JP3127930B2 - Semiconductor radiation position detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nuclear medicine diagnostic apparatus such as a gamma camera, a single photon emission CT (computer tomography) apparatus, a positron emission CT apparatus, and a medical diagnostic apparatus such as an X-ray CT apparatus and an X-ray imaging apparatus. And a semiconductor radiation position detecting device used in the field of science and engineering.

[0002]

2. Description of the Related Art Conventionally, a semiconductor radiation detector is used which calculates a radiation incident position from each output in the row and column directions using a semiconductor detector in which a plurality of semiconductor radiation detection elements made of mercury iodide single crystal or the like are arranged in a matrix. Position detection devices are known (U.S. Pat. No. 4,727,256).

[0003]

However, in the semiconductor radiation position detecting device, a high-sensitivity charge-sensitive preamplifier is used for a signal extracting portion of the semiconductor detector. Therefore, when the detector portion vibrates, the input terminal of the preamplifier is used. There is a problem that a circuit noise called microphonic noise is generated due to a change in stray capacitance between the antenna and the container, and the radiation position calculation circuit may mistakenly operate as a radiation detection signal and malfunction.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor radiation position detecting device which has a simple structure and can almost ideally eliminate the possibility of malfunction due to vibration.

[0005]

According to the present invention, there is provided a semiconductor radiation detecting element, a preamplifier for amplifying an output of the semiconductor radiation detecting element, and a waveform to which the output of the preamplifier is inputted. In a semiconductor radiation position detection device including a shaping circuit and a discriminator, and a position calculation circuit to which the outputs of the waveform shaping circuit and the discriminator are input, vibration detection means is provided. As the vibration detection means, A second preamplifier connected via a capacitor, a discriminator to which the output of the second preamplifier is input, and a one-shot circuit are used, and the capacitor has a capacity substantially equal to that of the semiconductor radiation detecting element. A capacitor and a second preamplifier, the semiconductor radiation detecting element and the preamplifier; Shall be provided on the same substrate, further providing a control circuit to temporarily stop the operation of the position calculation circuit described above in accordance with an output from the discriminators and the one-shot circuit has become a feature. The signal system for detecting radiation and the signal system for detecting vibration have almost the same configuration, and a capacitor and a second preamplifier are provided on the same substrate as the semiconductor radiation detecting element and the preamplifier. Since the capacitance is substantially equal to the semiconductor radiation detection element,
These frequency characteristics can be matched, so that the noise based on the vibration obtained from the signal system for vibration detection can be made almost ideally close to the noise generated in the radiation detection system due to the vibration. Erroneous operation can be prevented except for the influence of the above. Moreover, the signal system for detecting vibration has almost the same configuration as the signal system for detecting radiation, and the capacitor for detecting vibration and the second preamplifier are provided on the same substrate as the semiconductor radiation detecting element and the preamplifier. Since it is not necessary to provide each direction, the configuration is simple.

[0006]

An embodiment of the present invention will be described below in detail with reference to the drawings. In FIG. 1, the detector unit 1
Is a matrix in each row and each column (4 × 4 in this embodiment).
The semiconductor radiation detecting elements 2 arranged in
The outputs (4 channels in this case) of each row (rows arranged in the X direction) of these semiconductor radiation detecting elements 2 are input to the preamplifier group 3 in the X direction, and the outputs (4 channels) of each column (columns arranged in the Y direction). Are input to the preamplifier group 4 in the Y direction. An example of the output waveform of each channel from the preamplifier group 3 is shown in FIG. The same applies to the preamplifier group 4.
These row outputs and column outputs are sent to the position calculation circuit 9 through the waveform shaping circuit and the discriminator 5, and the position signals X and Y in the X and Y directions are obtained. When one or more channels in the X direction and one or more channels in the Y direction of the discriminator simultaneously output pulse signals within a predetermined time, the OR circuit and the simultaneous detection circuit 6 as shown in FIG. A trigger pulse is generated and sent to the timing circuit 8 via the AND gate circuit 7, and the operation of the timing circuit 8 starts. The output of each of the waveform shaping circuits of the waveform shaping circuit and the discriminator 5 is input to the energy peak analyzer 10 via an analog multiplexer or the like, which is not shown in the drawing. Send a signal to 8. As a result, the timing circuit 8 outputs an UNBLANK signal, and this signal and the above-mentioned position signals X and Y are output from the data collection processing device 11.
And sent to a CRT display device (not shown) to display the position of the radiation event.

