JPH05100035A - Gamma-ray detector - Google Patents

Abstract

PURPOSE:To provide a gamma-ray detector capable of reducing the deterioration of resolution and sensitivity at the periphery section and sharply moving the gamma-ray incidence face near a subject. CONSTITUTION:A scintillator section 4 inserted with fiber-like plastic scintillators 3 into through holes 2A of a collimator section 2 arranged and formed with multiple through holes 2A into a lattice shape and a position- sensitive PMT 6 are provided. The gamma-ray incidence end face of the collimator section 3 is formed into a curved face shape along the body surface of a subject P, and the distance between the gamma-ray incidence face of the plastic scintillators 3 and the gamma-ray incidence face of the collimator section 2 is made a uniform preset distance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects gamma rays emitted from a radioisotope (hereinafter referred to as RI) administered to a subject and measures the distribution of RI within the subject based on the detection signal. The present invention relates to a gamma ray detector for a scintillation camera.

[0002]

2. Description of the Related Art Conventionally, as a γ-ray detector of this type, there is one shown in FIG. 4, for example. In the figure, 101
Shows three γ-ray detectors provided in the SPECT apparatus. Each γ-ray detector 101 has a substantially rectangular solid Na shape.
Scintillator 101A composed of I etc. and scintillator 1
Collimator 101B mounted on the γ-ray incident surface of 01A
And a photomultiplier tube (not shown) is connected to the back surface (the surface opposite to the γ-ray incidence surface) of the scintillator 101A. These γ-ray detectors 101 are used for the subject P at the time of imaging.
It is arranged so as to surround.

When the subject P is imaged, each γ-ray detector 101 rotates around the subject P, and at the same time, the γ-rays emitted from the RI previously administered to the subject P are different from each other. γ
The light enters the scintillator 101A via the collimator 101B of the line detector 101. When light is generated in the scintillator 101A due to the incidence of γ rays, the photomultiplier tube performs photoelectric conversion, and a preamplifier attached to this photomultiplier tube generates an electric signal. An information processing unit (not shown) of the SPECT apparatus obtains information on the distribution of RI in the subject P based on this electric signal, and creates a γ-ray image of the subject P according to this information.

[0004]

However, in the case of the above-mentioned conventional technique, the γ-ray incident surface of the scintillator 101A is a flat surface, and the peripheral portion thereof has a substantially annular sectional shape as compared with the central portion. Since the distance to P becomes large, there is a problem that resolution and sensitivity are unavoidably deteriorated and, therefore, there is a limit to the proximity of the γ-ray detector 101 to the subject P. Therefore, it is difficult to obtain a high-quality γ-ray photographed image using such a γ-ray detector.

The present invention has been made in order to solve the above-mentioned problems of the prior art. The purpose of the present invention is to reduce the deterioration of the resolution and sensitivity of the peripheral portion, and to make the γ-ray incident surface with respect to the subject. An object of the present invention is to provide a γ-ray detector that can be made to be extremely close to each other.

[0006]

In order to achieve the above object, in a γ-ray detector of the present invention, a fiber shape is provided in each through hole of a collimator section in which a plurality of through holes are arranged in a grid pattern. Of a scintillator portion having a plastic scintillator inserted therein, and photoelectric conversion means for converting light generated in the plastic scintillator into an electric signal by incidence of γ-rays, and the shape of the γ-ray incident end face of the collimator portion is the object to be inspected. Of the plastic scintillator in each of the through-holes and the γ-ray incident surface of the collimator section are all equal to each other at a predetermined distance.

In the γ-ray detector, scintillator driving means may be provided for changing the distance between the γ-ray incident end face of the collimator section in the scintillator section and the subject by driving the scintillator section.

[0008]

In the γ-ray detector of the present invention having the above-mentioned structure, the γ-ray incident end face of the collimator section is formed into a contour shape along the body surface of the subject, and the γ-ray incident face of the plastic scintillator is formed. Since the distances from the γ-ray incident end surface of the collimator section are all equal to each other,
The entire γ-ray incident surface of the plastic scintillator also has a curved shape along the body surface of the subject, and the distance between the γ-ray incident end face of the collimator section and the γ-ray incident surface of the plastic scintillator with respect to the subject is the peripheral portion and the central portion. Are almost equal. Therefore, the deterioration of the resolution and sensitivity of the peripheral portion with respect to the central portion is reduced. In addition, this makes it possible to bring the γ-ray incident surface of the γ-ray detector significantly closer to the subject. As a result, it is possible to obtain a high quality γ-ray photographed image.

