X-ray film cassette

An improved x-ray film cassette including a film support plate and a resilient concave-convex window member formed of a highly x-ray transparent material. The convex side of the window member is positioned facing the film supporting plate so that when the cassette is loaded with film, the window member is deformed into a substantially flat shape and the film is clamped over its entire surface area between the window member and the support plate.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to x-ray film cassettes, and more 
particularly, but not by way of limitation, to x-ray film cassettes 
commonly utilized in radiology. 
2. Description of the Prior Art 
In the practice of radiology, i.e., the photographing of organs, bones, 
etc. using x-rays, the x-ray film is commonly placed in a cassette which 
is positioned to receive x-rays after they have passed through a patient's 
body. Such cassettes generally include a flat x-ray window and a flat film 
support plate between which x-ray activated luminescent screens and the 
x-ray film are clamped. The window members of such x-ray film cassettes 
have heretofore been formed of aluminum, magnesium or plastic materials 
which are relatively x-ray opaque requiring relatively high patient x-ray 
exposure. In addition, because the window members and support plates of 
such cassettes are flat, when they are loaded with x-ray film air is often 
trapped between the luminescent screens and film causing distortion of the 
x-ray image produced on the film. 
By the present invention, an improved x-ray film cassette is provided which 
includes a window member of substantially increased x-ray transparency 
whereby patient x-ray exposure is reduced and which obviates the problems 
associated with air entrapment mentioned above. 
SUMMARY OF THE INVENTION 
An improved x-ray film cassette comprised of a frame having a resilient 
concave-convex window member attached to the top thereof and a film 
support plate hingedly attached to the bottom thereof whereby the support 
plate can be selectively moved between opened and closed positions. The 
support plate is spaced from the window member a distance such that when 
the support plate is in the closed position with x-ray film supported 
thereon, the window member is deformed into a substantially flat 
configuration and the x-ray film is clamped under pressure over its entire 
surface area between the window member and the support plate. Means for 
locking the support plate in the closed position are attached to the frame 
and/or the support plate. 
It is, therefore, a general object of the present invention to provide an 
improved x-ray film cassette. 
A further object of the present invention is the provision of an x-ray film 
cassette which includes a window member of substantially increased x-ray 
transparency as compared to heretofore used window members thereby 
substantially reducing required patient x-ray exposure. 
Yet a further object of the present invention is the provision of an 
improved x-ray film cassette which when loaded with film and one or more 
x-ray activated luminescent screens exerts pressure on the film and 
screens thereby preventing air entrapment therebetween. 
Other and further objects, features and advantages of the present invention 
will be readily apparent to those skilled in the art upon a reading of the 
description of preferred embodiments which follows when taken in 
conjunction with the accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring now to the drawings, the improved x-ray film cassette of the 
present invention is illustrated and generally designated by the numeral 
10. The cassette 10 is comprised of an open rectangular frame 12 formed of 
elements having inverted L-shaped in cross section whereby vertical sides 
14 and a continuous inwardly extending top flange portion 16 are provided. 
A flat rectangular film support plate 18 for closing the open bottom of the 
frame 12 is hingedly attached thereto by one or more pins 20 or other 
suitable hinge means so that the film support plate 18 can be moved 
between the closed position illustrated in FIG. 2 and the open position 
illustrated in FIG. 3. The frame 12 and plate 18 can be formed from any 
suitable strong durable material such as aluminum, stainless steel or 
plastic materials, and suitable means for locking the film support plate 
18 in a closed position are provided attached to the frame 12 and/or the 
support plate 18. For example, one or more wing members 22 can be 
rotatably attached to the bottom of the side 14 of the frame 12 opposite 
the hinge means 20 which upon rotation provide outwardly extending 
shoulders for maintaining the film support plate 18 in the closed 
position. 
An x-ray window member 24 is movably retained within the interior of the 
frame 12 beneath the inwardly extending flange portion 16 thereof by means 
of a plurality of inserts or other suitable means 26 attached to the sides 
14 of the frame 12. The window member 24 is concave-convex in shape and is 
formed of a resilient highly x-ray transparent material which will be 
described further hereinbelow. As best shown in FIG. 3, the window member 
24 is positioned within the frame 12 so that the convex side 28 of the 
window member 24 faces the film support plate 18. 
Attached to the side 28 of the window member 24 is a uniform layer of a 
compressible material 30, e.g., felt, and attached to the compressible 
material 30 is a conventional x-ray activated luminescent screen 32 of the 
type conventionally used with x-ray film to illuminate the x-ray image 
produced. A uniform layer of compressible material 34 is also attached to 
the upper surface of the support plate 18 with a second luminescent screen 
36 attached to the material 34. 
The concave-convex window member 24 is preferably formed from a material 
which retains its resiliency over a long period of time and which is 
substantially more x-ray transparent than heretofore used materials 
thereby allowing the production of an x-ray film with substantially less 
patient x-ray exposure. A material having such properties which has been 
found to be particularly suitable for use in accordance with the present 
invention is comprised of powdered carbon and a fibrous material held in a 
matrix of cured plastic material. 
