Radiographic image detector and control method therefor
First Claim
1. A radiographic image detector for detecting a radiographic image from radioactive rays projected from a radiation source, the radiographic image detector comprising:
- an imaging device having pixels arrayed in a matrix, each pixel generating an electric signal corresponding to the amount of radioactive ray incident on the pixel;
a measuring device measuring radiation intensity that represents radiation dose per unit time of the incident radioactive rays;
a detection device detecting an end of radiation from the radiation source on determining that the measured radiation intensity began to decrease;
a timing device for deciding reading start time to start a reading operation for reading out the electric signals from the pixels as radiographic image data such that an interval between detection of the end of radiation and start of the reading operation is variable, on the basis of a gradient of a declivity in time curve of the radiation intensity decreasing in the end of radiation; and
a control device for controlling the imaging device to stop accumulating the electric signals and start the reading operation at the reading start time decided by the timing device after the end of radiation is detected by the detection device.
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Accused Products
Abstract
An x-ray image detector monitors the intensity of incident x-rays to detect an end of radiation from an x-ray source when the x-ray intensity decreases to a threshold level or less. The x-ray intensity gets down to zero with a variable time lag from the start of decreasing, called radiation wave tail. Depending on the gradient of declivity in time curve of the decreasing x-ray intensity, calculated at the time when the end of radiation is detected, the x-ray image detector decides a delay time from the end-of-radiation detection time to a reading start time to start reading signal charges from the image detector. Thus, the reading start time may be adjusted to the point when the x-ray intensity gets down to zero, which will improve S/N ratio and prevent shading artifacts.
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Citations
14 Claims
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1. A radiographic image detector for detecting a radiographic image from radioactive rays projected from a radiation source, the radiographic image detector comprising:
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an imaging device having pixels arrayed in a matrix, each pixel generating an electric signal corresponding to the amount of radioactive ray incident on the pixel; a measuring device measuring radiation intensity that represents radiation dose per unit time of the incident radioactive rays; a detection device detecting an end of radiation from the radiation source on determining that the measured radiation intensity began to decrease; a timing device for deciding reading start time to start a reading operation for reading out the electric signals from the pixels as radiographic image data such that an interval between detection of the end of radiation and start of the reading operation is variable, on the basis of a gradient of a declivity in time curve of the radiation intensity decreasing in the end of radiation; and a control device for controlling the imaging device to stop accumulating the electric signals and start the reading operation at the reading start time decided by the timing device after the end of radiation is detected by the detection device. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A control method for a radiographic image detector for detecting a radiographic image from radioactive rays projected from a radiation source, the radiographic image detector having pixels arrayed in a matrix, each pixel accumulating an electric signal corresponding to the amount of radioactive ray incident on the pixel, the method comprising the steps of:
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measuring radiation intensity that represents radiation dose per unit time of the radioactive rays incident on the radiographic image detector; determining whether the measured radiation intensity began to decrease or not; detecting an end of radiation from the radiation source when it is determined that the measured radiation intensity began to decrease; determining a gradient of a declivity in time curve of the radiation intensity decreasing in the end of radiation; deciding on the basis of the gradient a reading start time to start reading the electric signals from the pixels as radiographic image data such that an interval between detection of the end of radiation and start of the reading operation is variable; and stopping accumulating the electric signals in the pixels and starting reading the electric signals from the pixels at the decided reading start time.
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Specification