EP0089665A1 — Subtraction processing method and apparatus for r…

Claim 1

Independent Claim 141 words

A subtraction processing method for radiation images comprising the steps of: a) after two or more stimulable phosphor sheets are exposed to a radiation transmitting through an object under conditions different from one another to have radiation images of said object, wherein at least a part of image information is different among said radiation images, recorded on said stimulable phosphor sheets, scanning said stimulable phosphor sheets with stimulating rays to convert said radiation images into light emitted from said stimulable phosphor sheets upon stimulation thereof, b) photoelectrically reading out the amounts of said emitted light and converting them into digital image signals, and c) conducting subtraction of said digital image signals between the corresponding picture elements of said radiation images to obtain a signal for forming an image of a specific structure contained in at least one of said radiation images.

Claim 2

Dependent Claim 141 words

A subtraction processing method for radiation images comprising the steps of: a) after two or more stimulable phosphor sheets are exposed to a radiation transmitting through an object under conditions different from one another to have radiation images of said object, wherein at least a part of image information is different among said radiation images, recorded on said stimulable phosphor sheets, scanning said stimulable phosphor sheets with stimulating rays to convert said radiation images into light emitted from said stimulable phosphor sheets upon stimulation thereof, b) photoelectrically reading out the amounts of said emitted light and converting them into digital image signals, and c) conducting subtraction of said digital image signals between the corresponding picture elements of said radiation images to obtain a signal for forming an image of a specific structure contained in at least one of said radiation images.

Claim 3

Dependent Claim 36 words

A method as defined in Claim 1 wherein said photoelectric read-out is conducted by scanning said stimulable phosphor sheets with the same stimulating rays after the recording on all of said stimulable phosphor sheets is finished.

Claim 4

Dependent Claim 44 words

'3. A method as defined in Claim 1 or 2 wherein said conversion of the read out amounts of said emitted light into the digital image signals is conducted by converting the logarithmic values of the amounts of said emitted light into digital values.

Claim 5

Dependent Claim 127 words

A subtraction processing method for radiation images comprising the steps of: a) scanning two or more stimulable phosphor sheets exposed to a radiation transmitting through an object under conditions different from one another and stored radiation .images of said object therein, at least a part of image information being different among said radiation images with .stimulating rays, b) photoelectrically reading out the amounts of said emitted light and converting them into digital image signals, c) conducting subtraction of said digital imag signals between the corresponding picture elements of said radiation images to obtain a signal for forming an image of a specific structure contained in at least one of said radiation images, and d) reproducing a radiation image of said specific structure by use of said signal.

Claim 6

Dependent Claim 127 words

A subtraction processing method for radiation images comprising the steps of: a) scanning two or more stimulable phosphor sheets exposed to a radiation transmitting through an object under conditions different from one another and stored radiation .images of said object therein, at least a part of image information being different among said radiation images with .stimulating rays, b) photoelectrically reading out the amounts of said emitted light and converting them into digital image signals, c) conducting subtraction of said digital imag signals between the corresponding picture elements of said radiation images to obtain a signal for forming an image of a specific structure contained in at least one of said radiation images, and d) reproducing a radiation image of said specific structure by use of said signal.

Claim 7

Dependent Claim 22 words

A method as defined in Claim 4 wherein said reproducing is conducted by optically recording a visible image on a light-sensitive material.

Claim 8

Dependent Claim 20 words

A method as defined in Claim 4 wherein said reproducing is conducted by displaying a visible image on a display.

Claim 9

Independent Claim 40 words

A method as defined in any of Claims 4 to 6 wherein said reproducing is conducted by once electrically recording said signal for forming an image of a specific structure on a recording medium, and then reproducing said recorded -signal.

Claim 10

Independent Claim 229 words

A method as defined in any of Claims 1 to 7 wherein said method comprising the steps of: 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 spacial 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 11

Dependent Claim 227 words

A method as defined in Claim 8 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 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 for the image signal values Sa, Sb, Sc and S d 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 12

Dependent Claim 54 words

1 0 . A method as defined in Claim 9 wherein said weight coefficients Wa, W b, W c 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 13

Independent Claim 153 words

A method as defined in any of claims 1 to 7 wherein said method comprising the steps of: i) when each radiation image t.o be subtraction processed is recorded on each stimulable phosphor sheet, simultaneously recordi.ng 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 of said marker detected from the light emitted from said stimulable phosphor sheet, iii) moving said stimulable phosphor sheet with respect to scanning lines of stimulating rays based on said detected spacial coordinate and adjusting said spacial coordinate in spacial coordinate predetermined with respect to said scanning lines of stimulating rays, and thereafter, and iv) reading out said radiation image.

