Abstract:
A device and method for providing radiation to selected radial portions of a segment of the interior wall of a body lumen. In a preferred embodiment, an intravascular catheter is positioned within a desired blood vessel adjacent to a lesion. A radioactive fluid is then injected into the catheter, and the catheter directs the radioactive fluid about the central axis of the vessel in the area of the lesion. This allows selected radial portions of a vessel to have a higher radiation exposure than other portions, which is particularly useful when a lesion does not uniformly extend around the entire circumference of a vessel.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to an intravascular catheter device for providing radiation to the interior walls of a human body lumen. More particularly, the invention relates to a catheter and method of use for selectively delivering radiation to portions of the walls of the human body lumen by distributing radioactive fluid non-uniformly within a catheter. 
     BACKGROUND OF THE INVENTION 
     Intravascular diseases are commonly treated by relatively non-invasive techniques such as percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA). These therapeutic techniques are well known in the art and typically involve use of a guide wire and catheter, possibly in combination with other intravascular devices. A typical balloon catheter has an elongate shaft with a balloon attached proximate the distal end and a manifold attached proximate the proximal end. In use, the balloon catheter is advanced over the guide wire such that the balloon is positioned across and adjacent a restriction in a diseased vessel. The balloon is then inflated and the restriction in the vessel is opened. 
     Vascular restrictions that have been dilated do not always remain open. In approximately 30% of the cases, a restriction reappears over a period of months. The mechanism of restenosis is not understood, but is believed to be different from the mechanism that caused the original stenosis. It is believed that rapid proliferation of vascular smooth muscle cells surrounding the dilated region may be involved. Restenosis may be in part a healing response to the dilation, including the formation of scar tissue. 
     Intravascular treatments, including delivery of radioactive radiation have been proposed as a means to prevent or reduce the effects of restenosis. For example, U.S. Pat. No. 5,199,939 to Dake et al. suggests that intravascular delivery of radiation may inhibit restenosis. Dake et al. suggest delivering radiation within the distal portion of a tubular catheter. Fischell, in the publication EPO 0 593 136 A1, suggest placing a thin wire having a radioactive tip near the site of vessel wall trauma for a limited time to prevent restenosis. Problems exist in attempting to provide uniform radiation exposure using a point or line source. Specifically, as the radiation varies inversely with the square of distance from a point source and inversely with distance from a line source, such sources laying off center near one vessel wall in a lumen may overexpose the nearby wall while underexposing the further away wall. 
     Bradshaw, in PCT publication WO 94/25106, proposes using an inflatable balloon to center the radiation source wire tip. In PCT publication WO 96/14898, Bradshaw et al. propose use of centering balloons which allow blood perfusion around the balloon during treatment. U.S. Pat. No. 5,540,659 to Tierstein suggests use of a helical centering balloon, attached to a catheter at points about the radiation source to allow perfusion through the balloon, and between the balloon and radiation ribbon source. 
     Use of continuous centering balloons having a beta radiation source within may significantly attenuate the beta radiation when the balloon is filled with inflation fluid. Further, the balloon may allow the radiation source to “warp” when placed across curved vessel regions, allowing the balloon to bend but having the central radiation source lying in a straight line between the two ends. Segmented centering balloons may improve the warping problem but may also increase beta attenuation by allowing blood to lie or flow between the beta source and vessel walls. Balloons allowing external perfusion in general have the aforementioned beta attenuation problem. 
     Rather than attempting to center a line or point radiation source using centering balloons or the like, U.S. Pat. No. 5,616,114 to Thornton et al. suggests inflating a balloon with a radioactive fluid. The balloon is inflated until the outer surface of the balloon engages the vessel walls. This inflation process requires a substantial amount of radioactive fluid. In this configuration, the radiation emitted by a portion of the fluid, which is distant from the balloon surface, is attenuated before reaching the vessel walls. 
     In some cases, it may be desirable to provide non-uniform radiation exposure within a vessel, for example, when a lesion does not uniformly extend around the circumference of the vessel wall. For these cases, it may be advantageous to provide more radiation to some segments of the vessel wall and less radiation to others. What remains to be provided, then, is an improved apparatus and method for delivering radiation non-uniformly to vessel walls. 
     SUMMARY OF THE INVENTION 
     The present invention provides devices and methods for providing radiation non-uniformly or to selected areas around the circumference of a segment within a given segment of a human body vessel. This allows selected portions of a vessel within a given segment to have a higher radiation exposure than other portions. As indicated above, this may be advantageous when, for example, a lesion is not uniformly distributed around the circumference of a vessel wall. 
