JPH11290308A - Method for arraying radiation detecting element, radiation detecting equipment and radiation tomograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the influence of an X-ray beam irradiating position on a reference signal by arraying plural radiation detecting elements having a thin and long light receiving surface in the thickness direction of a radiation beam by means of permitting the longitudinal direction of the surface to meet the width direction of the radiation beam in the end part of a radiation detecting element array. SOLUTION: Multiple X-ray detecting elements 24(i) are arrayed in a detecting equipment array 24 and reference channels 14 are arranged in the both end parts. The basic configuration of a reference channel module is the same as that of a detecting equipment module and scintillators and photo-diodes respectively make a pair so as to constitute the X-ray detecting elements 24(i) having the thin and long light receiving surface. A different point is that the elements 24(i) are arrayed mutually in parallel in the X-ray beam thickness direction by permitting the longitudinal direction of the surface to meet with the X-ray beam width direction. The plural elements are adjacently arrayed in the thickness direction at the both ends of the array 240 of the detecting equipment module.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for arranging radiation detecting elements, a radiation detector and a radiation tomography apparatus, and more particularly to a radiation detector irradiated with a radiation beam having a width and a thickness, and such a radiation detector. And a radiation tomography apparatus having such a radiation detector.

[0002]

2. Description of the Related Art As an example of a radiation tomography apparatus, there is, for example, an X-ray computed tomography (CT) apparatus. In an X-ray CT apparatus, X-rays are used as radiation. An X-ray tube is used for X-ray generation. Then, the radiation irradiation / detection device, that is, the X-ray irradiation / detection device is rotated (scanned) around the subject, and the subject is exposed to X-rays in a plurality of views around the subject. Is measured, and a tomographic image is generated (reconstructed) based on the projection data.

An X-ray irradiator has an X-ray beam (b) having a width encompassing an imaging range and having a predetermined thickness in a direction perpendicular thereto.
eam). The X-ray detection device detects X-rays by a multi-channel X-ray detector in which a large number of X-ray detection elements are arranged in an array in the direction of the width of the X-ray beam. The multi-channel X-ray detector has a length (width) corresponding to the width of the X-ray beam in the direction of the width of the X-ray beam. The X-ray detection element in the multi-channel X-ray detector has a length (thickness) greater than the thickness of the X-ray beam in the direction of the thickness of the X-ray beam.

Some X-ray detection elements at both ends of the X-ray detector are arranged so as to be out of the range where the subject is projected, so that the X-ray beam is directly irradiated. These X-ray detecting elements are used as reference channels.
channel). The detection signal of the reference channel is used for correcting measurement data as a reference signal indicating the intensity of the X-ray beam.

[0005] Solid state typ
The X-ray detecting element e) is composed of, for example, a scintillator that emits light upon irradiation with X-rays and a photodiode L (photodiode) that converts the light into an electric signal. The X-ray beam passes through a collimator
The X-ray detecting element is irradiated to the central part in the thickness direction. The thickness of the X-ray beam is determined by the X-ray aperture (aperturing) of the collimator according to the slice thickness of the imaging.
e)).

[0006]

In an X-ray detecting element comprising a combination of a scintillator and a photodiode, the sensitivity distribution in the thickness direction is generally not uniform.
The detection signal changes according to the X-ray irradiation position in the thickness direction. Therefore, the detection signal of the reference channel also changes according to the X-ray irradiation position in the thickness direction.

In the X-ray tube, the focal point of the X-ray moves due to thermal expansion or the like due to a rise in temperature during use, and this appears as a change in the irradiation position in the thickness direction of the X-ray detector through the aperture of the collimator. There was a problem of changing the reference signal.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a method of arranging a radiation detecting element in which a reference signal is not affected by an irradiation position of an X-ray beam, a radiation detector, and a method of radiating a radiation. It is an object of the present invention to realize a radiation tomography apparatus having a simple radiation detector.

