JP2003047605A - Radiograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the update time for data on the intensity of an X-ray signal. SOLUTION: Data for canceling variation in signal intensity of the X-ray detection signal is divided into the correction data for a detecting element hard to vary with the passage of time and correction data for an amplifying element easy to vary with the passage of time and stored in the correction tables 14, 15, respectively. Only the correction data for the amplifying element is independently updated to restrain variation with time as the whole correction data. In the case of updating only the correction data for the amplifier element, the number of pre-amplifiers is smaller than the number of X-ray detecting elements, and the number of correction data for amplifier element is smaller than the number of correction data for the detecting elements, so that the data collection and storage time is considerably short so as to shorten the data update time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation image pickup apparatus such as a medical X-ray image pickup apparatus or an industrial X-ray nondestructive inspection apparatus for detecting radiation by an array type radiation detector, and more particularly to an array type radiation detector. The present invention relates to a technique for shortening the update time of correction data used to eliminate the variation in the signal intensity of the radiation detection signal output from the device.

[0002]

2. Description of the Related Art Recently, in a medical or industrial X-ray imaging apparatus, a flat panel type X-ray sensor (hereinafter referred to as "panel type sensor") 51 as shown in FIG. Is attracting attention as an array-type X-ray detector of W.Zhao, et al., “A flat panel detec
tor for digital radiology using active matrix read
out of amorphous selenium, '' Proc. SPIE Vol.2708, pp.
523-531, 1996). This panel type sensor 51 has a structure in which a large number of X-ray detection elements 51A having an X-ray sensitive film such as an amorphous selenium film (a-Se film) are arranged on the detection surface in an XY matrix, and are lightweight. -It is a two-dimensional array type X-ray detector that is thin and suitable for large area.

However, there is considerable variation in the signal intensity between the X-ray detection signals output from the panel type sensor 51 as the X-rays are detected by each X-ray detecting element 51A. That is, the characteristics of the offset (the intensity of the detection signal when the X-ray is not irradiated) and the sensitivity (the intensity of the detection signal when the X-ray is irradiated with the same dose) are not uniform among the X-ray detection elements 51A, and there are variations. , X-ray detection signals vary in signal strength.

Due to such a state, the difference in signal intensity due to the variation in signal intensity appears as a noticeable artifact (false image) in the X-ray image output on the screen of the display monitor 55. .

Therefore, as shown in FIG. 13, both offset and sensitivity correction data, which are correction data for eliminating the variation in the signal intensity of the X-ray detection signal of the panel sensor 51, are preliminarily obtained from the panel sensor 51. The signal is collected by the signal processing unit 52 based on the output signal of, and stored in the offset correction table 53 and the sensitivity correction table 54.

Then, during execution of X-ray imaging, the signal processing unit 52 stores the X-ray detection signal output from the panel type sensor 51 along with the X-ray irradiation of the subject to be imaged in the correction tables 53 and 54. The correction calculation process is performed using the corrected data. As a result, variations in the signal intensity of the X-ray detection signal are eliminated, and the appearance of artifacts in the X-ray image is prevented.

Furthermore, since the offset / sensitivity characteristic of the panel type sensor 51 changes with time, X
It is also necessary to update both offset / sensitivity correction data, which is data for eliminating variations in the signal strength of the line detection signal. Therefore, after a lapse of a predetermined time, the signal processing unit 52 recollects the new offset / sensitivity correction data, rewrites the old data stored in the correction tables 53 and 54 with the new offset / sensitivity correction data, and updates the data. is doing.

[0008]

However, in the case of the above-mentioned conventional X-ray imaging apparatus, the correction data is updated to eliminate the variation in the signal intensity of the X-ray detection signal output from the flat panel X-ray sensor 51. There is a problem that it takes time.

That is, the offset correction data and the sensitivity correction data must be collected for each X-ray detecting element 51A, but since the total number of X-ray detecting elements 51A is considerable, the correction data is updated. It takes a long time to get there.

