Abstract:
A radiation exposure recording device and radiography method are disclosed, where the radiation exposure recording device includes a radiation exposure recording medium, a housing that at least partly surrounds the radiation exposure recording medium, and a first detector that detects a radiation exposure. An output signal produced in response to the detecting of the radiation exposure can be provided, and the detection of and output of a signal in response to the radiation exposure is entirely automatic and independent of any manual processing of the radiation exposure recording device. Further, the radiography method includes providing a first radiation exposure recording medium, providing a first radiation exposure detector, and sensing an exposure of radiation at the first radiation exposure detector. Also disclosed is a circuit that can be retrofitted to existing radiography cassettes for detecting when the cassettes are exposed to radiation.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   This invention was made with United States Government support awarded by the following agencies: ARMY/MRMC DAMD17-02-1-0517. The United States Government has certain rights in this invention. 

   CROSS-REFERENCE TO RELATED APPLICATIONS 
   BACKGROUND OF THE INVENTION 
   The present invention relates to x-ray radiography and, in particular, to the using of radiography plates to record x-ray information. 
   X-ray radiographs are of great value in diagnosing patient illnesses and monitoring patient status. A variety of x-ray radiographic techniques are now available including, for example, computed tomography (CT) and more conventional x-ray techniques. Radiographs or “radiographic pictures” are commonly taken by way of radiography plates that temporarily or, in some circumstances, permanently record radiographic information. Such radiography plates commonly come in two forms. A first form employs a version of photographic film, which typically is a sheet of translucent supporting material that is coated on one or both of its sides by a photosensitive emulsion. When exposed to photons at the wavelengths of interest, the photosensitive emulsion darkens the film at various locations according to the amounts of exposure that have occurred at any given location. 
   A second form of radiography plate employs a photo-stimulable phosphor plate. When exposed to x-ray photons from a radiography machine, energy is stored in the sheet at different positions according to the intensity of the radiation exposure at those positions, and thus the sheet stores an image. Then, some time later after the exposure to the high energy radiation, the sheet is “read” by a machine that scans the sheet with a small area beam (e.g., a laser beam) of relatively long-wavelength radiation to release the energy stored in the sheet as light. An appropriate photosensor receives light that is emitted by the sheet and produces electrical signals in accordance with the light received. The electrical energy in turn can be digitized to store the image information for computer access, or to output that image information on a display device or the like. 
   In each of these cases, although the radiography plates are intended for sensing x-ray photons such as those produced by radiography machines, the plates nevertheless are also sensitive to other light, in that the light would serve to erase the previously stored information. Consequently, to prevent the exposure of the radiography plates to visible light until such time as the radiographic information on those plates can be processed and recorded on a less ephemeral form, the plates typically are housed within boxes or “cassettes” that are impervious to visible light despite allowing for the passage of the high energy radiation produced by the radiographic imaging machines. When a radiograph exposure is taken, the cassette is removed for processing of the plate in the cassette. In the case of traditional photographic film-type radiography plates, the radiographic images are not in a stable form until the film is processed in a conventional manner in a “dark room”. Similarly, in the case of machine-read radiography plates, the cassettes are designed to be inserted into a cassette-reading machine, which is able to remove the radiographic plates from the cassettes and then read the information on those plates. 
   Although cassette-reading machines are able to “automatically” read the radiographic information stored on machine-read radiography plates, there nevertheless can be considerable delay in the processing of such plates by the cassette-reading machines. Likewise, there can be considerable delay in the processing of photographic film-type radiography plates by film-development equipment. These delays are attributable to the fact that radiography plates are seldom processed, either by cassette-reading machines or by film-development equipment, immediately subsequent to the radiograph exposures. Rather, there tends to be a time gap between the times at which the radiograph exposures occur and the times at which the radiography plates are processed. 
