JP2005249411A - Positron imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positron imaging system having high spatial resolution and little background and capable of accurately displaying the position of an affected part such as a tumor during operation. <P>SOLUTION: The positron imaging system 1 comprises a first scintillator 2 capable of detecting positions; a light guide 3 arranged in the rear of the first scintillator 2; a second scintillator 4 arranged in the periphery of the light guide 3; and a position-sensitive photomultiplier tube 5 arranged in the rear of the light guide 3. The first oscillator 2 is optically connected to a center part of the position-sensitive photomultiplier tube 5 via the light guide 3, and the second oscillator 4 is directly and optically connected to a peripheral part of the position-sensitive photomultiplier tube 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a nuclear medicine diagnostic apparatus, and more particularly to a positron imaging apparatus mainly used during surgery for tumor search and the like.

  For example, when imaging the distribution of positrons accumulated in a tumor, there are two methods. One is a method of detecting 511 keV gamma rays emitted when the positron is extinguished, and the other is a method of detecting the positron itself with a beta ray detector. Both of these conventional techniques simultaneously detect gamma rays from the periphery, resulting in an image with a high background, making it difficult to detect the exact position of the tumor and often difficult to use clinically.

There exists a scintillation detector described in patent document 1 as what solves this subject. The detector described in Document 1 includes two types of scintillators with different emission decay times, which are sequentially connected to the photodetector and the signal processing device.
JP 2002-48869 A

  Although the scintillation detector described in Patent Document 1 can detect positrons, it cannot display the image of the distribution of the positrons, and therefore cannot know the exact position of the tumor.

  In view of this problem, the invention according to the claims aims to provide a positron imaging device with high spatial resolution and low background, which can accurately display the position of an affected area such as a tumor during surgery. And

  The positron imaging apparatus according to claim 1 is a positron imaging apparatus for detecting a position of a positron emitting nuclide, wherein the scintillation light generated by the emitted positron and the scintillation light generated by annihilation gamma rays of the positron are independent of each other. And a scintillation detector that can output to each other, and a coincidence means for performing coincidence between the outputs.

  According to this apparatus, since simultaneous counting can be performed between the output obtained from the light emission due to the incidence of the positron and the light emission due to the incidence of the gamma ray emitted when the positron disappears, the scintillation light that has not been simultaneously counted is used as the background. Can be removed. That is, only the output due to the incidence of the positron can be position-calculated and displayed on the image. That is, a positron image with little background and high spatial resolution can be displayed.

  The positron imaging apparatus according to claim 2, wherein the scintillation detector includes a first scintillator capable of detecting a position, a light guide disposed behind the first scintillator, and a first scintillator disposed around the light guide. A second scintillator and a position-sensitive photomultiplier tube disposed behind the light guide, and the first scintillator is optically connected to the center of the position-sensitive photomultiplier tube via the light guide. The second scintillator is optically connected directly to the periphery of the position-sensitive photomultiplier tube.

According to this apparatus, the invention described in claim 1 can be realized with a simple configuration. The operation is as follows.
When the positron is incident on the first scintillator, the positron loses energy and generates two oppositely directed gamma rays, one of which is incident on the second scintillator placed around the rear light guide. . The scintillation light generated in the first scintillator is guided to the center of the position-sensitive photomultiplier tube by the light guide, and the scintillation light generated in the second scintillator is directly applied to the position-sensitive photomultiplier. Incident on the periphery of the tube. As a result, the two scintillation lights by the positron and its annihilation gamma rays do not overlap and can be extracted as independent outputs, so that only the positron can be imaged by performing simultaneous counting. Since the first scintillator can detect the position and the photomultiplier tube is also a position-sensitive type, the spatial resolution of the positron distribution image can be increased by performing position calculation.
In addition, since this apparatus uses one position-sensitive photomultiplier tube for two scintillators, it can be configured compactly and inexpensively and is easy to handle during the operation.

  As in the positron imaging device according to claim 3, it is preferable that the position-sensitive photomultiplier tube is a multi-channel type. This is because the scintillation light from the two scintillators is incident on separate channels of the position-sensitive photomultiplier tube, so that an independent output can be reliably obtained.

As described in claim 4, it is also very preferable to use a plastic scintillator or a flake type inorganic scintillator as the first scintillator and use GSO or BGO as the second scintillator.
The plastic scintillator or the flake-type inorganic scintillator used as the first scintillator has a low detection efficiency of gamma rays that become a background, and is convenient for detection of beta rays (positrons). Further, GSO (gadolinium silicate, Gd ₂ SiO ₅ ) or BGO (bismuth germanate, Bi ₄ Ge ₃ O ₁₂ ), which is the second scintillator, has high gamma ray detection efficiency, so that good sensitivity can be obtained.

  Since the positron imaging apparatus according to the first aspect has a small background and can display a positron image with high spatial resolution, the position of a tumor or the like can be accurately detected during the operation.

