JP4326613B2 - Radiation detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiation detection apparatus used as a radioisotope imaging apparatus or the like.
[0002]
[Prior art]
Conventionally, as a radioisotope (RI: Radioisotope) imaging device such as biological imaging using a radioactive tracer, a single photon emission tomography device (SPECT: Single Photon Emission Computed) using a gamma camera is applied. Tomography) is used in the field of nuclear medicine.
[0003]
[Problems to be solved by the invention]
In the above-described radiation detection apparatus such as a gamma camera or SPECT, the basic performance and characteristics such as the field of view, the position resolution, and the count rate characteristic are almost fixed to each apparatus. On the other hand, practically, when it is necessary to select the optimal field of view and position resolution according to the object to be measured, and after measuring the entire field of view (large field of view), a part of the field of interest (small field of view) It may be necessary to switch these characteristics when it is desired to perform measurement with high resolution.
[0004]
Here, for such switching, in order to change the field of view and the position resolution in the same apparatus, a method such as changing the collimator used for measurement can be considered. However, when such switching is performed, it is necessary to prepare a plurality of expensive collimators, and there is a problem that a degree of freedom for selecting an optimal collimator for a measurement target cannot be secured. In addition, since switching by such a method involves a change in the apparatus configuration, it cannot be easily performed, and in particular, there is a problem that it is difficult to change or switch in a short time during measurement. .
[0005]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a radiation detection apparatus capable of easily changing the visual field, position resolution, and the like.
[0006]
[Means for Solving the Problems]
In order to achieve such an object, a radiation detection apparatus according to the present invention includes a radiation detection module including a scintillator that emits fluorescence by incident radiation, and a position detection type photomultiplier that detects fluorescence from the scintillator. formed by arranging a plurality array, detection signals from a plurality of output terminals having a radiation detecting means configured as a full field of view in a predetermined field of view measurable region, a plurality of radiation detection modules respectively are input From the signal selection circuit that sets a part or all of the entire visual field as the measurement visual field by setting the connection between the output terminals and to the external output and selecting the output signal to the outside. The position detection circuit that detects the incident position of radiation in the measurement field and the position input from the position detection circuit A data processing circuit for collecting over data, retrieve data from the data processing circuit, and a selection control signal and control means for controlling the performing of the signal selection circuit according to a position-sensitive photomultiplier tube of the radiation detector module A plurality of anodes, a resistance divider circuit connected via a resistor having a predetermined resistance value, and a plurality of outputs connected to the ends of the resistor divider circuit, while receiving signals from the plurality of anodes A multi-anode type photomultiplier tube having a terminal, and a signal selection circuit is provided for a plurality of radiation detection modules and switches connection between output terminals of two adjacent radiation detection modules. A connection switch for switching a combination that functions as an integrated radiation detection module, and a plurality of radiation detection modules. 1st selection switch circuit which selects the output signal of the one end side used for a position detection by turning on either of the several switch to which those inputs were connected by the signal from the output terminal of the side being input In addition, the signals from the output terminals on the other end side of each of the plurality of radiation detection modules are input, and one of the plurality of switches to which those inputs are connected is turned on, so that the other is used for position detection. A second selection switch circuit for selecting an output signal on the end side, and the control means turns on / off the connection switch and turns on / off each of the plurality of switches in the first selection switch circuit according to the selection control signal. , and to control the respective ON / OFF of the plurality of switches of the second selection switch circuit and said Rukoto.
[0007]
In the above-described apparatus, radiation detection is performed by a plurality of radiation detection modules arranged in a predetermined shape and configuration such as a two-dimensional matrix, each of which is a two-dimensional position detection type. The position detection type photomultiplier tube has a plurality of output terminals, and detects the incident position of radiation by the correlation of detection signals output from them. In such a configuration, radiation detection used for detection in a single detection device by setting or switching the connection between output terminals of each radiation detection module and selection of an output signal used for position detection by a signal selection circuit. It is possible to select the modules and their combinations, set the measurement field of view, and switch the field of view and position resolution only by controlling the circuit without changing the device configuration.
