JPH0619444B2 - 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 means for accurately calculating the incident position of radiation incident on a radiation detector.

(Prior Art) First, an example of a conventional gamma camera will be described. 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 of an amount proportional to the physical data of incident radiation is generated and supplied to a plurality of photomultiplier tubes. These photomultiplier tubes are divided into a plurality of groups, and each group outputs an electric signal corresponding to incident radiation, that is, a position signal of each specific coordinate system. The position calculator calculates the incident position signal in the absolute coordinate system for the incident radiation based on those signals. On the other hand, the energy discriminator outputs the unblank signal only when the added value of each output of the photomultiplier tubes is compared with the set reference value and a certain condition is satisfied, that is, when the radiation having the desired energy is incident. To do. An RI distribution image in the subject is created based on the absolute coordinate system position signal and the unblank signal thus obtained.

(Problems to be Solved by the Invention) The plurality of photomultiplier tubes in the above-mentioned conventional example are, for example, as shown in FIG. 5, three groups, that is, L axis (L _{1 to} L _n ), M axis (M _{1 to} M _n ) and the N axis (N ₁
~ N _n ) groups. The output of each photomultiplier tube thus divided is supplied to the position calculator 1 shown in FIG. 6 for each group. When the output of the photomultiplier tube 2 is supplied to this position calculator, those outputs are extracted by the OR circuit 3, converted into a digital signal by the A / D converter 4, and the set value or more by the comparator 5. Only the signal having the value of is taken out and sent to the encoder 6. The position signal L _S in the L-axis coordinate system is calculated and output by this encoder. The other M-axis and N-axis coordinate systems are similarly calculated and output as position signals M _S and N _S , respectively. The position signal L _S obtained in this way,
By sending M _S and N _S to the encoder 7, the radiation incident position is finally calculated and output as X and Y.

According to the conventional apparatus having the above-described configuration, for example, when the radiation incident position on the detector is the intermediate position P between the two photomultiplier tubes 20 and 21, as shown in FIG. L
When calculating the position signal of the axis coordinate system, either the L ₂ axis or the L ₃ axis is randomly selected. Therefore, the data of such a portion contains a non-uniform component, and the radiation incident position signal calculated based on the data eventually also contains a non-uniform component. Therefore, R created by these radiation incident position signals
The I distribution image also includes a non-uniform density portion.

The present invention has been made in view of the above problems, and an object thereof is to provide a radiation incidence position even if the radiation incidence position on the detector is at an intermediate position between two photomultiplier tubes adjacent to each other. Is distributed regularly and alternately to the coordinate axes of the same group adjacent to each other to provide an RI distribution image in which the non-uniform density portion is removed.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides only radiation in a predetermined direction out of radiation emitted from a radioisotope (RI) administered into a subject. A collimator that passes through, a scintillator that receives the radiation that has passed through this collimator, and generates scintillation light with a light amount proportional to the physical data, and receives scintillation light from this scintillator, and outputs an electrical signal proportional to that light amount. A plurality of photomultiplier tubes, a position calculator that calculates the incident position of the incident radiation based on the output signals from these photomultiplier tubes, and the energy of the incident radiation based on the output signals of the photomultiplier tubes. An energy analyzer for analysis, an output incident position signal from the position calculator and an output energy from the energy analyzer. The gamma camera apparatus comprising a means for generating an RI distribution image in the subject on the basis of ghee analysis signal, wherein the position calculator comprises first divides the photomultiplier tube of the plurality of the plurality of coordinate axes group 1
Means, second means for obtaining a position signal corresponding to the incident position of radiation for each coordinate axis group divided by the first means, and radiation based on each position signal obtained by the second means. The third means for obtaining the incident position information and the third means for obtaining the position signal by the second means, when the incident position of the incident radiation is at a substantially intermediate position between two adjacent photomultiplier tubes, A fourth means for alternately switching and outputting position signals corresponding to the photomultiplier tubes each time such incident radiation is incident.

(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 output signal from each photomultiplier tube is provided to the position calculator. The position calculator receives these output signals and first divides them into a plurality of coordinate axis groups by the first means. The signal group for each group thus divided is then used by the second means to calculate the position information corresponding to the radiation incident position for each coordinate group. Furthermore, the position information for each of these coordinate groups is supplied to the third means,
Here, the radiation incident position information is calculated based on these pieces of information.

