双层深度编码探测器的晶体表面优化

设计了双层LSO晶体和位置灵敏型光电倍增管耦合构成的用于小动物PET成像的 深度编码探测器. 众所周知, 晶体的不同的表面处理影响着光输出量, 进而影响着它们构建的PET探测器的性能. 为了优化设计的深度编码探测器的性能, 测试了两种不同表面处理的LSO闪烁晶体阵列探测器的晶体分辨能力及其能量、时间和空间分辨率, 结果表明, 光滑表面LSO晶体构建的深度编码探测器显示出良好的空间、能量及时间分辨特性.     

正电子放射层析成象系统设计的计算机模拟

在一个简单实用的数学模型基础上,利用现代计算机技术对正电子放射层析成象系统(PET)进行了模拟,并详细讨论了闪烁晶体材料的物理、几何特性以及探测器环直径的大小对于PET系统的空间分辨率的影响.本文所得的结论对于开发和设计PET系统来说,是非常有用的.     

植物研究用γ射线成像系统设计

为了利用正电子发射断层成像技术在植物生理功能研究中的优势,正在开发由两个探测器相向放置构成的γ射线成像系统.系统中采用的探测器是由10×10的氧正硅酸镥(LSO)晶体阵列与滨松R5900-C12耦合组成.单个LSO尺寸为1.8mm×1.8mm×10mm.根据PET应用的特点,测试了该探测器的性能.所有闪烁晶体的图像在位置图谱中清楚可见;511keV全能峰处的能量分辨率位于14.5%—22%之间;符合时间分辨率随着位置灵敏光电倍增管的供给电压的增加而得到改善.这些实验结果表明,该LSO探测器适于构造高分辨率的双探测器成像系统.     

高能伽玛相机探测量子效率的蒙特卡罗模拟

探测量子效率（DQE）可被用来精确描述图像噪声通过成像系统的传播特性。根据级联理论,简洁得出了零频噪声传播情况下成像系统的DQE 表达式。采用蒙特卡罗程序MCNP 计算了高能X射线的硬化能谱在六种常用闪烁晶体中的能量沉积分布以及高能伽玛相机的DQE,分析了闪烁晶体的材料和厚度对DQE的影响。模拟结果表明,高密度、高原子序数是影响DQE的主要因素,在同样厚度下,LuAP和LSO转换屏的探测量子效率最高。     

植物研究用γ射线成像系统设计（英文）

为了利用正电子发射断层成像技术在植物生理功能研究中的优势,正在开发由两个探测器相向放置构成的γ射线成像系统.系统中采用的探测器是由10×10的氧正硅酸镥(LSO)晶体阵列与滨松R5900-C12耦合组成.单个LSO尺寸为1.8mm×1.8mm×10mm.根据PET应的特点,测试了该探测器的性能.所有闪烁晶体的图像在位置图谱中清楚可见;511keV全能峰处的能量分辨率位于14.5%-22%之间;符合时间分辨率随着位置灵敏光电倍增管的供给电压的增加而得到改善.这些实验结果表明,该LSO探测器适于构造高分辨率的双探测器成像系统.     

国产BaF_2闪烁晶体特性的测试

观察到了人工晶体所生长的BaF_2闪烁晶体发光的快、慢成分,并对其光产额、时间分辨率、能量分辨率、能量线性、技术衰减长度等特性进行了测试。对Co~(60)γ源,时间分辨率(标准偏差σ)为59ps(微微秒);对Cs~(137)γ源,能量分辨率为12.1％。这些指标都接近国际BaF_2闪烁晶体先进水平,展现出在核物理、核医学、粒子物理实验中应用的广泛前景。     

国产BaF2闪烁晶体特性的测试

观察到了人工晶体所生长的BaF₂闪烁晶体发光的快、慢成分, 并对其光产额、时间分辨率、能量分辨率、能量线性、技术衰减长度等特性进行了测试. 对Co⁶⁰ γ源, 时间分辨率(标准偏差σ)为59ps(微微秒); 对Cs¹³⁷ γ源, 能量分辨率为12.1%. 这些指标都接近国际BaF₂闪烁晶体先进水平, 展现出在核物理、核医学、粒子物理实验中应用的广泛前景.     

