JPH02272386A - Gamma camera device - Google Patents

Abstract

PURPOSE:To obtain a radioactive isotope (RI) distribution image of high quality by correcting position information of each calculated coordinate group to deflect it a prescribed extent inside at the time when position information corresponding to a coordinate end part is included in the position information. CONSTITUTION:Respective output signals from photomultiplers 16 which are supplied to a position calculator 18 are divided to groups in OR circuits 26 of coordinate axis position calculating circuits 23 to 25 by coordinate axes L, M, and N. Signals divided to groups are compared with one another by a comparator 28 to select position information having a maximum value. The selected position information is supplied to an encoder 29; and when position information of an end part is selected, corrected information deflected a prescribed extent inside is selected and outputted. Output position information Ln, Mn, and Nn from axis position calculating circuits 23 to 25 are supplied to an encoder 30 to finally calculate an incidence position X, Y of radiation.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a gamma camera device that creates R1 distribution data within a subject administered with a radioactive isotope (R1), and particularly relates to The present invention relates to a gamma camera device with improved means for calculating the incident position of radiation.

(Prior Art) A general configuration of a scintillation camera is shown in FIG. 1 is a scintillator that generates scintillation light when radiation (gamma rays) emitted from a subject to which a radioactive isotope has been administered is incident, and 2 is a plurality of scintillators that are optically coupled to scintillator 1 and convert the scintillation light into electrical signals. This is a photomultiplier tube. The scintillator 1 and photomultiplier tube 2 described above constitute a detector 9 together with a collimator, a light guide, etc. (not shown). The output signal from this detector 9 passes through each preamplifier 3, and then
The information is supplied to the Y position calculation circuit 4, where the scintillation light generation position information is calculated.

That is, the position calculation circuit 4 is composed of a weighting circuit using, for example, a resistance matrix, and calculates the values of X", X-,
The output signal of the detector 9 is supplied to the pulse height analysis circuit 7 via the variable resistor 5 and the summing amplifier 6, where the energy value information of the incident radiation is obtained. Based on the position information and energy value information, the display system 8 can display an R1 distribution image within the subject.

(Problem to be Solved by the Invention) Here, to explain in detail the means for calculating the light emitting position on the scintillator 1 when radiation is incident, for example, 61 photomultiplier tubes 2 are connected to each other as shown in FIG. The light receiving surfaces are arranged in a dense manner on a hexagonal plane. Now, assuming that the "weighting by position" value given to each photomultiplier tube 2 is given as shown in FIG. 7, the incident position when radiation (gamma ray) is incident as shown by the arrow in the figure. The calculation method for calculating is shown in the figure. The one in this figure deals only with the X-axis direction.
Calculated as 0.5. Although not shown, the calculation is performed in exactly the same manner in the Y-axis direction.

However, as described above, since the photomultiplier tube 2 has a finite number of 61 pieces arranged in a hexagonal shape, the following problem has occurred. In other words, if the number of photomultiplier tubes could be increased to sufficiently cover a wide field of view, this problem would not be the same, but this is not possible due to installation space, economical reasons, etc. The sensing aperture is relatively limited.

Therefore, if the incident position of the incident radiation is relatively inside the detector aperture, there are photomultiplier tubes surrounding the incident position, and the output signals of these tubes are used to calculate the incident position, so there is no equivalent problem. does not occur. On the other hand, if radiation is incident on the periphery, some of the photomultiplier tubes surrounding this incident position will be incomplete and the calculation of the incident position will be affected by unbalanced factors. Therefore, the calculated incident position will be slightly biased inward from the actual position.

Therefore, even if an R1 distribution image is created based on detection data collected under such circumstances, there is a drawback that the image will be distorted in the peripheral areas.

This invention has been made in view of the above-mentioned problems, and its purpose is to improve the periphery of an R1 distribution image caused by radiation incident on the periphery of a detector sensitive aperture formed by a plurality of photomultiplier tubes. The object of the present invention is to provide high-quality RI distribution images useful for diagnosis.

[Structure of the Invention (Means for Solving the Problems)] In order to achieve the above object, the present invention is directed to a method that uses only radiation in a predetermined direction among the radiation emitted from a radioisotope (R1) 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. photomultiplier tubes, a position calculator that calculates the incident position of the incident radiation based on the output signals from these photomultiplier tubes, and an energy analysis of the incident radiation based on the output signals of the photomultiplier tubes. and means for creating an R1 distribution image within the subject based on an output incident position signal from the position calculator and an output energy analysis signal from the energy analyzer. , the position calculator divides the plurality of photomultiplier tubes into a plurality of coordinate axis groups;
means for determining the position signal corresponding to the incident position of the radiation for each coordinate axis group divided by the first means; a third means for determining incident position information; and a fourth means for biasing the determined position signal of the corresponding coordinate axis group inward when the position signal determined by the second means coincides with the end position signal. It is characterized by including means.

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

Here, if the position information for each coordinate group calculated by the second means includes position information corresponding to the coordinate end, the corresponding position information is shifted inward by a predetermined amount. After the correction is made as described above, the fourth means controls the supply to the third means.

In this way, according to the present invention, even if radiation is incident on the periphery of the detector aperture, the position information calculated midway is corrected so as to be biased inward, and this corrected information is Since the radiation incident position is calculated based on this, peripheral distortion can be sufficiently alleviated and a high-quality R1 distribution image useful for diagnosis can be provided.

(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 is provided to detect radiation (gamma rays) emitted from a subject 11 to which RIIO has been administered. This detector 12 includes a collimator 13 that allows only gamma rays to pass in a predetermined direction, a scintillator 14 that converts the gamma rays that have passed through this collimator into scintillation light, a light guide 15 that guides the scintillation generated by this scintillator, and a light guide 15 that guides the scintillation generated by this scintillator. It is composed of a plurality of photomultiplier tubes 16 that receive scintillation light from a scintillator 14.

