JP2001340324A - X-ray detector and radiodiagnostic device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray detector and a radiodiagnostic device using the same capable of accurately removing a dark current noise. SOLUTION: In the radiodiagnostic device comprising an X-ray image detector having X-ray detecting elements 63 each for converting an X-ray exposed toward a subject and transmitted through the subject into a charge signal and accumulating the signal and arranged in a two-dimensional manner and a read control TFT 62 for controlling reading of the charges stored in the elements, the image detector has an X-ray detecting element 63 masked so that the charge is not accumulated therein at the exposure time, and a differential circuit 68 for removing the dark current noise from the charge signal based on an output of the masked element 63.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray detector in which a plurality of X-ray detecting elements for converting X-rays into electric signals are two-dimensionally arranged, and an X-ray diagnostic apparatus using the same.

[0002]

2. Description of the Related Art An X-ray (semiconductor) flat panel detector is a means for detecting an X-ray transmitted through a subject, such as an imaging device using a film or the like. I. (Imaging Intensifier)-An X-ray imaging device that may be replaced by a TV imaging device or the like in the future, and a detected X-ray image can be displayed on a display in real time and stored as digital data ( Shooting).

FIG. 14A is a diagram showing an example of an image pickup apparatus using a film or the like. The X-rays emitted from the X-ray tube 101 are exposed to a subject 102, and the subject 102
X-rays transmitted through are exposed to the film 103. When the film 103 is developed, an X-ray image transmitted through the subject 102 is obtained.

[0004] FIG. I. It is a figure showing an example of -TV imaging device. X-rays radiated from the X-ray tube 101 are applied to the subject, and the image of the X-rays transmitted through the subject 102 is represented by I.D. I. The light is converted into an image of light via the optical system 104, and an optical system mechanism (including a lens or the like)
5. The optical mechanism 105 focuses an image of light to a desired size, focuses the image, and captures the image by a TV camera 106.

[0005] The TV camera 106 includes a camera controller 10
The camera controller 107 controls an image signal output from the TV camera 106 as an image (CRT (cathode ray tube) display) 1
08 is displayed.

FIG. 15 is a view showing an example of an X-ray imaging apparatus using an X-ray flat panel detector. X-rays radiated from the X-ray tube 101 are emitted to the subject 102, and the X-rays transmitted through the subject 102 enter the X-ray flat panel detector 109. The X-ray flat panel detector 109 is controlled by a camera controller 107 like the TV camera 106, so that signals of respective pixels are sequentially output. This signal is output by the camera controller 107. The image is displayed on the monitor 108 as an image.

FIG. 16 is a circuit diagram showing an example of a configuration of a main part of the X-ray flat panel detector. FIG. 17 is a circuit diagram showing an X-ray detecting element constituting the X-ray flat panel detector.
FIG. 8 is a cross-sectional view showing a main structure of an actual X-ray detection element.

[0008] The X-ray detecting element senses light and generates a charge according to the amount of incident light, a capacitor (hereinafter referred to as a storage capacitor) 112 for storing the charge from the photodiode 111, TFT (thin film transistor) 113 used as a switch for reading out the electric charge stored in the storage capacitor 112
It is composed of

The connection point between the cathode terminal of the photodiode 111 and one terminal of the storage capacitor 112 is connected to a reverse bias power supply (-Vn), and the anode terminal of the photodiode 111 and the other terminal of the storage capacitor 112 are connected. The connection point with the terminal is connected to the source terminal of the TFT 113.

The X-ray flat panel detector 109 uses the X-ray detecting element as one element, and uses the X-ray detecting element as a column and a line.
Are arranged in a two-dimensional array. Further, the gate terminal of the TFT 113 is commonly connected to each line, and is connected to each line output terminal of the gate driver 114.

Each of the line output terminals of the gate driver 114 sequentially outputs a pulse-like control signal in time sequence, and the TFTs 113 on the same line are simultaneously turned on by the pulse-like control signal. In operation, the TFTs 113 on different lines are sequentially turned ON in time sequence.

The drain terminal of the TFT 113 is commonly connected to each column, and is connected to a read-out amplifier (Read-out A).
mplifier) 115, a capacitor (hereinafter, referred to as a capacitor for time constant) 116 and a reset switch 117 are connected to respective input terminals of a multiplexer 118 via an integrating circuit.

The multiplexer 118 takes in the signals inputted to the respective input terminals during one pulse outputted from the respective line output terminals of the gate driver 114 one by one in time sequence and outputs the signals. Output from the terminal.

