METHOD FOR ADJUSTING POSITIONS OF RADIATION IMAGES

• US 20030012456A1
• Filed: 03/02/1995
• Published: 01/16/2003
• Est. Priority Date: 03/07/1994
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: NAKAJIMA, NOBUYOSHI, TAKEO, HIDEYA
• Granted Patent: US 6,563,942 B2
• Time in Patent Office: Days
• US Class Current: 382/295
• CPC Class Codes: G06T 2207/10116 X-ray image
• CPC Class Codes: G06T 2207/30004 Biomedical image processing
• CPC Class Codes: G06T 3/02 Affine transformations for image registration G06T3/147; for image mosaicing G06T3/4038
• CPC Class Codes: G06T 7/32 using correlation-based methods
• CPC Class Codes: G06T 7/33 using feature-based methods
• CPC Class Codes: G06T 7/337 involving reference images or patches

Abstract

Template regions are set on a single radiation image, which is among a plurality of radiation images. Template matching is carried out, with which the template regions are matched with the radiation images other than the single radiation image. At least three corresponding points are thereby obtained in each of the plurality of the radiation images. The corresponding points in a single radiation image, which is among the plurality of the radiation images, are taken as reference corresponding points, and factors of affine transformation are calculated with the method of least squares. Affine transformation is then carried out by using the calculated factors of affine transformation. The values of coordinates of the corresponding points in the radiation images other than the single radiation image having the reference corresponding points are thus transformed into values of coordinates of the reference corresponding points such that the reference corresponding points and the corresponding points may coincide with one another.

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 template regions on a single radiation image, which is among the plurality of the radiation images,

ii) carrying out template matching, with which said template regions are matched with the radiation images other than said single radiation image,

iii) thereby obtaining at least three corresponding points in each of the plurality of the radiation images,

iv) taking the corresponding points in a single radiation image, which is among the plurality of the radiation images, as reference corresponding points,

v) calculating factors of affine transformation with the method of least squares, said affine transformation being represented by the formula

$\left(\begin{array}{c}u\\ v\end{array}\right)=\left(\begin{array}{cc}a& b\\ c& d\end{array}\right)<br><br>\left(\begin{array}{c}x\\ y\end{array}\right)+\left(\begin{array}{c}e\\ f\end{array}\right)$

wherein u and v represent the coordinates of the reference corresponding point, x and y represents the coordinates of the corresponding point to be transformed, a, b, c, and dare 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, and

vi) carrying out affine transformation, in which the calculated factors of affine transformation are used, and with which the values of coordinates of the corresponding points in the radiation images other than said single radiation image having the reference corresponding points are transformed into values of coordinates of the reference corresponding points such that the reference corresponding points and the corresponding points in the radiation images other than said single radiation image having the reference corresponding points may coincide with one another.

2. A method as defined in claim 1 wherein the plurality of the radiation images are obtained by exposing a plurality of stimulable phosphor sheets superposed one upon another to radiation, which has been produced by a radiation source and has passed through an object, thereby storing a radiation image of the object on each of the stimulable phosphor sheets, thereafter exposing each of the stimulable phosphor sheets to stimulating rays, which cause the stimulable phosphor sheet to emit light in proportion to the amount of energy stored thereon during its exposure to the radiation, and photoelectrically detecting the emitted light, and

the radiation image, which has been obtained from the stimulable phosphor sheet located at the position closest to the radiation source, is taken as the radiation image, in which the reference corresponding points are to be set.

3. A method as defined in claim 1 wherein the template matching is carried out with a correlation method.

4. A method as defined in claim 1 wherein the template matching is carried out with sequential similarity detection algorithms.