JP2004261209A - Radiation imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable an observer to read a taken image by acquiring a precise X-ray image by eliminating the artifact caused by the incidence of excessive X rays even if excessive X rays like the halation due to incidence of direct X rays on a part of the pixels of an X-ray plane detector when an X-ray image by means of continuous fluoroscopy is taken using a radiation imaging apparatus. <P>SOLUTION: Leak signal data is acquired by the empty reading of signal charge prior to reading the signal charge from a pixel array of the X-ray plane detector and X-ray image data is corrected on the basis of the leak signal charge. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a radiation imaging apparatus, and more particularly to a radiation imaging apparatus that performs correction based on leak signal information on image data during continuous fluoroscopy.
[0002]
[Prior art]
The radiation image capturing apparatus obtains X-ray image data of the subject by irradiating the subject with X-rays and detecting transmitted X-rays with a flat panel detector. The X-ray flat panel detector includes a pixel array in which detection elements for converting an X-ray image signal into signal charges are two-dimensionally arranged, a signal readout line provided for each pixel column, and a detection element provided for each detection element. Switching means for closing and opening signal readout from each detection element via a signal readout line, and controlling the switching means to change the signal charge of the detection element included in the row for each row of the pixel array. The data is read out (for example, see Non-Patent Document 1).
[0003]
Such an X-ray flat panel detector has been used for capturing an X-ray image in which X-ray irradiation and signal reading do not overlap in time, such as pulse fluoroscopy.
[0004]
[Non-patent document 1]
Edited by Takeshi Iinuma and Norio Tateno, "X-ray imaging"
Published by Corona on June 15, 2001 (pages 86 to 89, 3.57, 3.60, 3.61)
[0005]
[Problems to be solved by the invention]
However, in a conventional X-ray flat panel detector, when performing X-ray imaging in which X-ray irradiation and signal readout such as continuous fluoroscopy temporally overlap with each other, excessive X-rays due to X-rays directly enter the pixel array. Excessive signal charges exceeding the signal capacity are accumulated in the detection elements in the incident area, and when the signals are read from the detection elements in each row of the pixel array, the excessive signal charges leak to the signal readout line, and the signal passing through the area The leakage charge is superimposed on the signal of the detection element belonging to the pixel column read via the read line.
[0006]
Thus, for example, if there is a portion in the pixel array where the X-rays do not hit, such as the shadow of an X-ray aperture, the apparent signal amount differs between the portion where the leaked charge is superimposed and the portion where it is not, and the column direction , An artifact (false image) occurs continuously.
[0007]
If such an artifact occurs, a correct X-ray image cannot be obtained, and it becomes difficult for the observer to interpret the captured image.
[0008]
The present invention has been made in view of the above circumstances, and when performing X-ray imaging by continuous fluoroscopy, excessive X-rays due to X-rays directly enter some of the pixels of the X-ray flat panel detector. However, an object of the present invention is to provide a radiographic image capturing apparatus that eliminates artifacts caused thereby, acquires a correct X-ray image, and allows a viewer to easily read a captured image.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a radiographic imaging apparatus according to the present invention described in claim 1 includes an X-ray source for irradiating an X-ray to a subject, and a signal charge for the X-ray radiated from the X-ray source. A pixel array in which detection elements to be converted into two-dimensional array are arranged, and for each row of the pixel array, signal charges of the detection elements included in the row are read out via a readout line during X-ray irradiation and output as image data An X-ray flat panel detector having a read-out unit that reads out signal charges of the pixel array before the correction of image data of each frame constituting a continuous fluoroscopic image. An X-ray flat panel detector for outputting at least one row of leakage signal information leaking to a signal readout line; and correcting the correction data for one row of the X-ray flat panel detector based on the leak signal information output from the reading unit. Remember Correction data storage means, image data correction means for correcting the image data by subtracting the correction data stored in the correction data storage means from the image data of each row of the pixel array output from the reading section, Image display means for displaying a continuous perspective image based on the image data corrected by the image data correction means.
