JPS628537Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure of a radiation detector 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.

Radiation detectors used in positron CT devices and single photon emission CT devices mainly use a scintillation detector as the detector body, and this is generally configured as shown in FIG. That is, NaI(Tl) crystal or
Rectangular parallelepiped scintillator 1 made of 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 of the radiation detectors in positron CT devices have one detector main body housed in one 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).

Incidentally, it is known that the detection efficiency of incident gamma rays of such a radiation detector is proportional to the square of the packing ratio α (α=nw/πD), which represents the degree of closeness in which the detector bodies are arranged. Here, n is the total number of detector bodies arranged in a ring shape, w is the width of the tip surface of one scintillator 1 (see Fig. 2),
π is pi and D is the diameter of the ring.

However, in the structure of conventional radiation detectors,
A container 4 in which the scintillator 1 is made of aluminum or the like
Since the scintillators are located inside the scintillators, the angle of the container 4 at the tip thereof is bulged out, the gap between the scintillators becomes large, and the packing ratio α becomes small. This has resulted in a drawback that the detection efficiency of incident gamma rays is low.

The present invention was made in order to eliminate the above-mentioned drawbacks, and it is a radiation detector that can increase the packing ratio α as much as possible to approach 1 and minimize the loss of detection efficiency of incident gamma rays. The purpose is to provide structure.

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 structure of a radiation detector 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. 1 to 3 and 6 are the same as in FIG. 1, respectively. 11
is a scintillator ring, which, as shown in FIG. 6, comprises a pair of flat rings 11a and 11b arranged opposite to each other. this ring 1
On the outer peripheral side between 1a and 11b, rings 11a,
The rings 11 are arranged at equal intervals along the circumference of the ring 11b.
A wedge 11c is fitted toward the center of the rings 11a, 11b, which allows the rings 11a, 11b to
A large number of holes 11d are formed in the radial direction between each other. A rectangular parallelepiped scintillator 1 is inserted into each of the holes 11d, and the ring 11
A cylindrical plate 11e made of aluminum or the like that absorbs little incident gamma rays is fitted between the inner circumferences a and 11b. Note that the wedge 11c is inserted into the ring 1 so that each hole 11d formed by the wedge 11c is inserted into the wedge 11c.
The scintillators 1a and 11b are set to be formed at opposite positions with the center points between them, and the scintillators 1 inserted into the holes 11d are arranged on the same circumference. Also, wedge 11c
The shape and spacing of the scintillator 1 are such that each hole 11
d and arranged in a ring shape, the corners of adjacent scintillators 1, 1 are in contact with each other, and the scintillators 1 are set so as to be arranged most closely (see FIG. 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 covers the detector main body including the scintillator 1, PMT 2, bleeder circuit 3, etc., the scintillator ring 11, and the PMT fixing ring 13 with a light-shielding fixing ring 12. The input and output cables 6 from the detector main body are led out to the outside via a connector (not shown) attached to the periphery of the light-shielding fixing ring 12.

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 present invention, the scintillator 1 is placed in the hole 11d of the scintillator ring 11 with the container 4 (see FIGS. 1 and 2) removed from the conventional detector.
The scintillators 1, 1 are arranged so close together that the corner portions of adjacent scintillators 1, 1 are in contact with each other. At the same time, the container 5 in the conventional detector
The scintillators 1 are also removed to facilitate close arrangement of the scintillators 1, and the light-shielding function of the containers 4 and 5 is provided to the light-shielding fixing ring 12 and the light-shielding cover 15.

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 detector, and to minimize the decrease in the detection efficiency of incident gamma rays related to the detector arrangement. There is an effect.

In the above-described embodiment, a detector having a single layer structure in which the detector bodies are arranged in a ring shape has been described, but it goes without saying that the present invention can also be applied to a detector having a multilayer structure. In this case, the detectors shown in FIG. 4 may be stacked in several stages.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the main body of a radiation detector consisting of a scintillation detector, Figure 2 is a diagram showing the main parts of the structure of a conventional detector, and Figure 3 is an example of the structure of a radiation detector 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. FIG. 7 is an exploded perspective view of the scintillator ring, PMT fixing ring, and light-shielding fixing ring in FIGS. 3 and 4. FIG. 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.

Claims (1)

[Scope of utility model registration request] In a radiation detector structure 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 outer periphery between a pair of flat rings arranged opposite each other. A number of holes are formed in the radial direction between the flat rings by wedges fitted at equal intervals, and a scintillator ring in which the scintillator is inserted into each hole, and a flat plate that fixes the scintillator ring concentrically. a light-shielding fixing ring; and a photomultiplier tube fixing concentrically fixed to the light-shielding fixing ring, the photomultiplier tube being located on the outer periphery of the scintillator ring and holding the photomultiplier tube optically coupled to the scintillator. A radiation detector comprising: a ring; and a light-shielding cover that covers at least the photomultiplier tube fixing ring, the scintillator ring, the scintillator, and the photomultiplier tube with the light-shielding fixing ring. structure.