Time resolution deterioration with increasing crystal length in a TOF-PET system
Time resolution deterioration with increasing crystal length in a TOF-PET system
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DOI：
10.1016/j.nima.2013.11.025
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发表时间：
2014-02-11
影响因子：
1.4
通讯作者：
Lecoq, P.
中科院分区：
文献类型：
--
作者：
Gundacker, S.;Knapitsch, A.;Lecoq, P.
基于闪烁体的探测器的最高时间分辨率变得越来越重要。在医学探测器物理学中，L（Y）SO放大器通常用于飞行时间正电子发射断层扫描（TOP-PET）。符合时间分辨率（CTR）小于100 ps FWHM是理想的，以便提高图像信噪比，从而通过更短的扫描时间给患者带来好处。此外，在高能物理中，需要将量热计的计时能力提高到10 ps。为了实现这些目标，重要的是研究整个链，即晶体中的高能粒子相互作用，闪烁过程本身，闪烁光在晶体中的传输，光电探测器和电子学。在利用超快准直器的符合装置中，用超阈值时间法测量了类PET系统的时间分辨率。利用与市售SiPM（Hamamatsu S10931- 050 P MPPC）耦合的2 x 2 x 3 mm（3）LSO：Ce共掺杂的0.4%Ca晶体，我们在511 keV的能量下实现了108 +/-5 ps FWHM的CTR。在相同的实验条件下，晶体长度增加到5 mm使CTR恶化到123 +/- 7 ps FWHM，10 mm恶化到143 +/- 7 ps FWHM，20 mm恶化到176 +/- 7 ps FWHM。CTR的这种退化是由晶体中的光传输效率（LTE）和光传输时间扩展（LTTS）引起的。为了定量地了解测量值，我们在MATLAB中开发了一个Monte Carlo模拟工具，将光电探测器和电子器件的时序特性，晶体的闪烁特性和SLITRANI模拟的晶体内的光传输结合起来。在这项工作中，我们表明，模拟的预测与实验数据吻合得很好。我们的结论是，对于较长的晶体，CTR的恶化主要是由LTE引起的，即到达光电探测器的光子与闪烁产生的光子总量的比率，而MS的影响部分地被晶体中的伽马吸收抵消，（C）2013 Elsevier B. V.保留所有权利
Highest time resolution in scintillator based detectors is becoming more and more important. In medical detector physics L(Y)SO scintillators are commonly used for time of flight positron emission tomography (TOP-PET). Coincidence time resolutions (CTRs) smaller than 100 ps FWHM are desirable in order to improve the image signal to noise ratio and thus give benefit to the patient by shorter scanning times. Also in high energy physics there is the demand to improve the timing capabilities of calorimeters down to 10 ps. To achieve these goals it is important to study the whole chain, i.e. the high energy particle interaction in the crystal, the scintillation process itself, the scintillation light transfer in the crystal, the photocletector and the electronics. Time resolution measurements for a PET like system are performed with the time-over-threshold method in a coincidence setup utilizing the ultra-fast amplifier-discriminator NINO. With 2 x 2 x 3 mm(3) LSO:Ce codoped 0.4%Ca crystals coupled to commercially available SiPMs (Hamamatsu S10931-050P MPPC) we achieve a CTR of 108 +/- 5 ps FWHM at an energy of 511 keV. Under the same experimental conditions an increase in crystal length to 5 mm deteriorates the CTR to 123 +/- 7 ps FWHM, 10 mm to 143 +/- 7 ps FWHM and 20 mm to 176 +/- 7 ps FWHM. This degradation in CTR is caused by the light transfer efficiency (LTE) and light transfer time spread (LTTS) in the crystal. To quantitatively understand the measured values, we developed a Monte Carlo simulation tool in MATLAB incorporating the timing properties of the photodetector and electronics, the scintillation properties of the crystal and the light transfer within the crystal simulated by SLITRANI. In this work, we show that the predictions of the simulation are in good agreement with the experimental data. We conclude that for longer crystals the deterioration in CTR is mainly caused by the LTE, i.e the ratio of photons reaching the photodetector to the total amount of photons generated by the scintillation whereas the MS influence is partly offset by the gamma absorption in the crystal, (C) 2013 Elsevier B.V. All rights reserved