CA1086124A - Radiographic film cassette with flexible foil cover - Google Patents
Radiographic film cassette with flexible foil coverInfo
- Publication number
- CA1086124A CA1086124A CA280,431A CA280431A CA1086124A CA 1086124 A CA1086124 A CA 1086124A CA 280431 A CA280431 A CA 280431A CA 1086124 A CA1086124 A CA 1086124A
- Authority
- CA
- Canada
- Prior art keywords
- radiographic film
- cassette according
- film cassette
- cover
- cassette
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B42/00—Obtaining records using waves other than optical waves; Visualisation of such records by using optical means
- G03B42/02—Obtaining records using waves other than optical waves; Visualisation of such records by using optical means using X-rays
- G03B42/04—Holders for X-ray films
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Radiography Using Non-Light Waves (AREA)
- Conversion Of X-Rays Into Visible Images (AREA)
- Apparatus For Radiation Diagnosis (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A radiographic cassette comprises a bottom and a cover capable of being locked together. The cover has a part of its normally rigid structure replaced by a flexible foil which, when vacuum is applied to the interior of the cassette, exerts a pressure upon the film/screen combination contained within the latter. In this way an intimate contact between the film and the screen is established and in the mean time the distance between the film/screen combination and the object to be radiographed is reduced to a minimum due to the small thickness of the foil.
The cassette may be used in the field of high-definition radiography especially for mammography.
A radiographic cassette comprises a bottom and a cover capable of being locked together. The cover has a part of its normally rigid structure replaced by a flexible foil which, when vacuum is applied to the interior of the cassette, exerts a pressure upon the film/screen combination contained within the latter. In this way an intimate contact between the film and the screen is established and in the mean time the distance between the film/screen combination and the object to be radiographed is reduced to a minimum due to the small thickness of the foil.
The cassette may be used in the field of high-definition radiography especially for mammography.
Description
L2~
~ his invention relates to radiographic film cassettes and more particularly to radiographic film cassettes having improved sharpness characteristics.
Present day radiographic techniques in which great im~
portance is attached to high resolving power of the recording cycle, require the use of so-called "sof-t" X-rays, which means that a relatively low voltage is applied -to the X-ray source so that a radiation is obtained which is of a ra-ther long wave-length.
In contrast to -the use of a radiation of shorter wave-length (or harder X-radiation), the radiation absorption is more pronounced. ~he choice of the soft range in the radio-graphic spectrum results in that even small or thin irregu-larities produce such a decrease in radiation intensity that a clearly discerneable contrast upon the radiographic recording material is obtained after processing the latter.
An inconvenience o~ "soft" X-rays, however, resides in the fact that they are very liable to become scattered and that, therefore, extreme care must be taken in order to guarantee an intimate con-tact between the radiographic film and the fluorescent screen(s). Moreover, the distance between ; the film/screen sandwich and the obJect to be radiographed should be as small as possible.
In order to, at least partially, fulfil these requiremcn-ts generally use is made of radiographic film cassettes of rather conventional design which, prior to exposure, are connec-ted GV.893 PCT - 1 -, ~
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to a suitable source of vacuum so that an intimate contact be-tween the film and fluorescent screen(s) is established as a result of the atmospheric pressure acting upon the casse-tte bottom and cover.
~ he design of this -type of cassettes has the drawback that the cover, facing the source of radia-tion and which is usually made of metal, absorbs already a substantial part of ` the soft radiation, which resul-ts in the need for increasing the radiation dose. It must also be noted -that the distance between -the film/screen combina-tion and the object to be radiographed is still considerable due to the thickness of the cassette cover.
Another method for locating the radiographic film durin~
exposure consists in placing the recording material, whether or not accompanied by one or two fluorescent screens, in a light-tight bag of polymeric material and heat-sealing the bag while applying vacuum to the interior of it. By this means a thin radiographic recording unit is obtained which does not show a significant absorption in respect of the in-
~ his invention relates to radiographic film cassettes and more particularly to radiographic film cassettes having improved sharpness characteristics.
Present day radiographic techniques in which great im~
portance is attached to high resolving power of the recording cycle, require the use of so-called "sof-t" X-rays, which means that a relatively low voltage is applied -to the X-ray source so that a radiation is obtained which is of a ra-ther long wave-length.
In contrast to -the use of a radiation of shorter wave-length (or harder X-radiation), the radiation absorption is more pronounced. ~he choice of the soft range in the radio-graphic spectrum results in that even small or thin irregu-larities produce such a decrease in radiation intensity that a clearly discerneable contrast upon the radiographic recording material is obtained after processing the latter.
An inconvenience o~ "soft" X-rays, however, resides in the fact that they are very liable to become scattered and that, therefore, extreme care must be taken in order to guarantee an intimate con-tact between the radiographic film and the fluorescent screen(s). Moreover, the distance between ; the film/screen sandwich and the obJect to be radiographed should be as small as possible.