Accordingly, the pulse-like control signal output from each line output terminal of the gate driver 114 causes
When the TFTs 113 in the line are simultaneously turned on, the electric charge accumulated in the accumulation capacitor 112 is output through the TFT 113, and this current is converted into a voltage via an integrating circuit, and the current is converted one by one by a multiplexer 118. (One pixel per line) is output. When reading of one line is completed in this way, reading of the next line is started.

That is, like a scanning line of a television, one X-ray detecting element is provided for each line (one pixel at a time).
The detection signals are read in order and output as image data (video signals) for one screen.

Further, a fluorescent substance for converting X-rays into light is formed in a layer on a two-dimensional array of the X-ray detecting elements. That is, a plurality of TFs on the support 121
A gate electrode 122 is formed in the T region, and Si
An Nx layer 123 is formed. On the SiNx layer 123, an a-Si layer 124, a drain electrode 125, and a source electrode 126 are formed in the TFT region. The drain electrode 125 and the source electrode 126 are connected via the a-Si layer 124 and are not directly connected.

In the gap between the drain electrode 125 and the source electrode 126 and the a-Si layer 124, n + a-Si layers 127 and 128 are formed. Thus, a TFT is formed in the TFT region.

On the other hand, the SiNx layer 123 and the source electrode 126 are formed in a plurality of PD regions on the support 11, and an n + layer 129, an i layer 130,
Photodiode 1 with a pin structure composed of a P + layer 131
11 are formed.

A first polyimide resin layer 132 is formed on the plurality of TFTs, and a transparent electrode 133 is formed on the plurality of photodiodes 111. On the first polyimide resin layer 132, a metal electrode 134 connecting between the transparent electrodes 131 of each of the photodiodes is formed.

The transparent electrode 133 and the metal electrode 13
4, a second polyimide resin layer 135 is formed. On the second polyimide resin layer 135, a transparent protective film 136, a phosphor 137, and a light reflection layer 138 are formed.

Next, a method for obtaining an X-ray image will be described. X-rays transmitted through the subject from above are reflected by the light reflecting layer 138.
Is transmitted to the phosphor 137. At this time, visible light incident from above is reflected by the light reflection layer 138 and is not incident on the phosphor 137.

The energy of the incident X-ray is converted into light energy (visible light) by the phosphor 137, and this visible light passes through the transparent protective film 136 and the second polyimide resin layer 135, and further passes through the transparent electrode 133. And is received by the photodiode 111 sensitive to visible light.

The photodiode 111 converts the charge into a charge amount proportional to the energy of light and stores the charge in the storage capacitor 112. As described above, the accumulated charges are read out on a pixel basis for each line through the data line. The read signal is proportional to the energy of the X-ray, and an X-ray image can be reproduced by reconstructing the signal read in pixel units.

However, the X-ray flat panel detector 109
Due to its structure, when X-rays are not irradiated, noise charge is accumulated in the accumulation capacitor 112 in the X-ray flat panel detector 109 by dark current. For this reason, the electric charge stored in the storage capacitor 112 by the photodiode 111 is limited. Therefore, regardless of the presence or absence of X-rays, reading is always performed or immediately before X-rays are incident, regardless of the presence or absence of X-rays for the purpose of obtaining a wide dynamic range. It is necessary to perform an operation of once performing idle reading and discharging the charge (noise charge) stored in the storage capacitor 112.

[0025]

However, when reading is always performed, it is necessary to adjust the X-ray irradiation timing to this reading cycle, and it is not possible to irradiate X-rays at a desired timing. There was a problem of bad.

Further, the exposure time is limited in accordance with the readout cycle, so that there is a possibility that a sufficient X-ray dose cannot be applied to the subject, and a clear X-ray image may not be obtained. there were.

In the method of performing a blank read operation in which dark current noise is sequentially emitted line by line before X-ray irradiation, it takes a long time from when an operator attempts to emit X-rays until completion of preparation. However, there is a problem that X-rays cannot be immediately emitted.

It is an object of the present invention to provide an X-ray detector capable of removing dark current noise with high accuracy and an X-ray diagnostic apparatus using the same.

