JP2009128212A - Radiation measuring circuit and nuclear medicine diagnosing apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation measuring circuit of a semiconductor radiation detector which exhibits good electric conduction when measuring radiation, and also to provide a nuclear medicine diagnosing apparatus using the radiation measuring circuit. <P>SOLUTION: The semiconductor radiation detector 21 is made up by bonding conductive members 22, 23 and electrodes A, C of a conductive thin film which is formed on the surface of a semiconductor element S, with a conductive adhesive 24. The radiation measuring circuit 100 includes the semiconductor radiation detector 21, a resistor 41, a capacitor 43, a preamplifier 45, a high-voltage supply 27, a control means 30, a voltage regulating means 31, a mechanical relay 33, a protection diode 48, and the like. The mechanical relay 33 is turned on and off so as to recover the conduction of the conductive adhesive 24 of the semiconductor radiation detector 21 in a state of a prescribed second high voltage which is equal to or less than a first high voltage used for an operation of recovering the conduction of the conductive adhesive 24. Since the protection diode 48 is disposed therein, the preamplifier 45 is prevented from being damaged owing to a high voltage occurring along with above on-off operation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a crystal element assembly in which a conductive member for connecting to an external electric circuit in order to use the crystal element as a functional element is a semiconductor radiation detector, and the conductive member in the semiconductor radiation detector The present invention relates to a radiation measurement circuit for maintaining good electrical continuity with a crystal element and processing a radiation detection signal, and a nuclear medicine diagnostic apparatus using the radiation measurement circuit.

In recent years, gamma cameras, single-photon emission tomography (SPECT (Single Photon Emission Computed Tomography) equipment), and positron emission tomography (PET (Positron Emission Tomography)) have been used as devices that apply radiation measurement technology to the medical field. A device for nuclear medicine diagnosis is known. Most of the radiation detectors used in these apparatuses are a combination of a scintillator and a photomultiplier tube. On the other hand, the use of a semiconductor instead of a scintillator as a radiation detector is described in Patent Document 1 and Patent Document 2, for example.
In such a semiconductor radiation detector, electrons and holes are generated by the photoelectric effect caused by the γ rays incident on the crystal of the semiconductor element, and moved by an electric field generated by an externally applied voltage, and the electric charge is transferred to the outside. Since the amount of charge is proportional to the energy of radiation, the energy of radiation can be accurately known by accurately measuring the amount of charge. Therefore, the semiconductor has an advantage that the radiation energy can be measured more accurately than the combination of the scintillator and the photomultiplier tube.
Further, the semiconductor radiation detector has a feature that the position detection accuracy is better than the combination of a scintillator and a photomultiplier tube.

  By the way, as a semiconductor for detecting radiation, particularly γ-rays, the effective atomic number is large in terms of measuring γ-rays used in nuclear medicine diagnostic devices such as gamma cameras, SPECT devices, and PET devices with high sensitivity. A method using cadmium telluride (CdTe) or zinc cadmium telluride (CdZnTe), which can be operated at room temperature in terms of handling, is known. Here, silicon and germanium are also used, but these are often used for X-ray detection because of their low sensitivity to high energy γ rays. As radioactive materials used in nuclear medicine diagnosis, for example, technetium 99m and fluorine 18 are known, and the energy of γ-rays emitted from these radioactive materials is 141 keV or 511 keV, and has a high permeability to the material. . Therefore, it is advantageous to use a substance having a large atomic number for the radiation detector to absorb a large amount of γ rays and output a radiation detection signal. In this respect, CdTe and CdZnTe have an advantage that they have an excellent ability to absorb γ rays because they have a large average atomic number.

When a semiconductor crystal such as CdTe or CdZnTe is used as a radiation detection element of a radiation detector, an anode electrode and a cathode electrode are provided on the semiconductor crystal. A conductive thin film is usually used for the anode electrode and the cathode electrode, and a conductive member is connected to the anode electrode and the cathode electrode in order to connect the anode electrode and the cathode electrode to an external circuit. At this time, since CdTe and CdZnTe are brittle and have a heat-resistant temperature of about 180 ° C., it is difficult to connect the anode and cathode electrodes to the conductive member by solder.
Incidentally, when electrically connecting electronic components with solder, the heat-resistant temperature is approximately 250 ° C.
Therefore, when an anode electrode and a cathode electrode formed by vapor deposition or sputtering on a CdTe or CdZnTe semiconductor crystal and a conductive member are connected, a conductive adhesive is used as a bonding member.

The conductive adhesive is a mixture of epoxy and other resin binders with a flake of conductive material such as silver called filler, and the resin shrinks during the resin curing process so that the fillers come into contact with each other and become conductive. To be expressed. Therefore, the bonding with the conductive adhesive is different from, for example, the connection relationship between solder and copper, and is rather close to a point contact.
On the other hand, a semiconductor radiation detection element using a semiconductor crystal such as CdTe or CdZnTe is usually applied with a bias voltage of about several tens to several hundreds of volts at the time of radiation measurement. For example, when a gamma ray is incident, a pulse current signal of several tens to several hundred nanoamperes is superimposed on the leakage current and flows for a moment.

Actually, a conductive thin film of an anode electrode and a cathode electrode is formed on the opposing surfaces of the conductive member and the CdTe semiconductor crystal, and the anode electrode and the cathode electrode are faced to each other as a unit. A conductive member was interposed between them, and the anode and cathode electrodes and the conductive member were bonded together with a conductive adhesive, and the units were laminated to produce a semiconductor radiation detector. However, when this manufactured semiconductor radiation detector was experimentally used for several months, the noise of the radiation detection signal (charge signal) increased in some semiconductor radiation detectors, resulting in a decrease in energy resolution and the like.
This is because conduction becomes unstable due to a decrease in the shrinkage of the conductive adhesive that bonds the conductive member, the anode electrode, and the cathode electrode after long-term use, or oxidation of the conductive material of the filler. It was inferred to be caused.

On the other hand, the charge generated in the semiconductor radiation detector due to the input of radiation is a small amount of several femtocoulombs to several tens of femtocoulombs, and the current value is less than microamperes. For this reason, when such a weak signal passes through the unstable part of the conductivity, there is a possibility that the signal may be distorted, which appears as deterioration of the semiconductor radiation detector, leading to a decrease in energy resolution. There was also.
On the other hand, in Patent Document 3, a small current is applied to the conductive adhesive during normal measurement, and when a large current is applied to improve the conduction of the conductive adhesive, the semiconductor radiation detector is illuminated by a light source. A technique is described in which the current flows to the ground side via a protection circuit so that the current does not flow to the amplifier.

JP 2004-317140 A Japanese Patent Laid-Open No. 2005-1006644 JP 2007-139479 A

  However, in the technique described in Patent Document 3, it is difficult to uniformly irradiate a large number of semiconductor radiation detectors arranged on a substrate with a light source, and a uniform high current is applied to each semiconductor radiation detector. It was difficult to flow through the portion where the material was used, and there was a problem in maintaining good conductivity of the conductive adhesive.