[0009]

Means for Solving the Problems (1) According to a first aspect of the present invention, one of two directions perpendicular to an irradiation direction and perpendicular to each other has a relatively large width in one of the two directions. A method of arranging radiation detection elements in a radiation detection element array irradiated with a radiation beam having a relatively small thickness, wherein the radiation detection element having an elongate radiation receiving surface is disposed in the longitudinal direction of the radiation receiving surface. A radiation detecting element array is formed by arranging a plurality of radiation detecting elements in the width direction of the radiation beam in accordance with the thickness direction of the radiation detecting element array. At least one end of the radiation detecting element array has a radiation detecting element having an elongated radiation receiving surface. A radiation detecting element arranging method, wherein a plurality of longitudinal directions are aligned in a thickness direction of the radiation beam so as to match a width direction of the radiation beam. That.

(2) A second aspect of the present invention for solving the above-mentioned problem is that one of two directions perpendicular to the irradiation direction and perpendicular to each other has a relatively large dimension width and the other has a relatively small dimension width. A radiation detector irradiated with a radiation beam having a thickness, wherein a plurality of radiation detection elements having an elongated radiation receiving surface are arranged in the width direction of the radiation beam such that the longitudinal direction of the light receiving surface is aligned with the thickness direction of the radiation beam. A first radiation detection element array having a plurality of radiation detection elements, and a radiation detection element provided on at least one end of the radiation detection element array and having an elongated radiation receiving surface. A second radiation detecting element array, which is arranged in a plurality in the thickness direction of the radiation beam in accordance with the above.

(3) A third aspect of the present invention for solving the above-mentioned problem is that two directions perpendicular to the irradiation direction and perpendicular to each other have a relatively large width in one direction and a relatively small width in the other direction. A radiation irradiating unit that irradiates a radiation beam having a thickness, a radiation detector to which the radiation beam is irradiated, and a tomographic image of a passage area of the radiation beam based on radiation detection signals of a plurality of views by the radiation detector. A radiation tomography apparatus having a radiation tomographic image generating means for generating a tomographic image, wherein the radiation detector adjusts a longitudinal direction of the radiation detecting element having an elongated radiation receiving surface to a thickness direction of the radiation beam. A first radiation detection element array arranged in a plurality in the width direction of the radiation beam, and a thin radiation detection element array provided on at least one end side of the radiation detection element array; A second radiation detection element array in which a plurality of radiation detection elements having a radiation reception surface are arranged in the thickness direction of the radiation beam such that the longitudinal direction of the light reception surface is aligned with the width direction of the radiation beam. It is a radiation tomography apparatus characterized by performing.

In the second invention or the third invention, it is preferable that the second radiation detector array is provided at both ends of the first radiation detector array from the viewpoint of appropriately obtaining a reference signal.

(Operation) In the present invention, the radiation detecting element for the reference channel provided in the radiation detecting element array is arranged such that the longitudinal direction of the light receiving surface thereof is in the width direction of the radiation beam, and the thickness direction of the X-ray beam is changed. The reference signal is not changed by the displacement.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the X-ray CT apparatus. This device is an example of an embodiment of the present invention. The configuration of the present apparatus shows an example of an embodiment relating to the apparatus of the present invention. An example of an embodiment of the method of the present invention is shown by the operation of the present apparatus.

As shown in FIG. 1, the apparatus comprises a scanning gantry 2, a photographing table 4, and an operation console (c).
onsole) 6. The scanning gantry 2 has an X-ray tube 20 as a radiation source. An X-ray (not shown) emitted from the X-ray tube 20 is shaped by the collimator 22 into, for example, a fan-shaped X-ray beam, and the detector array 24
Is to be irradiated. The X-ray tube 20 and the collimator 22 are an example of an embodiment of a radiation irradiation unit in the present invention.

The detector array 24 is an example of an embodiment of the radiation detector according to the present invention. It is also an example of an embodiment of the radiation detecting element array according to the present invention.
The detector array 24 has a plurality of X-ray detection elements arranged in an array in the direction of the width of the fan-shaped X-ray beam. The configuration of the detector array 24 will be described later.