In order to, at least partially, fulfil these requiremcn-ts generally use is made of radiographic film cassettes of rather conventional design which, prior to exposure, are connec-ted GV.893 PCT - 1 -, ~
, ~
.... . . ~, : - ~ . :.
to a suitable source of vacuum so that an intimate contact be-tween the film and fluorescent screen(s) is established as a result of the atmospheric pressure acting upon the casse-tte bottom and cover.
~ he design of this -type of cassettes has the drawback that the cover, facing the source of radia-tion and which is usually made of metal, absorbs already a substantial part of ` the soft radiation, which resul-ts in the need for increasing the radiation dose. It must also be noted -that the distance between -the film/screen combina-tion and the object to be radiographed is still considerable due to the thickness of the cassette cover.
Another method for locating the radiographic film durin~
exposure consists in placing the recording material, whether or not accompanied by one or two fluorescent screens, in a light-tight bag of polymeric material and heat-sealing the bag while applying vacuum to the interior of it. By this means a thin radiographic recording unit is obtained which does not show a significant absorption in respect of the in-
2~ cident rays, and which at the same time, because the bag wall ~; may be very thin, permits the set formed by the film/screen combination to be located very close to the object to be radiographed.
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Unfortunately, when the bag is opened by means of acutting tool, such as a pair of scissors, part of the useful space always ~ets lost, so that the number of times such a GV.893 PC~ -- 2 -,~., ,:
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bag may be used is ra-ther limited. After -two or three exposures, the dimensions of the bag may have diminished to such an extent that it will no longer hold a film of a given format. The unavoidable flexure of the film/screen set may also lead to difficulties with respect to a correc-t positioning. An analogous drawback may be noticed when employing radiographic film casset-tes of classical design but which are made of a flexible material, such as polymer , , .
; material.
I-t is therefore an obaect of the invention to provide a radiographic film cassette which does not show the inconve- -nierces of the above mentioned prior art devices.
l According to the invention, there is provided :
A radiographic film cassette comprising a bottom and a cover hingc~l~c connected~to each other and fatening means, said bottom and said cover when closed and fastened form a light-tight enclosure in which a radiographic film sheet can be accommodated,the cover being formed in part by a flexible foil which is transparent to penetrating radiation and extends over part of the plan area of the cassette, and in part by a less flexible marginal-portion to which said foil is connec-ted and that has a thickness that is greater than that of the flexible foil,and comprising at least one exhaust opening via which air can be aspirated from the interlor of the closed and fastened cassette to cause atmospheric pressure to be - exerted on said screen and film system via said foil.
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In the foregoing, -the "plan area" of the cassette must be in-terpreted as the area occupied by the clos~d cassette viewed normally to -the plane in which it holds a film sheet.
The "cover" means tha-t ~ler~ber which is turned towards the X-ray source and upon which the object to be radiographed is positioned.
A radiographic casse-tte of this design combines the advantages of a classical radiographic film casse-t-te and -the polymeric bag in that on the one hand it is undeformable ~ 10 due -to the combined rigidity of the bo-ttom and the cover as ; they are locked -together and on the other hand by the fact that the distance between the objec-t to be radiographed and the set of film/screen is limited -to the thickness of the flexible foll only.
A preferred field of application of the cassette according to the invention are mammography techniques.
The cassette may be designed so that it can be fastened or unfastened automa-tically by mechanisms forming part of an automatic cassette loading and/or unloading apparatus, e.g. an apparatus which can operate in a well-lit room.
~ he latter possibility may be of importance when radio-graphic examinations are carried out by ambulant teams which do not dispose of the classical hospital facilities.
., ,',7 Preferably, the bottom of the cassette is provided with ... .
an intensifying screen.
In order to increase the efficiency of the vacuum, :
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supplementary sealing expedients may be provided in the cassette, so that it is not necessary to maintain the source of vacuum in operà-tion after a sufficiently low pressure has been established in the cassette. It will also be clear that the aspira~ing means may be equipped wi-th means which provide or at leas-t ~acilitate the a-tmospheric pressure restoration once the exposure has taken place. In ~act the ~i exposure cycle which comprises -the loading of the casse~tte, the application of vacuu~, the exposure i-tself, the release of the vacuum and the unloading of ~the cassette in a magazine or direc-tly into a processing apparatus may be carried out -fully automatically.
In a preferred embodiment, the flexible foil occupies ,`
at least 60% of -the plan area of the cassette. ~he foil itself has a thickness o~ not more than 0.5 millimeter and , is advantageously composed of a polymer material, preferably polyethylene, in which carbon black is dispersed as opaci-~ fying agent.
', ~he cassette according to the invention may be designed in such a manner that it may coopera-te with a gripping element located at the exposure station of a mammographic X-ray table, in which element also means are provided for automatically connecting the vacuum means with the vacuum valve of the cassette. In this way a reproducible positioning of the cassette is possible and in the meantime excessive time losses due to occasional bad connections are avoided.
