Multi-pass edge detection of collimator blades in digital radiography images
View Patent ↗A process for detecting the edges of collimator blades in digital radiography images in the first pass detects the edges of the collimator blades using original image, and the in the second pass repeats edge detection using an image enhanced by a histogram matching technique, for example. The edge detection using an enhanced image may also be repeated any number of times in cases of complex anatomy or when selected radiographic techniques does do not provide sufficient imaging data. The results of the second pass, or the collection of the results of multiple second passes, are then combined with the result from the first pass to form a list of the potential blade edge candidates. A desirable number of edges are then selected from the combined list to form a polygon which encloses the target area of the image, thereby providing the shutter area.
1. A method for detecting collimator blade edges in a digital radiography image, comprising:
performing a first detection pass of said image to generate a first list of detected edges;
enhancing said image;
performing a second detection pass of said enhanced image to generate a second list of detected edges;
combining said first list and said second list to generate a combined edge list;
validating a plurality of the detected edges in said combined edge list; and
selecting a predetermined number of validated edges.
2. The method of claim 1 , wherein the act of enhancing the image comprises modifying pixel values of said image according to a predetermined histogram transformation.
3. The method of claim 2 , wherein said first list of detected edges and said second list of detected edges are stored in memory prior to said act of combining said first list and second list to generate the combined edge list.
4. The method of claim 1 , wherein said predetermined number of validated edges comprises four to eight.
5. The method of claim 1 , wherein the act of performing the second detection pass and the act of combining are repeated at least once.
6. The method of claim 1 , wherein said first detection pass is accomplished using a Hough transform.
7. The method of claim 1 , further comprising enclosing a shutter area in said image by providing a polygon based on the predetermined number of validated edges.
8. A non-transitory computer readable medium including program instructions for detecting collimator blade edges in a digital radiography image which when executed perform a method comprising:
performing a first detection pass of said image to generate a first list of detected edges;
enhancing said image;
performing a second detection pass of said enhanced image to generate a second list of detected edges;
combining said first list and said second list to generate a combined edge list;
validating a plurality of the detected edges in said combined edge list; and
selecting a predetermined number of validated edges.
9. The computer readable medium of claim 8 , wherein said act of performing said first detection pass comprises using a Hough transform.
10. The computer readable medium of claim 9 , further comprising performing a third detection pass to generate a third list of detected edges.
11. The computer readable medium of claim 8 , wherein said predetermined number of validated edges comprises four to eight.
12. The computer readable medium of claim 8 , wherein said act of enhancing said image comprises modifying pixel values of said image according to a predetermined histogram transformation.
13. An apparatus for detecting collimator blade edges in a digital radiography image, comprising:
a processing unit configured for:
performing a first detection pass of said image to generate a first list of detected edges;
enhancing said image;
performing a second detection pass of said enhanced image to generate a second list of detected edges;
combining said first list and said second list to generate a combined edge list; and
validating a plurality of the detected edges in said combined edge list.
14. The apparatus of claim 13 , wherein the processing unit is configured to enhance the image by modifying pixel values of the image according to a predetermined histogram transformation.
15. The apparatus of claim 14 , further comprising a memory for storing the first list of detected edges and the second list of detected edges.
16. The apparatus of claim 13 , wherein the processing unit is further configured for selecting a predetermined number of validated edges.
17. The apparatus of claim 13 , wherein the processing unit is configured to repeat the act of performing the second detection pass and the act of combining at least once.
18. The apparatus of claim 13 , wherein the processing unit is configured to perform the first detection pass using a Hough transform.
19. The apparatus of claim 13 , wherein the processing unit is further configured for enclosing a shutter area in the image by providing a polygon based on a predetermined number of validated edges.