JP2005249658A - Light or radiation detector, and light or radiation detection control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light or radiation detector and a light or radiation detection control system capable of reducing a noise. <P>SOLUTION: This light or radiation detector unit /light or radiation detection control system is provided with a magnetic shield 50 formed of a magnetic permeable substance represented by a permalloy or the like, the magnetic shield 50 is constituted into a casing-like shape to make the detector unit 10 not affected by magnetism, and a radiation detector 30 is stored in a casing to constitute the radiation detector unit 10. A magnetic noise MN, i.e., a magnetic force line is shielded thereby along the magnetic shield 50 not to affect the detector unit 10. Resultingly, the magnetic noise is removed and the noise therein is reduced to reduce the noise. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radiation detection apparatus and a light or radiation detection control system used in the medical field, the industrial field, and the nuclear field.

An X-ray detection apparatus will be described as an example. The X-ray detection apparatus includes an X-ray sensitive X-ray conversion layer (semiconductor layer). The X-ray conversion layer is converted into charge information by the incidence of X-rays, and the converted charge information is read out to read X Detect lines. The charge converted from X-rays by the X-ray conversion layer is very small, and it is necessary to amplify the charge. In that case, since noise is amplified, it is necessary to reduce the noise in order to obtain an image with a good S / N (signal to noise) ratio. Therefore, in order to reduce noise, conductive fibers obtained by combining polyamide and silver having a high shielding effect are used in the detection device (see, for example, Patent Document 1).
JP 2000-116633 A (page 3, FIGS. 2, 4)

  However, it has been found that noise cannot be removed even with a conductive material typified by such conductive fibers.

  This invention is made | formed in view of such a situation, Comprising: It aims at providing the light or radiation detection apparatus and light or radiation detection control system which can reduce noise.

  As a result of earnest research to solve the above problems, the inventors have obtained the following knowledge.

  That is, attention was paid to an MRI (Magnetic Resonance Imaging) apparatus. In the MRI apparatus, computers that control the MRI apparatus are electrically connected to the MRI apparatus by connection means such as a cable. One system is constructed by the MRI apparatus and the computer. A CRT (Cathode Ray Tube) monitor or the like on the computer side is specially provided with a magnetic shield so as not to be affected by magnetism from the MRI apparatus. By applying a magnetic shield to the CRT monitor or the like, the MRI apparatus is not affected by the magnetism from the CRT monitor or the like. That is, by providing a magnetic shield at least anywhere between the MRI apparatus, the computer, and the MRI apparatus / computer, they are not affected by the magnetism from the MRI apparatus / computer.

  Even in the case of a light or radiation detection apparatus typified by an X-ray detection apparatus or the like, a computer is electrically connected in the same manner as an MRI apparatus, and this light or radiation detection apparatus and the computer constitute one system. ing. A computer is disposed in the vicinity of the detection device. Therefore, the inventors assume that the influence of magnetism from the computer side (for example, a CRT monitor) is exerting on the detection device as well as the MRI apparatus, and that this magnetic noise cannot be removed. did.

  In Patent Document 1 described above, conductive fibers are useful for shielding electromagnetic waves, but in reality, only electrical noise can be removed by conductive materials such as conductive fibers. There was found. That is, as shown in FIG. 6A, even if the conductive material 101 is grounded, the electrical noise EN escapes to the ground plane through the conductive material 101, but as shown in FIG. 6B. The magnetic noise MN, that is, the lines of magnetic force, are considered to pass through the conductive material and enter the detection device side. Based on the above, the knowledge that magnetic noise can be removed if a magnetic shield is placed anywhere between a detection device, a control device typified by a computer, and the detection device / control device. Obtained.

  The present invention based on such knowledge has the following configuration.

  That is, the invention according to claim 1 includes a semiconductor layer that converts light or radiation information into charge information upon incidence of light or radiation, and detects light or radiation by reading the converted charge information. Or it is a radiation detection apparatus, Comprising: The magnetic shield formed with the magnetic permeability substance is provided, The said magnetic shield is arrange | positioned in the location where the said detection apparatus does not receive the influence of magnetism.

