JP2012085173A - Radiographic image reading apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiographic image reading apparatus that can increase the speed of image reading and can moderate a resolution drop.SOLUTION: A radiographic image reading apparatus 10 includes: a radiographic sensor 11 including an image detection section in which first pixels connected to odd-numbered gate lines and second pixels connected to even-numbered gate lines are arranged alternately in row and column directions; a gate drive circuit 12 for sequentially applying drive voltages to the gate lines; a reading circuit 14 for reading pixel data from the pixels connected to a selected gate line; and an image updating/synthesis circuit 16 for, as to the image data sequentially acquired by the reading circuit 14, updating original image data in pixel portions where new image data is available, and displaying original image data synthesized with image data updated in adjacent portions in pixel portions where new image data is unavailable.

Description

  Embodiments described herein relate generally to a radiation image reading apparatus capable of reading not only a still image but also a moving image.

  As a new generation X-ray diagnostic detector, a radiation image reading apparatus using an active matrix has been attracting much attention. By irradiating the radiation image reading apparatus with X-rays, an X-ray image or a real-time X-ray image is output as a digital signal. In addition, since it is a flat solid detector, it is highly expected in terms of image quality and stability. For this reason, many universities and manufacturers are working on research and development.

  Radiation image reading apparatuses are roughly classified into two methods, a direct method and an indirect method.

  The direct method is a method in which X-rays are directly converted into a charge signal by a photoconductive film such as a-Se and led to a charge storage capacitor.

  One indirect method is a method in which X-rays are received by a phosphor layer and converted into visible light, and then the visible light is converted into signal charges by an a-Si photodiode or the like and led to a charge storage capacitor.

  Many of the radiation image reading apparatuses currently in practical use employ the indirect method.

  A conventional indirect radiation image reading apparatus includes a fluorescence conversion film that converts incident X-rays into fluorescence, and an image detection unit that converts the fluorescence into image information using an electrical signal.

  FIG. 8 shows an equivalent circuit diagram of an image detection unit in a conventional indirect radiation image reading apparatus.

  In this image detection unit, a signal of a vertical wiring is supplied to each pixel 1 composed of a TFT switch 3, a photodiode 8, and a capacitor 9 made of a thin film transistor (hereinafter referred to as "TFT"). A readout line (signal line) 2 and a lateral wiring gate line 4 are connected through a TFT switch 3, and a signal readout line 2 is further connected to an integrating amplifier 5. The signal readout line 2 reads out the signal of the pixel group in the column connected to the TFT switch 3, and the gate line 4 controls on / off of the TFT switch 3.

  In this radiographic image reading apparatus, a two-dimensional image can be read by sequentially turning on the gate lines 4 and reading the electric signals of the pixels 1 connected to the gate lines 4 through the signal read lines 2. .

  FIG. 9 shows an example of an image reading method based on a conventional non-binning method (reading independently without combining a plurality of pixels).

  In this readout method, the gate lines 4 are turned on line by line, whereby the pixels 1 connected to each signal readout line 2 are sequentially read out by the lead-out IC shown in FIG. That is, when the gate line 4a is turned on, only the pixel 1a connected to the gate line 4a and the signal readout line 2a is read out from the signal readout line 2a.

  For this reason, in order to read out the image of the entire image detection unit, the image signal is read out in order of the gate lines 4 line by line, and the time for reading out the image is limited by the time required for the reading.

  In the non-binning readout method, the scanning time of the gate line 4, the processing time of the image data from the pixel 1, the transfer time, and the like are limited, and the update rate (frame rate) of the moving image is determined.

  For this reason, when the effective area of the image is large, the number of pixels and the number of gate lines increase accordingly, and the frame rate decreases.

  Therefore, to increase the image reading speed, it is necessary to speed up this operation or reduce the number of pixels, that is, the number of gate lines.

  Next, FIG. 10 shows an example of an image reading method by binning that reads out by combining a plurality of pixels.

  In this method, two gate lines are simultaneously turned ON, and the image data of the upper and lower two pixels are read out as a signal added to the readout IC shown in FIG. That is, when the two gate lines 4a and 4b are turned on, for example, in the signal readout line 2a, the sum signal of the image data of the pixels 1a and 1b connected to the two gate lines 4a and 4b turned on is read out. It is.