   A primary reason for this time gap is that radiography machines typically are not physically located proximate the cassette-reading machine or film-development machine at which cassettes are processed. This is due in part to the desirability of using portable radiography machines that can be brought to a patient&#39;s location. As a result, when radiographs are taken, the cassettes typically need to be hand-delivered back to the cassette-reading machine or film-development machine for processing, which can take a significant and variable amount of time depending upon the person delivering the cassette. A second reason for the time gap between radiograph exposures and the processing of radiography plates is that radiographic images are often acquired in batches by the technicians who perform the radiographic tests. That is, numerous tests on multiple patients, sometimes situated in different medical units (e.g., Trauma, Intensive Care, Burn, etc.), are often performed by a technician over the course of several hours before a batch of radiographic plates is turned in by the technician for processing. 
   Despite the existence of these delays, the typical protocol for assigning imaging times to radiography plates indicating the times at which the plates were exposed to x-ray radiation during radiographic procedures is simply to assign the times at which the plates are being processed as the times at which the radiographs were taken. In the case of machine-read radiography plates, in particular, cassette-reading machines typically assign the times at which they process cassettes as the times at which the radiographic information was obtained. Likewise, in the case of photographic film-type radiography plates, typically it is the times at which the plates are processed by film-development equipment that are assigned as the images as the exposure times. 
   While the times at which radiography plates are processed is often an adequate proxy for the times at which radiographic images were taken, this is not always the case. The existence of these differences between the times at which radiography tests are performed and the times that are assigned to the images resulting from those tests can become particularly disadvantageous in circumstances where a given patient is undergoing relatively rapid changes, or where a given patient is undergoing repeated radiography tests in a relatively short amount of time. In such circumstances, it can become particularly important for physicians and others to understand the exact times at which images have been taken, to understand the rapidity of changes that are occurring in a patient. Further, it is particularly important in such circumstances that the proper order in which different images have been taken be readily apparent to a physician or other personnel reviewing the images. Yet the conventional manner of assigning times to radiography images can make it difficult or impossible for physicians and others to understand the temporal relationships among different radiography images. 
   Indeed, in some circumstances, the conventional manner of assigning times to radiography images can cause a misinterpretation of the different images and consequently cause a misunderstanding of a patient&#39;s condition. For example, if a patient&#39;s condition suddenly begins to deteriorate, a STAT film may be requested by a physician and nearly immediately a technician may proceed with performing a radiographic test and have the radiography plates processed. If, prior to the change in the patient&#39;s condition, an earlier set of radiographic tests were performed and the processing of the resulting radiography plates has not yet been completed, it is possible that the earlier-obtained radiography images may be assigned later times than the rushed images. A physician reviewing the entire set of processed images, then, may be presented with images that misrepresent the overall progress of a patient&#39;s condition. 
   It therefore would be advantageous if a new radiographic device and/or technique was developed that allowed times to be assigned to radiographic images that more accurately reflected the actual times at which the radiographic tests that produced the images were performed. It further would be advantageous if such a new radiographic device and/or technique could be easily and inexpensively implemented in relation to radiographic images obtained using both film-type and machine-read radiography plates. Further, insofar as conventional radiography plates are relatively expensive devices, it would be advantageous if such a new radiographic device and/or technique could be easily and inexpensively applied to existing radiography plates. 
   SUMMARY OF THE INVENTION 
   The present inventors have recognized that the problems associated with ascribing the proper times to radiographic images could be eliminated if the radiography cassettes themselves included circuits that automatically recorded when the radiography cassettes were exposed to radiation during radiography tests. With such circuits embedded within or fixedly attached to the cassette housings, or fixedly attached to the radiography plates within the cassette housings, the ascribing of times to the radiographic images would be independent of the times at which the radiography plates were processed, either in a dark room or by way of a cassette-reading machine, and instead truly be reflective of the times of radiation exposure. In particular, the present invention relates to a radiation exposure recording device that includes a radiation exposure recording medium, a housing that at least partly surrounds the radiation exposure recording medium, and a first detector that detects a first radiation exposure and produces at least one signal in response to detecting the first radiation exposure. 