The present invention has been made in view of the above circumstances, and it takes time to update the correction data for eliminating the variation in the signal intensity of the radiation detection signal output from the array type radiation detector. It is a main object to provide a radiation imaging apparatus capable of shortening

[0011]

The present invention has the following constitution in order to achieve such an object. That is, the radiation imaging apparatus according to the invention of claim 1 is
(A) Radiation irradiation means for irradiating the subject with radiation,
(B) An array-type radiation detector in which a large number of radiation detection elements are arranged on a detection surface and a radiation detection signal is read out through a common signal amplification element provided for each of the plurality of radiation detection elements, (C) The correction data for the detection element that eliminates the variation in the signal intensity of the radiation detection signal that is mainly caused by the variation in the detection characteristic between the radiation detection elements, and the radiation detection signal that is mainly caused by the variation in the amplification characteristic of the signal amplification element. An array type radiation detector based on both (D) the correction data stored in the data storage means for individually updating and storing the amplification element correction data for eliminating the variation in the signal strength. And (E) both correction data stored in the data storage means. Data updating means for collecting the data corresponding to the correction data to be updated based on the output signal from the array type radiation detector and updating the corresponding correction data stored in the data storage means. It is what

The invention described in claim 2 is the same as claim 1.
In the radiation imaging apparatus described in (1), (E) the detection element correction data and the amplification element correction data are respectively
(Ea) Offset correction data collected without irradiation with radiation, and (Eb) Sensitivity correction data collected with irradiation with radiation.

The invention described in claim 3 is the same as claim 1
Alternatively, in the radiation imaging apparatus according to claim 2,
(F) The array-type radiation detector is configured so that the gain (amplification factor) can be switched with respect to the radiation detection signal, and (G) the data storage means is the amplification element correction data corresponding to each switchable gain. And the (H) correction calculation means is configured to perform the correction calculation process using the correction data for the amplification element corresponding to the switched gain.
(I) The data update means is configured to update the amplification element correction data corresponding to each gain that can be switched by the array type radiation detector.

[Operation] Next, the operation of the radiation imaging apparatus according to the present invention will be described. According to the invention described in claim 1, between the radiation detection elements, with respect to the radiation detection signal taken out from the array-type radiation detector via the shared signal amplification element in accordance with the detection of the radiation by each radiation detection element. Amplification element that eliminates the variation in the signal intensity of the radiation detection signal that is mainly caused by the variation in the detection element correction data and the amplification characteristic of the signal amplification element that eliminates the variation in the signal intensity of the radiation detection signal that is mainly caused by the variation in the detection characteristic. As a result of performing the correction calculation based on the use correction data, the variation in the signal strength due to the variation in the detection characteristic between the radiation detection elements and the variation in the amplification characteristic between the signal amplification elements is eliminated.

And in the invention described in claim 1,
When updating the correction data for the detection element or the correction data for the amplification element, the correction data for update is collected based on the output signal from the array type radiation detector, and is stored in the data storage means by the data updating means, Update old data by rewriting it to newly collected data.

However, since the correction data for the amplifying element can be updated independently in the data storage means, when the correction data for the amplifying element is updated independently, the data updating means collects only the correction data for the amplifying element. Then, it is sent to the data storage means and rewritten with the old data.

That is, in the array type radiation detector according to the first aspect of the present invention, the variation in the detection characteristics between the radiation detection elements is unlikely to change with time, but the variation in the amplification characteristics of the signal amplification element does not. Focusing on the fact that it easily fluctuates, the correction data for eliminating the variation in the signal intensity of the radiation detection signal is divided into correction data for the detection element that does not easily change over time and correction data for the amplification element that easily changes over time. It is also stored so that only the correction data for the amplifying element, which tends to change with time, is updated so that the change with time of the entire correction data can be suppressed.

When only the correction data for the amplification element is independently updated, the number of signal amplification elements shared by some radiation detection elements is smaller than the number of radiation detection elements. That is, since the number of amplification element correction data is smaller than the number of detection element correction data, the time required for data collection / storage is considerably shortened, and the correction data update time is sufficiently shortened.

According to the second aspect of the present invention, each of the detection element correction data and the amplification element correction data is collected together with the offset correction data and the radiation irradiation collected without the irradiation of the radiation. And sensitivity correction data.

Then, the radiation detection signal extracted from the array type radiation detector is subjected to offset correction calculation processing based on the offset correction data of each of the correction data, and then the sensitivity correction data of each of the correction data. As a result, the variation of the signal intensity due to the variation of both characteristics of the offset and the sensitivity between the radiation detection elements and between the signal amplification elements is eliminated.

According to the third aspect of the present invention, the data updating means collects the amplification element correction data corresponding to each switchable gain (for the radiation detection signal) in the array type radiation detector. It is sent to and stored in the data storage means. When the gain (amplification factor) of the signal amplification element in the array-type radiation detector is switched, the correction calculation means uses the amplification element correction data corresponding to the switched gain of the signal amplification element to detect the radiation detection signal. A correction calculation process for is performed.

