Patent Publication Number: US-2012043470-A1

Title: X-ray imaging apparatus

Description:
BACKGROUND 
     X-ray imaging is widely used in medical, industry, and security systems. An example of a conventional configuration for capturing an X-ray image on film is depicted in  FIG. 1 . More particularly,  FIG. 1  shows an X-ray source  102 , a scintillator  108 , and a film  110 . In operation, when X-rays  104  are emitted from the X-ray source  102 , the scintillator  108  converts the X-rays  104  into photons that are captured on the film  110 . When a blocking object  106  is positioned in the path of the X-rays  104 , the blocking object  106  blocks some of the X-rays  104  and an image  112  is formed in the film  110  from a contrast between locations in the film  110  where photons are captured and locations where photons are not captured. 
     Other types of X-ray imaging systems that use an Indirect Flat Panel Detector to take X-ray images instead of the film  110  have been gaining wider use. These types of systems employ an active matrix of amorphous silicon TFT as an imager that transfers the image light signals from the scintillator into electrical signals that are further digitized and processed by a computer. Although the amorphous silicon TFT panels provide good resolution and relatively high sensitivity, they are associated with relatively high manufacturing costs, especially when the panels are manufactured to have relatively large sizes. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The embodiments of the invention will be described in detail in the following description with reference to the following figures. 
         FIG. 1  illustrates a conventional configuration for capturing an X-ray image on film. 
         FIG. 2A  illustrates a simplified frontal view of an X-ray imaging system, according to an embodiment of the invention; 
         FIG. 2B  illustrates a simplified cross-sectional side view of a top transparent conductive layer depicted in  FIG. 2A , according to an embodiment of the invention; 
         FIG. 2C  illustrates a simplified frontal view of an X-ray imaging system, according to an embodiment of the invention; and 
         FIG. 3  illustrates a flow diagram of a method of capturing an X-ray image through use of the X-ray imaging apparatuses depicted in  FIGS. 2A and 2B , according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     For simplicity and illustrative purposes, the principles of the embodiments are described by referring mainly to examples thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments. It will be apparent however, to one of ordinary skill in the art, that the embodiments may be practiced without limitation to these specific details. In some instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the embodiments. 
     Disclosed herein is an X-ray imaging system having an X-ray imaging apparatus configured to cause an image of a blocking object to be displayed. The X-ray imaging apparatus includes an X-ray field modulator that is composed of a material configured to map differences in X-rays irradiated thereon by changing its resistance. The X-ray imaging apparatus also includes an electro-optic layer composed of a material that changes a visible property thereof with varying levels of voltage caused by differences in resistance in the X-ray field modulator, to thereby visibly show the differences in resistance in the X-ray field modulator. 
     Through implementation of the X-ray imaging apparatus disclosed herein, an instant X-ray image may be achieved. In addition, the visible image may easily be digitized by normal digital cameras and thus expensive large active TFT panels are not required. Moreover, fabrication of the X-ray imaging apparatus disclosed herein is associated with relatively low costs due to its relatively simple architecture. One result of this relatively low costs is that the X-ray imaging apparatus disclosed herein may be employed in relatively large-scale X-ray imaging operations, such as, imaging of entire human bodies, shipping containers, etc., in addition to use in smaller medical imaging operations. 
     With reference first to  FIG. 2A , there is shown a simplified frontal view of an X-ray imaging system  200 , according to an example. It should be understood that the X-ray imaging system  200  may include additional elements and that some of the elements described herein may be removed and/or modified without departing from a scope of the X-ray imaging system  200 . 
     As shown in  FIG. 2A , the X-ray imaging system  200  includes an X-ray source  202  and an X-ray imaging apparatus  210 . The X-ray source  202  may comprise an X-ray tube or other device configured to irradiate X-rays  204  in the direction of the X-ray imaging apparatus  210 . Although not shown, a collimator may be positioned between the X-ray source  202  and the X-ray imaging apparatus  210  to generally limit the range of X-ray irradiation in directions other than toward the X-ray imaging apparatus  210 . 
     A blocking object  206  is also depicted as being positioned between the X-ray source  202  and the X-ray imaging apparatus  210 . The blocking object  206  depicted in  FIG. 2A  generally represents an object, an article, a person or person&#39;s body part, etc., that is configured to be imaged using the X-ray imaging system  200 . 