Further, as shown in FIG. 2, for example, the plurality of photomultiplier tubes 16 include 61 photomultiplier tubes arranged so as to form a hexagonal light-receiving plane.

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 collection memory has a two-dimensional memory area specified by the X, Y position signals, and when the position calculator 18 gives, for example, Xi, Y1 position signals, the count stored in the memory section Xi, Yl is One count is added to the data. Such an operation is performed every time the output is supplied from the position calculator 18, and after collecting sufficient data, the data is stored in the collection memory 19.
RI distribution image data within the subject is stored. This R1
In order to use the distribution image data as a display image, a display memory 2o is provided, data is once transferred thereto, and the transferred data is supplied to a display 22 via a D/A converter 21.

The position calculator 18 is constructed as shown in FIG.

Prior to explaining this configuration, the grouping of the coordinate axes of the photomultiplier tube 16 will be explained with reference to FIG. In this embodiment, the photomultiplier tube 16 has three groups of coordinate axes: the L axis (LL, L2..., L9), the M axis (Ml, M2.

..., M9), N axis (Nl, N2. ..., N9
). Independent position calculation circuits for each axis for each of those three groups 23.24
．． 25 will be provided. Since all of these circuits have the same configuration, the L-axis circuit 23 will be explained here. That is, this circuit includes an OR circuit 26 that selects the photomultiplier tube belonging to the L axis, an A/D converter 27 that converts the output signal of this OR circuit into A/D, and an output signal of this A/D converter. The encoder 29 includes a comparator 28 that performs a comparison operation, and an encoder 29 that outputs an L-axis position signal based on the output signal of the comparator. The encoder 29 also
When the obtained L-axis position information matches the end position of the L-axis, the position information is outputted by being shifted inward by one unit position. Each output signal of each axis position calculation circuit 23, 24, 25 is supplied to an encoder 26 which finally calculates the radiation incident position X, Y based on these signals.

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

In FIG. 1, a detector detects gamma rays emitted from a subject 11 to which R110 has been administered. At this time, an electrical signal is output from the output terminal of the photomultiplier tube 16 of the detector 12 according to the incident position of the gamma ray. These output electric signals have a higher signal peak value in the photomultiplier tube 16 located near the gamma ray incident position.

The output electrical signals from each photomultiplier tube 16 are amplified by each preamplifier 17 and then supplied to a position calculator 18 .

Each output signal supplied to this position calculator 18 is outputted to each axis, M,
Grouped by N.

This grouping is shown in FIG. 2. The signals grouped on the L axis are converted into digital signals by the A/D converter 27 and then supplied to the comparator 28, where they are compared and the position information having the maximum value is selected. This selected position information is supplied to the encoder 29, and this information is
If the position does not correspond to the end position of the shaft, the position information Ln is output as is. That is, in FIG. 2, L2 to L
When 8 is selected, the selected information is output as is.

On the other hand, when the end position information L1 or L9 is selected, for example, in the case of Ll, L2 is shifted inward by one unit.
information is selected and output, and in the case of L9, L8 is selected and so on. A flowchart regarding the operation of such encoder 29 is shown in FIG. Although the explanation here will be omitted, the M-axis and N-axis groups operate in exactly the same manner. Each axis position calculation circuit 23, 24
The output positions Ln, Mn, Nn from .degree. 25 are fed to an encoder 30, where the radiation incidence position

Y is finally calculated. Therefore, the device signals X and Y generated by the position calculator 18 are always corrected for the radiation incident on the periphery of the detector, so R
It is possible to reliably reduce peripheral distortion of a 1-distribution image.

In the above embodiment, the photomultiplier tubes are divided into three groups, M, and H, but the present invention is not limited thereto, and can be divided into any number of groups. Other design changes can be made as appropriate without changing the gist of the invention.

[Effects of the Invention] As described above, according to the gamma camera device of the present invention, even if radiation is incident on the periphery of the detector aperture, the position information calculated midway is biased inward. Since the radiation incident position is calculated based on this corrected information, it is possible to provide a high-quality RI distribution image useful for diagnosis in which peripheral distortion is sufficiently alleviated.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing the mode of grouping of photomultiplier tubes in the same embodiment, FIG. 3 is a block diagram showing the configuration of the position calculator in the device shown in FIG. 1, and FIG. FIG. 5 is a block diagram showing the configuration of the conventional device, and FIGS. 6 and 7 are diagrams each explaining the operation of the conventional device. 12...Detector, 16...Photomultiplier tube 18...
Position calculator, 19... Collection memory 20... Display memory, 21... D/A converter 22... Display 23.24.25... Coordinate axis position calculation circuit 30...
encoder

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 is generated, a plurality of photomultiplier tubes that receive scintillation light from the scintillator and output an electrical signal proportional to the amount of light, and the input of incident radiation is determined based on the output signals from these photomultiplier tubes. a position calculator that calculates a position; an energy analyzer that performs energy analysis of incident radiation based on an output signal of the photomultiplier tube; and an output incident position signal from the position calculator and an output from the energy analyzer. and means for creating an RI distribution image within the subject based on an energy analysis signal, wherein the position calculator divides the plurality of photomultiplier tubes into a plurality of coordinate axis groups. means for determining the position signal corresponding to the incident position of the radiation for each coordinate axis group divided by the first means; a third means for determining incident position information; and a fourth means for biasing the determined position signal of the corresponding coordinate axis group inward when the position signal determined by the second means coincides with the end position signal. A gamma camera device comprising means.