[0029]

The invention corresponding to claim 1 is:
An X-ray image detecting unit in which X-ray generating means for irradiating X-rays toward the subject and an X-ray detecting element for converting a Χ-ray transmitted through the subject into a charge signal and accumulating them are two-dimensionally arranged. And the X
In an X-ray diagnostic apparatus including a readout control unit that controls reading out of electric charges accumulated in a X-ray detection element, the X-ray image detection unit is configured to mask X so that electric charges are not accumulated during X-ray irradiation. A line detecting element; and a correcting means for removing dark current noise from the charge signal based on the output of the masked X-ray detecting element. The invention according to claim 2 has an X-ray image detection unit in which X-ray detection elements that convert a Χ-ray transmitted through the subject into a charge signal and accumulate them are two-dimensionally arranged, and the X-ray detection element In the X-ray detector, which is used for diagnosis by reading out the charge accumulated in the X-ray and imaging it, a masked X-ray detection element is provided so that the charge is not accumulated when the X-ray is irradiated. The masked output of the X-ray detecting element is used for removing dark current noise included in the charge signal.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a main configuration of an X-ray imaging apparatus to which the present invention is applied. 1 is a control unit. The control unit 1 includes an X-ray tube X
For the X-ray generation unit 2 composed of a tube lamp driving unit and the like,
Control is performed so that a desired X-ray dose is applied to the subject. The X-ray semiconductor flat detector 3 that detects X-rays transmitted through the subject is controlled to read charges accumulated by X-ray irradiation.

An exposure start switch 1-1 provided on an operation panel (not shown) is connected to the control unit 1. When the exposure start switch 1-1 is turned on, the X-ray generation unit 2 is turned on. The timing of the start of irradiation is supplied.
The exposure start switch 1-1 may be provided in the X-ray generation unit 2 instead of the control unit 1 for convenience of operability.

FIG. 2 is a circuit diagram showing a main configuration of the X-ray flat panel detector 3. As shown in FIG. Since the configuration of the X-ray flat panel detector 3 is the same as that described in the related art (see FIGS. 16 and 17), the description thereof is omitted here.

The control unit 1 controls the X-ray generation unit 2
When the timing information of the X-ray irradiation is supplied to the gate driver 4, the gate driver 4 drives all the X-ray detecting elements simultaneously based on the supplied X-ray irradiation timing information. Are output at the same timing.

Alternatively, as shown in FIG. 3, when the X-ray irradiation timing information is supplied from the control unit 1, the gate driver 4 sets a plurality of (for example, three) lines as one block. An ON pulse signal of the same timing is output for each block.

Therefore, in the integration circuit 5 composed of the readout amplifier and the capacitor for the time constant, the TFTs of all the lines or a plurality of lines are turned ON, and the accumulated electric charges are accumulated from all the accumulation capacitors of those lines. Even if they are discharged at the same time, they have a current resistance (capacity) sufficient to allow the accumulated charges to flow.

In the first embodiment having such a configuration, for example, as shown in FIG. 4, timing between X-ray irradiation and TFT occurs. The X-ray generation unit 2 generates X-ray irradiation timing, and the control unit 1 obtains the X-ray irradiation timing and sends the X-ray irradiation timing to the gate driver 4 of the X-ray flat panel detector 3. The timing information is supplied (time t1).

Based on the timing information of the X-ray exposure, the gate driver 4 generates ON pulses of the same timing for each block in which all lines or a plurality of lines are one block as shown in FIG. 2 or FIG. Output a signal. All TFTs on the line where this ON pulse signal was output
Is turned on, the accumulated charge (dark current noise) accumulated in the storage capacitor connected to the TFT is discharged and flows to the integration circuit including the readout amplifier and the time constant capacitor. At this time, the integration circuit does not integrate the accumulated charge (dark current noise) or resets the integration immediately after the integration so as not to affect the integration of the accumulated charge due to X-ray irradiation.

When the discharge (elimination) of the dark current noise stored in the storage capacitor is completed in this manner, the TF
When T is turned off (time point t2), the photodiode for the storage capacitor is again started to accumulate charges by X-ray irradiation. That is, in FIG. 4, the time A from the time t1 to the time t2 is the noise sweeping time, and the time t
The time B from time 2 to time t3 when the X-ray irradiation ends is the imaging time, and the time C from time t1 to time t3 is the X-ray irradiation time.

As described above, according to the first embodiment, X
By simultaneously sweeping out the charge such as dark current noise accumulated in the storage capacitors of the X-ray detection elements of all lines or a plurality of lines in accordance with the line irradiation timing, the accumulated charge such as dark current noise is swept. Can be greatly reduced, and X-ray imaging can be performed at a desired timing.

A second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the configuration is the same as the configuration of the above-described first embodiment (see FIGS. 1, 2, 16, and 17), and the description of the configuration is omitted here. .