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~ he scope and spirit of the inven-tion will be understood in a clearer way at -the hand of a detailed description of a preferred embodimen-t and in -the light of -the accompanying drawings in which :
~ig. 1 is a longitudinal cross-sectional view according to the line 1-1' in l'ig. 3 and 3-3' in fig. 4 of` a r~dio-graphic film cassette according -to the invention, Fig. 2 is a longitudinal cross-sectional view according to the line 2-2' in fig. 3 and 3-3' in fig. 4 of a radio-graphic film casse-tte as illustrated in fig. 1 (showing small structural differences) when the cassette is partl~-opened, Fig. 3 is an under-plan view of the cover, ~ig. 4 is an under-plan view of the bo-t-tom, ~ig. 5 is a top view of another embodiment of a cassette according to the invention and ~ig. 6 is a cross-sec-tional view of an alternative embodiment of the cassette according to the invention.
As illustrated in figs. 1 and 2, the radiographic film cassette 10 according to -the invention comprises a bottom ~` 11 and a cover 12 which are hingingly connected -to each other with the help of hinges 13 (only one being shown~. ~he cover 12 and the bottom 11 represented in the form of a sandwich - structure in fig. 1 may be made of a metal such as aluminium or of a polymeric material having a high degree of stiffness~
and is so designed that its dimensions enable the use of current format radiographic films and their incorporation GV.893 PC~ - 6 -., 1~ `.i , ,. .,,- ,- - , ,. ~ , : , :. - ~ , :, . .
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in exposure apparatus. The bo-t-tom 11 bears an intensifying screen 17 which may be resilien-tly sup~orted and which is intended to increase the yield of the conversion of pene-trating radiation into a latent image built-up in the radiographic film contained in the cassette.
Par-t o~ the sur~ace area of -the cover 12 consists o~
a flexible foil 16 which is opaque to visible light but which transmits the penetra-ting radia-tion creating a latent image. The purpose of this foil 16 is to ~uarantee àn optimum contact with -the film 28 and the intensifying screen 17 so that sca-ttering or other quality decreasing phenomena may be avoided to a large extent. ~his in-timate contact is made possible by the application of a vacuum in the inner space of the cassette 10 after locking the latter with the help of locking mechanism 14, 15, so -that the a-tmospheric pressure tends to flex the flexible foil 16, and that as a consequence a firm contact between the latter and the film 28 is establishedO In order to evacuate the inner spaGe a usual vacuum valve 18 is provided in one o~ the corners of , ,, the cover frame 12 which valve may be connected to a suitable source of vacuum (not shown). In case the flexible foil 16 is connected with only the cover 12, the vacuum is malntained i during the exposure. When however the flexible foil has twice its original length (as especially illustrated in fig.2) < and continues under the whole area of the intensifying screen 'i 17, or when supplementary sealing means as for example a . i ~ GV.893 PCT - 7 -., .
.;. . . .. , ~ : ,. .-.. ~ : , . . . .
6~24 strip of silicone rubber 27 (see again fig. 1) is provided, the connection to the vacuum source may be -terminated once a sufficiently low pressure has been established in the cassette. ~he good working of the cassette is already guaranteed when the vacuum within -the inner space of the cassette attains 7000 mm of water column or less.
Fig. 3 is an under plan view of -the cover 12 of -the cassette. It comprises a rigid U-shaped member 19 which is provided with an upstanding ridge 20 which is capable to disappear in a correspo~ding groove (see fig. 4) provided in the bottom 11 of the casse-tteO ~he flexible foil ~6 of rectangular shape is secured to -the U-shaped member 19 by known mea~s such as adhesive, heat sealing, etc., over about three quarters of its periphery. The residual part 24 partly extends under the intensifying screen 17, and by closing the cassette a relatively air-tight unit is obtained.
The space 21 defined by the upstanding ridge 20 and the , upstanding wall 22 of the cover may be provided with supple-mentary sealing means 27 of resilient nature (only parts of said means have been illustrated for the sake of clearness).
The area occupied by the flexible foil 16 is of such shape and dimensions -that -there is ample space in order to locate the objects (for example a breast) to be radiographed in an easy manner9 even after partly compressing the latters.
`~ At the end of the legs of the U-shaped member ~9, there i are provided small recesses 25 and 26, which serve to house one element of the hinges 13 (see also fig. 1).
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r~he flexible foil 16 is made from a flexible polymeric foil such as polye-thylene in which carbon black has been previously dispersed as opacifying agent.
~ ig. 4 illustra-tes an under-plan view of the bottom 11.
It cornprises a rigid plate 30 in which a groove 31 is provided, extending over abou-t three quarter60f i-ts periphery and ~rhich serves for receiving the upstanding ridge 20 of the cover ~2 (see preceding fig~ 3). At -the inside of the bottom 12, an intensifying screen 17 is provided w~ich is mounted onto the inner surface of -the pla-te 30 and the dimensions of said ` screen are about -the same as the format of -the radiographic film (not shown) which is to be exposed. If desired, a portion 24 of the flexible foil may, as shown, extend under said intensifying screen 17 in order -to increase the air-tightness of the whole arrangement.
It will be clear that when providing a flexible foil (which in figs. 3 and 4 is denoted by 16) of a width exceeding the distance between opposite edges of the groove 31, as sho~m by dotted lines 16', the air-tightness reaches a very high accura~ as part of the flexible foil is urged into the space defined by the groove 31 o~ the bottom 11 and the ridge 20 of the cover 12, so forming a kind of alr-tight bag when closing the cassette.
