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20 October 2022, Volume 35 Issue 5

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Preparation and Preliminary Imaging Evaluation of a Group of Novel Rapid 99mTc-Labeled Boric Acid Derivatives Tracers for Myocardial Perfusion Imaging

ZHANG Lixia, ZHANG Zongyao, ZHANG Hailong, HAN Kai, ZHAO Zuoquan, FANG Wei

2022, 35(5):  361-367.  DOI: 10.7538/tws.2021.youxian.057

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Nuclear cardiology plays an important role in management of cardiac patients with known or suspected coronary artery disease (CAD). CAD is the leading cause of premature death and permanent disability. Myocardial perfusion imaging (MPI) with radiotracers is a non-invasive technique that shows the heart function and the areas of perfusion defects. In order to evaluate perfusion defects accurately, the radiotracer used in MPI studies must be taken up into myocardium in proportion to the regional myocardial blood flow. At present, ^99mTc-TEBO is commonly used in clinic for rapid myocardial perfusion imaging, which has high initial uptake but poor myocardial retention, so it is necessary to optimize its structure. In this study, a group of novel ^99mTc-labeled rapid boric acid derivatives tracers for myocardial perfusion imaging, including ^99mTc-2SP,  ^99mTc-4LPA and ^99mTc-2MDM were prepared in this study. The preparation time of these tracers was 30 min, and all of them were colorless clear liquid. The radiochemical purity of the three tracers was > 95%, respectively. The above tracer agents were used to perform SPECT dynamic imaging in healthy miniature pigs and compared with ^99mTc-TEBO. After ^99mTc-TEBO injection, rapid uptake was shown in left ventricular myocardium within 0.5 min, but the myocardial radioactivity decreased rapidly to about 75% of the peak value and the ratio of the radioactivity between myocardium/blood pool was 1.63 at 10 min. Compared with ^99mTc-TEBO, ^99mTc-2SP had prolonged retention and slower elution in myocardium within 15 min after the injection when the 2-methylsulfonyl pyridine-5-boric acid group was introduced into the ^99mTc-2SP structure. The myocardial radioactivity still maintained 95% of the peak value, and the ratio of radioactivity between myocardium/blood pool was 3.75, which was significantly higher than that of ^99mTc-TEBO. However, the other two imaging agents ^99mTc-4LPA and ^99mTc-2MDM showed poor uptake in myocardium within 15 min after injection. In conclusion, ^99mTc-2SP was an ideal boric acid derivatives tracers for myocardial perfusion imaging and has prospect for clinical application in future.



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The Glioma Model micro-PET Imaging and Biodistribution of ⁶⁸Ga Labeled Fibroblast Activation Protein Inhibitor

XIANG Yili, ZHONG Xuan, FU Jingjing, WU Wenyu, SHAO Guoqiang, WANG Feng, ZHANG Jun

2022, 35(5):  368-375.  DOI: 10.7538/tws.2021.youxian.115

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To investigate the biodistribution and micro-PET imaging of ⁶⁸Ga labeled fibroblast activation protein inhibitor (⁶⁸Ga-FAPI-04) in normal mice and glioma nude mice, ⁶⁸Ga-FAPI-04 was synthesized using DOTA-modified fibroblast activation protein inhibitor as precursor. The synthesis yield, radiochemical purity and in vitro stability were analyzed by radio-HPLC, and the hydrophilicity of ⁶⁸Ga-FAPI-04 was evaluated by lipo-hydro partition coefficient. Twenty ICR mice were randomly divided into 5 groups. 3.7 MBq of ⁶⁸Ga-FAPI-04 was injected by tail vein per mouse, then the mice were killed at 5, 15, 30, 60, 120 min post-injection(pi.). The main organs and tissues were collected and weighed, then the radioactivity was measured, and the uptake of each tissue or organ was calculated. The nude mice bearing U87MG glioma model were established, then the biodistribution study and micro-PET imaging were performed. The results indicate that the synthesis yield of ⁶⁸Ga-FAPI-04 was (97.38±1.32)% (n=3), the radiochemical purity was 100%，and the in vitro stability and hydrophilicity were good. The biodistribution study of normal-ICR mice showed that 68Ga-FAPI-04 was cleared from blood rapidly and mainly excreted from kidneys, and the radioactivity uptake in brain was low. The biodistribution and micro-PET of U87MG tumor-bearing nude mice showed high radioactivity at the tumor targets. The uptake of ⁶⁸Ga-FAPI-04 at the tumor targets reached (2.50±0.00)%ID/g at 90 min pi. The tumor-to-background ratios (TBRs) were（6.26±0.09）, （5.06±0.02）, （5.54±1.47） and （5.51±0.03） at 30, 60, 90 and 120 min pi., respectively. The preliminary studies indicate that ⁶⁸Ga-FAPI-04 is synthesized easily with high yields, and is stable in vitro. The radiotracer was mainly excreted from kidneys, and targeting tumor targets with clear images in micro-PET of glioma models. Therefore, ⁶⁸Ga-FAPI-04 might be a potential brain tumor imaging agent.