  The device according to claim 2 shows the effect of claim 1 with a simple configuration, is compact and easy to handle during the operation.

The apparatus according to claim 3 can display an image with high spatial resolution.
The device according to claim 4 exhibits particularly good sensitivity.

An example of an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram of a positron imaging device 1. The positron imaging apparatus 1 includes the following parts. That is, the first scintillator 2 capable of detecting the position, the light guide 3 disposed behind the first scintillator 2, the second scintillator 4 disposed along the outer peripheral surface of the light guide 3, the light guide 3 and the second A position sensitive photomultiplier tube 5 optically coupled to both of the scintillators 4, a position calculation circuit 6 for calculating the position of the output of the first scintillator 2, the outputs of the first scintillator 2 and the outputs of the second scintillator 4. A coincidence counting circuit 7 for simultaneously counting images, a display mechanism 8 for displaying images, and the like. The light guide 3 is optically connected to the central portion of the position-sensitive photomultiplier tube 5, and the second scintillator 4 is optically connected to the peripheral portion thereof. Reference numeral 7 a in the figure is a detector that receives an output from the peripheral portion of the photomultiplier tube 5.

  Positron A released from a positron emitting nuclide such as F-18-FDG (fluorodeoxyglucose) administered to a patient as a radiopharmaceutical is detected by the first scintillator 2 and loses energy. Positron A that has lost its energy combines nearby electrons and emits two 511 keV gamma rays B in opposite directions. One of these gamma rays B is detected by the second scintillator 4. In this case, since the first scintillator 2 and the second scintillator 4 emit light simultaneously, only the positron A can be detected by simultaneous counting by the coincidence counting circuit 7.

  The light emitted from the first scintillator 2 is guided to the center of the photomultiplier tube 5 by the light guide 3, and the center of gravity is calculated by the position calculation circuit 6. The position information is displayed by the display mechanism 8. On the other hand, the light emitted from the second scintillator 4 is directly incident on the peripheral edge of the photomultiplier tube 5.

  In order to make it possible to detect the outputs of the first scintillator 2 and the second scintillator 4 as independent signals, the position sensitive photomultiplier tube 5 is preferably a multi-channel type. That is, the output of the first scintillator 2 is incident on the central portion of the multichannel photomultiplier tube 5 through the light guide 3, and the output from the central channel is calculated by calculating the center of gravity. In addition to being used for position calculation, all signals are added and guided to the coincidence counting circuit 7. The light emitted from the second scintillator 4 is incident on the peripheral portion of the multichannel photomultiplier tube 5, and the output of the peripheral channel is guided to the coincidence circuit 7.

  Gamma rays other than those caused by positron A incident on the first scintillator 2 among the 511 keV gamma rays detected by the first scintillator 2 and the gamma rays detected by the second scintillator 4, which were conventionally counted as the background, Since they are detected individually, they are removed by the coincidence circuit 7.

  In this way, the distribution of only the positron A incident on the first scintillator 2 is displayed as an image on the display mechanism 8.

  Since the first scintillator 2 is intended to detect beta rays, a plastic scintillator with low gamma ray detection efficiency or an inorganic scintillator processed extremely thinly is desirable. As the second scintillator 4, GSO or BGO having high gamma ray detection efficiency is preferable.

  However, the scintillator is not limited to the plastic scintillator and GSO or BGO. Further, a photodetector other than the position sensitive photomultiplier tube may be used.

It is a conceptual diagram which shows the positron imaging device 1 of invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positron imaging device 2 1st scintillator 3 Light guide 4 2nd scintillator 5 Position sensitive photomultiplier tube 6 Position calculation circuit 7 Simultaneous counting circuit 8 Display mechanism A Positron B Gamma ray

Claims (4)

A positron imaging device for position detection of positron emitting nuclides, comprising:
It has a scintillation detector that can output the emitted scintillation light by the positron and the scintillation light by the annihilation gamma ray of the positron independently of each other, and a coincidence means for performing coincidence between the respective outputs Positron imaging device.   The scintillation detector is disposed behind the light guide, the first scintillator capable of detecting the position, the light guide disposed behind the first scintillator, the second scintillator disposed around the light guide, and the light guide. The first scintillator is optically connected to the central portion of the position sensitive photomultiplier tube via a light guide, and the second scintillator is 2. The positron imaging apparatus according to claim 1, wherein the positron imaging apparatus is directly optically connected to a peripheral portion of the sensitive photomultiplier tube.   3. The positron imaging apparatus according to claim 2, wherein the position-sensitive photomultiplier tube is a multi-channel type. 4. The positron imaging apparatus according to claim 2, wherein a plastic scintillator or a flake type inorganic scintillator is used as the first scintillator, and GSO or BGO is used as the second scintillator.

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