JP2002303592A - Tomographic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide tomographic equipment capable of quickly calculating a detection element position of a detector whereon the rotational axis of a rotational scan motion is projected. SOLUTION: Since a calculation section 53 calculates the position of detection element 2 of a detector 3 whereon rotation scan axis Z is projected based on first detection data of which a phantom F mounted in the vicinity of rotation center on a table 4 is picked up in a state that the phantom F is at a first angular position in rotation scanning and second detection data of which the phantom F is picked up in a state that the phantom F is at a second angular position in opposite phase of the first angular position, processing only two transmitted X-ray detection data of which the phantom F is picked up only twice for an angle and another rotated by 180 deg. from it, is sufficient and the rotation center of the detector 3 can be quickly found.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tomographic apparatus used in the medical and industrial fields for performing tomographic imaging of an object by relatively rotating and scanning an irradiation source and a detector and the object around the object. More particularly, the present invention relates to a technique for quickly calculating a position of a detection pixel of a detector on which a rotation center axis of a rotational scanning motion is projected.

[0002]

2. Description of the Related Art As a conventional tomography apparatus, for example, an X-ray CT (X-ray computer tomography) type X-ray tomography apparatus (hereinafter referred to as X-ray C
Called T device. ). This X-ray CT apparatus has an X-ray tube that irradiates a subject with X-rays in the form of a fan beam, and a number of X-ray detection elements arranged in a line with the subject interposed therebetween. A multi-channel row-type X-ray detector for detecting a line of X-rays is disposed opposite to the central axis of the rotational scanning set in substantially the center of the region of interest of the subject. Around one turn (at least half a turn) by synchronizing the X-ray tube and the row X-ray detector
By imaging while scanning, transmission X-ray detection data (transmission image) for one rotation (at least half a rotation) around the body axis of the subject is acquired.

In this X-ray CT apparatus, a predetermined image reconstruction process is performed on a plurality of transmission images acquired at each scanning position, so that a tomographic image of a region of interest (a body of the subject) is obtained. (A tomographic image viewed from the axial direction), and the generated tomographic image is displayed on a monitor or the like.

As in the above-mentioned X-ray CT apparatus, an X-ray tube and a row-type X-ray detector are photographed while rotating and scanning around a subject, and a plurality of transmission images (a group of transmission X-ray detection data ), The center position of the rotational scanning movement, that is, the position of the detection pixel (X-ray detecting element) of the column type X-ray detector on which the rotational center axis of the rotational scanning movement is projected is determined by the image. Since it is an important element in the reconstruction process,
Its detection is essential.

[0005]

However, the prior art having such a configuration has the following problems. That is, there is a problem that the position of a detection pixel of a detector (for example, a column type X-ray detector) on which the rotation center axis of the rotational scanning motion is projected cannot be quickly calculated.

Specifically, in a conventional tomography apparatus,
The X-ray tube and the row type X-ray detector and the table on which the subject is installed are relatively rotated around the subject and rotationally scanned to perform tomography. The pre-shooting for obtaining is performed in advance as described below. A test object (marker) is arranged near the center of rotation on the table, and the table on which the test object is arranged is rotated by half or one rotation tomographically scan, and transmitted X-ray detection data for half or all of the circumference is obtained. (A plurality of transmission images) are collected, and image processing similar to averaging processing and image reconstruction processing is performed on the collected transmission X-ray detection data for half a circle or the entire circumference to rotate the image. Since the position of the detection pixel of the column type X-ray detector on which the rotation center axis of the scanning motion is projected is calculated, the calculation takes time. In particular, in a tomography apparatus in which the positional relationship between the X-ray tube and the row-type X-ray detector is variable, or in a tomography apparatus in which the center position of the rotational scanning movement is movable, the rotational scanning movement is changed each time it changes or moves. It is necessary to re-detect the position of the detection pixel of the column type X-ray detector on which the rotation center axis is projected, which takes a long time. Further, in the flat plate two-dimensional detector developed recently, the amount of collected data is enormous and the processing time becomes very long.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and a tomographic apparatus capable of quickly calculating a position of a detection pixel of a detector on which a rotation center axis of a rotational scanning motion is projected. The purpose is to provide.

[0008]

The present invention has the following configuration to achieve the above object. That is, the tomographic imaging apparatus according to claim 1 is: (a) an irradiation source for irradiating the subject with an electromagnetic wave having transparency to the subject; and (b) an opposing arrangement to the irradiation source across the subject. And
A detector for detecting an electromagnetic wave transmitted through the subject by a plurality of detection pixels arranged in parallel, and (c) a setting table for setting the subject, and (d) the irradiation source and the detector, In a tomography apparatus for performing tomography by rotating and scanning a mounting table relatively around a subject, (e) a test object installed near a rotation center on the mounting table is positioned at a first angular position in the rotation scanning. The first image of this test piece taken in a certain state
A rotation center axis is projected based on the detection data and second detection data obtained by photographing the device under test in a state where the device under test is at a second angle position opposite to the first angle position. An arithmetic unit for calculating a position of a detection pixel of the detector is provided.

Further, the tomographic apparatus according to claim 2 is
2. The tomographic imaging apparatus according to claim 1, wherein the detector is a linear detector in which a plurality of detection pixels are arranged one-dimensionally or a surface in which a plurality of detection pixels are arranged in a two-dimensional matrix. Characterized in that it is a state detector.