     The X-ray imaging apparatus  210  is depicted as being formed of a number of components arranged in a layered structure. More particularly, the X-ray imaging apparatus  210  is depicted as including a top holding substrate  212 , a top transparent conductive layer  214 , an electro-optic layer  216 , an X-ray field modulator  218 , a bottom transparent conductive layer  220 , and a bottom holding substrate  222 . The layers of the X-ray imaging apparatus  210  may be held together through frictional forces or through use of transparent adhesives that do not substantially affect the transmission of X-rays  204  through the X-ray imaging apparatus  210 . In addition, or alternatively, the layers of the X-ray imaging apparatus  210  may be held together through use of mechanical fasteners or other mechanical devices. At least some of the layers of the X-ray imaging apparatus  210  requires a relatively high level of electrical conduction there between. For instance, a relatively high level of electrical conduction between the top transparent conductive layer  214  and the electro-optic layer  216  is preferable. To provide the relatively high level of electrical conduction, the top transparent layer  214  may be deposited onto the electro-optic layer  216 . 
     The top holding substrate  212  and the bottom holding substrate  222  generally provide support and protection to components of the X-ray imaging apparatus  210 . The top holding substrate  212  and the bottom holding substrate  222  comprise transparent devices configured to enable light and X-rays to penetrate therethrough. The top holding substrate  212  and the bottom holding substrate  222  are formed of glass, plastic, or like material. 
     The top transparent conductive layer  214  and the bottom transparent conductive layer  220  are generally configured to enable X-rays  204  and light to pass therethrough. In addition, the top transparent conductive layer  214  and the bottom transparent conductive layer  220  are connected together through a voltage source  240  and are configured to operate as electrodes by conducting electricity from the voltage source  240  through the electro-optic layer  216  and the X-ray filed modulator  218 . According to an example, the top transparent conductive layer  214  and the bottom transparent conductive layer  220  are formed of indium tin oxide (ITO) or equivalent material. 
     According to an example, one or both of the top transparent conductive layer  214  and the bottom transparent conductive layer  220  are electrically segmented. More particularly,  FIG. 2B  shows an example of the top transparent conductive layer  214  having alternating sections of electrically conductive segments  262  and electrically insulative segments  264  running from the top to the bottom of the transparent conductive layer  214 ,  220 , with the electrically conductive segments  262  in electrical contact with an electrode  260 . In instances where the bottom transparent conductive layer  220  is segmented, the bottom transparent conductive layer  220  may have a similar arrangement to that depicted for the transparent conductive layer  214 , except that the electrode  260  will be positioned at the bottom section of the bottom transparent conductive layer  220 . In various examples, the electro-optic layer  216  may also be configured to have the electrically conductive segments  262  and the electrically insulative segments  264 . 
     The electrically conductive segments  262  may be sized according to the level of resolution desired in images  230  formed the electro-optic layer  216 . Thus, for instance, the electrically conductive segments  262  may have relatively smaller sizes and positioned relatively close together when higher resolution images  230  are desired. By way of particular example, the electrically conductive segments  262  may comprise relatively thin discrete elements and the electrically insulative segments  264  may comprise an insulative layer deposited around the electrically conductive segments  262 . Alternatively, the electrically insulative segments  264  may be fabricated with holes into which the electrically conductive segments  262  are deposited or positioned. 
     The electro-optic layer  216  generally comprises a material that is transparent to X-rays  204  and configured to display different levels of contrast depending upon, for instance, the level of voltage applied therethrough. Thus, when a relatively consistent level of voltage is applied through the entire electro-optic layer  216 , the electro-optic layer  216  displays a substantially even image throughout. However, when the voltage varies for a section of the electro-optic layer  216 , such as by a voltage drop, that section of the electro-optic layer  216  has a different contrast as compared with the remainder of the electro-optic layer  216 . As discussed in greater detail herein below, one or more sections in line with a blocking object  206  may experience a voltage drop as compared with the rest of the electro-optic layer  216 , which causes an image  230  corresponding to the blocking object  206  to be displayed in the electro-optic layer  216 . 
     According to an example, the electro-optic layer  216  comprises a bi-stable material that enables the image  230  to be persistently displayed following removal of voltage. In this example, the electro-optic layer  216  may comprise at least one of an electrophoretic and a cholesteric material. Examples of suitable materials include materials available from the E-Ink Corporation of Cambridge, Mass. and from Sipix of Fremont, Calif. and Bridgestone of Tokyo, Japan. 
     According to another example, the electro-optic layer  216  comprises a material that is configured to cause the image  230  to be removed from the electro-optic layer  216  when the voltage is removed. In this example, the electro-optic layer  216  may comprise a material composed of twisted nematic liquid crystals. An X-ray imaging apparatus  210 ′ having an electro-optic layer  216  composed of twisted nematic liquid crystals is discussed in greater detail herein below with respect to  FIG. 2B . 