     In one illustrative embodiment, a catheter is positioned within a desired vessel, across and adjacent to a lesion. A radioactive fluid is then injected into the catheter. The catheter directs the radioactive fluid non-uniformly about the central axis of the vessel in the area of the lesion. In an illustrative embodiment, the radioactive fluid is directed to those portions of the vessel wall that have the lesion present, and away from those portions of the vessel wall that are free from the lesion. 
     It is recognized that a lesion can extend around the entire circumference of the vessel wall, but may be thicker in one area than in another. Accordingly, it is contemplated that different radioactive fluids may be directed to different portions of a lesion. By providing the proper type of radioactive fluid, a particular lesion may receive the proper radiation exposure, while reducing the exposure to other body tissue. A preferred radiation source is a beta emitter, as beta radiation penetrates only a few millimeters into tissue, rather than through the vessel tissue and into other body tissues as can be the case with gamma emitters. However, other radiation sources may also be used. 
     The catheter preferably includes a shaft with at least one infusion lumen therein, and a balloon member mounted on the distal end of the shaft. The balloon member preferably includes two or more inflatable channel members. Each of the inflatable channel members form part of the outer surface of the balloon member. Selected inflatable channel members are in fluid communication with the infusion lumen of the shaft. An injecting device is used to inject a radioactive fluid into selected inflatable channel members via the at least one infusion lumen. By aligning the selected inflatable channel members with the lesion, the lesion may receive the proper radiation exposure. 
     It is also contemplated that the shaft may include a second infusion lumen, and that some of the inflatable channel members may be in fluid communication with the second infusion lumen. By selectively injecting radioactive fluid into the appropriate infusion lumen, the proper inflatable channel members may be inflated to irradiate the corresponding portion of the lesion. It is contemplated that any number of separately filled inflatable channel members may be provided to accommodate a wide variety of lesion configurations. 
     It is further contemplated that some inflatable channels are designed for delivering therapeutic agents into portions of the lesions. These additional therapeutic agents may aid in the treatment of the lesion, or in counteracting the adverse effects of the radiation. Anti-angiogenic, anti-proliferative or anti-thrombogenic drugs are examples of such additional therapeutic agents. With this embodiment, at least one infusion lumen is included in fluid communication with selected drug delivery channel members on the balloon. These drug delivery channel members allow the drug to diffuse through the wall of the channel to the treatment site. The combination of radiation and drug therapy is believed to provide added benefits. 
     Alternatively, or in addition to, it is contemplated that different radioactive fluids may be injected into each of the infusion lumens to provide different radiation levels and/or radiation types. For example, the concentration of radioactive isotopes and/or the type of radioactive isotopes may be modified to provide a number of different radioactive fluids. By using more than one radioactive fluid, the inflatable channel members that are associated with one of the infusion lumens may exhibit different radiation characteristics than the inflatable channel members that are associated with another one of the infusion lumens. Finally, it is contemplated that the radioactive fluid may be maintained in each of the infusion lumens for different periods of time. This may provide another degree of flexibility in achieving a desired radiation dosage at a particular location within a vessel. 
     In a preferred embodiment, each of the inflatable channel members is disposed about the outer surface of a primary balloon. When the primary balloon is inflated, the inflatable channel members move outwardly, and preferably ultimately engage the vessel walls. After the primary balloon is inflated, selected inflatable channel members may be inflated with a radioactive fluid to irradiate the desired portion of a lesion. In preferred embodiments, the tubular member, having the lumen for carrying the radioactive fluid, is shielded so that users are not exposed to radiation over the length of the catheter, nor is the vessel lumen wall irradiated at areas other than the treatment site. 
     The primary balloon is preferably inflated with a non-radioactive fluid. Because the primary balloon occupies much of the cross-sectional area of the vessel when inflated, the amount of radioactive fluid required to fill the inflatable channel members is reduced relative to simply inflating the primary balloon with a radioactive fluid. Thus, the likelihood that a physician and/or a patient will become exposed to unnecessary radiation may be reduced, and the cost of obtaining and storing the radioactive fluid may likewise be reduced. 