[0010] The tomographic apparatus according to the third aspect is characterized in that:
2. The tomography apparatus according to claim 1, wherein the detector is a planar detector in which a plurality of detection pixels are two-dimensionally arranged in a matrix, and the arithmetic unit is configured to rotate the planar detector in a rotational scanning direction. 3. For each of a predetermined number of detection pixel lines substantially parallel to, the position of the detection pixel on which the rotation center axis is projected is calculated based on the first and second detection data, and the rotation center axis is calculated based on the calculated positions. It is characterized in that the inclination is calculated.

The tomographic apparatus according to claim 4 is
4. The tomographic imaging apparatus according to claim 1, wherein the calculation unit captures an image of the device under test in a state where the device under test is within a predetermined angle range centered on the first angular position. 5. The first detection data is calculated by averaging a series of detection data, and the series of detection data obtained by photographing the test object in a state where the test object is within a predetermined angle range around the second angular position is averaged. And calculating the second detection data, and calculating the position of the detection pixel on which the rotation center axis is projected based on the calculated first and second detection data.

[0012]

The operation of the present invention is as follows. That is,
According to the first aspect of the present invention, an irradiation source that irradiates the subject with an electromagnetic wave having transparency to the subject, and a plurality of irradiation sources arranged in parallel to the irradiation source with the subject interposed therebetween. A detector that detects an electromagnetic wave transmitted through the subject by the detection pixels and a tomographic image by relatively rotating and scanning the mounting table around the subject, such as before the so-called actual tomographic imaging, the rotation center Is performed in advance as described below. The calculation unit is configured to: first detection data obtained by imaging the test object in a state where the test object installed near the rotation center on the installation table on which the object is installed is at the first angular position in the rotational scanning; Based on the second detection data obtained by photographing the test object in a state where the test object is in the second angular position having the opposite phase to the first angular position, the detection pixel of the detector on which the rotation center axis is projected is obtained. Calculate the position.

Therefore, an image is taken while scanning the irradiation source and the detector and the installation table on which the test object is installed near the center of rotation so as to make a half turn or one turn around the test object. A conventional method of obtaining a rotation center of a detector by performing predetermined image processing on a plurality of transmission images (a group of transmission X-ray detection data) for a half or entire circumference obtained by this imaging is used. , The specimens are placed in opposite phases (180 ° different).
Photographing is performed in the state of being in the second angular position, that is, photographing is performed only for two times of a certain angle and an angle rotated by 180 ° therefrom, and two pieces of transmitted X-ray detection data are collected. Since the rotation center of the detector is obtained based on this, the time required for collecting the transmitted X-ray detection data is reduced, and the data processing time is also reduced because only the arithmetic processing of the two transmitted X-ray detection data is required. You.

According to the second aspect of the present invention, as the detector, a linear detector in which a plurality of detection pixels are arranged one-dimensionally or a plurality of detection pixels are arranged in a two-dimensional matrix. Even when using a placed planar detector,
The center of rotation in the detector can be quickly obtained.

According to the third aspect of the present invention, as the detector, a planar detector in which a plurality of detection pixels are arranged two-dimensionally in a matrix is employed, and the arithmetic unit includes the planar detector. For each predetermined number of detection pixel lines substantially parallel to the rotational scanning direction, the position of the detection pixel on which the rotation center axis is projected is defined as the first or first position.
Calculation is performed based on the second detection data, and the inclination of the rotation center axis is calculated based on the calculated positions. Therefore,
The inclination of the rotation center in the detector can be quickly obtained.

According to the fourth aspect of the present invention, the arithmetic unit detects a series of detections of the device under test while the device under test is within a predetermined angle range centered on the first angular position. The data is averaged to calculate first detection data, and a series of detection data obtained by photographing the test object in a state where the test object is within a predetermined angle range around the second angular position is averaged to obtain a second detection data. Detection data is calculated, and the position of the detection pixel on which the rotation center axis is projected is calculated based on the calculated first and second detection data. Therefore, the transmission X-ray detection data is collected for two predetermined angle ranges, and the accuracy of the first and second detection data is improved by each average calculation.
The collection of the transmitted X-ray detection data in each predetermined angle range and the amount of calculation thereof are smaller than the conventional method of collecting and calculating a plurality of transmission images (a group of transmitted X-ray detection data) for a half or entire circumference. Since the data collection amount and the calculation amount for the small angle are small, the calculation accuracy of the rotation center in the detector can be improved while keeping the data collection amount and the calculation amount small.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An X-ray tomography apparatus as an embodiment of the tomography apparatus according to the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 shows an X-ray CT type X-ray tomography apparatus according to a first embodiment of the X-ray tomography apparatus of the present invention (hereinafter, appropriately referred to as an X-ray CT apparatus). It is a block diagram of. The X-ray CT apparatus according to the first embodiment includes an operation unit 10 for inputting various information and instructions, an imaging control unit 20 for controlling X-ray imaging based on the input information and instructions, A driving unit 30 that operates the imaging unit 40 while being controlled by the unit 20; an imaging unit 40 that captures an area of interest of a subject placed on the placement surface 4a of the turntable 4; Image reconstruction for generating a tomographic image of a region of interest of the subject based on the obtained image information (a group of transmitted X-ray detection data);
A data processing unit 50 for storing the generated tomographic image;
A monitor 60 for appropriately displaying the tomographic image stored in the data processing unit 50 is provided.

