Method for adjusting positions of radiation images

• US 5,623,560 A
• Filed: 07/25/1995
• Issued: 04/22/1997
• Est. Priority Date: 11/27/1992
• Status: Expired due to Term

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Ezuka, Daigo, Nakajima, Nobuyoshi
• Primary Examiner(s): Couso, Jose L.
• Application Number:
  US08/507,022
• Time in Patent Office: 637 Days
• Field of Search: 382/295, 382/296, 382/128, 382/130, 382/132, 382/144, 382/151, 382/263, 382/288, 364/413.13, 364/413.14, 364/413.15, 364/413.22, 364/413.23
• US Class Current: 382/295
• CPC Class Codes: G06T 2207/10116 X-ray image
• CPC Class Codes: G06T 2207/30061 Lung
• CPC Class Codes: G06T 7/337 involving reference images or patches
• CPC Class Codes: G06V 10/7515 Shifting the patterns to accommodate for positional errors

Abstract

Reference regions are set in a radiation image, which serves as a reference among a plurality of radiation images, and template regions are set in the other radiation images. An orthogonal coordinate system is defined on each of the plurality of the radiation images. First template matching is carried out in order to match the template regions to the reference regions. Factors of affine transformation are calculated, and first affine transformation is carried out, with which at least the correction with a rotating operation and the correction with an enlargement or reduction factor are carried out on the radiation images containing the template regions. Second template matching is then carried out on the radiation images, which have been obtained from the first affine transformation. The factors of affine transformation are calculated, and second affine transformation is then carried out, with which the correction with the rotating operation, the correction with the enlargement or reduction factor, and the correction with a parallel translation are carried out on the radiation images containing the template regions.

Claims

1. A method for adjusting positions of radiation images, wherein the positions of a plurality of radiation images are matched to one another such that the radiation images may be subjected to superposition processing or subtraction processing,

the method comprising the steps of:

i) setting at least two regions of interest in each of the radiation images, such that each region of interest in each radiation image is approximately common to a region of interest in each of the other radiation images, the regions of interest in a radiation image which serves as a reference among the radiation images being taken as reference regions, the regions of interest in the other radiation images being taken as template regions,

ii) defining an orthogonal coordinate system on each of the radiation images,

iii) carrying out a first template matching in order to match the template regions to corresponding reference regions,

iv) calculating values of coordinates of corresponding points in the plurality of the radiation images, at least two corresponding points being taken in each of the radiation images,

v) calculating factors of a first affine transformation for transforming values of coordinates in the radiation images which contain the template regions, into values of coordinates in the radiation image which contains the reference regions, such that said corresponding points in the plurality of the radiation images may coincide with one another, said affine transformation being represented by the formula ##EQU5## wherein u and v represent the coordinates of the reference region, x and y represents the coordinates of the specific region, a, b, c, and d are the factors representing correction with a rotating operation and correction with an enlargement or reduction factor, and e and f are the factors representing correction with parallel translation,

vi) carrying out said first affine transformation, in which the calculated factors of said first affine transformation are used and in which at least the correction with the rotating operation and the correction with the enlargement or reduction factor are carried out on the radiation images containing the template regions,

vii) carrying out a second template matching on the radiation images which have been obtained from the first affine transformation,

viii) calculating the factors of a second affine transformation, which is represented by said formula, and

ix) carrying out said second affine transformation, in which the factors of said second affine transformation having been calculated after the second template matching are used, and in which the correction with the rotating operation, the correction with the enlargement or reduction factor, and the correction with the parallel translation are carried out on the radiation images containing the template regions.

2. A method as defined in claim 1 wherein the first affine transformation is repeated a plurality of times.

3. A method as defined in claim 1 wherein each of the radiation images, the positions of which are to be adjusted, has been stored on a stimulable phosphor sheet.

4. A method as defined in claim 1 wherein the first template matching and the second template matching are carried out with a correlation method.