Particularly suitable fibrous materials for forming the window member 34 
are carbon filaments and synthetic organic fibers. Of the organic fibers 
which can be used, a product of I. E. duPont de Nemours and Company, which 
is comprised of fibers having an average diameter of about 0.0005 inch, 
marketed under the trademark "KEVLAR" is preferred. Carbon filaments 
having an average diameter of 0.007 inch are preferred, e.g., the carbon 
filament product commercially available from the Carbon Products Division 
of Union Carbide Corporation under the trade name "THORNEL," and both the 
carbon filaments and organic fibers are formed into tows of about 6000 
filaments or mats of woven or randomly oriented filaments. 
The tows of fibrous material are impregnated with a curable plastic 
material, such as by passing the tows through a liquid body of the 
material, and are laid up in a side-by-side relationship to form a layer 
or "tape" of desired width. The impregnated tape is then cut into sections 
which are stacked one on top of the other in a curing fixture in a manner 
whereby the tows forming adjacent layers are positioned transversely to 
each other, preferably perpendicularly to each other followed by the 
curing of the plastic material utilized. When mats of fibrous material are 
included in the composite material, they are also impregnated with the 
curable plastic material and are positioned between two or more sections 
of impregnated tape. 
A variety of thermoplastic or thermosetting materials can be utilized 
including, but not limited to, resins such as polyester, epoxy, phenolic, 
ploypropylene, polystyrene, nylon, polycarbonate, polyurethane and 
polyphenolene oxides. Thermosetting resins are most suitable for use in 
forming the window member of the present invention. Thermosetting phenolic 
resins are preferred with phenolformaldehyde resins such as bisphenol 
A-novalak being the most preferred. The x-ray transparent fibrous 
materials mentioned above, i.e., carbon filaments and synthetic organic 
fibers are substantially x-ray transparent, but all of the various 
thermoplastic and thermosetting materials mentioned above are relatively 
opaque to x-rays. In order to minimize the quantity of thermoplastic or 
thermosetting material present in the window member 24, powdered carbon is 
preferably mixed with the thermoplastic or thermosetting material utilized 
in the amount of about 20 percent by volume of the mixture. The stacked 
sections of tape or mat are preferably impregnated with the mixture of 
thermoplastic or thermosetting material and powdered carbon in an amount 
of about 40 percent by weight of the fibrous material and mixture, so that 
when the stacked sections are squeezed or compressed under pressure, 
excess amounts of the mixture are removed from the sections and the 
powdered carbon is distributed throughout the resultant composite 
material. The powdered carbon fills voids between the tape sections and 
between the tows forming the sections displacing the thermoplastic or 
thermosetting material therefrom and providing a carbon-fiber uniformity 
to the finished composite material, all of which substantially improves 
the x-ray transparency of the composite material as compared to the 
materials utilized heretofore. As will be understood, the transversely 
stacked tows of fibrous material present in the composite material gives 
the material extremely high tensile strength even when formed in very thin 
sheets. 
The particular number of transversely stacked sections or layers of the 
impregnated tape utilized to form the window member 24 determines the 
thickness, flexibility and strength of the member as well as whether the 
member is flat or curved. When an even number of transversely laid-up 
sections or layers of the tape are utilized, the member is unbalanced, 
i.e., the tows of the top and bottom layers are positioned transversely to 
each other, and upon being removed from the curing fixture, the member 
takes on a curved shape, i.e., a shape corresponding to the arc of a 
circle. When an odd number of layers are utilized, the resulting member is 
balanced, i.e., the tows of the top and bottom layers are parallel, and 
will remain flat when removed from the curing fixture. A curved unbalanced 
panel of the composite material is utilized for the window member 24. When 
the curved panel is placed in the frame 12 of the cassette 10 it takes on 
the concave-convex shape described above and illustrated in the drawings. 
For example, a four layer panel formed of powdered carbon, carbon 
filaments and bisphenol A-novalak resin cured at a temperature of about 
300.degree. F. while maintaining a pressure thereon of about 1000 psig for 
a period of about 60 minutes is curved and has a thickness of about 0.020 
inch. 
The window member 24 can include one or more mats or carbon filaments or 
organic fibers positioned between tapes of either fibrous material or the 
member can be formed entirely of stacked mats. The use of mats in forming 
the surface is economically advantageous since the fibrous materials in 
mat form are less expensive to produce than in tape form. 
In operation of the cassette 10, the film support plate 18 is opened as 
shown in FIG. 3, and a section of conventional x-ray film 38 is placed on 
top of the screen 36 and compressible material 34 attached to the plate 
18. The plate 18 is then moved to the closed position and locked in place 
as shown in FIG. 2. As the plate 18 is moved to the locked position, the 
film 38 contacts the screen 32 and compressible material 30 attached to 
the window member 24 and forces the window member 24 upwardly whereby it 
is deformed into a substantially flat configuration. As the window member 
24 is deformed into the flat configuration, the peripheral edges thereof 
are moved inwardly within the frame 12. The deformation of the window 
member 24 exerts pressure against the film support plate which results in 
the x-ray film being clamped under pressure over its entire surface area 
between the window member 24 and support plate 18 thereby insuring that 
air is not trapped between the film 38 and the screens 32 and 36. 
Thus, by the present invention, an improved x-ray film cassette is provided 
which prevents air from being trapped between the x-ray film and 
luminescent screens utilized, and in addition, reduces patient x-ray 
exposure due to the substantially increased x-ray transparency of the 
material from which the x-ray window 24 is formed. While presently 
preferred embodiments of the invention have been described for purposes of 
this disclosure, numerous changes in the construction and arrangement of 
parts can be made, which changes are encompassed within the spirit of this 
invention as defined by the appended claims.