That is, in the case of the invention described in claim 3,
Amplification element correction data corresponding to each gain that can be switched in the array-type radiation detector is collected and stored, and the correction calculation processing that eliminates the variation in the signal intensity of the radiation detection signal is performed in the array-type radiation detector. Since appropriate amplification element correction data that matches the gain of the signal amplification element that is set to be switched is used, the correction calculation processing is performed accurately.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of an X-ray imaging apparatus according to the embodiment, and FIG.
FIG. 3 is a schematic diagram showing the configuration of the imaging system side of the line imaging apparatus, and FIG. 3 is a plan view showing the schematic configuration of a flat panel X-ray sensor as an array radiation detector.

As shown in FIGS. 1 to 3, the X-ray imaging apparatus includes an X-ray tube 1 which is a radiation irradiating means for irradiating the subject M with X-rays as radiation, and X-ray detection as a radiation detecting element. A flat panel X-ray sensor 2 (hereinafter, appropriately referred to as a “panel type sensor”) in which a large number of elements 2A are arranged vertically and horizontally on a detection surface 2a is a subject M placed on a top plate 3. X-ray detection signals (radiation detection signals) output from the panel-type sensor 2 in association with the X-ray irradiation of the subject M on the control system side of the panel-type sensor 2 in the latter stage. According to the above, the X-ray image of the subject M is obtained.

The X-ray tube 1 for X-ray irradiation has a high voltage generator 5
Tube voltage by the control of the irradiation control unit 4 including
It is configured to irradiate the subject M with X-rays according to set irradiation conditions such as a tube current.

In the panel type sensor 2, a large number of X-ray detection elements 2A are arranged on the detection surface 2a in an XY matrix (for example, [X: 1.
024] × [Y: 1024] matrix), and is configured to convert incident X-rays into X-ray detection signals for creating an X-ray image and output the signals to the control system side.

The top plate 3 for moving the subject is controlled by the top plate driving unit 6 to move the subject M on the X (horizontal) side.
It is configured to be moved in each of Y (vertical direction = body axis direction of the subject M) and Z (vertical).

The control by the irradiation control unit 4 and the top plate drive unit 6 is controlled by the photographing control unit 8 according to the input operation from the input unit 7 composed of an input device such as a console or a mouse and the photographing progress situation. It is performed in accordance with a command signal issued from timely.

On the other hand, on the control system side of the embodiment apparatus, an X-ray detection signal memory (original image memory) 9 for storing an X-ray detection signal output from the panel type sensor 2 in association with X-ray irradiation.
And a signal processing unit 10 for performing various necessary signal processings on signals output from the panel type sensor 2, and an X-ray image memory 11 for storing X-ray images obtained by the necessary signal processings. At the same time, a display monitor 12 that displays the X-ray image stored in the X-ray image memory 11, and an image printing device that prints the X-ray image stored in the X-ray image memory 11 on a film and outputs it as an image photograph (laser type Imager) 13 and the like.

The signal processing section 10 performs, as necessary signal processing, so-called X-ray image creation processing such as edge enhancement, filtering, or digital subtraction (DSA). It is configured to perform a correction data collection / storage process based on the output signal and a correction calculation process for eliminating the variation in the signal intensity of the X-ray detection signal based on the correction data.

Next, the structure of the panel type sensor 2 for detecting X-rays will be specifically described. FIG. 4 is a schematic sectional view of the sensor portion of the panel type sensor 2. FIG. 5 is a block diagram showing the overall configuration of the panel-type sensor 2. Normally, about 500 to 5000 X-ray detecting elements 2A in the X direction and 50 in the Y direction.
It is a matrix configuration with about 0 to 5000 arranged,
For convenience of explanation, the X-ray detection element 2 is shown below as shown in the figure.
A 5 × 5 matrix configuration in which five A's are arranged in the X direction and five A's are arranged in the Y direction will be described.

As shown in FIG. 4, the panel type sensor 2 is
A semiconductor film 2 which is an X-ray sensitive film (for example, an amorphous Se thick film) in which carriers are generated by the incidence of X-rays.
1, a voltage application electrode 22 provided on the surface of the semiconductor film 21 on the X-ray incidence side, a carrier collection electrode 23 provided on the back surface of the semiconductor film 21 on the X-ray non-incidence side, and a collection of the carrier collection electrode 23. The sensor unit is provided with a capacitor Ca for accumulating charges for accumulating carriers and a thin film transistor (TFT) of a switch element 24 for extracting charges accumulated in the capacitor Ca, which is normally off (shut off) for extracting charges.

That is, while the bias voltage is being applied to the voltage applying electrode 22, the carriers generated by the X-ray irradiation are sent from the carrier collecting electrode 23 to the capacitor Ca and accumulated, and at the read timing, the switch element. When 24 is turned on (connected), the accumulated charge is read out as a detection signal.

