Surgery – Radioactive substance applied to body for therapy – Radioactive substance placed within body
Reexamination Certificate
2001-03-05
2003-08-19
Hindenburg, Max F. (Department: 3736)
Surgery
Radioactive substance applied to body for therapy
Radioactive substance placed within body
Reexamination Certificate
active
06607478
ABSTRACT:
FIELD OF THE INVENTION
The present invention is a surgical device. Specifically, it is an intravascular brachytherapy system adapted to locally irradiate tissue within a body space. More, specifically, it is a temporarily implantable brachytherapy assembly which is adapted to deliver a radiation source within a vessel lumen for treatment of the vessel wall tissue in order to prevent restenosis ancillary to recanalizing and/or stenting of the vessel.
BACKGROUND
Several medical treatments have been developed which use invasive medical devices for local in situ delivery of energy within body tissues, such as for example in order to treat cancer, or according to other specific examples for preventing or reducing restenosis. Restenosis is an occlusive tissue response to vessel wall injury after recanalization of an occluded region of the vessel, such as through angioplasty, stenting or atherectomy, and has been observed to take place during the first six months after recanalization. Restenosis is believed to be related to an injury response in a vessel wall after balloon expansion of an occlusive lesion, in the case of angioplasty and/or stenting, or during debulking of the lesion site, in the case of atherectomy procedures. This wall injury is further believed to invoke a hyperproliferative response in the smooth muscle cells which make up the vessel wall, such that the proliferating muscle tissue essentially grows into the vessel lumen. This muscle cell proliferation forms at least in part an occlusion at the injury site, minimizing or even reversing the initial result of recanalization. Various localized energy delivery devices which have been disclosed for use in preventing restenosis are generally intended to stunt this hyperproliferative growth of smooth muscle cells in order to substantially reduce the related occlusive response and thereby maintain lumenal patency through the injured site post-recanalization.
According to the known devices which are intended for localized energy delivery to tissue, various specific modes of local energy delivery have been previously disclosed. For example, one known procedure for treating tumors uses a catheter to deliver a ferromagnetic material to a tumor so that the material may heat the tumor when exposed to an ultrahigh radiofrequency electromagnetic field or ultrasonic waves. In another example intended to treat atherosclerosis, microscopic magnetic particles are injected intravenously into a patient, are selectively phagocytized by atherosclerotic cells in a lesion along a blood vessel wall in the patient, and are then heated to therapeutic temperatures by subjecting the magnetized cells to a high frequency alternating magnetic field. Another previously disclosed medical device assembly is adapted to locally emit X-ray radiation into tissue adjacent the catheter. Still further, another known device intended for use in preventing restenosis is adapted to emit ultraviolet light radiation into injured vessel wall tissue. More detailed examples of medical device assemblies and methods which are adapted for local delivery of high levels of energy into tissue, such as of the types just described, are variously disclosed in the following references: U.S. Pat. No. 4,359,453 issued to Gordon; U.S. Pat. No. 5,282,781 issued to Granov et al.; U.S. Pat. No. 5,607,419 issued to Amplatz et al.; and PCT No. WO 97/07740.
Other known devices and related procedures place a radioactive source made of a radioisotope material within a particular body region in order to locally irradiate specific tissue abnormalities within that body region. Such procedures are herein generally referred to interchangeably as “radiation therapy” or “brachytherapy” or “radiotherapy”, and include applications which actually treat as well as prevent abnormal conditions in tissue. Medical device assemblies which are adapted for brachytherapy applications are herein interchangeably referred to as tissue “radiation devices” or “brachytherapy devices”, or “radiation therapy devices”
Previously disclosed brachytherapy devices include permanent implantable brachytherapy devices, which are adapted for prolonged brachytherapy of tissues, and temporary implantable brachytherapy devices, which are adapted for brachytherapy of tissue. In addition, particular brachytherapy devices have also been disclosed for specialized use in treating specific tissues, including cancer tumors or injured vessel wall tissue for preventive restenosis therapy.
Permanently Implantable Brachytherapy Devices
Known implantable brachytherapy devices which are generally adapted for prolonged brachytherapy of body tissues include, for example, implantable brachytherapy sources for the prolonged treatment of tumors, and implantable brachytherapy stents for the prevention of restenosis.
One previously disclosed implantable brachytherapy device assembly which is intended for use in treating tumors includes a radiation source affixed to a stainless steel wire which is adapted to be delivered through a catheter for implantation within the region of a tumor. The radiation source includes an alloy of Iridium-192 and platinum encased within a pure platinum outer layer.
Another known implantable brachytherapy device assembly which is intended for use in treating tumors includes an implantable radioactive wire that is adapted to be delivered with a delivery wire through a delivery sheath and into the desired body region. Once delivered to the desired region, the implantable wire is detached from the delivery wire and is thereby implanted within that region. The radioactive wire has a level of radioactivity which may be specially selected for a desired procedure, and is particularly disclosed for conjunctive use with excision or chemotherapy, standard therapies in tumor treatment. The radioactive wire is further disclosed to include a radioisotope such as cobalt-60, cesium-137, iridium-192, iodine-125, palladium-103, tantalum-73, tungsten-74, or gold-198. The radioactive wire is also disclosed to include an inner core with an outer buffer layer of high atomic number material, such as a platinum coil, which is adapted to attenuate radiation. The radioactive wire is further disclosed to include a variety of shapes such as a helix in order to adapt the device to the anatomy where implanted and such shapes may further adapt the device for also occluding a space or lumen in the treatment region. In addition, the radioactive wire may be further adapted to allow for retrieval from the body tissue by use of a retrieval device.
Several endolumenal prostheses, and more particularly implantable endolumenal stents, have also been disclosed for use as implantable brachytherapy devices. Stents are generally implantable tubular structures which are expandable from a radially collapsed condition, which is adapted for delivery to an implant site, to a radially expanded condition, which is adapted to circumferentially engage a vessel wall at the implant site. Such stents may be expandable either by forcing the stent open, such as by means of an inflatable balloon over which the stent is mounted, or by self-expanding means, such as by elastic recovery to the radially expanded condition after removing the stent from a radially confining sheath or tether. While the stent tubular wall is adapted to mechanically hold a vessel lumen open at the site of wall injury, a through lumen is also provided through the stent to allow for flow through the implant region. It is believed that the mechanical presence of stents in regions of vessel wall injury may reduce restenosis in some patients. Radiation therapy stent devices generally combine the restenosis-preventing benefits that are believed to arise from the mechanical structure of the stent with a brachytherapy means coupled to the stent.
More specifically, previously disclosed radiation therapy stent devices provide a therapeutic dose means either as a coating, in cladding associated with Ea stent, an additive within the material which makes up the stent wall, by ionic or chemical vapor deposition w
Hindenburg Max F.
Medtronic Ave Inc.
Szmal Brian
LandOfFree
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