  Accordingly, an object of the present invention is to provide a radiation measurement circuit using a crystal element assembly as a semiconductor radiation detector, which has good electrical continuity during radiation measurement, and is excellent in stable energy resolution using this radiation measurement circuit. It is to provide a nuclear medicine diagnostic apparatus.

In order to achieve the above-described object, the radiation measuring circuit according to the first invention of the present application includes two elements for electrically connecting the conductive thin film formed on the surface of the crystal element, which is a functional element, to the outside. Occurs when radiation is incident on the crystal element assembly by providing a conductive member and bonding the conductive thin film to the conductive member with a conductive adhesive composed of conductive particles and a binder. A semiconductor radiation detector that extracts electric charge as a signal via a conductive adhesive and a conductive member, an amplifier that amplifies and shapes the signal from the semiconductor radiation detector, and a high voltage applied to one conductive member of the crystal element assembly A voltage adjusting hand that is interposed between the high-voltage power supply to be supplied and the high-voltage power supply and one of the conductive members, and sets the voltage supplied from the high-voltage power supply to a predetermined first high voltage in the radiation measurement state. When a radiation measurement circuit comprising,
Furthermore, a relay switch arranged after the voltage adjusting means, and a control means for controlling the voltage adjusting means and the relay switch,
The control means causes the voltage adjustment means to set the high voltage from the high voltage power supply to a predetermined second high voltage that is equal to or lower than the first high voltage for the conduction recovery work of the conductive adhesive, and in the relay switch, The on / off operation is performed to restore the conduction of the conductive adhesive of the semiconductor radiation detector.

The radiation measuring circuit of the second invention of the present application is provided with two conductive members for electrically connecting to the outside with respect to the conductive thin film formed on the surface of the crystal element which is a functional element. The conductive thin film and the conductive member are bonded to each other by a conductive adhesive composed of a binder and a crystal element assembly, and charges generated when radiation is incident on the crystal element assembly are transferred to the conductive adhesive and the conductive material. A semiconductor radiation detector that extracts a signal via a member, an amplifier that amplifies and shapes the signal from the semiconductor radiation detector, a high-voltage power source that supplies a high voltage to one conductive member of the crystal element assembly, In a radiation measurement circuit comprising: a voltage adjusting unit that is interposed between a voltage power source and one conductive member and sets a voltage supplied from the high voltage power source to a predetermined high voltage.
Further, a relay switch arranged at a subsequent stage of the voltage adjusting means, a control means for controlling the voltage adjusting means and the relay switch, and an amplifier for a signal line connected to the other conductive member of the crystal element assembly and taken out as a signal A first capacitor having a predetermined first capacitance connected in front of the first capacitor and a sufficiently larger than the first capacitance arranged in series with the first capacitor on the semiconductor radiation detector side A second capacitor having a predetermined second capacitance, and a protection circuit that is grounded via a protection diode from an intermediate connection point of the signal line between the first capacitor and the second capacitor. Prepared,
The control means is characterized in that the voltage adjusting means is set to a predetermined high voltage, and the relay switch is turned on / off to perform conduction recovery work of the conductive adhesive of the semiconductor radiation detector.

According to the first and second inventions, the large electric current that flows when the control means turns on / off the relay switch re-couples the conductive particles of the conductive adhesive material of the adhesive structure portion, The oxide film formed on the adhesive can be broken, and the conductivity of the conductive adhesive can be stabilized.
Furthermore, according to the second aspect of the present invention, when the conductive adhesive of the semiconductor radiation detector is restored in conduction, a high current is caused to flow to the ground side by the second capacitor and the protection circuit, and the protection circuit does not operate during radiation measurement. Therefore, noise due to the protection circuit does not enter the radiation detection signal sent to the amplifier side.

A nuclear medicine diagnostic apparatus according to a third invention of the present application is characterized by using the radiation measurement circuit according to the first invention or the second invention.
According to the third invention, the occurrence of failure due to unstable conduction is effectively suppressed by turning on and off the relay switch while a predetermined high voltage is applied to the semiconductor radiation detector for radiation measurement. The radiation detection performance can be maintained over a long period of time.

  According to the present invention, a radiation measurement circuit using a crystal element assembly as a semiconductor radiation detector having good electrical continuity at the time of measurement, and a stable nuclear medicine diagnosis using this radiation measurement circuit with excellent energy resolution An apparatus can be provided.

<< First Embodiment >>
Next, a PET apparatus (nuclear medicine diagnostic apparatus), which is a preferred first embodiment of the present invention, will be described in detail with reference to the drawings, with reference to the drawings as appropriate.
(Semiconductor radiation detector)
First, a detailed configuration of the semiconductor radiation detector used in the present embodiment will be described.
FIG. 1 is a perspective view of an example of a semiconductor radiation detector in the present embodiment, (a) is a schematic perspective view of a semiconductor radiation detection element of a unit constituting the semiconductor radiation detector, and (b) is It is a perspective view of a semiconductor radiation detector constituted by laminating a plurality of semiconductor radiation detection elements, and (c) is a diagram schematically showing a state in which the semiconductor radiation detector is installed on a wiring board.

  A semiconductor radiation detector (crystal element assembly) 21 is a semiconductor radiation detection element in which two thin film-like electrodes (conductive thin films) A and C are formed on the surface of a semiconductor element (crystal element) S so as to be separated from each other. 211 and conductive members 22 and 23 connected to the electrodes A and C, respectively.

  As shown in FIG. 1A, the semiconductor radiation detection element 211 is a thin film-like electrode formed on a semiconductor element S made of a plate-like semiconductor material over the entire surface of both side surfaces by sputtering or vapor deposition. Is formed. The electrode formed on one surface is the anode electrode A, and the electrode formed on the other surface is the cathode electrode C.

The semiconductor element S is a region that generates charges by interacting with radiation, and is formed of any single crystal such as CdTe, CdZnTe, or GaAs. The cathode electrode C and the anode electrode A are made of any material such as platinum (Pt), gold (Au), indium (In). In the semiconductor radiation detector 21, the semiconductor radiation detection element 211 uses, for example, CdTe for the semiconductor element S, a cathode electrode C mainly containing Pt, an anode electrode A mainly containing In, and a pn junction diode. Forming.
Here, the names of the anode electrode A and the cathode electrode C are referred to as an electrode on the side where electrons generated in the semiconductor element S are collected by a high voltage power source applied when used as the semiconductor radiation detector 21. The electrode A and the electrode on the side where holes are collected are referred to as a cathode electrode C.
The thickness (interelectrode distance) t of the semiconductor element S is preferably 0.2 mm to 2.0 mm.

