Surgery – Radioactive substance applied to body for therapy – Radioactive substance placed within body
Reexamination Certificate
1998-07-16
2001-10-30
Gilbert, Samuel G. (Department: 3736)
Surgery
Radioactive substance applied to body for therapy
Radioactive substance placed within body
Reexamination Certificate
active
06309339
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a device and method for treating a blockage or stenosis in a vessel of a patient. More specifically, the present invention relates to a device and method for precisely and accurately delivering a dosage of radiation to a vessel to inhibit re-stenosis.
BACKGROUND
It is well known that many medical complications are caused by a partial or total blockage or stenosis of a blood vessel in a patient. Depending on the location of the stenosis, the patient can experience cardiac arrest, stroke or necrosis of tissues or organs. Commonly, the stenosis is caused by the build-up of artherosclerotic plaque in the intima of the vessel. The plaque typically builds up irregularly in the vessel. As a result of the irregular build-up of plaque, the lumen of the vessel, in most blocked vessels, is not centrally located relative to the external elastic lamina.
Several procedures have been developed to treat stenoses, including angioplasty, stenting, and atherectomy. However, none of these procedures are entirely successful in inhibiting or preventing the re-stenosis of a vessel after the procedure is completed.
Recent studies have demonstrated that radiation may inhibit or prevent re-stenosis in the vessel by inhibiting or preventing the growth of fibrotic cells in the vessel wall, commonly referred to as neointima. The precise target for the radiation in the vessel is currently not known. However, it is believed that the adventitia may be a key source of growth of the neointima. Therefore, it is theorized that the entire vessel, including the adventitia should be treated with radiation.
At least one delivery device has been used for performing intravascular radiation treatment on a treatment site of the vessel. This delivery device utilizes a catheter to position a radiation source in the vessel lumen, adjacent the treatment site. The radiation source is positioned in the vessel lumen and is allowed to emit radiation until the prescribed dosage is released. With this delivery device, the tissue closest to the radiation source receives a larger radiation dosage than the tissue farthest from the radiation source. Subsequently, the radiation source is removed from the vessel lumen.
However, the results obtained using this type of delivery device are not entirely satisfactory. Specifically, because the growth of the plaque inside the vessel is irregular and/or the vessel is curved, the radioactive source is not centered in the vessel relative to the vessel lamina. Thus, depending upon the dosage prescribed, this can result in undertreating certain portions of the vessel and overtreating certain other portions of the vessel. For example, certain portions of the vessel lamina will receive a larger dosage of radiation than other portions of the vessel lamina.
Undertreating with radiation can result in not inhibiting the neointima and, in some instances, can actually result in stimulating smooth muscle cell proliferation and extra-cellular matrix production. Overtreating with radiation can, for example, induce necrosis or an aneurysm. Therefore, it is important to avoid overtreating and/or undertreating of a treatment site of the vessel.
One attempt to solve this problem involves accurately centering the delivery device in the vessel, relative to the vessel lumen. This can be accomplished using a variety of mechanical devices, such as a centering balloon or an expandable mechanical strut. However, these mechanical devices add excessive mass and bulk to the delivery device. This limits the usefulness of the present delivery device to relatively large vessels, i.e., three and one-half millimeters (3.5 mm) or larger and increases the risk of occluding blood flow in the vessel. Moreover, there is a risk that the delivery device will not be accurately centered.
In light of the above, it is an object of the present invention to provide a device and method for delivering a precise dose of radiation to a treatment site within a vessel without centering the delivery device. Another object of the present invention to provide a device and method for delivering a substantially uniform dose of radiation to the vessel lamina and other areas of the vessel. Another object of the present invention is to provide a device which can be used to precisely evaluate the amount and distribution of atherosclerotic plaque in a vessel and which can tailor the treatment in view of the evaluation. Still another object of the present invention is to provide a device and method which is relatively safe and easy to use in curved vessels. Another object of the present invention is to provide a device which can be easily adapted to meet the specific needs of the patient. Still another object of the present invention is to provide a device for accurately providing a treatment plan based upon the configuration of the treatment site of the vessel. Yet another object of the present invention is to provide a device which is relatively simple and inexpensive to manufacture.
SUMMARY
The present invention is directed to a device which satisfies these objectives. The device is useful for delivering an asymmetrical dose of radiation to a treatment site of a vessel to treat a stenosis in the vessel. In one embodiment, the device includes an adjuster section adapted to be positioned into the vessel. As provided herein, the adjuster section alters the intensity of a portion of the radiation emitting radially from the radiation source when a portion of the radiation source is positioned in the vessel. In use, the adjuster section partly alters the intensity of radiation directed at where the vessel lamina is the closest. This prevents overtreatment of the vessel.
As used herein, the term “radiation dose profile” refers to and means a cross-sectional pattern of energy being delivered to the vessel from a radiation source. A more comprehensive definition of radiation dose profile is provided in the description section.
As used herein, the term “vessel wall” refers to and means the structural support of the vessel. For an artery, the vessel wall includes an endothelium, a basement membrane, a vessel intima, an internal elastic lamina, a vessel media, a vessel external elastic lamina (hereinafter “vessel lamina”), and a vessel adventitia. For a diseased artery, the vessel wall can also include atherosclerotic plaque which infiltrates the vessel intima and causes stenosis of the vessel.
The adjuster section alters a portion of the radiation emitting radially from the radioactive source so that a radiation dose profile which is substantially asymmetrical and eccentric is delivered to the vessel. With an eccentric, asymmetrical radiation dose profile, more radiation is directed at where the vessel lamina is farthest from the radiation source, while less radiation is delivered to where the vessel lamina is the closest. Thus, a substantially uniform dosage of radiation can be delivered to the vessel lamina at the treatment site, even though the delivery device is not centered in the vessel relative to the vessel lamina.
In one version of the present invention, the adjuster section includes a plurality of spaced apart conductor coils which create a magnetic field proximate to the radiation source. Depending upon the direction of current through each conductor coil, each coil either attenuates or potentiates the charged particle radiation which emits from the radiation source. Further, the amount of attenuating or potentiating for each conductor coil depends upon the magnitude of the current in each conductor coil. Thus, the radiation dose profile relative to the radiation source can be specifically tailored for a particular vessel by adjusting the magnitude and direction of current in each conductor coil.
Typically, conductor coils are attached to a catheter and spaced apart radially around the catheter. Additionally, the conductor coils can be spaced apart longitudinally along the catheter. This feature allows the radiation dose profile along a longitudinal axis of the radiation source to be mo
Ciezki Jay P
Jung, Jr. Eugene J.
Lee Eric J.
Savage James D.
Tuzcu Emin M.
Endosonics Corporation
Gilbert Samuel G.
Nydegger & Associates
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