Inorganic Scintillator and Process for its Fabrication

a technology of inorganic scintillators and fabrication processes, which is applied in the direction of polycrystalline material growth, crystal growth process, gel state, etc., can solve the problems of low fluorescence intensity output from the scintillator, insufficient energy time resolution, and considerable noise generation of siosub>5/sub>, so as to reduce the detection precision of charged particles, the effect of low energy time resolution and low fluorescence intensity outpu

Inactive Publication Date: 2007-12-20
KURASHIGE KAZUHISA +5
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  • Abstract
  • Description
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Benefits of technology

[0011] However, when the present inventors conducted a detailed examination of conventional inorganic scintillators including those described in the aforementioned publications, it was found that the inorganic scintillator described in Japanese Examined Patent Publication No. 62-8472 composed of CeαGd2-αSiO5 has a slow rise in fluorescence (fluorescent intensity) output from the scintillator after radiation absorption, and therefore the energy time resolution is insufficiently high. Also, it has been demonstrated that the scintillator composed of CeαLu2-αSiO5 generates considerable noise in the fluorescence outputted upon incidence of charged particles from a subject. This noise lowers the detection precision of the charged particles from the subject.
[0020] The inorganic scintillator of the invention has a very short fluorescent rise time of no greater than 2 nanoseconds, thus allowing the object stated above to be achieved, while the workability also tends to be superior, with greater resistance to cracking during polishing, for example, as compared to scintillators with crystals belonging to P21 / c or scintillators wherein {ALu / (ALu+AGd)} is 0.50 or greater.
[0032] According to the invention, it is possible to provide an inorganic scintillator having an adequately rapid rise time for fluorescence outputted upon absorption of radiation and sufficiently reduced fluorescent noise, as well as a process for its fabrication.

Problems solved by technology

However, when the present inventors conducted a detailed examination of conventional inorganic scintillators including those described in the aforementioned publications, it was found that the inorganic scintillator described in Japanese Examined Patent Publication No. 62-8472 composed of CeαGd2-αSiO5 has a slow rise in fluorescence (fluorescent intensity) output from the scintillator after radiation absorption, and therefore the energy time resolution is insufficiently high.
Also, it has been demonstrated that the scintillator composed of CeαLu2-αSiO5 generates considerable noise in the fluorescence outputted upon incidence of charged particles from a subject.
This noise lowers the detection precision of the charged particles from the subject.
It has also been shown that the scintillator described in Japanese Patent Application Laid-Open No. 2001-524163 does not permit adequate reduction in the noise effect even when Ta, W, Ca and F are included.

Method used

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  • Inorganic Scintillator and Process for its Fabrication
  • Inorganic Scintillator and Process for its Fabrication

Examples

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example 1

[0077] In an Ir crucible having the same shape shown in FIG. 3 with a diameter of 50 mm, a height of 50 mm and a thickness of 1.5 mm there were loaded 316.84 g of gadolinium oxide (Gd2O3, 99.99 wt % purity), 87.06 g of lutetium oxide (Lu2O3, 99.99 wt % purity), 65.73 g of silicon dioxide (SiO2, 99.99 wt % purity) and 0.38 g of cerium oxide (CeO2, 99.99 wt % purity) as the starting materials, and 470.01 g of the mixture was obtained. The mixture was then heated to melting at 1950° C. or higher in a high-frequency induction heating furnace to obtain a melt (chemical composition of melt: Ce0.002Lu0.4Gd1.598SiO5) (melting step).

[0078] Next, the end of the lifting rod to which the seed crystal was anchored was placed in the melt for crystal growth. The seed crystal used was a cut-out single crystal composed of a metal oxide containing Ce0.002Lu0.4Gd1.598SiO5, obtained by an ordinary crystal growth method. After growth of the single crystal and before its cutting (trimming), the crystal ...

example 2

[0085] In an Ir crucible having the same shape shown in FIG. 2 with a diameter of 50 mm, a height of 50 mm and a thickness of 1.5 mm there were loaded 262.67 g of gadolinium oxide (Gd2O3, 99.99 wt % purity), 124.02 g of lutetium oxide (Lu2O3, 99.99 wt % purity), 62.42 g of silicon dioxide (SiO2, 99.99 wt % purity) and 0.89 g of cerium oxide (CeO2, 99.99 wt % purity) as the starting materials, and 450.00 g of the mixture was obtained. The mixture was then heated to melting at 1950° C. or higher in a high-frequency induction heating furnace to obtain a melt (chemical composition of melt: Ce0.005Lu0.6Gd1.395SiO5) (melting step).

[0086] Next, the end of the lifting rod to which the seed crystal was anchored was placed in the melt for crystal growth. The seed crystal used was a cut-out single crystal composed of a metal oxide containing Ce0.005Lu0.6Gd1.395SiO5, obtained by an ordinary crystal growth method. After growth of the single crystal and before its cutting (trimming), the crystal...

example 3

[0092] In an Ir crucible having the same shape shown in FIG. 2 with a diameter of 50 mm, a height of 50 mm and a thickness of 1.5 mm there were loaded 273.54 g of gadolinium oxide (Gd2O3, 99.99 wt % purity), 86.10 g of lutetium oxide (Lu2O3, 99.99 wt % purity), 24.43 g of yttrium oxide (Y2O3, 99.99 wt % purity), 65.00 g of silicon dioxide (SiO2, 99.99 wt % purity) and 0.93 g of cerium oxide (CeO2, 99.99 wt % purity) as the starting materials, and 450.00 g of the mixture was obtained. The mixture was then heated to melting at 1950° C. or higher in a high-frequency induction heating furnace to obtain a melt (chemical composition of melt: Ce0.005Y0.2Lu0.4Gd1.395SiO5) (melting step).

[0093] Next, the end of the lifting rod to which the seed crystal was anchored was placed in the melt for crystal growth. The seed crystal used was a cut-out single crystal composed of a metal oxide containing Ce0.005Y0.2Lu0.4Gd1.395SiO5, obtained by an ordinary crystal growth method. After growth of the si...

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Abstract

The inorganic scintillator of the invention is an inorganic scintillator capable of producing scintillation by radiation, which is a crystal comprising a metal oxide containing Lu, Gd, Ce and Si and belonging to space group C2 / c monoclinic crystals, and which satisfies the condition specified by the following inequality (1A), wherein ALu represents the number of Lu atoms in the crystal and AGd represents the number of Gd atoms in the crystal. {ALu / (ALu+AGd)}<0.50  (1A)

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a divisional application of U.S. application Ser. No. 11 / 154,824, filed Jun. 17, 2005, the contents of which are incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an inorganic scintillator and to a process for its fabrication. [0004] 2. Related Background of the Invention [0005] In an apparatus used for Positron Emission (computed) Tomography (hereinafter, “PET”), the optical characteristics (wavelength conversion characteristics, etc.) of the scintillator mounted therein has a major effect on the imaging performance of the apparatus, and therefore improvement in the optical characteristics of the scintillator is the most important factor for enhancing the imaging performance of such apparatuses. Researchers are therefore actively exploring scintillator materials which can be used to construct scintillators with excellent optical chara...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C30B1/02
CPCC09K11/7774C30B29/22C30B15/00C09K11/77742
Inventor KURASHIGE, KAZUHISASHIMURA, NAOAKIISHIBASHI, HIROYUKISUMIYA, KEIJIUSUI, TATSUYASHIMIZU, SHIGENORI
Owner KURASHIGE KAZUHISA
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