  The conductive members 22 and 23 are flat members formed of at least one of iron-nickel alloy, iron-nickel-cobalt alloy, chromium, and tantalum, for example. Here, 42 alloy (Fe 58%, Ni 42%) can be used as the iron-nickel alloy, and Kovar (Fe 54%, Ni 29%, Co 17%) can be used as the iron-nickel-cobalt alloy. .

In the present embodiment, the conductive members 22 and 23 are formed so as to cover each electrode surface of the semiconductor radiation detection element 211, that is, larger than each electrode surface.
Note that the size of the conductive members 22 and 23 may be the same as that of the semiconductor radiation detection element 211. The thickness of the conductive members 22 and 23 is about 10 μm to 100 μm, preferably about 50 μm.

  Such conductive members 22 and 23 hang down below the semiconductor radiation detection element 211 (on the wiring board 20 side) as shown in FIG. Projecting portions 22a, 23a. The protrusions 22 a and 23 a function as a fixing part for attaching the semiconductor radiation detector 21 to the wiring board 20, and the protrusion 22 a is connected to the wiring CP for the cathode electrode C provided on the wiring board 20. The protrusion 23a is connected to the wiring AP for the anode electrode A provided on the top. Further, the semiconductor radiation detector 21 is brought into a non-contact state on the wiring board 20 by these protrusions 22a and 23a, that is, the semiconductor radiation detection element 211 has a predetermined gap between the semiconductor radiation detector 21 and the wiring board 20. It is attached.

Such conductive members 22 and 23 are attached to the semiconductor radiation detection element 211 by a conductive adhesive 24 as shown in FIG. However, in FIG. 2, the semiconductor radiation detector 21 is configured by a single semiconductor radiation detection element 211 and is schematically simplified and displayed.
As the conductive adhesive 24, for example, a conductive particle (filler) such as metal powder (silver) dispersed in an insulating resin binder (binder) made of an organic polymer material is used. Usually, when the semiconductor radiation detection element 211 and the conductive members 22 and 23 are bonded by the conductive adhesive 24, a high-temperature heat treatment at about 120 to 150 ° C. is performed in order to cure the conductive adhesive 24. Is called. The conductive adhesive 24 having such a component develops conductivity when fillers come into contact with each other when the resin shrinks during the curing process of the resin.

In the present embodiment, the semiconductor elements S arranged in parallel have the thickness t (0.2 to 2.0 mm), and the thicknesses of the cathode electrode C and the anode electrode A are at most several μm. Set to degree. In the semiconductor radiation detector 21, since the cathode electrodes C and the anode electrodes A of the plurality of semiconductor radiation detection elements 211 are connected in common, the semiconductor element S of which semiconductor radiation detection element 211 interacts with γ rays. It is configured not to determine whether it has occurred.
The configuration of the semiconductor radiation detector 21 as described above reduces the thickness t of the semiconductor element S to increase the charge collection efficiency, increases the rising speed of the peak value of the radiation detection signal, and improves the energy resolution. This is to reduce the amount of γ rays that pass through the parallel arrangement of the semiconductor elements S and increase the interaction between the semiconductor elements S and γ rays (to increase the count number of γ rays). Increasing the count number of γ rays improves the sensitivity of the semiconductor radiation detector 21.

(Radiation measurement circuit)
Next, the radiation measurement circuit of this embodiment will be described with reference to FIG. FIG. 2 is a schematic diagram for explaining the principle for explaining the configuration and operation of the radiation measurement circuit applied to the PET apparatus according to the present embodiment.
Note that a large number of semiconductor radiation detectors 21 are incorporated in the nuclear medicine diagnosis apparatus, and a radiation measurement circuit 100 is provided for each of them. Here, a single radiation measurement circuit 100 will be representatively described.

A positive voltage is applied to the anode electrode A of each semiconductor radiation detection element 211 of each semiconductor radiation detector 21 from the high voltage power supply 27 via the voltage adjusting means 31 and the mechanical relay (relay switch) 33. At this time, the conductive member (one conductive member) 23 is connected to the positive electrode of the high voltage power supply 27 via the wiring AP.
The high voltage power supply 27, the voltage adjustment unit 31, the mechanical relay 33, the voltage adjustment unit 31, and the control unit 30 that controls the mechanical relay 33 are provided in common for the plurality of radiation measurement circuits 100.

The control means 30 is a control circuit including a microcomputer, a memory, and its peripheral circuits, and controls the voltage adjusting means 31 and the mechanical relay 33 by the microcomputer executing the program stored in the memory as described above. The control means 30 includes a solenoid drive circuit for exciting a solenoid (not shown) of the mechanical relay 33. The control means 30 is incorporated in, for example, the PET imaging apparatus 1 of the PET apparatus 10 (see FIG. 4), and starts the PET apparatus 10 from the console 3 (see FIG. 4), that is, the mechanical relay 33 is turned on. Thus, a first high voltage described later for radiation measurement is applied to the semiconductor radiation detector 21. Further, the control means 30 receives a control command for the continuity recovery operation from the console 3 (see FIG. 4) automatically, and with the second high voltage described later, while the mechanical relay 33 is kept in the OFF state. It is applied to the radiation detector 21, and then the mechanical relay 33 is turned on / off to restore the conduction.
Incidentally, the control means 30 has a function of storing the calendar / clock function, the date and time when the continuity recovery work is performed, and the like in a memory.
Details of the control of the continuity recovery operation will be described in the explanation of the operation of the radiation measurement circuit 100.

The voltage adjusting means 31 is controlled by the control means 30 to set the high voltage supplied from the high voltage power supply 27 to a predetermined high voltage. The voltage adjustment unit 31 applies a predetermined first high voltage, for example, a voltage of about 500 V, to the semiconductor radiation detector 21 when the PET apparatus 10 (see FIG. 4) is activated and enters the radiation measurement state. At that time, the semiconductor radiation detector 21 and a preamplifier (amplifier) 45 to be described later are slowly boosted to set the first high voltage as described above.
The voltage adjusting means 31 is controlled by the control means 30 and is set to a predetermined second high voltage when the conduction recovery work of the conductive adhesive 24 of the semiconductor radiation detector 21 is periodically performed. .
Also at this time, the voltage is gradually increased to a predetermined second high voltage.
The predetermined second high voltage is a voltage lower than the first high voltage, for example, about 100 to 200V.
In the present embodiment, the high voltage power supply 27 and the voltage adjusting means 31 are distinguished from each other. However, the high voltage power supply 27 itself has a function of being set by the control means so that the voltage can be set to a predetermined high voltage. The one integrated with 31 may be used.

  The mechanical relay 33 is a normal normally open (non-energized) electromagnetic switch, and the on / off operation is controlled by the control means 30.