Therefore, in the case of the panel type sensor 2, 1
This means that each X-ray detection element 2A is composed of the semiconductor film 21 and a part of the voltage application electrode 22, the carrier collection electrode 23, the switch element 24, and the capacitor Ca.

In the panel type sensor 2, the source of the thin film transistor for the switch element 24 in the X-ray detection element 2A is connected to the readout wiring 25 in the lateral (X) direction,
The gate is connected to the read wiring 26 in the vertical (Y) direction.

As shown in FIG. 5, the read wiring 25 is connected to a charge-voltage converter type preamplifier 28 as a signal amplifying element provided for each read wiring 25 in the signal output circuit 27. And 5 X in a row
The line detection element 2A is configured so that an X-ray detection signal is extracted via the same preamplifier 28. That is, one shared preamplifier 28 is provided for each of the five X-ray detection elements 2A for one column.

The signal output circuit 27 of the panel type sensor 2 is
Equipped with a multiplexer function and AD conversion function, each X
The signal of the line detection element 2A is configured to be read out in the form of a digital signal in a time series, and the gain (amplification factor) for the X-ray detection signal can be switched. The operation is performed using the input unit 7 or the like.

As a concrete gain switching method in the signal output circuit 27, in addition to a method of changing the gain of the gain switchable active circuit element interposed between the outputs of the preamplifier 28 and the signal output circuit 27, A method of switching the gain of each preamplifier 28 itself may be used.

For example, if the X-ray incident amount is small, the gain is set large, and conversely, if the X-ray incident amount is large, the gain is set small, and the X-ray detection signal is output from the panel type sensor 2 with an appropriate signal intensity. It can be taken out.
Here, for convenience of explanation, it is assumed that the gain for the X-ray detection signal has three stages and can be selectively set to any of the gains GA to GC, but the number of stages for switching the gain is set to a specific stage number. It is not limited.

Further, in the case of the panel type sensor 2, a scanning signal for signal extraction is sent from the readout controller 20 to a multiplexer (not shown) of the signal output circuit 27 and the gate driver 29. The identification of each X-ray detection element 2A is performed by identifying each X-ray detection element 2A along the arrangement in the X and Y directions.
Addresses sequentially assigned to A (for example, 1 to 1)
024), the scanning signal for taking out becomes a signal for designating an X-direction address or a Y-direction address, respectively.

The X-ray detection elements 2A are selected in column units as the extraction voltage is applied from the gate driver 29 to the Y-direction read wiring 26 in accordance with the Y-direction scanning signal. Then, the multiplexer of the signal output circuit 27 is switched according to the scanning signal in the X direction, so that the capacitor C of the X-ray detection element 2A in the selected column is switched.
The electric charge accumulated in a is sent as an X-ray detection signal from the panel type sensor 2 to the X-ray detection signal memory 9 via the preamplifier 28 of the signal output circuit 27. The X-ray detection signal memory 9 is a frame memory in which X-ray detection signals are stored with the same addressing as that of the panel type sensor 2.

The panel type sensor 2 described above is used.
In the X-ray detection signal output from the X-ray detection element 2A, there are variations in the signal strength of the X-ray detection signal, which are mainly caused by variations in the detection characteristics between the X-ray detection elements 2A and variations in the amplification characteristics of the preamplifier 28. The embodiment apparatus is provided with a configuration for sufficiently eliminating the variation in signal strength.

First, in the embodiment apparatus, as shown in FIG. 1, detection element correction data for eliminating the variation in the signal intensity of the X-ray detection signal, which is mainly caused by the variation in the detection characteristics between the X-ray detection elements 2A. The correction table 14 for the detection element for storing the correction element and the correction table 15 for the amplification element for storing the correction data for the amplification element that eliminates the variation in the signal intensity of the X-ray detection signal mainly caused by the variation in the amplification characteristic of the preamplifier 28. It is provided as a data storage means. Further, the amplification element correction table 15 is configured so that the data can be updated independently of the detection element correction table 14.

Further, as shown in FIG. 6, the detection element correction table 14 includes an offset correction table 14A for storing offset correction data collected without X-ray irradiation and an X-ray irradiation. And a sensitivity correction table 14a for storing the collected sensitivity correction data.

Further, in the amplification element correction table 15,
Offset correction tables 15A to 15C that store offset correction data collected without X-ray irradiation,
It has sensitivity correction tables 15a to 15c for storing sensitivity correction data collected with X-ray irradiation.