     It is contemplated that the primary balloon may be of a size and type that can be used to perform an angioplasty procedure. That is, the primary balloon may be sized so that it may be positioned adjacent a restriction within a vessel, and of a type so that the restriction becomes dilated when the primary balloon is inflated. Because the inflatable channel members are preferably disposed about the outer surface of the primary balloon, the lesion at the site of treatment can be irradiated during or immediately after the angioplasty procedure. Alternatively, the primary balloon may be positioned across the treatment site after a conventional angioplasty catheter has been utilized to dilate then withdrawn. In either case, after a desired exposure period, the radioactive fluid may be withdrawn from the inflatable channel members, and the non-radioactive fluid may be withdrawn from the primary balloon. The device may then be withdrawn from the patient to complete the procedure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary side view of a balloon catheter having a channel balloon mounted proximate the distal end thereof; 
     FIG. 2 is a cross-sectional view of the balloon catheter of FIG. 1 taken along line  2 — 2 ; 
     FIG. 3 is a cross-sectional view of the balloon catheter of FIG. 1 taken along line  3 — 3 ; 
     FIG. 4 is a cross-sectional view of the balloon catheter of FIG. 1 taken along line  4 — 4 ; 
     FIG. 5 is a cross-sectional view of the balloon catheter of FIG. 1 taken along line  5 — 5 ; 
     FIG. 6 is a cross-sectional view of the balloon catheter of FIG. 1 taken along line  6 — 6  showing the channels within the balloon; and 
     FIG. 7 is a perspective view of an alternative balloon having a larger number of channels therein. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a fragmentary side view of an illustrative balloon catheter  10  in accordance with the present invention. The balloon catheter  10  includes a shaft  12  with a channel balloon  14  mounted proximate the distal end thereof. The shaft  12  includes a proximal outer tube  16  and a distal outer tube  18 . The distal outer tube  18  is secured to the proximal outer tube  16  with an adhesive at lap joint  20 . To impart more flexibility to the distal portion of the catheter  10 , the distal outer tube  16  is preferably more flexible than the proximal outer tube  16 . The shaft  12  may further include an inner tube  22  having a guide wire lumen  24  therethrough. A guide wire may be inserted through the guide wire lumen  24  to help guide the catheter  10  to a desired site within the vasculature of a patient. In an illustrative embodiment, the inner tube  22  extends from the proximal end of the catheter  10  to the distal end. 
     The channel balloon  14  includes two or more channel members. Each channel member includes a chamber for receiving a radioactive fluid. For example, channel member  26 A has a chamber  28 A and channel member  26 B has a chamber  28 B. Each chamber is preferably separated from an adjacent chamber via a shared side wall, as more clearly shown in FIG.  6 . The channel balloon may be constructed in accordance with U.S. Pat. No. 5,704,912 to Abele et al. and U.S. Pat. No. 5,458,575 to Wang, both disclosures of which are incorporated herein by reference. 
     In the embodiment of FIG. 1, all of the channel members are inflatable from a single infusion lumen  30 . Infusion lumen  30  extends from the proximal end of the catheter  10  to the inflatable chambers, including inflatable chambers  28 A and  28 B. To reduce the volume of the radioactive fluid that is required to inflate the channel members  26 A and  26 B, an infusion tube  32  is provided. The infusion tube extends from the proximal end of the catheter  10  to a point just proximal of the channel balloon  14 . A first seal  36  is provided to seal the fluid that is provided through infusion tube  32  from flowing proximally into the shaft of the catheter  10 . The infusion tube  32  may be shielded to reduce the radiation emitted therefrom. 
     An outer wall  40  of the channel balloon  14  is attached to the distal outer tube  18 , and an inner wall  42  of the channel balloon  14  is attached to a second seal  44 . The inner and outer walls, along with the shared side walls, define each of the chambers of channel members  26 A and  26 B. In this configuration, each chamber of channel members  26 A and  26 B is in fluid communication with the infusion lumen  30 . Although the illustrative embodiment shows for simplicity all of the channel members in fluid communication with a single infusion lumen  30 , it is contemplated more than one infusion lumen may be provided so that selected sets or groups of channel members may be separately inflatable via a corresponding infusion lumen. 
     The distal ends of both the inner wall  42  and outer wall  40  are attached to the inner tube  22  distally of the distal outer tube  18 . In this configuration, the inner tube  22  provides longitudinal support to the channel balloon  14 , and extends the guide wire lumen  24  to the distal end of the catheter  10 . An annular marker band  41  is attached to the inner tube  22  within the channel balloon  14 . Using fluoroscopy, the marker band  41  can be used to identify the location of the channel balloon  12  relative to a desired treatment site. 
     The inner wall  42  of the channel balloon  14  may define a primary balloon having an inner chamber  46 . In the illustrative embodiment, the inner chamber  46  is in fluid communication with a primary inflation lumen  50  in combination with a primary inflation tube  52  extending distally therefrom. The primary inflation lumen  50  is formed by the space between the outer tubes  16  and  18 , inner tube  22  and infusion tube  32 , as more clearly shown in FIGS. 2-3. Primary inflation tube  52  extends proximally of the first seal  36  and distally of the second seal  44 , and provides a fluid path between the primary inflation lumen  50  and the inner chamber  46  of the primary balloon. 