As shown in FIG. 2, the cathode electrode C of each semiconductor radiation detection element 211 of the semiconductor radiation detector 21 is connected to a detection circuit 40 prepared for each semiconductor radiation detector 21. At this time, the conductive member (the other conductive member) 22 is connected to the capacitor 43 on the signal line SC through the above-described wiring CP, and further connected to the preamplifier 45 at the subsequent stage of the capacitor 43. A signal processing circuit such as a fast system or a slow system is connected to the subsequent stage of the preamplifier 45. However, since it is a known technique in Patent Document 2 and the like, detailed description thereof is omitted.
A resistor 41 is connected to an intermediate point of the signal line SC between the wiring CP and the capacitor 43, and the opposite side of the resistor 41 connected to the conductive member 22 is grounded. Further, from the connection point on the semiconductor radiation detector 21 side of the signal line SC connected to the capacitor 43, the two protection diodes 48 and 48 are arranged in parallel with the cathode and anode being opposite to each other and grounded.

The two protection diodes 48 and 48 constitute a protection circuit 49 that prevents the preamplifier 45 from being damaged by a voltage generated by an excessive current during the conduction recovery operation of the conductive adhesive 24. In the state where the second high voltage is applied to the mechanical relay 33, the current when the mechanical relay 33 is turned on from the off state, and conversely, when the mechanical relay 33 is turned off from the state. It plays the role of flowing the reverse current of between the ground side.
Here, the protection diodes 48 correspond to the diodes recited in the claims.

In the present embodiment, the high-voltage power supply 27 to the preamplifier 45 are referred to as a radiation measurement circuit 100, and signal processing circuits such as a fast system and a slow system are not included.
Incidentally, the resistor 41 serves to release leakage current from the semiconductor radiation detector 21 and to prevent charge from being accumulated in the capacitor 43 for a long time. The
The capacitor 43 is for preventing leakage current from the semiconductor radiation detector 21 from entering the preamplifier 45.
A capacitor 46 and a resistor 47 are connected in parallel between the input side terminal and the output side terminal of the preamplifier 45.

(Operation of radiation measurement circuit during radiation measurement)
First, the case of normal radiation measurement will be described.
Here, when the control means 30 receives the control command for the start operation from the console 3, it determines, for example, whether or not it is a predetermined day of the week, which is previously input from the console 3 and stored in the memory, based on a calendar / clock function. However, if it is not the predetermined day of the week, the mechanical relay 33 is turned on, and then the voltage is adjusted to the first high voltage for radiation measurement by controlling the voltage adjusting means 31 and the voltage is applied to the semiconductor radiation detector 21. Is applied.
If the first high voltage is thus applied to the semiconductor radiation detector 21 and no γ rays are incident on the semiconductor radiation detector 21, there are very few carriers generated in the semiconductor element S, and from the conductive member 23. A leakage current of about several nanometers to several tens of nanoamperes flows through the semiconductor radiation detector 21 to the conductive member 22. This leakage current flows through the resistor 41 to the ground side.

When γ rays are incident on the semiconductor element S, carriers are generated, and a current flows through the semiconductor radiation detector 21 from the conductive member 23 to the conductive member 22 by an amount corresponding to the charge of the carriers. The electric charge charges the capacitor 43 through the signal line SC and is transmitted to the preamplifier 45 as a radiation detection signal. Thereafter, the electric charge charged in the capacitor 43 is discharged through the resistor 41.
Since the radiation detection signal described above is a weak signal, it is amplified by the preamplifier 45 and then input to a signal processing circuit of a fast system or a slow system (not shown). The slow signal processing circuit includes a waveform shaper (corresponding to the bandpass filter 24d in FIG. 8 of Patent Document 2) and a wave height analyzer (corresponding to the peak hold circuit 24e in FIG. 8 of Patent Document 2). In the wave height analyzer, γ-ray energy analysis is performed. Further, γ-ray detection (detection of γ-ray detection timing) is performed in the first signal processing circuit.

(Operations when radiation measurement circuit continuity is restored)
Next, the case of the conduction recovery operation of the conductive adhesive 24 of the semiconductor radiation detector 21 will be described.
Here, when the control means 30 receives the control command for the start operation from the console 3, it determines, for example, whether or not it is a predetermined day of the week, which is previously input from the console 3 and stored in the memory, based on a calendar / clock function. In the case of a predetermined day of the week, with the mechanical relay 33 kept in the OFF state, the voltage is first applied to the semiconductor radiation detector 21 by setting the second high voltage lower than the first high voltage for radiation measurement. To do. Thereafter, the control means 30 turns the mechanical relay 33 from the off state to the on state.
Then, a voltage is suddenly applied to the semiconductor radiation detector 21 in nanosecond order. The semiconductor radiation detection element 211 has a capacitance of several to several tens of pF (picofarad), and a large charge current of several milliamperes or more is instantaneous but the conductivity of each side of the conductive members 22 and 23. It flows to the adhesive 24.
With this current, the contact failure between the fillers of the conductive adhesive 24 can be recovered, the oxide film of the filler can be destroyed, the contact failure can be recovered, and conduction recovery and conduction deterioration can be prevented.

(Protection circuit operation)
Next, the operation of the protection circuit 49 will be described.
In the state of radiation measurement, the leakage current of the semiconductor radiation detector 21 is normally several nanoamperes and about 20 nanoamperes at the maximum as described above, and it flows to the ground side via the resistor 41. Due to this leakage current, a potential of about 0.2 V at maximum is generated at the terminal on the connection side of the capacitor 43 with the resistor 41 when a resistor 41 having a resistance of 10 MΩ is used. On the other hand, the operating potential of the normal protection diode 48 is about 0.4 V, and the protection diode 48 is kept off in the state of only leakage current or the state where the radiation detection signal is input, and the signal does not operate. There is no noise on the line SC.

When the mechanical relay 33 is switched from the off state to the on state with the second high voltage applied to the mechanical relay 33 for the continuity recovery work, the potential of the terminal on the protection circuit 49 side of the capacitor 43 rises, and the protection diode 48 In operation, an excessive current is released to the ground side, and an excessive voltage is not applied to the capacitor 43 and the preamplifier 45.
It is a generally known technique to use a limiter circuit in which two protection diodes 48 are arranged in parallel in the opposite direction. For example, it is described in the document “Practical know-how of OP amplifier utilization 100” (Kunihiko Matsui, CQ Publishing Co., Ltd.).

  However, when a limiter circuit is used, noise may increase significantly. As the protection diodes 48 and 48, it is preferable to use high-frequency diodes or PIN diodes that can have their own leakage current smaller than that of the semiconductor radiation detector 21 and have a small capacitance.

  In addition, after the conduction recovery operation of the conductive adhesive 24, the control unit 30 turns on the mechanical relay 33 and controls the voltage adjusting unit 31 to slowly increase the applied voltage to the first high voltage. And it shifts to the state of radiation measurement.

  Incidentally, although the frequency of the above-described continuity recovery work is once a week, it is not limited thereto. It may be performed every predetermined number of days stored and set in the memory of the control means 30. Further, the control means 30 may perform the continuity recovery work even when a predetermined number of days have passed since the previous continuity recovery work stored in the memory.