In the second embodiment, the timing between the X-ray irradiation and the TFT occurs as shown in FIG. When the operator turns on the exposure start switch 1-1 (time t4), first, an ON pulse signal of the same timing is output to all the lines from the first line of the TFT to the n-th line of the TFT. All the TFTs on the line to which this ON pulse signal was output are turned ON, and this TFT
The stored charge (dark current noise) stored in the storage capacitor connected to the storage capacitor is discharged to the integration circuit.

As described above, when the discharge of the dark current noise is completed and the TFT is turned off, X-ray irradiation is started (time t5). By this X-ray exposure, the charge from the photodiode is stored in the storage capacitor. Then, when the operator turns OFF the exposure start switch 1-1 (time t6), the X-ray exposure ends, an ON pulse signal is sequentially supplied to each line of the TFT, and the charge stored in the storage capacitor is stored. A reading is performed. When the X-ray irradiation time exceeds the preset maximum allowable irradiation time, the X-ray irradiation is automatically terminated without the operator's operation of turning off the irradiation start switch 1-1. It has become.

That is, in FIG. 5, a time D from time t4 to time t5 is a noise sweeping time, a time E from time t5 to time t6 is an X-ray irradiation time, and a time F after time t6 is read. Time.

As described above, according to the second embodiment, the same effects as those of the first embodiment can be obtained, and further, charges such as dark current noise are swept out before the start of X-ray irradiation. Therefore, it is possible to prevent unnecessary irradiation of X-rays.

A third embodiment of the present invention will be described with reference to FIGS. In the first and second embodiments described above, the control unit 1 and the X-ray generation unit 2 are directly connected, and the timing of X-ray irradiation is directly obtained from the X-ray generation unit 2. In contrast, in the third embodiment, some methods for indirectly obtaining the timing of X-ray irradiation when the control unit 1 is not connected to the X-ray generation unit 2 are described. Will be described.

FIG. 6 shows a first example of obtaining the timing of X-ray exposure.
FIG. 4 is a block diagram showing a configuration of the method. The X-ray detection signal output from the X-ray detection sensor 13 provided on the X-ray incidence surface of the X-ray flat panel detector 12 or the back surface thereof is input to the control unit 11.

When the X-ray detection sensor 13 is disposed on the X-ray incident surface of the X-ray flat panel detector 12, it is preferably formed of a material that transmits X-rays. It is arranged in a dead part of the flat panel detector 12. Further, when the X-ray detector 12 is disposed behind the X-ray incident surface of the X-ray flat panel detector 12, a detector having high X-ray sensitivity is used to detect X-rays leaking from the X-ray flat panel detector 12. Is done.

FIG. 7 shows a second example of obtaining the timing of X-ray exposure.
FIG. 4 is a block diagram showing a configuration of the method. The control unit 14 has one (one pixel) X at the end of the X-ray flat panel detector 15.
An X-ray detection signal output from the X-ray sensor unit 15-1 including a line detection element or one line (a plurality of) X-ray detection elements is input.

FIG. 8 shows a third example of obtaining the timing of X-ray exposure.
FIG. 4 is a block diagram showing a configuration of the method. The control unit 16 receives a current detection signal output from a current detection sensor 18 that detects a current flowing through an X-ray tube 17 constituting an X-ray generation unit (not shown) that irradiates the subject with X-rays. Is entered.

In the third embodiment having such a configuration, the timing of X-ray irradiation is detected by the X-ray detection sensor 13, X-ray detection element, or current detection sensor 18, and this detection signal is controlled. The parts 11, 14, 16 are supplied.

The control units 11, 14, and 16 obtain the timing of X-ray irradiation and supply timing information of X-ray irradiation to each gate driver of the X-ray flat panel detectors 12, 15, and 19. Thereafter, the operation is the same as that of the above-described first embodiment, and the description is omitted here. Thus the third
According to the embodiment, the same effects as those of the above-described first and second embodiments can be obtained.

A fourth embodiment of the present invention will be described with reference to FIGS. FIG. 9 is a block diagram showing a main configuration around one pixel (one X-ray detecting element) of the X-ray imaging apparatus to which the present invention is applied. 21 is a control unit.
The control unit 21 controls the gate driver 22 and the switch 23-1 included in the integration circuit 23 as described later.

