JPS5923273A - Radiant ray detector of emission ct device - Google Patents

Abstract

PURPOSE:To raise a packing ratio and to raise detecting efficiency of incident gamma rays, by arraying radially a frame provided with a scintillator supporting plate, etc, whose width is almost equal to the width of a scintillator, and covering it with a light shielding plate. CONSTITUTION:Width of a scintillator supporting plate 13 of the lower end of a frame 11 is made almost same as the width of a scintillator 1, and a photoelectric multiplier 2 connected to the scintillator 1, a bleeder circuit 3, etc. are supported the frame 11 by a holding plate 17, a supporting plate 15, etc. These frames 11 are arrayed and installed radially so that the adjacent tip parts are brought into contact with each other, and when the whole is covered with a light shielding plate 26, a packing ratio is improved comparing with the case when each one set of the scintillator, etc. is contained in a light shielding vessel, and detecting efficiency of incident gamma rays, etc. being proportional to square-law of this ratio is raised.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiation detector for an emission CT 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. .

Positron CT equipment and single photon emission C
The radiation detector used in the T device mainly uses a scintillation detector as the detector body, and this is generally constructed as shown in FIG. That is, Na
I(Tt) crystal or i-1: A rectangular parallelepiped scintillator 1 made of BGO crystal, and a photomultiplier tube (hereinafter referred to as PMT) optically coupled to this scintillator 1 via silicone grease or the like (not shown). ) 2 and leader circuit 3
(7) Taille. In FIG. 1, 4 is a container for protecting and shielding the scintillator 1, which is made of a material such as aluminum that has low absorption of incident gamma rays. In between is a PMT magnetic shield such as mu-metal (not shown)
is applied. Reference numeral 6 indicates a high voltage cable, a signal cable or a low voltage cable of the PM'r 2 and the bleeder circuit 3, and an output cable.

In recent years, most of the radiation detectors in positron CT systems have one detector main body housed in a single container consisting of containers 4 and 5, and this is placed in a ring around the subject, as shown in Figure 1. A large number of them are closely arranged in a shape (a part of the arrangement is shown in Fig. 2).

By the way, it is known that the geometrical detection efficiency of incident gamma rays of such a radiation detector is proportional to the banking ratio α (α-nw/πD)02, which represents the degree of closeness of the arrangement of the detector bodies. . Here, n is the total number of detector bodies arranged in a ring shape, W is the width of the tip surface of the scintillator 1, π is pi, and D is the diameter of the ring.

However, in conventional radiation detectors, scintillator 1
is located in the container 4 made of aluminum or the like, so the corner of the container 4 protrudes at the tip, which reduces the detection efficiency of one sipma ray relative to the width of the tip surface of the detector body. there were.

The present invention was made to eliminate the above-mentioned drawbacks, and provides a radiation detector for emission CT equipment I in which the backing ratio α is increased as much as possible to approach 1, and the improvement in detection efficiency of incident gamma rays is reduced. The purpose is to provide.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a front view schematically showing an embodiment of a radiation detector for an emission CT apparatus according to the present invention, FIG. 4 is a sectional view taken along the l'V-IV line in FIG. 3, and FIG. This is an enlarged view of the main parts inside, which are also marked 2 in the figure.
, 3 and 6 are each the same as in FIG. 2 also refers to a scintillator as in FIG. 1, but here a reflective agent (not shown) is coated on the side surface of the scintillator. 11 is the detector body (
(see Figure 1), which is constructed as shown in Figure 6. That is, the predetermined [
...@ a pair of frame boards 12, 12 placed opposite each other,
A scintillator support plate 13 made of an aluminum plate or the like with low gamma ray absorption is fixed between the tips of the frame plates 12 and 12, and the scintillator support plate 13 is opposed to the support plate 13 and is located at a position where the support plate 13 is a predetermined length apart. The main structure and PMT support plate 15 are fixed between the frame plates 12 and 12 using screws 14.
It is something that can be achieved. In this case, scintillator support plate 1
The width W' of the scintillator 1 is set approximately equal to the width W of the scintillator 1. In FIG. 6, 16 is a scintillator holding plate, 17 is a PMT holding plate, and 18 is an intermediate frame plate, which are fixed using screws 19 as shown in FIG. In addition, numeral 21 is a frame reinforcing plate, 21 is a frame fixing metal fitting, and 22 is a frame reinforcing plate.
is a frame positioning pin.

