Judenhofer Martin S, Pichler Bernd J, Cherry Simon R
Department of Biomedical Engineering, University of California, Davis, 95616, USA.
Phys Med Biol. 2005 Jan 7;50(1):29-44. doi: 10.1088/0031-9155/50/1/003.
Detectors used for positron emission tomography (PET) provide fast, randomly distributed signals that need to be digitized for further processing. One possibility is to sample the signals at the peak initiated by a trigger from a constant fraction discriminator (CFD). For PET detectors, simultaneous acquisition of many channels is often important. To develop and evaluate novel PET detectors, a flexible, relatively low cost and high performance laboratory data acquisition (DAQ) system is therefore required. The use of dedicated DAQ systems, such as a multi-channel analysers (MCAs) or continuous sampling boards at high rates, is expensive. This work evaluates the suitability of well-priced peripheral component interconnect (PCI)-based 8-channel DAQ boards (PD2-MFS-8 2M/14 and PD2-MFS-8-500k/14, United Electronic Industries Inc., Canton, MA, USA) for signal acquisition from novel PET detectors. A software package was developed to access the board, measure basic board parameters, and to acquire, visualize, and analyse energy spectra and position profiles from block detectors. The performance tests showed that the boards input linearity is >99.2% and the standard deviation is <9 mV at 10 V for constant signals. Synchronous sampling of multiple channels and external synchronization of more boards are possible at rates up to 240 kHz per channel. Signals with rise times as fast as 130 ns (<2 V amplitude) can be acquired without slew rate effects. However, for signals with amplitudes of up to 5 V, a rise time slower than 250 ns is required. The measured energy resolution of a lutetium oxyorthosilicate (LSO)-photomultiplier tube (PMT) detector with a 22Na source was 14.9% (FWHM) at 511 keV and is slightly better than the result obtained with a high-end single channel MCA (8000A, Amptek, USA) using the same detector (16.8%). The crystals (1.2 x 1.2 x 12 mm3) within a 9 x 9 LSO block detector could be clearly separated in an acquired position profile. Thus, these boards are well suited for data acquisition with novel detectors developed for nuclear imaging.
用于正电子发射断层扫描（PET）的探测器会提供快速、随机分布的信号，这些信号需要进行数字化处理以便进一步分析。一种方法是在由恒比甄别器（CFD）触发产生的信号峰值处对信号进行采样。对于PET探测器而言，同时采集多个通道的数据通常很重要。因此，为了研发和评估新型PET探测器，需要一个灵活、成本相对较低且高性能的实验室数据采集（DAQ）系统。使用专用的DAQ系统，如多通道分析仪（MCA）或高速连续采样板，成本很高。本研究评估了价格合理的基于外围组件互连（PCI）的8通道DAQ板（PD2-MFS-8 2M/14和PD2-MFS-8-500k/14，美国联合电子工业公司，坎顿，马萨诸塞州）对于从新型PET探测器采集信号的适用性。开发了一个软件包来访问该板卡、测量基本板卡参数，并采集、可视化和分析来自块状探测器的能谱和位置分布图。性能测试表明，对于恒定信号，该板卡的输入线性度>99.2%，在10 V时标准偏差<9 mV。多个通道可实现同步采样，并且多个板卡可进行外部同步，每个通道的采样速率高达240 kHz。对于上升时间快至130 ns（幅度<2 V）的信号，采集时不会产生压摆率效应。然而，对于幅度高达5 V的信号，需要上升时间慢于250 ns。使用22Na源的硅酸镥（LSO）-光电倍增管（PMT）探测器测得的能量分辨率在511 keV时为14.9%（半高宽），略优于使用同一探测器的高端单通道MCA（8000A，美国Amptek公司）所得到的结果（16.8%）。在采集到的位置分布图中，可以清晰地分辨出9×9 LSO块状探测器内的晶体（1.2×1.2×12 mm3）。因此，这些板卡非常适合用于为核成像开发的新型探测器的数据采集。