   Further, the present invention relates to a radiation exposure detection device for implementation on a radiography cassette. The detection device includes a radiation-sensitive component that provides a signal upon being exposed to radiation, and a mechanism capable of attaching the radiation-sensitive component to the radiography cassette. 
   Additionally, the present invention relates to a radiography method that includes providing a first radiation exposure recording medium, providing a first radiation exposure detector, and sensing an exposure of radiation at the first radiation exposure detector. 
   These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of an exemplary Prior Art radiography cassette; 
       FIG. 2  is a schematic view of a radiography machine taking a radiograph of a patient using the radiography cassette of  FIG. 1 ; 
       FIG. 3  is a perspective view of an exemplary radiography cassette in accordance with one embodiment of the present invention; 
       FIG. 4 . is a block diagram showing exemplary components of a circuit employed in the radiography cassette of  FIG. 3 ; 
       FIG. 5  is a perspective view of an exemplary, modified radiography cassette having a circuit for detecting radiation exposure attached to its outer surface, in accordance with another embodiment of the present invention; 
       FIG. 6  is a perspective view of an additional exemplary radiography cassette in accordance with a further embodiment of the present invention, where one or more circuits for detecting radiation exposure are attached to a radiography plate within the cassette; and 
       FIGS. 7–8  are additional perspective views showing additional exemplary radiography cassettes in accordance with further embodiments of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , an exemplary prior art radiography cassette  10  is shown to include a radiography plate  20  and a cassette housing  30 . The cassette housing  30  is typically made from plastic or some other material that blocks the transmission of visible light yet is essentially transparent with respect to radiation of wavelengths that are commonly employed by radiographic machines (e.g., x-rays). Commonly, the cassette housing  30  and the radiography plate  20  are generally rectangular and the cassette housing, which is intended to entirely (or at least substantially) contain the radiography plate, has a thickness  40  that is substantially less than its width  50  or height  60 . The radiography plate  20  is capable of being inserted and removed from the cassette housing  30  by way of an opening  70  that can be formed when a hinged door portion  80  of the cassette housing  30  is swung open. In the embodiment shown, the hinged door portion  80  of the cassette housing  30  additionally has a small window  90  on one of its surfaces, which allows certain information that is printed on the radiography plate  20  to be visible to someone even when the hinged door portion  80  is closed such that the radiography plate is fully contained within the cassette housing. It is known for such information printed on the radiography plate  20  to include a serial number of the radiography plate, in particular. 
   Turning to  FIG. 2 , as is known in the prior art, the radiography cassette  10  can be utilized to take radiographs (that is, radiographic pictures) of portions of a patient  100  when the patient is exposed to radiation  110  emitted by a radiation source  120 . Although not shown in detail,  FIG. 2  is intended to be representative of a variety of radiography machines that generally employ a radiation source and a radiography cassette including, for example, various x-ray machines, computed tomography (“CT”) machines, and other radiography machines. As discussed in the Background of the Invention above, the radiography plate  20  within the cassette housing  30  generally can be one of two types. A first type of radiography plate  20  is essentially a sheet of photographic film that, after being exposed to radiation, must be processed by a technician in a dark room or similar film development environment using known film-developing machines and processes. A second type of radiography plate  20  employs a sheet that records radiation exposure and, after radiation exposure has occurred, is capable of being read by a cassette-reading machine (not shown). As discussed above, the reading of the sheet typically occurs by scanning the sheet with a small area beam to release the energy stored in the sheet as light, sensing the emitted light, and generating electrical signals in response to the light, where the electrical signals can then be digitized, stored and/or output. 