Claim 14

Dependent Claim 77 words

A method as defined in Claim 11 wherein, when each radiation image to be subtraction processed is recorded on each stimulable phosphor sheet, simultaneously recording a marker having a shape defining at least on eedge portion of the radiation image area in a position fixed with respect to said radiation image, and reading out image signals of said radiation image by using the detection signal of said edge portion defined by said marker as the synchronizing signal.

Claim 15

Independent Claim 36 words

A method as defined in any of Claims 1 to 7, 8, 11 and 12 wherein an image size reduction processing is conducted on the radiation image after or before said subtrac- tion processing is conducted.

Claim 16

Dependent Claim 110 words

A method of defined in Claim 13 wherein said image size reduction processing is conducted by equally dividing the radiation image before the image size reduction processing to sections having an area larger than the area of each picture element of the original radiation image, calculating the weighted mean of the image data of the picture elements of the radiation image by using the areas over which the respective sections thus obtained are superposed upon the respective picture elements of the original radiation image as the weight coefficients, and using the thus obtained image signal value as the image signals of the picture elements of the scale-down processed radiation image.

Claim 17

Independent Claim 63 words

A method as defined in any of claims 1 to 7, 8, 11, 12 and 13 wherein, at an unnecessary portion developing at the peripheral portion of the subtraction image obtained from two or more radiation images due to incomplete coincidence of the two or more radiation images, an image frame of arbitrary density is created so as to cover said unnecessary portion.

Claim 18

Dependent Claim 118 words

A subtraction processing apparatus comprising a means for scanning two or more stimulable phosphor sheets carrying radiation images, wherein at least a part of image information is different among said radiation images, stored therein with stimulating rays, a means for detecting and photoelectrically converting the light emitted from said stimulable phosphor sheets when said stimulable phosphor sheets are scanned with said stimulating rays, a means for converting the obtained electric signal into a digital signal, and a means for conducting digitally a subtraction processing between said radiation images stored in said two or more stimulable phosphor sheets and obtaining a signal for forming an image of a specific structure contained in at least one of said radiation images.

Claim 19

Dependent Claim 118 words

A subtraction processing apparatus comprising a means for scanning two or more stimulable phosphor sheets carrying radiation images, wherein at least a part of image information is different among said radiation images, stored therein with stimulating rays, a means for detecting and photoelectrically converting the light emitted from said stimulable phosphor sheets when said stimulable phosphor sheets are scanned with said stimulating rays, a means for converting the obtained electric signal into a digital signal, and a means for conducting digitally a subtraction processing between said radiation images stored in said two or more stimulable phosphor sheets and obtaining a signal for forming an image of a specific structure contained in at least one of said radiation images.

Claim 20

Dependent Claim 129 words

A subtraction processing apparatus comprising a means for scanning two or more stimulable phosphor sheets carrying radiation images, wherein at least a part of image information is different among said radiation images, stored therein with stimulating rays, a means for detecting and photoelectrically converting the light emitted from said stimulable phosphor sheets when said stimulable phosphor sheets are scanned with said stimulating rays, a means for converting the obtained electric signal into a digital signal, a means for conducting digitally a subtraction processing between said radiation images stored in said two or more stimulable phosphor sheets and obtaining a signal for forming an image of a specific structure contained in at least one of said radiation images, and a means for reproducing a visible image based on said signal.

Claim 21

Dependent Claim 129 words

A subtraction processing apparatus comprising a means for scanning two or more stimulable phosphor sheets carrying radiation images, wherein at least a part of image information is different among said radiation images, stored therein with stimulating rays, a means for detecting and photoelectrically converting the light emitted from said stimulable phosphor sheets when said stimulable phosphor sheets are scanned with said stimulating rays, a means for converting the obtained electric signal into a digital signal, a means for conducting digitally a subtraction processing between said radiation images stored in said two or more stimulable phosphor sheets and obtaining a signal for forming an image of a specific structure contained in at least one of said radiation images, and a means for reproducing a visible image based on said signal.

Subtraction processing method and apparatus for radiation images

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