Surgery – Radioactive substance applied to body for therapy – Radioactive substance placed within body
Reexamination Certificate
2000-06-07
2002-05-21
Winakur, Eric F. (Department: 3736)
Surgery
Radioactive substance applied to body for therapy
Radioactive substance placed within body
C604S515000
Reexamination Certificate
active
06390968
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a modified Fletcher-Suit after-loading cervical applicator for use in brachytherapy. The invention includes a tandem and colpastat tube arrangement permitting introduction of radio-emissive material to intracervical tissues where the tubes are combined with at least one balloon that is inflatable in situ with a radiation attenuating fluid to positionally stabilize the applicator in the patient and provide selective shielding during high dose rate brachytherapy.
2. Description of the Art
Since shortly after the Curies' discovered radioactivity, radiotherapy has been used in connection with treatment of proliferative tissues and, particularly, in connection with cancer treatments and other oncological procedures. The two major categories of radiotherapy are teletherapy and brachytherapy. Teletherapy utilizes an external radiation source generally directed to a select region of the body to destroy cancer cells. Brachytherapy involves directly implanting/embedding a radioactive source within or proximate to a target cancerous mass for localized exposure.
Numerous medical devices and adjuncts have been developed for cervical cancer brachytherapy. An important early development was the Fletcher-Suit cervical applicator. The Fletcher (standard shielded) applicator provided a technique for intracervical/intrauterine introduction of a radioactive source. The traditional Fletcher applicator is employed in low dose therapies and comprises three hollow, metal tubes. The two, flanking “colpastat” tubes provide for intravaginal positioning and the medially disposed intrauterine “tandem” tube is adapted to traverse the vaginal canal and project into the cervix. The conventional Fletcher-Suit system design suffers from a known in situ positioning problem attributed, in part, to the absence of a secure connection between the colpastat tubes and the tandem tube.
Variations of the Fletcher-Suit applicator for intrauterine brachytherapy have evolved from its original form. For example, in Weeks U.S. Pat. No. 5,562,594 a modified Fletcher tandem device providing shielding for protection of untargeted tissues is described. The Weeks applicator features an inflatable lumen applicator with one embodiment incorporating dual inflatable balloons for delivery and placement of radioactive fluid for temporary brachytherapy. The stated purpose of the Weeks applicator is to reduce the dose of radiation applied to internal organs, such as the rectum, without the need to decrease the dose targeted at the tumor-bearing areas. Because Weeks contains a relatively comprehensive discussion of the physics and anatomy associated with intracervical brachytherapy using a Fletcher tandem, its content is incorporated herein by reference.
Schoppel et al., in U.S. Pat. No. 5,012,357, discloses an intracavity brachytherapy applicator permitting “after-loading” shielding particularly useful in CT scanning procedures. Morrison, in U.S. Pat. Nos. 4,244,357 and 5,947,891, discloses a dual tube brachytherapy delivery system including at least one hollow tube (an intravaginal tube) having an inner end adapted for insertion into the vaginal cavity, and a second hollow tube (an intracervical tube) having an inner end adapted for insertion into the cervix and the uterus. Finally, by way of exemplary prior art technologies, Weinberger, in U.S. Pat. No. 5,924,973, describes an applicator incorporating a balloon catheter in fluid communication with an indiflator for inflation with a radioactive fluid.
Brachytherapy is divided into two major classifications, low dose rate (LDR) and high dose rate (HDR). Low dose rate treatments typically involve dose rates of 40 to 60 centigray per hour and more typically about 55 centigray/hr. High dose brachytherapy, on the other hand, contemplates significantly higher rates of dose delivery (up to 1000 centigray per minute) and not uncommonly in the range of hundreds of centigray in minutes. High dose and low dose brachytherapy are generally believed to be of substantially equal efficacy oncologically, albeit that HDR is generally recognized to provide significant delivery efficiencies over a low dose alternative. Notwithstanding significantly enhanced radiation delivery efficiencies, many hospitals and medical treatment providers have opted not to use HDR treatments due to reportedly higher incidences of complications of which the most frequent complications arise from radiation damage to healthy tissues and organs proximate to the implanted/embedded radiation source. The risk of such complications resulting from HDR treatment is believed to have steered some healthcare professionals to conventional LDR techniques and/or use of hybrid LDR/HDR delivery schemes providing radiation delivery at a substantially augmented rate relative to LDR but at a substantially reduced rate from HDR. Thus, while reportedly reducing the risk of complications, such hybrid treatments also represent a corresponding loss of delivery efficiencies.
In brachytherapy associated with treatment of cervical cancer, LDR treatment minimizes collateral and undesirable damage to healthy tissues, e.g. the bladder and rectum, but achieves its therapeutic effect only by subjecting a patient to prolonged periods of immobilization during exposure. Thus, it is not unusual for LDR procedures, particularly in the treatment of cervical cancer, to require hospitalization for days. Furthermore, prolonged procedures result in patient aggravation, inconvenience, and discomfort while also significantly increasing treatment costs attributable to extended hospitalization, all without any significant augmentation in efficacy.
In contradistinction, HDR intra-cervical brachytherapy provides an efficient alternate therapeutic option. HDR may significantly reduce, from days to minutes, the duration of exposure and patient immobilization. Thus, HDR eliminates the need for prolonged hospitalization and reduces patient inconvenience and discomfort without a loss of therapeutic efficacy. In short, reliance on HDR provides significant advantages in healthcare delivery efficiency, minimizes patient discomfort, and even permits outpatient treatment.
Recognizing both the value and potential harm from HDR, healthcare providers have turned to various shielding techniques to minimize undesirable collateral tissue damage in HDR brachytherapy procedures. However, such shielding is difficult to use and difficult to position in situ. Even minor displacement of selective radiation attenuating shielding in situ defeats the benefit provided thereby. If displaced, the shielding not only fails to diminish exposure of healthy tissues but also may obstruct exposure of targeted proliferative tissues. Moreover, the use of effective shielding is increasingly difficult where the applicator embodies complicated structures that either interfere with or are interfered with by the shielding.
Conventional shielding material, e.g., metal, barium fluids, etc. are opaque to radiation which serves admirably to attenuate impinging radiation. However, the very radiation attenuating excellence also obstructs efficient monitoring of the general area by electromagnetic-based instrumentation, for example, tomographs, magnetic resonance imagers, etc. and the more traditional x-rays and fluoroscopes. Finally, conventional shielding does not contribute to stable positioning of the applicator during treatment in conjunction with its function to shield healthy tissue from exposure.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to address and overcome problems of the prior art brachytherapy apparatus and methods. It is another object of this invention to provide a highly efficient and efficacious intracervical and intervaginal brachytherapy delivery system.
Another object of this invention is to provide selective attenuation of radiation emitted from an internally disposed radiation source without reducing dose rate exposure to a selected target.
A further object of the invention prov
Cahn & Samuels LLP
Paxton Equities, LLC
Veniaminov Nikita R
Winakur Eric F.
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