Patent Number: 052415783
Section: abstract

An optical alignment system for aligning a film cassette carrying grid cassette with an x-ray source of a portable x-ray apparatus. To facilitate accurate alignment of the central x-ray beam of the x-ray source of a portable x-ray apparatus with a focused grid in a clinical setting, the present invention uses a light projector and a reflector device. The light projector is substantially fixed relative to the x-ray source and projects a spot or line of light on the surface of the grid cassette. The reflector device, which can be temporarily or permanently fixed to the grid cassette, includes a reflector surface and an image surface. Images of the incident light spot or line and of the reflected light spot or line are formed on the image surface, and the distance between the images indicates the magnitude of angulation alignment error between the grid cassette and the x-ray source. When beam alignment is accurate, the incident light spot or line and reflected light spot or line will be substantially superimposed, producing a single image on the reflector element. In addition, an opaque line on the transparent front surface of the collimator housing of the x-ray apparatus appears as a dark shadow within the field projected by the collimation light. Coincidence between the incident light spot or line and the shadow produced by the opaque line on the collimator serves as a distance indicator facilitating the placement of the grid cassette at the proper focal distance from the x-ray source. Further aspects of the invention include radiopaque markers which are located on front and rear surfaces of the grid cassette, and which produce images on an x-ray film when exposed. The relative positions between the images of the markers on the exposed radiographs are indicative of the amount of angulation alignment error between the grid cassette and the x-ray source. Yet another aspect of the present invention is the capability of the grid cassette to accommodate a standard x-ray film cassette in either a horizontal or vertical orientation, without reorienting the grid cassette itself.