Pb-Qdot Direct Gamma Detectors

描述（由申请人提供）：分子成像系统（例如 PET、伽马相机）需要电子致密材料来有效检测高能伽马射线。增加探测器中电子密度的传统解决方案是用高原子序数材料（例如溴化镧）制造闪烁体。由于难以提供高透明度和均匀性的晶锭，高质量电子致密闪烁体往往很昂贵。闪烁体还具有需要光电探测器（例如光电倍增管）将可见光转换为电信号的缺点，这进一步增加了体积和费用。由于从伽马射线到电信号的转换过程中的步骤数量减少，直接检测固态设备比闪烁体具有更好的能量分辨率。有几种固态材料具有出色的能量分辨率（例如 CZT - 碲化镉锌），但对 PET 系统中使用的伽马射线的阻止能力较低，并且相对昂贵。尽管其他半导体电子致密化合物具有高阻止本领（即 PbS、PbSe），但由于这些化合物的不利电子特性（例如低载流子迁移率寿命乘积和/或窄带隙），使用它们设计直接检测器件一直具有挑战性。低载流子迁移率-寿命乘积会导致任何实际厚度的探测器的能量分辨率较差。窄带隙导致低电阻率，从而导致高漏电流。纳米技术可以提供具有与相同化合物的本体配方显着不同的电子特性的受限材料（例如量子点）。这种微调电子特性的能力引起了光伏界的强烈兴趣。该提案建立在一个小组所做的大量工作的基础上，该小组将量子结构嵌入半导体塑料中，形成具有良好迁移率寿命和带隙特性的导电聚合物供体-受体体异质结。从我们的角度来看，量子点很偶然，可以由具有高原子序数的廉价化合物（例如硫化铅）构成。我们建议探索使用廉价的电子致密量子点/聚合物复合材料作为 X 射线和伽马射线探测器。公共卫生相关性：分子成像系统（PET 和核医学）已融入癌症诊断和治疗。这些分子成像系统采用昂贵的探测器材料以有效地收集辐射。我们建议使用纳米技术方法来制造新型辐射探测器材料，这将降低分子成像系统的成本和尺寸，并降低患者的辐射暴露。

DESCRIPTION (provided by applicant): Molecular imaging systems (e.g., PET, gamma cameras) require electron-dense materials to effectively detect high-energy gamma rays. The traditional solution to increasing electron density in detectors has been to fabricate scintillators out of high-atomic-number materials (e.g., lanthanum bromide). High quality electron-dense scintillators tend to be expensive, due to difficulties in delivering crystal boules of high transparency and uniformity. Scintillators also have the disadvantage of requiring photodetectors (e.g., photomultipliers) to convert visible light into electrical signals, further adding to bulk and expense. Direct-detecting solid-state devices have better energy resolution than scintillators because of the reduced number of steps in the conversion process from gamma-rays to electrical signal. Several solid-state materials are available with excellent energy resolutions (e.g., CZT - cadmium zinc telluride), but have low stopping power for gamma-rays used in PET systems, and are relatively expensive. Although other semiconducting electron-dense compounds are available with high stopping power (i.e. PbS, PbSe), it has been challenging to design direct-detecting devices using them, because of unfavorable electronic properties of these compounds (e.g., low carrier mobility- lifetime product and/or narrow band-gap). Low carrier mobility-lifetime product results in poor energy resolution for detector of any practical thickness. Narrow band-gaps result in low resistivity, and consequently in high leakage current. Nanotechnology can provide confined materials (e.g., quantum dots) with electronic properties that significantly differ from those of the bulk formulations of the same compounds. This ability to fine-tune electronic properties has generated strong interest within the photovoltaic community. This proposal builds on the substantial work generated by one group that has embedded quantum structures in semiconducting plastics, forming conducting polymer donor- acceptor bulk heterojunctions with favorable mobility-lifetime and band-gap characteristics. Fortuitously from our point of view, quantum dots can be constructed of inexpensive compounds with high atomic number (e.g., lead sulfide). We propose to explore the use of inexpensive electron-dense quantum dot/polymer composites as x-ray and gamma-ray detectors. PUBLIC HEALTH RELEVANCE: Molecular imaging systems (PET and nuclear medicine) have become integrated into cancer diagnosis and treatment. These molecular imaging systems employ expensive detector materials in order to efficiently collect radiation. We propose the use of nanotechnology methods to fabricate novel radiation detector materials that will reduce cost and size of molecular imaging systems, and lower patients' radiation exposures.