JPH0524068Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field This invention is based on the method of detecting RI (single photon or positron emitting radiation) administered into the body by arranging a large number of radiation detectors in a ring around the subject. The present invention relates to an improvement in a radiation detector suitable for a ring-type ECT device (emission computer tomography device) that detects radiation from a radioactive isotope and obtains a distribution image of the RI.

BACKGROUND TECHNOLOGY Ring-type ECT devices for single photons or positrons usually use a radiation detector in which one PMT (photomultiplier tube) is coupled to one scintillator.

Problems that the invention aims to solve For this reason, because there is a limit to the miniaturization of PMTs, it is not possible to miniaturize the radiation detector as a whole. Furthermore, when used in a ring-type ECT device, there is a problem in that as a result, the spatial resolution of the reconstructed image cannot be improved.

Of course, this problem would be solved if the PMT could be made smaller, but even then, increasing the spatial resolution would require a large number of radiation detectors and therefore the PMT, leading to the problem of high cost.

The purpose of this invention is to provide a radiation detector that can obtain high spatial resolution.

Means for Solving the Problems The radiation detector according to this invention has at least one
a plurality of optically separated scintillators arranged in a direction, and a surface inclined substantially in a V-shape in the arrangement direction, and the scintillator is optically coupled to this surface. It consists of a light guide and a plurality of PMTs optically coupled to the plurality of scintillators via the light guide.

Function Since multiple PMTs are optically coupled to multiple scintillators via light guides, each
By taking the ratio of PMT outputs, it is possible to determine which scintillator is responsible for emitting light.

The light guide has a substantially V-shaped inclined surface in the direction in which the scintillators are arranged, and the scintillators are optically coupled to this surface, so that the light from each scintillator can be conveniently distributed to the PMT. This can improve the separation characteristics of each scintillator.

Embodiment In FIG. 1, a large number (eight in this embodiment) of scintillators 1 to 8 formed into strips are arranged in one direction. In the ring type ECT device,
This arrangement direction is defined as the circumferential direction. A light reflecting material is applied between these scintillators 1 to 8, making them optically independent from each other, and on the other hand, two PMTs 21 and 22 are placed at the other end of the scintillators 1 to 8.
The light is optically coupled via the light guide 11. The light guide 11 is made of a transparent member such as acrylic resin, and has a surface inclined in a V-shape in the direction in which the scintillators 1 to 8 are arranged, as shown in FIG. Optically coupled. The shapes of the ends of the scintillators 1 to 8 are determined in accordance with the V-shaped shape of the light guide 11.

In this way, the light guide 11 has a V-shaped inclined surface, and the scintillators 1 to 8 are placed on this surface.
are optically coupled, the light from each of the scintillators 1 to 8 is appropriately distributed to each of the two PMTs 21 and 22. Therefore,
Let the outputs of PMT21 and 22 be a and b, respectively,
For example, if we take the ratio (a-b)/(a+b), this will well represent the light emission position. That is, when a radiation source is placed in front of each of the scintillators 1 to 8 and the appearance frequency of signals with the above ratio is measured, the result is as shown in FIG. 3, and the peak portion is divided for each scintillator 1 to 8. In this way, two PMT2
Based on the outputs a and b of 1 and 22 (a-b)/
(a+b) signals cause eight scintillators 1 to
It can be seen which of the 8 scintillators emitted light.

4 and 5 show a second embodiment, and unlike the first embodiment shown in FIGS. 1 and 2, the light guide 12 is formed into a stepped V-shape. There is. In this case as well, the same light distribution as in the light guide 11 of the first embodiment is performed, and the separation characteristics of the scintillators 1 to 8 are improved.

FIGS. 6 and 7 show a third embodiment. In this third embodiment, the scintillators are arranged in two directions.
This method is extended to two dimensions to perform two-dimensional discrimination. That is, as shown in FIG. 6, the scintillators are arranged both in the circumferential direction and in the slice thickness direction perpendicular thereto, and the PMTs 2 to 24 are similarly arranged in the circumferential direction and in the slice thickness direction. Ori,
The light guide 13 is also V-shaped in both the circumferential direction and the slice thickness direction, as shown in FIG. In this case, each output of PMT21-24 is
If d, then {(a+c)-(b+d)}/{(a+c)+(b+
d)}, the position of the scintillator in the circumferential direction can be discriminated, and {(a+b)-(c+d)}/{(a+b)+(c+
d)} The position of the scintillator in the slice thickness direction can be discriminated. That is, 8×4=32 scintillator positions can be discriminated by the four PMTs 21 to 24.
Note that the method of calculating the ratio for position calculation is not limited to the above method; for example, (a+c)/(b+d) is used to discriminate the circumferential direction, and (a+b)/(c+d) is used to discriminate the slice thickness direction. Other ratios can also be considered.

When these first to third embodiments are used as a radiation detector for a ring-type ECT device,
The number of PMTs allows finer discrimination of the radiation incident position in the circumferential direction, improving the spatial resolution of the image, and also increases the number of slices because the smaller number of PMTs allows finer discrimination of the radiation incidence position in the slice thickness direction. is easy.

In the above embodiment, a PMT with one circuit is used, but a PMT with two circuits may be used. In this case, one PMT is sufficient in the embodiments of Figs. 1 and 4, and two PMTs are sufficient in the embodiment of Fig. 6. In addition, the number of scintillators and
The number of PMTs is not limited to the above embodiments.

Effects of the invention According to this invention, more scintillators can be discriminated with fewer PMTs, and the ring type
It is possible to reduce the cost of the ECT device. Furthermore, the scintillator can be made smaller without being limited by the size of the PMT, and the spatial resolution can be improved.

[Brief explanation of the drawing]

Fig. 1 is a schematic perspective view of an embodiment of this invention, Fig. 2 is a perspective view of only the light guide portion, Fig. 3 is a graph showing a signal histogram, and Fig. 4 is a schematic perspective view of an embodiment of the invention.
The figure is a schematic perspective view of the second embodiment, FIG. 5 is a perspective view of only the light guide portion of the same embodiment, FIG. 6 is a schematic perspective view of the third embodiment, and FIG. It is a perspective view of only the light guide part of the same Example. 1 to 8... scintillator, 11, 12, 13...
...Light guide, 21-24...PMT.

Claims (1)

[Scope of utility model registration request] It has a plurality of optically separated scintillators arranged in at least one direction, and a surface inclined substantially in a V-shape in the arrangement direction, to which the scintillators are optically coupled. and a plurality of photomultiplier tubes optically coupled to the plurality of scintillators via the light guide.