Metal fusion bonding – Process – With shaping
Reexamination Certificate
2000-09-14
2001-10-09
Elve, M. Alexandra (Department: 1725)
Metal fusion bonding
Process
With shaping
C228S141100, C029S428000
Reexamination Certificate
active
06299054
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to treatment of age-related macular degeneration. In particular, the present invention relates to apparatus and method for X-irradiation of the macular region of the retina.
2. State of the Art
In recent years there has been a multitude of developments in the treatment of age-related macular degeneration. Macular degeneration is the leading cause of visual loss in those over the age of 50. There have been methods proposed that utilize medication, laser treatment and radiotherapy. Unfortunately, an acceptable standard treatment of this condition has not been developed. In a number of trials, retinal radiotherapy has resulted in stabilized or improved visual acuity in the majority of patients in short term follow-up with no reported significant toxicity. However, it is assumed and accepted by those skilled in this area that it is unnecessary, and potentially deleterious, to irradiate the entire retina. Those trials involving radiotherapy have been limited by the apparatus and methods presently available to the irradiation of the entire retina. It would be highly desirable to have available apparatus and methods of treating macular degeneration with radiotherapy in which irradiation is essentially limited to the macula. Such apparatus would permit precision X-irradiation of the macular region of the retina using smaller radiation fields than have been heretofore possible.
OBJECTIVES AND BRIEF DESCRIPTION OF THE INVENTION
A principal objective of the invention is to provide novel apparatus for X-irradiation of the macular region of the retina wherein the radiation fields are centered on and substantially limited to the macula, and wherein irradiation of the remainder of the retina and incidental irradiation of the lens, the cornea and the optic nerve of the eye are limited to a minimum, low level dose.
A further objective of the present invention is to provide novel apparatus having multiple conically oriented beam positions to minimize irradiation of the lens of the eye and other normal tissue, with the beam being directed through an extended collimator to minimize beam penumbra, and further wherein the collimator has an elliptical aperture that creates a circular beam image at the angle of incidence on the retina.
A still further objective of the present invention is to provide novel apparatus that incorporates a video system that enables precise alignment of the radiation beam with the macula of the eye and real-time monitoring of the position of the eye during treatment, with an electronic means further being provided to define the center of the target with respect to the actual beam image so as to overcome any inherent lack of mechanical isocentricity of the linear accelerator and associated apparatus.
An additional objective of the present invention is to provide novel apparatus having a system for positioning the patient's head in the x, y and z directions, where by the patient's eye can be properly positioned and the position can be monitored and adjusted before and during treatment.
Another objective of the present invention is to provide a novel method for making a thick lead-alloy collimator that has an elliptical aperture as small as 5 to 6 mm.
The above objectives are achieved in accordance with the present invention by providing a device for precision macular X-irradiation is directed to and essentially limited to the macular region of the retina. The device comprises a mounting plate that is mounted to a linear accelerator collimator. The mounting plate has a housing extending therefrom in which an extended cerrobend (lead alloy) secondary collimator is positioned so that the elongate aperture extending through the secondary collimator is in linear alignment with an X-ray beam from the linear accelerator collimator.
A side mounted support member is attached to the housing so that the support extends outwardly from the side of the housing. An elongate, hollow, sight tube is mounted on the support member such that the sight tube is disposed in a vertical orientation when the mounting plate of the device is mounted to a linear accelerator collimator. In a preferred embodiment of the device, the sight tube is mounted on the support member so that the sight tube can be rotated about its longitudinal axis. In addition, means are provided for insuring that the longitudinal axis of the sight tube aligns with the axis of the X-ray beam from the secondary collimator so that the axis of the sight tube and the X-ray beam intersect each other.
A light beam is transmitted down the sight tube substantially along the longitudinal axis of the light tube. Reflected light is transmitted up the sight tube from the cornea so that the impingement of the light beam on the cornea can be observed through the upper end of the sight tube. A first video camera is positioned at the upper end of the sight tube for viewing through the sight tube. The first camera is used to insure the intersection of the axis of the sight tube and the X-ray beam and to monitor and adjust the patient's eye position. A second video camera is positioned outwardly and downwardly from the lower end of the sight tube and at 90 degrees to it. The second camera is used to properly position the patient's cornea so that the retina (at known distance from the cornea) lies at the plane of intersection of the sight tube and X-ray beam.
The two cameras and the sight tube can be rotated as a unit about the longitudinal axis of the sight tube. The treatment couch on which the patient lies also rotates so that the patient while lying supine rotates about a vertical axis through the macular region of the patient's eye. This allows the X-ray beam from the secondary collimator to be directed on the macular region of the patient's eye in a series of conically coincident beams that pass by the lens of the patient's eye and impinge on the macular region of the eye as the patient is rotated beneath the lower end of the sight tube. It has been found advantageous to rotate the patient so that the patient's eye makes from one to five equal angular movements from its initial position. X-ray beams are directed at the macular region of the patient's retina during the initial position and each of the subsequent positions following an angular movement of the eye. This produces a series of separate, conically oriented beams that are directed to the macular region of the retina, with the beams being equally spaced from each other. It should be recognized, however, that the device of the present invention is useful even without the rotation of the patient. A single irradiation of the macular region is better than no treatment, but it is recognized that dose uniformity is improved with two conically coincident directions on the same plane and normal tissue sparing is further enhanced with the conical array.
It is also recognized that it is theoretically possible to rotate the patient in a continuous angular movement, with irradiation being performed continuously during the rotation of the patient. However, the apparatus for rotating the patient would have to be elaborately designed to accomplish a rather rapid rotation while maintaining the eye of the patient centered about the vertical axis through the sight tube. It is preferred to rotate the patient in discreet movements as described above. The apparatus for rotating the patient in discreet, separate motions is greatly simplified and more importantly, the operator can adjust the direction of the X-ray beam for each step to counteract any lack of mechanical isocentricity of the linear accelerator and the attached device of the present invention. It is also easier for the patient to fixate on the visual target for brief discrete intervals.
It should also be recognized that the sight tube and the two cameras need not rotate. It is sufficient to rotate the patient without concurrent rotation of the sight tube and camera system. However, it is advantageous to rot
Elve M. Alexandra
TraskBritt
University of Utah Research Foundation
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