JPS6057552B2 - Coincidence detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coincidence detection device for detecting simultaneous occurrence of scintillation in two scintillators in a radiation computed tomography apparatus.

Radiation computed tomography equipment takes RI (radioactive isotope) into the patient's body, and when RI accumulates in specific organs, it detects the radiation emitted from the RI outside the body and creates a distribution image of RI on a specific tomographic plane. It consists of

When a positron radionuclide is used as a radionuclide, two gamma rays are generated in the 1800 direction, so if these gamma rays are incident on opposing scintillators and it is detected that scintillation occurs simultaneously, the gamma rays can be detected. You can know the location of the generation point. Conventionally, the light from the scintillator is immediately converted into an electrical signal, and a coincidence detection circuit is configured to detect coincidence through electrical processing.

Therefore, two systems of electric circuits were required, and a complicated coincidence detection circuit was also required. Since the time span of scintillation is extremely short, the requirements regarding circuit accuracy are extremely strict, and therefore electrical adjustment must be complicated and troublesome.
In view of the above, it is an object of the present invention to provide a coincidence detection device that requires only one electric circuit and can greatly reduce the number of adjustment steps, thereby making it possible to significantly reduce costs. An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, two scintillators 2 and 3 are arranged to face each other with a subject (patient) not shown in between. It is guided to the entrance surface of the multiplier tube 6. The two optical fibers 4 and 5 are bundled together in the middle so that the light enters the common entrance plane of one photomultiplier tube 6, so the light from each of the scintillators 2 and 3 is photomultiplier. By the time it reaches the entrance surface of the multiplier tube 6, it is added at the stage of the optical signal J.

The output of this photomultiplier tube 6 is sent to a detection circuit 7, and signals above a predetermined discriminator level are detected.
Assume that at point 1, the positrons of RI made of positron radionuclides are annihilated and two γ-rays are emitted 7 in the 1800 direction. Then, these γ rays are simultaneously emitted onto the scintillator 2|3, causing scintillation. This scintillation light reaches a photomultiplier tube 6 through optical fibers 4 and 5, respectively. When the intensities of the optical signals from the scintillators 2 and 3 are shown in FIGS. 2A and 2B, the timings of the optical signals of scintillation due to simultaneous human emission of γ-rays coincide. Since these two optical signals are added, the output of the photomultiplier tube 6 has a high level as shown in FIG. 2C. On the other hand, since the timings of the scintillation optical signals due to independently incident gamma rays do not coincide, the level of the added output from the photomultiplier tube 6 is low. Become. Therefore γ
If the discriminator level L is set as shown in FIG. 2C to detect only the high output level of the photomultiplier tube 6 when scintillation occurs simultaneously due to simultaneous human radiation, the detection circuit 7, the detection signal shown in FIG. 2D can be obtained. As described above, according to the present invention, coincidence can be easily detected by simply adding a light guide section to a conventional electrical signal processing system.

Further, since only one electrical signal processing system is required, a large amount of adjustment man-hours can be saved, and a large cost reduction is possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a time chart showing the operation of FIG. 1. 1... RI position, 2, 3... scintillator, 4,
5... Optical fiber, 6... Photomultiplier tube, 7...
detection circuit.

Claims (1)

[Claims] 1 Light from two scintillators facing each other is guided by a light guide and made incident on one photoelectric conversion device, and the light from both scintillators is added at the optical signal stage to determine the level of the output signal of the photoelectric conversion device. A coincidence detection device adapted to make a selection.