期刊：
Journal of Nuclear Engineering and Radiation Science,2018年4(2):024501 ISSN：2332-8983
通讯作者：
Jian, C.
作者机构：
[Huan, Mao] Nuclear and Radiation Safety Center, MEP of China, No.54 of Hong Lian Nan Cun, Beijing 10082, Haidian, China e-mail: maohuan@chinansc.cn;[Sengai, Yang] Nuclear and Radiation Safety Center, MEP of China, No.54 of Hong Lian Nan Cun, Beijing 10082, Haidian, China e-mail: yangsengai@chinansc.cn;[Wenbin, Xiong] Nuclear and Radiation Safety Center, MEP of China, No.54 of Hong Lian Nan Cun, Beijing 10082, Haidian, China e-mail: xiongwenbin@chinansc.cn;[Huwei, Li] Nuclear and Radiation Safety Center, MEP of China, No.54 of Hong Lian Nan Cun, Beijing 10082, Haidian, China e-mail: lihuwei@chinansc.cn;[Jian, Cao] Nuclear and Radiation Safety Center, MEP of China, No.54 of Hong Lian Nan Cun, Beijing 10082, Haidian, China e-mail: caojian@chinansc.cn
通讯机构：
Nuclear and Radiation Safety Center, MEP of China, No.54 of Hong Lian Nan Cun, Beijing, Haidian, China
作者机构：
[刘红娟; 谢水波] Institute of Nuclear Science and Technology, University of South China, Hengyang;Hunan;421001, China;Key Discipline Laboratory for National Defence for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang;[张希晨; 刘迎九; Zeng, Tao-Tao] Hunan Province Key Laboratory of Pollution Control and Resources Reuse Technology, University of South China, Hengyang
通讯机构：
[Xie, S.-B.] I;Institute of Nuclear Science and Technology, University of South China, Hengyang, Hunan, China
摘要：
Cardiac activity can induce dose–volume evaluation errors for cardiac structures. The purpose of this study was to quantify the variation in dose–volume parameters for the heart, pericardium and left ventricular myocardium (LVM) throughout the cardiac circle. The heart, pericardium and LVM of 22 patients were contoured on 20 phases of electrocardiography-gated 4D computed tomography (4DCT) images acquired during breath-hold. Radiotherapy plans were designed on 0% phase of the 4DCT images, and the dose distributions of the plans were imported into MIM Maestro and deformed to each phase to generate distributions for all phases. Variations in dose–volume parameters for the heart, pericardium and LVM were compared among different phases. The rates of variation in Dmean for the heart and pericardium were 3.33 ± 1.04% and 2.66 ± 1.15%, respectively. The mean values of the maximum difference in V5, V10, V20, V30 and V40 were all <2% for the heart and pericardium and were not statistically significant (P > 0.05). The rate of variation in Dmean for the LVM reached 87.05 ± 38.34%, and the maximum differences in V5, V10, V20, V30 and V40 were 13.76 ± 4.46%, 13.64 ± 4.33%, 12.84 ± 4.55%, 11.62 ± 4.85% and 3.63 ± 2.56%, respectively; all differences were statistically significant (P < 0.05). Variations in dose–volume parameters were more significant in the LVM than in the heart and pericardium (P < 0.05). The dose–volume parameters for the LVM were significantly influenced by cardiac activity, whereas those for the heart and pericardium were not; therefore, individual dosimetric evaluation and limitation must be performed for the LVM.
