Method for recognizing the contour of an irradiation field

Claim 1

A method for recognizing an irradiation field wherein an image signal comprising a plurality of image signal components corresponding to picture elements on a recording medium, on which a radiation image of an object has been recorded, is obtained, and an irradiation field on the recording medium is recognized on the basis of the image signal components, wherein the improvement comprises the steps of: i) on each of a plurality of radial lines each of which connects a predetermined point located in the region inside of said irradiation field on said recording medium with an edge of said recording medium, detecting a single prospective contour point, which is considered to be an intersection of each said line and a contour of said irradiation field on said recording medium, or a plurality of such prospective contour points, together with prospectiveness ranks of the prospective contour points, on the basis of the image signal components corresponding to the picture elements arrayed along each said line, ii) in cases where said prospective contour points detected on each said line are present in both a predetermined peripheral region close to the edge of said recording medium and a center region on the inward side of said peripheral region, and a prospective contour point standing in the first prospectiveness rank is present in said peripheral region, changing the prospectiveness ranks of said prospective contour points so that the first prospectiveness rank is given to a prospective contour point which is in the highest rank among the prospective contour points located in said center region, and iii) recognizing said irradiation field on the basis of the first-ranking prospective contour points which are thus determined on said lines.

Claim 2

A method for recognizing an irradiation field wherein an image signal comprising a plurality of image signal components corresponding to picture elements on a recording medium, on which a radiation image of an object has been recorded, is obtained, and an irradiation field on the recording medium is recognized on the basis of the image signal components, wherein the improvement comprises the steps of: i) on each of a plurality of radial lines each of which connects a predetermined point located in the region inside of said irradiation field on said recording medium with an edge of said recording medium, detecting a single prospective contour point, which is considered to be an intersection of each said line and a contour of said irradiation field on said recording medium, or a plurality of such prospective contour points, together with prospectiveness ranks of the prospective contour points, on the basis of the image signal components corresponding to the picture elements arrayed along each said line, ii) in cases where said prospective contour points detected on each said line are present in both a predetermined peripheral region close to the edge of said recording medium and a center region on the inward side of said peripheral region, and a prospective contour point standing in the first prospectiveness rank is present in said peripheral region, changing the prospectiveness ranks of said prospective contour points so that the first prospectiveness rank is given to a prospective contour point which is in the highest rank among the prospective contour points located in said center region, and iii) recognizing said irradiation field on the basis of the first-ranking prospective contour points which are thus determined on said lines.

Claim 4

A method for judging the correctness or incorrectness of a prospective contour point of an irradiation field, which comprises the steps of, after image read out from a recording medium, on which a radiation image of an object has been recorded, is carried out in order to obtain an image signal comprising a plurality of image signal components corresponding to picture elements on the recording medium: i) on a line which connects a predetermined point located in the region inside of an irradiation field on said recording medium with an edge of said recording medium, detecting prospective contour points, each of which is considered to be an intersection of said line and a contour of said irradiation field, on the basis of the image signal components corresponding to the picture elements arrayed along said line, ii) detecting a change point of said image signal components arrayed along said line, which change point arises characteristically only in the region inside of said irradiation field, and iii) in cases where said change point has been detected, judging that a prospective contour point located on the predetermined point side of said change point is not present on the contour of said irradiation field and is thus incorrect.

Claim 5

A method for judging the correctness or incorrectness of a prospective contour point of an irradiation field, which comprises the steps of, after image read out from a recording medium, on which a radiation image of an object has been recorded, is carried out in order to obtain an image signal comprising a plurality of image signal components corresponding to picture elements on the recording medium: i) on a line which connects a predetermined point located in the region inside of an irradiation field on said recording medium with an edge of said recording medium, detecting prospective contour points, each of which is considered to be an intersection of said line and a contour of said irradiation field, on the basis of the image signal components corresponding to the picture elements arrayed along said line, ii) detecting a change point of said image signal components arrayed along said line, which change point arises characteristically only in the region inside of said irradiation field, and iii) in cases where said change point has been detected, judging that a prospective contour point located on the predetermined point side of said change point is not present on the contour of said irradiation field and is thus incorrect.

Claim 7

A method for judging the correctness or incorrectness of a prospective contour point of an irradiation field, which comprises the steps of, after image read out from a recording medium, on which a radiation image of an object has been recorded, is carried out in order to obtain an image signal comprising a plurality of image signal components corresponding to picture elements on the recording medium: i) on a line which connects a predetermined point located in the region inside of an irradiation field on said recording medium with an edge of said recording medium, detecting a prospective contour point, which is considered to be an intersection of said line and a contour of said irradiation field, on the basis of the image signal components corresponding to the picture elements arrayed along said line, ii) in cases where said prospective contour point has been detected, calculating a characteristic value of the image signal components corresponding to the picture elements arrayed along a single line or along each of a plurality of lines, each of which line extends from said prospective contour point to the direction that goes away from said predetermined point, iii) comparing said characteristic value with a predetermined value, and iv) based on the results of the comparison of said characteristic value with said predetermined value, judging whether said prospective contour point is truly present on the contour of said irradiation field or is not present on the contour of said irradiation field and is thus incorrect.

Claim 8

A method for judging the correctness or incorrectness of a prospective contour point of an irradiation field, which comprises the steps of, after image read out from a recording medium, on which a radiation image of an object has been recorded, is carried out in order to obtain an image signal comprising a plurality of image signal components corresponding to picture elements on the recording medium: i) on a line which connects a predetermined point located in the region inside of an irradiation field on said recording medium with an edge of said recording medium, detecting a prospective contour point, which is considered to be an intersection of said line and a contour of said irradiation field, on the basis of the image signal components corresponding to the picture elements arrayed along said line, ii) in cases where said prospective contour point has been detected, calculating a characteristic value of the image signal components corresponding to the picture elements arrayed along a single line or along each of a plurality of lines, each of which line extends from said prospective contour point to the direction that goes away from said predetermined point, iii) comparing said characteristic value with a predetermined value, and iv) based on the results of the comparison of said characteristic value with said predetermined value, judging whether said prospective contour point is truly present on the contour of said irradiation field or is not present on the contour of said irradiation field and is thus incorrect.