The detector body is assembled into the frame 11 in the following manner. First, scintillator support plate 13
A scintillator 1 is placed on the back surface. After passing the leader circuit 3 part integrated with the PMT 2 through the round hole 15a of the PMT support plate 15, the tip of the PMT 2 is slightly attached to the rear end surface of the scintillator 1 through silicone grease or the like (not shown). They are brought into contact with each other in the valved state for optical coupling, and in this state, a screw cap is screwed into the screw hole 15b on the side of the PMT support plate 15, and the PMT 2 is fixed via the leader circuit 3. As a result, the scintillator l, the PMT 2, and the leader circuit 3 are held together in the framework 11, and the framework 1
The incorporation of the detector body into 1 is achieved. Incidentally, the surplus space within the framework 11 can be used as a storage space for various electronic circuits (not shown) such as a preamplifier.

A large number of ``'' are arranged in a ``CIJ'' shape along the outer periphery of a cylindrical continuous light plate 5 made of an aluminum plate with low gamma ray absorption fitted into the inner periphery of the fixed ring U (Fig. 7 shows one example of the arrangement). In this case, the scintillator support plates 13ψ11 at the tips of the frame Mi1 are placed as close to each other as possible.

The periphery of all the frameworks 11 assembled in the detector main body arranged in this manner is covered with the light-shielding cover 26 and the fixing ring, and is shielded from light.

In addition, in FIG. 4, 27 is a guide for the pin 22,
The pin 22 defines the position of the tip of the frame m11.

This is a pedestal for fixing the opening framework 11 to the fixing ring 24, and each framework 11 is screwed between the pedestal 28 part and the fixing metal fitting 21 part. Further, the output cable 6 from the detector body is led out to the outside via a connector (not shown) attached to the periphery of the fixing ring 24.

Next, the operation will be explained. Regarding the radiation detection operation, there is no particular difference from the conventional detector described above. The detector of the present invention replaces the detector body with the containers 4 and 5 (
(See FIGS. 1 and 2) The width W of the scintillator 1 is set to be approximately equal to the width W of the scintillator 1, and when the framework 11 is arranged, the sides of the scintillator support plates 13 are brought close to each other, so that adjacent scintillators 1.1 are closely spaced to the extent that they are in contact with each other. It is configured so that it can be arranged. In addition, in the detector of the present invention, the continuous light function provided by the container 4.5 is provided in the fixing ring and part of the light-shielding cover.

Therefore, according to the present invention, the backing ratio α can be brought as close to υ1 as possible without changing the functions of conventional detectors, and the decrease in the detection efficiency of incident gamma rays determined by geometric conditions can be minimized. It has the effect of being able to

In the above-mentioned embodiment, a case has been described in which the ring-shaped arrangement of the detector bodies is arranged in four rows in the direction of the body M of the subject, but the arrangement is not limited to this, and the number can be increased or decreased. The number of rows can be easily increased or decreased by mainly changing the lengths of the support plates 13, 15 and presser plates 16, 17 of the frame 11, and accordingly changing the sizes of the light shielding plate δ and the light shielding cover 26. In addition, although the frame #, [1, 1 is used with screw holes (not shown) and guides 27 for connecting a plurality of detector bodies to the metal fittings 21 in the circumferential direction of the ring, the present invention is not limited to this. There isn't.

In any case, it goes without saying that by providing the positioning means, the work of arranging the frame work 1 on the fixing ring becomes easier. Here, it is preferable that the fixing metal fittings 21 have a slightly larger area in order to improve seating when the framework 11 is arranged into different fixing rings.

Further, in the above embodiment, the light-shielding cover 26 is constructed as a single unit, but it may be constructed in several parts, and each part can be attached to and detached from the fixing ring separately. Each framework] 1. Training of different detector bodies,
Convenient for repairs.

[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 detector, and FIG. 3 is an example of a radiation detector for an emission CT device according to the present invention. 4 is a schematic front view, FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3, and FIG. 5 is an enlarged view of the main parts in FIG.・Scintillator support plate, bottom...fixing ring, 26...shading cover. Patent applicant Makoto Ishiita, Director of the Agency of Industrial Science and Technology - Figure 5

Claims (1)

[Claims] In 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 around a subject, the width of the scintillator support plate at the tip is set to be approximately equal to the width of the scintillator. The framework holding the photomultiplier tube optically coupled to the scintillator disposed on the back surface of the scintillator support plate is placed concentrically on a flat fixing ring at the side of the scintillator support plate at the tip thereof. 1. A radiation detector for an emission CT apparatus, characterized in that a large number of these are arranged in close proximity to each other, and the entire framework is covered with a light shielding cover and the fixing ring.