Department of Radiation Radionuclides and Reactors, Applied Sciences, Delft University of Technology, JB Delft, The Netherlands.
Phys Med Biol. 2012 Nov 21;57(22):7709-24. doi: 10.1088/0031-9155/57/22/7709. Epub 2012 Nov 2.
High spatial resolution γ-imaging can be achieved with scintillator readout by low-noise, fast, electron-multiplying charge-coupled devices (EMCCDs). Previously we have shown that false-positive events due to EMCCD noise can be rejected by using the sum signal from silicon photomultipliers (SiPMs) mounted on the sides of the scintillator. Here we launch a next generation hybrid CCD-SiPM camera that utilizes the individual SiPM signals and maximum likelihood estimation (MLE) pre-localization of events to discriminate between true and false events in CCD frames. In addition, SiPM signals are utilized for improved energy discrimination. The performance of this hybrid detector was tested for a continuous CsI:Tl crystal at 140 keV. With a pre-localization accuracy of 1.06 mm (full-width-at-half-maximum) attained with MLE the signal-to-background ratio (SBR) was improved by a factor of 5.9, 4.0 or 2.2 compared to the EMCCD-only readout, at the cost of rejecting, respectively, 47%, 9% or 4% of the events. Combining the pre-localization and SiPM energy estimation improved the energy resolution from 50% to (19 ± 3)% while maintaining the spatial resolution at 180 µm.
高空间分辨率γ成像可以通过低噪声、高速、电子倍增电荷耦合器件（EMCCD）的闪烁体读出来实现。此前，我们已经表明，通过使用安装在闪烁体侧面的硅光电倍增管（SiPM）的总和信号，可以拒绝由于 EMCCD 噪声引起的假阳性事件。在这里，我们推出了一种下一代混合 CCD-SiPM 相机，它利用单个 SiPM 信号和最大似然估计（MLE）对事件的预定位来区分 CCD 帧中的真实事件和假事件。此外，SiPM 信号用于提高能量鉴别能力。该混合探测器的性能在 140keV 的连续 CsI:Tl 晶体上进行了测试。通过 MLE 实现了 1.06mm（半峰全宽）的预定位精度，与仅使用 EMCCD 读出相比，信号与背景比（SBR）提高了 5.9、4.0 或 2.2 倍，代价分别是拒绝 47%、9%或 4%的事件。结合预定位和 SiPM 能量估计，在保持空间分辨率为 180µm 的同时，将能量分辨率从 50%提高到（19±3）%。
