JPH0147755B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scintillation camera, which is a type of radiological diagnostic equipment.

The scintillation camera is constructed as shown in FIG. A large number of photodetectors 12 such as photomultiplier tubes are mounted on the back of a scintillator 11 that emits light (causes scintillation) upon incidence of radiation.
are arranged, and the output of each photoelectric detector 12 is sent to a position calculation circuit 13 and an energy discrimination circuit 14. The photoelectric detector 12 generates an output according to the intensity of the incident light, and the closer to the scintillation, the greater the output. Therefore, the position calculation circuit 13 calculates the emission position (radiation incident position) from the magnitude relationship of the output of each photoelectric detector. ) can be obtained. This position calculation circuit 13 is usually constructed using a resistance matrix method or a delay line method. The energy discrimination circuit 14 discriminates the energy of incident radiation based on the sum of the outputs of all the photoelectric detectors 12, and when the energy is a predetermined value, it operates the position calculation circuit 13 and also outputs a luminance signal (Z signal). Output. This Z signal is sent to the CRT display device 15, and a bright spot is displayed at a position defined by the position signal (X, Y signal) from the position calculation circuit 13. That is, each time radiation is incident, a bright spot appears on the screen of the CRT display device 15 at a position corresponding to the incident position.

A patient is given a specific RI (a radioactive isotope that emits gamma rays, etc. with specific energy) as a drug, and when the RI accumulates in a specific organ, the scintillation camera is placed near that organ. For example, only gamma rays of a specific energy emitted from the RI mentioned above are detected, and the distribution state of the RI concentration is
It is displayed on the screen of the CRT display device 15 and can be used to diagnose the organ.

By the way, in this scintillation camera, if two or more gamma rays are incident at the same time (to be precise, within the response time of the detection system and circuit system), the incident position cannot be calculated.In other words, the position calculation circuit 13 and Since the incident position cannot be calculated unless the incident occurs at a time interval that is longer than the response time of the detection system and circuit system up to the energy discrimination circuit 14, in the case of simultaneous incidence like this, the photoelectric detector 1
The output from 2 has no choice but to be discarded. Therefore, from this point of view, there is a limit to the sensitivity and count rate characteristics (number of incident radiation that can be detected per unit time) as a scintillation camera.

The present invention overcomes the above limitations, improves sensitivity and count rate characteristics, and provides a scintillation system that can be used for high-speed clinical testing. The purpose is to provide cameras.

An embodiment of the present invention will be described below. Second
As shown in the figure, for example, when 61 photodetectors 12 numbered No. 1 to No. 61 (consisting of photomultiplier tubes, for example) are placed on the back side of the scintillator 11, the incident field of radiation is set at the center. It is divided into two halves, a right half and a left half, and the photoelectric detectors 12 are divided into groups corresponding to each half. Here, No. 1 to No. 43 correspond to the left half, and No. 1 to No. 43 are set to A group, and No. 19 to No. 61 correspond to the right half, and No. 19 to No. 61 are set to B group. Furthermore, A
The reason why the group and the B group overlap is to accurately calculate the positions near the center dividing line of each of the right and left halves.

As shown in FIG. 3, each group includes a position calculation circuit 13a, 13b and an energy discrimination circuit 14.
a, 14b are provided, and position calculation circuits 13a, 13
Each position signal (X, Y signal) of
6a and 16b, respectively. This X signal is compared by comparators 17a and 17b, and it is determined whether the incident position is in the right half or the left half of the field of view. parallel to the axis). In this way, if the X and Y signals obtained from the outputs from the photoelectric detectors 12 of group A are within the left half, the analog gate 18a is closed and the delayed X and Y signals are sent to the analog buffer 19a. Also B
In the group, if the X and Y signals similarly obtained are within the right half, the analog gate 18b is closed and the delayed X and Y signals are sent to the analog buffer 19b.

The display control circuit 20 uses this analog buffer 1
9a, 19b and the multiplexer 21, and receives the output of the energy discrimination circuits 14a, 14b, and when the output of the energy discrimination circuits 14a, 14b of either group is input, the multiplexer 21 controls the X of that group. ,Y
Send the signal to the CRT display device. Furthermore, when radiation enters the left and right visual fields simultaneously (or almost simultaneously), the outputs of the energy discrimination circuits 14a and 14b are inputted to the display control circuit 20 simultaneously (or almost simultaneously). Therefore,
To determine the order of these outputs, or to give priority to one of them in the case of simultaneous outputs, the X and Y signals of the first group are first sent to the multiplexer 21, and during this time the X and Y signals of the next group are sent to the analog buffer. The X and Y signals are held, and when the previous one is completed, the multiplexer 21 is switched to transmit the X and Y signals of the next group.

Even when radiation is simultaneously incident on each of the divided fields of view, detection and display are possible, and sensitivity and count rate characteristics are improved.

In addition, in the above embodiment, the field of view is set only in the X direction.
Of course, the number of divisions can be increased, such as dividing the field of view in the Y direction and dividing the entire visual field into four. The sensitivity and counting rate characteristics improve as the number of divisions increases.

Furthermore, in the above description, the analog A combination of buffers 19a, 19b, display control circuit 20, multiplexer 21, and CRT display device 15 is used, but instead of this, each position signal output from analog gates 18a, 18b is converted to an A/D converter. If the data is sent to a storage device via the 100-degree storage device, and the number of incident radiations is added for each position, one image of the entire field of view can be constructed in this storage device.

As described above with respect to the embodiments, according to the present invention, the field of view is divided to prepare for the simultaneous incidence of radiation, so the sensitivity and count rate characteristics are improved. Suitable for high-speed clinical testing.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional scintillation camera, FIG. 2 is a schematic plan view showing the positional relationship between a scintillator and a photodetector of a scintillation camera according to an embodiment of the present invention, and FIG. 3 is a block diagram of the scintillation camera of the same embodiment. 11...Scintillator, 12...Photoelectric detector,
13, 13a, 13b...position calculation circuit, 14,
14a, 14b...Energy discrimination circuit, 15...
CRT display device, 16a, 16b...delay circuit,
17a, 17b... comparator, 18a, 18
b...Analog gate, 19a, 19b...Analog buffer, 20...Display control circuit, 21...
multiplexer.

Claims (1)

[Claims] 1. In a scintillation camera comprising a scintillator that emits light when radiation is incident, and a number of photoelectric detectors that are arranged on the back side of this scintillator and detect the emitted light, the field of view where the radiation is incident is divided into a plurality of parts. , the photoelectric detectors are divided into groups in an overlapping manner corresponding to each divided field of view, and for each group of photoelectric detectors, an energy discrimination circuit, a position calculation circuit, and an output from the position calculation circuit are output. A determination circuit that determines whether the position signal is within the field of view corresponding to the group, and a gate that outputs the position signal when it is determined that the position signal is within the field of view corresponding to the group are provided. A scintillation camera characterized by being provided with a device that composes one image based on position signals output from gates for each group.