METHOD FOR AUTOMATIC CONSTRUCTION OF 2D STATISTICAL SHAPE MODEL FOR THE LUNG REGIONS

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.