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Radiation Information Process and Implement in a ⁶⁰Co Dual-projection Digital Radiography System

GUO Xiaojing, CONG Peng, CHEN Liu, SUN Yuewen

2022, 35(5):  376-381.  DOI: 10.7538/tws.2021.youxian.070

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The Tsinghua University successfully invented a dual-projection digital radiography system, which adopts two ⁶⁰Co radiation sources aiming at two patented high-pressure gas chamber array detectors respectively. The system can obtain both vertical and horizontal projections from one scan, providing more information for image examination. Comparing with traditional single-projection system, the dual-projection system adopts two ⁶⁰Co radiation sources that are deployed on the side and at the bottom respectively, but the adoption of two radiation sources also brings problems like γ photon scatter and more complicated radiation information process, and image processing algorithms needs improving to obtain radiation images of better quality. To solve the above-mentioned problems, this paper presents a comprehensive radiation information processing method, including correcting the photon scatter between two radiation sources, designing and implementing a radiation information processing and analyzing platform, and improving radiation image processing algorithms. This work has been applied in the system at a nuclear facility access for over two years and proved to be reliable, achieving application innovation among similar-type systems.



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Study on Preparation Process of Ni-63 Radioactive Sources by Electrodeposition

LUO Ting, SU Dongping, LIANG Banghong, LI Shuntao, ZHANG Jingsong, CHEN Yunming, GAN Quan, WU Lu, LUO Laoyong

2022, 35(5):  382-389.  DOI: 10.7538/tws.2021.youxian.078

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Nickel-63 radioactive sources used in micro nuclear batteries require high surface emissivity, thin coating and small substrate. The method for the preparation of nickel-63 radioactive sources by direct and constant current electrodeposition was established by using nickel-63 solution with small volume, high specific activity and low Ni²⁺ concentration as electrodeposition liquid.Using this method, under the conditions of copper substrate, Ni²⁺ concentration with 1 g/L, electrodeposition pH with 3.5-4.5 and sulphamic acid concentration with 0.1 g/L, the electrodeposition efficiency can reach to 95.8% after 1 h . The coating is compact and bright with the thickness from 0.3 μm to 1.6 μm. The surface emissivity of the prepared nickel-63 radio-source film is up to 2.40×10⁷ s^-1·(2πSr)^-1 while the activity is up to 1.89×10⁹ Bq, which can meet the application requirements of micro nuclear batteries. At the same time, by recovering the residual electrodeposition solution and adjusting its composition, the reuse of electrodeposition liquid is realized, reducing the waste of nickel-63 raw material.



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A Nuclear Material Accounting Simulation Model for Spent Fuel Reprocessing Facility

BU Lixin, HE Lixia, LIU Hongbin

2022, 35(5):  390-398.  DOI: 10.7538/tws.2022.youxian.026

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In order to optimize the nuclear material accounting of spent fuel reprocessing facilities and find the main factors of the material unaccounted for (MUF), a numerical simulation model based on nuclear material accounting perspective is built, which includes the front-end process, PUREX process, uranium and plutonium back-end and MUF calculations. The material flow rate in the model can be changed easily by changing different process parameters to simulate different production scale. The simulated material measurement error comprising of random and system errors are simulated by normal distributed random variables and constant numbers respectively, which have the similar randomness and statistical features with the actual measurement uncertainty. When the model measurements are set to different random and system errors, the corresponding square error distribution and improvement direction can be obtained, by which a better measurements precision combination satisfying the uncertainty requirement can be found. The final results show that the system error of the 1AF measurement is the main source of the MUF.



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MCNP Simulating the Apatial Dose Field of Cobalt-60 Irradiation Facility

