Method and apparatus for cephalometric imaging

Abstract

The invention relates to a method for cephalometric imaging using an apparatus ( 1 ) which comprises an X-ray source ( 5 ), a line detector camera ( 8 ) equipped with a digital detector, which line detector camera is located to a position far away from the X-ray source ( 5 ) for carrying out cephalometric imaging while the slot of the line detector camera is substantially vertical. In cephalometric imaging, an X-ray beam ( 11 ) located substantially on the vertical plane is directed from the X-ray source ( 5 ) through the object being imaged, and the X-ray source ( 5 ) is at the same time turned about the rotation center ( 13 ) located between the X-ray source and the line detector camera ( 8 ) in order to scan the object being imaged in the horizontal direction, whereby the line detector camera ( 8 ) is moved during the scanning movement in such a way that the ray beam ( 11 ) meets the slot ( 14 ) of the line detector camera. In the method, the effective focal spot is transferred from the rotation center ( 13 ) to the focal spot of the X-ray source ( 5 ) by transferring the rotation center by means of a transverse linear movement (A) with respect to the ray beam ( 11 ).

1. A method for operating a panoramic imaging apparatus to provide improved tomographic  cephalometric images, the panoramic imaging apparatus being capable of operating in a mode in which an X-ray source and radiation sensor, spaced from said radiation  X- ray  source at a first distance, are rotated about an intermediate vertical rotation center to provide a panoramic image from a subject positioned between the X-ray source and the radiation sensor, said method comprising the steps of:
 positioning a radiation receiver to receive radiation from said X-ray source, said radiation receiver being located at a second distance from said X-ray source greater than said first distance;  
 placing a subject for cephalometric imaging in front of the radiation receiver;  
 projecting radiation from the X-ray source along a horizontal radiation path to apply radiation from the X-ray source to the radiation receiver;  
 carrying out a first motion comprising rotating the X-ray source about the center of rotation  while otherwise maintaining the X- ray source generally stationary;    
 carrying out a second motion comprising horizontally translating the center of rotation in a direction generally transverse to the radiation path during application of the radiation to the radiation receiver;  
 wherein the effective focal spot of the X- ray source is transferred to the general location of the X - ray source ; and  
 carrying out a third motion comprising translating the radiation receiver in a horizontal direction generally transverse to the radiation path, said first, second, and third motions producing a tomographic  cephalometric image from the panoramic imaging apparatus for which the effective focal point for the X-ray source has been altered in a manner to reduce differences in vertical and horizontal ratios of enlargement.  
 
     
     
       2. The method according to  claim 1  further including the step of collimating the radiation applied to the radiation receiver. 
     
     
       3. An apparatus for providing a tomographic  cephalometric image comprising:
 a radiation receiver;  
 a panoramic imaging X-ray source providing radiation along a generally horizontally extending radiation path for application to said radiation receiver;  
 a support for said X-ray source, said support having a vertical rotation center for rotating said X-ray source, said rotation center being positioned intermediate said radiation receiver and said X-ray source and closer to said X-ray source than to said radiation receiver;  
 means for rotating said X-ray source about said rotation center  while otherwise maintaining the X- ray source generally stationary;    
 means for generally horizontally translating said rotation center in a direction generally transverse to the radiation path;  
 wherein the effective focal spot of the X- ray source is transferred to the general location of the X - ray source ; and  
 means for translating said radiation receiver in a horizontal direction generally transverse to the radiation path during application of the radiation to said radiation receiver,  
 the motions provided to said radiation  X- ray  source, rotation center, and radiation receiver by the respective means producing a tomographic  cephalometric image from a subject positioned in front of said radiation receiver for which the effective focal length of the X-ray source has been altered in a manner to reduce differences in the vertical and horizontal ratios of enlargement.  
 
     
     