Further, by providing the scintillator portion driving means, the distance between the γ-ray incident end surface of the collimator portion and the γ-ray incident surface of the scintillator and the body surface of the subject is set to an appropriate distance according to the subject. can do.

[0010]

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

FIG. 1 is a sectional view showing the construction of a γ-ray detector according to an embodiment of the present invention, and FIG. 2 is a side view of the γ-ray detector.
In these drawings, reference numeral 1 denotes a γ-ray detector of two scintillation cameras provided in the SPECT apparatus, and as shown in FIG. 1, a lead-made detector having a large number of through holes 12A arranged in a grid pattern is formed. A scintillator portion 4 formed by inserting a fibrous plastic scintillator 3 into each through hole 2A of the collimator portion 2 and a position-sensitive PMT (photomultiplier tube) 6 as photoelectric conversion means are provided. The plastic scintillator 3 may have a structure in which a plurality of fiber strands are bundled. The collimator unit 2 and the plastic scintillator 3 are housed in a box-shaped shield member 5, and the PMT 6 is coupled to the back surface of the scintillator unit 4 (the surface opposite to the γ-ray incident surface). The PMT 6 is optically connected to each of the plastic scintillators 3 described above. Further, as shown in FIG. 2, the γ-ray detector 1 has a width that is somewhat large in the body axis direction of the subject P (direction of arrow a).

In the present embodiment, the shape of the γ-ray incident end surface of each collimator portion 2 is a curved surface shape along the body surface of the subject P. That is, in the present embodiment, the cross-sectional shape of the subject P is substantially annular, so each collimator unit 2
The shape of the γ-ray incident end face of No. 3 is not a concave shape corresponding to this. Further, since the distances between the γ-incident surface of the plastic scintillator 3 and the γ-ray incident end surface of the collimator section 2 in each through hole 2A are all set to the same predetermined distance, the shape of the entire γ-ray incident surface of the plastic scintillator 3 is determined. Also the subject P
It has a concave shape along the body surface. The two γ-ray detectors 1 are arranged so as to face each other with their γ-ray incident faces facing each other, and the γ-ray incident end faces of these two collimator portions 2 form a substantially cylindrical space. .. During imaging, the subject P is placed between the two γ-ray detectors 1.

A drive section 7 is provided as a scintillator section drive means for driving the two γ-ray detectors 1 in the direction of arrow 6 shown in FIG. This drive unit 7
By driving the line detector 1 in the direction of arrow b, the distance between the γ-ray incident end face of the collimator unit 2 and the subject P is changed, and the γ-ray incident end face of the collimator unit 2 and the γ-ray incident of the plastic scintillator 3 are incident. The distance between the surface and the subject P can be set to an optimum distance.

At the time of imaging the subject P, the two γ-ray detectors 1 are rotated around the subject P in the direction of arrow c by a rotation driving unit (not shown). At the same time, γ-rays emitted from RI previously administered to the subject P enter the plastic scintillator 3 of each γ-ray detector 1. When light is generated in the plastic scintillator 3 by the incidence of γ rays,
The PMT 6 performs photoelectric conversion and generates an electric signal. SP
An information processing unit (not shown) of the ECT apparatus obtains information on the distribution of RI within the subject P based on this electric signal, and creates a γ-ray image of the subject P according to this information. This γ-ray photographed image is displayed by a display means such as a CRT display (not shown).

In the γ-ray detector 1 of this embodiment, the shapes of the γ-ray incident end face of the collimator section 2 and the γ-ray incident face of the plastic scintillator 3 are the same as described above.
Since it has a concave shape along the body surface, the distance between the γ-ray incident cross section of the collimator unit 2 and the γ-ray incident surface of the plastic scintillator 3 with respect to the subject P is equal to the distance at the central portion L1 of the γ-ray detector 1. The difference from the distance in the peripheral portion L2 is greatly reduced compared to the conventional case. Therefore,
Degradation of resolution and sensitivity of the peripheral portion L2 with respect to the central portion L1 is reduced, and imaging can be performed with the γ-ray incident surface of the γ-ray detector 1 being significantly close to the subject P. As a result, it is possible to obtain a high quality γ-ray photographed image. Here, in the present embodiment, since a plurality of fiber-shaped plastic scintillators 3 are used, by designing so that the average light emitting distance to the plastic scintillators 3 is sufficiently shorter than the shortest length of the plastic scintillators 3, the central portion Even if the thickness (length) of the plastic scintillator 3 is different between L1 and the peripheral portion L2, a difference in sensitivity due to the thickness of both portions does not easily occur.