In the bottom 11 are also provided recesses 32 and 33 in which the second element of hinges 13 may be located.
~ As may be derived from the foregoing, when closing the -l cassette, the flexible ~oil 16 (or 16') folds itself about '; GV.893 PCr~ _ 9 _ , .: .
its edge ~3.
A member 34 which par-tly projects from the bottom 11 and fixedly connected therewi-th enables the bottom 1~ to be taken hold of by means of an appropriate mechanism and to further open the cassette, once the locking/unlocking 14, 15 mechanism (~ig. 1) is in i-ts unlocking position. ~his feature makes possible to incorporate -the casse-tte according to the invention in-to already existing daylight loading/
unloading systems or into daylight loading/unloading ~ys-tems, especially adapted or designed for this -type of cassette.
In fig. 5 is illustra-ted a top view of another preferred embodimen-t of a cassette 10, according to the invention which ~` is provided with supplementary expedients in order to increase its ergonomic properties. ~he casset-te 10 comprises a bottom ;!
11 (of which only the side edges may be seen) and a cover 12 '1 which are hingingly connected with each other. Suitable locking means 14 are provided. In contrast to the cassette ~t of fig. 1, the locking means are located in the side walls of -the cassette and may comprise a pin fixedly connected to . .
.
the cover 12 and a yieldi~gly biased slot which is located on a rail or in a groove fixedly connected with -the bottom 11 .
` wherein the pin and slot are capable of engaging each other ~; when exerting a pressure on the cover ~2. As this locking/
, , unlocking means is no part of the invention i-t has not been represented in detail. ~he cover 12 of which a part is formed by a flexible foil 16 is provided wi-th means which permit j .
-the film to be provided with supplementary data related to .. : , ,l GV.893 PC~ - 10 -'' :
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-the person or to -the objec-t to be radiographed.
So are provided first identification means 40,41,42 which enable to print additional informa-tion related -to -the person to be radiographed upon the film (not shown). ~he said identification means comprise a small chamber ~0 in which a slide 41 is located and which slide 41, by pushing -the knob 42 in downward direction, may perform a transla-tional movement into -the chamber 40, so providing a small rec-tangular opening in the cover ~2. At -tha-t moment data carrying means (not shown) such as a smal:L typewritten card may be placed into a special exposure unit (not shown) which,by means of a small light source, prints -the data upon the film via the above mentioned opening in the cover. ~he slide 41 may be resilien-tly biased in the chamber 40, so that upon withdrawing the casse-tte ~0 from the special exposure unit the slide 41 automatically closes again in a light-tight manner.
~here are also provided second identification means for printing supplementary data upon the film during its exposure to penetrating radiation.
. Especially in mammography in which generally two practi-cally identical objects are radiographed, it is desirable to dispose of identification upon the film which positively indicates whether it is the left or the right breast which is represented on the radiographic record.
As such, symbols 45 or 46 provided on a slide 4~ and associated with respectively the left or right side of the GV.893 PC~ - 11 _ - j Z~
pa-tien-t are flxedly loca-ted in the cover 12 of t~e cassette.
~he slide ~3 made of a material opaque to pene-trating radia-tion and having an opening 44 may -take a dual position in that the opening 44 may be positioned either over the symbol 45 or over the symbol 46.
The said symbols 45 and 46, which are made of a pene-trating radiation absorbing ma-terial, such as lead, intercep-~-the radiation during exposure, so -that after processing the film a white area in the form of the symbol is obtained there-on. ~he circles 50 and 51 represen-t -the areas on which cover lifting means (such as sucker cups) may be located for opening -the cassette when the latter is incorporated into or forms part of a daylight loading/unloading system.
~ inally, fig. 6 shows an alternative embodiment of -the cassette 10 of fig. 1, in which a second intensifying screen 29 is connected to the flexible foil 16 on the cover 12.
~his second intensifying screen 29 contributes positively to a substantial decrease of the radiation dose by the fact that the radiographic film 28, having in general a penetra-ting radiation sensitive coating on either side, will be exposed to the light emitted by both intensifying screens 17 and 29, which means that the radiation dose may practically be halved.
~he second intensifying screen 29 may be secured to the ; flexible foil 16 by known means such as pressure adhesive tape. If desired, the side of the flexible foil 16 facing the inner space of the cassette itself may be provided with ,7 a fluorescent coating, so that the use of a separate support ` GV.893 PC~ - 12 -.-.
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. for this coating may be dispensed wi-th.
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Unfortunately, when the bag is opened by means of acutting tool, such as a pair of scissors, part of the useful space always ~ets lost, so that the number of times such a GV.893 PC~ -- 2 -,~., ,:
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bag may be used is ra-ther limited. After -two or three exposures, the dimensions of the bag may have diminished to such an extent that it will no longer hold a film of a given format. The unavoidable flexure of the film/screen set may also lead to difficulties with respect to a correc-t positioning. An analogous drawback may be noticed when employing radiographic film casset-tes of classical design but which are made of a flexible material, such as polymer , , .