The power from the reverse bias power supply -Vn is
It is supplied to an anode terminal of a photodiode 24 constituting an X-ray detecting element and one end of a capacitor (hereinafter referred to as a storage capacitor) 25 connected in parallel to the photodiode 24. The connection point between the cathode terminal of the photodiode 24 and the other end of the storage capacitor 25 is connected to the source terminal of the TFT 26.

The line (Ro) is connected to the gate driver 22.
w) A gate drive line provided for each TFT 26 is connected, and the gate drive line is connected to the gate terminal of each TFT 26. The drain terminal of each of the TFTs 26 is a column.
The output terminal of the integration circuit 23 is connected to a multiplexer (not shown) via a data signal line provided for each (Column).

The integration circuit 23 is provided with the switch 23-
1. Read-out Amplifier 23
-2 and a capacitor (hereinafter referred to as a capacitor for a time constant) 23-3. The drain terminal (data signal line) of the TFT 26 is connected to the inverting input terminal of the readout amplifier 23-2, and the switch 23-1 and the capacitor 23-3 are connected between the inverting input terminal and the output terminal. Are connected. The non-inverting input terminal of the readout amplifier 23-2 is connected to ground (0V).

In the fourth embodiment having such a configuration, control is performed at timings as shown in FIG.
Before X-ray irradiation (until time t7), the ΤFT control signal supplied from the gate driver 22 via the gate drive line is set to a positive potential to keep the TF # 26 on, and the switch 23-1 of the integrating circuit 23 is turned on. Is in the ON state.
As a result, the dark current noise is reduced by the storage capacitor 25.
From the TF # 26, the data signal line, and the integration circuit 23.

Next, when the control unit 21 turns on the X-ray emission start signal (time t7), the X-ray generation unit starts the X-ray emission, and at the same time, the gate driver 22 sets the ΤFT control. The signal is set to zero potential (negative potential) to turn off the FT26. Next, an X-ray exposure start signal is
At F (time t8), the X-ray generation unit stops the X-ray irradiation. After the X-ray irradiation is completed and before the accumulated charge is read out (before t9), the switch 23-1 of the integration circuit 23 is turned off, and thereafter, at time t9
, And sequentially read out the signals.

As described above, according to the fourth embodiment, before the X-ray irradiation timing, ΤFΤ26 becomes O
Since N is set to N so that dark current noise is not always accumulated in the accumulation capacitor 25, accumulation of electric charge can be started simultaneously with X-ray irradiation. Therefore, the sweeping time of the accumulated charges such as dark current noise is short, and the X-ray imaging is performed at a desired timing without wasting the X-ray exposure as compared with the above-described first, second, and third embodiments. It can be performed.

A fifth embodiment of the present invention will be described with reference to FIG. FIG. 11 is a block diagram showing a main configuration of an X-ray imaging apparatus to which the present invention is applied. 31 is a control unit. The control unit 31 controls the X-ray generation unit 32 and the X-ray flat panel detector 33 and controls the supply of power to the X-ray flat panel detector 33, as in the first embodiment. The power supply control section 33-1 is controlled.

That is, similarly to the above-described fourth embodiment, before the X-ray irradiation timing, the X-ray flat panel detector 33 (especially, the storage capacitor constituting the X-ray flat panel detector 33) is connected. Cut off (stop) the power supply. And X
When the X-ray exposure timing occurs, the X-ray flat panel detector 33
Supply power to the As described above, according to the fifth embodiment, the same effects as those of the above-described fourth embodiment can be obtained.

A sixth embodiment of the present invention will be described with reference to FIG. FIG. 12 is a circuit diagram showing a main configuration of an X-ray flat panel detector of an X-ray imaging apparatus to which the present invention is applied. The difference between this X-ray flat panel detector and the X-ray flat panel detector (see FIG. 2) described in the first embodiment is that the dark current noise (other signals) The point is that a circuit for performing shading correction for removing noise (including fixed pattern noise) is provided.

That is, after the X-ray irradiation, a signal for turning on the TFT 42 line by line from the gate driver 41 is output in a time sequence. Then, the TFT 42 is provided for each line.
The electric charge accumulated by the X-ray exposure from the X-ray detection element connected to the X-ray detector is output as a data signal line. The X-ray detecting element 43 is composed of a photodiode and a storage capacitor as described in the related art (FIGS. 15 and 16).

The charges output in time series for each line are readout amplifiers and time constant capacitors for each column (a switch for discharging (resetting) the charges accumulated in the time constant capacitors is omitted). ) Are input to the respective input terminals of the multiplexer 45 via the integration circuit 44 composed of. This multiplexer 45
The output from each of the integrating circuits 44 is selected in time series and output as a serial signal.