  In the continuity recovery operation, the mechanical relay 33 is described as being only once from the off state to the on state, but is not limited thereto. After the mechanical relay 33 is turned from the off state to the on state, the mechanical relay 33 may be turned off again and turned on. This number can be selected as appropriate.

(Radiation measurement circuit of comparative example)
Next, the radiation measurement circuit of the comparative example of FIG. 3 will be described.
The semiconductor radiation detector 21 in the radiation measurement circuit 110 of FIG. 3 is the same as that of the first embodiment, but the connection is different. The conductive member 22 on the cathode electrode C side is grounded, and a high voltage is applied to the conductive member 23 on the anode electrode A side via the mechanical relay 33 and the resistor 41. The signal line SC is drawn from the conductive member 23 and connected in series with the capacitor 43 and the preamplifier 45.
About the same structure as 1st Embodiment, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

A device obtained by removing the mechanical relay 33 from the radiation measurement circuit 110 is often used since the conductive member 22 of the semiconductor radiation detector 21 is at a ground potential and is easy to handle.
In this case, in a normal radiation measurement state, the mechanical relay 33 is in an on state, and a predetermined first high voltage is applied to the conductive member 23 of the semiconductor radiation detector 21 via the resistor 41. The capacitor 43 is also charged. Here, when γ rays are incident on the semiconductor element S, carriers are generated in the semiconductor element S, and a current corresponding to the generated charge flows from the signal line SC side to the ground side through the conductive member 23. Due to this current, the electric charge charged in the capacitor 43 flows, becomes a radiation detection signal, and is transmitted to the preamplifier 45. Thereafter, the capacitor 43 is charged again by the high voltage power supply 27 via the resistor 41.

  However, since the resistor 41 is about 10 MΩ and the capacitance of the semiconductor radiation detector 21 is several to several tens of pF, the mechanical relay 33 is turned off and the applied voltage is set to the second high voltage described above, After that, even if the mechanical relay 33 is turned on, the high voltage cannot be applied to the semiconductor radiation detector 21 in the order of several nanoseconds.

  Further, by inserting the mechanical relay 33 on the signal line SC between the conductive member 23 and the connection point of the resistor 41 to the signal line SC, the high voltage is changed in the order of several nanoseconds, thereby detecting the semiconductor radiation detector. 21. In this case, however, the radiation detection signal from the semiconductor radiation detector 21 always passes through the mechanical relay 33 in the normal radiation measurement state, and noise enters the signal.

  Further, the mechanical relay 33 can be inserted between the conductive member 22 and the ground, but this time, since the conductive member 22 cannot always be maintained in the grounded state, the advantage of the radiation measuring circuit 110 described above, that is, the simplicity of the connection. Cannot be obtained.

  Incidentally, in this embodiment, the mechanical relay 33 is normally open. However, when the mechanical relay 33 is normally closed and a current of several μamperes or less flows normally, the contact of the canal relay 33 is oxidized. In view of preventing contact sticking, it is desirable to prevent the contact sticking by operating the mechanical relay 33 from the off state to the on state each time the PET apparatus 10 is operated. Further, for the conduction recovery work, for example, since the second high voltage state is changed from the off state to the on state at a frequency of once a week, it is useful for maintaining the continuity of the contact of the mechanical relay 33.

(PET device)
Next, a PET apparatus according to this embodiment suitable as a nuclear medicine diagnostic apparatus of the present invention will be described in detail with reference to FIGS.
FIG. 4 is a perspective view schematically showing the configuration of a PET apparatus suitable as the nuclear medicine diagnostic apparatus of this embodiment. FIG. 5 is a perspective view schematically showing a PET imaging apparatus. 6A is a front view of a unit substrate used in the PET imaging apparatus shown in FIG. 5, and FIG. 6B is a side view of the unit substrate.
As shown in FIG. 4, the PET apparatus 10 of the present embodiment includes a PET imaging apparatus 1 having a measurement space 1a, a bed B that supports a subject (examinee) H, a data processing apparatus (computer or the like) 2, In addition, a console 3 having a display device 3a, an operation device 3b, and the like is provided. The PET imaging apparatus 1 has a large number of unit substrates U arranged in the circumferential direction of the measurement space 1a as shown in FIG. 5, and in such a PET imaging apparatus 1, the subject H is as shown in FIG. It is placed on a bed B movable in the longitudinal direction and inserted into a cylindrical measurement space 1a surrounded by the unit substrate U.

  As shown in FIG. 5, a plurality of unit substrates U of the PET imaging apparatus 1 are also arranged in the longitudinal direction of the bed B (the arrow Z direction in the figure). As shown in FIG. 6, the unit substrate U has a radiation detection region (hereinafter referred to as a detection region) 20A and an integrated circuit region (hereinafter referred to as an ASIC (Application Specific Integrated Circuit) region) 20B. The detection region 20 </ b> A includes a plurality of semiconductor radiation detectors 21. The semiconductor radiation detector 21 detects γ rays emitted from the body of the subject H (see FIG. 4).

  The ASIC region 20B has an integrated circuit (analog ASIC 28, digital ASIC 29) for measuring the peak value and detection time of the radiation detection signal by the detected γ-ray, and the peak value and detection time of the radiation detection signal are displayed. It comes to measure. The integrated circuit includes a plurality of signal processing devices that process radiation detection signals.

(PET imaging device)
Next, details of the PET imaging apparatus 1 will be described.
The semiconductor radiation detector 21 shown in FIG. 1 is used as the semiconductor radiation detector 21 shown in FIGS. Such a semiconductor radiation detector 21 is arranged on the wiring board 20 in the Y direction (radial direction of the PET imaging apparatus 1 from the detection area 20A to the ASIC area 20B, as shown in FIGS. 6A and 6B). 6 rows (6 ch) in the X direction (circumferential direction of the PET imaging device 1, see FIG. 5) orthogonal to the Y direction, 8 rows (8 ch), and the Z direction which is the thickness direction of the wiring board 20 Two surfaces (2ch) are arranged (disposed on both surfaces of the wiring board 20) in the depth direction of the PET imaging device 1 (see FIG. 5). As a result, the semiconductor radiation detector 21 is provided with a total of 48 ch on one side of the wiring board 20 and a total of 96 ch on both sides.

In the present embodiment, in order to maintain the gamma ray detection function of each semiconductor radiation detector 21 as described above, the control means 30 for ensuring the conductivity of the conductive adhesive 24 described in FIG. Means 31 and a mechanical relay 33 are provided. Among these, the control means 30 and the voltage adjustment means 31 are installed in a housing (not shown) that stores the unit substrate U (for example, the high-voltage device PS of the housing 30 shown in FIG. 10 of Patent Document 2). Included). Then, one mechanical relay 33 is installed on each side of the wiring board 20 as shown in FIG.
One mechanical relay 33 installed on each surface of the unit substrate U controls on / off of a wiring for applying a high voltage to the semiconductor radiation detector 21 included on each surface.

