JPS628536Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiation detection device in which a large number of radiation detector bodies, each consisting mainly of a scintillator and a photomultiplier tube, are closely arranged in a ring shape around a subject.

The radiation detection device used in positron CT equipment and single photon emission CT equipment is
A scintillation detector is mainly used as the detector body, and this is generally constructed as shown in FIG. That is, a rectangular parallelepiped scintillator 1 made of NaI (Tl) crystal or BGO crystal.
The scintillator 1 is equipped with a photomultiplier tube (hereinafter referred to as PMT) 2 optically coupled to the scintillator 1 via silicone grease or the like (not shown), and a bleeder circuit 3. In addition, in Figure 1,
4 is a container for protecting and shielding the scintillator 1, and is made of a material such as aluminum that absorbs little incident gamma rays, and its inner surface is coated with a reflective agent (not shown) such as barium sulfate or white paint. . 5 is PMT2 and bleeder circuit 3
A container for protection and light-shielding, and this container 5 and
A PMT magnetic shield (not shown) such as Mumetal is provided between the PMTs 2. 6 is PMT2
and input and output cables such as high voltage cables, signal cables, and low voltage cables of the bleeder circuit 3.

In recent years, most radiation detection devices for positron CT systems have one detector body housed in a single container consisting of containers 4 and 5, and this is placed around the subject in a ring shape, as shown in Figure 1. (A part of the arrangement is shown in Figure 2).

By the way, the detection efficiency of incident gamma rays of such a radiation detection device is determined by the packing ratio α (α=nw/πD), which represents the degree of closeness of the arrangement of the detector bodies.
It is known that it is proportional to the power of Here, n is the total number of detector bodies arranged in a ring shape, and w is 1
The width of the tip surface of the two scintillators 1 (see FIG. 2), π is the circumference, and D is the diameter of the ring.

However, in the conventional radiation detection device, since the scintillator 1 is placed in a container 4 made of aluminum or the like, the angle of the container 4 protrudes at the tip thereof, and the gap between the scintillators becomes large, resulting in a small packing ratio α. This has resulted in a drawback that the detection efficiency of incident gamma rays is low.

The present invention was developed in order to eliminate the above-mentioned drawbacks, and it is possible to bring the packing ratio α close to 1, thereby minimizing the loss of detection efficiency of incident gamma rays, and moreover, it is possible to minimize the loss of detection efficiency of incident gamma rays. It is an object of the present invention to provide a radiation detection device that can be easily adjusted.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a front view showing an embodiment of the radiation detection device according to the present invention, FIG. 4 is a sectional view taken along the line -- in FIG. 3, and FIG. 5 is an enlarged view of the main parts in FIG. 1. So, in each of these figures, 1~
3 and 6 are each the same as in FIG. Reference numeral 11 denotes a scintillator ring, which, as shown in FIG. 6, includes a pair of flat rings 11a and 11b arranged opposite to each other. This ring 11
On the outer peripheral side between a and 11b, rings 11a and 1
Rings 11a, 1b are arranged at equal intervals along the circumference of 1b.
A wedge 11c is fitted toward the center of ring 11b, thereby forming a large number of holes 11d in the radial direction between rings 11a and 11b. A rectangular parallelepiped scintillator 1 is inserted into each of the holes 11d, and the rings 11a, 1
A cylindrical plate 11e made of aluminum or the like that absorbs little incident gamma rays is fitted between the inner circumferences of the cylindrical plates 1b and 1b. In addition, the wedge 11c is inserted into each hole 11d formed by the wedge 11c.
The scintillators 1 are set to be formed at opposing positions with the center point of the scintillators 11b placed therebetween, and the scintillators 1 inserted into the holes 11d are arranged on the same circumference. The shape and spacing of the wedges 11c are such that when the scintillators 1 are inserted into each hole 11d and arranged in a ring shape, the corners of adjacent scintillators 1, 1 touch each other, and the scintillators 1 are arranged most closely. (See Figure 5).