     The X-ray field modulator  218  is generally configured to generate electron hole pairs when exposed to X-rays  204 . The X-ray field modulator  218  is thus required to have a relatively strong interaction with the X-rays  204 . Examples of suitable materials are high Z materials, for instance, one or more elements from the bottom of the periodic chart. In operation, the X-ray field modulator  218  is configured to vary the resistance through the X-ray field modulator  218  when exposed to X-rays  204 , such that, the resistance of the X-ray field modulator  218  at locations that are blocked by the blocking object  206  differs from those locations that are not blocked by the blocking object  206 . The differences generally form a voltage map across the X-ray field modulator  218  that indicates the shape of the blocking object  206 . In this regard, the electro-optic layer  216  and the X-ray field modulator  218  generally operates as a voltage divider between the top transparent conductive layer  214  and the bottom transparent conductive layer  220 . 
     The differences in resistance at the locations of the X-ray field modulator  218  as denoted by the voltage map is reflected in the electro-optic layer  216  because the electro-optic layer  216  creates a visual representation of the voltage map. More particularly, for instance, there will be a voltage drop below the blocking object  206  that differs from a voltage drop across locations that are not below the blocking object  206 . In addition, because the optical properties of the electro-optic layer  216  depend upon the voltage drop level, the regions in the electro-optic layer  216  beneath the blocking object  206  will appear differently from the regions that are not beneath the blocking object  206 . 
     According to an example, the X-ray field modulator  218  comprises a relatively thick material having a relatively high-z value and configured to block about 50% of the X-rays  204 . Examples of suitable materials include gadolinium, sodium iodide activated by thallium (NaI:Tl), Yttirum aluminum perovskite activated by cerium (YAP:Ce), Yttrium aluminum garnet activated by cerium (YAG:Ce), Bismuth germanate (BGO), Calcium fluoride activated by Europium (CaF:Eu), Cesium iodide activated by thallium (CsI:Tl), Lutelium aluminum garnet activated by cerium (LuAG:Ce), Gadolinium silicate doped with cerium (GSO), Cadmium tungstate CdWO4 (CWO), Lead tungstate PbWO4 (PWO), Double tungstate of sodium and bismuth NaBi(WO4)2) (NBWO), ZnSe(Te), and the like. Other suitable materials include chalcogenides, such as, selenium, arsenic tri-solenide, or the like. 
     According to another embodiment, the X-ray field modulator comprises a charge node, such as a PIN diode in reverse bias. In this embodiment, instead of a current flowing through the X-ray field modulator  218 , charge is created within the X-ray field modulator  218  and is separated by the internal field of the PIN device thereby changing the field across the electro-optic layer  216 . The charge on the X-ray field modulator  218  exhibits spatial variation depending upon whether a blocking object  206  blocks the X-rays  204 . In addition, the charge in the electro-optic layer  216  beneath the blocking object  206  will differ from the charge in the electro-optic layer  216  in sections that are not beneath the blocking object  206 , which causes the optical properties of the electro-optic layer  216  to differ in those sections. 
     Turning now to  FIG. 2C , there is shown a simplified frontal view of an X-ray imaging system  200 ′, according to another example. It should be understood that the X-ray imaging system  200 ′ may include additional elements and that some of the elements described herein may be removed and/or modified without departing from a scope of the X-ray imaging system  200 ′. 
     The X-ray imaging system  200 ′ depicted in  FIG. 2C  contains all of the elements discussed above with respect to the X-ray imaging system  200  depicted in  FIG. 2A . As such, a detailed discussion of the common elements are omitted with respect to  FIG. 2C . Instead, only those elements that differ from the elements depicted in  FIG. 2C  will be described. 
     The principle difference between the X-ray imaging systems  200  and  200 ′ is that the electro-optic layer  216  depicted in  FIG. 2C  comprises twisted nematic liquid crystals. As such, the X-ray imaging apparatus  210 ′ further includes a vertical axis polarizer  250  and a horizontal axis polarizer  252  to enable images  230  in the electro-optic layer  216  to be visible. 
     According to an example, the X-ray imaging apparatuses  210 ,  210 ′ are designed for single use applications, and may thus be discarded after their use. In another example, however, the X-ray imaging apparatuses  210 ,  210 ′ are designed for multiple uses and the electro-optic layer  216  may be configured such that the image  230  may be “erased” from the electro-optic layer  216  between each use. The manners in which the image  230  may be “erased” from the electro-optic layer  216  may depend upon the materials and/or configuration of the electro-optic layer  216 , the voltage source waveform, polarity, etc. By way of example, when the electro-optic layer  216  is unable to maintain the image  230  when the voltage supply is cut off, such as, with twisted nematic liquid crystals, the image  230  may be erased by simply turning off the voltage supply to the top and bottom transparent conductive layers  214  and  220 . 