  [Operation / Effect] According to the invention described in claim 1, the magnetic shield is formed of a magnetically permeable material, and the magnetic shield is disposed at a location where the detection device is not affected by magnetism. Magnetic noise, ie magnetic field lines, are blocked along the magnetic shield and do not reach the detection device. As a result, magnetic noise can be removed, and noise can be reduced by removing the noise.

  In the above-described invention, it is preferable that a radiation detector including a semiconductor layer and a readout substrate for reading out the charge information is accommodated in a casing, and the casing is formed of the above-described magnetically permeable material. invention). Magnetic field lines (magnetic noise) MN wrap around as shown in FIG. 7, for example. Therefore, when the wall of the magnetic shield S shown in FIG. 7 is provided, the magnetic field lines MN are formed below the upper part of the wall or when not installed on the floor. The noise caused by the sneaking around reaches the detection device. Of course, as shown in FIG. 5, the magnetic shield may be arranged with the height of the wall of the magnetic shield S so that noise due to the wraparound of the magnetic field lines MN can be ignored. In some cases, the casing is formed of a magnetically permeable material, and the casing does not allow the magnetic lines of force to enter the casing. Therefore, the magnetic shield can be easily realized in the casing without allowing magnetic field lines to wrap around the detector accommodated in the casing, that is, magnetic noise.

  In the above-described invention, it is preferable that the magnetically permeable material has conductivity, and the permeable magnetic material having conductivity is grounded (the invention according to claim 3). With this configuration, electrical noise escapes through the grounded magnetically permeable material. As a result, not only magnetic noise but also electrical noise can be removed, and noise can be further reduced by removing these noises.

  The invention described above includes a phosphor (scintillator) that converts radiation information into light, and a light-sensitive semiconductor layer that converts radiation information into charge information indirectly, that is, converts the converted light into charge information. The present invention can also be applied to the indirect conversion type radiation detection apparatus provided and the direct conversion type radiation detection apparatus including a radiation sensitive semiconductor layer that directly converts radiation information into charge information. Invention described in 1.). Of course, the present invention can also be applied to a photodetection device.

  According to a fifth aspect of the present invention, there is provided a semiconductor layer for converting the light or radiation information into charge information by the incidence of light or radiation, and light or radiation is detected by reading the converted charge information. Or a light or radiation detection control system constructed by a radiation detection device and a control device for controlling the detection device, comprising a magnetic shield formed of a magnetically permeable material, at least the detection device, the control device, The magnetic shield is disposed at any location between the detection device and the control device.

  [Operation / Effect] According to the invention described in claim 5, the magnetic shield is formed of a magnetically permeable material, and the magnetic shield is provided at least at any location between the detection device, the control device, and the detection device / control device. By disposing the magnetic noise, that is, the magnetic lines of force are blocked along the magnetic shield, the magnetic noise does not reach both the detection device and the control device. As a result, magnetic noise can be removed, and noise can be reduced by removing the noise.

  One example of the above-described invention is that a magnetic shield is provided at least on the detection device side (the invention according to claim 6), similarly to the invention (light or radiation detection device) described in claim 1. .

  According to the light or radiation detection device according to the present invention (the invention according to claim 1), the magnetic shield is provided at a location that is provided with a magnetic shield formed of a magnetically permeable material and is not affected by the magnetic device. The magnetic noise, that is, the lines of magnetic force are blocked along the magnetic shield and do not reach the detection device. On the other hand, according to the light or radiation detection control system according to the present invention (the invention according to claim 5), the magnetic shield is disposed at least anywhere between the detection device, the control device, and the detection device / control device. As a result, magnetic noise, that is, lines of magnetic force are blocked along the magnetic shield, and magnetic noise does not reach both the detection device and the control device. As a result, magnetic noise can be removed, and noise can be reduced by removing the noise.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 is a schematic diagram of a radiation detection control system having a radiation detection apparatus according to an embodiment, FIG. 2 is a schematic cross-sectional view of the radiation detection apparatus, and FIG. 3 is an equivalent circuit of FIG. FIG. 4 is a circuit diagram showing a plan view. In the present embodiment, a direct conversion type radiation detector will be described as an example.