[0010]
According to the first aspect of the present invention, when the X-rays emitted from the X-ray source enter the X-ray flat panel detector, the X-rays are converted into signal charges by each detection element of the pixel array of the X-ray flat panel detector. . After that, prior to correcting the image data of each frame constituting the continuous fluoroscopic image, the readout unit reads the signal charges of the pixel array without reading and outputs at least one row of leak signal information. One line of correction data based on the leak signal information is stored in the correction data storage unit.
[0011]
The blank reading of the signal charges may be performed for at least one row. However, the blank reading of the signal charges for a plurality of rows may be performed, and the correction data may be calculated based on the leak signal information for the plurality of rows and stored. Good.
[0012]
When the correction data is stored, the reading unit reads, for each row of the pixel array, signal charges (image data before correction) of the detection elements included in the row, and outputs the read signal charges as image data. For this image data, the image data correction means subtracts the correction data from the image data corresponding to each row of the pixel array to correct the image data, and the image display means converts the image based on the image data into one of the continuous perspective images. Display as a frame.
[0013]
As described above, the leak signal information is obtained from the pixel array of the X-ray flat panel detector, and the X-ray image data is corrected based on the leak signal information. Even if a line is incident, artifacts caused by the line can be eliminated to obtain correct image data, and a correct image with the artifact eliminated is displayed, so that the observer can easily read the captured image.
[0014]
According to a second aspect of the present invention, there is provided a pixel array in which an X-ray source for irradiating an object with X-rays and a detection element for converting the X-rays emitted from the X-ray source into signal charges are two-dimensionally arranged. A pixel array which has been subjected to processing for preventing generation of signal charges due to irradiation of X-rays on some pixel rows of the pixel array, and a detection element included in the row for each row of the pixel array. A readout unit for reading out signal charges via a readout line during X-ray irradiation and outputting the image charge as image data, wherein the readout unit reads out image data of each frame forming a continuous fluoroscopic image. An X-ray flat panel detector for reading out signal charges of pixel rows of the pixel array which have been subjected to processing for preventing generation of signal charges due to X-ray irradiation prior to the correction and outputting at least one leak signal information; Out of the reading unit Correction data storage means for storing correction data for one row of the X-ray flat panel detector based on leaked signal information to be obtained, and correction data storage means for converting the image data of each row of the pixel array output from the reading section. Image data correction means for correcting the image data by subtracting the correction data stored in the image data, and image display means for displaying a continuous perspective image based on the image data corrected by the image data correction means. It is characterized by.
[0015]
According to the invention described in claim 2, when the X-rays emitted from the X-ray source enter the X-ray flat panel detector, the X-rays are converted into signal charges by the respective detection elements of the pixel array of the X-ray flat panel detector. You. After that, when reading out the signal of the image data constituting each frame of the continuous fluoroscopic image, the reading unit performs the processing for preventing the generation of the signal charges due to the irradiation of the X-ray in the pixel row (the mask row) in the pixel array. ), And outputs leakage signal information of at least one row. The correction data based on the leak signal information is stored in the correction data calculation means.
[0016]
The reading of the signal charges from the mask row may be performed for at least one row, but the signal charges for a plurality of rows are read, and the correction data is calculated and stored based on the leak signal information for the plurality of rows. Is also good.
[0017]
The reading unit also reads signal charges (image data before correction) from other pixel rows of the pixel array, and outputs the signal charges as image data. For this image data, the image data correction means subtracts the correction data from the image data corresponding to each pixel row of the pixel array to correct the image data, and the image display means converts an image based on the image data to a continuous fluoroscopic image. Are displayed as one frame.
[0018]
As described above, the leakage signal information is obtained by reading out the signal charges of the pixel rows (mask rows) of the pixel array of the X-ray flat panel detector that have been subjected to the processing for preventing the generation of signal charges due to X-ray irradiation. However, since the X-ray image data is corrected based on the leak signal information, even if excessive X-rays due to X-rays are directly incident on a part of the pixel array, artifacts caused by the excessive X-rays are eliminated and correct image data is obtained. Can be obtained, and a correct image in which artifacts are eliminated is displayed, so that the observer can easily read the captured image.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of a radiation image capturing apparatus according to the present invention will be described in detail with reference to the accompanying drawings.