       4. The apparatus according to  claim 3  wherein said radiation receiver comprises a line detection camera. 
     
     
       5. The apparatus according to  claim 3  further including a collimator for being placed in front of the subject. 
     
     
       6. A method for operating imaging apparatus to provide improved cephalometric images having reduced differences in vertical and horizontal ratios of enlargement, the method comprising the steps of:
   providing an imaging apparatus comprising an X - ray source configured to apply radiation to a radiation receiver spaced apart from the X - ray source by a first distance in a lateral direction and to a radiation receiver spaced apart from the X - ray source by a second distance in the lateral direction, the second distance being greater than the first distance;        the imaging apparatus being capable of operating in a mode in which the X - ray source and the radiation receiver spaced apart from the X - ray source by the first distance are rotated about an intermediate rotation center to provide an image of an object positioned between the X - ray source and the radiation receiver spaced apart from the X - ray source by the first distance;        placing a subject for cephalometric imaging between the X - ray source and the radiation receiver spaced apart from the X - ray source by the second distance; and        taking a cephalometric image of the subject by applying radiation from the X - ray source to the radiation receiver spaced apart from the X - ray source by the second distance and simultaneously translating said rotation center in a direction generally transverse to the lateral direction so as to transfer the effective focal spot of the X - ray source towards the X - ray source in the lateral direction;        wherein the X - ray source remains substantially stationary and the effective focal spot of the X - ray source is transferred to the general location of the X - ray source.     
     
     
       7. The method according to  claim 6 , wherein the imaging apparatus comprises a first radiation receiver spaced apart from the X- ray source by the first distance and a second radiation receiver spaced apart from the X - ray source by the second distance.   
     
     
       8. The method according to  claim 6 , further comprising the step of translating the radiation receiver spaced apart from the X- ray source by the second distance generally transverse to the lateral direction so that the radiation receiver is positioned to continuously receive radiation applied by the X - ray source.   
     
     
       9. The method according to  claim 6 , further comprising the step of operating the imaging apparatus in the first mode by rotating the X- ray source and the radiation sensor spaced apart from the X - ray source by the first distance about the intermediate rotation center to provide an image of the object positioned between the X - ray source and the radiation receiver spaced apart from the X - ray source by the first distance.   
     
     
       10. The method according to  claim 9 , wherein the image of the object is a panoramic image. 
     
     
       11. The method according to  claim 6 , wherein the imaging apparatus comprises a panoramic imaging apparatus configured to also take cephalometric images. 
     
     
       12. The method according to  claim 6 , further comprising the step of collimating the radiation applied to the radiation receiver spaced apart from the X- ray source by the second distance.   
     
     
       13. A method for operating an imaging apparatus to provide improved cephalometric images having reduced differences in vertical and horizontal ratios of enlargement, the method comprising the steps of:
   providing an imaging apparatus extending in three dimensions, including a length dimension, a width dimension that is generally perpendicular to the length dimension, and a height dimension that is generally perpendicular to the length dimension and generally perpendicular to the width dimension;        wherein the imaging apparatus comprises an X - ray source configured to apply radiation in the length dimension to a radiation receiver spaced apart from the X - ray source by a first distance in the length dimension and to a radiation receiver spaced apart from the X - ray source by a second distance in the length dimension, the second distance being greater than the first distance;        the imaging apparatus being capable of operating in a mode in which the X - ray source and the radiation receiver spaced apart from the X - ray source by the first distance are rotated about an intermediate rotation center to provide an image of an object positioned between the X - ray source and the radiation receiver spaced apart from the X - ray source by the first distance;        placing a subject for cephalometric imaging between the X - ray source and the radiation receiver spaced apart from the X - ray source by the second distance; and        taking a cephalometric image of the subject by applying radiation from the X - ray source to the radiation receiver spaced apart from the X - ray source by the second distance and simultaneously translating said rotation center generally in the width dimension so as to transfer the effective focal spot of the X - ray source towards the X - ray source in the length dimension;        wherein the X - ray source remains substantially stationary and the effective focal spot of the X - ray source is transferred to the general location of the X - ray source.     
     
     
       14. The method according to  claim 13 , wherein the imaging apparatus comprises a first radiation receiver spaced apart from the X- ray source by the first distance and the second radiation receiver spaced apart from the X - ray source by the second distance.   
     
     
       15. The method according to  claim 13 , wherein the imaging apparatus comprises a panoramic imaging apparatus configured to also take cephalometric images. 
     
     
       16. The method according to  claim 13 , further comprising the step of translating the radiation receiver spaced apart from the X- ray source by the second distance generally in the width dimension so that the radiation receiver is positioned to continuously receive radiation applied by the X - ray source.   
     
     
       17. The method according to  claim 13 , further comprising the step of operating the imaging apparatus in the first mode by rotating the X- ray source and the radiation sensor spaced apart from the X - ray source by the first distance about the intermediate rotation center to provide an image of the object positioned between the X - ray source and the radiation receiver spaced apart from the X - ray source by the first distance.   
     
     
       18. The method according to  claim 17 , wherein the image of the object is a panoramic image. 
     
     
       19. The method according to  claim 13 , further comprising the step of collimating the radiation applied to the radiation receiver spaced apart from the X- ray source by the second distance.