The offset correction tables 15A-1
5C stores offset correction data corresponding to the gains GA to GC that can be switched in the signal output circuit 27 of the panel type sensor 2, and the sensitivity correction tables 15a to 15c store the signal output of the panel type sensor 2. Sensitivity correction data corresponding to each of the switchable gains GA to GC in the circuit 27 is stored.

On the other hand, as shown in FIG. 1, the signal processing unit 10 of the embodiment apparatus detects X-rays output from the panel type sensor 2 based on the correction data stored in both correction tables 14 and 15. A correction calculation means 16 for performing a correction calculation process of a signal, and a correction table 14 in which data corresponding to correction data to be updated in both correction tables is collected based on an output signal from the panel type sensor 2 and the data is stored. , 15 to read the data and update it with new correction data.

That is, the variation in the signal intensity between the X-ray detection signals includes two variations due to the variation in the detection characteristics between the X-ray detection elements 2A and the variation in the amplification characteristics between the preamplifiers 28. There is. Further, variations in the detection characteristics between the X-ray detection elements 2A and variations in the amplification characteristics between the preamplifiers 28 include variations in offset (output when X-rays are not irradiated) characteristics and sensitivity (X-ray conversion rate) characteristics, respectively. At the same time, variations in the amplification characteristics among the preamplifiers 28 also vary depending on the switchable gains GA to GC in the signal output circuit 27 of the panel type sensor 2.

Therefore, in the case of the apparatus of the embodiment, the offset correction data and the sensitivity correction data are collected and stored as the detection element correction data, and the signal output circuit 27 of the panel type sensor 2 is switched as the amplification element correction data. Offset correction data and sensitivity correction data are collected and stored for each possible gain GA to GC.
Then, appropriate correction data is selected from the stored data and correction calculation processing of the X-ray detection signal output from the panel type sensor 2 is performed to eliminate the variation in the signal intensity between the X-ray detection signals. The line image is prevented from having an artifact.

Next, the configuration of the collection / storage process of each correction data and the correction calculation process of the X-ray detection signal will be specifically described. First, collection and storage of offset correction data will be described with reference to the drawings. FIG. 7 is a flowchart showing a process of collecting and storing offset correction data, and FIGS. 8A and 8B are schematic diagrams showing a storage state of offset correction data.

[Step S1] The signal output circuit 27 of the panel type sensor 2 is set to the gain GA.

[Step S2] All X in non-irradiated X-ray
X-ray detection signals C _{11 to} C _{ij of the} line detection elements 2A _{11 to} 2A ₅₅
The C ₅₅ is stored in the X-ray detection signal memory 9. It is preferable that the X-ray detection signals C _{11 to} C ₅₅ are collected a plurality of times (for example, 16 times) and averaged to sufficiently remove noise. Further, i corresponds to an address in the X direction and j corresponds to an address in the Y direction.

[Step S3] Five X-ray detection elements 2 each in a column (i is the same) sharing the same preamplifier 28.
The average value of the X-ray detection signals C _{i1 to} C _i5 of A is i = 1, 2,
Offset correction data D _i of the amplification element correction data at the gain GA are obtained for five cases of 3, 4, and 5.
[= (C _i1 + C _i2 + C _i3 + C _i4 + C _i5 ) / 5]
As shown in FIG. 8A, the offset correction table 15A
Remember.

That is, the offset correction data D _i obtained by averaging the X-ray detection signals of the five X-ray detection elements 2A shows the variation in the offset characteristics of the X-ray detection elements 2A due to the averaging of the signals. Relationship has been canceled,
Only the variation in the offset characteristic of the preamplifier 28 is relevant data.

[Step S4] Each X-ray detection signal C_ijOr
Corresponding offset correction data D _iOperation to subtract
For i, j = 1,2,3,4,5
For offset correction of detection element correction data
Data E_ij(= C_ij-D_i ) Is obtained, and this is shown in FIG.
Stored in the offset correction table 14A as shown in
It

Since the offset correction data E _ij of the detection element correction data does not have a variable element due to gain switching, it is not necessary to obtain data for each gain. However, when the offset correction data E _ij of the detection element correction data is used with a gain Gb different from the gain Ga at the time of collection, a coefficient (Gb / Ga) due to the difference in gain
Must be multiplied and used as E _ij · (Gb / Ga).

[Step S5] After the signal output circuit 27 of the panel type sensor 2 is set to the gain GB, the offset correction data D _i of the amplification element correction data at the gain GB is obtained in the same manner as above, and the offset is corrected. The correction table 15B is stored.

