Radiation imaging system

Patent metadata

Field	Value
Publication number	US-9743018-B2
Application number	US-201414903271-A
Country	US
Kind code	B2
Filing date	Jul 7, 2014
Priority date	Jul 9, 2013
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

A radiation imaging system capable of obtaining excellent image quality is provided. The radiation imaging system includes a detection unit ( 205 ) configured to include a plurality of pixels which are arranged in a matrix and which output pixel values by converting radial rays into charges and to output image information, driving control means ( 204 ) for causing the plurality of pixels to perform a resetting operation until a signal indicating irradiation with radial rays is supplied and to stop the resetting operation and perform an operation of accumulating charges when the signal indicating irradiation with radial rays is supplied, and for performing an operation of reading pixel values of the plurality of pixels after the irradiation with radial rays is terminated so as to output image information corresponding to the irradiation with radial rays, correction coefficient obtaining means ( 207 ) for calculating correction coefficients in accordance with the image information output from the detection unit, and image correction means ( 208 ) for correcting the image information output from the detection unit using the correction coefficients calculated by the correction coefficient obtaining means.

First claim

The invention claimed is:

1. A radiation imaging system comprising:
a detection unit configured to include a plurality of pixels which are arranged in a matrix and which output pixel values by converting radial rays into charges and to output image information;
driving control means for causing the plurality of pixels to perform a resetting operation until a signal indicating irradiation with radial rays is supplied and to stop the resetting operation and perform an operation of accumulating charges when the signal indicating irradiation with radial rays is supplied, and for performing an operation of reading pixel values of the plurality of pixels after the irradiation with radial rays is terminated so as to output image information corresponding to the irradiation with radial rays;
correction coefficient obtaining means for calculating correction coefficients in accordance with the image information output from the detection unit; and
image correction means for correcting the image information output from the detection unit using the correction coefficients calculated by the correction coefficient obtaining means,
wherein the correction coefficient obtaining means sets a pair of a first pixel value of a pixel included in a row which has been subjected to the resetting operation after the irradiation with radial rays is started and a second pixel value of a pixel which is included in a row which has not been subjected to the resetting operation after the irradiation with radial rays is started and which is included in a column including the pixel having the first pixel value, and
the correction coefficients are calculated using the pair of values which belong to different columns.

2. The radiation imaging system according to claim 1 , wherein the driving control means controls operation of the detection unit using a signal indicating irradiation with radial rays output from a radiation control apparatus which controls irradiation with radial rays.

3. The radiation imaging system according to claim 1 , further comprising:
detection means for detecting irradiation with radial rays and outputting a signal indicating the irradiation with radial rays,
wherein the driving control means controls operation of the detection unit using the signal indicating irradiation with radial rays output from the detection means.

4. The radiation imaging system according to claim 1 , wherein
the correction coefficient obtaining means sets a pair of a first average value obtained by averaging pixel values of a plurality of pixels included in a row which has been subjected to the resetting operation after the irradiation with radial rays is started and a second average value obtained by averaging pixel values of a plurality of pixels which are included in a row which has not been subjected to the resetting operation after the irradiation with radial rays is started and which are included in columns including the plurality of pixels used for generating the first average value, and
the correction coefficients are calculated using a plurality of pairs of values included in different columns.

5. The radiation imaging system according to claim 1 , wherein the correction coefficient obtaining means calculates the correction coefficients using a least-square method.

6. The radiation imaging system according to claim 1 , wherein the correction coefficient obtaining means calculates the correction coefficients in accordance with a row number of a row where the resetting operation is stopped.

7. The radiation imaging system according to claim 6 , wherein the correction coefficient obtaining means calculates the correction coefficients in accordance with the row number of the row where the resetting operation is stopped which is input by the driving control means.

8. The radiation imaging system according to claim 6 , wherein the correction coefficient obtaining means calculates the correction coefficient in accordance with the row number of the row where the resetting operation is stopped which is calculated in accordance with the image information.

9. The radiation imaging system according to claim 6 , wherein the first pixel value is a pixel value of a pixel included in the row where the resetting operation is stopped, and the second pixel value is a pixel value of a pixel included in a row immediately after the row where the resetting operation is stopped.

10. The radiation imaging system according to claim 6 , wherein
the first pixel value is a pixel value of a pixel included in a row immediately before the row where the resetting operation is stopped, and
the second pixel value is a pixel value of a pixel included in a row immediately after the row where the resetting operation is stopped.

11. The radiation imaging system according to claim 1 , wherein the correction coefficients include an offset correction coefficient, a gain correction coefficient, and a width correction coefficient indicating a width of artifact generated in an image.

12. The radiation imaging system according to according to claim 1 , wherein the correction coefficients include an offset correction coefficient, a gain correction coefficient, and shape correction coefficient strings indicating amounts of artifact in individual rows generated in an image.

13. The radiation imaging system according to claim 11 , wherein the correction coefficient obtaining means calculates the width correction coefficient or the shape correction coefficient strings in accordance with the image information.

14. The radiation imaging system according to claim 11 , wherein the correction coefficient obtaining means calculates the width correction coefficient or the shape correction coefficient strings in accordance with current supplied to a bias line of the pixels.

15. The radiation imaging system according to claim 1 , wherein the correction coefficient obtaining means removes, when the pair of values is abnormal, the abnormal pair of values before calculating the correction coefficients.

16. The radiation imaging system according to claim 15 , wherein the correction coefficient obtaining means determines that the pair of values is abnormal in a case where at least one of the pixel values in the pair of values is out of an amount of variation estimated from quantum noise relative to neighboring pixel values.

17. The radiation imaging system according to claim 15 , wherein the correction coefficient obtaining means determines that the pair of values is abnormal in a case where at least one of the pixel values in the pair of values is out of an amount of variation estimated from system noise relative to neighboring pixel values.

18. The radiation imaging system according to claim 15 , wherein the correction coefficient obtaining means determines that the pair of values is abnormal in a case where at least one of the pixel values in the pair of values is saturated.

19. The radiation imaging system according to claim 15 , wherein the correction coefficient obtaining means determines that the pair of values is abnormal in a case where at least one of the pixel values in the pair of values is a negative value.

20. The radiation imaging system according to claim 15 , wherein the correction coefficient obtaining means determines that the pair of values is abnormal in a case where at least one of the pixel values in the pair of values corresponds to a defective pixel.

Assignees

• Canon Kk

Inventors

• Iwashita Atsushi
• Kameshima Toshio
• Yagi Tomoyuki
• Takenaka Katsuro
• Okada Hideyuki
• Sato Sho
• Sato Eriko
• Ryu Takuya

Classifications

• A61B6/4233 Primary

  using matrix detectors · CPC title

• A61B6/585

  Calibration of detector units · CPC title

• H04N25/63 Primary

  applied to dark current · CPC title

• H04N5/361

  Electricity · mapped topic

• H04N5/32 Primary

  Transforming X-rays (cameras or camera modules for generating image signals from X-rays H04N23/30; circuitry of SSIS for transforming X-rays into image signals H04N25/30) · CPC title