This serial signal is input to the A / D converter 46. The A / D converter 46 converts an analog serial signal into a digital signal (digital data) and outputs it. The outputted digital data is subtracted by a subtractor 47.
Is input to The subtractor 47 includes an arithmetic processing circuit 48
Are connected, and correction data (noise amount data) for shading is supplied.

The arithmetic processing circuit 48 includes a memory 49 in which noise amount data per unit time is stored in advance for each X-ray detecting element (each pixel) and an accumulation time for each line from the previous reading of the X-ray image. Time counting circuit 50 for counting time
Is connected, the noise amount data per unit time of the corresponding X-ray detecting element is supplied from the memory, and the accumulation time data of the corresponding line is supplied from the accumulation time counting circuit 50.

Therefore, based on the data of the noise amount per unit time from the memory 48 and the accumulation time data from the accumulation time counting circuit 50, the arithmetic processing circuit 49 calculates the accumulated noise amount included in the digital data. And supplies the accumulated noise amount data to the subtracter 47 as shading correction data.

The subtractor 47 is provided with the A / D converter 46.
Then, the accumulated noise amount data is subtracted from the digital data directly supplied from the CPU and output. The A / D converter 46 and the memory 48 are connected to each other. When the amount of noise per unit time is set in advance, the amount of noise per unit time is transferred from the A / D converter 46 to the memory 48. Data is supplied.

In the sixth embodiment having such a configuration, the memory 49 previously stores noise amount data per unit time for each X-ray detecting element. For example, after sweeping out dark current noise, reading is performed by waiting (photographing) for a unit time without exposing X-rays.
The digital data output from the D converter 46 is directly stored as noise amount data in the memory 49 for each X-ray detection element. In addition, the accumulation time counting circuit 50 determines that the previous X
The elapsed time (accumulation time) since the reading of the line image is measured.

In this state, when an X-ray image is read by actually exposing X-rays, the digital data output from the A / D converter 46 is output from the memory 49 as noise per unit time. Based on the amount data and the accumulation time data from the accumulation time counting circuit 50, the accumulated noise amount data calculated by the arithmetic processing circuit 48 is subtracted to obtain data obtained by X-ray irradiation without dark current noise or fixed pattern noise. Become.

As described above, according to the sixth embodiment, X
A memory 49 for storing the amount of noise per unit time for each line detecting element, a storage time clock circuit 50 for measuring the storage time since the previous reading of the X-ray image, and a noise amount and a storage time for the unit time. By providing an arithmetic processing circuit 48 for calculating the accumulated noise amount data based on the data and a subtractor 47 for subtracting the accumulated noise amount data from the digital data from the A / D converter 46, the digital data read from the read digital data can be obtained. An accurate X-ray image can be obtained by eliminating the influence of dark current noise.

Accordingly, when dark current noise is simultaneously removed from all the X-ray detection elements before the X-ray exposure timing, when the X-ray detection elements of the line to be read first are read in the order of the read lines. And the detection data from the X-ray detection element for the last line to be read, the dark current noise is larger for the X-ray detection element for the last line to be read. There is a problem that the influence of the dark current noise is different for each line. However, according to the sixth embodiment, the effect that the difference in the influence of the dark current noise for each line can be easily eliminated can be obtained.

A seventh embodiment of the present invention will be described with reference to FIG. FIG. 13 is a circuit diagram showing a main configuration of an X-ray flat panel detector of an X-ray imaging apparatus to which the present invention is applied.

After the X-ray irradiation, a signal for turning on the TFT 62 for each line is output from the gate driver 61 in time series. Then, the charge accumulated by the X-ray irradiation from the X-ray detection element connected to the TFT 62 for each line is output as a data signal line. Each of the X-ray detection elements 63 is composed of a photodiode and a storage capacitor, as described in the background art, and one of these X-ray detection elements 63 (the end row).
A mask 64 for shielding X-rays is provided on the X-ray incidence surface of the X-ray detecting element.

The charges output in time series for each line are readout amplifiers and time constant capacitors for each column (a switch for discharging (resetting) the charges accumulated in the time constant capacitors is omitted). ) Is input to the integrating circuit 65.

