An improved cassette and radiographic film combination

Claim 1

Cassette comprising a front element and a back element, said cassette having a combination of photosensitive elements for use in radiography, said com­bination comprising opposed intensifying screens in the interior of said cassette, a first X-ray fluorescent screen attached to said front element and a second X-ray fluorescent screen attached to said back element, a sil­ver halide photographic element between said opposed screens, said silver halide element comprising a support base and front and back silver halide emulsion layers each coated on one surface of said support wherein said front screen is arranged adjacent to said front silver halide layer and said back screen is arranged adjacent to said back silver halide layer, and wherein 1) said front screen comprises a first radiation emit­ting phosphor and said front silver halide layer compris­es silver halide grains sensitive to said first radiation emitted by said front screen, and 2) said back screen comprises a second radiation emit­ting phosphor and said back silver halide layer comprises silver halide grains sensitive to said second radiation emitted by said back screen, wherein a) said first radiation emitted by said front screen is in a first wavelength region of the electromagnetic spectrum and said second radiation emitted by said back screen is in a second wavelength region of the electro­magnetic spectrum, b) said front silver halide emulsion layer is substan­tially insensitive to said second wavelength region radi­ation emitted by said back screen, and c) said back silver halide emulsion layer is substan­tially insensitive to said first wavelength region radia­tion emitted by said front screen, the difference in wavelength region of said first and second wavelength regions and the unsensitivity of each silver halide layer to wavelength region emitted by oppo­site screen being such to reduce crossover exposure of at least 10 percent when compared with a symmetrical combi­nation of a pair of green light emitting fluorescent screens and a double-side coated green sensitized silver halide radiographic element, said cassette further having an asymmetrical system of at least one protuberance with­in said cassette and said photographic element having an asymmetrical system of at least one hole or notch which corresponds to said asymmetrical system of at least one protuberance, the correspondence between said asymmetri­cal system being such that the photographic element can fit and nest within the cassette only with said front screen directly facing said front silver halide emulsion.