  As shown in FIG. 1, the radiation detection control system according to this embodiment includes a radiation detection apparatus 10 and a computer 20. As illustrated in FIGS. 2 and 3, the radiation detection apparatus 10 includes a radiation detector 30 and a housing-like magnetic shield 50 that houses the radiation detector 30. The computer 20 includes a pointing device (input means) 21 typified by a mouse, keyboard, joystick, trackball, touch panel, etc., a storage medium typified by ROM (Read-only Memory), RAM (Random-Access Memory), etc. And a main body 22 that houses a central processing unit (CPU), a CRT (Cathode Ray Tube) monitor (display means) 23, and the like. The radiation detection apparatus 10 and the computer 20 are electrically connected to each other by connection means such as a cable, and the computer 20 controls the radiation detection apparatus 10 via the cable. The computer 20 corresponds to the control device in the present invention.

  As shown in FIGS. 2 and 3, the radiation detector 30 is provided on a surface of the semiconductor thick film 31 and a radiation sensitive semiconductor thick film 31 in which carriers are generated when radiation such as X-rays enters, for example. The applied voltage application electrode 32, the carrier collection electrode 33 provided on the back surface opposite to the radiation incident side of the semiconductor thick film 31, and the charge storage capacitor Ca for collecting collected carriers to the carrier collection electrode 33. , And a thin film transistor (TFT) Tr that is a switching element for taking off charges that are normally OFF (blocked) for taking out the charges accumulated in the capacitor Ca. In the present embodiment, the semiconductor thick film 31 is formed of a radiation sensitive material that generates carriers by the incidence of radiation, but may be a photosensitive material that generates carriers by the incidence of light. . The semiconductor thick film 31 corresponds to the semiconductor layer in this invention.

  In addition, the radiation detector 30 includes a data line 34 connected to the source of the thin film transistor Tr, and a gate line 35 connected to the gate of the thin film transistor Tr. 31, a carrier collecting electrode 33, a capacitor Ca, a thin film transistor Tr, a data line 34, and a gate line 35 are stacked on an insulating substrate 36.

  2 to 4, for each of the carrier collection electrodes 33 formed in a large number (for example, 1024 × 1024) in a vertical / horizontal two-dimensional matrix arrangement, each of the capacitors Ca and the thin film transistors Tr described above is provided. Are connected to each other, and the carrier collecting electrode 33, the capacitor Ca, and the thin film transistor Tr are separately formed as each detecting element DU. Further, the voltage application electrode 32 is formed over the entire surface as a common electrode of all the detection elements DU. Further, as shown in FIG. 4, the data lines 34 described above are arranged in parallel in the horizontal (X) direction, and the gate lines 35 described above are arranged in the vertical (Y) direction as shown in FIG. The data lines 34 and the gate lines 35 are connected to the detection elements DU. The data line 34 is connected to a multiplexer 38 via a charge-voltage conversion group 37, and the gate line 35 is connected to a gate driver 39. Note that the number of detection elements DU arranged is not limited to the above-mentioned 1024 × 1024, but can be used by changing the number of arrangement according to the embodiment. Therefore, the form with only one detection element DU may be sufficient.

  The detection elements DU are patterned on the insulating substrate 36 in a two-dimensional matrix arrangement, and the insulating substrate 36 on which the detection elements DU are patterned is also called an “active matrix substrate”. The insulating substrate 36 on which the detection element DU is patterned corresponds to the readout substrate in the present invention.