; material.
I-t is therefore an obaect of the invention to provide a radiographic film cassette which does not show the inconve- -nierces of the above mentioned prior art devices.
l According to the invention, there is provided :
A radiographic film cassette comprising a bottom and a cover hingc~l~c connected~to each other and fatening means, said bottom and said cover when closed and fastened form a light-tight enclosure in which a radiographic film sheet can be accommodated,the cover being formed in part by a flexible foil which is transparent to penetrating radiation and extends over part of the plan area of the cassette, and in part by a less flexible marginal-portion to which said foil is connec-ted and that has a thickness that is greater than that of the flexible foil,and comprising at least one exhaust opening via which air can be aspirated from the interlor of the closed and fastened cassette to cause atmospheric pressure to be - exerted on said screen and film system via said foil.
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GV.893 PCT _ 3 _ , . .
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In the foregoing, -the "plan area" of the cassette must be in-terpreted as the area occupied by the clos~d cassette viewed normally to -the plane in which it holds a film sheet.
The "cover" means tha-t ~ler~ber which is turned towards the X-ray source and upon which the object to be radiographed is positioned.
A radiographic casse-tte of this design combines the advantages of a classical radiographic film casse-t-te and -the polymeric bag in that on the one hand it is undeformable ~ 10 due -to the combined rigidity of the bo-ttom and the cover as ; they are locked -together and on the other hand by the fact that the distance between the objec-t to be radiographed and the set of film/screen is limited -to the thickness of the flexible foll only.
A preferred field of application of the cassette according to the invention are mammography techniques.
The cassette may be designed so that it can be fastened or unfastened automa-tically by mechanisms forming part of an automatic cassette loading and/or unloading apparatus, e.g. an apparatus which can operate in a well-lit room.
~ he latter possibility may be of importance when radio-graphic examinations are carried out by ambulant teams which do not dispose of the classical hospital facilities.
., ,',7 Preferably, the bottom of the cassette is provided with ... .
an intensifying screen.
In order to increase the efficiency of the vacuum, :
GV.893 PvT - 4 -, .
. .
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supplementary sealing expedients may be provided in the cassette, so that it is not necessary to maintain the source of vacuum in operà-tion after a sufficiently low pressure has been established in the cassette. It will also be clear that the aspira~ing means may be equipped wi-th means which provide or at leas-t ~acilitate the a-tmospheric pressure restoration once the exposure has taken place. In ~act the ~i exposure cycle which comprises -the loading of the casse~tte, the application of vacuu~, the exposure i-tself, the release of the vacuum and the unloading of ~the cassette in a magazine or direc-tly into a processing apparatus may be carried out -fully automatically.
In a preferred embodiment, the flexible foil occupies ,`
at least 60% of -the plan area of the cassette. ~he foil itself has a thickness o~ not more than 0.5 millimeter and , is advantageously composed of a polymer material, preferably polyethylene, in which carbon black is dispersed as opaci-~ fying agent.
', ~he cassette according to the invention may be designed in such a manner that it may coopera-te with a gripping element located at the exposure station of a mammographic X-ray table, in which element also means are provided for automatically connecting the vacuum means with the vacuum valve of the cassette. In this way a reproducible positioning of the cassette is possible and in the meantime excessive time losses due to occasional bad connections are avoided.
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~ he scope and spirit of the inven-tion will be understood in a clearer way at -the hand of a detailed description of a preferred embodimen-t and in -the light of -the accompanying drawings in which :
~ig. 1 is a longitudinal cross-sectional view according to the line 1-1' in l'ig. 3 and 3-3' in fig. 4 of` a r~dio-graphic film cassette according -to the invention, Fig. 2 is a longitudinal cross-sectional view according to the line 2-2' in fig. 3 and 3-3' in fig. 4 of a radio-graphic film casse-tte as illustrated in fig. 1 (showing small structural differences) when the cassette is partl~-opened, Fig. 3 is an under-plan view of the cover, ~ig. 4 is an under-plan view of the bo-t-tom, ~ig. 5 is a top view of another embodiment of a cassette according to the invention and ~ig. 6 is a cross-sec-tional view of an alternative embodiment of the cassette according to the invention.
As illustrated in figs. 1 and 2, the radiographic film cassette 10 according to -the invention comprises a bottom ~` 11 and a cover 12 which are hingingly connected -to each other with the help of hinges 13 (only one being shown~. ~he cover 12 and the bottom 11 represented in the form of a sandwich - structure in fig. 1 may be made of a metal such as aluminium or of a polymeric material having a high degree of stiffness~
and is so designed that its dimensions enable the use of current format radiographic films and their incorporation GV.893 PC~ - 6 -., 1~ `.i , ,. .,,- ,- - , ,. ~ , : , :. - ~ , :, . .
6~LZ4 .
in exposure apparatus. The bo-t-tom 11 bears an intensifying screen 17 which may be resilien-tly sup~orted and which is intended to increase the yield of the conversion of pene-trating radiation into a latent image built-up in the radiographic film contained in the cassette.