Hereinafter, the configuration and function of each section will be described in detail. This X-ray CT apparatus, as shown in FIG.
An X-ray tube 1 for irradiating an X-ray FB in the form of a fan beam to the X-ray tube with the X-ray tube irradiating the X-ray FB on the mounting surface 4a of the turntable 4 and a large number of X-ray detection elements 2 arranged in the Y direction A multi-channel row-type (line-type) X-ray detector 3, which is arranged in a line and detects lines of X-rays transmitted through the subject, is arranged to face each other. In a state where the subject is placed on the placement surface 4a, the turntable 4 is rotated by one rotation (at least half a rotation) around the rotation scanning center axis Z set at substantially the center of the region of interest of the subject, and X By scanning the region of interest of the subject by the tube 1 and the row-type X-ray detector 3 so as to capture an image of the region of interest, one rotation (about at least half a rotation) around the body axis of the subject, that is, around the rotational scanning center axis Z. The actual tomography to obtain the transmission image of (minute) is performed. Note that a phantom F as a test object for obtaining a rotation center, which will be described later, is disposed on the mounting surface 4a of the turntable 4 shown in FIG. 1. When performing the above-described actual tomography, The phantom F is removed from the mounting surface 4a, and only the subject is mounted on the mounting surface 4a. Operation unit 1
From 0, the distance from the X-ray tube 1 to the row-type X-ray detector 3 and the circular shape that rotates the turntable 4 around the rotational scanning center axis Z before actual imaging of the region of interest of the subject. The rotation pitch in the direction is input in advance. Note that an input device such as a keyboard, a mouse, and a touch panel is used as the operation unit 10. The X-ray tube 1 described above corresponds to the irradiation source in the present invention, the row type X-ray detector 3 corresponds to the detector (linear detector) in the present invention, and the turntable 4 corresponds to the installation table in the present invention. I do.

In the first embodiment, the X-ray tube 1 and the row type X-ray detector 3 are not rotated, and the turntable located between the X-ray tube 1 and the row type X-ray detector 3 is not used. 4 itself is rotated about the rotational scanning center axis Z, but the turntable 4
Is fixed without rotating, and the mounting surface 4 of the turntable 4 is fixed.
The X-ray tube 1 and the row-type X-ray detector 3 may be rotated in a circular manner in the same plane by synchronizing the X-ray tube 1 and the row-type X-ray detector 3 around the subject on a.

The photographing control unit 20 is connected to the operation unit 10, the driving unit 30, and the data processing unit 50. The imaging control unit 20 controls the driving unit 30 and the data processing unit 50 based on each information set and input from the operation unit 10. Details of the control will be described later in each section.

As shown in FIG. 1, the drive unit 30 has the X-ray tube 1 and the row type X-ray detector 3 opposed to each other across the subject, and mounts the subject on the mounting surface 4a. In this state, the turntable 4 is rotated by the X-ray tube 1 and the row-type X-ray detector 3 while rotating the turntable 4 once (at least half a rotation) around a rotational scanning center axis Z set substantially at the center of the region of interest of the subject. This scans the region of interest of the sample so as to image it.

The imaging unit 40 includes a turntable 4 on which the subject is placed, and an X-ray FB in the form of a fan beam directed toward the subject.
An X-ray tube 1 for irradiating X-rays and a row-type X-ray detector 3 for detecting X-rays transmitted through the subject. The X-ray tube 1 is provided, for example, at one end of a C-shaped arm 5, and the row type X-ray detector 3 is
The C-arm 5 is provided at the other end so as to face the wire tube 1.

The row type X-ray detector 3 is configured to detect an X-ray fluoroscopic image of a subject generated by X-ray irradiation by the X-ray tube 1, convert the X-ray fluoroscopic image into an electric signal as an X-ray detection signal, and output the electric signal. This is an X-ray detector in which a large number of X-ray detection elements 2 as detection pixels are arranged in a line (linear).
It is a dimensional X-ray detector. Column type X-ray detector 3 of embodiment
Are arranged in the horizontal (Y) direction in a plurality (for example, 1024). The detection signals (transmission X-ray detection data) detected by the column type X-ray detector 3 are sequentially
The data is output to the data processing unit 50 in real time.

Next, the configuration and functions of the data processing unit 50 will be described. As shown in FIG. 1, the data processing unit 5
0 is based on a plurality of transmission images (a group of transmission X-ray detection data) detected at each scanning position in the imaging unit 40,
An image processing unit 51 for performing image reconstruction for generating a tomographic image of the region of interest of the subject, and an image information storage unit 52 for storing the tomographic image of the region of interest reconstructed by the image processing unit 51 are provided. I have. Hereinafter, specific functions of the image processing unit 51 and the image information storage unit 52 will be described.