The output terminals of the integrating circuits 65 in the column provided with the mask 64 are connected to a first resistor 66 and a second resistor 67.
Is connected to ground (0 V) via a series voltage dividing circuit composed of

On the other hand, the output terminals of the integrating circuits 65 in the other columns are connected to the inverting input terminals of the operational amplifiers constituting the differential circuits (differential amplifier circuits) 68 via the resistors 69. A connection point (divided voltage output point) between the first resistor 66 and the second resistor 67 is connected to a non-inverting input terminal of each operational amplifier of the difference circuit 68.

Each output terminal of the difference circuit 68 is connected to each input terminal of the multiplexer 70. The multiplexer 70 selects the output from each of the difference circuits 68 in a time sequence and outputs the selected signal as a serial signal. This serial signal is input to the A / D converter 71. The A / D converter 71 converts an analog serial signal into a digital signal and outputs the digital signal.

In the seventh embodiment having such a structure, for example, when the X-rays are emitted to the subject after the simultaneous sweeping of the dark current noise for all the X-ray detecting elements 63, the mask 64 In each X-ray detecting element not provided, an electric charge corresponding to the detected transmitted X-ray dose is accumulated. On the other hand, in each X-ray detecting element 63 provided with the mask 64, dark current noise (other various noises) is stored. ) Are accumulated as electric charges.

When the X-ray exposure is completed and reading is performed in a time-sequential manner for each line, one X-ray detecting element 62 provided with a mask 64 outputs a charge indicating dark current noise. A voltage indicating this charge is output from a connection point between the first resistor and the second resistor, and each difference circuit 68 outputs a voltage between the detection signal from the other X-ray detection element 62 and the voltage of the dark current noise. The difference is amplified and output to the multiplexer 70. That is, the voltage corresponding to the dark current noise is subtracted from the detection signal from the other X-ray detection element 63 in which the charge is accumulated by the X-ray irradiation, and the result is output to the multiplexer 70.

As described above, according to the seventh embodiment, the mask 64 for shielding the X-rays incident on a predetermined row of X-ray detection elements and the output from these X-ray detection elements 63 are provided. By providing the difference circuit 68 for subtracting the voltage corresponding to the dark current noise from the detection signal from the other X-ray detection element 63 without the mask 64, the same effect as in the above-described sixth embodiment can be obtained. Obtainable.

Further, in the seventh embodiment, in the method of sweeping out dark current noise before X-ray irradiation, the method of sweeping out one line at a time, the method of sweeping out each block of a plurality of lines, and the like. Even in the method of simultaneously sweeping out all the lines, the dark current noise can be accurately removed in any case. Further, when the sixth embodiment is combined with the seventh embodiment, a higher effect in removing dark current noise can be obtained.

Therefore, the first to fifth embodiments are appropriately combined before the X-ray exposure, and the sixth embodiment is used when reading the X-ray image data after the X-ray exposure. By using the method in which the embodiment and the seventh embodiment are combined, it is possible to obtain a higher effect in eliminating the influence of dark current noise.

An integrating circuit (5, 23, 44, 65) comprising a readout amplifier and a capacitor for a time constant constituting the X-ray flat panel detector is provided on the input terminal side of the multiplexer for each column of X-ray detecting elements. However, the present invention is not limited to this. For example, it is not provided on the input terminal side of the multiplexer, but is connected to the output terminal side of the multiplexer.
Only one may be provided. By doing so, the number of integrating circuits can be reduced, the circuit can be simplified, the substrate can be made smaller, and the cost can be reduced.

As a configuration of the X-ray flat panel detector, there is a method that does not use a multiplexer. That is, A / D converters may be connected to integrating circuits provided for each column of X-ray detection elements, and outputs from the A / D converters may be selected and taken in time series. Things.

[0085]

As described in detail above, according to the present invention,
Dark current noise can be removed with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a main configuration of an X-ray imaging apparatus according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a main configuration of an X-ray flat panel detector of the X-ray imaging apparatus according to the embodiment;

FIG. 3 is a diagram showing a gate driver of an X-ray flat panel detector of the X-ray imaging apparatus according to the embodiment.

FIG. 4 shows X-ray exposure and TF of the X-ray imaging apparatus according to the embodiment.
The figure which shows the timing of ON / OFF control of T.

FIG. 5 is a diagram showing timings of X-ray irradiation and TFT ON / OFF control of the X-ray imaging apparatus according to the second embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a first method for obtaining X-ray irradiation timing of an X-ray imaging apparatus according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a second method for obtaining X-ray irradiation timing of the X-ray imaging apparatus according to the embodiment.

FIG. 8 is a block diagram showing a configuration of a third method for obtaining X-ray irradiation timing of the X-ray imaging apparatus of the embodiment.