Par-t o~ the sur~ace area of -the cover 12 consists o~
a flexible foil 16 which is opaque to visible light but which transmits the penetra-ting radia-tion creating a latent image. The purpose of this foil 16 is to ~uarantee àn optimum contact with -the film 28 and the intensifying screen 17 so that sca-ttering or other quality decreasing phenomena may be avoided to a large extent. ~his in-timate contact is made possible by the application of a vacuum in the inner space of the cassette 10 after locking the latter with the help of locking mechanism 14, 15, so -that the a-tmospheric pressure tends to flex the flexible foil 16, and that as a consequence a firm contact between the latter and the film 28 is establishedO In order to evacuate the inner spaGe a usual vacuum valve 18 is provided in one o~ the corners of , ,, the cover frame 12 which valve may be connected to a suitable source of vacuum (not shown). In case the flexible foil 16 is connected with only the cover 12, the vacuum is malntained i during the exposure. When however the flexible foil has twice its original length (as especially illustrated in fig.2) < and continues under the whole area of the intensifying screen 'i 17, or when supplementary sealing means as for example a . i ~ GV.893 PCT - 7 -., .
.;. . . .. , ~ : ,. .-.. ~ : , . . . .
6~24 strip of silicone rubber 27 (see again fig. 1) is provided, the connection to the vacuum source may be -terminated once a sufficiently low pressure has been established in the cassette. ~he good working of the cassette is already guaranteed when the vacuum within -the inner space of the cassette attains 7000 mm of water column or less.
Fig. 3 is an under plan view of -the cover 12 of -the cassette. It comprises a rigid U-shaped member 19 which is provided with an upstanding ridge 20 which is capable to disappear in a correspo~ding groove (see fig. 4) provided in the bottom 11 of the casse-tteO ~he flexible foil ~6 of rectangular shape is secured to -the U-shaped member 19 by known mea~s such as adhesive, heat sealing, etc., over about three quarters of its periphery. The residual part 24 partly extends under the intensifying screen 17, and by closing the cassette a relatively air-tight unit is obtained.
The space 21 defined by the upstanding ridge 20 and the , upstanding wall 22 of the cover may be provided with supple-mentary sealing means 27 of resilient nature (only parts of said means have been illustrated for the sake of clearness).
The area occupied by the flexible foil 16 is of such shape and dimensions -that -there is ample space in order to locate the objects (for example a breast) to be radiographed in an easy manner9 even after partly compressing the latters.
`~ At the end of the legs of the U-shaped member ~9, there i are provided small recesses 25 and 26, which serve to house one element of the hinges 13 (see also fig. 1).
~;; GV.893 PCT - 8 -`
., .... . .. .. .. . . . : . . . . .
6~
r~he flexible foil 16 is made from a flexible polymeric foil such as polye-thylene in which carbon black has been previously dispersed as opacifying agent.
~ ig. 4 illustra-tes an under-plan view of the bottom 11.
It cornprises a rigid plate 30 in which a groove 31 is provided, extending over abou-t three quarter60f i-ts periphery and ~rhich serves for receiving the upstanding ridge 20 of the cover ~2 (see preceding fig~ 3). At -the inside of the bottom 12, an intensifying screen 17 is provided w~ich is mounted onto the inner surface of -the pla-te 30 and the dimensions of said ` screen are about -the same as the format of -the radiographic film (not shown) which is to be exposed. If desired, a portion 24 of the flexible foil may, as shown, extend under said intensifying screen 17 in order -to increase the air-tightness of the whole arrangement.
It will be clear that when providing a flexible foil (which in figs. 3 and 4 is denoted by 16) of a width exceeding the distance between opposite edges of the groove 31, as sho~m by dotted lines 16', the air-tightness reaches a very high accura~ as part of the flexible foil is urged into the space defined by the groove 31 o~ the bottom 11 and the ridge 20 of the cover 12, so forming a kind of alr-tight bag when closing the cassette.
In the bottom 11 are also provided recesses 32 and 33 in which the second element of hinges 13 may be located.
~ As may be derived from the foregoing, when closing the -l cassette, the flexible ~oil 16 (or 16') folds itself about '; GV.893 PCr~ _ 9 _ , .: .
its edge ~3.
A member 34 which par-tly projects from the bottom 11 and fixedly connected therewi-th enables the bottom 1~ to be taken hold of by means of an appropriate mechanism and to further open the cassette, once the locking/unlocking 14, 15 mechanism (~ig. 1) is in i-ts unlocking position. ~his feature makes possible to incorporate -the casse-tte according to the invention in-to already existing daylight loading/
unloading systems or into daylight loading/unloading ~ys-tems, especially adapted or designed for this -type of cassette.
In fig. 5 is illustra-ted a top view of another preferred embodimen-t of a cassette 10, according to the invention which ~` is provided with supplementary expedients in order to increase its ergonomic properties. ~he casset-te 10 comprises a bottom ;!
11 (of which only the side edges may be seen) and a cover 12 '1 which are hingingly connected with each other. Suitable locking means 14 are provided. In contrast to the cassette ~t of fig. 1, the locking means are located in the side walls of -the cassette and may comprise a pin fixedly connected to . .