The X-ray tube 20, collimator 22 and detector array 24 constitute an X-ray irradiation / detection device. The configuration of the X-ray irradiation / detection device will be described later. A data collection unit 26 is connected to the detector array 24. The data collection unit 26 collects detection data of individual X-ray detection elements of the detector array 24.

The irradiation of X-rays from the X-ray tube 20 is controlled by an X-ray controller 28. The illustration of the connection relationship between the X-ray tube 20 and the X-ray controller 28 is omitted. Collimator 22
Are controlled by the collimator controller 30. The illustration of the connection relationship between the collimator 22 and the collimator controller 30 is omitted.

The above-described X-ray tube 20 to collimator controller 30 are mounted on the rotating unit 32 of the scanning gantry 2. The rotation of the rotation unit 32 is controlled by a rotation controller 34. The illustration of the connection relationship between the rotation unit 32 and the rotation controller 34 is omitted.

The imaging table 4 carries a subject (not shown) into and out of the X-ray irradiation space of the scanning gantry 2. The relationship between the subject and the X-ray irradiation space will be described later.

The operation console 6 has a central processing unit 60. The central processing unit 60 is an example of an embodiment of a tomographic image generation unit according to the present invention. Central processing unit 6
0 is composed of, for example, a computer. The central processing unit 60 has a control interface (int
erface) 62 is connected. Control interface 6
2, a scanning gantry 2 and an imaging table 4 are connected.

The central processing unit 60 has a control interface 6
2, the scanning gantry 2 and the imaging table 4 are controlled. The data acquisition unit 26, X-ray controller 28, collimator controller 30, and rotation controller 34 in the scanning gantry 2 are controlled through a control interface 62. It should be noted that illustration of individual connections between these units and the control interface 62 is omitted.

A data acquisition buffer 64 is also connected to the central processing unit 60. Data collection buffer 6
4 is connected to the data collection unit 26 of the scanning gantry 2. The data collected by the data collection unit 26 is input to the data collection buffer 64. Data collection buffer 6
4 temporarily stores the input data. Central processing unit 6
The storage device 66 is also connected to 0. The storage device 66 stores various data, reconstructed images, and programs.
(program) and so on.

The central processing unit 60 also includes a display device 6
8 and the operating device 70 are connected to each other. The display device 68 displays a reconstructed image and other information output from the central processing unit 60. Operation device 7
Numeral 0 is operated by the operator to input various instructions and information to the central processing unit 60.

FIG. 2 shows a schematic configuration of the detector array 24. The detector array 24 has a large number (for example, 1000)
X-ray detectors 24 (i) are arranged in an arc to form a multi-channel X-ray detector. i is a channel number, for example, i = 1 to 1000. X-ray detector 2
FIG. 4 (i) is an example of an embodiment of the radiation detecting element in the present invention. At both ends of the detector array 24, a plurality of X-ray detecting elements for reference, that is, reference channels 14 are provided. The detailed configuration of the reference channel 14 will be described later.

FIG. 3 shows the relationship among the X-ray tube 20, the collimator 22, and the detector array 24 in the X-ray irradiation / detection device. 3A is a front view, and FIG. 3B is a side view. As shown in the figure, the X-rays radiated from the X-ray tube 20 are shaped into a fan-shaped X-ray beam 40 by a collimator 22 and irradiated to a detector array 24. FIG. 3A shows the spread of the fan-shaped X-ray beam 40, that is, the width of the X-ray beam 40. FIG. 3B shows the thickness of the X-ray beam 40.

The fan axis of the X-ray beam 40 is crossed with the body axis, and for example, as shown in FIG.
Is placed in the X-ray irradiation space. X
A projection image of the subject 8 sliced by the line beam 40 is projected on the detector array 24. The thickness of the X-ray beam 40 at the isocenter of the subject 8 gives the slice thickness th of the subject 8. The slice thickness th is
It is determined by the aperture of the collimator 22.