FIG. 9 is a block diagram illustrating a configuration of a main part around one X-ray detection element of an X-ray imaging apparatus according to a fourth embodiment of the present invention.

FIG. 10 is a view showing timings of various signals of the X-ray imaging apparatus of the embodiment.

FIG. 11 is a block diagram showing a main configuration of an X-ray imaging apparatus according to a fifth embodiment of the present invention.

FIG. 12 is a circuit diagram showing a main configuration of an X-ray flat panel detector of an X-ray imaging apparatus according to a sixth embodiment of the present invention.

FIG. 13 is a circuit diagram showing a main configuration of an X-ray flat panel detector of an X-ray imaging apparatus according to a seventh embodiment of the present invention.

FIG. 14 shows a conventional imaging apparatus using a film or the like and I.I. I. The figure which shows the example of a -TV image imaging device.

FIG. 15 is a diagram showing a conventional example of an X-ray imaging apparatus using an X-ray (semiconductor) flat panel detector.

FIG. 16 is a circuit diagram showing an example of a configuration of a main part of an X-ray flat panel detector of the X-ray imaging apparatus of the conventional example.

FIG. 17 is a circuit diagram showing an X-ray detection element constituting an X-ray flat panel detector of the X-ray imaging apparatus of the conventional example.

FIG. 18 is a cross-sectional view showing a main structure of an actual X-ray detection element constituting an X-ray flat panel detector of the X-ray imaging apparatus of the conventional example.

[Explanation of symbols]

 1, 11, 14, 16, 21, 31, ... control unit, 2, 32 ... X-ray generation unit, 3, 12, 15, 19, 33 ... X-ray plane detector, 4, 22, 41, 61 ... gate driver , 5, 23, 44, 65: integrating circuit, 13: X-ray detection sensor, 15-1: X-ray sensor unit, 18: current detection sensor, 33-1: power supply control unit, 45, 70: multiplexer, 48 ... Arithmetic processing circuit, 49: memory, 50: accumulation time counting circuit, 64: mask, 68: difference circuit.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) G03B 42/02 G03B 42/02 H01L 21/027 H04N 5/32 27/14 5/335 R 31/09 H01L 21/30 531Z H04N 5/32 27/14 K 5/335 31/00 A (72) Inventor Koichiro Nabuchi 1385-1 Shimoishigami, Otawara-shi, Tochigi Pref. Toshiba Nasu Plant (72) Inventor Akira Tsukamoto 1385-1, Shimoishigami, Otawara City, Tochigi Prefecture, Japan Inside the Toshiba Nasu Factory (72) Inventor Shinichi Yamada 1385-1, Shimoishigami, Otawara City, Tochigi Prefecture, Japan 1 Toshiba Nasu Factory (72) Inventor Saisu Torugi 1385-1 Shimoishigami, Otawara City, Tochigi Prefecture Inside the Toshiba Nasu Factory (72) Inventor Takayuki Tomisaki 1385-1 Shimoishigami, Otawara City, Tochigi Prefecture 1 Inside the Toshiba Nasu Factory (72) Inventor: Manabu Tanaka Tochigi Prefectural university Changwon Shimoishigami 1385 No. 1 stock company Toshiba Nasu in the factory (72) inventor Seiichiro Nagai Tochigi Prefecture Otawara Shimoishigami 1385 No. 1 Toshiba main di Cal Engineering Co., Ltd. in

Claims (2)

[Claims] 1. An X-ray generating means for irradiating an X-ray toward a subject, and an X-ray detecting element for converting a Χ-ray transmitted through the subject into a charge signal and accumulating the X-ray, are two-dimensionally arranged. An X-ray diagnostic apparatus comprising: an X-ray image detection unit; and a readout control unit that controls reading out of the electric charge stored in the X-ray detection element. An X-ray detector comprising: an X-ray detection element masked so as not to be performed; and a correction means for removing dark current noise from the charge signal based on an output of the masked X-ray detection element. Diagnostic device. 2. An X-ray detector comprising two-dimensionally arranged X-ray detecting elements for converting a Χ-ray transmitted through the subject into a charge signal and storing the charge signal.
An X-ray detector having a line image detecting unit and reading out and imaging an electric charge accumulated in the X-ray detecting element performs the accumulation of the electric charge when the X-ray is irradiated. An X-ray detector comprising a predetermined number of masked X-ray detection elements so as to prevent dark current noise included in the charge signal from being output from the masked X-ray detection elements.