JPH03107787A - Gamma camera device - Google Patents

Abstract

PURPOSE:To simplify a circuit by selecting photoelectron multiplier tubes required to calculate an accurate radiation incidence position from a rough radiation incidence position and calculating a position digitally according to their outputs. CONSTITUTION:Gamma rays are radiated from a sample 31 doped with RI30 and electric signals corresponding to the incidence position of the gamma ray are outputted from the output terminals of photoelectron multiplier tubes 36 of a detector 32. Those output electric signals have larger crest values as their multiplier tubes 36 are arranged closer to the gamma ray incidence position. The output signals are amplified by preamplifiers 37 and supplied to a rough position calculator 38. Signals X0 and Y0 outputted by the calculator 38 are supplied to a channel selector 38. An analog switch 41 inputs signals from the selector 39 and signals from delay circuits 40. An A/D converter 42 converts the signal from the switch 41 and supplies the result to an adder 43. The adder 43 supplies output waveform integral values added by channels to a position calculator 44 and an energy analyzer 45.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a gamma camera device that creates RI distribution data within a subject administered with a radioisotope (RI), and particularly relates to The present invention relates to a gamma camera device in which a means for calculating the incident position of radiation is digitalized.

(Prior Art) An example of a conventional gamma camera is shown in FIG. That is,
A detector 3 detects gamma rays emitted from a subject 2 to which RI1 has been administered. At this time, an electrical 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. These output electric signals have a higher signal peak value when the photomultiplier tube 4 is disposed close to the gamma ray incident position. The output electrical signals from each photomultiplier tube 4 are amplified by respective preamplifiers 5 and then supplied to a rough position calculator 6.

As shown in FIG. 4, the rough position calculator 6 is composed of 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 calculates the photomultiplier tubes 4 that are grouped into L-axis, M-axis, and N-axis. It detects the output signal of the doubler tube 4 and outputs it as a specific coordinate system position signal. The group selection circuit 8 is a circuit that performs selection control of each group when the photomultiplier tubes 4 are divided into groups. The absolute coordinate system position calculation circuit 9 calculates approximate absolute coordinates based on the specific coordinate system position signal for each group output from the specific coordinate system position calculation circuit 7 and the group selection signal output from the group selection circuit 8. System position signals Xo, Yo
Calculate and output.

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 an L axis (Ll, L2...Ln), an M axis (Ml, N
2. -, Mn), and the N axis (Nl, N2...Nn). Since each group has the same circuit configuration, only the L-axis group will be explained. Each output of the photomultiplier tube is connected to an OR circuit 10, and this output terminal is connected to an A/D converter 11. As a result, the A/D converted output signal is output as a specific coordinate system position signal by the comparator 12 and encoder 13.

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

Further, each output signal from each preamplifier 5 is supplied to an analog switch 16 via a dedicated integrating amplifier 15, respectively. This analog switch is supplied with the output signal from the channel selector 14 described above, and
Only the output of the integrating amplifier 15 corresponding to the selected channel number of the photomultiplier tube is passed through, and these outputs are directed 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 in parallel to the position calculator 18 and the energy analyzer 19 to obtain the incident position signal X of the gamma ray to be determined, respectively. Y and a luminance signal (unranked signal) Z. Based on the X, Y, and Z signals obtained in this way, RI distribution data is accumulated on the collection memory 20, and after the accumulation result is temporarily transferred to the display memory 21, it is transferred via the D/A converter 22. The RI distribution image is displayed on the display 23.

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

This invention has been made in view of the above problems, and its purpose is to enable the circuit to be constructed at low cost by digitally performing waveform integration for each output signal of each photomultiplier tube. An object of the present invention is to provide a gamma camera device which can be easily adjusted.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above-mentioned object, this invention uses only radiation in a predetermined direction among the radiation emitted from a radioisotope (RI) administered into a subject. A collimator that allows the radiation to pass through, a scintillator that receives the radiation that has passed through this collimator and generates scintillation light with an amount of light proportional to its energy value, and a plurality of scintillators that receive the scintillation light from this scintillator and output an electrical signal that is proportional to the amount of light. a photomultiplier tube, a rough position calculator that calculates a rough radiation incidence position based on each output signal from these photomultiplier tubes, and a rough radiation incidence position calculated by this rough position calculator. A means for selecting a photomultiplier tube of a necessary channel in order to obtain a more accurate radiation incident position based on the data, and A/D conversion of each output of the photomultiplier tube selected by the selection means. position calculation means for calculating a more accurate radiation incidence position based on the addition output of the addition means; and means for creating an RI distribution image.

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

A rough position calculator determines the rough radiation incidence position based on these electrical signals. Next, based on the rough radiation incident position data obtained in this manner, a photomultiplier tube of a channel necessary to obtain a more accurate radiation incident position is selected. The outputs of the photomultiplier tubes selected in this way are individually A/D converted, and then added separately to obtain integrated waveform outputs for each. A more accurate radiation incident position is calculated based on the respective waveform integral outputs obtained in this manner.

According to the above configuration, since the calculation of the radiation incident position is performed mainly using the digital circuit, an inexpensive circuit configuration can be provided, and the adjustment work for 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 is provided to detect radiation (gamma rays) emitted from a subject 31 to which RI 30 has been administered. This detector 32 includes a collimator 33 that allows only gamma rays in a predetermined direction to pass through, a scintillator 34 that converts the gamma rays that have passed through this collimator into scintillation light,
This scintillator is composed of a light guide 35 that guides the generated scintillation light, and a plurality of photomultiplier tubes 36 that receive the scintillation light from the scintillator 34 via this light guide.