[0008]
In addition, data acquisition and signal selection are performed by the same control means, whereby both can be set and controlled at the same time to perform efficient measurement.
[0009]
The signal selection circuit is configured to simultaneously set n types of measurement visual fields (where n is an integer of 2 or more) and select an output signal corresponding to each measurement visual field. Output signals corresponding to n types of measurement visual fields are respectively input, and n position detection circuits for detecting incident positions of radiation in the respective measurement visual fields, and position data respectively input from the n position detection circuits. And n data processing circuits for collecting data.
[0010]
In particular, when two or more different fields of view are to be measured at the same time, such as measurements with a large field of view and a small field of view, two or more systems of position detection circuits and data processing circuits are installed as described above, and a signal selection circuit. By connecting the output terminals in the display and selecting the output signals used for position detection, the output signals for the multiple visual fields are respectively selected and output. Simultaneous measurement is possible.
[0011]
Furthermore, the signal selection circuit includes a connection circuit that sets connection between each of the plurality of output terminals of the plurality of radiation detection modules, and a selection circuit that selects an output terminal connected to the external output. Also good.
[0012]
By setting it as the signal selection circuit which consists of such a circuit structure, the setting and switching of a measurement visual field can be implement | achieved efficiently.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a radiation detection apparatus according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings do not necessarily match those described.
[0014]
FIG. 1 is a block diagram showing a configuration of an embodiment of a radiation detection apparatus according to the present invention. The radiation detection unit 1 that detects radiation has the same configuration as that of a conventional gamma camera or the like, and includes a collimator 1b that collimates radiation such as gamma rays that are emitted from a measurement target and incident on a radiation detection apparatus, and a collimator 1b. The radiation detection module array 1a is configured to detect a collimated radiation and to detect a two-dimensional position. As the collimator 1b, one having a configuration corresponding to the shape and configuration of the radiation detection module array 1a to be connected and the required position resolution is selected and used. The radiation detection module array 1a is configured by two-dimensionally arranging a plurality of radiation detection modules 10.
[0015]
Detection signals including incident position information of detected radiation output from the plurality of radiation detection modules 10 constituting the radiation detection module array 1 a are input to the signal selection circuit 2. As will be described later, the signal selection circuit 2 controls and changes the visual field and position resolution of the detection device by performing connection and change between the detection signals and selection of an output signal based on the connection. It is configured to be realized.
[0016]
The output signal selected and output by the signal selection circuit 2 is input to the position detection circuit 3, converted into radiation incident position information and output as position data, and the data processing circuit 4 collects the position data. Is finally input to the computer 5. The computer 5 displays data collected on the connected display device 6 or an analysis result thereof. The computer 5 controls the switching of the visual field and the position resolution by the signal selection circuit 2 in accordance with the selection control signal, thereby executing and controlling the measurement visual field in correspondence with the acquisition and display of data. can do. The computer 5 may have a configuration in which a storage device for storing collected data is connected if necessary. In addition, for example, an input device such as a keyboard can be connected so that the selection control signal and the like can be changed. Further, since the response speed of the position detection circuit 3 is constant, the count rate characteristic of the apparatus is improved when the field of view is small compared to the large field of view.
[0017]
2 is a perspective view showing a configuration of the radiation detection module array 1a used in the present embodiment, and FIG. 3 is an enlarged perspective view of the radiation detection module 10. As shown in FIG. In this embodiment, the radiation detection module array 1a is composed of a plurality of radiation detection modules 10 arranged in an 8 × 8 matrix, and in FIG. Is attached. In addition, each of the radiation detection modules 10 is configured to be capable of detecting a two-dimensional position.
