Radiation imaging apparatus and control method thereof, and radiation imaging system

Patent metadata

Field	Value
Publication number	US-10028364-B2
Application number	US-201514789599-A
Country	US
Kind code	B2
Filing date	Jul 1, 2015
Priority date	Feb 3, 2012
Publication date	Jul 17, 2018
Grant date	Jul 17, 2018

Abstract

An FPD detects an X-ray image of an object. The FPD includes a plurality of pixels arranged in its image capturing field. Each pixel receives X-rays emitted from an X-ray source, and outputs a pixel value in accordance with an X-ray dose applied thereto. A pixel determiner determines a minimum-value pixel out of the pixels based on the pixel values of the pixels. The minimum-value pixel is a pixel whose pixel value is the lowest. The pixel determiner sets the minimum-value pixel as an exposure control pixel. A comparator compares a first integrated value, which is an integrated value of the pixel values of the minimum-value pixel, with a predetermined first threshold value. The comparator performs X-ray emission control such that, when the first integrated value has reached the first threshold value, the X-ray source stops emitting the X-rays.

First claim

What is claimed is:

1. A radiation imaging apparatus comprising:
an image detector for detecting a radiographic image of an object, said image detector including a plurality of pixels arranged in an image capturing field, each of said pixels receiving radiation emitted from a radiation source and outputting a pixel value in accordance with a received radiation dose;
a pixel determiner for determining at least one typical low-value pixel from said pixels based on said pixel values, and setting said at least one typical low-value pixel as an exposure control pixel, said pixel determiner determining said at least one typical low-value pixel out of said pixels present within an index area being predetermined in said image capturing field in accordance with a body portion to be imaged;
a comparator for comparing a first integrated value being an integrated value of said pixel value of said at least one typical low-value pixel with a predetermined first threshold value, and performing radiation emission control such that, when said first integrated value has reached said first threshold value, said radiation source stops emitting said radiation,
wherein said pixels include a plurality of normal pixels for specific use in detection of said radiographic image, and a plurality of detection pixels distributed throughout said image capturing field to detect said radiation dose; and
a pixel value estimator for estimating said pixel value of said normal pixel based on said pixel values of said detection pixels near said normal pixel to be estimated,
wherein said pixel determiner determines said at least one typical low-value pixel based on said estimated pixel values.

2. The radiation imaging apparatus according to claim 1 , further comprising:
an irradiation field determiner for determining an irradiation field based on said pixel values, said irradiation field being a field irradiated with said radiation in said image capturing field, wherein
said pixel determiner deteimines in said irradiation field a directly exposed area being an area applied with said radiation directly without through said object, an implant area being an area of an implant implanted in said object, and an object area being an area excluding said directly exposed area and said implant area from said irradiation field; and
said at least one typical low-value pixel is determined out of said pixels in said object area.

3. The radiation imaging apparatus according to claim 2 , wherein said pixel determiner determines said object area based on a histogram of said pixel values of said pixels in said irradiation field.

4. The radiation imaging apparatus according to claim 1 , wherein
said image detector has a plurality of pixel groups each including one or more of said normal pixels and one or more of said detection pixels, and said detection pixels are laid out differently between said pixel groups adjoining to each other; and
said pixel value estimator estimates said pixel value of said normal pixel of a first pixel group, based on said pixel value of said detection pixel belonging to said first pixel group and said pixel value of said detection pixel belonging to a second pixel group adjoining to said first pixel group.

5. The radiation imaging apparatus according to claim 1 , wherein said pixel determiner determines said at least one typical low-value pixel out of said detection pixels.

6. The radiation imaging apparatus according to claim 1 , wherein
signal lines electrically connected to said pixels are routed in said image capturing field to output said pixel values; and
said detection pixel is connected to said signal line directly or through a switching element.

7. The radiation imaging apparatus according to claim 1 , wherein said pixels include a combined pixel that is composed of a first subpixel functioning as said normal pixel and a second subpixel functioning as said detection pixel.

8. A radiation imaging apparatus comprising:
an image detector for detecting a radiographic image of an object, the image detector including a plurality of pixels arranged in an image capturing field, each of the pixels receiving radiation emitted from a radiation source and outputting a pixel value in accordance with a received radiation dose;
a pixel determiner for determining at least one typical low-value pixel from the pixels based on the pixel values, and setting the at least one typical low-value pixel as an exposure control pixel; and
a comparator for comparing a first integrated value being an integrated value of the pixel value of the at least one typical low-value pixel with a predetermined first threshold value, and performing radiation emission control such that, when the first integrated value has reached the first threshold value, the radiation source stops emitting the radiation,
wherein the pixel determiner determines a minimum-value pixel that outputs a lowest pixel value from at least one peak of a histogram of the pixel values, and sets the minimum-value pixel as the at least one typical low-value pixel.

9. The radiation imaging apparatus according to claim 8 , further comprising:
an irradiation field determiner for determining an irradiation field based on said pixel values, said irradiation field being a field irradiated with said radiation in said image capturing field, wherein
said pixel determiner determines in said irradiation field a directly exposed area being an area applied with said radiation directly without through said object, an implant area being an area of an implant implanted in said object, and an object area being an area excluding said directly exposed area and said implant area from said irradiation field; and
said at least one typical low-value pixel is determined out of said pixels in said object area.

10. The radiation imaging apparatus according to claim 9 , wherein said pixel determiner determines said object area based on a histogram of said pixel values of said pixels in said irradiation field.

11. The radiation imaging apparatus according to claim 8 , wherein said pixels include a plurality of normal pixels for specific use in detection of said radiographic image, and a plurality of detection pixels distributed throughout said image capturing field to detect said radiation dose.

12. The radiation imaging apparatus according to claim 11 , further comprising:
a pixel value estimator for estimating said pixel value of said normal pixel based on said pixel values of said detection pixels near said normal pixel to be estimated; and
said pixel determiner determines said at least one typical low-value pixel based on said estimated pixel values.

13. The radiation imaging apparatus according to claim 12 , wherein
said image detector has a plurality of pixel groups each including one or more of said normal pixels and one or more of said detection pixels, and said detection pixels are laid out differently between said pixel groups adjoining to each other; and
said pixel value estimator estimates said pixel value of said normal pixel of a first pixel group, based on said pixel value of said detection pixel belonging to said first pixel group and said pixel value of said detection pixel belonging to a second pixel group adjoining to said first pixel group.

14. The radiation imaging apparatus according to claim 11 , wherein said pixel determiner determines said at least one typical low-value pixel out of said detection pixels.

15. The radiation imaging apparatus according to claim 11 , wherein
signal lines electrically connected to said pixels are routed in said image capturing field to output said pixel val

Assignees

• Fujifilm Corp

Inventors

• Tsuji Tetsuya

Classifications

• A61B2560/0214

  of power generation or supply · CPC title

• G01T1/02

  Dosimeters (G01T1/15 takes precedence) · CPC title

• H05G1/44 Primary

  in which the switching instant is determined by measuring the amount of radiation directly {(dosimetry in general G01T1/02)} · CPC title

• H05G1/56

  Switching-on; Switching-off · CPC title

• A61B6/542

  involving control of exposure · CPC title