1. Field of the Invention
The present invention relates to methods for performing radiosurgery on a patient, and in particular, to methods for performing radiosurgery using microbeam radiation.
2. Description of the Related Art
For over a century, high energy radiation (e.g., X- and y-radiation) has been used to destroy cancerous tumors located deep within the bodies of patients. This form of cancer therapy, known as radiotherapy, is one of the three major methods for treating cancer, surgery and chemotherapy being the remaining two. Radiotherapy is widely used. Indeed, nearly 60% of all cancer patients receive radiotherapy as an element of their overall treatment protocols.
Recently, radiation has also been used to treat non-cancerous tissues which are otherwise diseased or compromised. A particularly exciting emerging medical protocol utilizes radiation to either destroy or modulate the function of brain tissue associated with psychiatric or neurological disorders. Such treatments hold the promise of curing problems such as depression, chronic pain, and obesity.
The use of radiation to treat all forms of disease and biological dysfunction is known as radiosurgery.
Conventional radiosurgery employs three methods to generate high energy radiation. In a first method, the physical phenomenon of radioactivity is used. In a second method, the physical phenomenon of bremsstrahlung (i.e., “braking radiation,” arising from decelerating charged particles) is used. In a third method, the physical phenomenon of oscillating charged particles is used.
Conventional radiosurgery systems also generate three types of radiation spatial patterns with which to expose tissue. In a first case, the spatial pattern is uniform, and is described as a broad or non-segmented beam. In a second case, the spatial pattern is comprised of a two dimensional array of substantially mutually parallel circular or rectangular beams, and is described as a grid or segmented beam. In a third case, the spatial pattern is comprised of a linear array of substantially mutually parallel rectangular beams, and is described as a segmented beam. If the diameter of the circular beams, or the width of the rectangular beams, is less than 1 mm, such beams are described as microbeams.
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A major difficulty presented by these conventional radiosurgery systems is that the radiation which destroys diseased tissue also destroys normal healthy tissue. For most conventional radiosurgery systems, this problem is dealt with by exposing the diseased tissue from several angles, thereby maximizing the dose to the diseased tissue while minimizing the dose to neighboring normal tissue. Even so, the maximum dose which can be deposited in the diseased tissue, which determines the effectiveness of the radiation in destroying the diseased tissue, is limited by the susceptibility of the neighboring normal tissue to damage.
As indicated in Slatkin et al., U.S. Pat. No. 5,339,347 (the disclosure of which is incorporated herein by reference), experiments show that microbeam radiation patterns essentially resolve the problem of damage to normal tissue. Although the normal cells in the direct path of the microbeams are destroyed, the region of destroyed cells is so narrow that the healthy cells on either side are capable of healing the damaged region of tissue. Furthermore, as shown in Dilmanian et al., U.S. Pat. No. 7,194,063 (the disclosure of which is incorporated herein by reference), there exist microbeam targeting strategies which assure the destruction of diseased tissue while sparing the functionality of neighboring normal tissue.
One problem that can disannul the effectiveness of microbeam radiosurgery, however, is tissue movement during irradiation. Such movement may arise from patient breathing, or the pulsing of blood through the tissue. Movement of the tissue effectively broadens the regions irradiated by the microbeams. As the irradiated regions become wide, the healing capability of surrounding tissue is compromised. To avoid this problem, the microbeam radiation is preferably delivered extremely quickly so that the range of tissue motion during the irradiation is sufficiently small. Thus, the radiation source providing the microbeams preferably has a high dose rate.
Of the conventional radiosurgery systems described herein (
Unfortunately, a synchrotron is a very large and expensive device. The synchrotron source which has been used for most microbeam radiosurgery experiments to date is the European Synchrotron Radiation Facility located in Grenoble, France. The storage ring associated with this synchrotron is 300 m in diameter, and the facility cost approximately $900M to construct. These characteristics of a synchrotron source prohibit widespread use of microbeam radiosurgery.
In accordance with the presently claimed invention, microbeam radiosurgery is performed by irradiating target tissue within a patient with high energy electromagnetic radiation from an inverse Compton scattering radiation source via microbeam envelopes.
In accordance with one embodiment of the presently claimed invention, a method of performing microbeam radiosurgery on a patient includes irradiating a target tissue, within a patient, with high energy electromagnetic radiation from an inverse Compton scattering radiation source via a plurality of microbeam envelopes which are mutually spatially distinct.
The following detailed description is of example embodiments of the presently claimed invention with references to the accompanying drawings. Such description is intended to be illustrative and not limiting with respect to the scope of the present invention. Such embodiments are described in sufficient detail to enable one of ordinary skill in the art to practice the subject invention, and it will be understood that other embodiments may be practiced with some variations without departing from the spirit or scope of the subject invention.
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The high energy photons 81 can be arranged into the desired pattern of one or more microbeams (e.g., as depicted in
An inverse Compton scattering source of radiation such as described above should achieve a dose delivery rate of 1×104 Gy/s. The diameter of the storage ring associated with such a source is expected to be less than 10 m, and the cost of such a source is expected to be less than $15 M.