X-ray beam 40 for detector array 24
FIG. 5 shows a more detailed schematic diagram of the irradiation state of FIG. As shown in FIG.
By displacing 0, 222 in the direction to narrow the aperture, the slice thickness th of the projected image on the detector array 24 can be reduced. Also, the collimator piece 22
0, 222 in the direction to widen the aperture, the slice thickness th of the projected image on the detector array 24 is increased.
Can be made thicker. With such an aperture adjustment, the slice thickness is set to, for example, 1, 2, 3, 5, 7, 10 m.
It is set to a predetermined thickness such as m. The length (thickness) of the detector array 24 in the slice thickness direction is, for example, about 30 mm.

FIGS. 6, 7 and 8 show detector array 2
4 shows a schematic configuration of a detector module (module) 240 constituting the fourth embodiment. FIG. 6 is a plan view, FIG.
Is an exploded view. As shown in these figures, the detector module 240 has a plurality of scintillators 242 to 248 arranged in parallel with each other. Scintillator 242-
248 each have an elongated rectangular X-ray receiving surface,
They are arranged parallel to each other in the direction of the short side of the light receiving surface. The scintillators 242 to 248 are integrated by a bonding material 250. Although the ratio of the long side to the short side of the light receiving surface is actually about 30: 1, the ratio is drawn lower than the actual one for easy understanding.

The detector module 240 also has a plurality of photodiodes 272 to 278 formed on the semiconductor substrate 270 in parallel with each other. Semiconductor substrate 270
Is mounted on a base 290 by, for example, bonding.

Each of the photodiodes 272 to 278 also has an elongated rectangular light receiving surface. The arrangement of the photodiodes 272 to 278 corresponds to the scintillators 242 to 248.
Corresponding to the array. The lower surfaces (light emitting surfaces) of the scintillators 242 to 248 shown in FIG. 8B are superimposed on the upper surfaces (light receiving surfaces) of the photodiodes 272 to 278 shown in FIG. Have been.
The adhesive 350 is an optical adhesive.

The X-ray beam enters the scintillators 242 to 248 from above in FIG. The fan-shaped surface of the X-ray beam is parallel to the plane of FIG. Scintillators 242-2
48 emits light in accordance with the intensity of the incident X-ray. Light emitted from the scintillators 242 to 248 is detected by the photodiodes 272 to 278, respectively.

Scintillator 242 and photodiode 2
72 pairs, scintillator 244 and photodiode 27
Four pairs, scintillator 246 and photodiode 276
Pair and scintillator 248 and photodiode 27
8 correspond to the X-ray detecting elements 24 shown in FIG.
Form (i).

A plurality of such detector modules 240 are arranged adjacent to each other so that the short side of the light receiving surface of each X-ray detecting element is aligned with the direction of the width of the X-ray beam 40, and the detection module shown in FIG. Of the device array 24 except for the reference channel 14. Detector module 240
The array portion constituted by the above arrangement is an example of an embodiment of the first radiation detector array in the present invention. The base 290 is fixed to a predetermined support frame (not shown) or the like by appropriate means.

FIGS. 9 and 10 show a reference channel module 140 for the reference channel 14.
1 shows a schematic configuration of FIG. FIG. 9 is a plan view, and FIG. 10 is a BB cross-sectional view. Reference channel module 140
Is basically the same as the detector module 240, the scintillators 142 to 148 and the photodiode 1
72 to 178 form a pair and constitute an X-ray detecting element having an elongated light receiving surface. Although the ratio of the long side to the short side of the light receiving surface is actually about 30: 1, the ratio is drawn lower than the actual one for easy understanding.

The difference from the detector module 240 is that the X-ray detecting elements are arranged parallel to each other in the thickness direction of the X-ray beam, with the longitudinal direction of the light receiving surface being adjusted to the width direction of the X-ray beam. is there. A plurality of such reference channel modules 140 are disposed adjacent to each other at both ends of the array of the detector modules 240 in the thickness direction of the X-ray beam, and constitute the reference channels 14 in the detector array 24 shown in FIG. doing. The reference channel 14 is an example of an embodiment of the second radiation detector array in the present invention.