The detector section 1 is provided with a vibration detecting element such as a piezoelectric vibration sensor and an amplifier 21 in the vicinity of the radiation detecting element 2 and the preamplifier groups 3 and 4, and the output thereof is a discriminator and an amplifier. The signal is sent to the one-shot circuit 23 and compared with the reference voltage level L from the reference voltage circuit 22. When vibration occurs, the output of the vibration detecting element and the amplifier 21 exceeds the reference voltage level L as shown in FIG. 2, and a pulse signal is generated from the discriminator and one-shot circuit 23 as shown in FIG. . This one-shot circuit preferably has a so-called retriggerable configuration in which when the input again exceeds the reference voltage level L during generation of the pulse signal, the trigger is triggered again and the pulse width is extended. This pulse signal is output from the inverting circuit 24.
The output of the OR circuit and the simultaneous detection circuit 6 is transmitted to the timing circuit 8 through the gate circuit 7 while the pulse signal is generated, as shown in FIG. Is prevented. In this case, it is desirable to provide the vibration detecting element and the amplifier 21 for each of the vibration directions of the X direction, the Y direction, and the Z direction, and it is also desirable to consider the frequency characteristics. Note that this gate circuit 7
The two signal systems before entering, namely, the preamplifier group 3,
4. Waveform shaping circuit and discriminator 5, signal system of OR circuit and simultaneous detection circuit 6, vibration detection element and amplifier 21, discriminator and one-shot circuit 2
3. A delay circuit or the like is inserted into one of the signal systems of the inverting circuit 24 to adjust the timing of both.

The output of the discriminator and one-shot circuit 23 is sent to the gate circuit 26 to gate the output from the oscillation circuit 25. As a result, while the gate circuit 7 is closed by the vibration, the gate circuit 26 is opened and the output of the oscillation circuit 25 is sent to the counter 27. Therefore, the counter 27 obtains a count value corresponding to the total time during which the gate circuit 7 is closed. The information on the total time during which the gate circuit 7 was closed is taken into the data collection processing device 11, and the time from when the gate circuit 7 was closed due to vibration detection and data could not be collected from the time actually required for data collection. By subtracting the sum, the net data collection time can be obtained.

FIG. 3 shows a second embodiment. Since the configuration is almost the same as that of FIG. 1, the same parts are denoted by the same reference numerals, and description thereof will be omitted. Only different parts will be described. . In FIG. 3, the vibration detecting element and the amplifier 2 of FIG.
A preamplifier 31 is provided instead of 1, and this output is sent to a discriminator and one-shot circuit 33 to be compared with a reference voltage level L 'from a reference voltage circuit 32. The preamplifier 31 is similar to each of the preamplifiers included in the preamplifier groups 3 and 4, and is provided near the radiation detection element 2 and the preamplifier groups 3 and 4, for example, on the same substrate. When the output of the preamplifier 31 exceeds the reference voltage level L 'as shown in FIG. 4, a pulse signal is generated from the discriminator and one-shot circuit 33, and the gate circuit 7 is closed.

The preamplifier 31 is, for example, shown in FIG.
Are connected as follows. FIG. 5 shows an example of a DC connection type preamplifier, and FIG. 6 shows an example of an AC connection type preamplifier. FIG.
Since one preamplifier 3 ′ in the preamplifier group 3 is connected to the bias voltage Vb via the radiation detection element 2 and the filter circuit 50,
A preamplifier 31 is connected to one end of the filter circuit 50 via a capacitor 30 corresponding to. In FIG. 6, one preamplifier 4 ′ in the preamplifier group 4 is A
The radiation detection element 2 is connected to one end of the radiation detection element 2 via a C-coupling capacitor 52, and one end of the radiation detection element 2 is supplied with a bias voltage Vb via a filter circuit 50 and a bias resistor 51. Therefore, similarly, a preamplifier 31 is connected to a connection point between the capacitor 30 corresponding to the radiation detection element 2 and the bias resistor 61 via an AC coupling capacitor 62.