[Step S6] After the signal output circuit 27 of the panel type sensor 2 is set to the gain GC, the offset correction data D _i of the amplification element correction data at the gain GC is obtained in the same manner as above, and the offset is corrected. When stored in the correction table 15C, the collection and storage of the offset correction data is completed.

Next, the collection and storage of sensitivity correction data will be described with reference to the drawings. FIG. 9 is a flowchart showing a process of collecting and storing sensitivity correction data, FIG.
(A), (b) is a schematic diagram which shows the storage condition of the data for sensitivity correction.

[Step F1] The signal output circuit 27 of the panel type sensor 2 is set to the gain GA.

[0061] stores [Step F2] X-ray detection signals H ₁₁ ~H _ij ~H ₅₅ of the total X-ray detected by the X-ray irradiation state in a predetermined irradiation condition element 2A ₁₁ to 2A region ₅₅ to the X-ray detection signal memory 9 . The X-ray detection signals H _{11 to} H ₅₅ are transmitted a plurality of times (for example, 1
It is preferable to collect and average six times) to sufficiently remove noise.

[Step F3] Offset processing is performed by subtracting the offset amount (D _i + E _ij ) from each X-ray detection signal H _ij for 25 cases of i, j = 1, 2, 3, 4, and 5. X-ray detection signal h _ij [= H
_ij- (D _i + E _ij )], the X of the five X-ray detection elements 2A in each one column which shares the same preamplifier 28 is further calculated.
The average value of the line detection signals h _{i1 to} h _i5 is i = 1, 2, 3, 4,
5 are obtained for five cases, and the obtained data are used for sensitivity correction data I _i [= (h
_i1 + h _i2 + h _i3 + h _i4 + h _i5 ) / 5], which is stored in the sensitivity correction table 15a as shown in FIG.

That is, the sensitivity correction data I obtained by averaging the X-ray detection signals of the five X-ray detection elements 2A.
_i loses the relationship with the variation in the sensitivity characteristic of the X-ray detection element 2A due to the averaging of the signals, and becomes data relating only to the variation in the sensitivity characteristic of the preamplifier 28.

[Step F4] Each X-ray detection signal h _ij [= H _ij − (D _i + E _ij )] excluding the offset is divided by the sensitivity correction data I _i of the amplification element correction data obtained in step S3. The calculation processing (h _ij ÷ I _i ) for calculation is i, j =
Do 25 cases of 1, 2, 3, 4, 5
Sensitivity correction data J _ij (= h _ij ÷ I _i ) of the correction data for the detection element, which eliminates the influence of the offset characteristics and the variations in the sensitivity characteristics between the preamplifiers 28, as shown in FIG. Correction table 14a
Remember.

Note that the sensitivity correction data J _ij of the detection element data does not have to be obtained for each gain because there is no variable element due to gain switching. Further, the correction data J _{ij is} acquired with a gain Gb different from the gain Ga at the time of collection.
Even when using, since the correction data J _ij is incorporated in the correction calculation as a division factor, it is not necessary to multiply and use the coefficient (Gb / Ga) due to the difference in gain, and it is used as it is.

[Step F5] After setting the signal output circuit 27 of the panel type sensor 2 to the gain GB, the sensitivity correction data I _i of the amplification element correction data at the gain GB is obtained in the same manner as described above, and the offset is obtained. Correction table 15
Store in b.

[Step F6] The signal output circuit 27 of the panel type sensor 2 is set to the gain GC, and the sensitivity correction data I _i of the amplification element correction data at the gain GC is obtained in the same manner as described above to obtain the offset correction table 15c. Memorize to

Next, the correction calculation processing of the X-ray detection signal will be described with reference to the drawings. FIG. 11 is a flowchart showing the correction calculation processing process of the X-ray detection signal.

[Step K1] X-ray irradiation of the subject M
All X-ray detection elements 2A₁₁~ 2A ₅₅X-ray detection signal
T₁₁~ T_ij~ T₅₅Are stored in the X-ray detection signal memory 9.

[Step K2] Offset correction calculation processing [T _ij − (D _i + E _ij ) = t _ij ] for each X-ray detection signal T _ij using the offset correction data E _ij and D _i.
Is performed for 25 cases of i, j = 1, 2, 3, 4, 5 to obtain an X-ray detection signal t _{ij from} which variations in signal strength due to variations in offset characteristics are removed.

Regarding E _ij , the panel type sensor 2
In the case where the gain of the signal output circuit 27 is a gain Gb different from the gain Ga when the offset correction data E _ij is collected, [T _ij − (D _i + E _ij )] instead of [T _ij
-(D _i + E _ij × Gb ÷ Ga)] is performed. As the offset correction data D _i , data corresponding to the gain at the time of collection of the signal output circuit 27 is used.