[0018]
The radiation detection module 10 has, for example, a rectangular or square shape when arranged as in the present embodiment, and the upper portion thereof emits fluorescence when incident radiation such as incident gamma rays is incident. A scintillator array 11 composed of a plurality of scintillators 11a arranged in a multi-anode type, such as a multi-anode type position detecting photomultiplier tube 12 is connected to the lower part of the scintillator array 11a. Yes. Detection signals from the position detection type photomultiplier tube 12 are output to the outside from the four output terminals 14. Note that the arrangement of the plurality of scintillators 11a of the scintillator array 11 is illustrated only in the radiation detection module 10 denoted by reference numeral 10 in FIG. Further, the scintillator array 11 does not necessarily have a plurality of scintillators, and may be constituted by a single scintillator.
[0019]
FIG. 4 is a cross-sectional view of the radiation detection module 10 shown in FIG. The scintillator array 11 is composed of a plurality of scintillators 11a, and each scintillator 11a reflects the fluorescence generated by the incidence of radiation into the scintillator 11a and efficiently enters the position detection type photomultiplier tube 12. The side surface and the upper surface are covered with the reflecting material 11b.
[0020]
The position detection type photomultiplier tube 12 installed in the lower part of the scintillator array 11 is a multi-anode type photomultiplier tube in this embodiment. A photocathode 12a to which a scintillator 11a is connected is formed on the upper surface of the position detection type photomultiplier tube 12, and the fluorescence generated in the scintillator 11a by the incidence of radiation enters the photocathode 12a and photoelectrons are produced by the photoelectric effect. Is converted to The photoelectrons emitted from the photocathode 12a are multiplied by the channel type dynode 12b, and the multiplied electron flow finally reaches the anode surface 12c to generate a detection signal. If necessary, a light guide may be installed between the scintillator array 11 and the photocathode 12a.
[0021]
The anode surface 12c is a multi-anode type capable of position detection. In this embodiment, the anode surface 12c is divided into an 8 × 8 matrix, and 8 × 8 anodes 12d each having a rectangular or square shape are arranged. ing. The multiplied electron current reaches these anodes 12d and is input to the resistance dividing circuit 13 via the anode terminal 12e. The signal processed by the resistance dividing circuit 13 is finally output from the four output terminals 14 to the outside.
[0022]
FIG. 5 shows a configuration of the resistance dividing circuit 13. Signals from the 8 × 8 anodes 12d are input to the resistance dividing circuit 13 via 8 × 8 anode terminals 12e, which are shown in the figure via a resistor 13a having a predetermined resistance value. , And finally, detection signals are output from the output terminals 14a to 14d connected to the four ends thereof. Here, when the xy coordinates are set as shown in FIG. 5 and the outputs from the output terminals 14a, 14b, 14c and 14d are a, b, c and d, respectively, the radiation incident positions (x, y) is the gravity center position calculation x = (c + d) / (a + b + c + d)
y = (a + d) / (a + b + c + d)
Can be obtained.
[0023]
Next, the configuration and function of the signal selection circuit 2 according to the present invention for switching the measurement visual field, position resolution, and the like in the radiation detection apparatus shown in FIG. 1 will be described. FIG. 6 is a circuit diagram showing a configuration of the signal selection circuit 2. However, in FIG. 6, for the sake of simplicity, the radiation detection unit 1 is of a one-dimensional position detection type, and therefore, for each radiation detection module, two output terminals corresponding to one-dimensional ends and their connections are shown. However, even in the case of the two-dimensional position detection type, it is possible to easily expand the corresponding one shown in this figure using the same configuration. Further, the collimator 1b is not shown.
[0024]
Here, as the radiation detection module array 1a, eight radiation detection modules 10 ₁ to 10 ₈ arranged one-dimensionally are shown, and each of the radiation detection modules 10 _i (i = 1 to 8) is one-dimensional. It is configured to include a position-sensitive photomultiplier tube 12, the detection signal from the output terminal 14a _i and 14b _i corresponds to a one-dimensional across is output. Note that the above only but are designated by the reference numeral in FIG. Similarly for other radiation detection module 10 _i in the figure for the output terminals 14a ₁ and 14b ₁ of the radiation detection module 10 ₁ located at the top An output terminal is 14a _i , and a lower output terminal is 14b _i .