  The charge-voltage conversion group 37 and the multiplexer 38 constitute the amplifier circuit 40 shown in FIG. 2, and this amplifier circuit 40 is mounted on a flexible substrate 41 formed of an elastic body. The flexible substrate 41 is electrically connected to a data line 34 formed on the insulating substrate 36 and a signal processing substrate 42 (see FIGS. 2 and 4) disposed on the opposite side of the insulating substrate 34 from the radiation incident side. It is connected. The signal processing board 42 is electrically connected to the computer 20 via a cable (see FIG. 1). The gate driver 39 is also mounted on a flexible substrate (not shown).

  When the radiation detector 30 formed of the semiconductor thick film 31, the insulating substrate 36, or the like is formed, the surface of the insulating substrate 36 is used by using a thin film forming technique by various vacuum deposition methods or a pattern technique by photolithography. The data line 34 and the gate line 35 are wired, and the thin film transistor Tr, the capacitor Ca, the carrier collection electrode 33, the semiconductor thick film 31, the voltage application electrode 32, and the like are sequentially stacked. The semiconductor for forming the semiconductor thick film 31 can be appropriately selected according to the application, withstand voltage, etc., as exemplified by an amorphous semiconductor and a polycrystalline semiconductor. Further, the material forming the semiconductor thick film 31 is not particularly limited as exemplified by selenium (Se). In the present embodiment, since it is a direct conversion type radiation detector, the semiconductor thick film 31 is formed of amorphous selenium.

  On the magnetic shield 50 containing the radiation detector 30 formed of the semiconductor thick film 31 and the insulating substrate 36, a shielding plate 51 that shields radiation and light other than radiation to be detected (here, X-rays). It is arranged. The shielding plate 51 is made of a material having a low shielding rate such as carbon or resin so as to minimize the attenuation of X-rays by the shielding plate 51.

Magnetic lines of force are generated from the CRT monitor 23 (see FIG. 1) in the computer 20 (see FIG. 1). The magnetic noise MN shown in FIG. 2 is mostly due to the lines of magnetic force from the CRT monitor 23. Therefore, the magnetic shield 50 is formed of a magnetically permeable material typified by an iron-nickel (Fe—Ni) alloy, which is a ferromagnetic material, that is thermally fired (annealed) to about 1000 ° C. (hereinafter referred to as “permalloy”). Has been. By forming the magnetic shield 50 with permalloy, the magnetic noise MN is blocked along the magnetic shield 50 and does not reach the detection device 10 as shown in FIG. Permalloy also has conductivity, and in this embodiment, this permalloy is grounded. The relative permeability of permalloy depends on the magnetic flux density and the like, but is about 10 ⁴ to several 10 ⁶ .

  Since X-rays may be attenuated by permalloy, it is preferable to make the thickness of the incident surface of the housing of the magnetic shield 50 thinner than the other surfaces. In this embodiment, a permalloy having a thickness of about 0.1 μm is formed on the incident surface, and a permalloy having a thickness of about 0.3 μm is formed on the other surface. If the incident surface is formed only by the shielding plate 51, the magnetic lines of force enter the detection device 10 through the incident surface due to the wraparound of the magnetic lines of force, so that the incident surface side is also formed of permalloy.

  Then, the effect | action of a present Example system is demonstrated. A command (instruction) for controlling the detection apparatus 10 is input from the pointing device 21 of the computer 20 or a program for controlling the detection apparatus 10 stored in the main body 22 is read out. Control like this.

That is, radiation that is a detection target is incident on the voltage application electrode 32 in a state where a bias voltage V _A of a high voltage (for example, about several hundred V to several tens kV) is applied.

  Carriers are generated by the incidence of radiation, and the carriers are stored in the charge storage capacitor Ca as charge information. The gate line 35 is selected by the scanning signal for signal extraction of the gate driver 39, and the detection element DU connected to the selected gate line 35 is selected and designated. The electric charge accumulated in the capacitor Ca of the designated detection element DU is read out to the data line 34 via the thin film transistor Tr that has been turned on by the signal of the selected gate line 35.