As shown in FIG. 1, the turntable 4 on which the subject is mounted on the mounting surface 4a is rotated once around a rotation scanning center axis Z set substantially at the center of the region of interest of the subject. The X-ray tube 1 and the row-type X-ray detector 3 arranged opposite to each other with the subject interposed therebetween while taking an image of the region of interest of the subject, and the subject is detected at each position in the rotational scanning. A real tomography is performed to collect a plurality of transmission images (a group of transmission X-ray detection data) for the region of interest. The image processing unit 51 performs a predetermined image reconstruction process on the collected transmission images (a group of transmission X-ray detection data) to generate a tomographic image of the region of interest. The generated tomographic image is stored in the image information storage unit 52. When a tomographic image stored in the image information storage unit 52 is displayed and selected by an operator or the like, the display-selected tomographic image (tomographic image viewed from the Z-axis direction) is displayed on the monitor 60. ing.

As described above, a tomographic image is obtained by performing image reconstruction processing on a plurality of transmission images obtained by the above-mentioned actual tomography, but the rotational scanning center axis Z is projected. Since the position of the detection pixel (X-ray detection element 2) of the column type X-ray detector 3 is an important element in performing image reconstruction processing, this detection, that is, detection for obtaining the rotation center, is performed by, for example, This is performed by performing preliminary imaging before performing the actual tomographic imaging described above. Hereinafter, the pre-shooting for obtaining the rotation center will be described in detail.

When performing preliminary photographing for obtaining the rotation center, as shown in FIG. 1, the rotation center on the mounting surface 4a of the turntable 4, that is, the rotation scanning center axis Z
In the vicinity, for example, a thin steel wire for obtaining the rotation center is installed as a phantom F. Here, Phantom F
(For example, a thin steel wire) is adopted, but a shape other than a linear shape such as a tapered shape may be adopted as long as the shape can determine the center of rotation.

Then, as shown in FIG. 2, the linear phantom F is at an arbitrary angular position, for example, at the first angular position θ1 in the rotational scanning, that is, the phantom F at the point a is moved to the X-ray tube 1 and Photographing is performed by the column type X-ray detector 3 to obtain first detection data (transmission X-ray detection data). Next, the turntable 4 is rotated by 180 ° around the rotation scanning center axis Z, and the phantom F is moved to the first angular position θ.
The second angular position θ2 (= θ1 + 180) having a phase opposite to that of the first angular position
°), that is, the phantom F at the point b is photographed by the X-ray tube 1 and the row-type X-ray detector 3,
Acquire detection data (transmission X-ray detection data).

The image processing unit 51 determines whether the phantom F is in the second angular position θ2 (= θ1 + 18) when the phantom F is in the second angular position θ2 (= θ1 + 18).
0 °), based on the second detection data captured in a state where the rotation scanning center axis Z is projected.
The calculation unit 53 for calculating the position of the X-ray detection element 2 is provided. The calculation unit 53 calculates the position of the X-ray detection element 2 of the column type X-ray detector 3 on which the rotational scanning center axis Z is projected, based on the first and second detection data described above.

The calculation of the position of the X-ray detection element 2 of the column type X-ray detector 3 on which the rotational scanning center axis Z is projected by the calculation unit 53 will be described below.

As shown in FIG. 2, the turntable 4 on which the phantom F (thin steel wire) is installed is photographed over the entire circumference while the phantom F is rotated once, for example, and data is collected for the entire circumference. Then, a sinogram (sine waveform) as shown in FIG. 3 is obtained. This sinogram (sine waveform) is an X-ray for detecting a phantom F (thin steel wire) in a column type X-ray detector 3 in which a plurality of X-ray detection elements 2 are arranged in the Y direction as shown in FIG. The detection element 2 is moved within a predetermined range in the Y direction along with the rotation of the turntable 4 (for example, (nm) th to (n +
m) -th range). The vertical axis in FIG. 3 indicates the X-ray detection element 2 of the column type X-ray detector 3.
The horizontal axis in FIG. 3 indicates the data collection angle,
That is, the rotation angle of the turntable 4 is shown.

The first and second detection data described above, that is,
The transmitted X-ray detection data (steel wire data) obtained by the two imagings is obtained by rotating the turntable 4 once and turning the phantom F (thin steel wire) as shown at points a and b in FIG. This indicates two points on the sinogram (sine waveform) obtained by arranging data obtained by taking data over the entire circumference and collecting data for all the circumferences, the phases being opposite to each other. The position of the center line C of this sinogram (sine waveform) is the position of the X-ray detection element 2 of the column type X-ray detector 3 on which the rotational scanning center axis Z is projected. The positions of two points (points a and b) whose phases are exactly opposite are
Paying attention to the fact that the point is always point-symmetric with respect to the intersection of the straight line connecting the points a and b and the center line C of the sine waveform,
Is the average of the position coordinates of these two points (points a and b), thereby obtaining the center position of rotation, that is, the X-ray detection element 2 of the column type X-ray detector 3 on which the rotational scanning center axis Z is projected. The position is calculated. For example, as shown in FIG.
Is in the first angular position θ1, that is, the phantom F at the point a is detected by the (n + m) -th X-ray detecting element 2 of the column type X-ray detector 3, and the phantom F is shifted to the second angular position θ2. State, that is, the phantom F at the point b
Is detected by the (nm) th X-ray detecting element 2 of the column type X-ray detector 3. The calculation unit 53 calculates the two points (a,
The average of the position coordinates of point b) is calculated. That is, ｛(n +
m) + (nm) / 2 = n. As described above, the position of the X-ray detection element 2 of the column type X-ray detector 3 on which the rotational scanning center axis Z is projected is calculated to be the n-th X-ray detection element 2, and the pre-imaging ends. .