[0025]
Two adjacent radiation detection modules, for example, radiation detection modules 10 ₁ and 10 ₂ , are connected to each other via a connection switch that is an analog switch, for example, a connection switch 21 ₁ . These connection switches 21 _{1 to} 21 ₇ are controlled to be turned on / off by a selection control signal from the computer 5 via the decoder 210, whereby the connection / combination of the radiation detection modules and the change of the measurement field of view are thereby performed. Is done. Ends that is, for example, when the connection switch 21 ₁ and the ON, radiation detection module 10 ₁ and 10 _2, the radiation detection module 10 ₁ above the output terminals 14a ₁ and the radiation detector module 10 ₂ output terminals 14b ₂ of the lower Functions as an integrated radiation detection module.
[0026]
The signal selection circuit 2 is further provided with selection switch circuits 22 and 24 for selecting a signal to be output to the position detection circuit 3. The selection switch circuit 22, the signal from the output terminal 14a ₁ to 14A ₈ in upward in the drawing of the radiation detector module 10 ₁ to 10 ₈ are input to the respective input analog switch mounted on the selection switch circuit 22 The output signals used for position detection are connected, and the ON / OFF of these eight switches is controlled by the selection control signal from the computer 5 via the decoder 220 and any one of the switches is turned ON. Can be selected. Similarly, the switch circuit 24 selects an output signal used for position detection with respect to the signals from the output terminals 14b _{1 to} 14b ₈ below the radiation detection modules 10 ₁ to 10 _{8 in} the drawing. Output signals from the selection switch circuits 22 and 24 are amplified by the amplifiers 221 and 241, respectively, and then output to the position detection circuit 3.
[0027]
These selection switch circuits 22 and 24 are controlled by a selection control signal in conjunction with the connection switches 21 _{1 to} 21 ₇ described above. For example, the connection switch 21 ₁ is turned on to connect the radiation detection modules 10 ₁ and 10 ₂ , the output signal from 14a ₁ is selected by the selection switch circuit 22, and the output signal from 14b ₂ is selected by the connection switch circuit 24. By selecting, it is possible to perform radiation detection with the region of the radiation detection modules 10 ₁ and 10 ₂ as the measurement field. Similarly, by connecting, selecting, and switching 1 to 8 radiation detection modules and their output signals, the measurement field of view and position resolution can be controlled only by controlling the circuit without changing the configuration of the detection device. Can be selected and switched.
[0028]
As described above, the signal selection circuit 2 connects the plurality of radiation detection modules 10 constituting the radiation detection unit 1 and selects the output signal, so that, for example, the selection / switching of the measurement with the large field and the small field can be performed in a single manner. It is possible with the device. On the other hand, there may be a case where it is desired to perform measurement with a large visual field and a small visual field at the same time. Such measurement can be realized by performing position detection simultaneously using two systems of circuits. FIG. 7 is a block diagram showing the configuration of another embodiment of the radiation detection apparatus according to the present invention having such a configuration. As described above, the position detection is performed using the two systems of the position detection circuit 3a and the data processing circuit 4a, and the position detection circuit 3b and the data processing circuit 4b, so that the above-described large visual field and small visual field can be obtained. It is possible to simultaneously perform measurement in two different measurement fields such as measurement.
[0029]
FIG. 8 is a circuit diagram showing a configuration of the signal selection circuit 2 applied to the embodiment shown in FIG. The configuration of the radiation detection unit 1 and the connection switches 21 _{1 to} 21 ₇ for connecting the output terminals of the radiation detection modules 10 ₁ to 10 ₈ are the same as the circuit shown in FIG. Here, for the sake of easy understanding, connection signal lines between the output terminals and the selection switch circuit are not shown.