  In this method, the scanning speed of the gate line 4 is doubled, but if it is left as it is, only the number of pixels in the vertical direction of the image is halved and the image is deformed.

  Therefore, as shown in FIG. 11, when the two gate lines 4a and 4b are turned on, not only the signal from the pixel connected to one signal readout line 2a but also the signal adjacent to the signal readout line 2a. A method is also employed in which signals from pixels connected to the readout line 2b are added together and an image signal is processed with four pixels as one pixel.

  As a result, the gate scanning speed is doubled, the number of image data is ¼, and the frame rate can be increased.

  However, in this image reading method based on Binning, since four pixels are processed as one pixel, the spatial resolution is lowered.

JP 2009-128023 A

  When a radiographic image reading apparatus reads not only a still image but also a moving image, a detection area is large and a moving image is required to have a high speed.

  However, as described above, in the conventional non-binning readout method, since readout is performed for each gate line, the scanning time of the gate line, the processing time of image data from the pixels, the transfer time, and the like are limited, and the speed at which the image is read out. Can not raise.

  On the other hand, in the conventional image reading method based on Binning, since a plurality of pixels are read out simultaneously, the image reading speed can be increased, but the spatial resolution is lowered.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a radiation image reading apparatus that can improve the image reading speed and can alleviate a decrease in resolution.

  In order to achieve the above-described object, the radiation image reading apparatus according to the present embodiment includes a plurality of two-dimensional substrates including pixels each including an element that converts incident radiation into an electrical signal and a TFT switch that reads the converted electrical signal. The plurality of pixels arranged above and each of the plurality of pixels extends in one direction out of a plurality of gate lines extending in one of a row direction and a column direction, and a direction orthogonal to the extending direction of the gate lines. The plurality of pixels are connected to one of the signal readout lines via the TFT switch, and the plurality of pixels are connected to the first pixel connected to the odd-numbered gate line and the even-numbered gate line. A plurality of second pixels, and a plurality of the radiation sensors including an image detection unit in which the first pixels and the second pixels are alternately and adjacently arranged in a row direction and a column direction, A gate driving circuit that sequentially applies a driving voltage to the gate line, and a reading circuit that reads image data via the signal reading line for a plurality of pixels connected to the gate line to which the driving voltage is applied; It is characterized by providing.

The schematic diagram which shows the structure of the radiographic image reading apparatus which concerns on embodiment. The perspective view which shows an example of the radiation sensor used for the radiographic image reading apparatus of FIG. FIG. 3 is an equivalent circuit diagram of the image detection unit in FIG. 2. FIG. 2 is a plan view illustrating an example of a gate driving circuit and a reading circuit in FIG. 1. The circuit diagram which shows the connection relation of the pixel and TFT switch in embodiment. FIG. 5 is a circuit diagram showing a read state of odd-numbered gate lines in the embodiment. The circuit diagram which shows the synthetic | combination state of the odd-numbered gate line and the even-numbered gate line in embodiment. The equivalent circuit diagram of the image detection part in the conventional indirect type radiographic image detector. Schematic which shows the image read-out method by the conventional non-binning. Schematic which shows the image reading method by the conventional Binning. Schematic which shows the other image reading method by the conventional Binning.

  Hereinafter, embodiments will be described with reference to the drawings.

(Overall configuration of radiation image reader)
FIG. 1 shows a radiation image reading apparatus according to the present embodiment.

  The radiation image reading apparatus 10 is two-dimensionally arranged in a radiation sensor 11 having a phosphor layer that converts incident X-rays into light and an image detection unit that converts incident light into an electrical signal, and an image detection unit. A gate drive circuit 12 that sequentially applies a drive voltage to each gate line for each pixel, a drive control circuit 13 that generates a drive signal that determines scan timing in the column direction for the gate drive circuit 12, and a selected gate line A reading circuit 14 that reads an electrical signal of a connected pixel, a reading control circuit 15 that generates a reading signal that determines the reading timing in the reading circuit 14, and image updating or image synthesis of image data sequentially obtained by the reading circuit 14 An image updating / combining circuit 16 for displaying the image data and a display device 17 for displaying the image data.