[0020]
FIG. 1 is a block diagram illustrating an overall configuration of a radiation image capturing apparatus 10 to which the first embodiment is applied.
[0021]
The radiation image capturing apparatus 10 includes an X-ray control circuit 12. X-rays are emitted from the X-ray source 16 under the control of the X-ray control circuit 12, the X-rays transmitted through the subject 14 are detected by the X-ray flat panel detector 18, and the X-rays are controlled by the image data acquisition control unit 20. It is stored in the X-ray image memory 22 as line image data.
[0022]
The X-ray image data stored in the X-ray image memory 22 is subjected to leak signal correction by a leak signal correction unit 28 and stored in the corrected image data memory 30, and is displayed on a display monitor 34 via a display control unit 32. Displayed as an image.
[0023]
Note that the X-ray source 16 and the X-ray flat panel detector 18 may be configured to be movable relative to the subject 14 according to the use state of the radiation image capturing apparatus 10.
[0024]
The operation unit 36 is used to operate the radiation image capturing apparatus 10 and includes buttons and switches (not shown). The operation unit 36 controls irradiation / non-irradiation of X-rays, the number of pieces of leak signal information obtained when calculating column correction data, display of image data, and the like. It is configured to be configurable.
[0025]
The image data acquisition control unit 20 acquires the image data output from the X-ray flat panel detector 18 and stores the image data in the X-ray image memory 22. Further, the image data acquisition control unit 20 acquires the leak signal information from the X-ray flat panel detector 18 and stores the leak signal information in the leak signal information memory 24 (described later) before correcting the image data.
[0026]
A column correction data calculation unit 26 is connected to the leak signal information memory 24. The column correction data calculation unit 26 calculates column correction data from the leak signal information stored in the leak signal information memory 24 and stores the column correction data. (Described later).
[0027]
A leakage signal correction unit 28 is connected to the column correction data calculation unit 26. The leakage signal correction unit 28 stores the column correction data stored in the column correction data calculation unit 26 in the X-ray image memory 22. Leakage signal correction is performed by subtracting from the existing X-ray image data. With this correction, image data subjected to leakage signal correction is obtained.
[0028]
The display control unit 32 sets the X-ray image data before the leak signal correction stored in the X-ray image memory 22, the leak signal stored in the leak signal information memory 24, and the corrected image according to the settings of the operation unit 36. An image based on the image data after the leakage signal correction stored in the data memory 30 is configured to be displayed on the display monitor 34.
[0029]
The radiation image capturing apparatus 10 includes a CPU (not shown) in addition to the above, and controls the processing of the radiation image capturing apparatus 10 by the CPU.
[0030]
FIG. 2 shows a main configuration of the X-ray flat panel detector 18. The X-ray flat panel detector 18 is provided with a phosphor layer 42 that emits light when irradiated with X-rays. The phosphor layer 42 is emitted below the phosphor layer 42 on the substrate 40. A pixel array 44 in which detection elements for accumulating electric charges (signal charges) corresponding to light are arranged in a two-dimensional array is provided.
[0031]
Each detection element of the pixel array 44 includes a photodiode 54 and an FET switch 56 as shown in the enlarged view. Further, each detection element is connected to a switch control line 46 provided for each row and a signal read line 48 provided for each column, and the switch control line 46 of each row is connected to a read row selection circuit 50, The signal read lines 48 of each column are connected to a read circuit 52.
[0032]
To read the data of the signal charges of the respective detection elements from the pixel array 44, the read-out row selection circuit 50 turns on only the switches of the pixel rows to be read out and turns off the other switches. The circuit 52 reads signal charges of pixels in each column included in the read target row.
[0033]
When the readout row selection circuit 50 turns off the switches of all the pixel rows and the readout circuit 52 reads the data of the Mth row (data blank reading), leak signal information is obtained.