   Turning to  FIG. 3 , in accordance with a first embodiment of the present invention, an improved cassette  130 , in addition to housing the radiography plate  20  and having the window  90  by which information printed on the radiography plate is visible from outside the cassette, has an improved cassette housing  140  that in particular includes a specialized sensing circuit  150 . The circuit  150  is sensitive to radiation at the levels produced by a radiation source of a radiography machine (such as the source  120  of  FIG. 2 ) and, in response to sensing the occurrence of such radiation, is capable of providing an indication or output signal that such radiation has occurred. Depending upon the embodiment, the circuit  150  is capable of sensing various attributes including, for example, sensing that a radiation exposure has occurred, sensing that a radiation exposure at or above a particular threshold magnitude has occurred, and/or sensing an accumulated amount of radiation exposure that has occurred thus far since a starting time. 
   The signal(s) output by the circuit  150  also can vary depending upon the embodiment. For example, in a preferred embodiment, and as discussed in further detail with reference to  FIG. 4 , the circuit  150  not only detects that a radiation exposure has occurred, but also determines and indicates (and/or stores) the time of the radiation exposure. Also for example, in other embodiments, the signal(s) output by the circuit  150  are capable of indicating a total accumulated magnitude of radiation exposure that has occurred thus far, and/or capable of causing the radiation source  120  to modify or stop the emitted radiation or modify some other aspect of the radiation treatment. In such embodiments, the signals output by the circuit  150  can be simply indicative of the accumulated magnitude of radiation exposure that has occurred, to allow the radiation source  120  or related device to determine what action to take based upon that information, or alternately can be signals that directly cause the radiation source  120  to modify or stop emitting radiation (or otherwise modify some aspect of the radiation treatment process), in which case the circuit  150  operates as a phototimer. 
   The output(s) of the circuit  150  in its various forms can be provided, depending upon the embodiment, in digital or analog form. Also, the circuit  150  can be implemented using any of a variety of known hardware and/or software technologies including, for example, through the use of one or more microprocessors, application-specific integrated circuits (ASIC), discrete circuit components and/or software implemented on a microcomputer/microprocessor or other computing device. 
   Referring to  FIG. 4 , a preferred embodiment of the circuit  150 , shown as a circuit  250 , includes several components. Specifically, a radiation sensitive circuit  160 , which detects radiation exposure, provides a signal  170  that is indicative that radiation exposure has occurred to a storage register  180  that also is coupled to a clock circuit  190  that provides clock signals  200  to the storage register. The storage register  180 , upon receiving the signal  170  from the radiation sensitive circuit  160 , stores a time at which a radiation exposure has occurred based upon the signals from the clock circuit  200 . This information in turn can be sent by way of a further signal  210  to an output circuit (or interface)  220  that is capable of further providing an output signal  230  to another location or device. Further as shown, in at least one embodiment, the clock circuit  190  is further coupled to an interface to time synchronizing system  240 , by which the clock circuit  190  is able to communicate with a reference and thereby verify that the time information that it is providing by way of the clock signals  200  is correct. The circuit  250  further can be powered by way of a battery (not shown) and/or by way of a power line coupled to the circuit or the radiography cassette (in certain embodiments, the battery can be recharged by power from a power line when such power line is intermittently connected). 
   The circuit  250 , and specifically the radiation sensitive circuit  160 , can in certain embodiments be “one-shot” devices that are only capable of detecting a single exposure of the radiography cassette to radiation, and thereafter incapable of detecting any further exposures. In such embodiments, the storage register  180  only stores a single time corresponding to the single time of exposure as indicated by the signal  170 , and the output circuit  230  only indicates a single time of exposure. In other embodiments, the circuit  250  is capable of detecting later radiation exposure(s) subsequent to detecting a first radiation exposure. In some embodiments of this type, the storage register  180  stores times corresponding to each time the storage register receives the signal  170  from the radiation-sensitive circuit  160  indicating that an exposure has occurred. In other embodiments of this type, the circuit  250  is resettable and only stores the time of occurrence of a new radiation exposure after it has been reset subsequent to a previous radiation exposure. Such resetting, in certain embodiments, can be manually triggered (e.g., by way of a button, not shown) or triggered by the cassette-reading machine during the cassette reading process, or occur automatically after a certain period of time has elapsed subsequent to a previous radiation exposure. 