PET用新型深度编码探测器设计

平行性问题或作用深度问题影响着正电子放射层析系统(PET)的成象分辨率。本文提出和评价了一种二阶深度编码探测器,这个探测器是由两层LSO晶体和位置灵敏型光电倍增管(PS-PMT)组成,上层的晶体相对于下层的晶体的位置在X和Y方向上都有半个晶体阵列单元的错位,因为每个晶体的输出光的重心位置分布在PS-PMT上不同的位置,所以通过计算其重心位置就可在象平面上区别开每个晶体。根据PET系统的应用要求,我们验证了探测器的性能。伽马射线垂直入射时,上层晶体阵列的固有空间分辨率为1.15mmFWHM,下层晶体列阵为1.34mm FWHM.钠伽马辐射源的511keV能量峰处的平均能量分辨率对于下层晶体为19.7%,上层为23.6%.通过类似的技术亦可实现3阶、4阶深度编码探测器。     

新型位置灵敏光电倍增管的性能测量

位置灵敏型光电倍增管(PS-PMT)代表了基于单个管子的原理开发新概念γ相机的技术进步.最近,日本滨松公司出品了一种新型紧凑型的PSPMT—R7600-C12.根据正电子放射断层成像系统(PET)的应用特点,我们测试了由该PS-PMT组合成的闪烁晶体阵列探测器的空间分辨率、空间线性度、增益均匀性及时间分辨率LSO与该PS-PMT的组合空间分辨率达到1.4mm,而且显示出良好的空间线性、增益均匀性及优异的时间分辨特性.     

新型太阳中微子闪烁探测器的研制

概述了一种新型太阳中微子闪烁探测器的研制,其中载钆(Gd)液体闪烁体的Gd浓度达到5%、光的衰减长度≥150cm、对60keV的Gamma-ray之能量分辨率为21%(σ);直径1cm、厚3cm的GSO:Ce晶体,其发光产额约为NaI(Tl)晶体的20%、光的衰减时间为60ns、对662keVGamma-ray之能量分辨率为9.2%(σ).文章讨论了由这两种闪烁体构成的复合探测器的特点及作为太阳中微子探测器其本底的降低措施.对直径10cm、厚50cm的这种复合探测器的模拟计算表明其光的收集效率可达20%.     

Giant light extraction enhancement of medical imaging scintillation materials using biologically inspired integrated nanostructures

We have utilized biologically inspired (bio-inspired), moth-eye nanostructures and further improved this biomimetic structure to enhance the scintillator materials external quantum efficiency significantly. As a proof of concept, we have demonstrated very high light output efficiency enhancement for Lu(2)SiO(5):Ce(3+) (LSO:Ce) film in large area, the X-ray mammographic instrument was employed to demonstrate the light output enhancement of the Lu(2)SiO(5):Ce thin film with biologically inspired (bio-inspired) moth-eye-like nanophotonic structures. Our work could be extended to other thin film scintillator materials and is promising to achieve lower patient dose, higher resolution images of human organs and even smaller scale medical imaging.     

A novel epitaxially grown LSO‐based thin‐film scintillator for micro‐imaging using hard synchrotron radiation

The efficiency of high‐resolution pixel detectors for hard X‐rays is nowadays one of the major criteria which drives the feasibility of imaging experiments and in general the performance of an experimental station for synchrotron‐based microtomography and radiography. Here the luminescent screen used for the indirect detection is focused on in order to increase the detective quantum efficiency: a novel scintillator based on doped Lu₂SiO₅ (LSO), epitaxially grown as thin film via the liquid phase epitaxy technique. It is shown that, by using adapted growth and doping parameters as well as a dedicated substrate, the scintillation behaviour of a LSO‐based thin crystal together with the high stopping power of the material allows for high‐performance indirect X‐ray detection. In detail, the conversion efficiency, the radioluminescence spectra, the optical absorption spectra under UV/visible‐light and the afterglow are investigated. A set‐up to study the effect of the thin‐film scintillator's temperature on its conversion efficiency is described as well. It delivers knowledge which is important when working with higher photon flux densities and the corresponding high heat load on the material. Additionally, X‐ray imaging systems based on different diffraction‐limited visible‐light optics and CCD cameras using among others LSO‐based thin film are compared. Finally, the performance of the LSO thin film is illustrated by imaging a honey bee leg, demonstrating the value of efficient high‐resolution computed tomography for life sciences.     