Microphonic noise due to vibration is
This is because the stray capacitance between the radiation detecting element 2 and the input terminals of the preamplifiers 3 ′ and 4 ′ and the container changes due to vibration, and a noise current is generated by coupling with the bias voltage Vb. Therefore, as described above, the capacitor 30 having the same capacity as that of the radiation detection element 2 and having sufficiently low radiation sensitivity compared to the radiation detection element 2 is connected, and also coupled to the bias voltage Vb. By doing so, exactly the same noise as the microphonic noise generated from the preamplifiers 3 ′ and 4 ′ can be ideally obtained from the preamplifier 31.

Here, the discriminator and one-shot circuit 33 includes a waveform shaping circuit and the discriminator 5.
If the reference voltage level L relating to the former is lower than the threshold level of the latter,
This is desirable because malfunction due to noise can be completely prevented. Thus, the radiation detecting element 2, the preamplifier groups 3, 4, the waveform shaping circuit, and the discriminator 5
By configuring the signal system for detecting the radiation of the above and the signal system for detecting the vibration of the preamplifier 31, the discriminator and the one-shot circuit 33 almost the same, their frequency characteristics can be matched, It is not necessary to provide the preamplifier 31 for each vibration direction.

The present invention can be variously modified without departing from the gist thereof. For example, in the examples shown in FIGS.
Alternatively, the output of the inverting circuit 24 may be input to the gate circuit 26 instead of the output of 3, and the counter 27 may obtain information on the net data collection time.
In addition, the present invention is applicable to a two-dimensional radiation position detecting device having another configuration, a one-dimensional and three-dimensional radiation position detecting device, and a ring-shaped radiation detector such as a single photon emission CT device or a positron emission CT device. The present invention can also be applied to a radiation position detecting device arranged in the following manner. Further, in each of the above examples, the position is detected for each radiation event as in a gamma camera, but the present invention can also be applied to the case where a radiation event signal is integrated as in an X-ray CT apparatus or an X-ray imaging apparatus. In addition, the radiation detecting element 2 can be applied to a type in which a scintillator and a semiconductor photodiode are combined.

[0014]

As described above, according to the embodiment,
According to the semiconductor radiation position detecting device of the present invention, when there is a possibility that noise may occur due to vibration and malfunction, the noise due to the vibration can be captured almost ideally, and the malfunction can be surely prevented. Therefore, even if the radiation detection unit moves during data acquisition, such as rotation for the emission CT of a gamma camera or whole body scan, image quality degradation such as reduced spatial resolution and uniformity may occur. Disappears. Moreover, the signal system for detecting vibration may have almost the same configuration as the signal system for detecting radiation, and the capacitor for detecting vibration and the second preamplifier may be mounted on the same substrate as the semiconductor radiation detecting element and the preamplifier. Since it is only necessary to provide it and it is not necessary to provide it for each direction, the configuration is simple.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a time chart for explaining the operation.

FIG. 3 is a block diagram of a second embodiment of the present invention.

FIG. 4 is a time chart for explaining the operation.

FIG. 5 is a circuit diagram of a specific example of a part of FIG. 3;

FIG. 6 is a circuit diagram of another specific example of a part of FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Radiation detector part 2 Radiation detection element 3, 4 Preamplifier group 5 Waveform shaping circuit and discriminator 6 OR circuit and simultaneous detection circuit 7, 26 Gate circuit 8 Timing circuit 9 Position calculation circuit 10 Energy wave height analyzer 11 Data collection processing Apparatus 21 Vibration detecting element and amplifier 22, 32 Reference voltage circuit 23, 33 Discriminator and one-shot circuit 24 Inverting circuit 25 Oscillator 27 Counter 3 ', 4', 31 Preamplifier 30 Capacitor 50 Filter circuit 51, 61 Bias resistor 52 , 62 AC coupling capacitor

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01T 1/24 G01T 1/161

Claims (1)

(57) [Claims] 1. A semiconductor radiation detecting element, a preamplifier for amplifying an output of the semiconductor radiation detecting element, a waveform shaping circuit and a discriminator to which an output of the preamplifier is input, and outputs of the waveform shaping circuit and the discriminator Is input to the position calculation circuit and the semiconductor radiation detecting element and the preamplifier are provided on the same substrate as the semiconductor radiation detecting element, and are connected in parallel with the semiconductor radiation detecting element via a capacitor having substantially the same capacitance as the element. The connected second preamplifier, the discriminator and the one-shot circuit to which the output of the second preamplifier is input, and the operation of the position calculation circuit according to the output from the discriminator and the one-shot circuit And a control circuit for temporarily stopping the semiconductor radiation position detecting device.