Surgery – Radioactive substance applied to body for therapy – Radioactive substance placed within body
Reexamination Certificate
2001-08-30
2004-06-29
Winakur, Eric F. (Department: 3736)
Surgery
Radioactive substance applied to body for therapy
Radioactive substance placed within body
Reexamination Certificate
active
06755775
ABSTRACT:
BACKGROUND
Radiation therapy is used in treating several medical ailments. In brachytherapy treatment, which is commonly used to treat various forms of cancer, “seeds” containing a radioactive isotope (e.g., iodine-125 or palladium-103) may be implanted in cancerous tissue. Exemplary seeds include the IoGold™ and PdGold™ seeds manufactured by North American Scientific, Inc. (“NASI”) of Chatsworth, Calif. and marketed by Mentor Corporation of Santa Barbara, Calif., or the Prospera™ seed manufactured by NASI. During the active life of the isotope, the seeds, which are each smaller than a grain of rice, deliver a radiation dose to the surrounding tissue. The radiation pattern emitted by the seed depends upon the placement of the radioactive isotope within the seed, the seed housing material, the type of radioactive isotoped used and other factors. Depending upon the isotope used and the amount contained in a seed, the seed may emit radiation for weeks or months. Seeds are generally left in the patient when radiation emission has ceased due to isotope decay.
Prior to implantation the size and shape of the tissue to be irradiated may be mapped out using ultrasound or other imaging techniques. For example, an ultrasound imaging device may be used to image sections of a prostrate so that cancerous portions may be identified in each section. Together, these sections and a marginal area surrounding the cancerous tissue (“extracapsular region”) may comprise the “target volume.” The extracapsular region is tissue on the order of 2-5 millimeters thick that surrounds the prostate gland. Irradiating this region helps to ensure that cancer cells that may have migrated to the into the extracapsular region (i.e., “capsular extension”) will also be treated.
Based on the resulting representation of the tissue, an optimized “dosimetry plan” for treatment of the target volume tissue may be developed. The dosimetry plan specifies the spatial distribution, number and dosage strength of seeds to be implanted. The dosimetry plan is developed with the goal of delivering the needed radiation dosage to the entire target region while ensuring that minimal non-target tissues are irradiated. A typical dosimetry plan may require that approximately one-hundred seeds be implanted.
Brachytherapy seeds are placed via needles which are inserted through the perineum into the prostate gland. Appropriate needle placement is determined base don the special distribution specified in the dosimetry plan and is executed using a guiding template or grid which is positioned in contact with the patient. Placement techniques of brachytherapy seeds vary, but generally, they are placed using preloaded needles, containing both seeds and inactive spacers, which position the seeds along a row in accordance with the dosimetry plan. A movable stylus is positioned within the needle against the column of seeds and spacers. The needle is then removed over the stylus, leaving the seeds and spacers in place. Alternatively, seeds can be placed using a mechanical applicator system, such as that available from Mick Radio-Nuclear Instrument, Inc. (“MRNI”) of Mount Vernon, N.Y. The applicator system allows for individual seed placement without the use of inactive spacers.
Brachytherapy needles may come pre-loaded with brachytherapy seeds and inactive spacer elements or may be loaded at the hospital site prior to implantation. Loading individual seeds and spacers into a needle(s) can be laborious. Because the needle loading procedure can be lengthy and require close contact with the radioactive seeds, medical personnel are exposed to significant doses of radiation when loading the needles.
In the applicator system, one or more seed cartridges or “magazines” may supply seeds to a needle or multiple needles as necessary. Such needles include, for example, the MTP-1720-C or MTP-1820-C TP needles available from MRNI. MRNI also produces seed cartridges—Mick Magazines Catalog #7609 (reusable) and 7609 (disposable). These cartridges may contain up to fifteen seeds and are attached to the applicator. The applicator is fixed to a needle and is designed to place a single seed by ejecting it from the distal end of the needle, which has been placed in the prostate gland in accordance with the dosimetry plan. As a seed is placed, the physician positions the needle for the placement of other seeds. Users of applicator systems feel that such systems provide greater speed and control in the implantation process.
Disposable cartridges may come pre-loaded with seeds and may be made of a light plastic, while reusable cartridges may be made of a metal, such as stainless steel, that is suitable for sterilization in an autoclave. Because using disposable cartridges can be expensive, hospitals generally prefer to use reusable cartridges. While seed manufacturers are generally willing to pre-load single-use, disposable cartridges, they are usually unwilling to pre-load reusable cartridges because used cartridges may be tainted with bio-hazardous material and the handling of such material may require additional site safety certifications or pose additional hazards to employees.
Such reluctance often means that either medical personnel in the operating room or a third party contractor will be required to manually load the cartridge by placing individual seeds into a cartridge using a pair of tweezers or a hemostat. For an implantation procedure involving a hundred seeds, this loading process can be time-consuming and may expose the loading personnel to unnecessarily high doses of radiation, eliminating one of the advantages of using afterloading instead of pre-loaded needles. MRNI manufactures a “Seed Loading V-Block” (Catalog #7509) to assist in loading by holding a seed cartridge in place during the manual procedure. The V-Block comes with a gauge to measure seeds to ensure that they are the proper length (thereby avoiding jamming of the cartridge during loading). However, the task of manual loading remains tedious.
Moreover, because the seeds are small, they are easily lost if dropped during the loading process. Since the seeds are radioactive, medical personnel are required to find and properly dispose of any lost seeds, which is also a time-consuming process. Finally, improper loading of a cartridge may jam the cartridge, preventing its use.
For these reasons, there is needed a simple device and method for loading seeds into a seed cartridge that minimizes the radiation exposure to loading personnel and reduces the risk of dropped seeds or improper loading.
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Bossi David
Cutrer L. Michael
Kalas Dan
North American Scientific, Inc.
Veniaminov Nikita R
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