(Radiation sensor 11)
FIG. 2 shows an example of a specific configuration of the radiation sensor 11.

  The radiation sensor 11 includes a fluorescence conversion film 23 that converts incident X-rays 21 into fluorescence, and an image detection unit 25 that converts the fluorescence into image information using an electrical signal.

  The image detection unit 25 is formed by providing a circuit layer 29 on which a large number of pixels 1 including photodiodes and TFT switches 3 are arranged on a holding substrate 27 mainly composed of a glass substrate.

  FIG. 3 shows an equivalent circuit of the image detection unit 25.

  The pixel 1 includes a TFT switch, a photodiode, and a capacitor as in FIG. 8, but the pixel 1x connected to the odd-numbered gate line 4x and the pixel 1y connected to the even-numbered gate line 4y are alternately arranged. Has been.

  Further, the lower end of the signal readout line 2 is connected to the integrating amplifier 5 shown in FIG. 4, and the left end of the gate line 4 is connected to a specific signal line of the gate driver 31 shown in FIG.

(Gate driving circuit 12, reading circuit 14)
FIG. 4 shows an example of a specific configuration of the gate driving circuit 12 and the reading circuit 14 of FIG.

  The gate driving circuit 12 includes a gate driver 31 and a row selection circuit 33, and the reading circuit 14 includes an integrating amplifier 5, an A / D (analog / digital) converter 35, and a driver 37.

  The gate driver 31 has a function of sequentially changing the voltages of a large number of gate lines 4 connected to the radiation sensor 11 when receiving a signal from the outside. A row selection circuit 33 is connected to the gate driver 31.

  The row selection circuit 33 has a function of sending a signal to the corresponding gate driver 31 according to the scanning direction of the X-ray image, and is connected to the drive control circuit 13 of FIG.

  Further, the integrating amplifier 5 is connected to the signal readout line 2 in FIG. 3 on a one-to-one basis, and amplifies a charge signal transmitted through the signal readout line 2. The integrating amplifier 5 is connected to the driver 37 via the A / D converter 35.

  The driver 37 is connected to the reading control circuit 15 of FIG. 1, and reads a signal digitized by the A / D converter 35 by a reading signal from the reading control circuit 15.

(Image update / synthesis circuit 16)
The image updating / synthesizing circuit 16 updates the image data for the pixel portion from which new image data is obtained among the image data sequentially obtained by the reading circuit 14 for all the two-dimensionally arranged pixel portions. . In addition, the pixel portion for which image data is not newly obtained is left as the original image data, or the original image data signal and the data signal updated in the adjacent portion are synthesized. Further, the image data of any pixel updated at an adjacent position can be combined with the original frame data by performing weighting processing.

(Pixel data readout method)
5 to 7 show an example of a pixel data reading method according to this embodiment.

  First, a drive control circuit 13 (see FIG. 1) for determining the scan timing of the gate lines 4 in the column direction generates drive signals for sequentially driving the odd-numbered gate lines 4x, and the gate drive circuit 12 (FIG. 1) based on the drive signals. (See) applies a driving voltage to the odd-numbered gate lines 4x sequentially. As a result, image data from the pixels connected to the odd-numbered gate lines 4x are sequentially read out.

  In FIG. 5, the position of the image data acquired from the pixel 1x connected to the odd-numbered gate line 4xa is indicated by a dotted line.

  Next, the drive control circuit 13 generates drive signals for sequentially driving the even-numbered gate lines 4y, and the gate drive circuit 12 sequentially applies drive voltages to the even-numbered gate lines 4y based on the drive signals. As a result, as shown in FIG. 6, the image data from the pixel position (position A) connected to the even-numbered gate line 4y is sequentially read out.

  Further, the drive control circuit 13 generates drive signals for sequentially driving the odd-numbered gate lines 4x, and the gate drive circuit 12 sequentially applies drive voltages to the odd-numbered gate lines 4x based on the drive signals. As a result, as shown in FIG. 7, the image data from the pixel position (position B) connected to the odd-numbered line is newly acquired, and the original image data at the position B is obtained by the image update / synthesis circuit 16. Update.

