Edge boundary definition for radiographic detector

1. A method for defining edge boundaries of an image formed on a flat-panel radiographic detector, comprising:

obtaining digital image pixel values from the radiographic detector;

obtaining dimensional information about a collimator in the radiographic signal path;

analyzing the image to detect one or more collimator blade edges; and

processing the digital image pixel values at least once to detect remaining collimator blade edges by:

(i) accumulating image pixel values along each of a plurality of lines in a first direction parallel to a first vector, determined by the orientation of a detected collimator blade edge, that extends across the image, to obtain a first profile value for each line in said first direction, thereby forming an ordered set of first profile values; and

(ii) identifying first and second threshold values in the set of first profile values, wherein the paired first and second threshold values indicate an edge boundary corresponding to a collimator blade projection along the first direction.

2. The method of claim 1 wherein processing the digital image pixel values at least once further comprises the steps:

(iii) accumulating image pixel values along each of a plurality of lines in a second direction perpendicular to the first vector, to obtain a second profile value for each line in said second direction, thereby forming an ordered set of second profile values; and

(iv) identifying third and fourth threshold values in the set of second profile values, wherein the paired third and fourth threshold values indicate an edge boundary corresponding to a collimator blade projection along the second direction.

3. The method of claim 2 further comprising applying a black surround to that portion of the image that lies outside each detected edge boundary.

4. The method of claim 1 wherein processing the digital image pixel values further comprises:

obtaining measurement data about the collimator; and

testing the first edge boundary against a calculated dimensional limit for collimator blade projection according to the measurement data.

5. A method for defining an image formed on a flat-panel radiographic detector, comprising:

obtaining digital image pixel values from the radiographic detector;

computing a maximum image size according to collimator opening dimensions and the source-to-image distance;

analyzing the image to detect one or more collimator blade edges;

processing the digital image pixel values one or more times by:

(i) accumulating image pixel values along each of a plurality of lines in a first direction parallel to a first vector, determined by the orientation of a detected collimator blade edge, that extends across the image, to obtain a first profile value for each line in said first direction, thereby forming an ordered set of first profile values;

(ii) identifying first and second threshold values in the set of first profile values, wherein the paired first and second threshold values indicate an edge boundary corresponding to a collimator blade projection along the first direction;

(iii) accumulating image pixel values along each of a plurality of lines in a second direction perpendicular to the first vector to obtain a second profile value for each line in said second direction, thereby forming an ordered set of second profile values; and

(iv) identifying third and fourth threshold values in the set of second profile values, wherein the paired third and fourth threshold values indicate an edge boundary corresponding to a collimator blade projection along the second direction; and

defining the image boundary according to the edge boundaries obtained.

6. A method for defining an image formed on a flat-panel radiographic detector, comprising:

obtaining digital image pixel values from the radiographic detector;

obtaining a signal indicative of at least one dimension of a collimator opening;

analyzing the image to detect one or more collimator blade edges;

processing the digital image pixel values one or more times by:

(i) accumulating image pixel values along each of a plurality of lines in a first direction parallel to a first vector, determined by the orientation of a detected collimator blade edge, that extends across the image, to obtain a first profile value for each line in said first direction, thereby forming an ordered set of first profile values;

(ii) identifying first and second threshold values in the set of first profile values, wherein the paired first and second threshold values indicate an edge boundary corresponding to a collimator blade projection along the first direction;

(iii) accumulating image pixel values along each of a plurality of lines in a second direction perpendicular to the first vector to obtain a second profile value for each line in said second direction, thereby forming an ordered set of second profile values; and

(iv) identifying third and fourth threshold values in the set of second profile values, wherein the paired third and fourth threshold values indicate an edge boundary corresponding to a collimator blade projection along the second direction;

comparing the at least one dimension of the collimator opening with a computed distance between parallel edge boundaries identified in step (c);

defining the image boundary according to the edge boundaries obtained; and

applying a black surround to areas lying outside the defined image boundary.