Abstract:
Cassette device for producing images, for a radiography apparatus of the type comprising a means for receiving mobile cassettes. The cassette comprises a casing of substantially parallelepipedal shape surrounding a means for producing images. The device comprises a means which forms a handle and is arranged on a small face of the casing The means which forms a handle is provided with a stop surface for insertion of the cassette into the reception means of the radiography apparatus.

Description:
This is a continuation application of International application Ser. No. PCT/FR97/02145 filed Nov. 28, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a cassette device for producing digital images, for a radiography apparatus. In general, such radiography apparatuses comprise an X-ray emitter, a device for supporting the cassette for producing images, the organ to be radiographer being arranged between the X-ray emitter and the cassette support device, a means for processing the data thus obtained and a space for storing the cassette when it is not being used. 
     By way of example, there are known mammography apparatuses which comprise an X-ray source arranged on one side of the organ to be radiographer, a support table, transparent to X-rays, arranged on the other side of the organ to be radiographer, an adjustable holding plate which presses the organ onto the support table, and a housing for receiving a cassette for producing images containing an exposable film. The housing is arranged under the support table and constitutes a means for receiving the cassette. After an image of the organ has been taken, the cassette containing the exposed film is extracted from its housing, and the film is developed. 
     Such apparatuses are generally used for finding possible symptoms of breast cancer. With the aim of reducing the time for which the patient is immobilized, the cassette containing exposable films may be replaced by cassettes containing a means for producing digital images, capable of producing images extremely quickly. The image production operations, in particular during a biopsy, are thus much shorter and reduce the discomfort of these examinations. Furthermore, cassettes for producing digital images allow the quality of the diagnosis to be improved. For economic reasons, it is desirable to use cassettes for producing digital images without changing the rest of the radiology apparatus. The cassette should be removable, so that it can be arranged either under the table, during diagnosis, or in the puncture system, during a biopsy. 
     A cassette for producing digital images comprises a casing, within which a device for detecting the radiographic signal is arranged. This detection device may, for example, comprise a scintillator capable of converting the incident X-rays into light radiation, an optical fiber making it possible to filter most of the X-radiation which has passed through the scintillator, and protecting the components located downstream of said optical fiber, and a charge-coup]Led device (CCD) array camera forming a sensitive region. In order to ensure that the cassette is positioned appropriately in the housing, the cassette is generally provided with a locking means. The cassette is also provided with an electrical cable connecting it to a data processing means, In general a microcomputer. 
     A mammography apparatus is generally provided with a support table whose height can be adjusted, and an X-ray source which can be tilted through ±180° relative to the vertical plane of symmetry of the apparatus. The support table may be replaced by a puncture system, intended for biopsy and also provided with a reception means. The puncture system comprises a holding plate which acts as a compression pad, a needle holder and a needle capable of performing a biopsy in the organ to be radiographer. 
     The data processing means may be connected to the puncture system and to the cassette by electrical cables, in particular in order to process the data received from the cassette and to control the puncture system, in particular the movement of the needle holder during biopsy. The data processing means can also control the X-ray source and comprises a screen for displaying the images of the radiographer organ and a keyboard. The data processing means may be equipped with software intended for the calculations of the three-dimensional coordinates of points in the organ to be radiographer on the basis of two images produced at different angles by virtue of the pivoting of the X-ray source. It is thus possible to obtain excellent visualization either of particular regions in the radiographer organ during diagnosis, or of the positioning of the needle in the radiographer organ during a biopsy, by using optimized display methods. 
     During operation, the X-rays are emitted by the source, passed through the holding plate, the radiographed organ, the breast support: plate and the upper wall of the sensitive region of the cassette, and enter the scintillator which, on receiving X-rays, emits visible light which is forwarded to the array camera by the fiber-optic layer. The array camera makes it possible to convert the information received in the form of visible light into information in the form of a digital electrical signal, which is transmitted to the data processing means. 
     Conventional digital cassettes are expensive and are not very easy to handle because of their flat shape and their attachment to an electrical cable connected to the data processing means. Twisting the cable close to the cassette, or sudden pulling risks causing significant damage inside said cassette. The risk of dropping should also be avoided. Furthermore, precise and secure positioning of the cassette in a housing is not obtained with conventional cassettes because of the presence of the cable. However, precise positioning is important for the quality of the images obtained, to avoid blurring, and for the accuracy of the positioning calculations for the biopsy examinations. 
     The object of the present invention is therefore a cassette device for producing images which overcomes the above drawbacks, which is easy to grip, whose positioning is precise and whose cable outlet is protected. 
