Surgery – Radioactive substance applied to body for therapy – Radioactive substance placed within body
Reexamination Certificate
2000-08-28
2002-12-24
Shaver, Kevin (Department: 3736)
Surgery
Radioactive substance applied to body for therapy
Radioactive substance placed within body
Reexamination Certificate
active
06497645
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to the field of radiotherapy. In particular, this invention relates to a remote controlled, automated delivery system used to advance, retract, and store isotopic neutron sources for treating cancer tumors and the like.
BACKGROUND OF THE INVENTION
Various diseases and disorders can cause undesirable cells to grow within the body of a patient. The most insidious of these diseases is cancer. Cancer is a condition where undesirable cells multiply uncontrollably forming cancerous tumors in the patient's body. To effectively treat cancer, surgery is generally required to remove as many of the cancer cells as possible. After surgery, various treatment methods such as chemotherapy and/or radiation treatment are used to damage or kill the remaining undesirable cells in the patient's body.
Some forms of cancer, such as cancerous brain tumors, are inoperable, and chemotherapy or conventional radiation treatment alone are not sufficient to combat and destroy the cancerous tumor cells. External radiation treatments are typically given to patients, however, as the depth for any one of the various tumors increases, the surrounding area gets exposed to more radiation. To overcome this obstacle, another treatment called brachytherapy was developed. Brachytherapy treatment is a method in which a radiation source is inserted into or near the cancerous tumor, thus the radiation is more focused toward the cancerous tumor cells and less damage occurs to surrounding healthy cells. Radiation sources used in brachytherapy may include various elements which emit various types of radiation or particles, including beta particles and gamma photons. Gamma photons and beta particles are referred to as low linear-energy-transfer (LET) radiation particles in which a particle transfers a small amount of its energy to a tumor cell on each passage. To effectively kill the cancerous tumor cells, the small amount of energy transferred to each cancerous tumor cell must be converted into free radicals via interaction with the oxygen existing within the cancerous tumor cells. Thus, low LET radiation treatment is ineffective against cancer cells which are hypoxic (have less oxygen than typical healthy cells). Hypoxic cells are found in cancerous tumors, such as brain tumors, melanoma, and sarcoma, that are more filly developed (Stage III or Stage IV).
High LET radiation sources, such as neutrons, may be more effective for treating hypoxic cancerous tumor cells (see R. A. Patchell et al., “A phase I trial of neutron brachytherapy for the treatment of malignant gliomas”,
The British Journal of Radiology,
Vol. 70, pp. 1162-1168 (November 1997)). Examples of neutron sources can be a radioactive element, such as californium (Cf-252), that may be internally placed near the tumor cells (i.e. the brachytherapy source) or an external neutron beam produced by a nuclear reactor or proton /deuteron accelerator. These neutron sources emit neutrons which collide with the hydrogen nuclei of the cancerous tumor cells. The recoil hydrogen nuclei (i.e. protons) then break chemical bonds of the essential molecules (e.g. DNA) in the cancerous tumor cells and cause the cells to be damaged and die. The interaction of the high LET radiation sources with the cancerous tumor cells is not dependant on the amount of oxygen that is present in each of the cancerous tumor cells, but rather hydrogen. Both oxic and hypoxic cells contain hydrogen. Thus a neutron treatment is equally effective at killing or damaging both normal cancerous tumor cells and hypoxic cancerous tumor cells.
A delivery system known as an afterloader is used to advance, retract and store highly concentrated isotopic sources used in brachytherapy treatment. Typical afterloaders delivering beta and gamma sources are relatively small (weighing 300 lbs), designed as a standalone piece of equipment, and are generally stationed in the same room as the patient, adjacent to the patient's bedside. To administer a brachytherapy treatment, healthcare workers typically place multiple catheters and/or needles into the patient's tumor and connect them to the afterloader before leaving the patient's room. After running a start-up routine and program, current afterloaders deliver a non-active (dummy) source into the first catheter to verify proper placement. If successful, the dummy source wire is retracted and an active source wire is delivered into the catheter. Next, the afterloader advances to the next catheter
eedle location and delivers a dummy source followed by the active source. This procedure continues until all of the catheter
eedle locations have successfully been radiated.
Radiation treatments with neutron sources using Cf-252 have various limitations. One problem is that the sources are large in size and the intensity of radioactive material is low. Handling and deploying of such sources is done manually. The types of cancerous tumors treated in this matter have been mainly intracavity tumors, such as cervical and head and neck tumors with some success. However, interstitial treatment of high grade brain tumors was also undertaken. Unfortunately, because of the long irradiation time (~30 hours) and the lack of precision in dose delivery caused the patients to suffer from infection and necrosis.
SUMMARY OF THE INVENTION
The present invention provides a remote afterloader suitable for use in brachytherapy with small, high intensity neutron sources.
The present invention provides a remote afterloader for simultaneously delivering and positioning multiple radiation sources in cancerous tumors. The remote afterloader for moving a radiation source into and out of a catheter inserted in a tumor may include one or more radiation source cassettes, one or more motors, and a shielded container for storing the radiation source cassettes and the motor. Each radiation source cassette may include a radiation source wire having the radiation source connected to a treating end and a dummy source wire having a dummy source connected to a treating end. The motor advances and retracts the radiation source wire and the dummy source wire into and out of each radiation source cassette one at a time.
The present invention also provides a radiation source cassette for storing a radiation source. The radiation source cassette may include a radiation source wire having the radiation source connected to a treating end and a dummy source wire having a dummy source connected to a treating end. Furthermore, a motor can be used to advance and retract the radiation source wire and the dummy source wire into and out of the radiation source cassette one at a time.
The present invention provides a remote afterloader having multiple motors for simultaneously delivering multiple dummy sources and neutron radiation sources through catheters or needles to multiple areas of a cancerous tumor, thus significantly reducing the patient treatment time.
The present invention also provides remote afterloader design having adequate radiation shielding and protection from high LET neutron sources such as Cf-252, thus significantly reducing the radiation exposure to the health care personnel.
The present invention also provides a remote afterloader which may serve as a long-term storage vault for radiation sources.
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Cadugan Joseph A.
Gray Cary Ware & Friedenrich LLP
Isotron ,Inc.
Shaver Kevin
LandOfFree
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