  Also, the address (address) designation of each detection element DU is performed based on the scanning signal for extracting signals from the data line 34 and the gate line 35. When a scanning signal for signal extraction is sent to the multiplexer 38 and the gate driver 39, each detection element DU is selected according to the scanning signal in the longitudinal (Y) direction from the gate driver 39. Then, when the multiplexer 38 is switched in accordance with the scanning signal in the horizontal (X) direction, the charge accumulated in the capacitor Ca of the selected detection element DU is transferred via the data line 34 to the voltage-voltage conversion group 37 and the multiplexer. The signal is sequentially sent to the signal processing board 42 through 38 and sent to the computer 20 outside the detection apparatus 10.

  With the above-described operation, for example, when the system according to the present embodiment is used to detect a fluoroscopic X-ray image of an X-ray fluoroscopic imaging apparatus, the charge information is converted into image information on the signal processing board 42 via the data line 34. And output as an X-ray fluoroscopic image by the computer 20. Specifically, the fluoroscopic image is output to a CRT monitor 23 of the computer 20 or a printer (not shown).

  According to the apparatus 10 of the present embodiment described above, the magnetic shield 50 formed of a magnetically permeable material typified by permalloy or the like is provided, and the magnetic shield 50 is arranged at a place where the detection apparatus 10 is not affected by magnetism. By providing the magnetic noise MN, that is, the magnetic lines of force are blocked along the magnetic shield 50 and do not reach the detection device 10. On the other hand, according to the system of the present embodiment, magnetic noise MN does not reach both the detection device 10 and the computer 20 by disposing the above-described magnetic shield 50 on the detection device 10 side. As a result, magnetic noise can be removed, and noise can be reduced by removing the noise.

  In the present embodiment, the radiation detector 30 is housed in a housing-like magnetic shield 50 so that the detection device 10 is not affected by magnetism, and the housing-like magnetic shield 50 is transmitted through, for example, permalloy. It is made of magnetic material. This casing does not allow the magnetic lines of force to enter the magnetic shield 50. Therefore, the magnetic shield 50 can be easily realized by the housing without allowing the magnetic lines of force to wrap around the detector 30 accommodated in the magnetic shield 50, that is, without allowing magnetic noise.

  In the present embodiment, the permalloy has conductivity, and the permalloy is configured to be grounded so that electric noise escapes through the grounded permalloy. As a result, not only magnetic noise but also electrical noise can be removed, and noise can be further reduced by removing these noises.

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

  (1) In the above-described embodiment, the present invention is applied to the direct conversion type radiation detection apparatus in which incident radiation is directly converted into charge information by the semiconductor thick film 31 (semiconductor layer), but the incident radiation is scintillator. The present invention may be applied to an indirect conversion type radiation detector that converts light into charge information by means of a semiconductor layer formed of a light sensitive substance. In addition, the present invention may be applied to a photodetector that converts incident light into charge information by a semiconductor layer formed of a photosensitive material.

  (2) In the above-described embodiments, the case of detecting X-rays has been described as an example. However, the present invention can also be applied to a detection device that detects γ-rays used in a nuclear medicine apparatus or the like.

  (3) In the above-described embodiment, the magnetic shield 50 is configured in a casing shape, and the detector 30 is accommodated in the casing so that the detection apparatus 10 is not affected by magnetism. As shown in FIG. 5, the magnetic shield may be disposed with the height of the wall of the magnetic shield S so high that the noise due to the wraparound of the magnetic lines of force MN can be ignored. However, the structure of the embodiment is more preferable in that the magnetic shield is easily realized and the magnetic field lines are not allowed to wrap around.

(4) In the above-described embodiment, the magnetically permeable material is made of permalloy. However, if the magnetically permeable material is normally used, for example, silicon steel, manganese zinc (Mn-Zn) ferrite, iron (Fe) based amorphous, etc. It is not specifically limited like. Further, the higher the magnetic permeability, the more effective as a magnetic shield. Preferably, it is made of a magnetically permeable material having a relative magnetic permeability of about 10 ³ or more, such as silicon steel, and more preferably a relative magnetic permeability of 10 ⁴ or more, such as permalloy.

