Abstract:
An X-ray CT apparatus includes an X-ray tube configured to emit X-rays, a detector faced against the X-ray tube, the detector having a detector element with a plurality of slots and a plurality of a collimator boards inserted into the slots, a data acquisition system configured to receive data detected by the detector, a computer unit configured to reconstitute the data from the data acquisition system and a display configured to show images by the data.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2005-276726, filed on Sep. 22, 2005, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to an X-ray CT(computer tomography) apparatus, an X-ray detector and a method of manufacturing an X-ray detector. 
   2. Description of the Related Arts 
   In an X-ray CT apparatus, X-rays are emitted from an X-ray tube and are formed into a fan-like shaped X-ray beam by a collimator. 
   The X-ray tube, and a circular arc like detector and a collimator facing the X-ray tube are rotated around a target object. 
   The detector receives X-rays which have passed through the target object and obtains X-ray information as a signal from the received X-ray. An X-ray tomography picture of the target object is obtained by processing the X-ray information by using a computer. 
   Some of the X-rays emitted from the X-ray tube travel straight and penetrate the target object, and other X-rays are scattered by the target object. 
   The collimator has a collimator board provided in front of the detector. The collimator removes the scattered X-rays incident from the oblique direction. The collimator passes the X-rays which have traveled straight and penetrated the target object. The collimator board forms an X-ray shield wall in front of the detector. The detector has detection elements which are arranged in a one- or two-dimensional manner.  FIG. 17  and  FIG. 18  show perspective views of known collimators and X-ray detectors.  FIG. 17  shows a collimator having a collimator board arranged in the one-dimensional manner.  FIG. 18  shows a collimator having a collimator board arranged in the two-dimensional manner. 
   In  FIG. 17 , collimator boards  50 ,  51  are shown together with a detection element array  52 . In  FIG. 18 , a collimate board  53  is shown together with a detection element array  54 . 
   The collimator arranged in one-dimension removes scattered X-rays in a certain direction, for example, a channel direction. The collimator arranged in two dimensions removes scattered X-ray in two directions, for example, channel and slice directions. 
   When manufacturing the X-ray detector, a collimator and an X ray detector are needed to be assembled with sufficiently accurate positioning. 
   This is because the collimator and the X ray detector are manufactured separately as shown in  FIG. 17  or  FIG. 18 . 
   The collimator may contain a plurality of Mo(Molybdenum) boards. The X-ray detector may contain a reflector. In the assembling process, it is necessary to position the collimator and the X-ray detector with a small gap in a rotating direction. 
   But it takes considerable time to carry out the assembling process with high positioning accuracy. 
   BRIEF SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide an X-ray CT apparatus positioning which may be manufactured with high positioning accuracy and in a relatively short time. It is another object of the present invention to provide an X-ray detector which may be manufactured with high positioning accuracy and in a relatively short time. It is further another object of the invention to provide a method of manufacturing an X-ray detector with high positioning accuracy and in a relatively short time.
     1. According to one embodiment of the present invention, an X-ray CT apparatus, is provided, which includes an X-ray tube configured to emit X-rays, a detector faced against the X-ray tube, the detector having a detector element with a plurality of slots and a plurality of a collimator boards inserted into the slots, a data acquisition system configured to receive data detected by the detector, a computer unit configured to reconstitute the data from the data acquisition system and a display configured to show images by the data.   2. According to another embodiment of the present invention, an X-ray CT apparatus, is provided, which includes an X-ray tube configured to emit X-rays, a detector faced against the X-ray tube, the detector having a detection element with a plurality of first and second slots, the first slots processed in parallel with a slice direction and formed in a channel direction at a space, the second slots processed in parallel with the channel direction and formed in the slice direction at a space, a reflective and adhesive material filled in the first and second slots, a data acquisition system configured to receive data detected by the detector, a computer unit configured to reconstitute the data from a data acquisition system, a display configured to show images by the data and a plurality of collimator boards inserted into the first and second slots.   3. According to another embodiment of the present invention, an X-ray detector, is provided, which includes a detection element having a plurality of slots and a plurality of collimator boards inserted into the slots.   4. According to another embodiment of the present invention, an X-ray detector, is provided, which includes a detector element having a plurality of first slots processed in parallel with a slice direction and formed in a channel direction at a space and a plurality of second slots processed in parallel with the channel direction and formed in the slice direction at a space, a reflective and adhesive material filled in the slots and a plurality of collimator boards inserted into the first and second slots.   5. According to another embodiment of the present invention, a method of manufacturing X-ray detector, is provided, which includes processing a plurality of slots in a detection element, injecting a reflective and adhesive material into the slots, and inserting a plurality of collimator boards into the slots.   6. According to another embodiment of the present invention, a method of manufacturing X-ray detector, is provided, which includes processing a plurality of first slots parallel to a slice direction into the detection element, processing a plurality of second slots parallel to a channel direction into the detection element, injecting a reflective and adhesive material into the first slots parallel to a slice direction, injecting the reflective and adhesive material into the second slots, inserting a plurality of first collimator boards into the first slots, inserting a plurality of first collimator boards into the second slots, and polishing a field opposite to a slot formation side of the detection element.   