12 is a flat light-shielding fixing ring that concentrically fixes the scintillator ring 11; 13 is a light-shielding fixing ring 1 on the outer periphery of the scintillator ring 11;
PMT fixing ring concentrically fixed to 2. As is clear from FIG. 7, this PMT fixing ring 13 is provided with a hole 13a into which the PMT 2 is inserted. A large number of holes 13a are formed corresponding to the holes 11d of the scintillator ring 11, and the PMT 2 (in the illustrated example, the PMT 2 integrated with the bleeder circuit 3) is inserted into each hole 13a, and the PMT 2 is inserted into the hole 13a using silicone grease or the like. scintillator 1
It is held by screws 14 while being optically coupled to. Reference numeral 15 denotes a light shielding cover that shields the scintillator 1 and the PMT 2 from light with a light shielding fixing ring. Each ring 1 on the side opposite to the light-shielding fixed ring 12 of both rings 11 and 13
1 to 13 are attached concentrically. Note that an O-ring, resin, or the like (not shown) for light shielding is fitted into the gap created between the bleeder circuit 3 and the periphery of the hole 13a of the PMT fixing ring 13. Reference numeral 16 designates adjustment circuits for the PMTs 2 disposed at portions of the light-shielding fixing ring 12 that are not covered by the light-shielding cover 15, for example, on the outer peripheral side of the bleeder circuit 3. Although not shown, the adjustment circuit 16 includes a gain adjustment circuit that adjusts the gain of the PMT 2, a time pickoff circuit that adjusts the output timing, and the like.

Next, the operation will be explained. Regarding the radiation detection operation, there is no particular difference from the conventional detection device described above. In the detection device of the present invention, the scintillator 1 is inserted into the hole 11d of the scintillator ring 11 with the container 4 (see FIGS. 1 and 2) removed in the conventional detection device, and the adjacent scintillator 1,
They are configured so that they can be arranged closely to the extent that the corners of one are in contact with each other. At the same time, the container 5 in the conventional detection device was also removed to facilitate the close arrangement of the scintillators 1, and the light shielding function of the containers 4 and 5 was provided to the light shielding fixing ring 12 and the light shielding cover 15. The light shielding cover 15 is PMT
The light shielding cover 15 does not cover up to the adjustment circuit 16 of No. 2.
This makes it possible to adjust the gain, output timing, etc. of PMT2 without removing the PMT2.

Therefore, according to the present invention, it is possible to bring the packing ratio α as close to 1 as possible without impairing the function of the conventional detection device, and to minimize the decrease in the detection efficiency of incident gamma rays related to the arrangement of the detection device. In addition, there are effects such as the ability to easily adjust the PMT on the light-shielding fixing ring.

In the above-described embodiments, a single layer structure detection device in which the detector bodies are arranged in a ring shape has been described, but the present invention is of course applicable to a multilayer structure detection device. In this case, the detection devices shown in FIG. 4 may be stacked in several stages.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the main body of a radiation detector consisting of a scintillation detector, Fig. 2 is a diagram showing the main parts of a conventional detection device, and Fig. 3 is a front view showing an embodiment of the radiation detection device according to the present invention. , Fig. 4 is a cross-sectional view taken along the - line in Fig. 3, Fig. 5 is an enlarged view of the main parts in Fig. 1, and Fig. 6 is an enlarged view of the scintillator ring in Figs. 3 and 4. FIG. 7 is an exploded perspective view of the scintillator ring, the PMT fixing ring, and the light-shielding fixing ring shown in FIGS. 3 and 4. 1...Scintillator, 2...Photomultiplier tube (PMT), 11...Scintillator ring, 11
a, 11b... Flat ring, 11c... Wedge, 11d... Hole, 11e... Cylindrical plate, 12...
Light-shielding fixing ring, 13...PMT fixing ring,
15... Light shielding cover, 16... Adjustment circuit.

Claims (1)

[Scope of utility model registration request] In a radiation detection device in which a large number of radiation detector bodies, each consisting mainly of a scintillator and a photomultiplier tube, are closely arranged in a ring shape around a subject, a pair of flat rings arranged opposite each other is placed on the outer periphery side. A large number of holes are formed in the radial direction between the flat rings by wedges fitted at intervals,
A scintillator ring in which the scintillator is inserted into each hole, a flat plate-shaped light-shielding fixing ring that fixes the scintillator ring concentrically, and a light-shielding fixing ring that is located on the outer periphery of the scintillator ring and that connects the photomultiplier tube to the scintillator and the light-shielding ring. a photomultiplier tube fixing ring concentrically fixed to the light-blocking fixing ring to hold the scintillator and the photomultiplier tube in a combined state; a light-blocking cover that blocks light from the scintillator and the photomultiplier tube with the light-blocking fixing ring; A radiation detection device comprising: an adjustment circuit for the photomultiplier tube disposed on the light-shielding fixing ring outside the light-shielding cover.