通讯机构：
[Gong, G.-Z.] D;Department of Radiation Physics, Shandong Cancer Hospital Affiliated to Shandong University, Shandong Academy of Medical Sciences, Jinan, China
摘要：
Photodisintegration reaction rates involving charged particles are relevant to the p-process nucleosynthesis that aims at explaining the production of stable neutron-deficient nuclides heavier than iron. In this study, considering the compound and pre-equilibrium reaction mechanisms, the cross sections and astrophysical rates of (γ,p) and (γ,α) reactions for about 3000 target nuclei with 10≤Z≤100 ranging from stable to proton dripline nuclei are computed. To study the sensitivity of the calculations to the optical model potentials (OMPs), both the phenomenological Woods-Saxon and the microscopic folding OMPs are taken into account. The systematic comparisons show that the reaction rates, especially for the (γ,α) reaction, are dramatically influenced by the OMPs. Thus, better determination of the OMP is crucial to reduce the uncertainties of the photodisintegration reaction rates involving charged particles. Meanwhile, a γ-beam facility at Extreme Light Infrastructure–Nuclear Physics (ELI-NP) is being developed which will open new opportunities to experimentally study the photodisintegration reactions of astrophysical interest. Considering both the important reactions identified by the nucleosynthesis studies and the purpose of complementing the experimental results for the reactions involving p nuclei, the measurements of six (γ,p) and eight (γ,α) reactions based on the γ-beam facility and the Extreme Light Infrastructure Silicon Strip Array (ELISSA) for the detection of charged particles at ELI-NP are proposed. Furthermore, the geant4 simulations on these (γ,p) and (γ,α) reactions are performed using the calculated cross sections and the features of the γ-beam facility and the ELISSA detector at ELI-NP. Simultaneously satisfying the minimum detectable limit of the experimental yield and the particle identification of protons and α particles, the minimum required energies of the γ beam to measure the six (γ,p) and eight (γ,α) reactions are estimated. It is shown that the direct measurements of these photonuclear reactions based on the γ-beam facility at ELI-NP within the Gamow windows at the typical temperature of T9=2.5 for the p-process are fairly feasible and promising. We believe that this pivotal work will guide the future photodisintegration experiments at ELI-NP. Furthermore, the expected experimental results will be used to constrain the OMPs of the charged particles, which can eventually reduce the uncertainties of the reaction rates for the p-process nucleosynthesis.
关键词：
Esophageal cancer radiotherapy;Deformable image registration;Dose-volume parameters;Heart;Left ventricular myocardium
摘要：
The deformable image registration (DIR) technique has the potential to realize the dose accumulation during radiotherapy. This study will analyze the feasibility of evaluating dose-volume parameters for the heart and left ventricular myocardium (LVM) by applying DIR. The electrocardiograph-gated four-dimensional CT (ECG-gated 4DCT) data of 21 patients were analyzed retrospectively. The heart and LVM were contoured on 20 phases of 4DCT (0%, 5%,…,95%). The heart and LVM in the minimum volume/dice similarity coefficient (DSC) phase (Volume min/DSC min) were deformed to the maximum volume/DSC phase (Volume max/ DSC max), which used the intensity-based free-form DIR algorithm of MIM software. The dose was deformed according to the deformation vector. The variations in volume, mean dose (Dmean), V20, V30 and V40 for the heart and LVM before and after DIR were compared, and the reference phase was the Volume max/DSC max phase. For the heart, the difference between the pre- and post-registration Volume min and Volume max were reduced from 13.87 to 1.72%; the DSC was increased from 0.899 to 0.950 between the pre- and post-registration DSC min phase relative to the DSC max phase. The post-registration Dmean, V20, V30 and V40 of the heart were statistically significant compared to those in the Volume max/DSC max phase (p < 0.05). For the LVM, the difference between the pre- and post-registration Volume min and Volume max were only reduced from 18.77 to 17.38%; the DSC reached only 0.733 in the post-registration DSC min phase relative to the DSC max phase. The pre- and post-registration volume, Dmean, V20, V30 and V40 of the LVM were all statistically significant compared to those in the Volume max/DSC max phase (p < 0.05). There was no significant relationship between the variation in dose-volume parameters and the variation in the volume and morphology for the heart; however, the inconsistency of the variation in the volume and morphology for the LVM was a major factor that led to uncertainty in the dose-volume evaluation. In addition, the individualized local deformation registration technology should be applied in dose accumulation for the heart and LVM.
