Image registration method

• US 4,644,582 A
• Filed: 01/24/1984
• Issued: 02/17/1987
• Est. Priority Date: 01/28/1983
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd., Hitachi Medical Corporation (Hitachi, Ltd.)
• Original Assignee: Hitachi, Ltd.
• Inventors: Omori, Shinji, Yamagata, Shimbu, Ogushi, Akira, Sano, Koichi, Morishita, Koichi, Yokoyama, Tetsuo
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): Couso, Jose L.
• Application Number:
  US06/573,323
• Time in Patent Office: 1,120 Days
• Field of Search: 358/111, 382/6, 382/44, 382/45, 382/46, 382/47, 382/48, 382/18, 382/51, 378/20, 364/731, 356/2
• US Class Current: 382/130
• CPC Class Codes: G06T 3/153 using elastic snapping
• CPC Class Codes: G06T 5/80 Geometric correction
• CPC Class Codes: G06V 10/7515 Shifting the patterns to accommodate for positional errors

Abstract

Two images to be registered are divided into a plurality of image portions. A standard point for the registration is extracted for each of the image portions divided. Coordinate transformations between two images for the registration are conducted for each image portion by using the standard point extracted. The coordinate values transformed between the image portions are smoothed in the case that they discretely change so that they may be smoothly connected.

Claims

1. For use in a digital subtraction method of extracting vascular tracks by conducting subtractions between a first X-ray image before injection of a contrast medium and second X-ray image subsequent to the injection of the contrast medium, an image registration method comprising the steps of:

(a) dividing said first and second X-ray images into a plurality of blocks;

(b) from each of said blocks extracting a standard point for registration;

(c) adjusting positional discrepancies between corresponding blocks of said first and second X-ray images by transforming the coordinates thereof on the basis of the extracted standard point; and

(d) modifying the transformed coordinates in prescribed portions of said blocks along respective interfaces thereof with adjacent blocks so as to effect a smoothing of image features connected through said interfaces;

wherein said standard point extracting step (b) includes the sub-steps of;

determining the difference between said first and second X-ray images;

for each of plural picture elements of which said images are comprised comparing the determined difference in each picture element with a predetermined threshold value; and

selecting as said standard point the point which remains as a result of the threshold comparison.

2. For use in a digital subtraction method of extracting vascular tracks by conducting subtractions between a first X-ray image before injection of a contrast medium and second X-ray image subsequent to the injection of the contrast medium, an image registration method comprising the steps of:

(a) dividing said first and second X-ray images into a plurality of blocks;

(b) from each of said blocks extracting a standard point for registration;

(c) adjusting positional discrepancies between corresponding blocks of said first and second X-ray images by transforming the coordinates thereof on the basis of the extracted standard point; and

(d) modifying the transformed coordinates in prescribed portions of said blocks along respective interfaces thereof with adjacent blocks so as to effect a smoothing of image features connected through said interfaces;

wherein said standard point extracting step (b) includes the sub-steps of;

making up first and second histograms respectively corresponding to said first and second X-ray images;

determining a curve indicative of the integrated values of the differences between said first and second histograms; and

conducting a selection from said second X-ray image by using as said standard point the point which has a lower X-ray strength than that at the peak point of the determined curve.

3. For use in a digital subtraction method of extracting vascular tracks by conducting subtractions between a first X-ray image before injection of a contrast medium and second X-ray image subsequent to the injection of the contrast medium, an image registration method comprising the steps of:

(a) dividing said first and second X-ray images into a plurality of blocks;

(b) from each of said blocks extracting a standard point for registration;

(c) adjusting positional discrepancies between corresponding blocks of said first and second X-ray images by transforming the coordinates thereof on the basis of the extracted standard point; and

(d) modifying the transformed coordinates in prescribed portions of said blocks along respective interfaces thereof with adjacent blocks so as to effect a smoothing of image features connected through said interfaces;

wherein said standard point extracting step (b) includes the sub-steps of;

comparing the positional discrepancy of said standard point, which has been extracted for each divided block, and the positional discrepancy of another standard point, which has been extracted for another block in the neighborhood of said divided block; and

removing the standard point which is judged to be singular as a result of said comparison.

4. For use in a digital subtraction method of extracting vascular tracks by conducting subtractions between a first X-ray image before injection of a contrast medium and second X-ray image subsequent to the injection of the contrast medium, an image registration method comprising the steps of:

(a) dividing said first and second X-ray images into a plurality of blocks;

(b) from each of said blocks extracting a standard point for registration;

(c) adjusting positional discrepancies between corresponding blocks of said first and second X-ray images by transforming the coordinates thereof on the basis of the extracted standard point; and

(d) modifying the transformed coordinates in prescribed portions of said blocks along respective interfaces thereof with adjacent blocks so as to effect a smoothing of image features connected through said interfaces;

wherein said standard point extracting step (b) includes the sub-steps of;

correlating said first and second X-ray images for each partial region that is determined by a template having an area varying with the coarseness of the image; and

selecting said standard point on the basis of the correlated result.