   While the present invention is generally intended to encompass any of a variety of different radiography cassettes that employ, in addition to a radiography plate that constitutes the recording medium, an additional sensing device for sensing the exposure of the cassette/plate to radiation and providing an indication or signal as a result thereof, the present invention is particularly advantageous when implemented in a manner that includes the clock circuit  190  or a similar time measuring device. By using such a device, it is possible to provide an accurate indication of when a given radiography test was performed. Further, because the time recording operation is automatic and does not rely upon any human intervention, the time recorded and output by the circuit  250  (or similar circuit employing a time measuring device) is much more reliable as an indication of when a given radiography test was performed than the times ascribed to the radiography tests by technicians or cassette-reading machines after the fact, as is conventionally done. 
   Although not shown in  FIG. 3  or  4  in detail, the output circuit  220  can include any of a variety of different types of circuit components capable of transmitting or outputting signals to other devices. For example, the output circuit  220  can include an RS-232 port or USB port by which the output circuit  220  can be coupled to a complementary port within a cassette-reading machine or to a cable that in turn is coupled to such a machine or to another device (such as a personal computer). Also, in other embodiments, the output circuit  220  can include a wireless transmitter by which information is transmitted using wireless Ethernet, RF transmission or IR transmission techniques, as are known to those of ordinary skill in the art. In other embodiments, the output circuit  220  is a display or audio device, and the output signal  230  is a visual or audio output. The radiation sensitive circuit  160  also can take on a variety of different forms, including, for example, a radiation sensitive photo-emitting diode that produces a light signal as the signal  170  when the radiation sensitive circuit  160  is exposed to radiation during a radiography test. The storage register  180  and clock circuit  190  also can employ any of a variety of conventional devices for storing information and providing timing signals as are known to those of ordinary skill in the art. 
   Referring to  FIG. 5 , in a further embodiment of the present invention, the conventional cassette  10  of  FIG. 1  is retrofitted with a form of the circuit  150 , shown as a circuit  270 , which is attached to an outside surface  260  of the cassette housing  30 . In this embodiment, the circuit  270  is capable of taking on any of the structures and features of the circuits  150 ,  250  and other circuits previously described. However, the circuit  270  is an add-on device that can be attached to the outer surface  260  of the cassette housing  30  by any conventional attachment technique such as, for example, a glue or adhesive substance, or by way of attachment components such as screws, clips, etc. Preferably, once attached, it is difficult to remove the circuit  270  from the cassette housing  30  such that it is unlikely that the circuit  270  will inadvertently fall off of the cassette housing in a manner that might result in confusion as to whether any information stored on the circuit (or other status of the circuit) applied to the particular cassette  10 . In the embodiment shown, the circuit  270  is in the shape of a card such that it preferably does not increase the overall thickness of the cassette  10  by any more than a relatively small amount. In other embodiments, the circuit  270  can take on other shapes and sizes. 
   Referring to  FIG. 6 , a further embodiment of an improved cassette  280  is shown. The cassette  280 , in contrast to the cassette  130 , employs a special circuit  290  on its radiography plate  300  rather than on a cassette housing  310 . Further as shown, in certain embodiments the circuit  290  is able to display information, for example, by way of a liquid crystal display  295 . In such embodiments, an additional window  320  can be formed on the cassette housing  310  to allow for inspection of such information displayed on the display  295  from outside the cassette  280 . Depending upon the embodiment, the information to be output by the circuit  290  can also be output in other manners as discussed with reference to  FIG. 4 , for example, by way of wireless transmission or by way of direct electrical coupling. Since the circuit  290  is mounted on or otherwise forms part of the radiography plate  300 , direct electrical coupling is possible when the plate  300  is removed from the cassette housing  310  (e.g., removed by a developer in a dark room or automatically by a cassette-reading machine) or, alternately, by way of an internal connection between the radiography plate  300  and the cassette housing  310 , which in turn could be directly electrically coupled to another component. 
