System and method for learning relative distance in a shape space using image based features

1. A method for populating a database with a set of images of an anatomical structure, the database being used to identify a shape of an anatomical structure in an input image, the method comprising the steps of:

receiving a set of images of anatomical structures, each image being annotated with a plurality of control points that identify a contour of the anatomical structure,

identifying a reference shape for the image set;

calculating a warping template for each image in the image set that warps that image into approximately the reference shape;

creating a matrix of images by applying each warping template calculated for each image in the image set to all of the images in the image set;

computing a shape difference for each image in the matrix by computing a distance measurement between each warped shape and the reference shape;

ranking the images based on the distance measurement;

identifying a set of features associated with the images;

computing feature scores for each image in the matrix;

using a ranking boosting process to selecting those combination of features that result in feature scores that produce a rank that is consistent with the rank associated with the warped image; and

storing the annotated contours of the anatomical structure, warping templates and the selected feature combination in the database.

2. The method of claim 1 wherein the step of computing feature scores for each image in the matrix further comprises the step of:

assigning a weight to each feature.

3. The method of claim 1 wherein the reference shape is the mean shape of all of the anatomical structures in the image set.

4. The method of claim 1 wherein the features are Haar features.

5. The method of claim 1 wherein the anatomical structure is a left ventricle and the shape is the contour of the left ventricle.

6. The method of claim 1 wherein the images are ultrasound images.

7. A method for identifying a shape of an anatomical structure in an input image, the method comprising the steps of:

receiving an input image;

warping the input image using a set of warping templates resulting in a set of warped images;

calculating an integral image for each warped image;

extracting selected features based on the integral image;

calculating a boosted feature score for the combined selected features for each warped image;

ranking the warped images based on the boosted feature scores;

selecting a predetermined number of warped images that have the largest feature scores;

associating each selected warped image with its corresponding warping template;

associating the corresponding warping templates with stored shape models ; and

identifying the shape of the input image based on the weighted average of the shapes models.

8. The method of claim 7 wherein the features are Haar features.

9. The method of claim 7 wherein the anatomical structure is a left ventricle and the shape is the contour of the left ventricle.

10. The method of claim 7 wherein the images are ultrasound images.

11. A system for non-rigid shape detection of an anatomical structure in an image, the system comprising;

a database that stores a set of images of anatomical structures, each image being annotated to indicate a contour of the shape of the anatomical structure, the database also storing selected features and combination weights;

a processor that receives an input image of an anatomical structure, the processor performing the following steps:

warping the input image using a warping template resulting in a set of warped versions of the input image;

calculating an integral image for each warped image;

extracting selected features based on the integral image;

calculating a boosted feature score for the combined selected features for each input warped image;

ranking the warped images based on the boosted feature scores;

selecting a predetermined number of warped images that have the largest feature scores;

associating each selected warped image with its corresponding warping template,

associating the corresponding warping templates with stored shape models;

identifying the shape of the input image based on the weighted average; and

a display to display the identified shape.

12. The system of claim 11 wherein the features are Haar features.

13. The system of claim 11 wherein the anatomical structure is a left ventricle and the shape is the contour of the left ventricle.

14. The system of claim 11 wherein the images are ultrasound images.