(Unit board)
As shown in FIG. 5, the unit substrate U has an annular support provided in the PET imaging apparatus 1 such that the surface on which the semiconductor radiation detector 21 is installed faces in the depth direction (Z direction) of the PET imaging apparatus 1. Installed on a member (not shown). The plurality of unit substrates U installed on the annular member are arranged in the circumferential direction and surround the measurement space 1a. And it arrange | positions so that detection area | region 20A may be located inside (measurement space 1a side) and ASIC area | region 20B may be located outside. In the present embodiment, the plurality of unit substrates U are also arranged in the depth direction of the PET imaging apparatus 1.

  The detailed structure of the unit substrate U will be described with reference to FIGS. The unit substrate U includes a detection area 20A in which a plurality of semiconductor radiation detectors 21 are installed as described above, and an ASIC area 20B. The ASIC area 20 </ b> B includes a mechanical relay 33, a resistor 41, a capacitor 43, an analog ASIC 28, and a digital ASIC 29. The γ-ray detection signal output from each semiconductor radiation detector 21 is supplied from the detection region 20A side to the ASIC region 20B side by a multilayer wiring (not shown) in the wiring board 20.

  In the ASIC area 20B, as shown in FIGS. 6A and 6B, one digital ASIC 29 is installed on one side and four analog ASICs 28 are arranged on both sides. On both surfaces of the ASIC region 20B, resistors 41 and capacitors 43 are installed in a number corresponding to the number of semiconductor radiation detectors 21.

A plurality of connection wirings (not shown) for electrically connecting the resistor 41, the capacitor 43, the analog ASIC 28, and the digital ASIC 29 are provided in the ASIC region 20B. The analog ASIC 28 means an application specific integrated circuit (ASIC) that processes an analog signal (γ-ray detection signal) output from the semiconductor radiation detector 21, and is an LSI (Large Scale Integrated Circuit) of the LSI. It is a kind. The analog ASIC 28 is provided with a signal processing circuit for each semiconductor radiation detector 21. These signal processing circuits are adapted to obtain a γ-ray peak value by inputting a γ-ray detection signal (radiation detection signal) output from one corresponding semiconductor radiation detector 21.
Incidentally, the analog ASIC 28 is a fast system signal processing circuit including the preamplifier 45 in FIG.

  It is preferable that the circuit length and the length (distance) of the wiring for transmitting the γ-ray detection signal are short because the electrostatic capacity is small and the influence of noise is small. Therefore, in the present embodiment, the semiconductor radiation detector 21, the capacitor 43, the resistor 41, the analog ASIC 28, and the digital ASIC 29 are arranged in this order on the unit substrate U from the central axis toward the outside in the radial direction of the PET imaging apparatus 1. It is arranged. With this configuration, the length (distance) of the wiring that transmits the weak γ-ray detection signal output from the semiconductor radiation detector 21 to the amplifier of the analog ASIC 28 can be shortened. For this reason, the influence of noise on the detection signal of γ rays is reduced.

  The cathode electrode C side of the semiconductor radiation detector 21 is connected to a detection circuit 40 (see FIG. 2). The detection circuit 40 includes a resistor 41, a capacitor 43, and an analog ASIC 28, and detects a current that flows when radiation enters the semiconductor radiation detector 21.

(Function and effect)
Incidentally, as described above, the radiation detection signal (charge signal) output from the semiconductor radiation detector 21 is output to the conductive member 22 from the cathode electrode C side via the conductive adhesive 24. Since the radiation detection signal is a high-frequency signal of 10 MHz or more, if there is a portion with poor conductivity in the conductive adhesive 24, distortion occurs when the detection signal passes through the portion, which is a noise. Will appear as degradation of characteristics equivalent to an increase in.

Next, in the semiconductor radiation detector 21 having the multilayer structure as shown in FIG. 1, the influence when the conductivity of a part of the conductive adhesive 24 is lowered will be described with reference to FIG.
FIG. 7 is a graph showing the count for each channel of the energy window by analyzing the pulse height of the radiation detection signal, showing the channel number of the energy window on the horizontal axis, and the larger the number, the energy of the detected γ rays indicated by the radiation detection signal. Indicates that the value is large, and the vertical axis represents the count for each energy window.
This figure is for 662 keV γ-rays emitted from Cs137 (Cesium 137) and shows a count distribution showing sharp peaks for γ-rays of a single energy, as originally shown by curve 92. It is.

However, if the conductivity of the conductive adhesive 24 between a certain semiconductor radiation detection element 211 and the conductive members 22 and 23 is deteriorated, a high resistance is exhibited, and γ rays having the same energy are incident. The peak value of the radiation detection signal differs from the radiation detection signal (charge signal) from the other semiconductor radiation detection element 211. That is, the radiation detection signal (charge signal) from the semiconductor radiation detection element 211 exhibiting high resistance decreases and reaches the preamplifier 45. Then, as shown by a curve 91 in FIG. 7, the distribution of the radiation detection signal from the semiconductor radiation detection element 211 in which the conductivity of the conductive adhesive 24 is deteriorated is a distribution located at the numbered channel having a low peak position. The distribution of the radiation detection signal from the semiconductor radiation detection element 211 having good conductivity of the conductive adhesive 24 shows the distribution located at the channel with the highest peak position, and the two peaks are overlapped. With a distribution.
Obtaining a distribution in which the peak is divided into two in this way means that the energy discrimination ability of γ rays has decreased.

In the radiation measurement circuit 100 shown in FIG. 2, the voltage from the high voltage power supply 27 is changed to a predetermined second high voltage by the voltage adjusting means 31 with respect to the semiconductor radiation detector 21 as shown by the curve 91 in FIG. When the mechanical relay 33 was set and turned on from the off state, the curve returned to a curve showing a good single peak as shown by the curve 92 in FIG. 7 in the subsequent radiation measurement state.
The mechanical relay 33 is a normal electromagnetic switch and can be easily obtained at a low price.

  Note that the number of mechanical relays 33 provided on the unit substrate U is not limited to one on each surface, and more mechanical relays 33 may be provided. In addition, the control means 30 provided in the casing (not shown) does not need to synchronize the mechanical relay 33 on the unit board U stored in the casing as described above and performs the on / off operation in synchronization with each other. Thus, it is desirable to reduce the burden on the high voltage power supply 27 and the voltage adjusting means 31 due to the on / off operation of the mechanical relay 33.