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
       FIG. 1  is a schematic view of one embodiment of an X-ray CT apparatus in accordance with the invention. 
       FIG. 2  is a perspective view of one embodiment of a detector in accordance with the invention. 
       FIG. 3  is a perspective view of another embodiment of the detector in accordance with the invention. 
       FIG. 4  is a perspective view showing slot processing for an embodiment of a detection element in accordance with the invention. 
       FIG. 5  is a sectional view showing slot processing of an embodiment of a detection element in accordance with the invention. 
       FIG. 6  is a perspective view showing an injecting reflective material serving as adhesive into a detection element of an embodiment in accordance with the invention. 
       FIG. 7  is a perspective view showing inserting a collimator board into a detection element of an embodiment in accordance with the invention. 
       FIG. 8  is a cross-sectional view showing a collimator board inserted into a detection element of an embodiment in accordance with the invention. 
       FIG. 9  is a cross-sectional view showing a polishing position of a detection element of an embodiment in accordance with the invention. 
       FIG. 10  is a cross-sectional view showing an X-ray passing route of an embodiment in accordance with the invention. 
       FIG. 11  is a perspective view showing slot processing for a detection element of an embodiment in accordance with the invention. 
       FIG. 12  is a perspective view showing an injecting reflective material serving as adhesive into a detection element of an embodiment in accordance with the invention. 
       FIG. 13  is a cross-sectional view showing inserting a collimator board into a detection element of an embodiment in accordance with the invention. 
       FIG. 14  is a perspective view showing a collimator board inserted into a detection element of an embodiment in accordance with the invention. 
       FIG. 15  is a cross-sectional view showing polishing position of a detection element of an embodiment in accordance with the invention. 
       FIG. 16  is a cross-sectional view showing polishing a detection element of an embodiment of in accordance with the invention. 
       FIG. 17  is a perspective view of a conventional collimator and collimator board. 
       FIG. 18  is a perspective view of another conventional collimator and collimator board. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows an X-ray CT apparatus. In  FIG. 1 , X-rays from an X-ray tube  1  are emitted to form a fan-like X-ray beam with a circular collimator  2 . 
   The X-ray tube  1 , a detector  10  and the circular collimator  2  facing the X-ray tube  1  are rotated around reference to a target object  3 . 
   The detector  10  obtains X-ray information as a signal from X-rays which have passed through the target object  3 . An X-ray tomography picture of the target object  3  is obtained by processing the signal by using a computer unit  4   b.    
   Some of the X-rays emitted from the X-ray tube  1  travel straight and penetrate the target object  3 , and others of the X-rays are scattered by the target object  3 . 
   The collimator  2  has a collimator board provided in front of the detector  10 . The collimator removes the scattered X-rays incident from the oblique directions. The collimator passes the X-rays which have traveled straight and penetrated the target object  3 . 
   The collimator board functions as an X-ray shield wall in front of the detector  10  which is arranged in a one- or two-dimensional manner. The detector  10  obtains the X-ray information as a signal from received X-rays which have passed through the target object  3 . The target object  3  is placed on a couch  3   a.    
   The X-ray information is sent to a data acquisition system  4   a  from the detector  10 . The data obtained from the data acquisition system  4   a  is sent to a computer unit  4   b  to display a tomography pictures on a display  4   c . The computer unit  4   b  stores and reconstitutes the data. In U.S. Pat. No. 6,188,744, the entire contents of this reference being incorporated herein by reference. 
     FIG. 2  is a perspective view to show a detector  10  with a collimator arranged in the one-dimensional manner according to one embodiment of the invention. 
     FIG. 3  is a perspective view to show a detector  10  with a collimator arranged in the two- dimensional manner. A space between one slot and another slot may be regular or may not be regular. 
   In the embodiment shown in  FIG. 2 , laminated X-ray detection elements  11  constituting a part of the detector  10  detect the quantity of the received X-rays. 
   The detector  10  is made by alternately adhering slender and square shaped X-ray detection elements  11  and slender square shaped reflectors  17  (reflective material) respectively extending, in a channel direction (a rotating direction of the detector  10 ) and being arranged adjacently in a slice direction. 
   A plurality of slots  12 , which have been processed in the slice direction of the laminated X-ray detection elements  11 , as shown in  FIG. 4 , are provided in the channel direction. 
