自由结构PET在束监测碳离子治疗剂量成像过程研究

In-beam PET 成像为碳离子、质子等粒子放射治疗提供了一种非侵入式的实时剂量监测方法。本文设计自由结构的in-beam PET模型,包括环形、C型、双平板型和直角型PET,并在蒙特卡罗模拟平台GATE上仿真碳离子打靶的in-beam PET成像过程。该PET包含32个探测模块,通过自由组合的方式形成探测视野相近、适用于人体或小动物体不同部位的碳离子治疗剂量成像。每个探测模块由20×20的硅酸钇镥晶体阵列耦合硅光电倍增管构成。单个晶体大小为1.5 mm×1.5 mm×10 mm,像素为1.6 mm。在蒙特卡罗模拟平台GATE中仿真230 MeV/u的碳离子笔形束轰击聚甲基丙烯酸甲酯（PMMA）靶体和在束PET成像过程,得到正电子核素分布后通过MLEM算法得到PET断层图像。结果显示,图像峰位的变化反映了正电子活度峰位的移动,表明自由结构PET可用于在束监测碳离子治疗剂量分布。使用八探头平板型在束PET成像实验和仿真进行对比,其图像一维谱峰值均为27 mm,验证了自由结构PET模型用于在束监测碳离子治疗剂量成像可行。     

质子治疗电离室剂量读出电子学研制

中国原子能科学研究院正在研制一套用于质子治疗的治疗头设备,为了实现束流剂量的测量,研制了一套剂量读出电子学装置,用于实现电离室剂量信号读取和测试。该电子学通过IVC102精密低噪声积分器实现电荷的积分放大,DSP56F82控制ADC实现数据的采集并处理,装置采用Modbus通信协议实现和上位机间的通信。同时设计了固定电荷发生器,利用其产生固定电荷量,用于对该电荷测量装置进行试验测试。结果表明,该装置在20 pC~2 μC电荷测量范围内的最大相对误差在0?62%以内,满足了设计需求。     

Implementation and application of PyNE sub-voxel R2S for shutdown dose rate analysis

PyNE R2S is a mesh-based R2S implementation with the capability of performing shutdown dose rate (SDR) analysis directly on CAD geometry with Cartesian or tetrahedral meshes. It supports advanced variance reduction for fusion energy systems. However, the assumption of homogenized materials of PyNE R2S with a Cartesian mesh throughout a mesh voxel introduces an approximation in the case where a voxel covers multiple non-void cells. This work implements a sub-voxel method to add fidelity to PyNE R2S with a Cartesian mesh during the process of activation and photon source sampling by performing independent inventory calculations for each cell within a mesh voxel and using the results of those independent calculations to sample the photon source more precisely. PyNE sub-voxel R2S has been verified with the Frascati Neutron Generator (FNG)-ITER and ITER computational shutdown dose rate benchmark problems. The results for sub-voxel R2S show satisfactory agreement with the experimental values or reference results. PyNE sub-voxel R2S has been applied to the shutdown dose rate calculation of the Chinese Fusion Engineering Testing Reactor (CFETR). In conclusion, sub-voxel R2S is a reliable tool for SDR calculation and obtains more accurate results with the same voxel size than voxel R2S.     

Comparison of the TSI Model 3306 Impactor Inlet with the Andersen Cascade Impactor: Solution Metered Dose Inhalers

The product performance of a series of solution Metered Dose Inhalers (MDIs) were evaluated using the TSI Model 3306 Impactor Inlet and the Andersen Cascade Impactor (ACI). The goal of the study was to test whether the fine particle and coarse particle depositions obtained using the Model 3306 were comparable to those results obtained by ACI testing. The analysis using the Model 3306 was performed as supplied by the manufacturer as well as with 20 cm and 40 cm vertical extensions that were inserted between the Model 3306 and the USP Inlet. Nine different solution formulations were evaluated. The drug concentrations ranged from 0.08 to 0.8% w/w and the ethanol cosolvent concentration varied between 5 and 20% w/w. In general, it was found that good correlations between the two instruments were obtained. However, for formulations containing 10–20% w/w ethanol it is shown that an extension fitted to the Model 3306 yielded an improved correlation to those obtained from the ACI.     

Comparison of optical particle sizing and cascade impaction for measuring the particle size of a suspension metered dose inhaler

Optical techniques for the particle size characterization of metered dose inhaler (MDI) suspensions have been developed as an alternative to the labor-intensive and time-consuming impaction method. In this study, a laser diffraction (LD) apparatus with a liquid cell (“wet cell” method) and a “time-of-flight” apparatus named aerodynamic particle sizer (APS) were utilized to assess MDI suspensions with varied formulation compositions and storage conditions. The results were compared with the conventional Anderson cascade impaction (ACI) data. The two optical methods were able to detect the changes in particle size distributions between formulations, yet to a lesser extent than those observed using the cascade impaction methodology. The median aerodynamic particle size measured by the APS method and the median geometric particle size obtained from the LD method were linearly correlated with the corresponding ACI results in the range of 2–5?µm. It was also found that the APS measurement was biased towards the finer particle size region and resulted in overestimated fine particle fraction (FPF) values which were 2–3 times folds of the ACI results. In conclusion, the optical particle sizing techniques may, under some circumstances, be viable techniques for the rapid assessment of MDI suspensions. The “wet cell” LD method, in particular, is found to be a valuable means of detecting active pharmaceutical ingredient (API) particle size changes in an MDI suspension. Using both the LD and the APS methods in early formulation screening followed by a final assessment with cascade impaction analysis can improve the efficiency of MDI formulation development.     

