1、Key materials
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 photoelectricdetector 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 todetermine 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 (Fig. 1). Large size and high performance LYSO crystals (Fig. 2) and a new generation of fast decay time LYSO crystals (Fig. 3) 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. 4). 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. 5).
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.
2、Core device
Silicon Photomultiplier (SiPM) is a new type of high performance semiconductor photoelectric sensor. Its structure is composed of several identical pixels in parallel. Each pixel is composed of avalanche photodiodes and quenching resistors working in Geiger mode in series. Its function is to detect optical signals and convert them into electrical signals.
It has more advantages compared with traditional photomultiplier tube (PMT) and avalanche photodiode (APD). SiPM has low operating voltage (< 100V), high gain, fast response (ns level), high detection efficiency, compact structure, easy readout and large-scale array fabrication. Each APD unit operates in the counting mode, without gain fluctuation and over noise like linear mode APD, and has better single photon resolution than PMT. It has the potential to replace the traditional photomultiplier tube in the detection of single photon or very weak light signal.
New type of SiPM independently researched and developed by the lab has the characteristics of sub-nanosecond response speed, single photon sensitivity and low noise. The overall performance of the products have reached the international top-ranking level.
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3、Key component
Digital PET Detector Module
Digital PET detector is an advanced scintillation detector that directly outputs digital pulses. By utilizing digital signal processing (DSP) the Digital PET BDM creates a new class of nuclear imaging technology.
New Digital Sampling Technology
PETLab pioneers a new digital sampling technology that directly digitizes ultra-high-speed pulse signals and innovates the traditional "real-time sampling" method.
One Platform
Multiple Possibilities
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High resolution Imaging
4、System integration
Animal all-digital PET
Animal PET has irreplaceable value in the mechanism research, treatment, and drug development for tumors and major diseases of the nervous and cardiac system, but its great application potential is limited by the performance of the instrument.Analog PET and semi-digital PET suffer from uncertainty, difficulty of use, and narrow applications.
In 2010, the team completed the world's first animal all-digital PET.It was granted “First Prize of Hubei Province Technological Invention Award” in December, 2013.Animal all-digital PET achieved the breakthrough, who’s spacial resolution of 1.0 mm reached the intrinsic resolution（Fig.1）.
As a scientific instrument for basic biological research, animal digital PET products have undergone four iterations so far (Fig. 2). It has cooperated with well-known universities, scientific research institutes and hospitals at home and abroad in disease research and new drug development in the fields of brain diseases, tumors, cardiovascular diseases, metabolism and so on. The research results have been published in authoritative academic journals in the industry (Fig. 3).
Fig.1all-digital PET
Fig.2：Animal all-digital PET
Fig.3：A large number of scientific research achievements based on animal all-digital PET were published in authoritative journals.
Clinical all-digital PET
In 2015, the team completed the world's first clinical all-digital PET (Fig. 1). As the most important medical molecular imaging equipment in clinical diagnosis, clinical all-digital PET has a spatial resolution of 2.0 mm, a temporal resolution of 350 PS and a sensitivity of more than 1.50%. It has excellent performance and can detect smaller lesion size in shorter scanning time.
In January 2018, clinical all-digital PET/CT passed the Special Approval Procedure for the Innovation Medical Devices. In July, clinical trials were performed in the First Affiliated Hospital of Sun Yat-sen University and the Affiliated Tumor Hospital (Fig. 2 and 3). Clinical all-digital PET/CT was granted “Medical Device Registration Certificate”from CFDA on May 31, 2019 (Fig 4).
Focusing on all digital PET, the team has applied for, disclosed and authorized more than 400 patents, of which invention patents account for more than 70%, covering China, the United States, Japan, the European Union, Africa and other countries or regions. The research covers the whole innovation chain from key materials, core devices to system integration and application research.
5、Application demonstration
Based on the animal all-digital PET , the team has cooperated with well-known universities, scientific research institutes and hospitals at home and abroad in disease research and new drug development in the fields of brain diseases, tumors, cardiovascular diseases, metabolism and so on. The research results have been published in authoritative academic journals in the industry.（Nature Medicine, vol. 23, pp 742–752, 2017；Nature Medicine, vol. 23, pp 439-449, 2017；American Journal of Respiratory and Critical Care Medicine, vol. 189, No. 6, 2014；European Journal of Nuclear Medicine and Molecular Imaging , 2015 Aug 11；Physics in Medicine and Biology, vol. 60, No. 19, pp. 7779-7804, 2015；CNS Neuroscience & Therapeutics, 2016 ；Oncotarget，vol. 7, No.2, pp.2038-2053, 2016；Scientific Reports, vol. 6, No. 32935, 2016）。
The core advantage of digital PET is that it brings innovation in imaging methods and system designs. It can develop a large number of new PET systems for innovative applications, which can not be achieved by traditional PET. The team is using proton PET, brain PET and super PET to form innovative clusters, leading the development of new digital PET equipment, and constantly highlighting and improving the technical advantages of digital PET.
The team is also devoted to the establishment of a digital PET global application demonstration center, establishing a molecular imaging application platform with digital PET technology as the core.It is expected to produce world-class research results here.