Abstract:
A storage phosphor cassette for use in recording radiographic images of elongated objects. The cassette includes: first and second storage phosphor plates having first and second length dimensions, a shell having first and second opposite open ends; a first assembly for detachably mounting said first storage phosphor plate in said shell from said first open end; and a second assembly for detachably mounting said second storage phosphor plate in said shell from said second open end, wherein said first and second storage phosphor plates are mounted in said shell such that they form a substantially continuous storage phosphor composite for recording an elongated radiographic image.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This non-Provisional application claims the benefit under 35 USC§120 of the earlier filing date of Provisional Application U.S. Ser. No. ______, filed on Dec. 8, 2000, titled: ELONGATED COMPUTED RADIOGRAPHY CASSETTE, inventors: David L. Steklenski, David H. Foos. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates in general to medical imaging and more particularly relates to the use in computed radiography (CR) of an elongated CR cassette for imaging elongated body regions, such as the full spine or the leg.  
         BACKGROUND OF THE INVENTION  
         [0003]    Conventional size radiographic image acquisition units are limited in size and unsuitable for imaging elongated body regions such as the full spine or the leg. The largest conventional radiographic film and radiographic computed radiography plates used in chest radiography are 35×43 cm. (14×17 in.). When it is necessary to obtain a radiographic image of a full spine or leg, several approaches have been used. If film/screen technology is used, either an extra long, non-standard radiographic film is used, or as disclosed in U.S. Pat. No. 3,774,045, issued Nov. 20, 1973, inventor Trott and U.S. Pat. No. 3,725,703, issued Apr. 3, 1973, inventor Bucky, cassette or cart is provided for holding a plurality of overlapping conventional sized film cassettes or packs. In the case of a special elongated film, the cost of the film and its processing is substantially greater than the cost of the conventional sized film. In the case of multiple film solutions, the films must be taped together to obtain the full length radiographic image. This introduces overlap and alignment problems.  
           [0004]    Similar solutions have been proposed when computed radiography plates are used. Thus, U.S. Pat. No. 5,130,541, issued Jul. 14, 1992, inventor Kawai discloses a self enclosed CR unit using elongated CR plates that are exposed, read, erased and reused within the unit. U.S. Pat. No. 5,111,045 discloses a self enclosed unit using conventional sized CR plates that are exposed, read, erased and reused within the unit. When an elongated body region is imaged, first and second overlapping CR plates are positioned at the exposure station, exposed and then processed. Both of these solutions are disadvantageous in the use of an expensive, heavy, self-enclosed unit that is unsuitable for use when a patient is unable to use the unit due to physical disability or when admitted to a hospital emergency room, intensive care unit or surgical suite.  
           [0005]    EP Patent application EPO 919856A1, published Feb. 6, 1999, inventor Dewaile et al. discloses an assembly for recording a radiographic image of an elongated body including a plurality of CR cassettes holding conventional sized CR plates that are held in staggered arrangement so that the length of the staggered arrangement is equal to at least the length of the elongated body. After exposure, the CR plates are read individually and the read electronic images are stitched together to form the entire image of the elongated body. This technique is disadvantageous in requiring the use of a special assembly to hold the CR cassettes. U.S. Pat. No. 5,986,279, issued Nov. 16, 1999, inventor Dewaile, discloses an elongated CR cassette holding a plurality of overlapping or non-overlapping CR screens. After exposure, the CR screens are removed from the elongated cassette, put into “normal” sized cassettes, and applied to a read out device that is able to read out normal sized cassettes. This technique is disadvantageous in the time and expense involved in loading and unloading the elongated cassette as well as in the subsequent handling of individual CR cassettes to enable CR screen readout.  
           [0006]    There is thus a need for a solution to these problems.  
         SUMMARY OF THE INVENTION  
         [0007]    According to the present invention, there is provided a solution to the problems of the prior art.  
