Abstract:
The invention relates to a method for processing a photostimulatable image plate ( 8 ). The image plate ( 8 ) is taken out of a cassette ( 1, 40 ), processed and placed back in the same cassette ( 1, 40 ), the cassette being conveyed from an input station ( 20 ) to an output station ( 22 ). The cassette ( 1, 40 ) is rotated about a vertical axis during conveyance once the image plate is taken out of the cassette and before said plate is reinserted in the same cassette.

Description:
BACKGROUND OF THE INVENTION 
     The present invention concerns a method and device for processing photostimulable image plate as whereby an image plate is taken out of a cassette, processed and then placed back in the same cassette while the cassette is transported from an input station to an output station 
     Photostimulable phosphor-coated film is increasingly employed instead of conventional film to produce x-rays for medical diagnoses. One advantage of a phosphor-coated film as a graphic reference material is its almost linear reproduction characteristic. This means that the gray scale or scale of densities of the image carrier matches the dose of radiation beamed onto it. Images obtained with photostimulable image plates are accordingly much less sensitive to excess or insufficient radiation. Another advantage of photostimulable image plates or phosphor-coated film is that they can be used over and over. Once the plate or film has been developed and the image interpreted and stored electronically, it can be erased and re-exposed. 
     Still another advantage of a phosphor-coated film is that it can be handled extensively like conventional x-ray film, and much existing processing equipment (e.g. cassettes, film loading-and-unloading mechanisms, etc.) can be used. 
     A method of and a device for handling photostimulatable phosphor-coated film is known, for example, from the European Patent No. 307,760 B1. The film is loaded into a cassette, such identifying information as patient&#39;s name and date of birth, physician&#39;s name, etc. is entered in a semiconductor memory on the cassette, and the film is exposed, leaving a latent image. To develop the image, the cassette is inserted into a digital reader, wherein it is opened and the film extracted and swept with radiation to stimulate it. The light emitted by the film is collected by a light collector and converted into a grid of pixels, restoring the image. The pixels can also be transmitted to a digital image processor for further treatment handling as desired. 
     There is a drawback to this approach. The footprint of the equipment employed to read out the film is relatively large in that the film is inserted into it from one direction, extracted from the cassette therein, and extracted in essentially the same direction for photoelectric scanning. Because of the many items of electronic equipment employed in hospitals, floor space in hospitals is at a premium. 
     Devices for processing photostimulable phosphor-coated film that occupy less area are known from the German Patent No. 3,733,191 C2 and the U.S. Pat. No. 5,493,128. In these devices the cassettes are forwarded vertically during processing. They are inserted into the device in one direction, displaced thereto, unloaded, and ejected in another direction. The cassettes, finished or in process, are coordinated in specific positions, especially in accordance with the U.S. Pat. No. 5,493,128, in relative complicated sorting mechanisms. 
     SUMMARY OF THE INVENTION 
     The principal object of the present invention is, accordingly, a method of and a device for processing photostimulable phosphor-coated image plates or film that will be as simple as possible and that will occupy as little area as possible. 
     This object, as well as other objects which will become apparent from the discussion that follows, are achieved, in accordance with the present invention, by a method whereby the cassette is rotated about a vertical axis after the image plate is extracted from it and before the image plate is returned to it. The invention also provides a device having an extraction station with an extraction mechanism for extracting the image plate from the cassette and thereafter returning the image plate to it. This extraction station rotates about a vertical axis after the plate is extracted from the cassette and before the plate is returned thereto. 
     In accordance with the present invention, the loaded cassette is rotated around a vertical axis while being forwarded. The cassette is opened in one position and the plate or film extracted and transported to the photoelectric scanner. While the plate or film is being scanned, the cassette, advantageously still open, is rotated farther to accept the scanned plate or film. The cassette is forwarded in a horizontal position in this embodiment. In another advantageous embodiment, however, the cassette can be forwarded essentially upright, resting on edge and tilted less than 45° to the vertical. This approach saves a lot of space inside the processor. A processor in accordance with this embodiment can also handle two cassettes at once, one ready to be unloaded and the other to be loaded. Such a device can process considerably more plates or film at a time than can be processed at the state of the art. 
     In one advantageous embodiment of the present invention, the cassette is forwarded to the film-extraction location in one direction horizontally and opened, and the plate or film extracted from it. The cassette is then rotated 180° around a vertical axis into a film-insertion position, where the photoelectrically scanned plate or film is returned to the cassette and the cassette closed. The cassette is then finally forwarded in opposition to the original direction to the delivery location, where it can be picked up at any time. 
