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EP-4435477-B1 - X-RAY DETECTOR COMPRISING AEC SENSOR, AND OPERATING METHOD THEREFOR

EP4435477B1EP 4435477 B1EP4435477 B1EP 4435477B1EP-4435477-B1

Inventors

  • KIM, SANGUK

Dates

Publication Date
20260506
Application Date
20221221

Claims (15)

  1. An X-ray detector comprising: a plurality of photodetection elements (110) including a plurality of pixels and configured to detect X-rays; an automatic exposure control, AEC, sensor array (120) configured to detect X-rays that have passed through an object and to quantify a dose of the detected X-rays as a signal value and output the signal value; a memory storing one or more instructions; and at least one processor configured to execute the one or more instructions stored in the memory, characterized in that the at least one processor is configured to: obtain a one-dimensional, 1D, image (400), based on the signal value output through the AEC sensor array, identify a symmetric point from the 1D image, based on a signal value for each pixel of the 1D image, and adjust respective locations of a plurality of AEC sensing areas so that the plurality of AEC sensing areas are symmetrical to each other with respect to the identified symmetric point.
  2. The X-ray detector of claim 1, wherein the AEC sensor array is a line-type sensor array including a plurality of photodetection elements arranged in a first direction among the plurality of photodetection elements included in the X-ray detector.
  3. The X-ray detector of claim 1, wherein the AEC sensor array includes a plurality of AEC sensors, and at least one AEC sensor among the plurality of AEC sensors is located within the plurality of AEC sensing areas.
  4. The X-ray detector of claim 1, wherein the at least one processor is configured to calculate an average value of differences between a signal value of each of a plurality of pixels included in the 1D image and respective signal values of pixels spaced apart from each of the plurality of pixels included in the 1D image, search for a minimum value among the average values respectively calculated for the plurality of pixels, and identify, among the plurality of cells, a location of a pixel having the minimum value as the symmetric point.
  5. The X-ray detector of claim 1, wherein the at least one processor is configured to detect a plurality of edge points based on the signal values of the plurality of pixels of the 1D image, obtain an edge point pair among the detected plurality of edge points, calculate a location of a center point of the obtained edge point pair, and identify the location of the calculated center point as the symmetric point.
  6. The X-ray detector of claim 1, wherein the AEC sensor array includes a first AEC sensor array and a second AEC sensor array arranged in the form of parallel lines, and the at least one processor is configured to identify the symmetric point by using a sum of a signal value for each pixel of a first 1D image obtained using the first AEC sensor array and a signal value for each pixel of a second 1D image obtained using the second AEC sensor array.
  7. The X-ray detector of claim 1, wherein the AEC sensor array includes a plurality of arrays, and the at least one processor is configured to identify a plurality of symmetric points from the 1D image obtained using a plurality of AEC sensor arrays, obtain a symmetric axis by connecting the plurality of symmetric points to each other, and change respective locations of the plurality of AEC sensing areas so that the plurality of AEC sensing areas arranged on left and right sides of the symmetric axis are symmetrical to each other about the symmetric axis.
  8. The X-ray detector of claim 1, wherein the at least one processor is configured to obtain a location of a center point of the plurality of AEC sensing areas arranged on the left and right sides of the identified symmetric point, and change respective locations of the plurality of AEC sensing areas such that the location of the center point is consistent with the location of the symmetric point.
  9. A method of operating an X-ray detector including an automatic exposure control, AEC, sensor, the method comprising: detecting, by using an AEC sensor array, X-rays that have passed through an object, and being characterized by obtaining a one-dimensional, 1D, image by quantifying a dose of the detected X-rays into a signal value; identifying a symmetric point from the 1D image, based on a signal value for each pixel of the 1D image; and adjusting respective locations of a plurality of AEC sensing areas so that the plurality of AEC sensing areas are symmetrical to each other with respect to the identified symmetric point.
  10. The method of claim 9, wherein the identifying of the symmetric point comprises: calculating an average value of differences between a signal value of each of a plurality of pixels included in the 1D image and respective signal values of pixels spaced apart from each of the plurality of pixels included in the 1D image; searching for a minimum value among average values respectively calculated for the plurality of pixels; and identifying a location of a pixel having the minimum value among the plurality of pixels as the symmetric point.
  11. The method of claim 9, wherein the identifying of the symmetric point comprises: detecting a plurality of edge points, based on the signal values of the plurality of pixels of the 1D image; obtaining an edge point pair from among the plurality of detected edge points; calculating a location of a center point of the obtained edge point pair; and identifying the location of the center point as the symmetric point.
  12. The method of claim 9, wherein the AEC sensor array includes a first AEC sensor array and a second AEC sensor array arranged in the form of parallel lines, and the identifying of the symmetric point comprises identifying the symmetric point by using a sum of a signal value for each pixel of a first 1D image obtained using the first AEC sensor array and a signal value for each pixel of a second 1D image obtained using the second AEC sensor array.
  13. The method of claim 9, wherein the identifying of the symmetric point comprises: identifying a plurality of symmetric points from the 1D image obtained using a plurality of AEC sensor arrays; and obtaining a symmetric axis by connecting the plurality of symmetry points to each other, and the adjusting of the locations of the plurality of AEC sensing areas comprises changing the locations of the plurality of AEC sensing areas such that the plurality of AEC sensing areas arranged on left and right sides of the symmetric axis are symmetrical to each other about the symmetric axis.
  14. The method of claim 9, wherein the adjusting of the respective locations of a plurality of AEC sensing areas comprises: obtaining a location of a center point of the plurality of AEC sensing areas arranged on the left and right sides of the identified symmetric point; and changing the locations of the plurality of AEC sensing areas so that the location of the obtained center point is consistent with the location of the symmetric point.
  15. A computer program product including a computer-readable storage medium, the computer-readable storage medium comprising instructions readable by an X-ray detector including an automatic exposure control, AEC, sensor to perform the operations of: detecting, by using an AEC sensor array, X-rays that have passed through an object, and being characterized by obtaining a one-dimensional, 1D, image by quantifying a dose of the detected X-rays into a signal value; identifying a symmetric point from the 1D image, based on a signal value for each pixel of the 1D image; and adjusting respective locations of a plurality of AEC sensing areas so that the plurality of AEC sensing areas are symmetrical to each other with respect to the identified symmetric point.