           [0008]    According to a feature of the present invention, there is provided a storage phosphor cassette for use in recording radiographic images of elongated objects comprising: first and second storage phosphor plates having first and second length dimensions; a shell having first and second opposite open ends, a first assembly for detachably mounting said first storage phosphor plate in said shell from said first open end; and a second assembly for detachably mounting said second storage phosphor plate in said shell from said second open end, wherein said first and second storage phosphor plates are mounted in said shell such that they form a substantially continuous storage phosphor composite for recording an elongated radiographic image.  
         ADVANTAGEOUS EFFECT OF THE INVENTION  
         [0009]    The invention has the following advantages.  
           [0010]    1. Radiographic images of an elongated object can be made in a single exposure using conventional size CR plates.  
           [0011]    2. The CR plates are exposed to a radiographic image in the same plane, obviating the need for stacking multiple cassettes and performing complex corrections or multi-plane images.  
           [0012]    3. The CR plates are not handled manually and are read automatically thus minimizing degradation of the CR plate and resultant image degradation. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a diagrammatic view of a CR cassette according to the present invention.  
         [0014]    [0014]FIG. 2 is a diagrammatic view of a radiographic image system using the present invention.  
         [0015]    FIGS.  3 - 13  are views illustrating details of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    In general, the present invention relates to the radiographic imaging of an elongate object such as the full spine (for diagnosing scoliosis, for example) or leg of a human subject.  
         [0017]    Two contiguous CR plates contained in an elongated cassette are exposed to a radiographic image of an elongate object to produce a latent image stored in the CR plates. The CR plates are removably mounted in the cassette and are sequentially fed to a CR reader where the latent radiographic images are converted to two electronic images which are combined to form an elongated image. The elongate image can be displayed on an electronic display or printed out on hard copy media.  
         [0018]    Referring now to FIGS. 1 and 2, there is shown an embodiment of the present invention. As shown, storage phosphor cassette  10  includes an elongate rectangular shell  12  having first and second open ends  14  and  16 . A first storage phosphor plate assembly  18  is detachably mounted in shell  12  from the first open end  14 . A second storage phosphor plate assembly  20  is detachably mounted on shell  12  from the second open end  16 . Each assembly  18 ,  20  includes a storage phosphor plate  22 ,  24  and a support and latching assembly  26 ,  28 . Plates  22 ,  24  are butt joined or overlapped in the central region  29  of shell  12 . Shell  12  includes upper and lower members  30 ,  32  and side extrusions  34 ,  36  which together form a rectangular shell.  
         [0019]    [0019]FIG. 3 shows first storage phosphor assembly  18  partially detached from cassette  10  at a reading device (not shown).  
         [0020]    [0020]FIG. 4 shows a cross-section of cassette  10  showing upper and lower members  30 ,  32  having respective opposed inner surfaces  40 ,  42  including deflectors  44 ,  46  extending therefrom for guiding the inner ends of assemblies  18 ,  20  to overlap. This results in an overlapping of storage phosphor plates  22  and  24  to form a composite storage phosphor plate for elongate radiographic images, such as the human spine and leg.  
         [0021]    [0021]FIG. 5 shows a radiographic imaging system using the elongated storage phosphor cassette of the present invention. As shown, cassette  10  is mounted on support  50 . Patient  52  is positioned between cassette  10  and a source  54  of X-rays. An X-ray beam  56  from source  54  penetrates the torso region  58  of patient  52  to record a latent radiographic image thereof in the composite storage phosphor plates of cassette  10 . The cassette  10  is removed and the first storage phosphor assembly placed in a reading device (described later). The first plate is read and the first electronic image stored. The cassette is removed from the reading device, inverted and the second storage phosphor assembly is placed in the reading device. The second storage phosphor plate is read and the second electronic image is stored. The two images can then be processed into a single image if so desired.  
