JPH04328485A - Scintillation camera - Google Patents

Abstract

PURPOSE:To obtain a scintillation camera whose positional resolution is improved sharply and whose detector system can be replaced easily in accordance with a use. CONSTITUTION:A collimator element 1, a fiber-containing collimator element 2 into which a plastic scintillator 7 is inserted and position-sensitive PMT 3 are provided. Each of these elements is made separable and replaceable corresponding to each of system sensitivity, resolution and collected nuclide energy.

Description

[Detailed description of the invention]

[Object of the invention]

0002

[Industrial Application Field] 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 in the subject based on this detection signal. Regarding scintillation cameras used for
In particular, it relates to improvements in gamma ray detectors.

0003

2. Description of the Related Art Conventionally, a gamma ray detector applied to this type of scintillation camera detects RI which has been administered to a subject.
The gamma rays emitted from the scintillator are selectively passed through the collimator section and made incident on the scintillator, where the scintillator converts them into light, which then photoelectrically converts them through photomultiplier tubes arranged densely on the scintillator. and,
After converting each photomultiplier tube into an electrical signal using a preamplifier, weighting calculations were performed for each output to detect the position of scintillation and derive the energy value.

0004

[Problems to be Solved by the Invention] However, in the case of conventional scintillation cameras of this kind, the positional resolution of the detector is not very good at FWHM 3 to 4 mm, and furthermore, a collimator for making γ-rays incident on the detector is not very good. The positional resolution of the area is even worse. Therefore, the positional resolution of the entire system depends on the positional resolution of the collimator itself, and can only be achieved at a maximum FWHM of around 8 mm. In addition, Compton scattering within the detector (scintillator) becomes a problem, which leads to further deterioration of the positional resolution.

[0005] Furthermore, there has been no detector system that allows the detector system to be replaced depending on the application. The present invention has been made with attention to such problems, and its purpose is to:
It is an object of the present invention to provide a scintillation camera whose positional resolution is greatly improved compared to the conventional one and whose detector system can be easily replaced depending on the application.

[Configuration of the invention]

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a collimator section in which a large number of cores are arranged in a grid pattern, and a collimator section installed directly below the collimator section; A casing having the same structure as , a fiber-containing collimator section consisting of a fiber-shaped plastic scintillator inserted into each core of the casing, and a fiber-containing collimator section installed directly below the fiber-containing collimator section or via a light guide, Further, it is equipped with a photoelectric conversion imaging section capable of detecting the incident position of the γ rays in the collimator section, and is made to be able to be separated and replaced for each section according to the system sensitivity, resolution, and collected nuclide energy. Features.

[0008]

[Operation] With the configuration of the scintillation camera according to the present invention, the γ
The rays are converted into light by the fiber-containing collimator section, and are incident on the photoelectric conversion imaging section. When the rays are photoelectrically converted in the photoelectric conversion imaging section, the incident position of the gamma rays is detected. A position-sensitive PMT (photomultiplier tube) that can be applied as a photoelectric conversion imaging section is a well-known one, and has a position resolution of 1 mm or less. The hole diameter is 1m
It is about m to 2 mm. Therefore, the positional resolution can be ensured only by the hole diameter of the core of the collimator section and the fiber-containing collimator section, and a positional resolution of around 4 mm FWHM can be achieved.

Furthermore, since the gamma rays selectively passed by the collimator section are incident on the fiber-containing collimator section, Compton scattering near the incident surface of the plastic scintillator is suppressed, and moreover, the lead wall of the core of the fiber-containing collimator section Compton scattering is absorbed by

[0010] Therefore, the positional resolution of the detector, which is composed of the collimator, the fiber-containing collimator section, and the photoelectric conversion imaging section as main parts, is greatly improved compared to the conventional one.

[0011] Furthermore, the collimator section, the fiber-containing collimator section, and the photoelectric conversion imaging section can be separated and replaced depending on the system sensitivity, resolution, and collected nuclide energy. optimal sensitivity,
Capable of resolution and energy collection.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram schematically showing the main parts of a scintillation camera according to a first embodiment of the present invention.

This scintillation camera includes a collimator section 1, a fiber-containing collimator section 2, and a position-sensitive PMT 3 as essential parts of the detector. The collimator section 1 includes a large number of cores 4 arranged in a grid pattern, as shown in a partially enlarged view in FIG. The fiber-containing collimator section 2 is located directly below the collimator section 1 and consists of a casing 5 having the same structure as the collimator section 1 and a plastic scintillator 7 inserted into each core 6 of the casing 5. . PMT3 is
It is installed directly under the fiber-containing collimator section 2 and is optically coupled to each plastic scintillator of the fiber-containing collimator section 2, so that the γ in the collimator section 1
It is possible to detect the incident position of the line. Although the plastic scintillator 7 has a hexagonal cross-section, it can be easily molded into a round or square cross-section. The core 6 of the collimator section 2 may have a cross-sectional shape compatible with a plastic scintillator. Furthermore, the structure of the plastic scintillator 7 may be obtained by bundling a plurality of fiber strands.

Furthermore, in order to enable the collimator section 1, the fiber-containing collimator section 2, and the PMT 3 to be separated and replaced depending on the system sensitivity, resolution, and collected nuclide energy, a shield structure 8 and a flange 9 are used. ，
10 and is tightened and fixed with a mounting screw 11. In addition, in FIG. 1, 12 is a position calculation circuit, 13
is a high voltage generator, 14 is a switch unit, 15 is a power supply, 16
is a screw tightening sensor.

