Method of treating a body vessel or duct with radiation from within the lumen

Abstract

A source wire having a radioactive source at its distal tip is used to treat tissue at a target site within a patient's body by localized in vivo radiation. The source wire is advanced to the target site along the intravascular system of the patient's body from a point external to the body. The source wire is a solid lead of substantially uniform thickness along its entire length, composed of nickel-titanium alloy (nitinol). Alternatively, the wire may be a cable composed of multiple strands of the alloy of substantially uniform thickness throughout the entire length of each strand. The alloy has desired characteristics including flexibility, springiness, slipperiness, mechanical strength and shape memory retention, and the source wire is imparted with certain stressed and unstressed states that depend on flexation of the wire and a prescribed transition temperature. The wire has a diameter suitable for passage into the coronary arteries, and the distal end of the wire is tapered for ease of entry into narrowed portions. The tissue to be treated lies along a portion of the interior surface of a coronary artery which has been subjected to an angioplasty procedure to reduce blockage of the lumen and thereby improve blood flow. However, the angioplasty procedure may itself initiate restenosis. The targeted tissue is irradiated only briefly, with the radioactive source of the source wire centered as much as practicable in the lumen of the coronary artery, as by use a channeled centering balloon. This allows substantially uniform radiotherapy of the targeted tissue.