US 6,212,291 B1Granted

Method for recognizing multiple irradiation fields in digital radiography

AssigneeEastman Kodak Company

InventorsXiaohui Wang, Jiebo Luo, Robert A. Senn

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Abstract

A method of processing a digital radiographic image comprising the steps of: providing a digital radiographic image having a plurality of radiation fields and collimation regions defined by collimation blades at least partially bounding the radiation fields; detecting and classifying pixels of the digital radiographic image as collimation boundary transition pixels; line-level delineating of a plurality of candidate collimation blades from the collimation boundary transition pixels; estimating the most likely partitioning; and determining at a region level the radiation field from the results of the partitioning estimating step.

Claims23

Dependent claims

A method of processing a digital radiographic image comprising the steps of:

providing a digital radiographic image having a plurality of radiation fields and collimation regions defined by collimation blades at least partially bounding said radiation fields;
detecting and classifying pixels of said digital radiographic image as collimation boundary transition pixels using smart edge detection based on a classifier and a prior knowledge of the collimation process;
line-level delineating of a plurality of candidate collimation blades from said collimation boundary transition pixels modeled as step edges with polarity from said collimation boundary transition pixels;
determining a plurality of candidate partition blade pairs from a list of said candidate collimation blades includes using a multiple-pass method;
determining at a region level the radiation field from the results of said determining step;
wherein said determining step includes the steps of:
sorting said candidate partition blade pairs in to a list of such an order that said radiographic image can be continuously and recursively partitioned;
partitioning said radiographic image into a simple sub-image and a compound sub-image using the most likely partition blade pair on the said list, and taking said pair off said list thereafter;
repeating said partitioning process for said compound sub-image using the remaining partition blade pairs on said list;
and
collecting candidate collimation blades that belong to each valid said simple sub-image;
wherein said step of determining a plurality of candidate partition blade pairs from a list of said candidate collimation blades includes using a multiple-pass method of the following steps:
the first pass is a process of rule-based decision to identify all the possible combinations of candidate collimation blades that can construct a partition blade pair, including, in terms of rules, a blade pair should (i) have an intersection angle less than a predefined value, (ii) have opposite polarities, (iii) have the dominant part of either blade relative to the other blade on the side opposite to the polarity of the other blade, etc. If two pairs, e.g., (A,B) and (A,C), share the same blade A, and, B and C are linearly coherent, these two pairs are merged into one;
the second pass is a process of fuzzy score-based evidence accumulation to rank the likelihood of the candidate partition blade pairs including, in terms of fuzzy scores, a partition blade pair (i) should not be too close to the image borders, (ii) should have comparable lengths, (iii) should be present next to each other, (iv) should be nearly parallel, (v) should not be too far apart relative to the dimensions of said radiographic image, (vi) should have large spatial extent relative to the dimensions of said radiographic image, (vii) should be well composed, (viii) should have no significant direct exposure region or modulated region within the gap formed by the candidate partition blade pair in the cases of disconnected and minor overlapping radiation fields, or should have significant direct exposure region within the gap in the cases of major overlapping radiation fields, (ix) should have the dominant part of each blade on the outer side relative to the other blade according to the polarity of the other blade in the cases of disconnected and minor overlapping radiation fields, or should have the dominant part of each blade on the inner side relative to the other blade according to the polarity of the other blade in the case of major overlapping radiation fields;
and
the third pass is a process to select best partition blade pairs such that (1) only the best pair, in terms of the largest overall combined figure-of-merit, is selected among those that share a common partition blade, (2) only the better pair, in terms of the largest overall combined figure-of-merit, is selected if two pairs are too close to each other, (3) both pairs are rejected if majority of either of the blades in either pair falls within the gap formed by extending the candidate blades of the other pair to the borders of said radiographic image or said compound image, whichever applies, (4) only the inner pair is retained if majority of both of the blades in either pair falls within the gap formed by extending the candidate blades of the other pair to the borders of said radiographic image or said compound image, whichever applies.

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Dependencies are inferred from the claim text.

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Abstract

A method of processing a digital radiographic image comprising the steps of:

providing a digital radiographic image having a plurality of radiation fields and collimation regions defined by collimation blades at least partially bounding said radiation fields;
detecting and classifying pixels of said digital radiographic image as collimation boundary transition pixels using smart edge detection based on a classifier and a prior knowledge of the collimation process;
line-level delineating of a plurality of candidate collimation blades from said collimation boundary transition pixels modeled as step edges with polarity from said collimation boundary transition pixels;
determining a plurality of candidate partition blade pairs from a list of said candidate collimation blades includes using a multiple-pass method;
determining at a region level the radiation field from the results of said determining step;
wherein said determining step includes the steps of:
sorting said candidate partition blade pairs in to a list of such an order that said radiographic image can be continuously and recursively partitioned;
partitioning said radiographic image into a simple sub-image and a compound sub-image using the most likely partition blade pair on the said list, and taking said pair off said list thereafter;
repeating said partitioning process for said compound sub-image using the remaining partition blade pairs on said list;
and
collecting candidate collimation blades that belong to each valid said simple sub-image;
wherein said step of determining a plurality of candidate partition blade pairs from a list of said candidate collimation blades includes using a multiple-pass method of the following steps:
the first pass is a process of rule-based decision to identify all the possible combinations of candidate collimation blades that can construct a partition blade pair, including, in terms of rules, a blade pair should (i) have an intersection angle less than a predefined value, (ii) have opposite polarities, (iii) have the dominant part of either blade relative to the other blade on the side opposite to the polarity of the other blade, etc. If two pairs, e.g., (A,B) and (A,C), share the same blade A, and, B and C are linearly coherent, these two pairs are merged into one;
the second pass is a process of fuzzy score-based evidence accumulation to rank the likelihood of the candidate partition blade pairs including, in terms of fuzzy scores, a partition blade pair (i) should not be too close to the image borders, (ii) should have comparable lengths, (iii) should be present next to each other, (iv) should be nearly parallel, (v) should not be too far apart relative to the dimensions of said radiographic image, (vi) should have large spatial extent relative to the dimensions of said radiographic image, (vii) should be well composed, (viii) should have no significant direct exposure region or modulated region within the gap formed by the candidate partition blade pair in the cases of disconnected and minor overlapping radiation fields, or should have significant direct exposure region within the gap in the cases of major overlapping radiation fields, (ix) should have the dominant part of each blade on the outer side relative to the other blade according to the polarity of the other blade in the cases of disconnected and minor overlapping radiation fields, or should have the dominant part of each blade on the inner side relative to the other blade according to the polarity of the other blade in the case of major overlapping radiation fields;
and
the third pass is a process to select best partition blade pairs such that (1) only the best pair, in terms of the largest overall combined figure-of-merit, is selected among those that share a common partition blade, (2) only the better pair, in terms of the largest overall combined figure-of-merit, is selected if two pairs are too close to each other, (3) both pairs are rejected if majority of either of the blades in either pair falls within the gap formed by extending the candidate blades of the other pair to the borders of said radiographic image or said compound image, whichever applies, (4) only the inner pair is retained if majority of both of the blades in either pair falls within the gap formed by extending the candidate blades of the other pair to the borders of said radiographic image or said compound image, whichever applies.

13 more elements