The position of the X-ray detecting element 2 of the column type X-ray detector 3 on which the rotational scanning center axis Z is projected, which is calculated by the arithmetic unit 53, is obtained by the above-mentioned actual tomography. A plurality of transmission images (a group of transmission X-ray detection data) is used when performing image reconstruction processing, and a tomographic image is favorably generated.

As described above, in the first embodiment described above, the arithmetic unit 5
Reference numeral 3 denotes a mounting surface 4a of a turntable 4 on which a subject is set.
First detection data obtained by imaging the phantom F in a state where the phantom F installed near the upper rotation center (the rotation scanning center axis Z) is at the first angular position θ1 in the rotation scanning;
The second phase in which the phantom F is in phase opposite to the first angular position θ1
On the basis of the second detection data obtained by imaging the phantom F in the state where the phantom F is at the angular position θ2 (= θ1 + 180 °), the X-ray detection element 2 of the column type X-ray detector 3 on which the rotational scanning center axis Z is projected. Since the position is calculated, the X-ray tube 1 and the row X
The line detector 3 and the turntable 4 in which the phantom F is installed near the center of rotation are scanned while rotating the phantom F around the phantom F by a half turn or one turn. Or, by using a conventional method of obtaining a rotation center in the row type X-ray detector 3 by performing predetermined image processing on a plurality of transmission images (a group of transmission X-ray detection data) for the entire circumference. Instead, the phantom F is photographed in the first and second angular positions θ1 and θ2 having opposite phases (different by 180 °), that is, photographing only two times of a certain angle and an angle rotated by 180 ° therefrom. Since two transmission X-ray detection data are collected and the rotation center in the column type X-ray detector 3 is obtained based on the two transmission X-ray detection data, the time required for collecting the transmission X-ray detection data Shortening can, yet, two only transmitted X-ray detection data can be shortened data processing time since it is only processing.

<Second Embodiment> Next, an X-ray CT apparatus according to a second embodiment of the X-ray tomography apparatus of the present invention will be described. FIG. 4 shows an X-ray CT according to the second embodiment of the present invention.
It is a block diagram of an apparatus. The X-ray CT apparatus according to the second embodiment includes a plurality of (for example, 1024 × 1024) detection elements Du instead of the row-type X-ray detector 3 according to the first embodiment.
The point that a flat panel type X-ray detector 6 arranged in a matrix in a three-dimensional manner is adopted, and the X-ray tube 1 is not irradiated with fan beam-shaped X-rays FB, but is irradiated with cone beam-shaped X-rays CB Except for this point, the configuration is the same as that of the first embodiment described above, so that the configuration and functions of the flat panel X-ray detector 6 will be described in detail.

The flat panel type X-ray detector 6 is configured to detect an X-ray fluoroscopic image of a subject caused by X-ray irradiation by the X-ray tube 1, convert the image into an electric signal as an X-ray detection signal, and output the electric signal. 5. As shown in FIG. 5, a so-called X-ray detector in which a large number of detection elements Du are arranged vertically and horizontally.
It is a dimensional matrix X-ray detector. The arrangement of the detection elements Du in the flat panel X-ray detector 6 of the embodiment is, for example, a horizontal (Y) direction 1024, a vertical (X) direction 10
Assuming a square matrix of 24, FIG.
Only a matrix configuration of a total of 9 matrixes in a 3 × 3 matrix configuration is shown. The flat panel X-ray detector 6, which has a rectangular planar shape, can provide a square detection surface suitable for imaging large parts such as the chest and abdomen, unlike an image intensifier in which the detection surface is limited to a circle. This is also a useful X-ray detector.

As shown in FIG. 6, the flat panel type X-ray detector 6 includes an X-ray conversion layer 12 for converting incident X-rays into charges or light, and a charge or light generated by the X-ray conversion layer 12. It has a laminated structure with a detection array layer 13 in which elements to be detected are arranged vertically and horizontally in a matrix. X-ray conversion layer 1 of this flat panel X-ray detector 6
For example, the plane dimensions of 2 are about 30 cm in length and width.

The flat panel type X-ray detector 6 includes:
The direct conversion type shown in FIG. 7A and the direct conversion type shown in FIG.
There is an indirect conversion type shown below. In the case of the former direct conversion type, the X-ray conversion layer 12 is composed of a selenium layer or a CdZnTe layer which directly converts incident X-rays into electric charges.
5, the charge is detected by the charge collection electrode group formed opposite to and the charge is stored in the capacitor Cs. One charge is detected by each charge detection element 14 and a part of the X-ray conversion layer 12 thereon. The element Du is formed. In the latter case of the indirect conversion type, the X-ray conversion layer 12 comprises a scintillator layer for converting incident X-rays into light, and the detection array layer 13
The light is detected by a photodiode group formed as a photodetecting element 16 on the surface of the device and light is stored in the capacitor Cs. Each of the photodetecting elements 16 and a part of the X-ray conversion layer 12 thereover. One detection element Du is formed.

