Surgery – Radioactive substance applied to body for therapy – Radioactive substance placed within body
Reexamination Certificate
2000-05-22
2002-10-29
Lacyk, John P. (Department: 3736)
Surgery
Radioactive substance applied to body for therapy
Radioactive substance placed within body
Reexamination Certificate
active
06471631
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to implantable radiation therapy devices. More particularly, the invention relates to improved radiation therapy and brachytherapy devices, also known as radioactive therapeutic seeds, for the treatment of oncological and other medical conditions.
2. State of the Art
Radioactive seed therapy is a well known and well accepted medical procedure for the treatment of various oncological and other medical conditions. Seed therapy, also known as interstitial brachytherapy typically involves the implantation of one to one hundred relatively small capsules (seeds) into or around a treatment site. The capsules contain a radioactive isotope which irradiates the treatment site at close range without adversely affecting other parts of the body. Brachytherapy has been used successfully in the treatment of various types of cancers such as prostate cancer. It has also been used to prevent the growth or regrowth of tissues in the treatment of various occlusive diseases such as arteriosclerosis and arthrosclerosis subsequent to balloon angioplasty.
Radioactive therapeutic seeds are carefully designed to possess several important qualities. First, in the case of prostatic interstitial brachytherapy they should be relatively small, approximately 0.025 inch in diameter and approximately 0.16 inch long so that they may be implanted into the prostate gland using minimally invasive instruments and techniques. However, it should be appreciated by those skilled in the art that implantable radioactive sources come in all shapes and sizes. Second, the radioactive isotope must be enclosed in a biocompatible protective package since the seeds are typically not removed and will remain in the body for many years. Third, each seed preferably includes a radiopaque (e.g. high Z material) marker so that it can be located at the treatment site with the aid of fluoroscopy.
The state of the art of radioactive therapeutic seeds is substantially disclosed in seven U.S. Patents: U.S. Pat. No. 5,713,828 to Coniglione for “Hollow-Tube Brachytherapy Device”, U.S. Pat. No. 5,405,309 to Carden, Jr. for “X-Ray Emitting Interstitial Implants”, U.S. Pat. No. 4,891,165 to Suthanthiran for “Device and Method for Encapsulating Radioactive Materials” and U.S. Pat. No. 4,784,116 to Russell, Jr. et al. for “Capsule for Interstitial Implants”, U.S. Pat. No. 4,702,228 to Russell, Jr. et al. for “X-Ray Emitting Interstitial Implants”, U.S. Pat. No. 4,323,055 to Kubiatowicz for “Radioactive Iodine Seed”, and U.S. Pat. No. 3,351,049 to Lawrence for “Therapeutic Metal Seed Containing within a Radioactive Isotope Disposed on a Carrier and Method of Manufacture”, which are each incorporated by reference herein in their entireties. In addition, the art has been significantly advanced in co-owned U.S. Ser. Nos. 09/133,072, 09/133,081, and 09/133,082, which are hereby incorporated by reference herein in their entireties.
The Lawrence patent, which issued in 1967, describes many of the essential features of radioactive therapeutic seeds. Lawrence describes radioactive isotopes (I-125, Pd-103, Cs-131, Xe-133, and Yt-169) which emit low energy X-rays and which have relatively short half-lives. When implanted at a treatment site, these isotopes provides sufficient radiotherapy without posing a radiation danger to the medical practitioner(s), people in the vicinity of the patient, or other parts of the patient's body. Lawrence further describes a protective capsule which contains the isotope and prevents it from migrating throughout the body where it might interfere with healthy tissue. The capsule is cylindrical and made of low atomic number biocompatible materials such as stainless steel or titanium which do not absorb X-rays. The isotope is coated on a rod shaped carrier made of similar X-ray transparent (e.g. low Z) material and is placed inside the capsule cylinder which is then closed. The other patents each provide some improvement over the original Lawrence design.
Despite the fact that radioactive therapeutic seeds have been in use for over thirty years and despite the several significant improvements made in the seeds, many concerns still exist regarding the use of the seeds. One problem is that prior to and during implantation of the therapeutic seeds, the physician must handle the radioactive seeds, and therefore take precautions to limit his or her exposure. The precautions may include the use of lead lined clothing and limiting the time for completing any one procedure. However, such clothing is generally heavy and tiring to wear, and limiting procedure time may not be in the best interest of the patient.
In addition, it is difficult to store radioactive therapeutic seeds, as special radiation shielding materials must be used in the container storing the seeds.
Moreover, there may be situations in which it is desirable to increase the level of radiation emitted by a seed after implantation, or keep the level of radiation at a certain level despite the natural decay of the radioactive source over a more prolonged period of time. For example, it may be desirable to provide a first dosage of radiation for a period of time and then, based upon a later diagnosis, increase the dosage for a second period of time. With the present radioactive implants of the art this can only be done through a subsequent invasive procedure of implanting additional seeds, as radioactive elements decrease their radiation output according to their respective half-life.
None of the art addresses any manner of providing an “inactive” seed which can later, e.g., after implantation, be activated to emit radiation. Likewise, none of the art addresses otherwise increasing the amount of radiation emitted by the seed after the seed is implanted in the patient, or maintaining a level of radiation over a longer period of time than the half-life of the radioactive isotope in the implant would otherwise permit.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide radioactive therapeutic seeds which have means for controllably altering the radiation transmitted through the seed capsule.
It is also an object of the invention to provide radioactive therapeutic seeds which are controllably activated to “turn on” the seeds to cause radiation to be emitted therefrom or to increase the radiation emitted therefrom.
In accord with these objects which will be discussed in detail below, the radioactive brachytherapy seeds of the present invention generally include an outer capsule containing a radioactive material, and a substantially radiopaque shield which in a first (pre-implantation) configuration substantially obstructs radiation emitted by the radioactive material. One or both of the radioactive material and the shield are controllably movable relative to the other into a second (post-implantation) configuration such that the radioactive material is at least partially unobstructed by the shield. As a result, the level of radiation emitted by the seed is increased. For purposes herein, “radiopaque” refers to the property of having a relatively “high Z” value, and the terms “radiopaque” and “high Z” are used interchangeably herein.
Various embodiments of the radioactive material and the radiopaque shield are provided. In a first embodiment, a low melt temperature low Z material, e.g., wax, includes radioactive particles suspended therein. The low Z material is preferably substantially provided entirely within a high Z casing. The low Z material, with radioactive particles therein, may be heated and forced to flow, by pressurized fluid or mechanical means, through an opening in the high Z casing to at least partially surround the high Z casing and substantially cause the seed to emit radiation. In a second embodiment, an elastic or heat shrinkable casing is stretched over a radioactive material and a high Z material is deposited on the casing. When the radioactive material is heated to a melted state, the force of the casing on the radioactive material moves the radioactive
Jahrmarkt Scott L.
Slater Charles R.
Smith Kevin W.
Smith Scott T.
Gallagher Thomas A.
Gordon David P.
Jacobson David S.
Lacyk John P.
Syntheon LLC
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