PbWO_4晶体的光输出与能量分辨研究

研究了多种包装材料和包装工艺对钨酸铅(PbWO4)晶体光输出和能量分辨的影响,测量结果与基于GEANT4的模拟结果符合很好,并由此确定了晶体的最佳包装方法。     

Energy resolution of CsI(Na) scintillators

The presented paper on CsI(Na) scintillators is a continuation of systematical studies of alkali halide crystals exhibiting more than one exponential decay time. The CsI(Na) crystals are known to have short (～550 ns) and long (few microseconds) components in the scintillation pulse. Previous studies showed that integration of slow components of the light pulse improved the light output, non-proportionality and energy resolution of CsI(Tl), NaI(Tl) in lower temperatures and undoped NaI crystal at liquid nitrogen temperature. In this work, an influence of the shaping time in the spectroscopy amplifier on the light output, non-proportional response to γ-rays, and energy resolution of two different size CsI(Na) scintillators is examined. Each crystal was coupled to the Photonis XP5212 PMT with a photocathode blue sensitivity of 12.2 μA/l mF. The data analysis showed improved proportionality of the crystal response, higher number of photoelectrons/MeV-γ, and consequently, a better overall energy resolution obtained for 12 μs shaping time constant. Finally, the CsI(Na) characteristics are compared to that obtained previously for NaI(Tl).     

Gadolinium pyrosilicate single crystals for gamma ray and thermal neutron monitoring

Bulk Gd₂Si₂O₇:Ce (GPS:Ce) single crystals obtained by Czochralski method demonstrate a high light output at γ-irradiation (3.8 times higher in comparison with Bi₄Ge₃O₁₂ (BGO)), energy resolution 13% (137Cs, 662 KeV), fast decay time (41.7 ns), and good thermal stability of light output (up to 425 K). This combination of characteristics makes this scintillator very attractive for medical imaging and high-temperature applications. Light output at thermal neutron monitoring is evaluated as twice higher in comparison with Gd₂SiO₅:Ce (GSO). The observed rather high afterglow level (0.2% after 20 ms) and moderate energy resolution (13%) certifies a room for improvement of these parameters by further optimization of crystal quality.     

Lu2SiO5:Ce透明薄膜改性及其发光性能

Lu2SiO5:Ce具有高密度、高光产额、快衰减等优点,是一种性能优异的新型X射线闪烁薄膜材料.本文采用溶胶-凝胶工艺和旋涂技术,以无机盐为原料、2-甲氧基乙醇为溶剂、聚乙二醇(PEG)为改性剂,在石英基片上成功制备出Lu2SiO5:Ce透明薄膜,较为详细地研究了PEG对该薄膜发光性能的影响.结果表明当采用浓度为12....     

Study of the characteristics of a scintillation array and single pixels for nuclear medicine imaging applications

By using a pixelized Nal(T1) crystal array coupled to a R2486 PSPMT, the characteristics of the array and of a single pixel, such as the light output, energy resolution, peak-to-valley ratio (P/V) and imaging performance of the detector were studied. The pixel size of the NaI(TI) scintillation pixel array is 2 min×2 mm×5 mm. There are in total 484 pixels in a 22～22 matrix. In the pixel spectrum an average peak-to-valley ratio (P/V) of 16 was obtained. In the image of all the pixels, good values for the Peak-to-Valley ratios could be achieved, namely a mean of 17, a maximum of 45 and the average peak FWHM (the average value of intrinsic spatial resolution) of 2.3 mm. However, the PSPMT non-uniform response and the scintillation pixels array inhomogeneities degrade the imaging performance of the detector.     

高速线扫描共焦检眼镜

高速线扫描共焦检眼镜使用线光束照明眼底视网膜,同时利用线阵CCD对视网膜平面的单次散射线光束探测成像。系统光学放大率为7倍,横向分辨率小于10μm,对于58kHz线频的1024pixel×512pixel成像模式,成像帧频高达110frame/s。该系统实现了高分辨率、高帧频模拟人眼实验图像的获取。