.
the cover 12 and a yieldi~gly biased slot which is located on a rail or in a groove fixedly connected with -the bottom 11 .
` wherein the pin and slot are capable of engaging each other ~; when exerting a pressure on the cover ~2. As this locking/
, , unlocking means is no part of the invention i-t has not been represented in detail. ~he cover 12 of which a part is formed by a flexible foil 16 is provided wi-th means which permit j .
-the film to be provided with supplementary data related to .. : , ,l GV.893 PC~ - 10 -'' :
z~
-the person or to -the objec-t to be radiographed.
So are provided first identification means 40,41,42 which enable to print additional informa-tion related -to -the person to be radiographed upon the film (not shown). ~he said identification means comprise a small chamber ~0 in which a slide 41 is located and which slide 41, by pushing -the knob 42 in downward direction, may perform a transla-tional movement into -the chamber 40, so providing a small rec-tangular opening in the cover ~2. At -tha-t moment data carrying means (not shown) such as a smal:L typewritten card may be placed into a special exposure unit (not shown) which,by means of a small light source, prints -the data upon the film via the above mentioned opening in the cover. ~he slide 41 may be resilien-tly biased in the chamber 40, so that upon withdrawing the casse-tte ~0 from the special exposure unit the slide 41 automatically closes again in a light-tight manner.
~here are also provided second identification means for printing supplementary data upon the film during its exposure to penetrating radiation.
. Especially in mammography in which generally two practi-cally identical objects are radiographed, it is desirable to dispose of identification upon the film which positively indicates whether it is the left or the right breast which is represented on the radiographic record.
As such, symbols 45 or 46 provided on a slide 4~ and associated with respectively the left or right side of the GV.893 PC~ - 11 _ - j Z~
pa-tien-t are flxedly loca-ted in the cover 12 of t~e cassette.
~he slide ~3 made of a material opaque to pene-trating radia-tion and having an opening 44 may -take a dual position in that the opening 44 may be positioned either over the symbol 45 or over the symbol 46.
The said symbols 45 and 46, which are made of a pene-trating radiation absorbing ma-terial, such as lead, intercep-~-the radiation during exposure, so -that after processing the film a white area in the form of the symbol is obtained there-on. ~he circles 50 and 51 represen-t -the areas on which cover lifting means (such as sucker cups) may be located for opening -the cassette when the latter is incorporated into or forms part of a daylight loading/unloading system.
~ inally, fig. 6 shows an alternative embodiment of -the cassette 10 of fig. 1, in which a second intensifying screen 29 is connected to the flexible foil 16 on the cover 12.
~his second intensifying screen 29 contributes positively to a substantial decrease of the radiation dose by the fact that the radiographic film 28, having in general a penetra-ting radiation sensitive coating on either side, will be exposed to the light emitted by both intensifying screens 17 and 29, which means that the radiation dose may practically be halved.
~he second intensifying screen 29 may be secured to the ; flexible foil 16 by known means such as pressure adhesive tape. If desired, the side of the flexible foil 16 facing the inner space of the cassette itself may be provided with ,7 a fluorescent coating, so that the use of a separate support ` GV.893 PC~ - 12 -.-.
ilLZ4 . ~
. for this coating may be dispensed wi-th.
,1 ~ ~ .
!, "
i: .
. 1 ,.
~!
;~ GV. 893 PC~ - 13 ~, , . ~ . . . ..
.
Claims (19)
1.A radiographic film cassette comprising a bottom and a cover connected by hinges to each other and fastening means, said bottom and said cover when closed and fastened form a light-tight enclosure in which a radiographic film sheet can be accommodated,the cover being formed in part by a flexible foil which is transparent to penetrating radiation and extends over part of the plan area of the cassette, and in part by a less flexible marginal portion to which said foil is connected and that has a thickness that is greater than that of the flexible foil, and comprising at least one exhaust opening via which air can be aspirated from the interior of the closed and fastened cassette to cause atmospheric pressure to be exerted on said screen/film system via said foil.
2. A radiographic cassette according to claim 1, in which the bottom beans a first intensifying screen.
3. A radiographic film cassette according to claim 1, in which said cover and said bottom at the surfaces facing each other are provided respectfully with a ridge-like and a groove-like structure engaging each other when the cassette is in closed condition.
4. A radiographic film cassette according to claim 3, in which the space defined by the edge of the cover and the ridge-like structure thereon contains a resilient, air-tight material.
5. A radiographic film cassette according to claim 4, in which said material is a silicone rubber.
6. A radiographic film cassette according to claim 1, in which the surface area of the cover of the cassette which is composed of a flexible foil has a rectangular form.
7. A radiographic film cassette according to claim 6, in which said flexible foil is a polymeric material.
8. A radiographic film cassette according to claim 7, in which said polymeric material is polyethylene containing carbon black.
9. A radiographic film cassette according to claim 1, wherein said foil occupies at least 60 % of the plan area of the cassette.