5. A method as defined in claim 1 wherein the first template matching and the second template matching are carried out with sequential similarity detection algorithms.

6. A method for adjusting positions of radiation images, wherein the positions of a plurality of radiation images are matched to one another such that the radiation images may be subjected to superposition processing or subtraction processing,

the method comprising the steps of:

i) setting at least two closed regions in each of the plurality of the radiation images, such that the closed regions have approximately identical shapes among the plurality of the radiation images,

ii) identifying a center of gravity position for each of the closed regions, and

iii) carrying out a rotating operation, enlargement or reduction, and parallel translation of each of the radiation images other than a radiation image which serves as a reference among the plurality of the radiation images, such that the coordinates of said center of gravity positions in each of said other radiation images may coincide with the corresponding coordinates of said center of gravity positions in the radiation image serving as the reference.

7. A method as defined in claim 6 wherein each of the radiation images, the positions of which are to be adjusted, has been stored on a stimulable phosphor sheet.

8. A method as defined in claim 6 wherein the center of gravity positions are each identified by obtaining an image signal comprising image signal components representing image information at respective picture elements located in each closed region, and weighting the respective picture elements with image signal values corresponding to the respective picture elements or with the reciprocals of the image signal values.

9. A method for adjusting positions of radiation images, wherein the positions of a plurality of radiation images are matched to one another such that the radiation images may be subjected to superposition processing or subtraction processing,

the method comprising the steps of:

i ) setting at least two closed regions in each of the plurality of the radiation images, such that the closed regions have approximately identical shapes among the radiation images,

ii) defining an orthogonal coordinate system on each of the radiation images,

iii) identifying a center of gravity position for each of the closed regions,

iv) calculating factors of a first affine transformation for transforming values of coordinates in each of the radiation images other than a radiation image which serves as a reference among the radiation images, into values of coordinates in the radiation image which serves as the reference, such that the coordinates of the center of gravity positions in each of said other radiation images coincide with the corresponding coordinates of the center of gravity positions in the radiation image servicing as the reference, said first affine transformation being represented by the formula ##EQU6## wherein u and v represent the coordinates of the reference closed region, x and y represents the coordinates of the general closed region, a, b, c, and d are the factors representing correction with a rotating operation and correction with an enlargement or reduction factor, and e and f are the factors representing correction with parallel translation,

v) carrying out said first affine transformation, in which the calculated factors of said first affine transformation are used and in which at least the correction with the rotating operation and the correction with the enlargement or reduction factor are carried out on said other radiation images,

vi) setting at least two regions of interest in each of the plurality of the radiation images, which have been obtained from the first affine transformation, such that the regions of interest may be approximately common to the plurality of the radiation images, the regions of interest in a radiation image which serves as a reference among the radiation images being taken as reference regions, the regions of interest in the other radiation images being taken as template regions,

vii) carrying out template matching in order to match the template regions to corresponding reference regions,

viii) calculating values of coordinates of at least two corresponding points for each of the radiation images which have been subjected to the template matching,

ix) calculating the factors of a second affine transformation, which is represented by said formula, such that said corresponding points in the radiation images may coincide with one another, and

x) carrying out said second affine transformation, using factors calculated after the template matching to carry out the correction with the rotating operation, the correction with the enlargement or reduction factor, and the correction with the parallel translation on the plurality of the radiation images containing the template regions.

10. A method as defined in claim 9 wherein each of the radiation images, the positions of which are to be adjusted, has been stored on a stimulable phosphor sheet.

11. A method as defined in claim 9 wherein the template matching is carried out with a correlation method.

12. A method as defined in claim 9 wherein the template matching is carried out with sequential similarity detection algorithms.

13. A method as defined in claim 9 wherein each of the center of gravity positions are identified by obtaining an image signal comprising image signal components representing image information at respective picture elements located in each closed region, and weighting the respective picture elements with image signal values corresponding to the respective picture elements or with the reciprocals of the image signal values.