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Automatic background recognition and removal (ABRR) in projection digital radiographic images (PDRI)

  • US 5,903,660 A
  • Filed: 07/16/1997
  • Issued: 05/11/1999
  • Est. Priority Date: 07/16/1997
  • Status: Expired due to Fees
First Claim
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1. An automatic background recognition and removal process for removing background signals, caused by collimation during projection, from projection digital radiographic images (PDRI), with a PDRI comprising a set of image pixels, each encoding an image value and identified by a set of (x,y) coordinates, said method comprising the steps of:

  • scanning a set of lines of said image to identify an edge candidate pixel in each line scanned having an image value which varies in value from the image value of a neighbor pixel by at least a first threshold value;

    collecting said candidate pixels into a first set of edge candidate pixels;

    calculating a background score value for each edge candidate pixel in said first set, with a higher background score indicating a higher probability that a pixel is located in the background;

    filtering said first set to discard all edge candidate pixels having a calculated background score value less than a probability threshold value from said first set to form a second edge set of edge candidate pixels;

    determining which edge candidate pixels in said second set of edge candidate pixels are not located on an edge of two image areas of different intensity;

    filtering said second set to discard all edge candidate pixels in the second set which are not on an image edge to form a third set of edge candidate pixels;

    adaptively determining an edge probability threshold value for the number of pixels in said third edge pixel set based on a calculated value of background score of a side of the image nearest to the edge, with said threshold value increased if the calculated value is small and decreased if the calculated value is large;

    fitting a line to the pixels in said third edge pixel set if the number of pixels in said set is greater than the edge probability threshold value adaptively determined for the third set; and

    performing background removal of all pixels outside the image edge determined by the line.

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