Further, these photomultiplier tubes 36 are arranged such that a hexagonal light-receiving plane is formed by 61 photomultiplier tubes, as shown in FIG. 7, for example.

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

The output signals of the approximate position calculator 38, that is, the approximate radiation incident position signals Xo, Yo, are supplied to the channel selector 39. For example, in the array of photomultiplier tubes shown in FIG. , 21, 22 and the channel number of a total of seven photomultiplier tubes including channel 14 located at the center of them.

In addition, each output signal from each preamplifier 37 is
Each signal is supplied to an analog switch 41 via a dedicated delay circuit 40. These delay circuits 40 each have a delay time sufficient 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 is provided to convert the output signal from the analog switch 41 into a digital signal.

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). Ru. An adder 43 is provided which separately adds the digital signals obtained by the A/D converter 42 for each photomultiplier tube.

Each addition output from this adder is supplied in parallel to a position calculator 44 and an energy analyzer 45, which output more accurate gamma ray incident position signals X, Y and a luminance signal (unranked signal) Z, respectively. Also, a collection memory 4 to which various signals outputted in this manner are supplied.
6 will be provided. This collection memory has a two-dimensional memory area in which X and Y position signals are designated, and when the position calculator 44 gives, for example, the X+ and Y+ position signals, and the energy analyzer 45 gives the luminance signal Z. ,X+,Y+
1 for the data stored in the memory section specified by
is added. Such an operation is performed each time the output is supplied from the position calculator 44 and the energy analyzer 45, and after sufficient data has been collected in this way, the RI distribution within the subject is stored in the collection 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 -H data is transferred thereto, and the transferred data is transferred to the D/A converter 4.
8 to a display 49.

Next, the operation of the embodiment having the above configuration will be explained.

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 electrical 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 a high peak value at any photomultiplier tube 36 located near the gamma ray incident position. The output electrical signals from each of the photomultiplier tubes 36 are amplified by each preamplifier 37 and then supplied to a rough position calculator 38 .

The general position calculator 38 will now be described with reference to FIGS. 4 and 5, which illustrate prior art devices. 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 comparator 12 according to the magnitude of the signal value, and are finally outputted by the encoder 13 as specific coordinate system position signals for each group of L, 2M, and N axes. The group to which this output signal belongs is identified by the signal from the group selection circuit 8. By supplying this identification signal and the specific coordinate system position signal to the absolute coordinate system position calculation circuit 9, absolute coordinate system position signals Xo, Yo of the incident gamma ray are outputted from this circuit.

The signals Xo, Yo output from the rough position calculator 38 in this manner are supplied to a channel selector 39.

As a result, the channel selector 39 selects, for example, if there is a photomultiplier tube in channel 14 in the rough position signals Xo, Yo calculated in FIG. 8,1
Select a photomultiplier tube of 3°15.21.22. Next, the channel selector 39 supplies the channel number of the photomultiplier tube thus selected to the analog switch 41.

This causes the analog switch 41 to turn on the output circuit of the photomultiplier tube of the selected channel. On the other hand, the analog switch 41 is supplied with a photomultiplier tube output from each preamplifier 37 via each delay circuit 40 .

Therefore, here, the photomultiplier tube outputs of the seven channels selected by the channel selector 39 are A
/D converter 42.

This A/D converter separately converts the selected photomultiplier tube outputs that are sent into digital signals as shown in FIG. 2, and supplies these to an adder 43. This adder adds these digital signals separately for each channel to obtain the output waveform integral value of each photomultiplier tube. The data obtained in this way is supplied to a position calculator 44 and an energy analyzer 45, where they are used to generate more accurate incident position signals X, Y and a brightness signal (unblank signal) 2 for the incident gamma ray. get.

Based on these signals, RI distribution data is accumulated on the acquisition memory 46, and after the accumulation result is once transferred to the display memory 47, the RI distribution data 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 incidence position, first the approximate radiation incidence position is determined, and then a more accurate radiation incidence position is determined based on this. Since the photomultiplier tubes required for calculation are selected and the position is calculated digitally based on these outputs, the circuit configuration can be made inexpensive and adjustments to the circuit can be made easily. It is also possible to do so.

[Brief explanation 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 same embodiment, FIG. 3 is a block diagram showing the configuration of the conventional device, and FIGS. 4 and 5 are respective examples of the conventional device. 6 and 7 are diagrams for explaining the arrangement of photomultiplier tubes, respectively. 32...Detector 36...Photomultiplier tube 38...Rough position calculator 39...Channel selector 40...Delay circuit 4
1...Analog switch 42...A/D converter 43...Adder 44...Position calculator 45...Energy analyzer 46...Collection memory 49...Display device Fig. 2 Figure 6 Figure 7

Claims (1)

[Claims] A collimator that allows only radiation in a predetermined direction to pass among the radiation emitted from a radioactive isotope (RI) administered into a subject, and a scintillation light beam that receives the radiation that has passed through this collimator and has an amount of light proportional to its energy value. A scintillator that is generated, a plurality of photomultiplier tubes that receive scintillation light from this scintillator and output electrical signals proportional to the amount of light, and a rough radiation incidence based on each output signal from these photomultiplier tubes. A rough position calculator for determining the position and a photomultiplier tube of the channel required to determine a more accurate radiation incidence position based on the rough radiation incidence position data determined by this rough position calculator. means for separately A/D converting each output of the photomultiplier tubes selected by the selection means and adding them later; and calculating a more accurate radiation incident position based on the added output by the addition means. 1. A gamma camera device comprising: a position calculation means for calculating a radiation incidence position; and a means for creating an RI distribution image within the subject based on radiation incident position data calculated by the position calculation means.