The effects obtained in this embodiment will be described below.
(1) Since the control means 30 and the mechanical relay 33 are provided so that a current larger than the current due to the charge generated when γ-rays (radiation) is incident flows through the conductive adhesive 24, The large current that flows when the mechanical relay 33 is turned on can recombine the conductive particles of the conductive adhesive 24 or destroy the oxide film formed on the conductive adhesive 24. The conductivity of the conductive adhesive 24 can be stabilized.
Further, when conducting the conduction recovery work of the conductive adhesive 24, the preamplifier 45 can be prevented from being damaged because the second high voltage is lower than that in the case of radiation measurement.
(2) A nuclear medicine diagnostic apparatus excellent in energy resolution can be obtained with the minimum additional configuration in which the mechanical relay 33 is provided on the wiring board 20 of the unit board U.
(3) A second high voltage by the mechanical relay 33, for example, a high voltage of about 100V to 200V, is nano-ranged in the semiconductor radiation detector 21 under the control of the control means 30 before applying a voltage for radiation measurement periodically. By multiplying by the second order, the occurrence of failure of the semiconductor radiation detector 21 can be effectively suppressed, and the radiation detection performance can be maintained over a long period of time.
(4) Since the conductivity of the conductive adhesive 24 can be maintained, the semiconductor radiation detection element 211 can be formed thinner and stacked, and both the performance and sensitivity of the semiconductor radiation detector 21 can be improved. It becomes possible to make it. In the PET imaging apparatus 1, it is necessary to efficiently capture 511 keV γ-rays. For this purpose, the semiconductor radiation detection element 211 must be thickened. However, if the semiconductor radiation detection element 211 is thickened, the moving distance of electrons and holes becomes long, so that the energy resolution and the recognition accuracy of the incident time are deteriorated. If a large number of thin semiconductor radiation detection elements 211 can be stacked, the movement distance of electrons and holes can be shortened, so that the energy resolution and the recognition accuracy of the incident time can be improved. There is an advantage that the volume of the container 21 can be increased, and the performance of the PET imaging apparatus 1 can be improved.
(5) Since the semiconductor radiation detector 21 is disposed so that the cathode electrodes C or the anode electrodes A of the semiconductor radiation detection elements 211 adjacent to each other face each other, the conductive members 22 and 23 can be shared. In addition, since the conductivity of the conductive adhesive 24 can be maintained, a reverse bias voltage for collecting charges can be applied between the cathode electrode C and the anode electrode A in a stable state.
Further, it is not necessary to arrange an electrical insulating material between the semiconductor radiation detection elements 211, and a dense arrangement of the semiconductor radiation detection elements 211 can be realized. Thereby, the sensitivity is improved and the inspection time can be shortened.

<< Second Embodiment >>
Next, a PET apparatus according to a second embodiment of the present invention will be described with reference to FIGS. 1, 4 to 6, and 8.
FIG. 8 is a schematic diagram for explaining the principle for explaining the configuration and operation of the radiation measurement circuit applied to the PET apparatus according to the second embodiment.
In the PET apparatus 10 of the present embodiment, the first embodiment and the radiation measurement circuit 100 are simply replaced with the radiation measurement circuit 100A shown in FIG. 8, and the other configurations are the same as those of the first embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.
The radiation measurement circuit 100A in the second embodiment is different from the radiation measurement circuit 100 in the first embodiment in that the connection point between the resistor 41 (resistance value R1, for example, about 100 MΩ) of the signal line SC and the capacitor The capacitor (second capacitor) 44 is disposed between the first capacitor 43 and the first capacitor. The capacitance C1 (first capacitance) of the capacitor 43 is, for example, about 1000 pF, while the capacitance C2 (second capacitance) of the capacitor 44 is, for example, 10000 pF and the static capacitance of the capacitor 43. It is assumed that it is sufficiently larger than the capacitance C1.

  Similarly to the first embodiment, the two protection diodes 48 and 48 are damaged when the voltage generated by an excessive current at the time of the conduction recovery work of the conductive adhesive 24 is applied to the preamplifier 45. The protection circuit 49 is configured so that the mechanical relay 33 is turned on from the off state in the state where the second high voltage is applied to the mechanical relay 33 and vice versa. It plays a role of flowing a reverse current between the ground side and the relay 33 when the relay 33 is turned off.

The difference from the first embodiment is that since the capacitor 44 is provided, the potential of the protection diode 48 is always kept at 0V in terms of DC. Therefore, even when a large potential difference occurs in the resistor 41 when the leakage current in a high temperature environment or the like increases, the protection diode 48 operates and noise does not enter the signal line SC.
The radiation detection signal (charge signal) passes through the capacitor 44 as it is as an AC operation and is transmitted to the capacitor 43 because the capacitance C2 of the capacitor 44 is 10,000 pF and sufficiently large with respect to the capacitance C1 of the capacitor 43. Therefore, the capacitor 44 does not adversely affect the radiation detection signal.

As described above, according to the second embodiment, in addition to the effects described in the first embodiment, the capacitor 43 and the preamplifier 45 are damaged during the continuity recovery work than the radiation measurement circuit 100 in the first embodiment. The possibility of making it low can be reduced.
In some cases, even if the second high voltage described above is set to the same voltage as the first high voltage, it is possible to prevent the capacitor 43 and the preamplifier 45 from being applied with a high voltage. The conduction recovery work can be performed without any problem on soundness. As a result, the program of the control means 30 can be simplified.

Although the mechanical relay 33 is used in the first embodiment and the second embodiment, it is not limited to this. A semiconductor switch that can withstand a high voltage applied to the semiconductor radiation detector 21 and can pass a current of several milliamperes on the order of nanoseconds may be used.
In the first embodiment and the second embodiment, the semiconductor radiation detector 21 has the multilayer structure of the semiconductor radiation detection element 211 as shown in FIG. 1, but is not limited thereto. . A single semiconductor radiation detection element 211 may be used as the single semiconductor radiation detector 21.
Further, the conductive members 22 and 23 have a flat plate shape as shown in FIG. 1, but the planar shape is not limited to that shown in FIG. 1, and a part thereof is cut off to absorb γ rays. A planar shape that reduces the area may be used.

  The present invention is suitable for a PET apparatus, a SPECT apparatus, and a gamma camera that use cadmium telluride or zinc cadmium telluride as the semiconductor radiation detector 21. In these nuclear medicine diagnostic apparatuses, since a radiopharmaceutical is administered to the measurement subject, it is not allowed to break down on the way. That is, since failures due to the measurement system can be reduced, a part of the semiconductor radiation detector 21 cannot be used during the use of the apparatus, the quality of the diagnostic image is deteriorated, or the apparatus cannot be operated. Can be prevented in advance. As a result, reliability as a nuclear medicine diagnostic apparatus can be improved.