Further, in this embodiment, since the PMT 6 is excellent in position resolution, it is possible to secure the position resolution only by the hole diameter of each through hole 2A of the collimator section 2.
Therefore, it is possible to directly detect in which of the plastic scintillators 3 the event of the generated scintillation occurs with high resolution (around FWHM 4 mm) by the PMT 6.

Moreover, the plastic scintillator 3 is
Since it is inserted and arranged in each through hole 2A of the collimator unit 2, the Compton scattering component is absorbed by the lead wall around the through hole 2A, whereby the Compton scattering in the γ-ray detector 1 is drastically reduced. , And can contribute to the improvement of the image quality of the γ-ray photographed image.

Further, the attenuation rate of the scintillation light of the plastic scintillator 3 is extremely short as compared with that of NaI or the like conventionally used as a scintillator,
The effect of improving the maximum counting characteristic can also be obtained.

The embodiment of the present invention has been described above.
The present invention is not limited to this, and various modifications can be made. For example, in the above embodiment, SPEC
Although the γ-ray detector of the T apparatus is taken as an example, it can be applied to a γ-ray detector of a γ-ray imaging apparatus that performs whole body collection. Further, in the above embodiment, the two γ-ray detectors 1
However, the present invention can be applied to a case where only one γ-ray detector is used or a case where three or more γ-ray detectors are combined, and the γ-ray detector is applied to the subject. It can also be applied to the case where γ-ray imaging is performed in a stationary state. Furthermore, the shapes of the γ-ray incident end surface of the collimator section and the γ-ray incident surface of the plastic scintillator are not limited to the concave shape as in the above embodiment, but can be any shape according to the subject.

Further, instead of the fiber-shaped plastic scintillator inserted and arranged in each core of the collimator section, γ
As a scintillator element for converting a line into light, a single crystal such as NaI, BGO, or CWO is cut into a hexagon, a circle, or a quadrangle as shown in FIG. 3, and the outer surface (excluding the PMT mounting surface) is cut. It is possible to insert and arrange a product coated with a reflecting agent (white painting). In this case, it becomes possible to construct a detector having a high γ-ray stopping effect and a high sensitivity in a shorter distance. However, since NaI has a disintegrating property, it needs to be sealed so as not to come into contact with the outside air after being inserted into the collimator portion. BGO and CWO do not need to be hermetically sealed because they have no smelting property. The method of cutting the single crystal may be shearing, laser light processing, wire electric discharge machining, or the like.

[0021]

The γ-ray detector of the present invention has the above-mentioned structure and action, and the deterioration of the resolution and sensitivity of the peripheral portion thereof is reduced, and the γ-ray incident surface is made extremely close to the subject. be able to. As a result, it is possible to improve the image quality of the gamma ray photographed image obtained using this gamma ray detector.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a γ-ray detector according to an embodiment of the present invention.

FIG. 2 is a side view of the γ-ray detector.

FIG. 3 is a perspective view showing a main configuration of a γ-ray detector according to another embodiment of the present invention.

FIG. 4 is a diagram showing a conventional γ-ray detector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 γ detector 2 Collimator section 2A Through hole 3 Plastic scintillator 4 Scintillator section 5 Shield member 6 PMT (photoelectric conversion means) 7 Driving section (scintillator section driving means) P Subject

Claims (2)

[Claims] 1. A scintillator section in which a fibrous plastic scintillator is inserted into each through hole of a collimator section in which a plurality of through holes are arranged in a grid pattern, and light generated by the plastic scintillator upon incidence of γ rays. And a photoelectric conversion means for converting into an electric signal, the shape of the γ-ray incident end face of the collimator portion is a curved shape along the body surface of the subject, and the γ-ray incident surface of the plastic scintillator in each through hole and A γ-ray detector characterized in that all distances from the γ-ray incident surface of the collimator section are equal to each other. 2. A gamma ray detector comprising a scintillator portion driving means for driving the scintillator portion to change the distance between the γ ray incident end face of the collimator portion in the scintillator portion and the subject.