[0030]
The signal selection circuit 2 is provided with four selection switch circuits 22 to 25. Of these, the selection switch circuits 22 and 23 have the same configuration and function as the selection switch circuit 22 in FIG. signal from the output terminal 14a ₁ to 14A ₈ in upward in the drawing of the radiation detector module 10 ₁ to 10 ₈ is input. The selection switch circuits 24 and 25 have the same configuration and function as the selection switch circuit 24 in FIG. 6, and signals from the output terminals 14 b _{1 to} 14 b ₈ below the radiation detection modules 10 ₁ to 10 _{8 in} the drawing. Is entered. In such a configuration, output signals from the selection switch circuits 22 and 24 are amplified by the amplifiers 221 and 241, respectively, and then output to the position detection circuit 3a to perform the first position detection. Further, the output signals from the selection switch circuits 23 and 25 are amplified by the amplifiers 231 and 251, respectively, and then output to the position detection circuit 3b to perform the second position detection.
[0031]
The selection switch circuits 22 to 25 and the connection switches 21 _{1 to} 21 ₇ are controlled by the selection control signal from the computer 5 via the decoders 220 to 250 and 210, thereby the first and second position detections described above. The field of view and position resolution can be selected and switched. In FIG. 8, ON / OFF of each switch is set so that the first position detection is a large visual field (full visual field) measurement and the second position detection is a small visual field measurement.
[0032]
That is, all the connection switches 21 _{1 to} 21 ₇ are set to ON, and the radiation detection modules 10 ₁ to 10 ₈ constitute an integral radiation detection module. On the other hand, the signal from the output terminal 14a ₁ is selected as the output signal in the selection switch circuit 22, and the signal from the output terminal 14b ₈ is selected as the output signal in the selection switch circuit 24. The large field of view is measured by the _eight radiation detection modules 10 ₁ to 10 ₈ . On the other hand, a signal from the output terminal 14a ₄ is selected as an output signal in the selection switch circuit 23, and a signal from the output terminal 14b ₄ is selected as an output signal in the selection switch circuit 25. The small field of view is measured by the radiation detection module 10 ₄ . Therefore, the configuration of the signal selection circuit 2 and the connection with the position detection circuits 3a and 3b are used, and the output signal in the signal selection circuit 2 is appropriately selected or switched, so that, for example, measurement in a large visual field and a small visual field is different. It is possible to perform measurement in two measurement fields at the same time.
[0033]
The radiation detection apparatus according to the present invention is not limited to the above-described embodiment, and various modifications can be made. For example, about the structure of the radiation detection part 1, various changes are possible as needed, such as the shape of each radiation detection module and the arrangement method thereof. Also, a position detection type photomultiplier tube other than the multi-anode type may be used. According to the configuration change of the radiation detection unit 1, the signal selection circuit can be configured to have the same function as that of the above-described embodiment. In some cases, switching of the visual field and position resolution by the circuit of the present invention and switching of the visual field and position resolution by a conventional collimator may be used in combination.
[0034]
Further, the simultaneous measurement using a plurality of measurement visual fields is not limited to two visual fields, and it is also possible to configure so that measurements on three or more visual fields can be performed simultaneously.
[0035]
【The invention's effect】
As described in detail above, the radiation detection apparatus according to the present invention achieves the following effects. That is, radiation detection is performed using a plurality of radiation detection modules each including a position detection type photomultiplier tube, and detection signals from the respective output terminals are connected and selection of output signals to the outside is performed by a signal selection circuit. By setting and controlling, it is possible to switch the measurement field of view and position resolution during measurement, or to simultaneously measure multiple measurement fields such as a large field of view and a small field of view without changing the device configuration. it can.
[0036]
As a result, the degree of freedom in optimizing the detection device in accordance with the measurement target is increased, and the optimization can be performed easily and in a short time. For example, in the field of nuclear medicine, the conventional gamma camera, SPECT, etc. In comparison, more accurate diagnosis information can be obtained. In addition, the apparatus can be reduced in size and price.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an embodiment of a radiation detection apparatus according to the present invention.
FIG. 2 is a perspective view showing a configuration of a radiation detection module array applied to the apparatus shown in FIG.