As shown in FIG. 5, the flat panel X-ray detector 6 includes an X-ray detection substrate 41 on which an X-ray conversion layer 12 and a detection array layer 13 are formed, and a carrier collection of the X-ray detection substrate 41. A capacitor Cs for storing collected carriers (collected charges) via electrodes (charge collecting electrodes);
A thin-film transistor (TFT), which is a switch element 42 for extracting charge that is normally off (cut off) for extracting the charge accumulated in s, a multiplexer 45 of a read circuit in the X and Y directions, and a gate driver 47 Have.

The flat panel X-ray detector 6
As shown in FIG. 5, the source of the thin film transistor for the switch element 42 of the detection element Du is connected to the vertical read wiring 43 arranged in the X-axis direction, and the gate is connected to the horizontal read wiring 46 arranged in the Y-axis direction. Have been. The readout wiring 43 is connected to a multiplexer 45 via a charge-voltage converter group (preamplifier group) 44,
The read wiring 46 is connected to a gate driver 47. In the charge-to-voltage converter group 44, one charge-to-voltage converter group 44 is connected to one read wiring 43, though not shown.

In the case of the flat panel X-ray detector 6, a scanning signal for signal extraction is sent to the multiplexer 45 and the gate driver 47.
Each detection element Du of the detection unit 10 is specified by an address sequentially assigned to each detection element Du along the array in the X direction and the Y direction (for example, 1 to 1024 when the number of detection elements Du is 1024). )
The scanning signal for taking out is a signal for specifying an X-direction address or a Y-direction address, respectively.

As a voltage for taking out is applied from the gate driver 47 to the readout wiring 46 in the Y direction according to the scanning signal in the X direction, each detection element Du is selected in a column unit. Then, by switching the multiplexer 45 according to the scanning signal in the X direction, the charge accumulated in the capacitor Cs of the detection element Du in the selected column is transferred to the charge-voltage changer group 44 and the multiplexer 45.
Will be sent out. As described above, the detection signals detected by the flat panel X-ray detector 6 are sequentially output to the data processing unit 50 in real time. The flat panel X-ray detector 6 described above corresponds to the planar detector in the present invention.

Next, a method of calculating the position of the detection element Du on which the rotational scanning center axis Z is projected in the flat panel X-ray detector 6 shown in FIG. 4 will be described below. As shown in FIG. 4, the flat panel X-ray detector 6
The detection element Du for one line in the arbitrary Y direction is a detection element row 6A, and this detection element row 6A is regarded as the row type X-ray detector 3 of the first embodiment. Then, similarly to the above-described first embodiment, the first and second detection data, that is, the transmission X-ray detection data (points of steel wire) at points a and b shown in FIG. Data) is detected by the detection element array 6A of the flat panel X-ray detector 6, and the arithmetic unit 53 detects two points (a, b) detected by the detection element Du of the detection element array 6A.
Take the average of the position coordinates of point). By doing this,
The position of the detection element Du in the Y direction of the flat panel X-ray detector 6 on which the rotation scanning center axis Z is projected, that is, the position of the detection element Du of the detection element array 6A on which the rotation scanning center axis Z is projected is calculated. You can also.

When a planar detector such as the flat panel type X-ray detector 6 is used, the inclination of the rotation center axis (rotational scanning center axis Z), that is, the rotation scanning center axis Z is equal to the flat panel type. X in the X and Y planes of the X-ray detector 6
It is also possible to detect that it is not parallel to the direction but inclined in the Y direction. Hereinafter, a method of calculating the inclination of the rotational scanning center axis Z in the flat panel X-ray detector 6 will be described.

More specifically, as shown in FIG. 8, a predetermined number of lines (for example,
The detection elements Du in the Y direction for three lines) are defined as detection element rows 6a, 6b, and 6c, respectively.
6b and 6c are regarded as the column type X-ray detector 3 of the first embodiment. In FIG. 8, the detection element rows 6a, 6
When b and 6c are illustrated in detail, it becomes rather difficult to see.
For reasons of space limitations, the detection element rows adjacent in the X direction are shown as detection element rows 6a, 6b, and 6c, respectively. However, actually, as shown in FIG. The detection element arrays are 6a, 6b, and 6c, respectively.

As in the first embodiment, the first and second detection data, that is, the transmission X-ray detection data (points a and b) shown in FIG. Steel wire data) are detected by the detection element rows 6a, 6b, 6c of the flat panel X-ray detector 6, respectively. The phantom F shown by a solid line in FIG. 9 shows a state at point a shown in FIG. 3, and the phantom F shown by a two-dot chain line in FIG. 9 shows a state at point b shown in FIG. In particular,
The arithmetic unit 53 calculates the average of the position coordinates of the two points (points a and b) detected by the detection elements Du of the detection element row 6a, and projects the rotation scanning center axis Z onto the flat panel X-ray detector 6
Is calculated (rotation center position Ca) of the detection element Du of the detection element row 6a. The calculation unit 53 calculates the remaining detection element row 6
The same calculation is performed for b and 6c.
The average of the position coordinates of the two points (points a and b) detected by the detection element Du of b is detected, and the detection elements of the detection element array 6b of the flat panel X-ray detector 6 on which the rotational scanning center axis Z is projected. The position of Du (rotation center position Cb) is calculated, the average of the position coordinates of the two points (points a and b) detected by the detection element Du of the detection element array 6c is taken, and the rotation scanning center axis Z is projected. The position (rotation center position Cc) of the detection element Du of the detection element array 6c of the flat panel X-ray detector 6 is calculated.