  At this time, the data of the pixel position (position A) of the even line is displayed at the position B adjacent to the data of the original frame by displaying the image data of the original frame or by the image update / synthesis circuit 16. The image data of any pixel may be combined and displayed on the display device 17 (see FIG. 1). Further, the image data of any pixel updated at the adjacent position B may be combined with the original frame data by performing weighting processing.

  As a result, checkered pattern image data is alternately read. In addition, pixels that have not been read accumulate data twice, and the image information is proportional to the dose of X-rays or the like.

(Effect of the radiation image reading apparatus according to the present embodiment)
(1) It is possible to provide a radiation image reading apparatus that can improve the image reading speed and can alleviate a decrease in resolution.

(2) By alternately allocating the image to the top and bottom of the gate line with respect to the scanning of the gate line, noise in the gate line direction and horizontal stripe noise peculiar to the image detection unit can be reduced.

(3) The image reading speed can be improved by dividing the image data in the pixel into position A and position B and alternately reading out every other gate line. In addition, the spatial resolution is lowered in the conventional image reading method by binning, whereas the spatial resolution is not lowered in the present method, so that the effect of increasing the frame rate is sufficiently high. In one pixel, the frame is updated once every two frames and the resolution of the time axis is reduced. However, in the field of medical images such as X-rays, the process of averaging the movement and noise of the subject on the time axis In practice, it is not a problem.

(4) For a portion where the frame has not been updated, the time is obtained by combining the updated image data of any adjacent pixel or further combining the image data of the pixel by performing weighting processing. A reduction in the resolution of the axis can be suppressed.

  In the above-described embodiment, an example of the indirect system in which the photodiode 8 is provided as the radiation sensor 11 is shown. However, the X-ray is directly converted into a charge signal by a photoconductive film such as a-Se, and charge accumulation is performed. The same method can be applied to a direct system that leads to a capacitor for use.

1, 1a, 1b: pixel 1x: pixel (first pixel)
1y: Pixel (second pixel)
2, 2a, 2b: signal readout line 3: TFT switch 4, 4a, 4b: gate line 4x, 4xa: odd gate line 4y: even gate line 5: integration amplifier 8: photodiode 9: capacitor 10: radiation image reader DESCRIPTION OF SYMBOLS 11: Radiation sensor 12: Gate drive circuit 13: Drive control circuit 14: Reading circuit 15: Reading control circuit 16: Image update and composition circuit 17: Display device 21: Incident X-ray 23: Fluorescence conversion film 25: Image detection part 27 : Holding substrate 29: Circuit layer 31: Gate driver 33: Row selection circuit 35: A / D converter 37: Driver

Claims (3)

A plurality of pixels including an element that converts incident radiation into an electrical signal and a TFT switch that reads the converted electrical signal are two-dimensionally arranged on the substrate, and each of the plurality of pixels has a row direction or a column. One of a plurality of gate lines extending in one direction and one of a plurality of signal readout lines extending in a direction orthogonal to the extending direction of the gate line and the TFT switch And the plurality of pixels further includes a first pixel connected to the odd-numbered gate line and a second pixel connected to the even-numbered gate line. A radiation sensor including an image detection unit in which the second pixels are alternately arranged in the row direction and the column direction; and
A gate driving circuit for sequentially applying a driving voltage to the plurality of gate lines;
For a plurality of pixels connected to the gate line to which the driving voltage is applied, a reading circuit that reads image data via the signal reading line;
A radiation image reading apparatus comprising:   The radiographic image reading apparatus according to claim 1, wherein the gate driving circuit sequentially applies a driving voltage to each of the plurality of gate lines every odd number and every even number.   At any point in time when image data is read by the reading circuit, the original image data is updated to the new image data for the pixel portion for which new image data has been acquired by the reading circuit, and new image data is acquired. 3. The radiation image reading apparatus according to claim 2, further comprising an image update / synthesis circuit that synthesizes an original image data signal and a data signal updated in an adjacent portion for a pixel portion that is not present. .

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