ZENG Diming, GU Jun, SONG Yanchao

2022, 35(5):  399-408.  DOI: 10.7538/tws.2021.youxian.103

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The Monte Carlo particle transport code program MCNP is used to establish a cobalt-60 irradiation device model and simulate the peripheral spatial dose field distribution outside the irradiation station in the irradiation room. The Cartesian coordinate system is established with the center point of the single-rack source frame as the coordinate origin. Considering the γ-rays non-self-absorption and the γ-rays self-absorption of cobalt-60 source, the dose rate distribution of the air surface at intervals of 10 cm along the coordinate axis and the variation law of dose rate on the coordinate axis are studied. The results show that the dose rate of the peripheral spatial dose field is relatively small, when the irradiation products of the irradiation room occupy all the irradiation stations. The variation law of dose rate on the coordinate axis of the single-rack source frame is more consistent with binomial fitting function. In the case of γ-rays self-absorption of cobalt-60 source, the dose rate near the coordinate axis of the single-rack source frame is obviously low, and the high-dose-rate region of the air surface moves to both sides as air surface moves away from the single-rack source frame. In the case of γ-rays non-self-absorption of cobalt-60 source, the high-dose-rate region of the air surface at the end face of the single-rack source frame is always located near the coordinate axis. The theoretical simulation calculation and analysis of MCNP has important practical guiding significance for the peripheral spatial dose field outside the irradiation station in the irradiation room of the cobalt-60 irradiation facility.



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Design and Application of Device for Collecting Radioactive Waste Gas from ¹³¹I Solution Vials

CHENG Haixu, SUN Ruifeng, GUO Hongli, MAO Baofeng, ZHANG Xuefeng, FU Bo

2022, 35(5):  409-414.  DOI: 10.7538/tws.2021.youxian.105

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During the process of ¹³¹I-labeled radiopharmaceuticals production, the radioactive waste gas accumulated in the vials will be released immediately when the vial of ¹³¹I solution is opened, and it will cause pollution. A set of device for collecting radioactive waste gas from ¹³¹I solution vials was developed, based on radiation resistance, operation convenience and versatility of device and the size of hot cell. The purpose of semi-automatic collection and temporary storage of radioactive waste gas was realized and the collected radioactive waste gas was measured and analyzed. The results showed that the equipment ran stably and reliably. The study of 22 batches shows that, the amount of ¹³¹I waste gas collected had a certain correlation with the ambient temperature. Three collecting bottles can fully collect the waste gas generated. In summary, the device for collecting radioactive waste gas can effectively collect the radioactive waste gas released from ¹³¹I solution, reducing the impact on the environment and operators, and has great reference significance for other radioactive drug companies. 



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Liquid-liquid Extraction of U(Ⅵ) and Pu(Ⅳ) with 2,2′-((4-Ethoxy-1,2-phenylene) bis (oxy)) bis (N,N-bis(2-ethylhexyl)acetamide)

DING Qixiu, GE Xiao, ZHU Haowei, CHEN Qi, LYU Hongbin, ZHENG Weifang, YAN Taihong

2022, 35(5):  415-423.  DOI: 10.7538/tws.2021.youxian.107

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To develop a highly selective extractant for Pu(Ⅳ), 2,2′-((4-ethoxy-1,2-phenylene)bis(oxy)) bis (N,N-bis(2-ethylhexyl)acetamide), short for 4-EthoxyBenzoDODA, has been evaluated as a novel extractant in n-dodecane diluent for the extraction of U(Ⅵ) and Pu(Ⅳ). The effect of contact time of two phases, HNO₃ concentration and extractant concentration on the distribution ratios of U(Ⅵ) and Pu(Ⅳ) was investigated. Acid uptake studies suggested that 4-EthoxyBenzoDODA (KH=0.14) was less basic as compared to BenzoDODA (KH=0.44), making it more conducive to selectively extract Pu(Ⅳ) with stronger ionic potential. Extraction experiments showed that the maximum of SFPu/U, SFPu/Eu were 6.9, 223 respectively. Slope analysis indicated extraction of 1∶1 (ML) species with U(Ⅵ) and mixed 1∶1 (ML) and 1∶2 (ML2) species with Pu(Ⅳ) at 4.0 mol/L HNO₃ 98% of Pu in the loaded organic phase can be stripped to the aqueous phase using reductive stripping agent such as hydrazine nitrate and hydroxylamine nitrate. The results showed that the 4-EthoxyBenzoDODA exhibited good selectivity toward Pu.



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The Current Situation and Prospect of Accelerator Produced Medical Radioisotopes

LIU Ning, GAO Jing, YANG Yuanyou, LI Feize, LIAO Jiali

2022, 35(5):  424-438.  DOI: 10.7538/tws.2022.youxian.015

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As one of the important ways to prepare radioisotopes, the role and status of accelerator produced nuclides have become increasingly prominent after entering the new century. In the present paper, a brief overview on development status of radioisotope preparation technology by accelerators at home and abroad was performed. In particular, the research progress of ¹⁸F, ⁶⁴Cu,   ⁶⁸Ge/⁶⁸Ga, ⁸⁹Zr, ¹¹¹In, ²¹¹At, ²²⁵Ac and other important medical radioisotope preparation technologies are introduced. The application prospects of isotopes prepared by domestic accelerators are also prospected.