The calculating section 53 calculates the calculated rotation center position Ca.
The inclination K of the rotation scanning center axis Z shown in FIG. 9 is calculated based on Cc. The inclination K of the rotational scanning center axis Z calculated in this manner is used when performing image reconstruction processing on a plurality of transmission images (a group of transmission X-ray detection data) obtained by the above-described actual tomography. A tomographic image can be satisfactorily generated by being used for correcting the inclination.

In the above-described second embodiment, for example, three detection element arrays 6 corresponding to a predetermined number of detection pixel lines substantially parallel to the rotational scanning direction of the flat panel X-ray detector 6 are used.
For each of a, 6b, and 6c, the position of the detection element Du on which the rotation center axis (the rotation scanning center axis Z) is projected is calculated based on the first and second detection data, and the rotation is performed based on the calculated positions. Since the calculation unit 53 for calculating the inclination K of the central axis (the rotation scanning central axis Z) is provided, as shown in FIGS. Photographing is performed at the two angular positions θ1 and θ2, that is, only two times, that is, a certain angle and an angle rotated by 180 ° from the certain angle, and two pieces of transmission X-ray detection data are detected for each of the detection element arrays 6a, 6b, and 6c. The rotation center positions Ca to Cc in the flat panel X-ray detector 6 are collected based on the two transmission X-ray detection data, and the detection element rows 6a,
6b and 6c, and these rotation center positions Ca to C
The inclination of the rotation center (the inclination K of the rotation scanning center axis Z) in the flat panel X-ray detector 6 can be obtained from c, the time required for collecting transmitted X-ray detection data can be reduced, and two transmissions can be performed. Since only the X-ray detection data needs to be processed, only the data processing time can be shortened. Therefore, the inclination of the rotation center (the inclination K of the rotation scanning center axis Z) in the flat panel X-ray detector 6 can be quickly obtained. it can.

The present invention is not limited to the above embodiment, but can be modified as follows.

(1) In each of the above embodiments, the operation unit 53
The first detection data when the phantom F is at the first angular position θ1, and the second angular position at which the phantom F has an opposite phase to the first angular position θ1 as shown in FIGS. The position of the detection pixel in the detector on which the rotational scanning center axis Z is projected is calculated based on the second detection data in the state of θ2 (= θ1 + 180 °), that is, data of two points. A series of detection data (a plurality of detection data) obtained by photographing the phantom F in a state where F is within a predetermined angle range (within a small angle range) around the first angular position θ1 is averaged to obtain first detection data. Is calculated, and a series of detection data (a plurality of detection data) obtained by photographing the phantom F in a state where the phantom F is within a predetermined angle range (within a small angle range) around the second angular position θ2 is averaged. And the second detection data Calculated, the first and the calculated, based on the second detection data, rotational scanning center axis Z may be calculated the position of the detected pixel in the detector to be projected. In this case, transmission X-ray detection data is collected for two predetermined angle ranges (two small angle ranges), and the accuracy of the first and second detection data is improved by each average calculation. (Two small angle ranges)
The amount of transmission X-ray detection data collection and the amount of calculation of the transmission X-ray detection data for a plurality of transmission images (a group of transmission X-rays)
Line detection data), and the amount of data collection and calculation for a small angle is small compared to the conventional method of collecting and calculating line detection data. Calculation accuracy can be improved.

(2) In each of the above-described embodiments, the pre-shooting for obtaining the rotation center is performed before the actual tomography. However, after the actual tomography is performed, the rotation center is determined. May be performed in advance to obtain the value.

(3) In each of the embodiments described above, the flat panel X-ray detector 6 is employed as the planar detector.
I. Various two-dimensional planar detectors such as an I-tube and an imaging plate can be adopted.

(4) The tomographic imaging apparatus of each of the above-described embodiments
The subject can be used as a human body for medical use, or the subject can be used for various electronic components such as a BGA (Ball G1id A11ay) substrate and a printed wiring board for nondestructive inspection in the industrial field.

(5) In each of the above-described embodiments, the X-ray tube 1 irradiates the subject with X-rays. However, the present invention is not limited to X-rays. The same effect is obtained even when an electromagnetic wave such as that described above is used. Therefore, the tomography apparatus of the present invention is not limited to an X-ray tomography apparatus, but is also applicable to a tomography apparatus that performs tomography using electromagnetic waves that are transparent to a subject other than X-rays. It is possible.

[0056]

As is apparent from the above description, according to the tomography apparatus of the first aspect, the test object installed near the center of rotation on the installation table on which the object is installed is rotationally scanned. The first detection data obtained by photographing the device under test at the first angular position and the device photographed under the condition that the device under test is at the second angular position opposite to the first angle position A calculation unit for calculating the position of the detection pixel of the detector on which the rotation center axis is projected based on the second detection data obtained, so that the first and second angular positions at which the test object is in the opposite phase , That is, taking only two shots of a certain angle and an angle rotated by 180 ° from it,
One transmission X-ray detection data is collected, a rotation center of the detector can be obtained based on the two transmission X-ray detection data, and a time required for collecting the transmission X-ray detection data can be reduced. Data processing time can also be shortened because only arithmetic processing of transmitted X-ray detection data is required.

