Radiation imaging apparatus, radiation image processing apparatus, and image processing method

1. A radiation image processing apparatus comprising:

an obtaining unit configured to obtain a radiation image signal and electrical signals, the radiation image signal being read during a first radiation imaging from a radiation detector including a plurality of pixels, and the electrical signals being read in succession from the radiation detector continuously after the reading of the radiation image signal and corresponding to accumulated electric charges of the plurality of pixels;

a determination unit configured to determine whether or not to correct another radiation image signal read from the radiation detector during a second radiation imaging that is performed continuously after the reading of the electrical signals based on a temporal change in the obtained electrical signals; and

a correction unit configured to correct said another radiation image signal based on a result of the determination and dark current data which is obtained after the first radiation imaging based on the temporal charge in the obtained electrical signals.

2. The radiation image processing apparatus according to claim 1 , wherein

when the determination unit determines that the correction is to be made based on the temporal change, said another radiation image signal is corrected based on the temporal change, and

when the determination unit determines that the correction is not to be made based on the temporal change, said another radiation image signal is corrected based on dark current data obtained before the second radiation imaging.

3. A radiation imaging apparatus including an image detection unit and an image processing unit, the image detection unit including a plurality of radiation detection elements that generate electric charges in accordance with a dose of radiation transmitted through an object, and the image processing unit processing a radiation image detected by the image detection unit,

wherein the image processing unit includes:

a correction image generation unit configured to generate, based on a plurality of unirradiated images that are obtained in succession by the image detection unit while radiation is not emitted, a correction image for a radiation image that is obtained at an arbitrary timing after the plurality of unirradiated images are obtained; and

a correction unit configured to correct the radiation image using the correction image, wherein

the correction image generation unit applies non-linear approximation to a temporal change in signal intensities of the plurality of unirradiated images in units of the plurality of radiation detection elements, and switches between methods for generating a correction image in accordance with a coefficient of determination of an obtained approximate equation.

4. The radiation imaging apparatus according to claim 3 , wherein the number of unirradiated images used in generation of the correction image is at least three.

5. The radiation imaging apparatus according to claim 3 , wherein the correction image generation unit generates the correction image using the approximate equation when the coefficient of determination is larger than or equal to a threshold, and generates the correction image using an unirradiated image that immediately precedes obtainment of the radiation image when the coefficient of determination is smaller than the threshold.

6. The radiation imaging apparatus according to claim 5 , wherein when an accumulation time period for obtaining the plurality of unirradiated images differs from an accumulation time period for obtaining the radiation image and the coefficient of determination of the approximate equation is larger than or equal to the threshold, the correction image generation unit generates the correction image by integrating the approximate equation in accordance with the accumulation time period for obtaining the radiation image.

7. The radiation imaging apparatus according to claim 5 , wherein when an accumulation time period for obtaining the plurality of unirradiated images differs from an accumulation time period for obtaining the radiation image and the coefficient of determination of the approximate equation is smaller than the threshold, the correction image generation unit generates the correction image by multiplying the unirradiated image that immediately precedes obtainment of the radiation image by a ratio between the accumulation time periods.

8. The radiation imaging apparatus according to claim 5 , wherein the threshold for the coefficient of determination is 0.6 or larger.

9. The radiation imaging apparatus according to claim 3 , wherein the non-linear approximation is approximation using a logarithmic function.

10. The radiation imaging apparatus according to claim 3 , wherein the non-linear approximation is applied to all of the plurality of radiation detection elements.

11. The radiation imaging apparatus according to claim 3 , wherein when a radiation image is not captured within a predetermined time period after obtaining a last unirradiated image, the approximate equation and the coefficient of determination are updated by obtaining an unirradiated image again and reapplying the non-linear approximation.

12. The radiation imaging apparatus according to claim 3 , wherein an interval at which the plurality of unirradiated images are obtained is changed in accordance with the coefficient of determination.

13. An image processing method for a radiation image processing apparatus, the method comprising:

an obtaining step of obtaining a radiation image signal and electrical signals, the radiation image signal being read during a first radiation imaging from a radiation detector including a plurality of pixels, and the electrical signals being read in succession from the radiation detector continuously after the reading of the radiation image signal and corresponding to accumulated electric charges of the plurality of pixels;

a determination step of determining whether or not to correct another radiation image signal read from the radiation detector during a second radiation imaging that is performed continuously after the reading of the electrical signals based on a temporal change in the obtained electrical signals; and

a correction step of correcting said another radiation image signal based on a result of the determination and dark current data which is obtained after the first radiation imaging based on the temporal charge in the obtained electrical signals.

14. An image processing method for a radiation imaging apparatus including an image detection unit and an image processing unit, the image detection unit including a plurality of radiation detection elements that generate electric charges in accordance with a dose of radiation transmitted through an object, and the image processing unit processing a radiation image detected by the image detection unit, the method comprising:

a correction image generation step of generating, based on a plurality of unirradiated images that are obtained in succession by the image detection unit while radiation is not emitted, a correction image for a radiation image that is obtained at an arbitrary timing after the plurality of unirradiated images are obtained; and

a correction step of correcting the radiation image using the correction image, wherein

the correction image generation step applies non-linear approximation to a temporal change in signal intensities of the plurality of unirradiated images in units of the plurality of radiation detection elements, and switches between methods for generating a correction image in accordance with a coefficient of determination of an obtained approximate equation.

15. A non-transitory computer readable storage medium storing a program for causing a computer to function as the units of the radiation image processing apparatus according to claim 1 .

16. A non-transitory computer readable storage medium storing a program for causing a computer to function as the units of the radiation imaging apparatus according to claim 3 .