Radiation image detecting device, radiation imaging system and operation method thereof

A radiation imaging system comprising:

• (A) a radiation source for applying radiation to an object;
• (B) a source control device for controlling operation of said radiation source;
• and
• (C) a radiation image detecting device having an image detector formed with an imaging area, and used together with a grid capable of being disposed in front of said image detector, said radiation image detecting device including:
• said grid having strip-shaped radiation transparent layers and radiation absorbing layers extending in a first direction to remove scattered rays produced upon radiation passing through an object, a plurality of said radiation transparent layers and said radiation absorbing layers being alternatingly formed at a grid pitch, G, in a second direction orthogonal to said first direction;
• said imaging area being provided with a plurality of pixels arrayed in said second direction at a pixel pitch Δ and a plurality of dose measurement sensors, said plurality of pixels accumulating electric charge in accordance with a received radiation dose in a readable manner to detect a radiographic image of said object, said plurality of dose measurement sensors measuring said received radiation dose;
• and
• provided that said image detector captures a radiographic image of said grid, and said dose measurement sensor that is not situated in a specific position in which an output signal is at a maximum value or a minimum value is designated as a first dose measurement sensor and said dose measurement sensor that is in said specific position is designated as a second dose measurement sensor, the position of said plurality of dose measurement sensors being determined so as to satisfy the following condition 1:
• condition 1:
• provided that fG/fN≠odd number and said grid and said pixels are relatively shifted to said second direction C times by one pixel, the number of said first dose measurement sensors is larger than the number of said second dose measurement sensors at any time within the range of a cycle C, wherein
• fG=1/G represents a grid frequency,
• fN=1/(2Δ) represents a Nyquist frequency of said pixels, and
• said cycle C is a cycle of a repetition pattern appearing in said second direction in said radiographic image of said grid, and is represented in units of the number of said pixels.

An operation method of a radiation imaging system including:

• (A) a radiation source for applying radiation to an object;
• (B) a source control device for controlling operation of said radiation source;
• and
• (C) a radiation image detecting device having an image detector formed with an imaging area, and used together with a grid capable of being disposed in front of said image detector, said radiation image detecting device including:
• said grid having strip-shaped radiation transparent layers and radiation absorbing layers extending in a first direction to remove scattered rays produced upon radiation passing through an object, a plurality of said radiation transparent layers and said radiation absorbing layers being alternatingly formed at a grid pitch, G, in a second direction orthogonal to said first direction;
• said imaging area being provided with a plurality of pixels arrayed in said second direction at a pixel pitch Δ and a plurality of dose measurement sensors, said plurality of pixels accumulating electric charge in accordance with a received radiation dose in a readable manner to detect a radiographic image of said object, said plurality of dose measurement sensors measuring said received radiation dose;
• and
• provided that said image detector captures a radiographic image of said grid, and said dose measurement sensor that is not situated in a specific position in which an output signal is at a maximum value or a minimum value is designated as a first dose measurement sensor and said dose measurement sensor that is in said specific position is designated as a second dose measurement sensor, the position of said plurality of dose measurement sensors being determined so as to satisfy the following condition 1:
• condition 1:
• provided that fG/fN≠odd number and said grid and said pixels are relatively shifted to said second direction C times by one pixel, the number of said first dose measurement sensors is larger than the number of said second dose measurement sensors at any time within the range of a cycle C, wherein
• fG=1/G represents a grid frequency,
• fN=1/(2Δ) represents a Nyquist frequency of said pixels, and
• said cycle C is a cycle of a repetition pattern appearing in said second direction in said radiographic image of said grid, and is represented in units of the number of said pixels,
• said operation method comprising the steps of:
• (i) measuring a radiation dose by at least a group of dose measurement sensors out of said plurality of dose measurement sensors;
• (ii) judging whether or not a total radiation dose being an integrated value of each radiation dose measured by said group of dose measurement sensors or an average value of said total radiation doses reaches a target dose;
• and
• (iii) stopping the operation of said radiation source to stop emission of said radiation, at the instant when said total radiation dose or said average value reaches said target dose.