Method for automatic construction of 2d statistical shape model for the lung regions

Abstract

A method for automatic construction of 2D statistical shape models for the lung regions in chest radiographic images. The method includes: extracting the anatomical structure contours from a chest radiograph image; generating a polygonal shape approximation for each contour; aligning a plurality of polygonal shape approximations by minimizing their distance; assigning a plurality of landmarks on each shape contour; and determining a statistical shape model using aligned shape contours.

1 . A method for automatic construction of 2D statistical shape models for the lung regions in chest radiographs, comprising: 
 extracting the anatomical structure contours from a chest radiograph image;    generating a polygonal shape approximation for each contour;    aligning a plurality of polygonal shape approximations by minimizing their distance;    assigning a plurality of landmarks on each shape contour; and    determining a statistical shape model using aligned shape contours.    
     
     
         2 . The method of  claim 1 , wherein aligning a plurality of polygonal shape approximations is accomplished by: 
 creating a template shape;    computing a minimal distance and associated transformation parameters between the polygon approximations of the template shape and a shape instance; and    transforming the shape instance based on the transformation parameters.    
     
     
         3 . The method of  claim 2 , wherein computing the minimal distance is accomplished by: 
 computing turning functions of polygon approximations of a shape instance and the template shape; and    transforming the turning function of the shape instance to search the minimal distance between the turning function of the shape instance and the turning function of the template shape; and    determining the transformation parameters using the minimal distance.    
     
     
         4 . The method of  claim 2 , wherein the computing the minimal distance is accomplished by: 
 choosing predetermined polygon vertices with salient shape features as landmarks;    assigning a plurality of landmarks between the located landmarks using the shape contour;    computing the minimal distance between the shape instance and the template shape using the landmarks; and    determining the transformation parameters using the minimal distance.    
     
     
         5 . The method of  claim 4 , wherein assigning a plurality of landmarks between the located landmarks comprises locating a fixed number of equidistant points between the located landmarks.  
     
     
         6 . The method of  claim 4 , wherein computing the minimal distance is accomplished by: 
 computing the minimal distance and associated transformation parameters between the polygon approximations of the template shape and a shape instance;    transforming the shape instance based on the transformation parameters; and    minimizing the weighted sum of distances between the corresponding landmarks of the template and the shape instance.    
     
     
         7 . The method of  claim 4 , wherein the minimal distance is computed by minimizing the weighted sum of distances between the corresponding landmarks.  
     
     
         8 . The method of  claim 7 , wherein the weights are chosen to give more significance to the landmarks associated with salient shape features.  
     
     
         9 . The method of  claim 1 , wherein assigning a plurality of landmarks on shape contours comprises: 
 choosing a certain polygon vertices with salient shape features as landmarks; and    assigning a plurality of landmarks between the located landmarks using the aligned shape contour;    
     
     
         10 . The method of  claim 9 , wherein assigning a plurality of landmarks between the located landmarks comprises locating a fixed number of equidistant points between the located landmarks.  
     
     
         11 . The method of  claim 1 , wherein the statistical model is determined according to a principle component analysis.  
     
     
         12 . A method for automatic construction of 2D statistical shape models for an anatomical structure, comprising: 
 extracting the anatomical structure contours from a radiograph image;    generating a polygonal shape approximation for each contour;    aligning a plurality of polygonal shape approximations by minimizing their distance;    assigning a plurality of landmarks on each shape contour; and    determining a statistical shape model using aligned shape contours.