JPH0619445B2 - Gamma camera device - Google Patents

Description

The present invention relates to a gamma camera device for creating RI distribution data in a subject administered with a radioisotope (RI), and more particularly to a gamma camera device. The present invention relates to a gamma camera device in which the means for calculating the incident position of radiation is digitized.

(Prior Art) An example of a conventional gamma camera is shown in FIG. That is,
The detector 3 detects gamma rays emitted from the subject 2 to which RI1 has been administered. At this time, an electric signal is output from the output terminal of the photomultiplier tube 4 of the detector 3 according to the incident position of the gamma ray. The peak value of these output electric signals becomes higher as the photomultiplier tube 4 is arranged closer to the gamma ray incident position. The output electric signal from each such photomultiplier tube 4 is amplified by each preamplifier 5 and then supplied to the rough position calculator 6.

As shown in FIG. 4, the schematic position calculator 6 includes a specific coordinate system position calculation circuit 7, a group selection circuit 8 and an absolute coordinate system position calculation circuit 9. As shown in FIG. 6, the specific coordinate system position calculation circuit 7 includes a photomultiplier tube 4 which is divided into L-axis, M-axis and N-axis groups, and the photomultiplier tube having a size larger than a set value for each group. The output signal of the double tube 4 is detected and output as a specific coordinate system position signal. The group selection circuit 8 is a circuit that controls selection of each group in grouping the photomultiplier tubes 4. The absolute coordinate system position calculation circuit 9 uses the specific coordinate system position signal output from the specific coordinate system position calculation circuit 7 for each group and the group selection signal output from the group selection circuit 8 as a rough absolute coordinate system. System position signals Xo, Y
Calculate and output o.

As shown in FIG. 5, the specific coordinate system position calculation circuit 7 has an independent circuit configuration for each group of photomultiplier tubes. Here, the photomultiplier tube 4 has, for example, as shown in FIG. 6, L-axis (L1, L2, ..., Ln) and M-axis (M1, M
2, ..., Mn) and N-axis (N1, N2, ... Nn). Since each group has the same circuit configuration, only the L-axis groove will be described. Each output of the photomultiplier tube is connected to the OR circuit 10, and this output terminal is connected to the A / D converter 11. The output signal thus A / D converted is converted into a specific coordinate system position signal by the comparator 12 and the encoder 13 and output.

The output signal from the rough position calculator 6, that is, the rough incident position signals Xo and Yo of the incident gamma rays are supplied to the channel selector 14. This channel selector is, for example,
In the arrangement of the photomultiplier tubes shown in FIG. 7, if the calculated rough position signal is channel 14, the six channels 7, 8, 13, 15,
21,22 and channel 1 located in their center
The channel numbers of 7 photomultiplier tubes including 4 are output.

Further, the respective output signals from the respective preamplifiers 5 are supplied to the analog switch 16 via the dedicated integrating amplifiers 15, respectively. The output signal from the above-mentioned channel selector 14 is supplied to this analog switch,
Only the output of the integrating amplifier 15 corresponding to the selected channel number of the photomultiplier of the book is passed, and these are output to the A / D converter 17.

The selection signals supplied to the A / D converter 17 are all converted into digital signals here and then supplied to the position calculator 18 and the energy analyzer 19 in parallel, and the incident position signals X, G It is output as Y and a luminance signal (unblank signal) Z. Based on the X, Y and Z signals obtained in this way, RI distribution data is accumulated in the acquisition memory 20, the accumulated result is temporarily transferred to the display memory 21, and then the D / A converter 22 is used. The RI distribution image is displayed on the display 23.

(Problems to be Solved by the Invention) According to the above-described conventional apparatus, a dedicated analog integrating amplifier 15 is provided in each output circuit for waveform integration of each output signal of each photomultiplier tube 4. . Since these integrating amplifiers are analog type, they are relatively expensive and require complicated adjustment work when assembling and using the device. These drawbacks are further exacerbated as the number of photomultiplier tubes incorporated in the device increases.

The present invention has been made in view of the above problems, and an object of the present invention is to inexpensively configure a circuit by digitally implementing waveform integration for each output signal of each photomultiplier tube. It is possible to provide a gamma camera device that can be easily adjusted.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides a radiation of radiation emitted from a radioisotope (RI) administered in a subject only in a predetermined direction. A collimator that passes through, a scintillator that receives the radiation that has passed through this collimator to generate scintillation light of a light amount proportional to its energy value, and a plurality of scintillator that receives scintillation light from this scintillator and outputs an electrical signal proportional to that light amount. Photomultiplier tubes, a schematic position calculator for obtaining a rough radiation incident position based on each output signal from these photomultiplier tubes, and a schematic radiation incident position obtained by the rough position calculator. Means for selecting a photomultiplier tube of a channel necessary for obtaining a more accurate radiation incident position based on the data, Means for separately A / D converting each output of the photomultiplier tube selected by the selecting means, and adding the output later, and position calculation for calculating a more accurate radiation incident position based on the added output by the adding means. It is characterized by comprising means and means for creating an RI distribution image in the subject based on the radiation incident position data calculated by the position calculating means.

