Li Xiaoli, Lockhart Cate, Lewellen Tom K, Miyaoka Robert S
University of Washington Department of Physics, Seattle, WA USA (phone: 206-543-0629; fax: 206-543-8356;
IEEE Trans Nucl Sci. 2011;58(3):590-596. doi: 10.1109/TNS.2011.2119378.
The spatial resolution performance characteristics of a monolithic crystal PET detector utilizing a sensor on the entrance surface (SES) design is reported. To facilitate this design, we propose to utilize a 2D silicon photomultiplier (SiPM) array device. Using a multi-step simulation process, we investigated the performance of a monolithic crystal PET detector with different data readout schemes and different SiPM parameters. The detector simulated was a 49.2mm by 49.2mm by 15mm LYSO crystal readout by a 12 by 12 array of 3.8mm by 3.8mm SiPM elements. A statistics based positioning (SBP) method was used for event positioning and depth of interaction (DOI) decoding. Although individual channel readout provided better spatial resolution, row-column summing is proposed to reduce the number of readout channels. The SiPM parameters investigated include photon detection efficiency (PDE) and gain variability between different channels; PDE and gain instability; and dark count noise. Of the variables investigated, the PDE shift of -3.2±0.7% and gain shift of -4±0.9% between detector testing and detector calibration had the most obvious impact on the detector performance, since it not only degraded the spatial resolution but also led to bias in positioning, especially at the edges of the crystal. The dark count noise also had an impact on the intrinsic spatial resolution. No data normalization is required for PDE variability of up to 12% FWHM and gain variability of up to 15% FWHM between SiPM channels. Based upon these results, a row-column summing readout scheme without data normalization will be used. Further, we plan to cool our detectors below room temperature to reduce dark count noise and to actively control the temperature of the SiPMs to reduce drifts in PDE and gain.
报告了一种采用入射表面传感器（SES）设计的单片晶体正电子发射断层显像（PET）探测器的空间分辨率性能特征。为便于实现这种设计，我们建议使用二维硅光电倍增管（SiPM）阵列器件。通过多步模拟过程，我们研究了具有不同数据读出方案和不同SiPM参数的单片晶体PET探测器的性能。所模拟的探测器是一个尺寸为49.2mm×49.2mm×15mm的LYSO晶体，由一个12×12阵列的3.8mm×3.8mm SiPM元件读出。基于统计的定位（SBP）方法用于事件定位和相互作用深度（DOI）解码。尽管单通道读出提供了更好的空间分辨率，但建议采用行列求和以减少读出通道的数量。所研究的SiPM参数包括光子探测效率（PDE）和不同通道之间的增益变化；PDE和增益不稳定性；以及暗计数噪声。在所研究的变量中，探测器测试和探测器校准之间PDE偏移-3.2±0.7%和增益偏移-4±0.9%对探测器性能的影响最为明显，因为这不仅降低了空间分辨率，还导致定位偏差，尤其是在晶体边缘。暗计数噪声也对固有空间分辨率有影响。SiPM通道之间PDE变化高达12%半高宽（FWHM）和增益变化高达15% FWHM时无需数据归一化。基于这些结果，将采用无需数据归一化的行列求和读出方案。此外，我们计划将探测器冷却至室温以下以降低暗计数噪声，并积极控制SiPM的温度以减少PDE和增益的漂移。
