X-ray or gamma ray systems or devices – Specific application – Absorption
Reexamination Certificate
1998-03-06
2002-12-17
Church, Craig E. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Absorption
C604S021000
Reexamination Certificate
active
06496561
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to devices, methods and systems for administering localized radiation to vessels, lumens, or cavities of a body, such as cardiovascular tissue, to treat restenosis and other conditions.
BACKGROUND OF THE INVENTION
In the medical field, doctors and scientists strive to find less invasive ways to treat patients. By using treatments that are less intrusive to the body, doctors can greatly reduce the stress on the patient's systems and exposure to infection. For example, laparoscopic techniques enable physicians to explore the interior of the body and perform surgery through a small opening in the skin. Less intrusive medical techniques are extremely beneficial when applied to cardiovascular diseases.
Cardiovascular diseases affect millions of people, often causing heart attacks and death. One common aspect of many cardiovascular diseases is stenosis, or the thickening of the artery or vein, decreasing blood flow through the vessel. Angioplasty procedures have been developed to reopen clogged arteries without resorting to a bypass operation. However, in a large percentage of cases, arteries become occluded again after an angioplasty procedure. This recurrent thickening of the vessel is termed restenosis. Restenosis frequently requires a second angioplasty and eventual bypass surgery. Bypass surgery is very stressful on the patient, requiring the chest to be opened, and presents risks from infection, anesthesia, and heart failure.
Effective methods of preventing or treating restenosis could benefit millions of people. One treatment for restenosis that has been attempted is beta-irradiation of the vessel wall by positioning radioactive isotopes in the vessel at the site of the restenosis. However, the depth of the penetration of the radiation is difficult to control with this method. The depth of the radiation is determined by the type of the radio-isotope used. The radioactive source will also irradiate other healthy parts of the body as it is brought to the site to be treated. Another disadvantage is that medical personnel must take extensive precautions when handling storing, and disposing the radioactive material.
Less intrusive techniques are also extremely beneficial when applied to the esophagus. Tens of millions of Americans suffer from gastroesophageal reflux disease (GERD). GERD is characterized by a backward flow of the stomach and duodenal contents into the esophagus. These conditions result when the valve at the junction between the esophagus and the stomach does not function properly. When this occurs frequently, it is termed chronic GERD or reflux esophagitis. The symptoms of this condition are dyspepsia, or discomfort in the esophagus after meals, burning chest, upper abdominal pain, sour taste, and regurgitation.
Medical research has revealed that the acidic stomach contents cause anatomic abnormalities of the epithelium, or lining, of the esophagus during reflux. The cell type of the epithelium of the esophagus changes from a squamous, or circular-shaped cell, to a columnar, or rectangular-shaped, cell type. This cellular damage of the epithelium is termed Barrett's esophagus.
Barrett's esophagus is a precursor for cancer of the gastroesophageal system. Barrett's-associated malignancies strike approximately 10,000 people per year. There is a high rate of progression from reflux disease to Barrett's esophagus. In fact, 90 percent of patients with reflux symptoms who have an endoscopic examination show anatomic abnormalities of the epithelium.
Diagnosis of cancer in Barrett's esophagus ordinarily leads to removal of the diseased segment of the esophagus. However, an effective treatment of Barrett's disease could prevent the progression to cancer and could therefore reduce the need for this painful and drastic procedure. An effective treatment for Barrett's esophagus could improve the lives of many people. Ultrasound and argon-ion plasma treatments have been suggested to treat Barrett's esophagus, but these techniques are in early experimental stages and have not been proven effective. It is believed that photodynamic therapy is also a possibility.
Many other disorders could be treated with small, effective medical devices capable of accessing the interior of the body. For example, one disorder of the gastrointestinal system is pyloric strictures. Pyloric strictures occur in the pylorus, or distal aperture of the stomach. The pylorus is surrounded by a strong band of circular muscle, through which the stomach contents are emptied into the duodenum. Pyloric strictures can be subjected to dilatation to open the pylorus passage. However, the pylorus frequently thickens in response to the dilatation. Repeated dilatation has been used to treat pyloric strictures, but has not proven to be an effective long-term solution. There is a need for treatments to prevent this recurrent thickening of the pylorus.
Thus, there is a need for miniature devices and effective methods to treat the interior of the body with minimal intrusion. Effective, less invasive techniques for treating stenosis and restenosis of a lumen, treating GERD, and treating pyloric strictures are especially needed.
Recently, X-ray radiation has been realized to provide a very promising way to treat these types of conditions. Ionizing radiation penetrates to the first layers of cells on the surface of the passage or lumen. This radiation induces apoptosis, or programmed cell death.
Apoptosis differs from another type of cell death, necrosis. In apoptosis, a disruption in the gene structure of the cell results in the cell failing to replicate, and in some cells, results in an induced cell death where the contents of the cell are utilized by adjacent cells. Cell death by apoptosis therefore reduces inflammation and the biochemical results of inflammation, as compared to necrosis, which results in scarring and thickening of the surface cells.
X-ray device radiation of the esophagus may be used to treat Barrett's esophagus by inducing apoptosis in the abnormal cells of the epithelium. The escalation of this condition to cancer may be reduced. X-ray radiation can also be used for preventing the thickening of the pylorus after dilatation of pyloric strictures.
X-ray radiation has been found to reduce the occurrence of restenosis when X-ray radiation is applied to area of a blood vessel where an angioplasty or other expansion of the vessel has taken place. In coronary applications, it is desirable to have the X-ray radiation penetrate into the adventitia tissue. The advantages and disadvantages of X-ray radiation penetration into the cardiac muscle tissue are still being investigated. Further, it is desirable to deliver X-ray radiation with a peak energy of about 6-15 kiloelectron volts (keV) in coronary applications. The peak energy may also be 8-10 kiloelectron volts.
X-ray treatment devices for these types of applications must be small and flexible enough to fit inside the vessels and passages, yet have enough rigidity and structural integrity so that they can be advanced a distance through the body and contain the advanced treatment device. In the case where an X-ray device is to be delivered through vessels and passages, there is also the additional complication of providing a high voltage to the treatment device while inside the body. Using the X-ray device may generate heat inside the patient, and the delivery system should prevent any heat from damaging surrounding tissue. If the treatment area is large enough that it cannot be treated from one point inside the body, the treatment device may have to be moved across the treatment area during therapy.
Thus there is a need for delivery formats to be used for example in connection with an X-ray device for emitting localized radiation inside a patient's body. The delivery formats need to include devices and methods that deliver the treatment device reliably to the treatment site, treat the site uniformly and deliver a predictable dose, while being easy to
Andre Patrick D.
Chornenky Victor Ivan
Eibs Thomas E.
Meyer Steven Thomas
Church Craig E.
Medtronic AVE Inc.
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