allowing blood to flow past the inflatable region.

16. The catheter as defined in claim 10, further including a protective sheath adapted to encase the radiation source wire to protect the radiation source wire from any bodily fluids in the body lumen, the protective sheath being insertable within the elongated catheter body.

17. The catheter of claim 11 , wherein the plurality of balloon elements extend axially along the elongated catheter body, each balloon element having three lobes.

18. The catheter as defined in claim 17, wherein each lobe on each balloon element is circumferentially disposed approximately 120 degrees from an adjacent lobe.

-21- 19. The catheter as defined in claim 1 1 , wherein each balloon element and its respective lobes are disposed directly in line with an adjacent balloon element and its associated lobes.

20. The catheter as defined in claim 1 1 , wherein each balloon element is spaced apart from an adjacent balloon element.

21. The catheter as defined in claim 18, wherein each balloon element and its associated lobes are angularly disposed on the catheter body 60 degrees from an adjacent balloon element and its associated lobes.

22. The catheter as defined in claim 1 1 , wherein each balloon element has four lobes which are circumferentially disposed approximately 90 degrees from one another.

23. A method for maintaining the patency of a body lumen for a period of time sufficient to permit delivery of a radiation dose to the body lumen while permitting blood perfusion, comprising the steps of: a) providing a catheter having: an elongated catheter body having a proximal end and a distal end; an inflation lumen extending within the elongated catheter body to a location within a distal portion of the elongated body; a guide wire lumen extending through at least a portion of the elongated catheter body for receiving a guide wire; -22- an inflatable region located near the distal end of the elongated catheter body in fluid communication with the inflation lumen, the inflatable region being expandable to contact a portion of the body lumen while permitting perfusion of blood past and over the inflatable region, the inflatable region having a plurality of balloon elements, each balloon element including a plurality of extending lobes adapted to contact the wall of the body lumen to center the inflatable region therein; and a radiation source wire being insertable within the guide wire lumen to provide a radiation source to the body lumen; b) positioning a guide wire in the body lumen; c) advancing the elongated catheter body over the guide wire until the inflatable region is within the target area in the body lumen; d) inflating the inflatable region to contact the body lumen to center the guide wire lumen within the body lumen; e) perfusing blood flow through and around the inflatable region; f) removing the guide wire from the guide wire lumen; g) inserting a radiation source wire into the guide wire lumen and advancing the wire to the target area in the body lumen and administering a radiation dose; h) deflating the inflatable region; and i) withdrawing the catheter and the radiation source wire from the bodv lumen.

24. A method for maintaining the patency of a body lumen for a period of time sufficient to permit delivery of a radiation dose to the body lumen while permitting blood perfusion, comprising the steps of: a) providing a catheter having: -23- an elongated catheter body having a proximal end and a distal end; an inflation lumen extending within the elongated catheter body to a location within a distal portion of the elongated body; a guide wire lumen extending through at least a portion of the elongated catheter body for receiving a guide wire; an inflatable region located near the distal end of the elongated catheter body in fluid communication with the inflation lumen, the inflatable region being expandable to contact a portion of the body lumen while permitting perfusion of blood past and over the inflatable region; a thin membrane enveloping the inflatable region while still permitting perfusion of blood past and over the inflatable region; and a radiation source wire being insertable within the guide wire lumen to provide a radiation source to the body lumen; b) positioning a guide wire in the body lumen; c) advancing the elongated catheter body over the guide wire until the inflatable region is in the target area in the body lumen; d) inflating the inflatable region to contact the body lumen to center the guide wire lumen within the body lumen; e) perfusing blood flow through and around the inflatable region; f) removing the guide wire from the guide wire lumen; g) inserting a radiation source wire into the guide wire lumen to the target area in the body lumen and administering a radiation dose; h) deflating the inflatable region; and i) withdrawing the catheter and the radiation source wire from the body lumen.