fig1 of the drawings shows a balloon catheter guidewire 1 which can be inserted through the center of a balloon catheter for steering the catheter through vascular structure to a site where an angioplasty is to be performed . the guidewire 1 has an outer sleeve 3 around an inner or center wire 5 . the guidewire structure 1 is sized to fit within a balloon catheter tube to allow guidance or steering of the balloon catheter by manipulation of guidewire 1 . the outer sleeve 3 of the guidewire is preferably a tightly wound wire spiral or coil of stainless steel , with an inside diameter large enough so that it can be slid or shifted longitudinally with respect to the inner wire 5 . the distal end 7 of inner wire 5 is the portion of the guidewire 1 which is to be positioned for radiation treatment of the site of the angioplasty . the distal end 7 has a radioactive material 9 such as cobalt - 60 which provides an intravascular radiation source , that is , it can be inserted through the vascular structure and will irradiate the site from within , as distinguished from an external radiation source . outer sleeve 3 has an end portion 11 at its distal end which is made of or coated with a radiation shielding substance for shielding the radioactive source 9 . in a preferred embodiment , the shielding section is lead or lead coated steel . the remaining portion 13 of the outer sleeve 3 , extending from shielding section 11 to the other end of guidewire 1 ( opposite from distal end 7 ) can be of a non - shielding substance such as stainless steel wire . by way of example , the guidewire may for example be 150 cm . long with an 0 . 010 &# 34 ; inner wire , having a 30 mm . long radioactive end 9 , and a sleeve 3 of 0 . 018 &# 34 ; diameter having a lead coating 11 which is 30 cm . long . except for the radioactive source 9 and retractable shielding 11 at the tip , guidewire 1 may be generally conventional . as already noted , the outer sleeve 3 of the guidewire 1 is slidable over the inner wire 5 , at least for a distance sufficient to cover and uncover radioactive material 9 , so that the shielding section 11 of the outer sleeve can be moved away from the radioactive material 9 to expose the angioplasty site to radiation . after the exposure , the outer sleeve is shifted again to cover the radioactive section . such selective shielding prevents exposure of the walls of the vascular structure when the guidewire 1 is being inserted or removed . a second embodiment of the invention , as shown in fig2 includes a balloon catheter 15 . the balloon catheter 15 has a balloon 19 at its distal end 21 and is constructed of a medically suitable plastic , preferably polyethylene . catheter 15 has a center core or tube 17 in which a conventional guidewire 23 is receivable . particles or crystals of radioactive material 25 ( which again may be cobalt - 60 ) are embedded in or mounted on tube 17 inside balloon 19 . a retractable radiation shielding sleeve 27 is slidable along tube 17 and covers source 25 , blocking exposure to radiation , until it is shifted away ( to the left in fig2 ). upon completion of angioplasty , the shielding sleeve 27 is retracted and the area of the injury is irradiated . such structure allows radiation of the vascular structure immediately following completion of angioplasty , without separately inserting a radiation source . a third embodiment of the invention , shown in fig3 and 4 , incorporates a balloon mounted stent 29 made of a radioactive material . stent 29 can be in the form of an expandable wire or mesh cage and is mounted over the balloon portion 31 at substantially the distal end 33 of the balloon catheter 32 . the stent is made of or coated with a radioactive material such as iridium 192 which will remain effectively radioactive just for 4 - 5 months , a period sufficient to reduce restenosis which typically occurs in the first six months following angioplasty . stent 29 is expanded by inflation of the balloon portion 31 , as shown in fig4 . after the balloon portion 31 has been deflated , catheter 32 can be removed from the site of the angioplasty . the expanded stent 35 remains at the site of the angioplasty . balloon expandable stents are already known , but not with a radioactive material associated with them . from the foregoing it can be appreciated that the invention provides devices and methods which can be incorporated and used in a well known and tested method for treatment of coronary artery and related diseases . while the present invention has been illustrated by a description of the preferred embodiments which have been described in detail , it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail . additional advantages and modifications will readily appear to those skilled in the art . for example , radiation elements can otherwise be attached within the balloon catheter structure or on a guidewire in accordance with the scope of the following claims .
the incidence of restenosis after angioplasty is reduced by exposing the potentially stenotic site to radiation from a source within the same vascular structure in which the site is located . the radioactive source can be mounted at the distal end of a guidewire , or in a balloon catheter , or on a balloon expansible stent , and is inserted through the vascular structure to the site to be exposed .