     Both the cassette-insertion location (input station) and the cassette-delivery location (output station) can constitute temporary-storage locations, each accommodating several cassettes. The insertion end of the device can accordingly be continuously exploited and the cassettes picked up at the other end as time permits without impeding the operation of the device as a whole. 
     One particular advantage is that the whole device can be operated from one side, both of the directions traveled by the cassettes paralleling the controls. 
     Several locations can be included at both ends, where the cassettes can be sorted as they are inserted and ejected. 
     For a full understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention as illustrated in the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 schematically illustrates a state-of-the-art device for processing photostimulable phosphor-coated plates or film. 
     FIG. 2 illustrates one embodiment of a device in accordance with the present invention for processing photostimulable phosphor-coated plates or film. 
     FIG. 3 is a section through the device illustrated in FIG.  2 . 
     FIG. 4 shows details of a film-extraction location  35  inside the device illustrated in FIG.  2 . 
     FIG. 5 illustrates another embodiment of the device in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the present invention will now be described with reference to FIGS. 1-5 of the drawings. Identical elements in the various figures are designated with the same reference numerals. 
     FIG. 1 shows the essential components of a device of the type disclosed in the aforesaid references for processing photostimulable image plates or film. 
     The term “film”, as used hereinafter, shall mean and include any type of photostimulatable image plate. Many of the same components are also employed in the device in accordance with the present invention. An x-ray cassette  1  is loaded with a photostimulable image plate, especially phosphor-coated film. Cassette  1  is introduced into an identification station  2 , where such relevant information as patient name, body region imaged, name of attending physician, etc. is entered into a semiconductor memory from an input console. The same information can alternatively be entered directly from an electromagnetic card. Specific film-processing instructions can also be entered from a menu. Once the cassette has been provided with the relevant information, the film is exposed to an x-ray tube  3 . The film will now carry a latent image. The film,  8 , is now read by introducing cassette  1  into a processor  4 , where an unillustrated mechanism opens it and extracts the film. 
     A film transport  9  in the form of a belt now transports film  8  to a reading location  18  accommodating a reader  19  that comprises such optical, mechanical, and electronic components as a laser  5 , a lens  7 , a pivoting or rotating-polyhedral mirror  6 , a photomultiplier  11 , and light conductors  10 . Laser  5  emits a beam  25  capable of stimulating film  8 . The beam can be infrared, red, or green, depending on the type of film being processed. Lens  7  focuses the beam on film  8 . Mirror  6  directs the beam location by location and line by line onto film  8  in direction B. 
     Light is now emitted from the latent image on film  8 . Light conductors  10  collect the light and convey it to photomultiplier  11 , which amplifies the signal. The signal is now digitalized and transmitted to a computer  13  with a graphic memory. The signal can now be processed in a known manner, passed through filters, an anti-alias filter for instance, and/or be electronically compressed. While being read, film  8  is transported by film transport  9  in slow-scan direction A. 
     Once film  8  has been scanned, it is erased by an eraser  12  and returned to cassette  1 , ready for the next exposure. 
     In computer  13 , the digitalized image can be stored in a digital memory  15 , displayed for interpretation on a screen  14 , or transmitted by way of a digital interface  13   a  to hard-copy equipment  16  for transfer to photographic film  17 . The data can also be transmitted to other imaging systems through digital interface  13   a.    
     FIG. 2 illustrates one embodiment of a processor  4  for processing photostimulable phosphor-coated film. It includes an input station or cassette-insertion location  20 , a film-extraction location  35 , and an output station or cassette-delivery location  22 . Cassette-insertion location  20  and cassette-delivery location  22  constitute temporary-storage locations, accommodating up to twenty cassettes  1 . Cassettes  1  have a flat bottom, a cover hinged thereto, and several sides. Resting on one side, they are maintained essentially upright at locations  20  and  22 , leaning at an angle of no more than 20° and preferably of only 1° to a vertical axis  36 . Cassette-insertion location  20  and cassette-delivery location  22  are essentially mutually symmetrical with respect to a plane that parallels insertion direction I. Both locations are hinged to the housing  44  of processor  4 , cassette-insertion location  20  around an axis  42  that coincides with one lateral edge of the processor and cassette-delivery location  22  around a similar axis  43  that coincides with the opposite edge of the processor. This structure allows access to the inside of the device for maintenance and repair, and any film jammed inside it can easily be removed. 