(Function) Of the radiation emitted from the RI administered into the subject, only the radiation passing through the collimator is incident on the scintillator. Here, scintillation light having a light quantity proportional to the energy value of incident radiation is generated and supplied to a plurality of photomultiplier tubes. Each of these photomultiplier tubes outputs an electric signal proportional to the supplied light.

The rough position calculator determines a rough radiation incident position based on the electric signals. Next, a photomultiplier tube of a channel required for obtaining a more accurate radiation incident position is selected on the basis of the thus obtained rough radiation incident position data. The outputs of the photomultiplier tubes selected in this way are A / D-converted separately and then separately added to obtain the waveform integral output for each. A more accurate radiation incident position is calculated based on the respective waveform integral outputs obtained in this way.

According to the above configuration, since the radiation incident position is calculated mainly by the digital circuit, an inexpensive circuit configuration can be provided and the adjustment work of the circuit can be simplified.

(Embodiment) The configuration of an embodiment of the present invention will be described with reference to FIGS. 1 and 2. A detector 32 for detecting radiation (gamma rays) emitted from the subject 31 to which the RI 30 is administered is provided. The detector 32 has a collimator 33 that allows only gamma rays in a predetermined direction to pass, a scintillator 34 that converts the gamma rays that have passed through the collimator into scintillation light,
The scintillator includes a light guide 35 for guiding the generated scintillation light, and a plurality of photomultiplier tubes 36 for receiving the scintillation light from the scintillator 34 via the light guide. The photomultiplier tubes 36 are, for example, as shown in FIG. 7, 61 photomultiplier tubes arranged so that a hexagonal light receiving plane is formed.

Each output terminal of each photomultiplier tube 36 is connected to a schematic position calculator 38 via a dedicated preamplifier 37.
Connect to. This schematic position calculator is the same as the schematic position calculator 6 used in the prior art device shown in FIG. 3, so a detailed description thereof will be omitted here.

The output signal of the rough position calculator 38, that is, the rough radiation incident position signals Xo and Yo are supplied to the channel selector 39. For example, in the arrangement of the photomultiplier tubes shown in FIG. 7, this channel selector is surrounded by 6 if the calculated rough position signal is channel 14.
A total of 7 channels, including channels 7, 8, 13, 15, 21, 22 and the channel 14 located at the center of the channels.
Outputs the channel number of the photomultiplier tube of the book.

In addition, the respective output signals from the respective preamplifiers 37 are
Each is supplied to the analog switch 41 via the dedicated delay circuit 40. Each of the delay circuits 40 has a delay time enough to extract the output of the photomultiplier tube selected by the channel selector 39. Here, the analog switch 41 operates to turn on only the output circuit of the photomultiplier tube corresponding to the channel number output from the channel selector 39.

An A / D converter 42 for converting the output signal from the analog switch 41 into a digital signal is provided. This A / D converter is configured to perform A / D conversion on the output waveform value of the photomultiplier tube shown in FIG. 2 (a) at a fine sampling clock pitch shown in FIG. 2 (b). It A / D
An adder 43 is provided to add the digital signals obtained by the converter 42 separately for each photomultiplier tube.

The addition outputs from the adder are supplied in parallel to the position calculator 44 and the energy analyzer 45, and the accurate gamma ray incident position signals X and Y and the luminance signal (unblank signal) Z are output by each. Further, a collection memory 46 to which various signals output in this way are supplied is provided. This acquisition memory is provided with a two-dimensional memory area in which X and Y position signals are designated.
_When the position signals of ₁ and Y ₁ are given and the luminance signal Z is given from the energy analyzer 45, 1 is added to the data stored in the memory unit designated by X ₁ and Y _1. . Such an operation is performed each time an output is supplied from the position calculator 44 and the energy analyzer 45, and after sufficient data acquisition is performed in this way, the RI distribution in the subject is stored in the acquisition memory 46. Image data is stored. In order to use this RI distribution image data as a display image, a display memory 47 is provided, the data is once transferred to this, and the transferred data is supplied to the display 49 via the D / A converter 48.