Here, when the position signal for each group is obtained by the second means, when the radiation incident position comes to an almost intermediate position between the two adjacent photomultiplier tubes, the photomultiplier tubes are moved to the photomultiplier tubes each time. The corresponding position signals are alternately switched and output.

(Embodiment) The configuration of an embodiment of the present invention will be described with reference to FIGS. 1 to 4. In FIG. 1 showing the overall configuration of this embodiment, a detector 12 for detecting radiation (gamma rays) emitted from the inside 11 of the subject to which RI 10 has been administered is provided.
The detector 12 includes a collimator 13 that passes only gamma rays in a predetermined direction, a scintillator 14 that converts the gamma rays that have passed through the collimator into scintillation light, a light guide 15 that guides the scintillation generated by the scintillator, and a scintillator via this light guide. 1
The photomultiplier tube 16 receives the scintillation light from the light source 4. Also, a plurality of photomultiplier tubes 1
For example, as shown in FIG. 2, reference numeral 6 denotes 61 photomultiplier tubes arranged so that a hexagonal light receiving plane is formed.

Each output terminal of each photomultiplier tube 16 is connected via a preamplifier 17 to a position calculator 18 for calculating a radiation incident position, which will be described in detail later. The output position signals X and Y of this position calculator are also supplied to the collection memory 19. This acquisition memory is provided with a two-dimensional memory area designated by the X and Y position signals, and when the position calculator 18 gives, for example, X ₁ and Y ₁ position signals, it is stored in the memory unit X ₁ and Y _1. One count is added to the counted data. Such an operation is performed every time the output from the position calculator 18 is supplied, and after sufficient data collection, the collection memory 19
The RI distribution image data in the subject is stored in. This RI
In order to use the distribution image data as a display image, the display memory 20 is provided, the data is once transferred to this, and the transferred data is supplied to the display 22 via the D / A converter 21.

The position calculator 18 is constructed as shown in FIG.
Prior to the description of this configuration, the coordinate axis grouping of the photomultiplier tube 16 will be described with reference to FIG. In this embodiment, the photomultiplier tube 16 has three coordinate axis groups, namely, L axis (L ₁ , L ₂ , ..., L ₉ ), M axis (M
₁ , M ₂ , ..., M ₉ ), N-axis (N ₁ , N ₂ , ..., N ₉ )
It is divided into. Position calculation circuits 23, 24 dedicated to each axis, which are independent of each of the three groups,
25 is provided. Since all of these circuits have the same configuration, the L-axis one 23 will be described here. That is, this circuit uses an OR circuit 26 for selecting a photomultiplier tube belonging to the L axis, an A / D converter 27 for A / D converting the output signal of this OR circuit, and an output signal of this A / D converter. The comparator 28 performs a comparison operation on the other hand, and outputs a signal having a value exceeding the set value. The comparator 28 recognizes the number of outputs from this comparator, and outputs the output as it is when the number is one. However, when the number is two, the output judging device 29 alternately outputs one of those outputs, and the encoder 30 which outputs the L-axis position signal based on the output from this output judging device. Each axis position calculation circuit 23,
The output signals of 24 and 25 are encoders 31 that finally calculate the radiation incident positions X and Y based on these signals.
Is supplied to.

Next, the operation of the embodiment having the above configuration will be described. In FIG. 1, a detector detects gamma rays emitted from the subject 11 to which RI 10 has been administered. At this time, the detector 12
An electric signal is output from the output terminal of the photomultiplier tube 16 according to the incident position of the gamma ray. These output electric signals have a higher crest value as the photomultiplier tube 16 is arranged closer to the gamma ray incident position. The output electric signal from each photomultiplier tube 16 is amplified by each preamplifier 17 and then supplied to the position calculator 18.

The output signals supplied to the position calculator 18 are supplied to the respective axes L, M, and M by an OR circuit 26 incorporated in each of the coordinate axis position calculation circuits 23, 24, 25 shown in FIG.
Each N is divided into groups. The state of this grouping is shown in FIG. Signals grouped on the L axis are A / D
After being converted into a digital signal by the converter 27, the digital signal is supplied to the comparator 28, where the comparison operation is performed, and for the signal having a value exceeding the set value, the output judging device 29
Generate output towards.

