Improved scintillators for time-of-flight positron emission tomography

描述(由申请人提供)：用于飞行时间正电子发射断层扫描的改进闪烁体项目摘要/摘要我们建议通过寻找具有Lu2SiO5：Ce(LSO)的伽马射线阻止能力和LaBr3：Ce的光度、计时和能量分辨率的新闪烁体来显著提高正电子发射断层扫描的诊断成像能力。与LSO相比，将光度从30,000光子/MeV提高到60,000光子/MeV，将衰减时间从40 ns减少到20 ns，将使定时分辨率提高2倍，有效飞行时间(TOF)灵敏度提高2倍。这是因为重建图像中的统计噪声的方差减小了与定时分辨率相同的系数。此外，将能量分辨率从9%提高到4%将使组织散射光子的背景减少约2倍。这些技术的进步将显著提高疾病的检测，特别是在肥胖患者和胸腔门控成像方面，并将增加使用重复成像来研究治疗对疾病的影响的能力。拟议的研究将集中于Ce3+和Pr3+激活的钚化合物，因为(1)在已知的高光度闪烁体中，只有被Ce3+和Pr3+激活的才能足够快，可以考虑用于元素周期表中三价元素的TOF和3DPET；(2)可以被Ce3+和Pr3+取代以产生高发光闪烁体(Y，La，Gd和Lu)的元素有：(1)钚提供最高的原子序数；(3)已知的高亮度闪烁体中没有任何含有比钚更重的元素。因此，钚化合物对511keV的湮没光子既有很高的光度，又有很好的阻挡能力。有数百种致密的钚化合物从未被用作伽马射线闪烁探测器。我们建议使用LBNL开发的高通量设备来合成微晶形式的掺杂候选化合物，表征它们在X射线激励下的发射，生长最佳候选晶体，并测量它们的能量和时间分辨率。晶体的大小和形状，以及光电探测器和电子设备将类似于正电子发射断层扫描仪中使用的那些。大约2,000个微晶粉末样品(200种不同掺杂化合物)将被合成和表征，大约50个最好的晶体将被生长和测量。第一原则和经验理论将被用来确定候选名单的优先顺序。LBNL处于进行这项研究的独特地位，因为最近创建了(1)高通量闪烁体发现设施(由国土安全部资助)和(2)晶体生长设施(由能源部和国土安全部资助)。其中包括48个合成炉，一个X射线衍射仪，一个脉冲X射线系统，一个X射线发光光谱仪，以及三种不同类型的14个晶体生长炉。测量仪器有计算机控制的样品换算器，并自动将数据上传到在线数据库。请注意，国土安全部不再资助钚闪烁体的开发，因为它们本身具有放射性，能源部也不再为国家实验室的核医学研究提供资金。 公共卫生相关性：改进的用于飞行时间正电子发射断层扫描的闪烁体项目叙述/相关性拟议研究的目标是发现新的辐射探测器材料(闪烁体)，与目前用于正电子发射断层扫描的探测器相比，该材料具有更好的光电阻止能力、时间分辨率和能量分辨率。这将使这些机器能够产生人体内发射正电子的同位素的3D图像，质量更高，辐射剂量更低。其结果是改进了对疾病的检测，并能够对治疗对疾病的影响进行重复研究。

DESCRIPTION (provided by applicant): Improved Scintillators for Time-of-Flight Positron Emission Tomography Project Summary/Abstract We propose to significantly improve the diagnostic imaging capability of positron emission tomography by finding new scintillators with the gamma-ray stopping power of Lu2SiO5:Ce (LSO) and the luminosity, timing, and energy resolution of LaBr3:Ce. Compared with LSO, improving the luminosity from 30,000 photons/MeV to 60,000 photons/MeV and reducing the decay time from 40 ns to 20 ns will improve the timing resolution by a factor of two and the effective time-of-flight (TOF) sensitivity by a factor of two. This is because the variance of the statistical noise in the reconstructed image is reduced by the same factor as the timing resolution. Moreover, improving the energy resolution from 9% to 4% will reduce the background from tissue-scattered photons by about a factor of two. These advances in technology will significantly improve the detection of disease, especially in obese patients and for gated imaging of the thorax, and will increase the ability to use repeat imaging to study the effects of therapy on the disease. The proposed research will focus on Ce3+ and Pr3+ activated lutetium compounds because (1) of the known high-luminosity scintillators, only those activated with Ce3+ and Pr3+ are fast enough to be considered for TOF and 3D PET (2) of the trivalent elements in the periodic table that can be substituted with Ce3+ and Pr3+ to produce highly luminous scintillators (Y, La, Gd, and Lu), lutetium provides the highest atomic number and (3) no known high-luminosity scintillator contains an element heavier than lutetium. Thus, lutetium compounds have the highest promise of having both high luminosity and good stopping power for 511 keV annihilation photons. There are hundreds of dense lutetium compounds that have never been explored as gamma-ray scintillation detectors. We propose to use the high- throughput facilities developed at LBNL to synthesize doped candidate compounds in microcrystalline form, characterize their emissions under X-ray excitation, grow crystals of the best candidates, and measure the their energy and timing resolution. The crystal size and shape, and the photodetector and electronics will be similar to those used in a positron emission tomograph. Approximately 2,000 microcrystalline powder samples (of 200 different doped compounds) will be synthesized and characterized, and approximately 50 crystals of the best will be grown and measured. First-principles and empirical theory will be used to prioritize the candidate lists. LBNL is in a unique position to perform this research because of the recent creation of (1) the high-throughput scintillator discovery facility (funded by DHS) and (2) the crystal growth facility (funded by DOE and DHS). These contain 48 synthesis furnaces, an X-ray diffractometer, a pulsed X-ray system, an X-ray luminescence spectrometer, and 14 crystal growing furnaces of three different types. The measurement instruments have computer-controlled sample changers and automatically upload their data to an on-line database. Note that DHS does not fund the development of lutetium scintillators due to their inherent radioactivity and DOE no longer funds nuclear medicine research at the National Laboratories. PUBLIC HEALTH RELEVANCE: Improved Scintillators for Time-of-Flight Positron Emission Tomography Project Narrative/Relevance the goal of the proposed research is the discovery of new radiation detector materials (scintillators) with an improved combination of photoelectric stopping power, timing resolution, and energy resolution compared with the detectors currently used in positron emission tomographs. This would allow these machines to produce 3D images of positron-emitting isotopes in the human body of higher quality and with lower radiation dose. The result is improved detection of disease and the ability to perform repeated studies of the effects of therapy on the disease.