According to the tomography apparatus of the present invention, the detector is a linear detector in which a plurality of detection pixels are arranged one-dimensionally or a two-dimensional detector. Even when the planar detectors arranged in a matrix are used, the rotation center of the detector can be quickly obtained.

According to the tomography apparatus of the third aspect, the detector employs a planar detector in which a plurality of detection pixels are two-dimensionally arranged in a matrix.
For each predetermined number of detection pixel lines substantially parallel to the rotational scanning direction of the planar detector, the position of the detection pixel on which the rotation center axis is projected is calculated based on the first and second detection data. Since the inclination of the rotation center axis is calculated based on the position,
The inclination of the rotation center in the detector can be quickly obtained.

Further, according to the tomographic imaging apparatus of the fourth aspect, the calculation unit is configured to take a series of images of the test object in a state where the test object is within a predetermined angle range centered on the first angular position. The first detection data is calculated by averaging the detection data, and a series of detection data obtained by photographing the test object in a state where the test object is within a predetermined angle range centered on the second angular position is averaged. The second detection data is calculated, and the position of the detection pixel on which the rotation center axis is projected is calculated based on the calculated first and second detection data. The accuracy of the first and second detection data is improved by the collection and the average calculation, and
The collection of the transmitted X-ray detection data in each predetermined angle range and the amount of calculation thereof are smaller than the conventional method of collecting and calculating a plurality of transmission images (a group of transmitted X-ray detection data) for a half or entire circumference. Since the data collection amount and the calculation amount for the small angle are small, the calculation accuracy of the rotation center in the detector can be improved while keeping the data collection amount and the calculation amount small.

[Brief description of the drawings]

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

FIG. 2 is a diagram of a radiographic style according to the X-ray tomography apparatus of the first embodiment of the present invention.

FIG. 3 is a characteristic diagram showing sinogram characteristics detected by a detector by photographing a phantom on a turntable.

FIG. 4 is a block diagram of an X-ray tomography apparatus according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram of a flat panel X-ray detector.

FIG. 6 is a perspective view showing a schematic configuration of a flat panel X-ray detector.

FIGS. 7A and 7B are cross-sectional views illustrating a layer structure of a flat panel X-ray detector.

FIG. 8 is a block diagram of an X-ray tomography apparatus according to a second embodiment of the present invention.

FIG. 9 is a schematic diagram for explaining calculation of a tilt of a rotation center.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... X-ray tube 2 ... X-ray detection element 3 ... Row type X-ray detector 4 ... Turntable 6 ... Flat panel type X-ray detector 53 ... Operation part Du ... Detection element F ... Phantom Z ... Rotation scanning center axis

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G001 AA01 BA01 CA01 DA01 DA08 DA09 FA06 GA13 HA01 HA13 HA14 JA01 JA06 JA08 JA11 JA13 KA03 LA01 LA11 PA12 4C093 AA22 BA03 CA28 EB12 EB17 EB18 FD11

Claims (4)

[Claims] 1. An irradiation source for irradiating a subject with an electromagnetic wave having transparency to the subject, and (b) a plurality of irradiation sources arranged in parallel to the irradiation source with the subject interposed therebetween. And (c) an installation table for installing the object, and (d) the irradiation source and the detector and the installation table are relatively positioned. (E) a tomographic apparatus for rotationally scanning around a subject to perform tomography, wherein (e) the test object placed near the rotation center on the mounting table is at a first angular position in the rotational scanning. Rotation is performed based on first detection data obtained by photographing the body and second detection data obtained by photographing the body under test in a state where the test body is at a second angular position opposite to the first angular position. The function of calculating the position of the detection pixel of the detector onto which the central axis is projected A tomography apparatus comprising a calculation unit. 2. The tomography apparatus according to claim 1, wherein the detector is a linear detector in which a plurality of detection pixels are arranged one-dimensionally or a plurality of detection pixels are arranged two-dimensionally. A tomographic apparatus characterized in that it is a planar detector arranged in a matrix. 3. The tomography apparatus according to claim 1, wherein the detector is a planar detector in which a plurality of detection pixels are two-dimensionally arranged in a matrix, and the arithmetic unit includes the planar detector. For each of a predetermined number of detection pixel lines substantially parallel to the rotation scanning direction of the detector, the position of the detection pixel on which the rotation center axis is projected is calculated based on the first and second detection data, and based on the calculated positions. A tomographic apparatus for calculating a tilt of a rotation center axis by using the tomography apparatus. 4. The tomographic imaging apparatus according to claim 1, wherein the operation unit is configured to perform the operation in a state where the test object is within a predetermined angle range centered on the first angle position. By averaging a series of detection data obtained by photographing the test specimen,
Calculating the detection data, averaging a series of detection data obtained by photographing the test object in a state where the test object is within a predetermined angle range around the second angular position, and calculating the second detection data. A tomographic apparatus, wherein a position of a detection pixel on which a rotation center axis is projected is calculated based on the calculated first and second detection data.