[Step K3] Sensitivity correction data I _i , J for each X-ray detection signal tij after offset correction
Correction calculation processing using _ij [t _ij / (I _i · J _ij ) =
U _ij ], for i, j = 1, 2, 3, 4, 5 in 25 cases. Then, the 25 X-ray detection signals U ₁₁ to U ₁₁ in which the variations in the signal strength due to the variations in the characteristics between the X-ray detection elements 2A and the preamplifier 28 are eliminated.
U ₅₅ is obtained.

[Step K4] The signal processing unit 10 stores the X-ray image in the X-ray image memory 11 in accordance with the 25 X-ray detection signals U _{11 to} U _{55 that have} undergone the correction calculation process.

In the case of the X-ray image pickup apparatus of the above-mentioned embodiment, in the panel type sensor 2, as described above, the correction data for eliminating the variation in the signal intensity of the X-ray detection signal is hard to change with time. The correction data for the detection element and the correction data for the amplification element, which easily change with time, are stored separately in the correction tables 14 and 15. Further, it is also configured to update only the correction data for the amplifying element, which easily changes with time, to suppress the change with time of the entire correction data.

When only the amplification element correction data is updated independently, the number of preamplifiers 28 is smaller than the number of X-ray detection elements 2A, and the number of amplification element correction data is larger than the number of detection element correction data. Since it is small, the time required for data collection and storage is considerably shortened, and the update time of correction data is very short.

That is, in the case of independently updating only the correction data for the amplifying element, from the above process to step S4.
And step F4 is removed, and offset correction data D _i and sensitivity correction data I of the amplification element correction data are removed.
As a result of only collecting / storing _i and updating the data, the time required for collecting / storing the data is considerably shortened.

In the case of the apparatus of the embodiment, for example, only the correction data for the amplification element is independently updated every day, and the correction data for the detection element and the correction data for the amplification element are updated once a week. If the correction data for the detector is 6
The data update time is shortened by the time required to update the data once.

The present invention is not limited to the above embodiment, but can be modified as follows. (1) In the case of the embodiment, when the offset correction data D _i and the sensitivity correction data I _i of the amplification element correction data are obtained, all signals of the X-ray detection elements for one vertical column are averaged. However, in the case where the number of X-ray detection elements for one vertical column is large, for example, it is possible to average only the signals of an appropriate specific number of the X-ray detection elements for one vertical column.

(2) In the case of the embodiment, both the correction data for the detecting element and the correction data for the amplifying element have a configuration in which both the correction data for the offset characteristic and the correction data for the sensitivity characteristic are collected and stored. For each correction data, the correction data of only one of the offset characteristic variation and the sensitivity characteristic variation is collected and stored, or the correction data that collects the offset characteristic variation and the sensitivity characteristic variation together is collected. -The configuration may be stored.

(3) In the case of the embodiment, the correction data is updated regularly. However, when the operator feels the need, the correction data is updated by an input operation from the input unit 7. It is also possible.

(4) The panel type sensor 2 of the embodiment was of the direct conversion type, but after the incident X-ray was first converted into light,
It may be an indirect conversion type sensor in which converted light is converted into an electric signal.

(5) The X-ray imaging apparatus of the embodiment may have the configuration of the X-ray CT apparatus in addition to the configuration of the X-ray fluoroscopic imaging apparatus. In addition to X-rays, radiation targeted by the present invention includes, for example, neutron rays and gamma rays.

[0083]

As described above in detail, according to the radiation imaging apparatus of the first aspect, the correction data for eliminating the variation in the signal intensity of the radiation detection signal is used for the detection element which is less likely to change with time. The correction data and the correction data for the amplification element that easily changes with time are stored separately, and only the correction data for the amplification element that easily changes with time is independently updated from the correction data. It is also configured to suppress the variation with time as a whole.

That is, when only the amplification element correction data is independently updated, the number of signal amplification elements is smaller than the number of radiation detection elements, and the number of amplification element correction data is the number of detection element correction data. Therefore, the time required for data collection and storage is considerably shortened, and the correction data update time can be shortened sufficiently.

Further, according to the radiation imaging apparatus of the second aspect, the correction data for the detection element and the correction data for the amplification element are respectively accompanied by offset correction data and radiation irradiation collected without radiation irradiation. It is composed of the sensitivity correction data collected by the correction calculation processing, and the variation in the signal intensity of the radiation detection signal due to the variation in both the characteristics of the offset and the sensitivity between the radiation detection elements and between the signal amplification elements is eliminated by the correction calculation process. The variation in the signal intensity of the radiation detection signal is sufficiently eliminated.

