Novel ultra-fast photodetectors for near reconstruction-less time-of-flight positron emission tomography

用于近重建飞行时间正电子发射断层扫描的新型超快光电探测器

基本信息

批准号：
9809409
负责人：
Gerard Ariño Estrada
金额：
$ 22.28万
依托单位：
UNIVERSITY OF CALIFORNIA AT DAVIS
依托单位国家：
美国
项目类别：
财政年份：
2019
资助国家：
美国
起止时间：
2019-07-01 至 2022-03-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9809409
关键词：
3-Dimensional Bismuth Bromides Calibration Cells Cherry - dietary Clinical Coupled Crystallization Data Detection Development Devices Dimensions Electrons Evaluation Gamma Rays Germany Goals Image Japan Lead Legal patent Lesion Light Measures Mentorship Morphologic artifacts Muslim religion Noise Penetration Performance Periodicity Photons Physiologic pulse Positioning Attribute Positron Positron-Emission Tomography Property Radiation Dose Unit Reaction Time Resolution Signal Transduction Silicon Structure System Technology Testing Thallium Thick Thinness Time Width Work absorption attenuation base design detector experience high reward high risk improved innovation novel off-patent optical communication photomultiplier photon-counting detector photonics prevent prototype quantum radiation detector reconstruction response tumor ultraviolet

项目摘要

SUMMARY Time-of-Flight Positron Emission Tomography (TOF-PET) scanners provide better signal-to-noise ratio (SNR) and artifact reduction compared to conventional PET systems. The performance of TOF-PET scanners improves with the timing precision of its detectors: the more accuracy in the time detection of gamma photons the better the performance. The ultimate aim of TOF-PET is to reach a 10 ps full width at half maximum (FWHM) coincidence time resolution (CTR) to resolve precisely the positron-electron annihilation point in 3 dimensions. State-of-the-art PET detectors consist of scintillation crystals coupled to silicon photomultipliers (SiPM) and show timing resolutions in the order of 100-200 ps FWHM. In this project, we focus on improving dramatically the timing properties of the SiPMs, as such improvement would have a strong impact on TOF-PET as it would improve the timing performance of most detectors that use scintillation crystals and/or Cerenkov light emitters by several-fold. State-of-the-art SiPMs are optimized for a narrow range of wavelengths (λ) because of the difference in penetration depth at different wavelengths. For photons of λ=450 nm and λ=590 nm, the attenuation depth is 0.4 μm and 2 μm, respectively. The trade-off is to either a) to have a thicker depletion layer to absorb a wider range of wavelengths but to increase the time jitter, or b) to have a thinner depletion layer to reduce the time jitter but absorb only a narrow range of wavelengths. Therefore, there is not a state-of-the-art SiPM that provides, simultaneously, very fast time response, and high photon detection efficiency (PDE) across a wide range of wavelengths. We propose to develop an SiPM prototype with photon-trapping microstructures integrated in the depletion layer that disperses the light laterally and allows one to obtain high-detection efficiency for a wide range of wavelengths within a depletion layer of 1 μm. With such a thin layer, the jitter in the electron drift time decreases to 10 ps and the dark current is expected to decrease as well. This new photosensor could revolutionize TOF-PET. The utilization of periodic microstructures to bend light in a perpendicular orientation and trapping photons for enhanced interaction with materials, high detection efficiency and fast response have been recently shown for wavelengths between 800-900 nm for optical communication. In this proposal, we will develop a new SiPM based on this technology. First, we will simulate the optimum layer structure to integrate the hole-trapping microstructures and an avalanche region to provide a gain of >105. Second, we will do an electronic characterization for the different type of microcells, including a gain calibration and measure quantum efficiency for different λ for each cell. Finally, we will manufacture a wafer with full-size SiPMs (3x3 mm2) and test the SiPMs with scintillation crystals and Cerenkov emitters.

概括飞行时间正电子发射断层扫描 (TOF-PET) 扫描仪提供更好的信噪比 (SNR) 与传统 PET 系统相比，TOF-PET 扫描仪的性能得到改善。与其探测器的计时精度有关：伽马光子的时间探测越精确越好 TOF-PET 的最终目标是达到 10 ps 半高宽 (FWHM)。重合时间分辨率 (CTR) 可精确解析 3 维中的正电子-电子湮灭点。最先进的 PET 探测器由与硅光电倍增管 (SiPM) 耦合的闪烁晶体组成，并显示时序分辨率约为 100-200 ps FWHM。在这个项目中，我们专注于显着提高 SiPM 的定时特性，因为这种改进将对 TOF-PET 产生重大影响，因为它将提高大多数使用闪烁晶体和/或切伦科夫光发射器经过数倍优化。由于不同波长的穿透深度不同，波长（λ）范围较窄。 λ=450 nm 和 λ=590 nm 的光子，衰减深度分别为 0.4 μm 和 2 μm。 a) 具有更厚的耗尽层以吸收更广泛的波长，但会增加时间抖动，或者 b) 具有更薄的耗尽层以减少时间抖动，但仅吸收窄范围的波长。因此，目前还没有一种最先进的 SiPM 能够同时提供非常快的时间响应和高宽范围波长的光子检测效率 (PDE)。我们建议开发一种 SiPM 原型，其光子捕获微结构集成在耗尽层中横向色散光，使人们能够在较宽的波长范围内获得高检测效率在 1 μm 的耗尽层内，电子漂移时间的抖动降低至 10 ps，这种新的光电传感器预计也会减少暗电流，从而彻底改变 TOF-PET。利用周期性微结构使光沿垂直方向弯曲并捕获光子最近显示出与材料的增强相互作用、高检测效率和快速响应用于光通信的波长在 800-900 nm 之间。在本提案中，我们将开发一种基于 SiPM 的新型器件。首先，我们将模拟最佳层结构以集成空穴捕获。微结构和雪崩区域以提供 >105 的增益其次，我们将制作一个电子器件。不同类型微电池的表征，包括增益校准和测量量子效率最后，我们将制造具有全尺寸 SiPM (3x3 mm2) 的晶圆并测试。具有闪烁晶体和切伦科夫发射器的 SiPM。