Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, CA 95616, USA.
Phys Med Biol. 2011 Oct 7;56(19):6327-36. doi: 10.1088/0031-9155/56/19/011. Epub 2011 Sep 6.
After many years of development, position-sensitive avalanche photodiodes (PSAPDs) are now being incorporated into a range of scintillation detector systems, including those used in high-resolution small-animal PET and PET/MR scanners. In this work, the signal, noise, signal-to-noise ratio (SNR), flood histogram and timing resolution were measured for lutetium oxyorthosilicate (LSO) scintillator arrays coupled to PSAPDs ranging in size from 10 to 20 mm, and the optimum bias voltage and working temperature were determined. Variations in the SNR performance of PSAPDs with the same dimensions were small, but the SNR decreased significantly with increasing PSAPD size and increasing temperature. Smaller PSAPDs (10 mm and 15 mm in width) produced acceptable flood histograms at 24 °C, and cooling lower than 16 °C produced little improvement. The optimum bias voltage was about 25 V below the break down voltage. The larger 20 mm PSAPDs have lower SNR and require cooling to 0-7 °C for acceptable performance. The optimum bias voltage is also lower (35 V or more below the break down voltage depending on the temperature). Significant changes in the timing resolution were observed as the bias voltage and temperature varied. Higher bias voltages provided better timing resolution. The best timing resolution obtained for individual crystals was 2.8 ns and 3.3 ns for the 10 mm and 15 mm PSAPDs, respectively. The results of this work provide useful guidance for selecting the bias voltage and working temperature for scintillation detectors that incorporate PSAPDs as the photodetector.
经过多年的发展，位置灵敏型雪崩光电二极管（PSAPD）现已被应用于一系列闪烁探测器系统中，包括用于高分辨率小动物 PET 和 PET/MR 扫描仪的系统。在这项工作中，我们测量了尺寸范围为 10 至 20 毫米的硅酸镥（LSO）闪烁体阵列与 PSAPD 耦合的信号、噪声、信噪比（SNR）、洪水直方图和定时分辨率，并确定了最佳偏置电压和工作温度。尽管具有相同尺寸的 PSAPD 的 SNR 性能变化很小，但随着 PSAPD 尺寸和温度的增加，SNR 显著下降。较小的 PSAPD（宽度为 10 毫米和 15 毫米）在 24°C 时可产生可接受的洪水直方图，而冷却至 16°C 以下几乎没有改善。最佳偏置电压约为击穿电压以下 25V。较大的 20 毫米 PSAPD 的 SNR 较低，需要冷却至 0-7°C 才能获得可接受的性能。最佳偏置电压也较低（取决于温度，低于击穿电压 35V 或更多）。随着偏置电压和温度的变化，定时分辨率发生了明显的变化。较高的偏置电压可提供更好的定时分辨率。对于单个晶体，获得的最佳定时分辨率分别为 2.8ns 和 3.3ns，适用于 10 毫米和 15 毫米 PSAPD。这项工作的结果为选择包含 PSAPD 作为光电探测器的闪烁探测器的偏置电压和工作温度提供了有用的指导。
