Abstract:
An example CT scanner assembly includes a gantry having a first end and a second end rotatable about a first axis, an x-ray detector adjacent the first end, and an x-ray source adjacent the second end. The x-ray source directs an x-ray beam toward a portion of the x-ray detector. The x-ray source translates along a second axis aligned with the first axis when the gantry rotates.

Description:
[0001]     This application claims priority to U.S. Provisional Application No. 60/797538 filed May 4, 2006. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates generally to computer tomography (CT) scanners and more particularly to a CT scanner which collimates an x-ray to assist in analysis of x-ray scatter during a helical-type scan.  
         [0003]     Generally, CT scanners include a moveable ring with an x-ray source mounted on the movable ring and an x-ray detector mounted opposite the x-ray source. The patient lies on a platform that moves through the ring. The ring is rotated so the x-ray source and the x-ray detector revolve in a helical path around the patient while taking a series of x-rays. The x-ray source produces an x-ray signal that is directed toward the x-ray detector. The x-ray source and x-ray detector typically translate together when following the helical path.  
         [0004]     The x-ray signal scatters as it travels the distance between the x-ray source and the x-ray detector. The scatter alters the image that is created from the x-ray signal and hinders the doctor when analyzing the CT image. When the effect of the scatter is known, it can be filtered from the received signal to provide a more accurate image.  
         [0005]     Therefore, it is desirable to provide a CT scanner which supplies information on the scatter of an x-ray signal for use in analyzing the x-ray image.  
       SUMMARY OF THE INVENTION  
       [0006]     An example CT scanner assembly includes a gantry having a first end and a second end rotatable about a first axis, an x-ray detector adjacent the first end, and an x-ray source adjacent the second end. The x-ray source directs an x-ray beam toward a portion of the x-ray detector. The x-ray source translates along a second axis aligned with the first axis when the gantry rotates.  
         [0007]     Another example CT scanner assembly includes a gantry having an x-ray source and an x-ray detector rotatable about a patient to define an axis, and an x-ray beam moves from the x-ray source to the x-ray detector. The CT scanner includes at least one shield for collimating a portion of the x-ray beam and a computer for identifying scatter in an x-ray image using known scatter from a collimated portion of the x-ray beam.  
         [0008]     An example method for generating a CT image include the steps of: (a) rotating an x-ray source and an x-ray detector about a patient, (b) taking a plurality of x-ray images with the x-ray source and the x-ray detector during step (a), and (c) translating the x-ray source vertically during step (a). 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.  
         [0010]      FIG. 1  illustrates an example CT scanner having a gantry.  
         [0011]      FIG. 2  illustrates another example CT scanner having a gantry.  
         [0012]      FIG. 3  illustrates an example image from the CT scanner.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]      FIG. 1  illustrates a CT scanner  10  according to the present invention wherein all of the components are contained in a gantry  12 . The gantry  12  provides the structural support and housing for the components. The gantry  12  comprises a cross-bar section  14  from which a first arm  16  and a second arm  18  extend perpendicularly from either end, forming a c-shaped assembly.  
         [0014]     The first arm  16  houses an x-ray source  20  that generates x-rays  40 , which in this embodiment is a cone-beam x-ray source. The second arm  18  houses a complementary x-ray detector  22 . The cross-bar section  14  of the gantry  12  houses a motor  27  for rotating the gantry  12  relative to a mounting plate  26 . Alternatively, the motor  27  could be mounted off the gantry  12 . A pair of shields  24  are supported on the x-ray source  20  to collimate the x-rays  40 . In the embodiment shown, the pair of shields  24  block at least an upper and lower portion of the x-ray source  20 , preventing x-rays  40  from passing through the pair of shields  24 . Only the middle portion of the x-ray  40  passes through and is received by the x-ray detector  22 . Although not shown, the x-ray shields  24  would preferably block a portion of each side of the x-ray source  20 , allowing the middle portion of the x-ray  40  to pass through.  
         [0015]     The first arm  18  further includes an actuator  28  for moving the x-ray source  20  during scanning. In this example, the x-ray source  20  moves vertically during scanning in a direction aligned with, and substantially parallel to, the axis of rotation of the gantry  12 . In another example CT scanner, the x-ray source  20  moves horizontally as the gantry  12  rotates about a horizontal axis, as shown in an example scanner  50  of  FIG. 2 .  
         [0016]     Referring back to  FIG. 1 , the x-ray  40  shown projected on the x-ray detector  22  is moved from an upper portion of the x-ray detector  22  to a lower portion of the x-ray detector  22  (or vice versa) during scanning, as shown. The x-ray detector  22  is larger than the portion of the x-ray  40  striking the x-ray detector  22  directly, as is also shown.  
         [0017]     The example CT scanner  10  may further include a computer  30  including a microprocessor or CPU  32 , memory  34 , a monitor  36  and other hardware and software for performing the functions described herein. The computer  30  controls the rotation of the CT scanner  10 , the location and operation of the x-ray source  20  and the x-ray detector  22 , and collects the data from the x-ray detector  22  and stores it for later collection, such as in memory  34 , hard drive, optical, magnetic or other storage. The computer  30  could also be mounted on-board the gantry  12 .  
         [0018]     In operation, a part of the body, such as a head  38 , is positioned between the first arm  16  and the second arm  18  of the gantry  12 . The computer  30  powers the x-ray source  20 . The x-ray source  20  generates an x-ray  40  that is directed toward the x-ray detector  22 . The CPU  32  then controls the motor  27  to perform one complete revolution of the gantry  12 , during which time the computer  30  collects multiple images from the x-ray detector  22 . During the revolution, the actuator  28  moves the x-ray source  20  relative to the x-ray detector  22 , such that the x-ray source  20  follows a helical path to cover a larger portion of the patient during the revolution and to eliminate some cone-beam artifacts. The images taken by the x-ray detector  22  are stored in the storage  34 .  
         [0019]     An image  42  taken from the example collimated CT scanner  10  is shown in  FIG. 3 . An upper portion  44  and a lower portion  46  of the image  42  represent the portion of the x-ray  40  that is collimated by the pair of x-ray shields  24 . A central uncollimated portion  48  includes an image of the head  38 .  
         [0020]     The image  42  includes randomly distributed scatter. The upper portion  44  and the lower portion  46  represent only scatter, while the central portion  48  includes scatter and the image of the head  38 . Based upon the known scatter information provided in the upper portion  44  and the lower portion  46  of the image  42 , the computer  30  can predict the effect of the scatter on the image  42  and specifically the image of the head  38 . A person having ordinary skill in the art would be able to develop a suitable technique for predicting the effect of scatter on an image if provided known scatter information. The computer  30  uses the predicted effect of scatter to improve the image  42  by removing or reducing the effect of scatter in the image  42 .  
         [0021]     Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.