     The cassette device for producing images according to the invention is intended for a radiography apparatus of the type comprising a means for receiving mobile cassettes. The cassette comprises a casing of substantially parallelepipedal shape surrounding a means for producing images. The device comprises a means which forms a handle and is arranged on a small face of the casing, said means forming a handle being provided with a stop surface for insertion of the cassette into the reception means of the radiography apparatus. The means which forms a handle may comprise a surface for supporting the arm of a patient being radiographed, and a cable outlet. The risk of the cassette slipping from the hands of an operator is thus greatly reduced. Possible twisting of the cable close to the cassette, or pulling will not have detrimental effects inside the casing, since the corresponding forces are taken up by the means which forms a handle. There is no longer any risk of the patient&#39;s arm being in direct contact with the cable. 
     BRIEF SUMMARY OF THE INVENTION 
     In one embodiment of the invention, the insertion stop surface is vertical, when the cassette is arranged in the reception means of the radiography apparatus, and is in contact with a corresponding surface of said radiography apparatus, said means forming a handle being arranged on a face of the casing which is to the rear in the cassette insertion direction. Since the means which forms a handle remains protruding from the reception means, it is very easy to insert the cassette into the reception means by pushing on the means which forms a handle. 
     In one embodiment of the invention, the support surface is substantially horizontal 
     Advantageously, the cable outlet comprises a conduit provided with a first orifice, arranged on a lower face of the handle, and a second orifice opening into the casing of the cassette. The cable thus exits under the means which forms a handle and does not risk interfering with the arm of a patient. 
     In one embodiment of the invention, the device comprises a locking means which can be locked after the cassette has been inserted into the reception means of the radiography apparatus. This avoids possible pulling of the cassette from the reception means, in particular due to tension on the cable or by falling under gravity. 
     Preferably, the locking means is arranged on the casing and can protrude from the reception means after insertion. The locking means may be rotary. 
     Preferably, the locking means comprises a spring acting axially in the direction of the casing. This keeps the cassette prestressed at the bottom of the reception means. 
     The locking means may interact with the reception means so that it executes a translation simultaneously with a rotation. The means which forms a handle may comprise a removable stop. 
     By virtue of the invention, the patient can rest his arm on the handle without any risk of moving the cassette or interfering with the cable. The invention will be understood more clearly on studying the detailed description of an embodiment, taken by way of entirely non-limiting example and illustrated by the appended drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the device according to an embodiment of the invention; 
     FIG. 2 is a front elevation of the cassette device; 
     FIG. 3 is a top elevation of the cassette device; 
     FIG. 4 is a side elevation of the cassette device; 
     FIG. 5 is a cross-sectional view of a variant of a cassette device in its reception means; and 
     FIG. 6 is a similar view to FIG. 5, the cassette device being out of the reception means. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As can be seen in the figures, the cassette  1  comprises a substantially parallelepipedal casing  2  comprising an upper face  3 , a lower face  4 , two longitudinal edges  5  and  6  and two side edges  7  and  8 . Two truncated comers  9  and  10  are respectively formed at the intersections between the longitudinal edge  5  and the side edge  7 , and between the longitudinal edge  5  and the side edge  8 , both truncated comers being perpendicular to the upper  3  and lower  4  faces. 
     On the side edge  7  of the casing  2  of the cassette  1 , a handle  11  is arranged which is used both for the operator to grip the cassette  1 , to protect the electrical cable  12  at its outlet from the cassette  1  and, where appropriate, to support the patient&#39;s arm in order to improve comfort. By virtue of the handle  11 , movement of the cable  12  relative to the casing  2  does not cause damage to the electrical contacts of the end of the cable  12  inside the casing  2 . patient during the examination. In order to provide a good grip, the height of the handle  11  is very much greater than the height of the casing  2 . The handle  11  comprises a substantially plane upper face  13  which provides the patient with the possibility of resting his arm on it when the mammography apparatus is horizontal. The handle  11  also comprises a side face  11   a  on the opposite side from the casing  2 , which is used to support the patient&#39;s arm when the mammography apparatus is inclined by 90°, the side face  11   a  then being horizontal. Opposite the upper face  13 , the handle  11  comprises a lower face  14  which is provided with an outlet orifice  15  for the cable  12 . The handle  11  also comprises an orifice  16  which communicates with the interior of the casing  2  and through which the cable  12  passes. Thus, if the cable  12  is pulled or twisted, the handle  11  will stabilize the cable  12  and prevent any movement of it inside the casing  2 . A cable  12  with flattened cross section may be provided in order to increase its rigidity along one axis, so as to direct it in a direction away from the patient, for example at 45° relative to the vertical. 