         [0022]    [0022]FIGS. 6, 7 and  8  show in greater detail the components of storage phosphor cassette  10 . As shown, cassette  10  is viewed from one end showing first storage phosphor assembly  18 . It will be understood that the other end of cassette  10  is similar in structure but showing storage phosphor assembly  20 . Storage phosphor plate assembly  18  has a storage phosphor plate  22  including an aluminum support plate  60  carrying a storage phosphor screen  62 . Plate  22  is cantilevered from assembly  26  which has a plurality of openings  64  and an opening  68  to be explained later (FIG. 8). Shell  12  has a lower member  32  having notches  66  with set back portions  70  at each open end  14 ,  16 . A locking mechanism in assembly  26  locks storage phosphor plate assembly  18  into shell  12 .  
         [0023]    Referring now to FIGS.  9 - 13 , there is shown a reader device for reading a storage phosphor plate assembly. As shown, storage phosphor reading device  100  includes a cassette receiving station  102  for receiving a cassette  103  containing a storage phosphor plate that stores a latent radiographic image. Station  102  has clamps  104 ,  106  for clamping the end of cassette  103 . Extractor bar assembly  108  includes hooks  110  for removing and replacing a storage phosphor assembly relative to cassette  103 . Assembly  108  is mounted on stage  112  for movement in opposite directions  114 . Stage  112  is mounted for movement in opposite directions  116  on rails  118 ,  120  on support  122 .  
         [0024]    As shown in FIGS. 10 and 11, the lower member  130  of cassette  103  has cut-outs  132  with slots  134 . The support and latch assembly  136  of the storage phosphor plate assembly contained in cassette  103  has a front wall  138  with openings  140  through which hooks  11 O project. Assembly  136  has a latch  142  with cutouts  144  and angled tabs  146 . In FIG. 10, the storage phosphor plate assembly is locked in cassette  103  by the mating of tabs  146  of latch  142  with slots  134  of cutouts  132 . In FIG. 11, hooks  110  with bearing portion  110   a  of extractor bar assembly  108  have been moved to the left to unlatch latch  142  from lower member  130  of cassette  103 . Hooks  110  grab front wall  138  of the storage phosphor plate assembly to allow removal of the assembly from cassette  103 .  
         [0025]    As shown in FIG. 12, extractor bar assembly  108  has engaged storage phosphor plate assembly  150  of cassette  103  and unlatched assembly  150  from cassette shell  152  of cassette  103 . In FIG. 13, extractor bar assembly  108  has completely removed storage phosphor plate assembly  150  from shell  152  of cassette  103 . Assembly  108  and assembly  150  are then moved in the direction  116  so that a laser scanner (not shown) reads the latent radiographic image stored in the storage phosphor screen  154  of storage phosphor plate assembly  150 . U.S. Pat. No. 5,276,333, issued Jan. 4, 1994, inventor Robertson, discloses an exemplary X-ray cassette having a single removable storage phosphor assembly. U.S. Pat. No. 5,330,309, issued Jul. 19, 1994, inventors Brahm et al., discloses an exemplary reader having cassette locating and unlatching mechanism.  
         [0026]    It will be understood that the present invention includes other types of elongated cassettes having removable storage phosphor plate assemblies. Thus, this cassette shell could have a three-sided, U shaped with an open bottom in which the storage phosphor plate assemblies close off the open bottom. Other type of latching mechanisms can also be used.  
         [0027]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.  
                                             PARTS LIST                                     10   storage phosphor cassette            12   elongated rectangular shell            14   first open end            16   second open end            18   first phosphor plate assembly            20   second phosphor plate assembly            22, 24   storage phosphor plate            26, 28   latching assembly            29   central region            30, 32   upper and lower members            34, 36   side extrusions            40, 42   inner surfaces            44, 46   deflectors            50   support            52   patient            54   source            56   X-ray beam            58   torso region            60   aluminum support plate            62   storage phosphor assembly            64   openings            66   notches            68   opening            70   back portions           100   storage phosphor reading device           102   cassette receiving station           103   cassette           104, 106   clamps           108   assembly           110, 110a   hooks           112   stage           114   opposite direction           116   opposite direction           118, 120   rails           122   support           130   lower member           132   cutouts           134   slots           136   assembly           138   front wall           140   openings           142   unlatch latch           144   cutouts           146   angled tabs           150   plate assembly           152   cassette shell