Description

Technical Field The disclosure relates to an X-ray detector including an automatic exposure control (AEC) sensor, and a method of operating the X-ray detector. In detail, the disclosure relates to an X-ray detector that corrects an AEC sensing area based on an image representing a dose of X-rays detected using an AEC sensor array, and a method of operating the X-ray detector. Background Art X-ray detectors obtain an image in an X-ray imaging apparatus. X-ray detectors detect X-rays emitted by an X-ray source (or an X-ray tube) and transmitted through an object (e.g., a patient), convert the detected X-rays into an electrical signal, and output the electrical signal to thereby generate an X-ray image. As imaging automation progresses, room X-ray imaging apparatuses (Room DR) help a radiologist's work by additionally including various automation functions, such as automatic source-detector alignment or automatic exposure control (AEC), and reduce quality deviations in captured images. AEC sensors are installed in the bucky of a room X-ray apparatus (Room DR) to detect the dose of X-rays emitted by an X-ray source in real time, convert an accumulated dose value into a voltage value, and output the voltage value. When the output voltage value exceeds a preset threshold, x-ray detectors may transmit an X-ray blocking signal to the X-ray source to block X-ray emission from the X-ray source. Accordingly, despite various photographing protocols, differences between patients, or differences between body parts to be photographed, the dose of X-rays reaching the X-ray detector may be constantly maintained, and an image quality may be maintained uniformly. General AEC sensors are manufactured in the form of an ion chamber using air, and are placed on a front side of an X-ray detector. General AEC sensors operate in a method of applying an appropriate voltage to an ion chamber, collecting air ions ionized by X-rays, converting the amount of charge due to the air ion collection into a voltage, and amplifying and accumulating such voltages. Ion chamber AEC sensors operate by comparing a voltage value increasing in real time with a voltage value corresponding to a target dose and, when the two voltage values are consistent with each other, stopping X-ray emission by an X-ray source. In order for an AEC sensor to operate an AEC function without any problems, a selected body part to be photographed by the AEC sensor must be accurately positioned. In the case of a room X-ray imaging apparatus (Room DR), an AEC sensor panel is located within the bucky, is thus accurately aligned with an X-ray detector, and is also aligned with an X-ray source by using, for example, an electronic control system or a mechanical matching method. In addition, because a patient's anatomical area must also be matched to an AEC sensor, cross-shaped light radiation is used. In particular, in the case of a stand bucky, an AEC sensor area is marked on the surface of the stand bucky, so a radiologist positions a patient by referring to the AEC sensor area. That is, in order to use an AEC function, it is very important to align an X-ray source, a patient, an AEC sensor, and an X-ray detector with each other. Recently, mobile X-ray detectors or portable X-ray detectors have become popular and are widely used. Mobile X-ray detectors including an AEC sensor are located at the back of a patient during X-ray imaging, so a radiologist should check the outline of the X-ray detector and the patient's anatomy by eye. Therefore, in the case of mobile X-ray detectors, the alignment between the X-ray source-patient-AEC sensor-X-ray detector may not be accurately performed. The patent publication EP2623032 A1 discloses a radiation-imaging system which is able to define a dose-measurement region at the location of the body part to be examined - even when accurate alignment between the examined body part and the image detector is hard to achieve. Disclosure Technical Solution To address the above-described technical problems, an aspect of the disclosure provides an X-ray detector that includes an automatic exposure control (AEC) sensor and corrects an AEC sensing area. The X-ray detector according to an embodiment of the disclosure may include a plurality of photodetection elements including a plurality of pixels and configured to detect X-rays, an AEC sensor array configured to detect X-rays that have passed through an object and to quantify a dose of the detected X-rays as a signal value and output the signal value, a memory storing one or more instructions, and at least one processor configured to execute the at least one instruction stored in the memory. The at least one processor may be configured to obtain a 1D image, based on the signal value output through the AEC sensor array. The at least one processor may be configured to identify a symmetric point from the 1D image, based on a signal value for each pixel of the 1D image. The at least one processor may be con