Next, the operation of the embodiment having the above configuration will be described. In FIG. 1, a detector 32 detects gamma rays emitted from a subject 31 to which RI 30 has been administered. At this time, an electric signal is output from the output terminal of the photomultiplier tube 36 of the detector 32 according to the incident position of the gamma ray. These output electric signals have higher crest values of the photomultiplier tubes 36 arranged closer to the gamma ray incident position. The output electric signal from each such electron multiplier 36 is amplified by each preamplifier 37 and then supplied to the rough position calculator 38.

The schematic position calculator 38 will now be described with reference to FIGS. 4 and 5 which show a conventional device. First, in FIG. 5, the signal supplied as described above is taken into the specific coordinate system position calculation circuit 7, collected by the OR circuit 10, and converted into a digital signal by the A / D converter 11. These digital signals are sorted by the magnitude of the signal value by the comparator 12, and finally output by the encoder 13 as a specific coordinate system position signal for each group of L axis, M axis, and N axis. Which group the output signal belongs to is identified by the signal from the group selection circuit 8. By supplying the identification signal and the specific coordinate system position signal to the absolute coordinate system position calculation circuit 9, the absolute coordinate system position signals Xo, Yo of the incident gamma rays are output from this circuit.

The signals Xo and Yo output from the rough position calculator 38 in this way are supplied to the channel selector 39.
Thereby, the channel selector 39, for example, when the rough position signals Xo and Yo calculated in FIG. 7 include the photomultiplier tube of the channel 14, the channel 14 and the six channels 7, which surround the photomultiplier tube, 8, 1
Select the photomultiplier tubes 3,15,21,22. Next, the channel selector 39 supplies the channel number of the photomultiplier tube thus selected to the analog switch 41.

As a result, the analog switch 41 turns on the output circuit of the photomultiplier tube of the selected channel. On the other hand, the photomultiplier tube output from each preamplifier 37 is supplied to each analog switch 41 through each delay circuit 40.
Therefore, here, the photomultiplier tube outputs of the seven channels selected by the channel selector 39 are A
It is output toward the / D converter 42.

In this A / D converter, the selected selected photomultiplier tube outputs are individually converted into digital signals as shown in FIG. 2, and these are supplied to the adder 43. In this adder, these digital signals are added separately for each channel to obtain the output waveform integral value of each photomultiplier tube. The data thus obtained is supplied to the position calculator 44 and the energy analyzer 45,
Here, more accurate incident position signals X and Y and a luminance signal (unblank signal) Z for the incident gamma ray are obtained based on them.

Based on these signals, the RI distribution data is stored in the collection memory 46, the storage result is temporarily transferred to the display memory 47, and then the RI distribution is displayed on the display 49 via the D / A converter 48. Display the image.

[Effects of the Invention] As described above, according to the gamma camera device of the present invention, when calculating the radiation incident position, first, a rough radiation incident position is obtained, and based on this, a more accurate radiation incident position is determined. Since the photomultiplier tube required for the calculation is selected and the position is digitally calculated based on these outputs, the circuit configuration can be made inexpensive and the adjustment work for the circuit can be facilitated. It is also possible to do so.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention,
FIG. 2 is a waveform diagram for explaining the operation of the A / D converter in the embodiment, FIG. 3 is a block diagram showing the configuration of a conventional device, and FIGS. 4 and 5 are examples of the conventional device. FIGS. 6 and 7 are block diagrams showing the configuration of the parts, respectively, for explaining the arrangement of the photomultiplier tubes. 32 ... Detector, 36 ... Photomultiplier tube 38 ... Schematic position calculator 39 ... Channel selector, 40 ... Delay circuit 41 ... Analog switch, 42 ... A / D converter 43 ... Adder, 44 ... Position calculator 45 ... Energy analyzer, 46 ... Collection memory 49 ... Display

Claims (1)

[Claims] 1. A radioisotope (R) administered into a subject.
Of the radiation emitted from I), a scintillator that transmits only a radiation in a predetermined direction, a scintillator that receives the radiation that has passed through the collimator and generates scintillation light of a light amount proportional to its energy value, and scintillation light from this scintillator. Receiving a plurality of photomultiplier tubes that output an electrical signal proportional to the amount of light, and a rough position calculator that determines a rough radiation incident position based on each output signal from these photomultiplier tubes, and Means for selecting a photomultiplier tube of a channel necessary for obtaining a more accurate radiation incident position based on the rough radiation incident position data obtained by the rough position calculator, and the photoelectron selected by this selecting means. By means for separately A / D converting each output of the multiplier tube and then adding it, and by this adding means The position calculating means calculates a more accurate radiation incident position based on the calculation force, and the means for creating an RI distribution image in the subject based on the radiation incident position data calculated by the position calculating means. A gamma camera device characterized in that