   The board-like X-ray shield board (collimator board)  13  is inserted in each of the slots  12 . In  FIG. 4 , a blade  9  is used to process the slots  12 . 
   X-rays shield boards  13  absorb the X-rays (scatted X-rays) which do not enter straight into the detector  10 . 
   The X-ray shield boards  13  are disposed so as not to contact the bottom of each of the slots  12  by gap control, as shown in  FIG. 8 . 
   The gap control is carried out so that X-ray shield boards  13  may be inserted so as not to contact the bottoms of the slots. 
   After inserting the X-ray shield boards  13 , a back surface of the laminated elements X-ray detection elements  11  is polished with a scintillator (X-ray detection element) polishing tool as shown in  FIG. 8 . 
   If the X-ray shield boards  13  contact the bottoms of the slots  12 , the back surface of the laminated X-rays detection element  11  is not polished with a scintillator polishing tool  9 . This is because the X-ray shield boards  13  are made of metal which is hard and may be difficult to polish. The X-ray shield boards  13  are formed except for a polishing area. Therefore, the gap control may not always be necessary, if a polishing tool can polish the laminated elements X-ray detection elements  11  and the X-ray shield boards  13 . A reflective material  15  serving as an adhesive is applied to the slots  12 . The reflective material is a gel-like material. By hardening after applying the reflective material, the reflective material works like an adhesive, as shown in  FIG. 6 . 
   Before applying the reflective material  15  serving as an adhesive and hardening it, the X-ray shield boards  13  are inserted in the slots  12 . 
   It may be unnecessary in this embodiment to carry out positioning of the reflective boards  15  and the X-ray shield boards  13  as conventional structures. 
   This is because the reflective material  15  serving as adhesives and the X-ray shield boards  13  are united as shown in  FIG. 7 . 
   This structure makes it easy to have X-rays reach photo-diodes  6  provided on a back side of the X-ray detection elements  11 , as shown in  FIG. 10 . It is because X-rays reflect by the reflective material  15  in the laminated elements X-ray detection elements  11 . 
   Scattered X-rays of the channel direction can be absorbed and removed by installing X-rays shield boards to be arranged adjacently in the slice direction perpendicular to the channel direction. 
   In  FIG. 3 , a plate-like X-ray detection element  21  is used to form X-ray shield boards  23  as well as X-ray shield boards  13   a , unlike the laminated X-ray detection element in  FIG. 2 . 
   A comb-like X-ray shield boards  23  are inserted in each of a plurality of slots  22  processed into the plate-like X ray detection element  21  in the perpendicular direction of the slice direction as shown in  FIG. 13 . The X-rays shield boards  13  are inserted in each of the plurality of slots  12   a  processed into the plate-like X-ray detection element  21  in the shield direction as shown in  FIG. 14 . 
   Reflective material  15   a  serving as an adhesive is applied to the slots  22  as well as the slots  12   a  as shown in  FIG. 12 . After applying the reflective material  15   a , the comb-like X-ray shield board  23  is inserted. 
   It is not always necessary to carry out positioning of reflective boards and the X-ray shield boards  13   a ,  23  as shown in  FIG. 15 , unlike conventional structures. 
   The scattered X-rays in the channel direction may be removed by installing the X-ray shield boards  13   a  in the direction perpendicular in the channel direction. 
   Further, the scattered X-rays in the slice direction may be removed by the comb-like X-ray shield boards  23  installed in the perpendicular direction of the slice direction as shown in  FIG. 10 . 
   Though, in  FIG. 3 , the comb-like X-ray shield boards  23  are installed in the perpendicular direction of the slice direction, the X-ray shield boards are not restricted to the comb-like structure or shape. Separate sheet-like X-ray shield boards may be used instead of the comb-like X-ray shield boards  23 . Mixture of the separate sheet-like and comb-like X-ray shield boards may be used. 
   The board-like X-ray shield boards  13   a  and the comb-like X-ray shield boards  23  are made of molybdenum (Mo.), because Mo is a high rate material of X-ray interception. However, another material may be used instead of Mo. 
   With reference to  FIG. 4  to  FIG. 9 , a manufacturing method of the detector  10  of  FIG. 2  will be explained.
         (1) In  FIG. 4 , polishing is performed to the upper surface of a laminated elements X-ray detection elements  11 , to which a reflector (reflective material)  17  is installed in the direction of a channel. The polishing is performed using whetstone or by a polishing machine to form slots  12 .   (2) In  FIG. 4 , the slot  12  processing is provided to the direction parallel to the slice direction by using the blade  9  as the processing tool. The slots  12  are formed respectively in the direction toward an X-ray focus. The slots  12  do not reach the laminated elements X-ray detection elements  11 . For example, it is left about a 0.3 mm depth remains from the undersurface of the laminated elements X-ray detection elements  11  to the slots  12  as shown in  FIG. 4  and  FIG. 5 .       