   Referring still to  FIG. 6  and additionally to  FIGS. 7 and 8 , in certain embodiments, more than one of the circuits  290  shown in  FIG. 6  or the circuits  150 ,  250 ,  270  of  FIGS. 3–5  (or other circuits serving the same purposes as these circuits) can be mounted at different locations on the cassette  280 . In the embodiment shown in  FIG. 6  in particular, the circuit  290  serves as an indication of whether a top portion  330  of the cassette  280  has been exposed to radiation, while a second circuit  340  serves as an indicator of whether a bottom portion  350  of the cassette has been exposed to radiation. As shown, the circuits  290  and  340  are respectively aligned with corresponding windows  320  and  360 , to allow for visually-displayed output. However, in other embodiments, the exact configurations of the circuits  290  and  340  and their orientations and relationships with other portions of the cassette  280  need not be as shown in  FIG. 6 . 
   For example,  FIGS. 7 and 8  show additional configurations of cassettes  280  on which multiple circuits  370  and  380 , respectively, are employed.  FIG. 7  in particular shows three circuits  370  positioned side-by-side along a midsection of the cassette, such that each of the circuits would be capable of detecting different radiation exposures occurring at three different column-type regions  375  of the cassette. Further,  FIG. 8  shows nine circuits  380  that are positioned generally in a three-by-three matrix arrangement, such that those circuits would be respectively capable of detecting different radiation exposures at any of nine sections  285  of the cassette. Each of the circuits  370 ,  380  can be of any of the types of the circuits  150 ,  250 ,  270  and  290  of the previous FIGS. (or other circuits serving the same purposes as those circuits). 
   By employing multiple circuits such as the circuits  150 ,  250 ,  270 ,  290 ,  340 ,  370  and  380 , it is possible not only to detect differently-timed radiation exposures of different portions of a cassette, but also possible to detect different magnitudes of radiation exposure (or even different types of radiation exposure, such as exposures to radiation of different wavelengths) occurring at different portions of the cassette. It is likewise possible to determine different times at which different magnitudes of radiation exposures have occurred, to detect accumulated amounts of radiation exposure that have occurred with respect to different sections of the cassette, and to determine other characteristics of interest. 
   Further, output signal(s) from the various circuits can be utilized in a variety of ways, both individually and in combination. For example, output signal(s) from two circuits corresponding to the radiation exposures that have occurred at two different sections of the cassette can be summed to obtain a total radiation exposure for the overall region including both of those sections. Also, for example, a radiation source  120  can vary its operation based upon the various signals from the various multiple circuits, e.g., when it is determined that two sections of a cassette have received uneven amounts of radiation exposure, the radiation source could vary the direction of the radiation  110  so that it impinges more directly one section of the cassette instead of another. Multiple radiation sources also could be controlled, respectively, based upon the output signals from the various respective circuits. For example, each respective circuit could operate as a distinct phototimer and provide signals to a respective radiation source that cause that source to modify or shut off after a certain amount of time and/or radiation exposure. 
   When different circuits are intended to detect radiation exposures associated with different sections of a cassette, it is not necessary that those sections be identical in size. Although only two circuits  290 , 340 , three circuits  370  and nine circuits  380  are shown in FIGS.  6 , 7  and  8 , respectively, it is also possible to have other numbers of such circuits associated with any given cassette. Also, it is not necessary for each of the circuits on a given cassette to be of the same type. For example, with respect to  FIGS. 7 and 8 , the circuits located at the centers of the cassettes shown in those respective FIGS. could of the same type as the circuit  150  of  FIG. 3  while the others could be of the same type as the circuit  270  of  FIG. 5 . 
   It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.