[0034]
FIG. 3 is a conceptual diagram illustrating the effect of leakage charge superposition. As shown in FIG. 3A, when excessive X-rays are directly incident on a certain region in the pixel array 44 by X-rays, all columns passing through that region are affected by the X-rays. As shown in (b), excessive signal charges are generated and superimposed on the signal charges in each column as leakage charges.
[0035]
Accordingly, by subtracting such leak signal information (leak charge) from the read signal charge, it is possible to perform leak signal correction on image data.
[0036]
Next, the operation of the above embodiment will be described with reference to FIG. FIG. 4 is a time chart of the processing performed by the radiation image capturing apparatus 10, and shows the timing at which the processing of each item is executed.
[0037]
First, prior to acquiring the signal charges (image data before correction), the signal charges in the first to fourth rows are read in an empty state with all the switch control lines 46 of the pixel array 44 closed (OFF). As a result, leak signal information for four rows is acquired and stored in the leak signal information memory 24.
[0038]
Next, the switch control line 46 in the first row is opened (ON) to acquire the signal charge in the first row, and the signal charge is stored in the X-ray image memory 22. Thereafter, the switch control line 46 in the first row is closed (OFF), the switch control line 46 in the second row is opened (ON), and the signal charges in the second row are acquired and stored. Hereinafter, similarly, the acquisition and storage of the signal charge are repeated until the last row (K row in the present embodiment).
[0039]
The column correction data is calculated and stored in parallel with the acquisition of the signal charges (image data before correction). The column correction data is obtained by the column correction data calculation unit 26 averaging the leakage signal information for four rows stored in the leakage signal information memory 24. The obtained column correction data is stored in the column correction data calculation unit 26.
[0040]
In this embodiment, the column correction data is obtained by averaging the leakage signal information for four rows, but the column correction data may be calculated from the leakage signal information of at least one row.
[0041]
When the pre-correction image data is acquired and stored in the X-ray image memory 22, and the column correction data is calculated and stored in the column correction data calculation unit 26, the leak signal correction unit 28 The leak signal is corrected by subtracting the column correction data from the data. This process is performed for each row of the pixel array 44 as shown in FIG.
[0042]
When the above processing is completed, the image data after the leakage signal correction is obtained, and is sequentially stored in the corrected image data memory 30 for each row. The image data stored in the corrected image data memory 30 is displayed as an image on the display monitor 34 under the control of the display control unit 32.
[0043]
The above description describes the processing for one frame that forms a continuous fluoroscopic image, and the above processing is repeatedly performed in the continuous fluoroscopy performed using the radiation image capturing apparatus 10.
[0044]
As described above, in the radiographic image capturing apparatus 10 to which the present exemplary embodiment is applied, prior to the acquisition of image data, all the switch control lines 46 of the X-ray flat panel detector 18 are closed (OFF). Leak signal information is obtained by performing blank reading of the signal charge, and column correction data obtained by averaging the obtained leak signal information is subtracted from the data of each row of the X-ray image data, thereby obtaining the leak signal charge. Make corrections.
[0045]
Therefore, even if excessive X-rays due to X-rays directly enter a part of the pixel array of the X-ray flat panel detector 18, artifacts caused by the X-rays can be eliminated and a correct X-ray image can be obtained. Images can be easily read.
[0046]
Next, a second embodiment of the radiation image capturing apparatus according to the present invention will be described. Note that the overall configuration of a radiographic image capturing apparatus 10 'to which the second embodiment is applied is the same as that of the first embodiment (see FIG. 1), and a description thereof will be omitted.
[0047]
FIG. 5A shows a main configuration of the X-ray flat panel detector 18 'of the radiation image capturing apparatus 10'.
[0048]
The basic configuration of the X-ray flat panel detector 18 'is the same as that of the X-ray flat panel detector 18 shown in FIG. The processing for preventing the generation of signal charges due to X-ray irradiation is performed on two rows (in the embodiment). This process is performed by covering a portion of the phosphor layer 42 corresponding to the pixel row with an X-ray non-transmissive material 60 that does not transmit X-rays, such as lead, as shown in FIG. 5B.
