Method for reading a radiographic image

Claim 3

A radiation image read-out method for scanning a stimulable phosphor sheet, having a radiation image stored thereon by imagewise exposure, with stimulating rays which cause the stimulable phosphor sheet to emit light in proportion to stored radiation energy, and detecting the emitted light by a photoelectric read-out means, the radiation image read-out method comprising the steps of i) determining the decrease with time of the amount of light emitted by said stimulable phosphor sheet having a predetermined level of radiation energy stored thereon when said stimulable phosphor sheet is exposed to a predetermined amount of stimulating rays, and ii) compensating for the decrease with time of said amount of emitted light, which arises within read-out time for said radiation image, by calculating a compensation coefficient as a function of time based on said decrease with time for selected portions of said stimulable phosphor sheet exposed to stimulating rays, and multiplying a signal proportional to the light emitted by each selected portion of the stimulable phosphor sheet upon exposure to stimulating rays by the compensation coefficient for the respective selected portion of the stimulable phosphor sheet.

Claim 4

A radiation image read-out method for scanning a stimulable phosphor sheet, having a radiation image stored thereon by imagewise exposure, with stimulating rays which cause the stimulable phosphor sheet to emit light in proportion to stored radiation energy, and detecting the emitted light by a photoelectric read-out means, the radiation image read-out method comprising the steps of i) determining the decrease with time of the amount of light emitted by said stimulable phosphor sheet having a predetermined level of radiation energy stored thereon when said stimulable phosphor sheet is exposed to a predetermined amount of stimulating rays, and ii) compensating for the decrease with time of said amount of emitted light, which arises within read-out time for said radiation image, by calculating a compensation coefficient as a function of time based on said decrease with time for selected portions of said stimulable phosphor sheet exposed to stimulating rays, and multiplying a signal proportional to the light emitted by each selected portion of the stimulable phosphor sheet upon exposure to stimulating rays by the compensation coefficient for the respective selected portion of the stimulable phosphor sheet.

Claim 5

The method of claim 2 wherein said method comprises the steps of generation of said stimulating light, driving said stimulating rays to effect scanning said sheet, receiving a photosignal generated by said emitted light from said sheet and converting said photosignal into an electric signal, processing said electric signal, and rectifying said electric signal.

Claim 6

The method of claim 3 wherein said compensating comprises intensity control of said stimulating light generation.

Claim 7

The method of claim 4 wherein said generation is achieved by a laser driver, and said intensity control is carried out by regulating an output of said laser driver.

Claim 8

The method of claim 3 wherein said compensating comprises scanning speed control of said stimulating rays.

Claim 9

The method of claim 6 wherein said driving is carried out by a deflector driver, and said scanning speed control is carried out by regulating said deflector driver.

Claim 10

The method of claim 3 wherein said compensating comprises gain control in a photoelectric conversion.

Claim 11

The method of claim 8, wherein a photomultiplier is utilized as a means for receiving and converting a photo signal, and said gain control in the photoelectric conversion is carried out by regulating the power source of said photomultiplier.

Claim 12

The method of claim 3 wherein said compensating comprises controlling a factor in said electric signal processing.

Claim 13

The method of claim 10 wherein said electric signal processing signal comprises a current voltage converting amplifier, a log converter, a sample holder an A/D converter and a CPU.

Claim 14

The method of claim 11 wherein said factor control during said electric signal processing is achieved by regulating an amplification gain in said current voltage converting amplifier.

Claim 15

The method of claim 11 wherein said factor control during said electric signal processing is achieved by regulating a conversion gain in said log converter and regulating an internal gain in said sample holder.

Claim 16

The method of claim 11 wherein said factor control during said electric signal processing is achieved by regulating a dynamic range in said A/D converter and regulating an input signal in the calculation factor of said CPU.

Claim 17

The method of claim 2 wherein said compensating is carried out based on the time period from said imagewise exposure to the commencement of reading.

Claim 18

The method of claim 15, wherein said compensating is carried out based on the information of light decay characteristics of said sheet determined prior to the compensating.

Claim 19

The method of claim 15, wherein said time is counted automatically in connection with exposing and reading operation.

Claim 20

The method of claim 15, wherein said sheet comprises a timer unit.

Claim 21

The method of claim 15, wherein said compensating is carried out based on the combination of the time period from said imagewise exposure to the commencement of reading and on the reading of the stimulable emission emitted from a predetermined portion of said sheet to which a predetermined quantity of exposure is given simultaneously with said imagewise exposure.

Claim 22

The method of claim 19, wherein said time is counted automatically in connection with the exposing and reading operation.

Claim 23

The method of claim 2, wherein said compensating is carried out based on the reading of the stimulable emission emitted from a predetermined portion of said sheet to which a predetermined quantity of exposure is given simultaneously with said imagewise exposure.

Claim 24

The method of claim 21, wherein said predetermined portion is provided adjacent to an imagewise area of said panel.

Claim 25

The method of claim 2, wherein said image-wise exposure is by X-ray.

Claim 26

The method of claim 2, wherein said stimulating rays are from 500 nm to 2000 nm in wavelength.

Claim 27

The method of claim 2, wherein said stimulable phosphor is alkali halide phosphor represented by the following formula: M.sup.I X·aM.sup.II X.sub.2.sup.' ·bM.sup.III X.sub.3.sup." : cA wherein M I represents at least one of alkaline metal selected from the group consisting of Li, Na, K, Rb and Cs; M II represents at least one divalent metal selected from the group consisting of Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu and Ni; M III represents at least one trivalent metal selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm. Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga and In; X, X' and X" independently represent at least one halogen atom selected from the group consisting of F, Cl, I and Br; A represents at least one metal selected from the group consisting of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu and Mg; a, b and c are numerals in the range of 0≦a<0.5, 0≦b<0.5 and 0<c≦0.2, respectively.

Claim 28

The method of claim 2 wherein said decrease with time is a predetermined relationship inputted into a memory, and said compensation coefficient is calculated based on said relationship.