Towards monolithic scintillator based TOF-PET systems: practical methods for detector calibration and operation
Towards monolithic scintillator based TOF-PET systems: practical methods for detector calibration and operation
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DOI：
10.1088/0031-9155/61/13/4904
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发表时间：
2016-07-07
影响因子：
3.5
通讯作者：
Schaart, Dennis R.
中科院分区：
文献类型：
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作者：
Borghi, Giacomo;Tabacchini, Valerio;Schaart, Dennis R.
基于厚单片闪烁体晶体的伽马射线探测器可以实现< 2 mm的半高全宽（FWHM）和优于200 ps FWHM的符合分辨时间（CRT）。此外，它们提供高灵敏度和交互深度（DOI）信息。虽然这些是临床飞行时间（TOF）正电子发射断层扫描（PET）的优良特性，但到目前为止，单片闪烁体的应用受到位置和相互作用时间估计所需的冗长而复杂的程序的阻碍。在这里，以前在我们的小组开发的算法进行了修订，使大量的单片闪烁体探测器在TOF-PET系统的实际校准和操作。特别是，用于x，y位置估计的k最近邻（k-NN）分类方法通过一种快速预选最有用的参考事件的算法来加速，从而将位置估计的计算时间减少了大约200倍。与之前发布的k-NN 1D方法相比。此外，估计的DOI和时间的相互作用的程序进行了修订，使完整的探测器校准，通过扇束或泛光照射。此外，提出了一种新技术，以允许使用其中一些光电传感器像素值和/或时间戳丢失（例如，由于死区时间）的事件，以便进一步增加系统灵敏度。加速方法在专门为临床PET应用开发的单片闪烁体探测器上进行测试，该探测器由32 mm x 32 mm x 22 mm LYSO：Ce晶体与数字光子计数器（DPC）阵列耦合组成。这导致空间分辨率为1.7 mm FWHM，平均DOI分辨率为3.7 mm FWHM，CRT为214 ps。此外，示出了使用丢失64个光电传感器像素中多达16个的信息的事件的可能性。这导致检测器性能的仅小的劣化。
Gamma-ray detectors based on thick monolithic scintillator crystals can achieve spatial resolutions < 2 mm full-width-at-half-maximum (FWHM) and coincidence resolving times (CRTs) better than 200 ps FWHM. Moreover, they provide high sensitivity and depth-of-interaction (DOI) information. While these are excellent characteristics for clinical time-of-flight (TOF) positron emission tomography (PET), the application of monolithic scintillators has so far been hampered by the lengthy and complex procedures needed for position-and time-of-interaction estimation. Here, the algorithms previously developed in our group are revised to make the calibration and operation of a large number of monolithic scintillator detectors in a TOF-PET system practical. In particular, the k-nearest neighbor (k-NN) classification method for x, y-position estimation is accelerated with an algorithm that quickly preselects only the most useful reference events, reducing the computation time for position estimation by a factor of similar to 200 compared to the previously published k-NN 1D method. Also, the procedures for estimating the DOI and time of interaction are revised to enable full detector calibration by means of fan-beam or flood irradiations only. Moreover, a new technique is presented to allow the use of events in which some of the photosensor pixel values and/or timestamps are missing (e.g. due to dead time), so as to further increase system sensitivity. The accelerated methods were tested on a monolithic scintillator detector specifically developed for clinical PET applications, consisting of a 32 mm x 32 mm x 22 mm LYSO : Ce crystal coupled to a digital photon counter (DPC) array. This resulted in a spatial resolution of 1.7 mm FWHM, an average DOI resolution of 3.7 mm FWHM, and a CRT of 214 ps. Moreover, the possibility of using events missing the information of up to 16 out of 64 photosensor pixels is shown. This results in only a small deterioration of the detector performance.