[0049]
In addition, in addition to the above-described method, the process for preventing the generation of signal charges due to the irradiation of X-rays includes, as shown in FIG. 5C, light generated when X-rays enter the phosphor layer 42. May be performed by covering some pixel rows with a light non-transmissive material 62 that does not transmit light, and covering the remaining pixel rows with a light transmissive material 64 that transmits light. Here, colored plastic, glass, metal, or the like can be used as the light non-transmissive material 62, and transparent plastic, glass, or the like can be used as the light transmissive material 64.
[0050]
Next, the operation of the above embodiment will be described with reference to FIG. FIG. 6 shows a time chart of the processing performed by the radiation image capturing apparatus 10 ', similarly to FIG. 4, and shows the timing at which the processing of each item is executed.
[0051]
First, prior to obtaining signal charges (image data before correction), leak signal information is obtained. In the present embodiment, a case will be described in which the first and second rows of the pixel array 44 are masked, and leak signal information is obtained from these two rows.
[0052]
At the start of the process, all the switch control lines 46 of the pixel array 44 are closed (OFF). When the process is started, the switch control line 46 in the first row is opened (ON) to acquire the signal charges in the first row, and the signal charges are stored in the leakage signal information memory 24. Thereafter, the switch control line 46 of the first row is closed (OFF), the switch control line 46 of the second row is opened (ON), the signal charge of the second row is acquired, and the leakage signal is obtained in the same manner as in the first row. The information is stored in the information memory 24.
[0053]
The signal charges read from the first and second rows in this manner become leakage signal information.
[0054]
When the acquisition of the leak signal information is completed, the signal charge (image data before correction) is acquired. This processing is performed on the unmasked pixel rows from the third row to the last row (K row in the present embodiment). The method of acquisition and storage is the same.
[0055]
The column correction data is calculated and stored in parallel with the acquisition of the signal charges. The column correction data is obtained by the column correction data calculation unit 26 averaging the leakage signal information for two rows stored in the leakage signal information memory 24. The obtained column correction data is stored in the column correction data calculation unit 26.
[0056]
In the present embodiment, the column correction data is obtained by averaging the leakage signal information for two rows, but the column correction data depends on the number of masked pixel rows in the pixel array 44. What is necessary is just to calculate from the leak signal information of at least one line or more.
[0057]
Hereinafter, the process of correcting and displaying the X-ray image data is the same as that of the first embodiment, and the description is omitted.
[0058]
Note that the above description describes the processing for one frame forming a continuous fluoroscopic image, and the above processing is repeatedly performed in the continuous fluoroscopy performed using the radiation image capturing apparatus 10 '.
[0059]
As described above, in the radiation image capturing apparatus 10 'to which the present exemplary embodiment is applied, the leakage signal information is acquired by reading out the signal charges in the masked rows of the pixel array 44, and the acquired leakage information is obtained. By correcting the column correction data obtained by averaging the signal information from the data of each row of the X-ray image data, the correction of the leakage charge is performed.
[0060]
Therefore, as in the case of the first embodiment, even if excessive X-rays due to X-rays are directly incident on a part of the pixel array of the X-ray flat panel detector 18 ', artifacts caused thereby are eliminated. A correct X-ray image can be acquired, and the observer can easily read the captured image.
[0061]
In the first and second embodiments described above, the acquisition of the leak signal information from the X-ray flat panel detector is performed prior to the reading of the signal charge (image data before correction). The acquisition of the information may be performed after the signal charge is read.
[0062]
For example, in the first embodiment, after reading out signal charges from the first row to the Kth row of the X-ray flat panel detector 18 and storing them in the X-ray image memory 22 as X-ray image data, all pixel rows are read out. Is turned off, the leak signal information is obtained by reading the data from the first row to the fourth row (reading empty), and the column correction data is calculated based on the leak signal information to obtain the X-ray image data. Can be corrected.
[0063]
In the second embodiment, the (K-1) th row and the Kth row of the X-ray flat panel detector 18 'are used as mask rows, and the mask rows are subjected to processing for preventing generation of signal charges due to X-ray irradiation. After reading out the signal charges from the first row to the (K-2) th row and storing them as X-ray image data, the data of the (K-1) th row and the Kth row are obtained and used as leakage signal information. The X-ray image data can be corrected by calculating the column correction data based on the leak signal information.
