US4710875A — Alignment procedure for radiation images undergoi…

Claim 1

Independent Claim 321 words

A subtraction processing method for radiation images including the steps of recording two or more radiation images on separate stimulable phosphor sheets, at least a part of image information being different among said radiation images, scanning the respective stimulable phosphor sheets with stimulating rays to sequentially release the radiation energy stored in the stimulable phosphor sheets as light emission, photoelectrically detecting the emitted light by a light detecting means to obtain digital image signal corresponding to the respective radiation images, and extracting an image of a specific portion of said radiation images by conducting a subtraction processing among said digital image signal, the subtraction processing method for radiation images comprising: (i) when each radiation image to be subtraction processed is recorded on each stimulable phosphor sheet, simultaneously recording a marker having such a shape as provides a reference point or a reference line to said stimulable phosphor sheet in a position fixed with respect to said radiation image, (ii) scanning said stimulable phosphor sheet carrying said radiation image stored therein with stimulating rays, and detecting the position coordinate of said reference point or said reference line provided by said marker from the digital image signal of said image detected from the light emitted from said stimulable phosphor sheet, (iii) conducting the steps (i) and (ii) for said two or more radiation images to be subtraction processed, (iv) calculating a rotation and a shift among said two or more radiation images based on the respective reference points or reference lines corresponding to said two or more radiation images to be subtraction processed, (v) when said rotation exists, rotating digitally either one of said radiation images to be subtraction processed, and/or when said shift exists, moving digitally either one of said radiation images to be subtraction processed, and conducting a subtraction processing of the image signal value among the corresponding picture elements of said two or more radiation images to be subtraction processed.

Claim 2

Dependent Claim 321 words

A subtraction processing method for radiation images including the steps of recording two or more radiation images on separate stimulable phosphor sheets, at least a part of image information being different among said radiation images, scanning the respective stimulable phosphor sheets with stimulating rays to sequentially release the radiation energy stored in the stimulable phosphor sheets as light emission, photoelectrically detecting the emitted light by a light detecting means to obtain digital image signal corresponding to the respective radiation images, and extracting an image of a specific portion of said radiation images by conducting a subtraction processing among said digital image signal, the subtraction processing method for radiation images comprising: (i) when each radiation image to be subtraction processed is recorded on each stimulable phosphor sheet, simultaneously recording a marker having such a shape as provides a reference point or a reference line to said stimulable phosphor sheet in a position fixed with respect to said radiation image, (ii) scanning said stimulable phosphor sheet carrying said radiation image stored therein with stimulating rays, and detecting the position coordinate of said reference point or said reference line provided by said marker from the digital image signal of said image detected from the light emitted from said stimulable phosphor sheet, (iii) conducting the steps (i) and (ii) for said two or more radiation images to be subtraction processed, (iv) calculating a rotation and a shift among said two or more radiation images based on the respective reference points or reference lines corresponding to said two or more radiation images to be subtraction processed, (v) when said rotation exists, rotating digitally either one of said radiation images to be subtraction processed, and/or when said shift exists, moving digitally either one of said radiation images to be subtraction processed, and conducting a subtraction processing of the image signal value among the corresponding picture elements of said two or more radiation images to be subtraction processed.

Claim 3

Dependent Claim 214 words

A method as defined in claim 1 wherein, when four picture elements approaching a picture element point A by coordinate rotation are taken to be a, b, c and d on the coordinate system before the rotation operation on said radiation image to be rotated, and when the image signal values of said four picture elements a, b, c and d are Sa, Sb, Sc and Sd, respectively, said rotation operation is conducted by expressing the image signal value S A of said picture element point A after the rotation by a weighted mean represented by the formula of S.sub.A =(Wa·Sa+Wb·Sb+ Wc·Sc+Wd·Sd)/Wtot wherein Wtot=Wa+Wb+Wc+Wd, and Wa, Wb, Wc and Wd respectively are the weight coefficients corresponding to picture elements a, b, c and d, or said rotation is conducted by cumulating the proportional distribution values of the image signal value S A of said picture element point A by said weight coefficients represented by the formulae of Sa=(Wa/Wtot)·S.sub.A Sb=(Wb/Wtot)·S.sub.A Sc=(Wc/Wtot)·S.sub.A Sd=(Wd/Wtot)·S.sub.A for the image signal values Sa, Sb, Sc and Sd of the four picture elements a, b, c and d which are the points on the coordinate system before the rotation operation and which approach said picture element point A by the rotation operation of the coordinate including said picture element point A.

Claim 4

Dependent Claim 55 words

A method as defined in claim 2 wherein said weight coefficients Wa, Wb, Wc and Wd are the weight coefficients selected in advance and having the largest value for the weight coefficient corresponding to the picture element nearest to the aforesaid picture element A among said four picture elements proximate to said picture element A.

Claim 5

Dependent Claim 51 words

A method as defined in claim 2 wherein said weight coefficients Wa, Wb, Wc and Wd are 1/la, 1/lb, 1/lc and 1/ld, respectively when the distances between said picture element A and said four picture elements a, b, c and d are taken to be la, lb, lc and ld, respectively.

Claim 6

Dependent Claim 49 words

A method as defined in claim 2 wherein said weight coefficients Wa, Wb, Wc and Wd are areas calculated by making the approximation that the rotation angle is zero in the course of calculating the areas over which said picture element A is superposed upon said four picture elements.

Claim 7

Dependent Claim 62 words

A method as defined in claim 2 wherein said weight coefficients Wa, Wb, Wc and Wd are the weight coefficients having a value other than zero only for the weight coefficient corresponding to the picture element nearest to said picture element A among four picture elements a, b, c and d approaching said picture element A, the remaining weight coefficients being zero.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1990-11-30	1991-06-01	1991-12-01	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1994-11-30	1995-06-01	1995-12-01	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1998-11-30	1999-06-01	1999-12-01	$7700.00	Window Closed / Lapsed

Alignment procedure for radiation images undergoing subtraction processing

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