     However, in instances where the electro-optic layer  216  comprises a bi-stable material and/or configuration, the image  230  may be erased by applying a reverse bias voltage across the electro-optic layer  216 . In various instances, the image  230  may be erased through application of a sufficiently high voltage for a sufficiently long period of time to cause the image  230  in the electro-optic layer to saturate into one state, for instance, an even white color. 
     In any regard, an image of the image  230  may be captured through use of a digital camera (not shown). According to an example, the image  230  may be viewed and captured through the top transparent conductive layer  214 . In this example, the line of sight of the digital camera is directed toward the top of the X-ray imaging apparatus  210 ,  210 ′. In addition, the digital camera may be incorporated with the X-ray source  202  such that the digital camera may be employed to capture the image of the image  230  while the X-ray source  202  is active or immediately after the X-ray source  202  has been deactivated. In a further example, the X-ray imaging apparatus  210 ,  210 ′ may be moved to another location to be imaged by the digital camera after having been irradiated with the X-rays  204 . 
     According to another example, the image  230  may be viewed and captured through the bottom transparent conductive layer  220 . In this example, because the X-ray field modulator  218  is opaque, the X-ray field modulator  218  may be formed to have a mesh structure to enable at least a relatively high level of light to pass therethrough. In addition, any other opaque sections of the X-ray imaging apparatus  210 ,  210 ′ may be formed to have a mesh structure to enable light to pass therethrough. Again, the digital camera may be used to capture the image  230  while the X-ray source  202  is active or after the X-ray source  202  has been deactivated. The mesh structure(s) may also be employed in a configuration in which the X-ray source  202  is positioned to irradiate X-rays  204  from the bottom of the X-ray imaging apparatus  210 ,  210 ′. 
     An example of a method of capturing an X-ray image through use of the X-ray imaging apparatus  210 ,  210 ′ will now be described with respect to the following flow diagram of the method  300  depicted in  FIG. 3 . It should be apparent to those of ordinary skill in the art that the method  300  represents a generalized illustration and that other steps may be added or existing steps may be removed, modified or rearranged without departing from a scope of the method  300 . 
     The description of the method  300  is made with reference to the X-ray imaging systems  200 ,  200 ′ illustrated in  FIGS. 2A and 2B , and thus makes reference to the elements cited therein. It should, however, be understood that the method  300  is not limited to the elements set forth in the X-ray imaging systems  200 ,  200 ′. Instead, it should be understood that the method  300  may be practiced by a system having a different configuration than that set forth in the X-ray imaging systems  200 ,  200 ′. 
     At step  302 , an X-ray imaging apparatus  210 ,  210 ′ is positioned to receive X-rays  204  from an X-ray source  202 . The X-ray imaging apparatus  210 ,  210 ′ includes an electro-optic layer  216  and an X-ray field modulator  218 . As discussed above, the X-ray field modulator  218  is configured to vary at least one of a voltage and a charge through the electro-optic layer when irradiated with X-rays  204 . 
     At step  304 , a blocking object  206  is positioned between the X-ray source  202  and the X-ray imaging apparatus  210 ,  210 ′. The blocking object  206  comprises the object whose image  230  is to be captured in the X-ray imaging apparatus  210 ,  210 ′. 
     At step  306 , X-rays  204  are irradiated through the X-ray imaging apparatus  210 ,  210 ′ from the X-ray source  202  to cause an image  230  of the blocking object  206  to be formed in the electro-optic layer  216 . As discussed in greater detail herein above, the image  230  may be formed through changes in either the voltage or the charge throughout the X-ray field modulator  218  caused by different levels of X-rays  204  being irradiated onto the X-ray field modulator  218 . In addition, the image  230  may be persistently or temporarily formed in the electro-optic layer  216 . 
     At step  308 , a digital image of the image  230  in the electro-optic layer  216  is captured through use of a digital camera. As discussed in greater detail herein above, the image may be captured through the top and/or the bottom of the X-ray imaging apparatus  210 ,  210 ′. 
     What has been described and illustrated herein is a preferred embodiment of the invention along with some of its variations. The terms, descriptions and figures used herein are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that many variations are possible within the scope of the invention, which is intended to be defined by the following claims—and their equivalents—in which all terms are meant in their broadest reasonable sense unless otherwise indicated.