As a result, the reference channel module 140 is irradiated with the X-ray beam from the top in FIG. 10 with the fan-shaped surface parallel to the paper. For this reason,
The X-ray beam is applied to the light receiving surface of the reference channel X-ray detecting element composed of a pair of a scintillator and a photodiode over the entire length in the longitudinal direction. Therefore, even if the reference channel is such that the sensitivity greatly changes in the longitudinal direction of the light receiving surface as shown in FIG. 11, for example, the X detection signal, that is, the reference signal is not affected.

Further, even if the irradiation position of the X-ray beam moves in the thickness direction due to the movement of the X-ray focal point or the like, the relationship in which the X-ray beam is irradiated over the entire length of the light receiving surface of the X-ray detecting element for the reference channel changes. Absent. Therefore, it is possible to obtain a reference signal that is not affected by a change in the irradiation position in the thickness direction.

FIG. 12 shows the configuration of an electric circuit for X-ray detection for one channel of the detector array 24.
As shown in the figure, an equivalent circuit of the photodiode 24k is represented by a parallel circuit of a diode 90, a capacitor 92, a resistor 94 and a DC constant current source 96.

A connector (connect) is connected to such a parallel circuit.
or) The integration circuit 100 is connected via 98. The integration circuit 100 exists in the data collection unit 26. The integration circuit 100 includes an operational amplifier (OP amplifier) 10
2, the positive input terminal is connected to common, the negative input terminal is connected to a resistor 104, the negative input terminal is connected to the output terminal via a capacitor 106, and a switch 108 is connected to the capacitor 106 in parallel. Connected and configured.

In such a circuit, the DC constant current source 9
The current 6 changes in proportion to the intensity of the X-ray incident on the scintillator, and as a result, the input current of the integrating circuit 100 changes. Such an input current is integrated and output as an X-ray detection signal. A similar X is used for all channels and reference channels of the detector array 24.
Line detection circuits are configured to obtain X-ray detection signals.

The operation of the present apparatus will be described. The imaging of the subject 8 is performed under the control of the central processing unit 60 based on a command from the operator given through the operation device 70. That is, the X-ray irradiation / detection device including the X-ray tube 20, the collimator 22, and the detector array 24 rotates (scans) around the body axis of the subject 8 while maintaining their mutual relationship, and performs one of the scans. A plurality (for example, 100
The projection data of the subject is collected at the view angle of 0). The collection of the projection data is performed by the detector array 24 and the data collection unit 2.
6- Performed by the system of the data collection buffer 64.

Based on the projection data collected in the data collection buffer 64, the central processing unit 60 generates a tomographic image, that is, performs image reconstruction. At this time, before image reconstruction, X-ray intensity correction is performed on the projection data using a reference signal measured through the reference channel 14. Since the reference signal is not affected by the change in the irradiation position in the thickness direction of the X-ray beam as described above,
X-ray intensity correction can be appropriately performed irrespective of the movement of the focal point of the line beam.

At this time, the X-ray beam irradiation position in the thickness direction can be detected by identifying the X-ray detecting element of the reference channel 14 receiving the X-ray beam. Therefore, based on the detection signal,
It is also possible to adjust the X-ray irradiation position using a collimator or the like.

Image reconstruction is performed, for example, by using projection data of, for example, 1000 views obtained by one rotation scan, for example, by using filtered back-projection (filtered back-projection).
ction) method. The reconstructed image is stored in the storage device 66 and the display device 68
Is displayed as a visible image.

In the above, an example in which X-rays are used as radiation has been described. However, the radiation is not limited to X-rays, but may be other types of radiation such as γ-rays. However,
At present, X-rays are preferred because practical means for generating, detecting, controlling, and the like are the most substantial. Also,
The radiation detecting element is not limited to the one using the scintillator, but may be another type of radiation detecting element using cadmium tellurium (Cd.Te) or the like.

[0047]

As described above in detail, according to the present invention, there is provided a radiation detecting element arrangement method, a radiation detector, and a radiation detector in which a reference signal is not affected by an irradiation position of an X-ray beam. Radiation tomography apparatus provided with the apparatus.

