Surgery – Miscellaneous – Devices placed entirely within body and means used therewith
Reexamination Certificate
1999-05-06
2002-08-13
Lacyk, John P. (Department: 3736)
Surgery
Miscellaneous
Devices placed entirely within body and means used therewith
C600S001000
Reexamination Certificate
active
06431175
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to a system and method for intrabody directing and monitoring doses of therapeutic radiation applied to a patient's body. More particularly, the system and method of the present invention employs an implantable sensor coupled to a relaying device, with which, information pertaining to radiation sensed and optionally quantified by the sensors can be relayed outside the body. In addition, the system and method of the present invention can be utilized to assist in directing radiation to a treatment site within the patient's body.
Radiation therapy is used extensively in the medical field to treat a variety of medical conditions. Radiation therapy typically utilizes electromagnetic radiation, typically ionizing radiation, such as, but not limited to, x-ray, gamma-rays and particle beams, as well as ultrasonic radiation to treat many types of cancers, tumors and, cell proliferative disorders as well as non-malignant medical conditions, including, but not limited to, the disintegration of stones.
It will be appreciated that radiation is typically detrimental to living cells. It is known that cancerous cells are more prone to the effects of radiation as such cells are rapidly proliferating cells. However, the effect of radiation on normal cells cannot be overlooked. Thus, when treating with radiation, one desires to apply the maximal possible (optimal) dose onto a specific location, trying, as much as possible to avoid radiating neighboring locations, so as to maximize the treatment vs. injury ratio.
Thus, although with some tumors it is possible to take advantage of the higher sensitivity of the tumor cells to the radiative energy, in most radiation therapy procedures localized treatment is effected by incorporating various methods and devices to direct the radiative beams to the site of treatment, so as to enable radiating at optimal therapeutic doses.
It will be appreciated that the precise aiming and collimating of such radiating beam (several centimeters in diameter) onto the treated site is of prime importance in optimizing the healing/injury ratio (see for example U.S. Pat. No. 3,794,840 to Scott and U.S. Pat. No. 4,995,068 to Chou).
However, in spite of such optimization, in the course of treatment, normal cells which surround the tumorous tissue are also effected by the radiation.
In order to minimize the damage to surrounding healthy tissues several dosage monitoring methods have been utilized by oncologists in conjunction with radiation therapy procedures.
One such monitoring method relies on measuring the entrance and exit doses of radiation. Interpolation of this data is used to determine dosage to tissues. However, measurement of entrance and exit doses combined with interpolation can only predict the dosage of the actual entrance and exit locations which are directly measured. In addition, the dosage applied to the treated locations, where interpolation has been performed, cannot always be predicted from the measured entrance and exit doses.
Another monitoring method involves the surgical implantation of thermoluminescent dosimeter (TLD) devices typically inserted through the midplane of the tumor and in single planes above and below the midplane. Unfortunately, such devices are not designed to relay data outside the patient's body. Thus, not only dosage monitoring is not effected in real time, invasive surgical removal of such devices, under full anesthesia, is required.
Another monitoring method relies on a single skin dose measurement as a checkpoint for the treatment plan. However, this procedure provides the treating physician with very little useful information on the actual dosage delivered deep into the affected tissue and the surrounding body tissues.
Another monitoring method utilized in conjunction with a treatment procedure incorporates a radiation phantom. An example of a radiation phantom is disclosed in U.S. Pat. No. 3,310,885 which describes a radiation phantom for use in a breast irradiation procedure. Such a phantom is fabricated with breast adapters into which TLD devices are inserted, thus, a prescribed radiation treatment is first carried out on the adapter which serves as a control. Although such a system can incorporate many TLD devices and as such, achieve many measurements, the positioning of the adapter, and the size and shape of the adapter is not necessarily repeatable and does not necessarily correspond to the actual positioning, size and shape of the patient's breast and surrounding tissue. A plastic cup strapped to the patient's breast has thus been used to shape the breast of the patient to conform somewhat with the phantom breast adapter. In any case, radiation phantoms are localized outside the patient's body, and as such provide little information, if any, relating to the actual doses applied to the treated site.
Since most of the above mentioned monitoring methods rely heavily on mathematical calculations and projections, such methods fail to accurately predict the doses absorbed by various body regions. Furthermore, since most of these methods employ calculations effected on information retrieved from the dosimetric points, field distortions, which can occur when a radiation beam or beams pass through an organ or tissue are not accounted for.
As such when monitoring is not effected directly in the tumor but rather on the skin, or on an extracorporeal phantom such as with the methods described above, the accurate prediction of dosage to the tumor itself ad to surrounding healthy tissues is not possible.
To try and overcome the limitation inherent to these dosage monitoring methods and as such to try and minimize the damage caused to surrounding healthy tissues while maintaining effective radiation procedure, oncologist often resort to the implantation of radio-opaque metal clips at the tumor boundaries, which can be viewed by a fluoroscope, and as such assist the oncologist to pinpoint the radiation beam.
This method has very poor resolution, does not yield the dose locally absorbed by any specified organ and does not enable a closed loop control of the radiation conditions.
A more precise method for monitoring dosage at a specific treatment site is termed brachytherapy and involves surgically locating a radioactive source in the specific treatment site. Examples of brachytherpy include the implantation of radioactive capsules for a short time period into the cancerous prostate, breast, or brain. Such radioactive capsules are removed following the radiation therapy procedure. There is no control over the local dose and zone of radiation and only remote sensors and indirect calculations are used in order to provide information about the physical properties monitored, as such, the physician has to decide upon the success or damage of the treatment using semi-accurate data. Also, to obtain satisfactory clinical results, such as necrosis of the tumor, a very precise administration of the radioactive source should be kept.
To further increase the accuracy of the irradiation treatment and as such to minimize the damage inflicted upon surrounding healthy tissues several and more advanced systems and methods are utilized.
In treating some cell proliferative disorders it is possible to utilize a microsurgical spot-like radiation beam. This irradiation method allows the oncologist to precisely irradiate small and specific body sections formerly treated by brachytherapy or surgery. One such procedure incorporates what is known in the art as a gamma knife which can be operated on a tumor (in the brain for example), a blood vessel, (such as a coronary artery) where it helps in preventing cell proliferation and restenosis following balloon, stent or graft angioplasty. In a gamma knife procedure, a plurality of gamma radiation beams are directed so as to cross one another at the treatment site, so as to increase the radiative dose thereat, while, at the same time, to reduce the damage to surrounding tissues.
Yet another irradiation procedure which is
Doron Eyal
Penner Avi
Porat Yariv
Lacyk John P.
Remon Medical Technologies Ltd.
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