According to the radiation imaging apparatus of the third aspect, the amplification element correction data corresponding to each gain that can be switched in the array type radiation detector is collected and stored, and the radiation detection signal In the correction calculation process that eliminates the variation in signal strength, the correction calculation process is always performed accurately because the correction data for the amplification element that is appropriate for the gain of the signal amplification element that is switched and set in the array-type radiation detector is used. As a result, variations in the signal intensity of the radiation detection signal are sufficiently eliminated.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an X-ray imaging apparatus according to an embodiment.

FIG. 2 is a schematic diagram showing a configuration of an X-ray imaging apparatus of an embodiment on an imaging system side.

FIG. 3 is a plan view showing a schematic configuration of a flat panel X-ray sensor.

FIG. 4 is a schematic cross-sectional view showing an internal configuration of a sensor unit of a panel type sensor.

FIG. 5 is a block diagram showing an overall configuration of a panel type sensor.

FIG. 6 is a block diagram showing a detailed configuration of a correction table.

FIG. 7 is a flowchart showing a process of collecting and storing offset correction data.

8A and 8B are schematic diagrams showing a storage state of offset correction data.

FIG. 9 is a flowchart showing a process of collecting and storing sensitivity correction data.

10A and 10B are schematic diagrams showing a storage state of sensitivity correction data.

FIG. 11 is a flowchart showing a correction calculation processing process of an X-ray detection signal.

FIG. 12 is a plan view showing an arrangement of X-ray detection elements of a panel type sensor of a conventional device.

FIG. 13 is a block diagram showing a main configuration of a control system side of a conventional device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... X-ray tube 2 ... Flat panel type X-ray sensor 2A ... X-ray detection element 2a ... Detection surface 14 ... Detection element correction table 15 ... Amplification element correction table 16 ... Correction calculation means 17 ... Data update means 28 ... Preamplifier (the signal amplifying element) D ₁ ~D ₅ ... offset correction data I ₁ ~I ₅ ... sensitivity correction data E ₁₁ to E ₅₅ ... offset correction data J ₁₁ through J ₅₅ ... sensitivity correction data M ... subject

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 27/14 H01L 27/14 K F term (reference) 2G001 AA01 BA11 CA01 DA08 FA06 FA10 GA06 HA13 JA11 KA03 LA01 2G088 EE01 EE29 FF02 GG21 JJ05 LL12 LL15 4C093 AA02 AA29 CA09 CA10 CA13 CA36 EA02 EB13 EB17 FC16 FC17 GA05 4M118 AA05 BA07 CA11 CA15 CB05 GA10

Claims (3)

[Claims] 1. A (A) radiation irradiating means for irradiating a subject with radiation, and (B) a multiplicity of radiation detection elements arranged on a detection surface and commonly provided for each of a plurality of radiation detection elements. For the array type radiation detector in which the radiation detection signal is read out through the signal amplification element, and (C) the detection element for eliminating the variation in the signal intensity of the radiation detection signal mainly caused by the variation in the detection characteristic between the radiation detection elements. (D) a data storage unit for individually updating and storing the correction data and the correction data for the amplification element that eliminates the variation in the signal intensity of the radiation detection signal mainly caused by the variation in the amplification characteristic of the signal amplification element. A supplementary correction processing for correcting the radiation detection signal output from the array-type radiation detector based on both correction data stored in the data storage means. Positive operation means and (E) data corresponding to the correction data to be updated of both correction data stored in the data storage means are collected based on the output signal from the array type radiation detector and stored in the data storage means. A radiation imaging apparatus, comprising: a data updating unit that updates the corresponding correction data. 2. The radiation imaging apparatus according to claim 1, wherein (E) the correction data for the detection element and the correction data for the amplification element are each (Ea) collected for the offset correction data without irradiation with radiation. And (Eb) sensitivity correction data collected with radiation irradiation. 3. The radiation imaging apparatus according to claim 1 or 2, wherein the (F) array type radiation detector is configured so that the gain (amplification factor) for the radiation detection signal can be switched. (G) The data storage means is configured to store the amplification element correction data corresponding to each switchable gain, and the (H) correction calculation means is configured to store the amplification element correction data corresponding to the switched gain. Is used to perform correction calculation processing, and (I) the data updating means is configured to update the amplification element correction data corresponding to each gain that can be switched by the array-type radiation detector. A radiation imaging apparatus characterized in that.