作者机构：
[邓年彪; 于涛; 谢金森; 赵文博; 谢芹; 陈珍平; 赵鹏程; 刘紫静; Zeng, Wenjie] School of Nuclear Science and Technology, University of South China, Hengyang;Hunan;421001, China;Virtual Simulation Experiment Teachering Center on Nuclear Energy and Technology, University of South China, Hengyang;[邓年彪; 于涛; 谢金森; 赵文博; 谢芹; 陈珍平; 赵鹏程; 刘紫静; Zeng, Wenjie] Hunan
通讯机构：
School of Nuclear Science and Technology, University of South China, Hengyang, Hunan, China
摘要：
Quantification of heart, pericardium, and left ventricular myocardium movements during the cardiac cycle for thoracic tumor radiotherapy Ying Tong,1,2 Yong Yin,1 Jie Lu,1 Tonghai Liu,1 Jinhu Chen,1 Pinjing Cheng,2 Guanzhong Gong1 1Department of Radiation Physics, Shandong Cancer Hospital Affiliated to Shandong University, Jinan, 2School of Nuclear Science and Technology, University of South China, Hengyang, People’s Republic of China Purpose: The purpose of this study was to quantify variations in the heart, pericardium, and left ventricular myocardium (LVM) caused by cardiac movement using the breath-hold technique. Patients and methods: In this study, the electrocardiography-gated four-dimensional computed tomography (CT) images of 22 patients were analyzed, which were sorted into 20 phases (0–95%) according to the cardiac cycle. The heart, pericardium, and LVM were contoured on each phase of the CT images. The positions, volume, dice similarity coefficient (DSC) in reference to 0% phase, and morphological parameters (max 3D diameter, roundness, spherical disproportion, sphericity, and surface area) in different phases of the heart, pericardium, and LVM were analyzed, which were presented as mean ± standard deviation. Results: The mean values of displacements along the X, Y, and Z axes respectively were as follows: 1.2 mm, 0.6 mm, and 0.6 mm for the heart; 0.5 mm, 0.4 mm, and 0.8 mm for the pericardium; and 1.0 mm, 4.1 mm, and 1.9 mm for the LVM. The maximum variations in volume and DSC respectively were 16.49%±3.85% and 10.08%±2.14% for the heart, 12.62%±3.94% and 5.20%±1.54% for the pericardium, and 24.23%±11.35% and 184.33%±128.61% for the LVM. The differences in the morphological parameters between the maximum and minimum DSC phases for the heart and pericardium were not significantly different (p>0.05) but were significantly different for the LVM (p<0.05). Conclusion: The volumetric and morphological variations of the heart were similar to those of pericardium, and all were significantly smaller than those of the LVM. This inconsistency in the volumetric and morphological variations between the LVM and the heart and pericardium indicates that special protection of the LVM should be considered. Keywords: thoracic radiotherapy, cardiac activity, cardiac structures, variations, volume, morphology
摘要：
Abstract: Boron carbide (B4C)/polytetrafluoroethylene (PTFE) neutron absorbing composite materials were prepared by liquid phase sintering method at 380˚C. The themogravimetry-differential scanning calorimetry (TG-DSC) was adopted to characterize the sintering process while X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques were used to investigate the phase constitution and microstructure of the composites. In addition, the influence of B4C content on the mechanical and neutron absorbing properties of the composites was tested. Results indicate that the relative density and impact toughness gradually increase while the hardness drops with decreasing B4C content. Lowering the B4C content however reduces neutron absorption capacity, as confirmed by the MCNPX simulations. The transmissivity of B4C/PTFE composite is 2.45 × 10−6 for 1Å neutrons through a 5 mm-thick sample with 70 wt% B4C content. This hydrogen-free composite is a suitable neutron absorber for beam line shielding purposes.#@#@#摘要: 采用低温液相烧结法制备了碳化硼(B4C)/聚四氟乙烯(PTFE)新型无氢中子吸收复合材料，在380℃下实现了致密烧结。通过同步热分析仪(TG-DSC)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)等对复合材料的烧结过程、结构组成和微观形貌进行了分析。此外，本文研究了B4C含量变化对样品力学性能和中子吸收能力的影响。研究结果表明：随着复合材料中B4C含量的降低，其相对密度和冲击韧性逐渐增大；硬度逐渐减小。复合材料中子吸收能力的中子输运蒙卡模拟计算(MCNPX)结果表明，随着B4C含量的减少，其慢中子吸收能力逐渐降低。在所研究的复合材料中，当B4C含量为70 wt%，厚度为5 mm时，其对1Å波长中子的透射率为2.45 × 10−6，可满足中子散射谱仪束线吸收材料的通常应用要求。
