Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1999-05-13
2001-06-05
Nguyen, Anhtuan T. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C600S004000, C623S001210, C604S103020, C604S103010
Reexamination Certificate
active
06241719
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is directed to methods for forming a radioactive stent at a vascular site by use of radioactive compositions. Specifically, these methods entail the in vivo delivery of radioactive compositions which are delivered as a fluid to one or more vascular sites. Subsequent solidification of this composition at the vascular site results in the formation of a stent which also acts to deliver a controlled amount of radiation to the vascular site.
In one embodiment, the fluidic radioactive compositions employed in the methods of this invention comprise a biocompatible polymer, a biocompatible solvent and a radioactive agent which provides a sufficient dose of radiation to inhibit restenosis. In another embodiment, the fluidic radioactive compositions employed in the methods of this invention comprise a biocompatible prepolymer, a radioactive agent and optionally a biocompatible solvent which provides a sufficient dose of radiation to inhibit restenosis.
REFERENCES
The following publications are cited in this application as superscript numbers:
1
Dunn, et al., U.S. Pat. No. 4,938,763 for “Biodegradable In-Situ Forming Implants and Methods of Producing Same”, issued Jul. 3, 1990
2
Kinugasa, et al., “Direct Thrombois of Aneurysms with Cellulose Acetate Polymer”,
J. Neurosurg.,
77:501-507 (1992)
3
“CANCER, Principles
&
Practice of Oncology”,
4th Ed., Volume 1,
“Cancer Treatment
”, pp. 545-548 (1993)
4
Greff, et al., U.S. Pat. No. 5,667,767, for “Novel Compositions for Use in Embolizing Blood Vessels”, issued Sep. 16, 1997
5
Greff, et al., U.S. Pat. No. 5,580,568 for “Cellulose Diacetate Compositions for Use in Embolizing Blood Vessels”, issued Dec. 3, 1996
6
Kinugasa, et al., “Early Treatment of Subarachnoid Hemorrhage After Preventing Rerupture of an Aneurysm”,
J. Neurosurg.,
83:34-41 (1995)
7
Kinugasa, et al., “Prophylactic Thrombosis to Prevent New Bleeding and to Delay Aneurysm Surgery”,
Neurosurg.,
36:661 (1995)
8
Taki, et al., “Selection and Combination of Various Endovascular Techniques in the Treatment of Giant Aneurysms”,
J. Neurosurg.,
77:37-24 (1992)
9
Evans, et al., U.S. patent application Ser. No. 08/802,252 for “Novel Compositions for Use in Embolizing Blood Vessels”, filed Feb. 19, 1997
10
Castaneda-Zuniga, et al.,
Interventional Radiology
, in Vascular Embolotherapy, Part 1, 1:9-32, Williams & Wilkins, Publishers (1992)
11
Rabinowitz, et al., U.S. Pat. No. 3,527,224 for “Method of Surgically Bonding Tissue Together”, issued Sep. 8, 1970
12
Hawkins, et al., U.S. Pat. No. 3,591,676 for “Surgical Adhesive Compositions”, issued Jul. 6, 1971
13
Laird, et al., “Inhibition of Neointimal Proliferation With Low-Dose Irradiation From a &bgr;-Particle Emitting Stent,”
Circulation
93(3):529-536 (1996)
14
Greff, et al., U.S. Pat. No. 6,015,541 Radioactive Embolizing Compositions, issued on Jan. 18, 2000.
All of the above publications are herein incorporated by reference in their entirety to the same extent as if each individual reference was specifically and individually indicated to be incorporated herein by reference in its entirety.
2. State of the Art
Atherosclerosis, a disorder involving thickening and hardening of the wall portions of the larger arteries of mammals, is a life-threatening affliction that is largely responsible for coronary artery disease, aortic aneurysm and arterial disease of the lower extremities. Atherosclerosis also plays a major role in cerebral vascular disease. It is responsible for more deaths in the United States than any other disease.
Angioplasty has heretofore been a widely used method for treating atherosclerosis. Percutaneous transluminal coronary angioplasty (hereinafter “PTCA”) procedures involve inserting a deflated balloon catheter through the skin and into the vessel or artery containing the stenosis. The catheter is then passed through the lumen of the vessel until it reaches the stenotic region, which is characterized by a build up of fatty streaks, fibrous plaques and complicated lesions on the vessel wall, which result in a narrowing of the vessel and blood flow restriction. In order to overcome the harmful narrowing of the artery caused by the atherosclerotic condition, the balloon is inflated, thus flattening the plaque against the arterial wall and otherwise expanding the arterial lumen.
Although PTCA has produced excellent results and low complication rates, there has, however, been difficulties associated with the use of this technique. In particular, during the expansion of the balloon against the arterial wall, the arterial wall is frequently damaged and injured. While this damage itself is not believed to be particularly harmful to the health or the life of the patient, the healing response triggered by this damage can cause a reoccurrence of the atherosclerotic condition. In particular, it has been observed that the smooth muscle cells associated with the stenotic region of the artery initiate cell division in response to direct or inflammatory injury of the artery.
Restenosis is the closure of a peripheral or coronary artery following trauma to the artery caused by efforts to open an occluded portion of the artery, such as, for example, by dilation, ablation, atherectomy or laser treatment of the artery. For these angioplasty procedures, restenosis occurs at a rate of about 20-50% depending on the vessel location, lesion length and a number of other variables. Restenosis is believed to be a natural healing reaction to the injury of the arterial wall that is caused by angioplasty procedures. The healing reaction begins with the clotting of blood at the site of the injury. The final result of the complex steps of the healing process is intimal hyperplasia, the migration and proliferation of medial smooth muscle cells, until the artery is again stenotic or occluded.
In an attempt to prevent restenosis, metallic intravascular stents have been permanently implanted in coronary or peripheral vessels. The stent is typically inserted by catheter into a vascular lumen and expanded into contact with the diseased portion of the arterial wall, thereby providing internal support for the lumen. However, it has been found that restenosis can still occur with such stents in place. Also, the stent itself can cause undesirable local thrombosis. To address the problem of thrombosis, persons receiving stents also receive extensive systemic treatment with anticoagulant and antiplatelet drugs.
Prior attempts to inhibit restenosis of coronary arteries have included, among other things, the use of various light therapies, chemotherapeutic agents, stents, atherectomy devices, hot and cold lasers, as well as exposure of the stenotic site to radiation. These therapies have had a varying degree of success, however, certain disadvantages are associated with each of these therapies. Although radiation therapy has shown promise, particularly in inhibiting intimal hyperplasia, the devices available for delivery of radiation sources to a stenotic site have been limited and have tended to suffer from drawbacks which limit their usefulness (see for example, U.S. Pat. No. 5,899,882). Accordingly, there is a need for a stent device which effectively delivers radiation to a stenotic or vascular site to inhibit restenosis.
SUMMARY OF THE INVENTION
This invention is directed to methods for the endovascular formation of a radioactive stent using a radioactive composition. These compositions are delivered to one or more vascular sites in a mammal as a fluid composition which solidifies in vivo to form a solid, coherent radioactive mass, preferably in the form or a stent. The solidified mass stents the vascular site thereby delivering the radioactivity attendant with the composition resulting in inhibition of restenosis.
Accordingly, in one of its method aspects, this invention is directed to a method for endovascular formation of a radioactive stent at a vascular site which method comprises:
(a) endovascularly delivering to a vascular site a liquid permeable balloon catheter, s
Greff Richard J.
Wallace George
Burns Doane , Swecker, Mathis LLP
Micro Therapeutics Inc.
Nguyen Anhtuan T.
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