   However, if the undersurface of the laminated elements X-ray detection elements  11  is fixed with wax, etc. to avoid parting, the slots  12  may reach the undersurface of the laminated elements X-rays detection elements  11 .
         (3) The reflective material  15  serving as an adhesive is injected into the slots  12  as shown in  FIG. 6 .   (4) X-ray shield boards  13  are inserted in the slots  12 .
 
The X-ray shield boards  13  are inserted so as not to touch bottoms of the slots  12  as shown in  FIG. 7  and  FIG. 8 .
   (5) After the reflective material  15  is hardened, the undersurface of the laminated X-ray detection elements  11  are polished to the position where the reflective material  15  can be seen, as shown in  FIG. 9 .       

   Referring to  FIG. 11  to  FIG. 16 , the manufacturing method of the detector of  FIG. 3  will be explained.
         (1) As shown in  FIG. 11 , an upper surface of an X-ray detection element  21  is polished.   (2) The X-ray detection element  21  is polished in the channel direction and in the slice direction with the blade  9 .
 
Slots  12   a  and Slots  22  are formed respectively, in the direction toward an X-ray tube focus.
 
The slots  12   a  and the slots  22  do not reach the laminated X-rays detection elements  11 . For example, about a 0.3 mm depth is left from the undersurface of the laminated X-rays detection elements  11  to the slots  12   a  as shown in  FIG. 11 . The slots  12   a  is defined as first slots, and the slots  22  is defined as first slots.
   (3) A reflective material  15  is injected into the slots  12   a  and the slots  22  as shown in  FIG. 12 .   (4) The comb-like X-ray shield boards  23  are inserted in the slots  22  after the injection. Then, the X-ray shield boards  13  are inserted into the slots  12   a.          

   The X-ray shield boards  13  are provided so as not to touch bottoms of the slots  12   a  and the slots  22  as shown in  FIG. 13 , to  FIG. 15 .
         (5) After the reflective material is hardened, the undersurfaces of the laminated X-rays detection element  21  are polished to the position where the reflective material  15  can be seen, as shown in  FIG. 16 ).       

   The detector  20  in  FIG. 3  can absorb and intercept not only scattered X-rays of the channel direction but also those of the slice direction, because of honeycomb structure of the detector  20 , in comparison with the detector  10  in  FIG. 2 . 
   As a result, the detector  20  has a structure which can be bore during a high-speed scanning. 
   Because the X-ray shield boards  13   a  and the comb-like X-ray shield boards  23  are inserted in the X-ray detection elements  21  directly, a positioning process may be omitted to attain reducing a step of manufacturing, to increase accuracy and to improve strength. 
   Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. 
   Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.