The gamma ray produced by annihilation effect of positive and negative electrons is transformed into visible photon by scintillating crystal, and the visible photon is detected by photoelectric detector to realize the measurement of high energy gamma ray. The detector module based on scintillating crystal is the basic unit of PET equipment, and it is the key to determine the imaging quality of the whole equipment.
LYSO (yttrium praseodymium silicate, chemical formula: Lu 2 (1-a-b) Y2aSiO 5: Ce2b, where a = 0-20%, B = 0-0.2%) is a cerium ion-doped Lutetium-based silicate scintillation crystal. It is considered to be the best inorganic scintillating crystal material with high density, high light output and short attenuation time. It is the most ideal scintillating crystal material in the positron emission computed tomography diagnostic device (PET) of large nuclear medical equipment.
At present, Cz and u-PD crystal growth equipments have been successfully developed by the scintillation crystal group in the laboratory. They have been put into crystal growth and related research. Large size and high performance LYSO crystals (Fig. 1) and a new generation of fast decay time LYSO crystals (Fig. 2) have been developed by Czochralski method. The non-uniformity of large size LYSO crystal from beginning to end decreases to 5.4%, and the utilization ratio of LYSO crystal increases from 50% to more than 90% (Fig. 3). The fluorescence attenuation time of LYSO crystal is reduced to 31.3ns, which meets the application requirements of the new generation TOF-PET detector (Fig. 4).
Through cooperation with Changchun Yinghua Institute and Ganzhou Rare Earth Longnan Co., Ltd., the enterprise standard of lutetium oxide for crystals has been established, and the large-scale production of lutetium oxide has been realized, which provides the key material basis for domestic PET-CT manufacturing.
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