As mentioned above, when each plastic scintillator 7 of the fiber-containing collimator section 2 and the position-sensitive PMT 3 are optically coupled, since the position resolution of the PMT 4 is excellent, each plastic scintillator 7 of the fiber-containing collimator section 2 Positional resolution can be ensured only by the hole diameter of the child 6. Therefore, it is possible to directly determine in which scintillation event occurred in each plastic scintillator 7 with high resolution (FWHM 4 mm).
(before and after) can be detected.

Furthermore, since the structure is such that the gamma rays selectively passed through the collimator section 1 are incident on the fiber-containing collimator section 2, Compton scattering near the incident surface of the plastic scintillator 7 is suppressed. Furthermore, since the plastic scintillator 7 is inserted into each core 6 of the fiber-containing collimator section 2, the Compton scattered components are absorbed by the lead walls of the cores 6.

Therefore, the position signal and energy signal of the generated scintillation obtained by the position calculation circuit 12 based on the detection signal of the PMT 3 are less affected by Compton scattering, and the image quality is improved.

Furthermore, the shield structure 8 and the flanges 9, 1
For example, when the fiber-incorporated collimator part 2 is removed from a state in which the collimator part 1, the fiber-incorporated collimator part 2, and the PMT 3 are held by tightening and fixing them with the mounting screws 11, light enters the PMT 3 directly. At this time, in this embodiment, the screw tightening sensor 16 detects that the fiber-containing collimator section 2 has been removed, and this detection signal is applied to the switch section 14 to stop the power supply from the power source 15 to the high voltage generation section 13. I decided to turn it off. Note that a door switch, a photo sensor, or the like can be used as the screw tightening sensor 16. In this way, by creating a structure in which the collimator part 1, the fiber-incorporated collimator part 2, and the PMT 3 are separated and replaceable, it is possible to collect low energy such as 201 Tl and collect high energy such as 67 Ga by entering the fiber. The collimator section 2 can be replaced as appropriate, and the collimator section 1 can be easily selected to obtain sensitivity and resolution according to the acquisition mode.

In the first embodiment described above, the PMT 3 was installed directly below the fiber-containing collimator section 2, but as in the configuration of the second embodiment shown in FIG. An optical connection configuration may be adopted in which a two-dimensional fiber array 17 is interposed as a light guide between the PMT 3 and the collimator section 1 and the fiber-containing collimator section 2. We can respond to your requests.

Furthermore, as in the configuration of the third embodiment shown in FIG.
An optical connection configuration may be adopted in which a two-dimensional condensing fiber array 18 is interposed as a light guide between the collimator section and the collimator section 3, which has a more expanded effective field of view. Detection of the γ-ray incident position can be performed using a smaller PMT.

Furthermore, instead of the fiber-shaped plastic scintillator inserted into each core of the collimator section, γ
As a scintillator element that converts a line into light, a single crystal such as NaI, BGO, or CWO is cut into a hexagonal, round, or square shape as shown in Figure 5, and the outer surface (
However, it is possible to insert and arrange a reflector coated (white painting) on the PMT mounting surface (excluding the PMT mounting surface). In this case, it is possible to construct a detector that has a gamma ray stopping effect over a shorter distance and has high sensitivity. However, in the case of NaI, due to its comprehensibility,
After inserting it into the collimator, it must be sealed to prevent it from coming into contact with the outside air. BGO and CWO do not need to be sealed because they are not collapsible. Note that as methods for cutting the single crystal, shirring processing, processing using laser light, wire electric discharge processing, etc. can be considered.

[0022]

[Effects of the Invention] As explained above, according to the present invention, the detection of the gamma ray incident position and the derivation of the energy value are performed by a detector whose main parts include a collimator section with two fibers and a photoelectric conversion imaging section. Therefore, the position resolution is significantly improved compared to the conventional method. Moreover, since each of the above parts can be separated and replaced, the detector system can be replaced depending on the application by replacing the collimator part and the fiber-containing collimator part.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram schematically showing main parts of a scintillation camera according to a first embodiment of the present invention.

FIG. 2 is a structural explanatory diagram of a collimator section.

FIG. 3 is a perspective view showing the appearance of a detector of a scintillation camera according to a second embodiment of the present invention.

FIG. 4 is a perspective view showing the appearance of a detector of a scintillation camera according to a third embodiment of the present invention.

FIG. 5 is an explanatory diagram of a main part of a detector in a scintillation camera according to a fourth embodiment of the present invention.

[Explanation of symbols]

1 Collimator section 2 Fiber-containing collimator section 3 PMT 4 Core 5 Housing 6 Core 7 Plastic scintillator 8　Shield structure 9 Flange 10 Flange 11 Mounting screw 12 Position calculation circuit 13 High voltage generation section 14 Switch part 15 Power supply 16 Screw tightening sensor 17 Fiber array 18 Fiber array

Claims (1)

[Claims] Claim 1: A collimator section in which a large number of cores are arranged in a grid pattern, and a collimator section installed directly below the collimator section,
In addition, a casing having the same structure as the collimator section, a fiber-containing collimator section consisting of a fiber-shaped plastic scintillator inserted into each core of the casing, and a fiber-containing collimator section directly below the fiber-containing collimator section or via a light guide. and a photoelectric conversion imaging unit that is installed at the collimator unit and can detect the incident position of the γ-ray at the collimator unit, and each unit can be separated and replaced in accordance with system sensitivity, resolution, and collected nuclide energy. A scintillation camera characterized by: