Method and Device for Creating a Cephalometric Image

Abstract

An extra-oral dental imaging system comprises an X-ray source ( 102 ) and an imaging device ( 101 ) suitable for producing multiple frames during at least part of an exposure of an object ( 200 ), the imaging device ( 101 ) being displaced along a scanning direction (X). A method for creating a cephalometric image of a human skull comprises a step of setting said imaging device ( 101 ) with an active area having in an imaging plane a width extending along said scanning direction (X), said width varying along a height direction perpendicular to said scanning direction (X); a step of synchronously displacing the X-ray source ( 102 ) and the imaging device ( 101 ) along said exposure profile; and a step of registering multiple frames produced by the imaging device ( 101 ) during the exposure of said object ( 200 ) to be imaged. Using for creating a cephalometric image by digital tomosynthesis.

1 . A method for creating a cephalometric image of at least part of a human skull in an extra-oral dental imaging system, said system comprising:
 an X-ray source for irradiating an object to be imaged;   an imaging device suitable for producing multiple frames during at least part of an exposure of said object;   a manipulator for displacing the imaging device along an exposure profile between multiple frames during said at least part of the exposure of said object, the manipulator permitting the movement of the imaging device along a scanning direction (X),   characterized in that said method comprises the following steps:
 setting said imaging device with an active area having in an imaging plane a width, extending along said scanning direction (X), said width varying along a height direction (Y) perpendicular to said scanning direction (X); 
 synchronously displacing the X-ray source and the imaging device along said exposure profile; and 
 registering said multiple frames produced by the imaging device during the exposure of said object to be imaged. 
   
     
     
         2 . A method according to  claim 1 , wherein said active area is symmetric in said imaging plane, with a central axis extending along said height direction (Y) of said active area. 
     
     
         3 . A method according to  claim 1 , wherein said active area has at least two portions having widths different from each other, said two portions being superposed in said imaging plane along said height direction (Y). 
     
     
         4 . A method according to  claim 3 , wherein the height of said active area is between 120 mm and 280 mm, the width of a first portion is between 2 mm and 50 mm, and the width of a second portion is between 50 and 140 mm. 
     
     
         5 . A method according to  claim 1 , wherein said active area has at least three portions with respectively three different widths. 
     
     
         6 . A method according to  claim 1 , wherein said active area has a central portion, a lower portion, and an upper portion each extending along said height direction (Y) in said imaging plane, the width of the central portion is larger than the width of the lower portion and the width of the lower portion is larger than the width of the upper portion. 
     
     
         7 . A method according to  claim 1 , further comprising a step of computing said multiple frames produced during at least one part of the exposure:
 by a shift-and-add processing, thereby reconstructing at least one slice; or   by a volumetric approach, thereby reconstructing a three-dimensional volume and subsequently extracting at least one slice from this volume;   wherein said at least one slice includes in-focus imaging data belonging respectively to at least one depth of said object to be imaged.   
     
     
         8 . A method according to  claim 7 , wherein the volumetric approach is selected from a Statistical Algebraic Reconstruction Technique (SART), a Statistical Iterative Reconstruction Technique (SIRT), or a Filtered Back Projection technique. 
     
     
         9 . A method according to  claim 7 , further comprising a step of using each reconstructed slice for the extraction of cephalometric features. 
     
     
         10 . A method according to  claim 9 , further comprising a step of automatic cephalometric tracing, wherein said extracted cephalometric features of each slice are put together. 
     
     
         11 . A method according to  claim 9 , wherein several slices are reconstructed and combined to give a separate linear projection for the left and right sides of said object to be imaged. 
     
     
         12 . A method according to  claim 7 , wherein several slices are reconstructed and retro projected to a distance superior to 1.50 meters, and preferably superior to 4 meters, on a cone beam or parallel geometry so as to create a synthesized 2D cephalogram of the skull. 
     
     
         13 . A method according to  claim 1 , comprising the following steps:
 synchronously displacing the X-ray source and the imaging device along a first part of said exposure profile, said X-ray source being in an upper position along said height direction (Y);   registering said multiple frames produced by the imaging device during said first part of the exposure profile;   synchronously displacing the X-ray source and the imaging device along a second part of said exposure profile, said X-ray source being in a lower position along said height direction (Y);   registering said multiple frames produced by the imaging device during said second part of the exposure profile; and   combining said multiple frames registered during said first and second parts of the exposure profile.   
     
     
         14 . An extra-oral dental imaging system for creating a cephalometric image of at least part of a human skull, such system comprising:
 an X-ray source for irradiating an object to be imaged;   an imaging device suitable for producing multiple frames during at least part of an exposure of said object;   manipulator for displacing the imaging device along an exposure profile between multiple frames during said at least part of the exposure of said object, the manipulator permitting the movement of the imaging device along a scanning direction (X),
 characterized in that said imaging device has an active area having in an imaging plane a width extending along said scanning direction (X), said width varying along a height direction (Y) perpendicular to said scanning direction (X); and in that said manipulator synchronously displaces the X-ray source and the imaging device along said exposure profile; and in that it comprises memory for registering said multiple frames produced by the imaging device during the exposure of said object to be imaged.