     A manifold  60  is attached proximate the proximal end of the balloon catheter  10 . A first access port  62  provides access to the guide wire lumen  24 . A second access port  64  provides access to the primary inflation lumen  50 . A syringe or the like may be attached to the second access port  64  to inject inflation fluid into the inner chamber  46  of the primary balloon via the primary inflation lumen  50 . Preferably, the inflation fluid used to inflate the inner chamber  46  of the primary balloon is non-radioactive. A third access port  66  provides access to the infusion lumen  30 . A syringe or the like may be attached to the third access port  66  to inject radioactive fluid into the channel members  26 A and  26 B via infusion lumen  30 . 
     The manifold, and in particular the third access port  66 , may be shielded to reduce the radiation emitted therefrom. 
     FIG. 2 shows a cross-sectional side view of the balloon catheter  10  of FIG. 1 taken along line  2 — 2 . The proximal outer tube  16  is shown, having inner tube  22  and infusion tube  32  positioned therein. The inner tube  22  defines the guide wire lumen  24 . As indicated above, the guide wire lumen  24  preferably extends the entire length of catheter  10 . It is contemplated, however, that the guide wire lumen  24  may extend less than the entire length of catheter  10 , such as in a monorail or rapid exchange type configuration. The infusion tube  32  defines the infusion lumen  30 , which provides a fluid path between the proximal end of the catheter to the appropriate inflatable channel members  26 A and  26 B. It is contemplated that infusion lumen  30  may have a shield  70  disposed therearound to reduce the radiation emitted therefrom. The space between the proximal outer tube  16 , inner tube  22  and infusion tube  32  defines the primary inflation lumen  50 . 
     It is contemplated that the shaft may include a second infusion lumen  31 , and that some of the inflatable channel members may be in fluid communication with the second infusion lumen  31 . By selectively injecting radioactive fluid into the appropriate infusion lumen, the proper inflatable channel members may be inflated to irradiate the corresponding portion of the lesion. It is contemplated that any number of separately filled inflatable channel members may be provided to accommodate a wide variety of lesion configurations. 
     It is further contemplated that additional therapeutic agents may be injected into a select infusion lumen which is in fluid communication with drug delivery channel members on the balloon. These drug delivery channels are porous or allow diffusion of a drug through the channel member wall to the treatment site to provide drugs to portions of the lesion. These additional therapeutic agents may aid in the treatment of the lesion, or in counteracting the adverse effects of the radiation. With the addition of these therapeutic agents, physicians may design treatments for a particular lesion. Anti-angiogenic, anti-proliferative or anti-thrombogenic drugs may be incorporated into such treatments. The combination of drugs and radiation is believed to enhance the overall treatment. 
     Alternatively, or in addition to, it is contemplated that different radioactive fluids may be injected into each of the infusion lumens to provide different radiation levels and/or radiation types. For example, the concentration of radioactive isotopes and/or the type of radioactive isotopes may be modified to provide a number of different radioactive fluids. It is contemplated that the radioactive fluids may be liquid, gas or a solid suspended in a carrier. By using more than one radioactive fluid, the inflatable channel members that are associated with one of the infusion lumens may exhibit different radiation characteristics than the inflatable channel members that are associated with another one of the infusion lumens. Finally, it is contemplated that the radioactive fluid may be maintained in selected infusion lumens for different periods of time. This may provide another degree of flexibility in achieving a desired radiation dosage at a particular location within a vessel. 
     FIG. 3 is a cross-sectional side view of the balloon catheter of FIG. 1 taken along line  3 — 3 . FIG. 3 is similar to that shown in FIG. 2, but shows the distal outer tube  18  disposed around the inner tube  22  and the infusion tube  32 , rather than the proximal outer tube  16 . FIG. 4 is a cross-sectional side view of the balloon catheter of FIG. 1 taken along line  4 — 4 . FIG. 4 is similar to that shown in FIG. 3, but further shows a proximal portion of the primary inflation tube  52 . As indicated above, the primary inflation tube  52  provides a fluid path between the primary inflation lumen  50  and the inner chamber  46  of the primary balloon. 