The development of dimple-shaped chitosan carrier for ethambutol dihydrochloride dry powder inhaler

Objective: In this study, a dimple-shaped chitosan carrier was developed for delivering the antituberculosis drug ethambutol dihydrochloride (EDH) from a dry powder inhaler (DPI) to the lungs.

Materials and methods: Nanosized drug particles were prepared using nanospray drying. The microsized carrier was developed from a chitosan solution by spray drying. Five formulations were prepared by physically mixing the drug and carrier in different ratios. The physico-chemical properties of the formulations were analyzed using scanning electron microscopy, differential scanning calorimetry, Fourier transform infrared spectroscopy, ultracentrifugation and a cascade impactor.

Result and discussion: The EDH size was 222?nm and the chitosan carrier size was 1.2?µm. Five formulations, i.e. 1:2, 1:2.5, 1:3.3, 1:5 and 1:10 w/w of the EDH to chitosan carrier were prepared by physical mixing. The chitosan carrier was spherical in shape with a dimpled surface and this provided shallow cavities to which the drug was bound, both within its grooves as well as on its surface. The median adhesion force (50% of drug detachment) for formulations #1 to #5 was between 122 and 993?µN. The mass median aerodynamic diameter of the EDH was between 2.3 and 2.7?μm, with the fine particle fractions (aerosolized particles less than 4.4?μm) of 32–42% of the nominal dose.

Conclusion: We suggest that ethambutol dihydrochloride mixed with a chitosan carrier was suitable for use in a dry powder inhaler for controlling tuberculosis especially in minimizing the risk of multidrug resistant tuberculosis and the possible side effects from EDH.     

Synthesis,characterization and TL properties of SrSO_4:Dy,Tb nanocrystalline phosphor

SrSO4:Dy,Tb nanocrystalline with crystalline size in the range of 44–54 nm was prepared by co-precipitation method followed by thermal treatment and characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDX) and UV-visible spectrometry. Our results provided direct evidence of incorporation of impurities into nanocrystalline SrSO4. The thermoluminescence(TL) properties of SrSO4:Dy,Tb nanocrystalline pellets irradiated with gamma rays at different doses were studied. The TL glow curve of SrSO4:Dy,Tb nanocrystalline pellets had a prominent peak at around 490 K and a small peak at around 430 K. The major peak in the TL glow curve was almost resolved from other peaks, which was analyzed using Chen's peak shape method to determine the TL kinetic parameters such as activation energy, E and kinetic order, b. The intensity of main dosimetric peak of SrSO4:Dy,Tb nanocrystalline pellets at around 490 K increased linearly with the increase in gamma dose. The TL response was linear in the range of 0.1–7 kGy. These properties made it a candidate as a dosimeter to be used for estimating the high dose of gamma rays.     

Influence of temperature and dose rate on the degradation of BiCMOS operational amplifiers during total ionizing dose testing

The degradation of BiCMOS operational amplifiers TLV2451CP under the gamma-irradiation is studied for different dose rates and temperatures during irradiation. It is shown that studied devices are sensitive to both enhanced low dose rate sensitivity and time-dependent effects. Evidently the main reason for degradation of studied devices is build-up of the interface traps. Obtained results show possibility to develop an approach for total ionizing dose testing of BiCMOS devices considering low dose rate effects.     

铀矿冶系统工作人员个人剂量变化规律的分析

本文通过对我国铀矿冶工作人员３０年回顾性个人剂量的统计与分析，得出了我国铀矿冶工作人员个人受照剂量的变化规律，进而提出了改进铀矿冶作业环境、提高辐射防护水平、降低工作人员受照剂量的建议。     

Reproductive toxicity of phthalate esters

Phthalate esters are ubiquitous environmental contaminants that in general display low‐toxicity. Overall, the reproductive effects of these compounds are well characterized in adult's animals, with gonadal injury observed after high dose exposure. However, results of recent transgeneration studies indicate that the reproductive system of developing animals is particularly vulnerable to certain phthalates. The phenotypic alterations observed in male offspring rats exposed during the perinatal period have remarkable similarities with common human reproductive disorders, including cryptorchidism, hypospadias and low‐sperm counts. Recent results also indicate that high phthalate doses can adversely affect adult and developing female rats. However, the main question involving phthalates is whether the current level of human exposure is sufficient to adversely affect male and/or female reproductive health. Here, we review the reproductive toxicity data of phthalates in adult and developing animals as well as possible modes of action. In addition, we briefly discuss the relevance of animal studies to humans in light of recent epidemiological data and experimental research with low (human relevant) doses. Finally, we point out some critical issues that should be addressed in order to clarify the implications of phthalates for human reproduction.