  (5) In the above-described embodiment, the magnetically permeable material represented by permalloy has conductivity, and the permalloy is grounded to remove electrical noise, but does not remove electrical noise. If it is, even if it is a magnetically permeable substance, it does not need to have electroconductivity. For example, the iron core of the coil is a magnetically permeable material but has no electrical conductivity. Such an iron core may be formed as a magnetic shield.

  (6) In the embodiment described above, the magnetic shield 50 is provided only on the radiation detection apparatus 10 side as shown in FIG. 1, but if the magnetic shield 50 is provided at least on the detection apparatus 10 side, In addition to the detection device 10 side, a magnetic shield may be applied to, for example, the CRT monitor 23 on the computer 20 side, or the magnetic shield wall described in the modification (3), for example, at a location between the detection device 10 and the computer 20. (See FIG. 5) may be provided.

  In addition, in the embodiment system as a whole, it is not necessary to provide the magnetic shield 50 on the radiation detection device 10 side, and at least the control device represented by the detection device 10, the computer 20, etc., the detection device 10 / control. What is necessary is just to arrange | position a magnetic shield in the somewhere between apparatuses. The number of magnetic shields to be provided may be only one, two or more, or shields may be provided at all locations.

It is the schematic of the radiation detection control system which has the radiation detection apparatus which concerns on an Example. It is a schematic sectional drawing of the radiation detection apparatus which concerns on an Example. FIG. 3 is a circuit diagram illustrating FIG. 2 in an equivalent circuit. It is the circuit diagram represented planarly. It is a schematic sectional drawing of the radiation detection apparatus which concerns on a modification. It is explanatory drawing of each noise in the knowledge based on this invention, Comprising: (a) is explanatory drawing regarding electrical noise, (b) is explanatory drawing regarding magnetic noise. It is explanatory drawing regarding the magnetic noise at the time of arrange | positioning the wall of a magnetic shield.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Radiation detection apparatus 20 ... Computer 23 ... CRT monitor 30 ... Radiation detector 31 ... Semiconductor thick film 36 ... Insulating substrate 50 ... Magnetic shield

Claims (6)

  A light or radiation detection device comprising a semiconductor layer for converting light or radiation information into charge information upon incidence of light or radiation, and detecting light or radiation by reading the converted charge information, wherein the magnetically permeable material A light or radiation detection apparatus comprising the magnetic shield formed by the above-described method, wherein the magnetic shield is disposed at a location where the detection apparatus is not affected by magnetism.   The light or radiation detection apparatus according to claim 1, wherein a radiation detector including the semiconductor layer and a readout substrate that reads the charge information is housed in a housing, and the housing is formed of the magnetically permeable material. Feature light or radiation detection device.   3. The light or radiation detection device according to claim 1, wherein the magnetically permeable material has electrical conductivity, and is configured by grounding the magnetically permeable material having electrical conductivity. Radiation detection device.   4. The light or radiation detection device according to claim 1, wherein the semiconductor layer is a radiation-sensitive type that directly converts the information of the radiation into charge information, and the detection device includes: A light or radiation detection device characterized in that it is a direct conversion radiation detection device provided with a radiation sensitive semiconductor layer.   A light or radiation detection device that includes a semiconductor layer that converts light or radiation information into charge information upon incidence of light or radiation, detects light or radiation by reading the converted charge information, and controls the detection device A light or radiation detection control system constructed with a control device that performs the above, comprising a magnetic shield formed of a magnetically permeable material, and at least any location between the detection device, the control device, and the detection device / control device A light or radiation detection control system, wherein the magnetic shield is disposed on the surface. 6. The light or radiation detection control system according to claim 5, wherein the magnetic shield is provided at least on the detection device side.

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