     FIG. 5 is a cross-sectional side view of the balloon catheter of FIG. 1 taken along line  5 — 5 . FIG. 5 is similar to that shown in FIG.  4 . However, because line  5 — 5  crosses catheter  10  distally of the infusion tube  32 , infusion tube  32  is not shown. The infusion lumen  30  continues, however, via the space between the distal outer tube  18 , the inner tube  22  and the primary inflation tube  52 . In this illustrative embodiment, all of the inflatable channel members  26 A and  26 B are in fluid communication with infusion lumen  30 . Thus, the space between the distal outer tube  18 , the inner tube  22  and the primary inflation tube  52  provides the fluid path between the infusion tube  32  and the chambers of each of the inflatable channel members  26 A and  26 B. 
     As indicated above, it is contemplated that more than one infusion lumen may be provided so that selected sets or groups of channel members may be separately inflatable via a corresponding infusion lumen. This may be accomplished by, for example, providing two or more infusion tubes that extend from the proximal end of catheter  10  to a point distally of the first seal  36  but proximally of the second seal  44 . The area between the first seal  36  and the second seal  44  may then be divided into a corresponding number of regions by one or more walls. An illustrative wall  72  is shown in FIG.  5 . The wall  72  would be constructed such that the first region  74  would be in fluid communication with a first group of inflatable channel members and the second region  76  would be in fluid communication with a second group of inflatable channel members. 
     FIG. 6 is a cross-sectional side view of the balloon catheter of FIG. 1 taken along line  6 — 6 . FIG. 6 shows a number of inflatable channel members extending circumferentially around the inner tube  22 . Each of the inflatable channel members defines a chamber. For example, channel member  26 A defines chamber  28 A. Preferably, each channel member shares a common side wall with an adjacent channel member. For example, channel member  26 A shares a common side wall  82  with adjacent channel member  80 . 
     Each of the inflatable channel members is disposed about the surface of a primary balloon. In the embodiment shown, the inner surface  42  forms the outer surface of the primary balloon. When the primary balloon is inflated, the inflatable channel members move outwardly, and preferably ultimately engage a vessel wall. After the primary balloon is inflated, selected inflatable channel members may be inflated with a radioactive fluid to irradiate the desired portion of a lesion. 
     As indicated above, the primary balloon is preferably inflated with a non-radioactive fluid. Because the primary balloon occupies much of the cross-sectional area of the vessel when inflated, the amount of radioactive fluid required to fill the inflatable channel members is reduced relative to simply inflating the primary balloon with a radioactive fluid. Thus, the likelihood that a physician and/or a patient will become exposed to unnecessary radiation may be reduced, and the cost of obtaining and storing the radioactive fluid may likewise be reduced. 
     It is contemplated that the primary balloon may be of a size and type that can be used to perform an angioplasty procedure. That is, the primary balloon may be sized so that it may be positioned adjacent a restriction within a vessel, and of a type so that the restriction becomes dilated when the primary balloon is inflated. Because the inflatable channel members are preferably disposed about the outer surface of the primary balloon, the lesion at the site of treatment can be irradiated during or immediately after the angioplasty procedure. Alternatively, the primary balloon may be positioned across the treatment site after a conventional angioplasty catheter has been withdrawn. In either case, after a desired exposure period, the radioactive fluid is withdrawn from the inflatable channel members, and the non-radioactive fluid is withdrawn from the primary balloon. The device may then be withdrawn from the patient to complete the procedure. 
     FIG. 7 is a perspective view of an alternative channel balloon having a larger number of channel members, including channel members  26 A and  26 B. Each of the channel members extends from the proximal end of the channel balloon  14  to the distal end thereof. As described above, the channels can be selectively filled with radioactive fluid. In an alternative embodiment, it is contemplated that selected channel members may have a number of perfusion holes  88  therein for delivering radioactive seeds or additional therapeutic agents as described herein into the vessel walls, if desired. Further, it is contemplated that the outer surface  44  of the channel members may be coated with a drug release coating having a therapeutic substance therein. Finally, it is contemplated that at least some of the channel members may have a shield  90  placed thereover. The shield  90  may be formed from metal or the like, and may reduce the radiation emitted from the channel members thereunder. The shield  90  may allow all channel members to be inflated with a radioactive fluid, while still providing a non-uniform radiation pattern to the vessel wall. 
     In another alternative embodiment, the catheter balloon of the present invention could be used with radioactive material within the primary balloon and selectively filling certain channels of the balloon with a radiation shielding or absorbing liquid. Selected portions around the circumference could be treated in this manner. 
     Numerous advantages of the invention covered by this document have been set forth in the foregoing description. It will be understood, however, that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of parts without exceeding the scope of the invention. The inventions&#39;s scope is defined in the language in which the appended claims are expressed.