Patent Number: 039379710
Section: summary

This invention relates to a shield of the kind employed in connection with radiation therapy machines to limit the area of exposure of a patient to cobalt rays or the like such that the radiation rays only strike at the very exact spot intended on the human body. In order that the rays strike only the intended spots, lead shields are positioned between the source of the cobalt rays and the patient's body such that the shields serve to protect those areas of the body that are not to be treated. Conventionally, focused shields are custom-made for each individual and contain an aperture therein having a configuration corresponding to the area of the body that is to be treated so that any cobalt rays directed to an area laterally of the aperture are blocked by the lead shield. Inasmuch as the patients normally require more than one treatment the shields must be very exact in order that the very same spot is uniformly and consistently exposed to the rays each time the patient is treated. The lead shields, which are approximately 2 inches thick, are disposed to intersect a radiation beam and thus block off all rays except those which are in a position to pass through the aperture in the shield. However, because of the thickness of the shields, as conventionally known, all of the rays entering the aperture do not necessarily exit the same because their angular disposition relative to the shield and the aperture sidewalls is such that they strike a sidewall before they have a chance to exit the aperture. Also, because of this aforementioned angularity of the rays relative to the focused shield, which is normally disposed perpendicular to the central, longitudinal axis of the radiation beam, there is also a "dead" spot below that portion of the aperture where the upper or entry edge of the aperture intersects the radiation rays proximal thereto. It is, therefore, a very important object of this invention to provide a method of fabricating a focused shield for use in connection with a radiation therapy machine or the like which the focused shield has a field of radiation aperture configured to permit precise exposure of a predetermined area of a patient's body and in which all of the radiation rays in alignment with the aperture pass therethrough to expose an area of the patient corresponding to the full area and configuration of the aperture. Another very important object of the invention is to provide a focused shield having an aperture therein through which any rays entering the aperture also exit the aperture in an unimpeded manner. It is another very important object of our invention to provide a method and apparatus for use in connection therewith for making a focused shield having an aperture therein that permits all radiation rays entering the aperture to exit therefrom in an unimpeded manner. Yet another important object of the instant invention is to provide a focused shield, as well as a method and apparatus for making the same, in which the focused shield has an aperture in which the sidewalls thereof are disposed to permit all radiation rays in alignment with the aperture to pass therethrough. A still further object of the instant invention is to provide a focused shield having a bevel-walled field of radiation aperture in which the sidewalls thereof are in substantial parallelism with the radiation rays passing through the aperture and proximal a sidewall thereof. A still further object of our invention is to provide a focused shield blank holding fixture adapted especially for use with a band saw or the like to permit cutting an aperture having the desired radiation field outline in which the sidewalls of the aperture are automatically beveled in order that the sidewalls will be substantially parallel with the radiation rays passing thereby and proximal thereto when the focused shield is inserted in a radiation therapy machine.