[0064]
In the first and second embodiments, the case where an image based on the image data after the correction is displayed on the display monitor 34 has been described. May be displayed so that the image can be compared with the image based on the corrected image data.
[0065]
Further, in the first and second embodiments, the case where the output of the image data corrected for the leakage charge is displayed as an image on the display monitor 34 is described. A device may be provided to record a continuous fluoroscopic image as image data so that the image can be repeatedly displayed.
[0066]
【The invention's effect】
As described above, according to the present invention, when capturing an X-ray image by continuous fluoroscopy, even if excessive X-rays due to X-rays are directly incident on a part of the pixel array of the X-ray flat panel detector. Thus, it is possible to eliminate the artifacts caused thereby and obtain correct image data, and it is possible for the observer to easily read the photographed image.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an overall configuration of a radiation image capturing apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a main configuration of an X-ray flat panel detector according to the first embodiment of the present invention.
FIG. 3 is a conceptual diagram showing an influence of leakage charge superposition according to the first embodiment of the present invention.
FIG. 4 is a time chart showing processing in the radiographic image capturing apparatus according to the first embodiment of the present invention.
FIG. 5 is a diagram showing a main configuration of an X-ray flat panel detector according to a second embodiment of the present invention.
FIG. 6 is a time chart showing processing in a radiographic image capturing apparatus according to a second embodiment of the present invention.
[Explanation of symbols]
10, 10 ': radiation image pickup device, 18, 18': X-ray flat panel detector, 22: X-ray image memory, 24: leakage signal information memory, 30: corrected image Data memory, 34 display monitor, 42 phosphor layer, 44 pixel array, 46 switch control line, 48 signal readout line, 60 non-transparent X-ray material , 62: light non-transmitting material, 64: light transmitting material

Claims (2)

An X-ray source for irradiating the subject with X-rays;
A pixel array in which detection elements for converting X-rays emitted from the X-ray source into signal charges are two-dimensionally arranged, and for each row of the pixel array, the signal charges of the detection elements included in the row are irradiated with X-rays. An X-ray flat panel detector having a read-out unit for reading out the image data via a read-out line and outputting the image data as image data, wherein the read-out unit reads out the pixel data before correcting the image data of each frame constituting a continuous fluoroscopic image. An X-ray flat panel detector for outputting at least one row of leakage signal information leaking from the detection element to the signal readout line by reading the signal charges of the array in an empty manner;
Correction data storage means for storing correction data for one row of the X-ray flat panel detector based on the leak signal information output from the reading unit;
Image data correction means for correcting the image data by subtracting the correction data stored in the correction data storage means from the image data of each row of the pixel array output from the reading unit,
Image display means for displaying a continuous perspective image based on the image data corrected by the image data correction means,
A radiographic imaging apparatus comprising: An X-ray source for irradiating the subject with X-rays;
A pixel array in which detection elements for converting X-rays emitted from the X-ray source into signal charges are arranged two-dimensionally, and signal charges are generated by irradiating X-rays to some pixel rows of the pixel array. A pixel array that has been subjected to a process for preventing the pixel array, and a reading unit that reads out signal charges of the detection elements included in the row for each row of the pixel array via the readout line during X-ray irradiation, and outputs the read out as image data. Wherein the reading unit performs processing for preventing generation of signal charges due to X-ray irradiation in the pixel array prior to correction of image data of each frame constituting a continuous fluoroscopic image. An X-ray flat panel detector for reading out the applied signal charges of the pixel rows and outputting at least one row of leakage signal information;
Correction data storage means for storing correction data for one row of the X-ray flat panel detector based on the leak signal information output from the reading unit;
Image data correction means for correcting the image data by subtracting the correction data stored in the correction data storage means from the image data of each row of the pixel array output from the reading unit,
Image display means for displaying a continuous perspective image based on the image data corrected by the image data correction means,
A radiographic imaging apparatus comprising:

Images