     A mechanism forwards the cassette  1  resting against the wall  34  of cassette-insertion location  20  to the film-extraction location  35  inside processor  4  in direction I. Cover la swings out, opening the cassette, e.g. cassette  40 , inside the processor, and an extraction mechanism  38  extracts the film. The film is now transported to a reading location  18 , where it is scanned at high precision along slow-scan direction A, detecting any graphical data stored on the film. Once the data has been scanned, it is entirely erased from the film by a lamp  26 . The film is then transported back to cassette  40  in the opposite direction and loaded back into it at a location opposite the cassette-delivery side of film-extraction location  35 . Film-extraction location  35 , which can rotate up to 360° in a circle  37  around vertical axis  36  in direction H, rotates 180° to allow the film to be loaded. Film-extraction location  35  is, like cassette-insertion location  20  and cassette-delivery location  22 , symmetrical, essentially with respect to the same plane, and accordingly has two sides  32  and  33 . A cassette can be inserted into each side and both processed simultaneously. One cassette can also be unloaded while another, e.g. cassette  41 , is being loaded. This considerably accelerates the processor&#39;s overall sequence of operations. Still another advantage is that cassettes of different formats can be handled by the same device. Various such formats as accommodated in side  32  of film-extraction location  35  are indicated by the discontinuous lines. 
     A cassette is reloaded at the output side of film-extraction location  35  by a loading mechanism  39 . Due to the overall symmetry of the device, the components of loading mechanism  39  can be extensively similar to those of film-extraction mechanism  38 . Such a processor is very simple. 
     Once cassette  41  has been reloaded, it is forwarded to cassette-delivery location  22  in direction K. The cassettes are ejected in sequence and maintained ready at cassette-delivery location  22 . The holding capacities of cassette-insertion location  20  and cassette-delivery location  22  allow extensive automatization and hence full exploitation of the device without waiting. 
     FIG. 3 is a section along the line V-V through the device illustrated in FIG. 2 showing the essential components of cassette-insertion location  20  and cassette-delivery location  22  along with the schematically represented essentially upright cassettes  1  temporarily accommodated therein. Vertical axis  36  divides the overall device into essentially symmetrically disposed halves, specifically an insertion-end half  47  and a delivery-end half  46 . A light conductor  10  and a set  45  of film-transport rollers are represented in reading location  18 . The relatively acute angle α between the cassettes and vertical axis  36  is approximately 10°. 
     FIG. 4 illustrates details of film-extraction mechanism  38 . It is mounted on housing  58  and accordingly physically separated, as schematically indicated by line  54 , from film-extraction location  35 , which rotates inside the housing, although operating in conjunction with it. Mechanism  38  is provided with means  49  of suction that extract film  8  from an open cassette  40 , whereof the outward-pivoted cover  48  is schematically represented. Means  49  of suction communicate with mechanical controls by way of a lever  50  secured to wheels  59  and  60  that rotate on shafts  51  and  52 . Wheels  59  and  60  are driven by a single motor with appropriate output mechanisms by way of a transmission  53 . Means  49  of suction assume a position  49   b  while transporting film  8  to a baffle  61  and to set  45  of film-transport rollers and another position  49   a  while it is being transported from cassette  40  to set  45  of film transport rollers. As means  49  of suction travel from film-extraction location  35  to position  49   b , film  8  is rotated approximately 120° around a horizontal axis  62  perpendicular to the plane of projection by transmission  53  and wheels  59  and  60 . 
     Loading mechanism  39  essentially operates exactly like film-extraction mechanism  38  but is geometrically the mirror image of it. Some details of the mechanisms, of transmission  53  and its associated drive mechanisms for instance, may need to be altered for the film-insertion phase. The transmission could be S-shaped for example. 
     Various embodiments of the present invention have been hereintofore specified by way of example and without limiting its scope in any way, and alternative versions will occur to those of skill in the art. One such is illustrated in FIG.  5 . In this embodiment illustrates how a rotating film-extraction location can simultaneously be exploited as a cassette-sorting location. Cassette-delivery location  22  has been supplemented by as many auxiliary cassette-delivery locations  56  and  57  as desired, constituting a delivery-end sorting mechanism  55 . Appropriate controls, subject for example to the semiconductor memories mounted on the cassette, will assign each cassette to an appropriate compartment  56  or  57 , in accordance for instance with the particular hospital department (internal medicine, emergency room, etc.) it is intended for. 
     It is also possible to employ only one auxiliary cassette-delivery location opposite the original, resulting in a lower-capacity sorter that will also help to decrease waiting time. In this event, the cassette can be forwarded to a format-appropriate delivery location without further rotation of the extraction location. 
     There has thus been shown and described a novel method and device for processing photostimulatable image plate which fulfills all the objects and advantages sought therefor. Many changes, modifications, variations and other uses and applications of the subject invention will, however, become apparent to those skilled in the art after considering this specification and the accompanying drawings which disclose the preferred embodiments thereof. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention, which is to be limited only by the claims which follow.