In this output judging device, when the output signal supplied is one,
That is, when the gamma ray incident position is located on the light receiving surface of any one photomultiplier tube, the output signal is supplied to the encoder 30 as it is, and this outputs the L axis position signal L _n . Further, when the number of output signals supplied is two, that is, when the gamma ray incident position is located at a substantially intermediate position between two arbitrary photomultiplier tubes, the L-axis position signals corresponding to those photomultiplier tubes respectively. Are alternately supplied to the encoder 30 each time there is such an event, which is output as L _n . (The flowchart is shown in FIG. 4.) Similarly, for other groups, that is, the M-axis and the N-axis, the M-axis position signal M _n and the N-axis position signal N _n are respectively output from the coordinate axis position calculation circuits 24 and 25. Is output.
Each axis position signal L _n , M _n , output as described above
N _n is supplied to the encoder 31, where the gamma ray incident position signals X and Y are finally calculated and output.

In this way, based on the calculated position signals X and Y for each incident gamma ray output from the position signal calculator 18, RI distribution data is accumulated in the collection memory 19, and the accumulation result is temporarily stored in the display memory 20. After the transfer, the RI distribution image is displayed on the display 22 via the D / A converter 21.

In the above embodiment, a plurality of photomultiplier tubes are connected to L,
Although the description has been made on the case of dividing into three groups of M and N axes, the present invention is not limited to this, and it is also possible to divide into a plurality of groups other than three groups.
Other design changes can be made without departing from the scope of the invention.

[Effects of the Invention] As described above, according to the gamma camera device of the present invention, when radiation is incident on the intermediate position between any two adjacent photomultiplier tubes, each time such radiation is incident, Since the axial position signals of the two photomultiplier tubes are alternately output, it is possible to provide an RI distribution image with improved nonuniformity of concentration.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention,
FIG. 2 is an explanatory view showing a mode of grouping of photomultiplier tubes in the same embodiment, FIG. 3 is a block diagram showing a configuration of a position calculator in the apparatus shown in FIG. 1, and FIG. FIG. 5 is a flow chart for explaining the operation of the encoder in the figure, FIG. 5 is an explanatory view showing the arrangement of photomultiplier tubes in the conventional apparatus, and FIG. 6 is a block diagram showing the configuration of the main part of the conventional apparatus. is there. 12 ... Detector, 16 ... Photomultiplier tube, 18 ... Position calculator, 19 ... Acquisition memory, 20 ... Display memory, 21 ... D / A converter, 22 ... Display device, 23, 24, 25 ... Coordinate axis position calculation circuit, 26 ... OR circuit, 27 ... A / D converter, 28 ... Comparator, 29 ... Output judgment device, 30, 31 ... Encoder

Claims (2)

[Claims] 1. A radioisotope (R) administered into a subject.
Of the radiation emitted from I), a scintillator that transmits only radiation in a predetermined direction, a scintillator that receives the radiation that has passed through the collimator, and generates scintillation light in an amount proportional to the physical data, and scintillation from this scintillator. A plurality of photomultiplier tubes that receive light and output an electrical signal proportional to the amount of light, a position calculator that calculates the incident position of incident radiation based on the output signals from these photomultiplier tubes, and An energy analyzer for performing energy analysis of incident radiation based on the output signal of the photomultiplier tube, and the inside of the subject based on the output incident position signal from the position calculator and the output energy analysis signal from the energy analyzer In the gamma camera device, the position calculator comprises: A first means for dividing a plurality of photomultiplier tubes into a plurality of coordinate axis groups, and a second means for obtaining a position signal corresponding to the incident position of radiation for each coordinate axis group divided by the first means. And this second
The third means for obtaining the radiation incident position information based on each position signal obtained by the means and the two photoelectron multipliers in which the incident positions of the incident radiation are adjacent to each other when the position signal is obtained by the second means. Fourth means for alternately switching the position signals respectively corresponding to those photomultiplier tubes each time such incident radiation is incident, when they are at substantially intermediate positions of the multiplier tubes. Gamma camera device. 2. The comparator, wherein the fourth means extracts an output having a value exceeding a set value from the outputs from the photomultiplier tubes belonging to the same coordinate axis group each time the radiation is incident, and the comparison. An output discriminator that recognizes the number of outputs extracted by the detector, outputs the output as it is when the number is one, and alternately outputs one of the outputs when the number is two; The gamma camera device according to claim 1, comprising an encoder that calculates a position signal for each coordinate axis group based on an output from the output determination device.