[Brief description of the drawings]

FIG. 1 is a block diagram of a device according to an example of an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a detector array in an apparatus according to an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of an X-ray irradiation / detection device in an example of an embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an X-ray irradiation / detection device in an example of an embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of an X-ray irradiation / detection apparatus in the apparatus according to an embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of a detector module in an apparatus according to an example of an embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a detector module in an apparatus according to an embodiment of the present invention.

FIG. 8 is a schematic configuration diagram of a detector module in an apparatus according to an embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of a reference channel module in an apparatus according to an embodiment of the present invention.

FIG. 10 is a schematic configuration diagram of a reference channel module in an apparatus according to an embodiment of the present invention.

FIG. 11 shows X in the apparatus according to the embodiment of the present invention.
It is a graph which shows an example of the sensitivity profile of a line detection element.

FIG. 12 shows X in the apparatus according to an embodiment of the present invention;
It is an electrical connection diagram of a line detection device.

[Explanation of symbols]

 2 Scanning gantry 20 X-ray tube 22 Collimator 24 Detector array 24 (i) X-ray detecting element 26 Data collection unit 28 X-ray controller 30 Collimator controller 32 Rotating unit 34 Rotation controller 4 Imaging table 6 Operation console 60 Central processing unit 62 Control Interface 64 Data acquisition buffer 14 Reference channel 40 X-ray beam 8 Subject 220, 222 Collimator piece 240 Detector module 242 to 248 Scintillator 272 to 278 Photodiode 140 Reference channel module 142 to 148 Scintillator 172 to 178 Photodiode

Claims (3)

[Claims] 1. A radiation detecting element array which is irradiated with a radiation beam having a relatively large dimension width in one direction and a relatively small dimension thickness in the other direction perpendicular to the irradiation direction and perpendicular to each other. The method of arranging radiation detection elements according to the above, wherein a plurality of radiation detection elements having an elongated radiation receiving surface are arranged in the width direction of the radiation beam such that the longitudinal direction of the light receiving surface is aligned with the thickness direction of the radiation beam. A radiation detecting element array having at least one end portion of the radiation detecting element array, the radiation detecting element having an elongated radiation receiving surface, the longitudinal direction of the light receiving surface being adjusted to the width direction of the radiation beam, and the thickness direction of the radiation beam being A radiation detecting element arranging method. 2. A radiation detector which is irradiated with a radiation beam having a relatively large dimension width in one of two directions perpendicular to the irradiation direction and perpendicular to each other and a relatively small dimension thickness in the other direction. A first radiation detecting element array in which a plurality of radiation detecting elements having an elongated radiation receiving surface are arranged in the width direction of the radiation beam so that the longitudinal direction of the light receiving surface is aligned with the thickness direction of the radiation beam; A plurality of radiation detection elements provided on at least one end of the radiation detection element array and having an elongated radiation receiving surface are arranged in the thickness direction of the radiation beam such that the longitudinal direction of the light receiving surface is aligned with the width direction of the radiation beam. Second
A radiation detection element array. 3. A radiation irradiating means for irradiating a radiation beam having a relatively large dimension width in one of two directions perpendicular to each other and perpendicular to the irradiation direction, and a relatively small dimension thickness in the other direction. Radiation tomography, comprising: a radiation detector to which the radiation beam is applied; and a tomographic image generation unit configured to generate a tomographic image of a passage area of the radiation beam based on radiation detection signals of a plurality of views by the radiation detector. The radiation detector, wherein a plurality of radiation detecting elements having an elongated radiation receiving surface are arranged in a width direction of the radiation beam such that a longitudinal direction of the radiation receiving surface is aligned with a thickness direction of the radiation beam. A first radiation detection element array, a radiation detection element provided on at least one end of the radiation detection element array and having an elongated radiation receiving surface The second formed by arranging a plurality in the thickness direction of the radiation beam and the combined longitudinal direction of the light receiving surface in the width direction of the radiation beam
A radiation detection element array.