3 is a perspective view showing a radiation detection module constituting the radiation detection module array shown in FIG. 2. FIG.
4 is a cross-sectional view of the radiation detection module shown in FIG. 3;
FIG. 5 is a circuit diagram showing a configuration of a resistance dividing circuit applied to the radiation detection module shown in FIG. 3;
6 is a circuit diagram showing a configuration of a signal selection circuit applied to the apparatus shown in FIG. 1;
FIG. 7 is a block diagram showing a configuration of another embodiment of the radiation detection apparatus according to the present invention.
8 is a circuit diagram showing a configuration of a signal selection circuit applied to the apparatus shown in FIG. 7;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Radiation detection part, 1a ... Radiation detection module array, 1b ... Collimator, 10 ... Radiation detection module, 11 ... Scintillator array, 11a ... Scintillator, 11b ... Reflector, 12 ... Position detection type photomultiplier tube, 12a ... Photoelectric Surface, 12b ... channel type dynode, 12c ... anode surface, 12d ... anode, 12e ... anode terminal, 13 ... resistance dividing circuit, 13a ... resistor, 14, 14a-d ... output terminal,
DESCRIPTION OF SYMBOLS 2 ... Signal selection circuit, 21 ... Connection switch, 210 ... Decoder, 22-25 ... Selection switch circuit, 220-250 ... Decoder, 221-251 ... Amplifier,
3, 3a, 3b ... position detection circuit, 4, 4a, 4b ... data processing circuit, 5 ... computer, 6 ... display device.

Claims (2)

Measures a predetermined field of view by arranging a plurality of radiation detection modules arranged in an array , including a scintillator that emits fluorescence by incident radiation and a position detection type photomultiplier tube that detects the fluorescence from the scintillator Radiation detection means configured as a whole field of view,
Detection signals from a plurality of output terminals respectively included in the plurality of radiation detection modules are input, and the entire visual field is selected by setting connection between the output terminals and to an external output and selecting an output signal to the outside. A signal selection circuit for setting a part or all of the measurement field of view,
A position detection circuit that receives the output signal from the signal selection circuit and detects an incident position of radiation in the measurement field; and
A data processing circuit for collecting position data input from the position detection circuit;
Control means for acquiring data from the data processing circuit and controlling the signal selection circuit by a selection control signal;
Equipped with a,
The position detection type photomultiplier tube of the radiation detection module includes a plurality of anodes, and a resistance divider circuit to which signals from the plurality of anodes are input and connected via a resistor having a predetermined resistance value A multi-anode type photomultiplier tube having the plurality of output terminals connected to an end of the resistance divider circuit;
The signal selection circuit includes:
A connection switch that is provided for a plurality of the radiation detection modules, and switches a combination that functions as an integral radiation detection module by switching ON / OFF between the output terminals of two adjacent radiation detection modules;
A signal from an output terminal on one end side of each of the plurality of radiation detection modules is input, and one of the plurality of switches to which those inputs are connected is turned on, so that one end side used for position detection is turned on. A first selection switch circuit for selecting an output signal;
The other end used for position detection by inputting a signal from an output terminal on the other end side of each of the plurality of radiation detection modules and turning on one of a plurality of switches to which the inputs are connected A second selection switch circuit for selecting a side output signal,
The control means is configured to turn on / off the connection switch, turn on / off each of the plurality of switches in the first selection switch circuit, and use the plurality of switches in the second selection switch circuit according to the selection control signal. radiation detecting apparatus characterized that you control the respective ON / OFF switch. The signal selection circuit is configured to simultaneously set n types of measurement fields (where n is an integer of 2 or more) and select the output signals corresponding to the respective measurement fields.
N position detection circuits that receive the output signals corresponding to the n types of measurement visual fields from the signal selection circuit and detect incident positions of radiation in the respective measurement visual fields;
N data processing circuits that collect position data respectively input from the n position detection circuits;
The radiation detection apparatus according to claim 1, further comprising:

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