Method and Device for Creating a Cephalometric Image

Abstract

Extra-oral dental method and/or apparatus embodiments according to this application can generate cephalometric imaged by digital tomosynthesis. An extra-oral dental imaging system embodiment for creating a cephalometric image of at least part of a human skull can include an X-ray source, an imaging device suitable for producing multiple frames during at least part of an exposure; a memory for registering and/or storing said multiple frames; and 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 imaging device has an active area having a long dimension m and a short dimension n, wherein the aspect ratio m:n is strictly inferior to 1.5.

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 X-ray source and the imaging device by means of a selective translation and selective rotation,   characterized in that said method comprises the following steps:   setting said imaging device with an active area having a long dimension m and a short dimension n, wherein the aspect ratio m:n is strictly inferior to 1.5;   synchronously displacing the X-ray source and the imaging device along said exposure profile, said exposure profile comprising at least one substantially linear section wherein said X-ray source and said imaging device are translated while rotating in the same direction; 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 the at least one substantially linear section of the exposure profile is oriented parallel to a mid-sagittal plane or a coronal plane, or angled to said mid-sagittal plane. 
     
     
         3 . A method according to  claim 1 , wherein said exposure profile comprises at least two separate substantially linear sections at two opposite angular extremes about the object to be imaged. 
     
     
         4 . A method according to  claim 1 , wherein said short dimension n of the active area of the imaging device extends along said at least one substantially linear section during the exposure of said object. 
     
     
         5 . A method according to  claim 1 , wherein the angular range (θ) of the rotational movement of the imaging device and the X-ray source is at least equal to 15°, and preferably equal to 30°. 
     
     
         6 . A method according to  claim 1 , wherein the X-ray source is displaced along a trajectory having a curvature directed towards said object, and the imaging device is displaced along a trajectory having a curvature directed away from said object. 
     
     
         7 . A method according to  claim 1 , wherein the length of said at least one substantially linear section is comprised between 70 and 250 mm. 
     
     
         8 . A method according to  claim 1 , wherein said aspect ratio m:n is inferior to 1.3, and most preferably inferior to 1.2. 
     
     
         9 . A method according to  claim 1 , wherein the long dimension m of said active area is equal to 140 mm and the short dimension n of said active area is equal to 120 mm. 
     
     
         10 . A method according to  claim 1 , wherein the long dimension m of said active area is equal to 210 mm and the short dimension n of said active area is equal to 150 mm. 
     
     
         11 . 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.   
     
     
         12 . The method according to  claim 11 , 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. 
     
     
         13 . A method according to  claim 11 , further comprising a step of using each reconstructed slice for the extraction of cephalometric features. 
     
     
         14 . A method according to  claim 13 , further comprising a step of automatic cephalometric tracing, wherein said extracted cephalometric features of each slice are put together. 
     
     
         15 . A method according to  claim 11 , wherein said several slices are reconstructed and combined to give a separate linear projection for the left and right sides of said object to be imaged. 
     
     
         16 . A method according to  claim 11 , wherein said 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. 
     
     
         17 . 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 X-ray source and the imaging device by means of selective translation and selective rotation,
 characterized in that said imaging device has an active area having a long dimension m and a short dimension n, wherein the aspect ratio m:n is strictly inferior to 1.5; and in that said manipulator synchronously displaces the X-ray source and the imaging device along said exposure profile, said exposure profile comprising at least one substantially linear section wherein said X-ray source and said imaging device are translated while rotating in the same direction; 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.