It is a perspective view of one example of the semiconductor radiation detector in a 1st embodiment, (a) is a schematic perspective view of a semiconductor radiation detection element of a unit which constitutes a semiconductor radiation detector, and (b) is a semiconductor. It is a perspective view of the semiconductor radiation detector comprised by laminating | stacking multiple radiation detection elements, (c) is the figure which showed typically the state which installed the semiconductor radiation detector in the wiring board. It is a schematic diagram for the principle explanation for explaining the composition and operation of the radiation measurement circuit applied to the PET device according to the first embodiment. It is a figure explaining the structure of the radiation measurement circuit of a comparative example. It is the perspective view which showed typically the structure of PET apparatus suitable as a nuclear medicine diagnostic apparatus of 1st Embodiment. It is the perspective view which showed the PET imaging device typically. (A) is a front view of the unit board | substrate used for the PET imaging device shown in FIG. 5, (b) is a side view of a unit board | substrate similarly. It is the graph which showed the count for every channel of an energy window by analyzing the pulse height of the radiation detection signal. It is a schematic diagram for the principle explanation for demonstrating the structure and effect | action of a radiation measurement circuit applied to the PET apparatus which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 PET imaging device 1a Measurement space 2 Data processing device 3 Console 3a Display device 3b Operation device 10 PET device 20 Wiring board 20A Detector region 20B ASIC region 21 Semiconductor radiation detector (crystal element assembly)
22 Conductive member (the other conductive member)
23 Conductive member (One conductive member)
24 conductive adhesive 27 high voltage power supply 30 control means 31 voltage adjustment means 33 mechanical relay (relay switch)
40, 40A detection circuit 41 resistor 43 capacitor (first capacitor)
44 Capacitor (second capacitor)
45 Preamplifier
48 Protection diode (diode)
49 Protection circuit 100, 100A Radiation measurement circuit 211 Semiconductor radiation detection element A Anode electrode (conductive thin film)
AP, CP wiring C cathode electrode (conductive thin film)
H Subject S Semiconductor element (crystal element)
SC signal line U Unit board

Claims (7)

For the conductive thin film formed on the surface of the crystal element which is a functional element, two conductive members for electrical connection with the outside are provided, and a conductive adhesive composed of conductive particles and a binder is used. The conductive thin film and the conductive member are bonded to form a crystal element assembly, and a charge generated when radiation is incident on the crystal element assembly is used as a signal through the conductive adhesive and the conductive member. A semiconductor radiation detector to be extracted;
An amplifier for amplifying and shaping the signal from the semiconductor radiation detector;
A high voltage power supply for supplying a high voltage to one of the conductive members of the crystal element assembly;
A voltage adjusting means interposed between the high voltage power supply and the one conductive member, and setting a voltage supplied from the high voltage power supply to a predetermined first high voltage in a radiation measurement state;
In a radiation measurement circuit comprising:
Furthermore,
A relay switch arranged at a subsequent stage of the voltage adjusting means;
Control means for controlling the voltage adjusting means and the relay switch;
With
The control means includes
In the voltage adjusting means, the high voltage from the high voltage power source is set to a predetermined second high voltage equal to or lower than the first high voltage for the conduction recovery operation of the conductive adhesive,
In the relay switch, on / off operation,
A radiation measuring circuit for performing conduction recovery work of the conductive adhesive of the semiconductor radiation detector. Furthermore,
A first capacitor having a predetermined first capacitance connected to the amplifier of a signal line connected to the other conductive member of the crystal element assembly and extracted as the signal;
A second capacitor having a predetermined second capacitance that is sufficiently larger than the first capacitance disposed on the semiconductor radiation detector side in series with the first capacitor of the signal line. When,
A protection circuit that is grounded via a diode from a connection point of the signal line between the first capacitor and the second capacitor;
The radiation measurement circuit according to claim 1, further comprising: For the conductive thin film formed on the surface of the crystal element which is a functional element, two conductive members for electrical connection with the outside are provided, and a conductive adhesive composed of conductive particles and a binder is used. The conductive thin film and the conductive member are bonded to form a crystal element assembly, and a charge generated when radiation is incident on the crystal element assembly is used as a signal through the conductive adhesive and the conductive member. A semiconductor radiation detector to be extracted;
An amplifier for amplifying and shaping the signal from the semiconductor radiation detector;
A high voltage power supply for supplying a high voltage to one of the conductive members of the crystal element assembly;
A voltage adjusting means interposed between the high voltage power supply and the one conductive member, and setting a voltage supplied from the high voltage power supply to a predetermined high voltage;
In a radiation measurement circuit comprising:
Furthermore,
A relay switch arranged at a subsequent stage of the voltage adjusting means;
Control means for controlling the voltage adjusting means and the relay switch;
A first capacitor having a predetermined first capacitance connected to the amplifier of a signal line connected to the other conductive member of the crystal element assembly and extracted as the signal;
A second capacitor having a predetermined second capacitance sufficiently larger than the first capacitance disposed on the signal line closer to the semiconductor radiation detector than the first capacitor;
A protection circuit for grounding via a protection diode from an intermediate connection point of the signal line between the first capacitor and the second capacitor;
With
The control means includes
In the voltage adjusting means, the predetermined high voltage is set,
In the relay switch, on / off operation,
A radiation measuring circuit for performing conduction recovery work of the conductive adhesive of the semiconductor radiation detector.   The radiation measurement circuit according to any one of claims 1 to 3, wherein the relay switch is configured by a mechanical relay. For the conductive thin film formed on the surface of the crystal element which is a functional element, two conductive members for electrical connection with the outside are provided, and a conductive adhesive composed of conductive particles and a binder is used. The conductive thin film and the conductive member are bonded to form a crystal element assembly, and a charge generated when radiation is incident on the crystal element assembly is used as a signal via the conductive adhesive and the conductive member. A semiconductor radiation detector to be extracted;
An amplifier for amplifying and shaping the signal from the semiconductor radiation detector;
A high voltage power supply for supplying a high voltage to one of the conductive members of the crystal element assembly;
A voltage adjusting means interposed between the high voltage power supply and the one conductive member, and setting a voltage supplied from the high voltage power supply to a predetermined first high voltage in a radiation measurement state;
In a radiation measurement circuit comprising:
Furthermore,
A semiconductor switch arranged at a subsequent stage of the voltage adjusting means;
Control means for controlling the voltage adjusting means and the semiconductor switch;
With
The control means includes
In the voltage adjusting means, the high voltage from the high voltage power source is set to a predetermined second high voltage equal to or lower than the first high voltage for the conduction recovery operation of the conductive adhesive,
In the semiconductor switch, an on / off operation is performed,
A radiation measuring circuit for performing conduction recovery work of the conductive adhesive of the semiconductor radiation detector. Furthermore,
A first capacitor having a predetermined first capacitance connected to the amplifier of a signal line connected to the other conductive member of the crystal element assembly and extracted as the signal;
A second capacitor having a predetermined second capacitance that is sufficiently larger than the first capacitance disposed on the semiconductor radiation detector side in series with the first capacitor of the signal line. When,
A protection circuit that is grounded via a diode from a connection point of the signal line between the first capacitor and the second capacitor;
The radiation measurement circuit according to claim 5, further comprising:   A nuclear medicine diagnosis apparatus using the radiation measurement circuit according to any one of claims 1 to 6.

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