Metal working – Method of mechanical manufacture – Assembling or joining
Reexamination Certificate
1998-10-12
2002-09-03
Hughes, S. Thomas (Department: 3726)
Metal working
Method of mechanical manufacture
Assembling or joining
C029S428000
Reexamination Certificate
active
06442822
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to radioactive source wires used to irradiate body tissue in the treatment of disease. More particularly, the present invention relates to the use of an elongated radioactive source wire with increased flexibility for the localized delivery of radiation to diseased tissue.
BACKGROUND OF THE INVENTION
The most common cause of death in industrial countries is ischemic heart disease which, generally speaking, is an imbalance between myocardial oxygen supply and demand. This imbalance is most often due to obstruction of large coronary arteries by sclerotic plaque and is related to either an absolute decrease in coronary blood flow or an inability to increase coronary blood flow relative to the needs of the heart. Ischemic heart disease is most commonly associated with chest pain, an acute heart attack, an abnormal ventricular rhythm and sudden death. Although various medical and surgical therapies may improve the quality of lifestyle of many patients with this disease, these therapies do not favorably change the underlying cause for the coronary vessel narrowing, nor do they stop its progression.
Various medical interventions have been employed to remove or otherwise treat an offending occlusion in the heart including transluminal angioplasty, coronary artery bypass grafting (CABG), balloon angioplasty, stents, and atherectomy. Of these, balloon angioplasty is the procedure of choice and also the least invasive alternative.
In the past, catheters have been developed which may be effectively inserted into blood vessels and maneuvered through a vascular tree. A balloon may be used with such catheters to expand inside the vessel and to open blockages found therein. In a typical percutaneous transluminal coronary angioplasty (PTCA) or percutaneously transluminal angioplasty (PTA) procedure, a guiding catheter is percutaneously introduced into the vascular system of a patient through an artery and advanced therein until the distal tip of the guiding catheter is appropriately positioned. A dilation catheter having a balloon on the distal end thereof and a guide wire are slidably disposed and introduced through the guiding catheter. The guide wire is first advanced through the distal tip of the guiding catheter until the distal end of the guide wire crosses the lesion to be dilated. The dilation catheter is then advanced over the previously introduced guide wire until the dilation balloon on the distal extremity of the dilation catheter is properly positioned inside the lesion. The balloon portion of the dilation catheter is then inflated to a predetermined size to radially compress the atherosclerotic plaque of the lesion against the inside of the artery wall to thereby reduce the annular stenosed area. After a period of time, the balloon is deflated so that blood flow is resumed, allowing the dilation catheter to be removed.
A major problem encountered in a significant number of patients treated by this procedure is the subsequent narrowing of the artery after the expansion treatment. Various methods and apparatus have been developed to address the restenosis problem including multiple inflations of the balloon during the original procedure, atherectomy, hot balloons, and lasers. Even the installation of permanent stents has been thought to potentially have some value in reducing restenosis rates. See, for example, U.S. Pat. No. 5,019,075 to Spears et al. wherein the region surrounding the balloon utilized in the angioplasty procedure is heated by means within the balloon, or within the skin of the balloon, upon inflation of the balloon in order to ideally fuse together fragmented segments of tissue. U.S. Pat. No. 4,733,655 to Palmaz discloses an expansible vascular graft which is expanded within a blood vessel by an angioplasty balloon to dilate and expand the lumen of the blood vessel. The Palmaz method and apparatus leaves the expandable vascular graft in place to ideally prevent recurrence of stenosis in the body passageway.
However, recent data seems to indicate that the prior art methods described above do not significantly reduce restenosis rates of occurrence. It would therefore be desirable to have a method and apparatus to treat a lesion in order to reduce the restenosis rate of occurrence. The present invention is believed to provide a unique method and apparatus to reduce the restenosis rate of occurrence following an angioplasty or like-intended procedure.
As discussed above, percutaneous transluminal coronary angioplasty (PTCA) is now commonly used for opening blockages, also called stenoses, of both peripheral and coronary arteries. However, within a period of several months after PTCA, a significant percentage of treated arteries experience a reoccurrence of the narrowing, also called restenosis, and a seriously reduced blood flow. In fact, clinically evident restenosis occurs in 30-40% of cases following successful PTCA and is most frequently observed between 3 and 6 months after the procedure. Late restenosis in the months after angioplasty reduces the initial success rate of 90% to 60-70% after six months. Although the incidence of success and associated complications has improved significantly over the last decade, the risk of restenosis has not changed. Hence, of the more than 300,000 coronary arteries subjected to angioplasty during 1990, 30-40% can be expected to restenose. As a result, there is a definite need for a method to reduce this high incidence of restenosis.
As the statistics demonstrate, restenosis after PTCA is a serious problem, and to date, there is no treatment to prevent this complication. It appears to be an inherent reaction of the vessel wall to the angioplasty stretching insult. The outward compression caused by the balloon catheter produces cracking, tearing, and stretching of the wall and a subsequent chain reaction of healing events. In short, it is believed to be caused chiefly by the migration and proliferation of smooth muscle cells which produces an exaggerated healing response. This response can progress to the point of severe restenosis and even occlusion. Due to this restenosis, at least one-third of all PTCA patients return for a second and even a third procedure. Accordingly, there is a definite need to decrease this high incidence of restenosis and thereby increase the long-term benefits of PTCA.
Two (2) approaches are currently employed to reduce restenosis. One approach involves the use of a revascularization device, such as the laser catheter, thermal catheter or stent to debulk plaque and create a smooth lumen to minimize turbulence and platelet aggregation along the vessel wall.
Another approach to reduce restenosis involves infusing a drug which modulates cell growth into the target artery before, during, or after the angioplasty to inhibit the profileration of smooth muscle cells. In particular, antiplatelet agents such as aspirin and dipyridamole, and anticoagulants such as heparin, have inhibited platelet aggregation and thrombus formation to a limited degree, thereby reducing the risk of early occlusion. There is therefore a critical need for an effective method to prevent and/or minimize restenosis after an intravascular procedure. The present invention satisfies this need and provides related advantages as well.
Radiation is used to treat cancer and other diseases of the body. Radiation has long been proven to destroy fast multiplying cells (e.g., cancer) in hopes of destroying or preventing the spread of the disease. Brachytherapy, which is the treatment of cancer at close distances, is one example of the use of radiation for treating diseases of the body. During brachytherapy, a radioactive source or sources are positioned in the area needing treatment. Depending on the shape, size and delivery means of the radioactive sources, the sources are either kept permanently in the body or removed after a specific amount of time. Since permanent implants are tiny seeds approximately 3 mm long and 0.5 mm wide, the use of these seeds do not relate to the present i
Hughes S. Thomas
Interventional Therapies LLC
Omgba Essama
LandOfFree
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