10. A radiographic film cassette according to claim 1, wherein said foil has a thickness of not more than 0.5 millimeter.
11. A radiographic film cassette according to claim 1, in which said cover is in U-shaped form and in which said flexible foil is folded near the hinges and continues onto said bottom and is located between said bottom and said intensifying screen.
12. A radiographic film cassette according to claim 3, in which said flexible foil has a width exceeding the width between the overlying parts of said ridge-like or groove-like structure.
13. A radiographic film cassette according to claim 1 which comprises in addition a second intensifying screen which contacts that side of said flexible foil which faces the interior of said cassette.
14. A radiographic film cassette according to claim 13, in which said second intensifying screen is in the form of a coating on said flexible foil.
15. A radiographic film cassette according to claim 13, in which said second intensifying screen is in the form of a coating on a separate support, which support is secured to said flexible foil.
16. A radiographic film cassette according to claim 1 which further comprises first identi-fication means in order to print additional information on the film contained in said cassette.
17. A radiographic film cassette according to claim 15, in which said first identification means comprise an opening of generally rectangular form in the cover which may be screened off from ambient light by means of a slide, and via which opening data from outside the cassette may be projected onto a radiographic film contained in the latter.
18. A radiographic film cassette according to claim 17 in which there are also provided second identification means in order to permit additional information to be printed on the film.
19. A radiographic film cassette according to claim 18, in which said second identification means comprise at least one significant symbol in penetrating radiation opaque material, said significant symbol being capable to be screened off from or to be put into the beam of penetrating radiation during exposure, so preventing or enabling the formation of a latent image in or on said radiographic film.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB25949/76A GB1578746A (en) | 1976-06-22 | 1976-06-22 | Radiographic film cassette |
| GB25.949/76 | 1976-06-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1086124A true CA1086124A (en) | 1980-09-23 |
Family
ID=10235948
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA280,431A Expired CA1086124A (en) | 1976-06-22 | 1977-06-13 | Radiographic film cassette with flexible foil cover |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS5392A (en) |
| BE (1) | BE855415A (en) |
| CA (1) | CA1086124A (en) |
| DE (1) | DE2727005C3 (en) |
| FR (1) | FR2356182A1 (en) |
| GB (1) | GB1578746A (en) |
| IT (1) | IT1079054B (en) |
| NL (1) | NL7706399A (en) |
| SE (1) | SE430928B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3208999C2 (en) * | 1982-03-12 | 1984-11-08 | Standard Elektrik Lorenz Ag, 7000 Stuttgart | Light-tight flat cassette |
| JPS59116738A (en) * | 1982-12-24 | 1984-07-05 | Hitachi Ltd | Film contacting device for x-ray fluorography |
| DE3401577C1 (en) * | 1984-01-18 | 1985-05-30 | Agfa-Gevaert Ag, 5090 Leverkusen | Roentgenblattfilmkassette for shooting angled body parts |
| JPS60169637U (en) * | 1984-04-20 | 1985-11-11 | コニカ株式会社 | X-ray film cassette |
| US5077778A (en) * | 1990-08-27 | 1991-12-31 | Fabian Carl E | Film cassette having marker for identifying the exposure side of a medical radiograph |
| FR2708755B1 (en) * | 1993-08-05 | 1995-09-08 | Kodak Pathe | Identification process in radiography and cassette for the implementation of this process. |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1288904B (en) * | 1965-04-26 | 1969-02-06 | Eastman Kodak Co | Evacuable X-ray film cassette |
| DE2214613C3 (en) * | 1972-03-25 | 1978-10-05 | Andreas 8420 Kelheim Schmitzer | Vacuum cassette for X-ray films |
-
1976
- 1976-06-22 GB GB25949/76A patent/GB1578746A/en not_active Expired
- 1976-09-20 FR FR7628410A patent/FR2356182A1/en active Granted
-
1977
- 1977-06-06 BE BE1008176A patent/BE855415A/en not_active IP Right Cessation
- 1977-06-10 NL NL7706399A patent/NL7706399A/en not_active Application Discontinuation
- 1977-06-13 CA CA280,431A patent/CA1086124A/en not_active Expired
- 1977-06-15 DE DE2727005A patent/DE2727005C3/en not_active Expired
- 1977-06-20 SE SE7707120A patent/SE430928B/en unknown
- 1977-06-21 JP JP7432377A patent/JPS5392A/en active Pending
- 1977-06-21 IT IT49903/77A patent/IT1079054B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| IT1079054B (en) | 1985-05-08 |
| DE2727005C3 (en) | 1982-05-13 |
| DE2727005A1 (en) | 1978-01-05 |
| NL7706399A (en) | 1977-11-30 |
| GB1578746A (en) | 1980-11-12 |
| BE855415A (en) | 1977-12-06 |
| FR2356182A1 (en) | 1978-01-20 |
| DE2727005B2 (en) | 1981-03-26 |
| SE430928B (en) | 1983-12-19 |
| SE7707120L (en) | 1977-12-23 |
| JPS5392A (en) | 1978-01-05 |
| FR2356182B1 (en) | 1978-12-22 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |