Multi-tracer positron emission tomography (PET) imaging can be accomplished by applying multi-tracer compartment modeling. Recently, a method has been proposed in which the arterial input functions (AIFs) of the multi-tracer PET scan are explicitly derived. For that purpose, a gamma spectroscopic analysis is performed on blood samples manually withdrawn from the patient when at least one of the co-injected tracers is based on a non-pure positron emitter. Alternatively, these blood samples required for the spectroscopic analysis may be obtained and analyzed on site by an automated detection device, thus minimizing analysis time and radiation exposure of the operating personnel. In this work, a new automated blood sample detector based on silicon photomultipliers (SiPMs) for single- and multi-tracer PET imaging is presented, characterized, and tested in vitro and in vivo. The detector presented in this work stores and analyzes on-the-fly single and coincidence detected events. A sensitivity of 22.6 cps/(kBq/mL) and 1.7 cps/(kBq/mL) was obtained for single and coincidence events respectively. An energy resolution of 35% full-width-half-maximum (FWHM) at 511 keV and a minimum detectable activity of 0.30 ± 0.08 kBq/mL in single mode were obtained. The in vivo AIFs obtained with the detector show an excellent Pearson’s correlation (r = 0.996, p < 0.0001) with the ones obtained from well counter analysis of discrete blood samples. Moreover, in vitro experiments demonstrate the capability of the detector to apply the gamma spectroscopic analysis on a mixture of 68Ga and 18F and separate the individual signal emitted from each one. Characterization and in vivo evaluation under realistic experimental conditions showed that the detector proposed in this work offers excellent sensibility and stability. The device also showed to successfully separate individual signals emitted from a mixture of radioisotopes. Therefore, the blood sample detector presented in this study allows fully automatic AIFs measurements during single- and multi-tracer PET studies.

中文翻译：

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使用伽马能谱仪开发用于多示踪正电子发射断层扫描的血液样本检测器

多示踪正电子发射断层扫描（PET）成像可通过应用多示踪隔室建模来完成。近来，已经提出了一种方法，在该方法中，明确导出多示踪PET扫描的动脉输入函数（AIF）。为此，当至少一个共注入示踪剂是基于非纯正电子发射体时，对从患者手动抽取的血液样本进行伽马能谱分析。或者，可以通过自动检测设备获取并进行光谱分析所需的这些血液样本，从而将分析时间和操作人员的辐射暴露降至最低。在这项工作中，提出了一种新型的基于硅光电倍增管（SiPM）的自动血液样本检测器，用于单迹线和多迹线PET成像，并在体内和体外进行了测试。这项工作中介绍的检测器可以存储并分析即时的单个事件和巧合事件。单个事件和巧合事件的灵敏度分别为22.6 cps /（kBq / mL）和1.7 cps /（kBq / mL）。在单模模式下，获得了511 keV的35％全宽半最大值（FWHM）的能量分辨率和0.30±0.08 kBq / mL的最小可检测活性。用检测器获得的体内AIF与通过对离散血样进行良好的反分析得到的Pearson相关性很好（r = 0.996，p <0.0001）。此外，体外实验证明了检测器能够对68Ga和18F的混合物进行伽玛光谱分析，并分离出每个发出的信号。在实际实验条件下的表征和体内评估表明，这项工作中提出的检测器具有出色的灵敏度和稳定性。该设备还证明可以成功地分离出放射性同位素混合物发出的各个信号。因此，本研究中介绍的血液样本检测器允许在单示踪和多示踪PET研究中进行全自动AIF测量。