     On the side edge  8  opposite the side edge  7 , the cassette  1  comprises a lock  17  for immobilizing the cassette  1  in its housing which ire provided with a breast support plate, in a positioning system or in a storage space. The lock  17  is mounted so that it can rotate about a horizontal axis parallel to the longitudinal edges  5  and  6 . In FIGS. 1 to  4 , the lock  17  is represented in the inactive or unlocked position. It can be seen that the thickness of the lock  17  is less than or equal to that of the casing  2 , in order to make it possible to insert the cassette  1  into a housing, in the direction of the arrow represented in FIG. 1, with the lock  17  entering the housing first. 
     The lock  17  may comprise a locking sensor and an analogue/digital converter (which are not shown), which send a digital signal to the data processing means when the lock  17  is locked, which may make it possible, for example, to prevent a frame from being taken so long as the cassette  1  is not locked suitably in the housing of a positioning system or breast support plate. This avoids unproductive emission of X-rays. 
     In FIG. 5, the cassette  1  is arranged in the housing of a reception means  18 . The reception means  18  comprises a first side face  19 , provided with an orifice  20  for entering the housing, and a second side face  21 , provided with an orifice  22  for exiting the housing. The handle  11 , adjacent to the side edge  7  of the casing  2 , is provided with a stop  23  which protrudes from the side of the casing  2  and comes into contact with a corresponding surface  24  of the first side face  19  of the reception means  18 . The stop  23  is removable so that its thickness can be selected according to the dimensions of the reception means. 
     The lock  17 , which is mounted so as to rotate, can also move in translation relative to the casing  2 . The lock  17  is retained axially by a spring (not shown) which is arranged inside the casing  2  and which exerts on said lock  17  a force which tends to return it toward the casing  2 . On one side, the lock  17  comprises a rounded locking surface  25  which can enter into contact with a corresponding surface  26  of the side face  21  of the reception means  18 . On the opposite side from the locking surface  25 , the lock  17  comprises a notch  27  which is intended to prevent any contact between said lock  17  and the reception means  18 . 
     A cassette  1  is inserted into the housing of a reception means  18  as follows. The cassette  1  is taken by the handle  11 , while firstly presenting the lock  17  in the unlocked position facing the orifice  20  of the first side face  19  of the reception means  18 . The cassette  1  is inserted into the housing of the reception means  18  until the stop  23  of the handle  11  is in contact with the corresponding surface  24  of the first side face  19 . At this stage, the lock is in the position illustrated by FIG.  6  and protrudes from the orifice  22  of the the position illustrated by FIG.  6  and protrudes from the orifice  22  of the second side face  21 . The lock  17  is then turned through about 90°, which leads to contact between the rounded locking surface  25  and the corresponding surface  26  of the second side face  21 , then sliding of the surface  25  on the surface  26 . The rounded surface  25  then acts as a ramp and causes a translational movement of the lock  17  outwards, simultaneously with its :rotation. At the end of rotation, the lock  17  is in the locked position illustrated in FIG. 5, and the cassette  1  is prestressed against the first side face  19  of the reception means  18  by virtue of the spring of the lock  17 . In order to ensure that the cassette  1  is held firmly, provision is made for a prestress force of the order of 10 to 70 N. 
     By virtue of this possibility of the lock  17  moving in translation relative to the casing  2 , and by virtue of the selection of the thickness of the stop  23 , the cassette  1  can be used with different radiography apparatuses which have cassette housings whose dimensions are not exactly identical, while ensuring that the X-radiation is targeted properly so as to irradiate only those regions of the organ whose image is acquired by the cassette. This makes the cassette easier to use. The locking means also prevents the cassette from falling from its housing, for example as a result of inclining the X-ray source and the reception means in order to perform certain examinations. 
     The rounded shape of the locking surface  25  of the lock  17  allows the operator to move the lock  17  in translation during the rotation, without having to pull on the lock  17 . This rounded shape Also tends to press the cassette  1  downward against the walls of its housing, which further improves the precision in the positioning of the cassette  1  relative to said housing. 
     The disclosed embodiments of the invention provides a cassette for producing digital images which is easy to grip, operates more reliably and is very durable. The mechanical positioning of the cassette ensures that the images are precise and that there is no blurring due to undesired movements of the cassette. 
     Various modifications in structure and/or steps and/or function may be made by one skilled in the art to the disclosed embodiments without departing from the scope and extent of the invention.