Purpose

Conventional positron emission tomography can be used only preoperatively to identify lymph node metastases, and hence, these growths are difficult to locate intraoperatively. Previously, an intraoperative laparoscopic coincidence imaging system, with an external fixed detector array and a detector probe that can be moved and inserted into the stomach, was proposed to identify lymph node metastases during stomach cancer surgery. This paper proposes a prototype detector for this system.

Methods

GAGG:Ce (Gd₃Al₂Ga₃O₁₂:Ce) scintillator crystals, one to one coupled with silicon photomultipliers (SiPMs), were used to identify 511 keV photons. An optical tracking system followed the position and orientation of the movable detector. SiPM outputs were read out by time-over-threshold (TOT)-based application-specific integrated circuits, which converted the electrical charges into digital pulses. To identify the arrival time, channel number, and pulse width, which indicate the energy information of each TOT output, a data acquisition system was developed based on a field-programmable gate array.

Results

The spatial resolution of the reconstructed images in lateral direction was better than 7 mm, but that of depth direction was limited, owing to inadequate projections. The prototype successfully reconstructed 44 kBq ¹⁸F-fluorodeoxyglucose sources during a 2-min scan.

Conclusion

We developed a prototype detector for an intraoperative laparoscopic coincidence imaging system. The prototype detector was evaluated successfully, and the produced images were similar to those obtained in the simulation results, thereby suggesting that this method offers a new possibility of imaging lymph node metastases intraoperatively.

中文翻译：

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带有PET示踪剂的术中腹腔镜符合成像系统原型检测器的开发和评估

目的

常规的正电子发射断层扫描只能在术前用于识别淋巴结转移，因此，这些生长很难在术中定位。以前，有人提出了一种术中腹腔镜符合成像系统，该系统具有外部固定的探测器阵列和可以移动并插入胃中的探测器探头，以识别胃癌手术期间的淋巴结转移。本文提出了该系统的原型检测器。

方法

与硅光电倍增管（SiPM）一对一耦合的GAGG：Ce（Gd ₃ Al ₂ Ga ₃ O ₁₂：Ce）闪烁体晶体被用来识别511 keV光子。光学跟踪系统遵循可移动探测器的位置和方向。SiPM输出由基于阈值时间（TOT）的专用集成电路读出，该集成电路将电荷转换为数字脉冲。为了确定表示每个TOT输出的能量信息的到达时间，通道号和脉冲宽度，开发了一种基于现场可编程门阵列的数据采集系统。

结果

重建图像的横向空间分辨率优于7 mm，但由于投影不足，深度方向的空间分辨率受到限制。该原型在2分钟的扫描过程中成功地重建了44 kBq ¹⁸ F-氟脱氧葡萄糖源。

结论

我们为术中腹腔镜符合成像系统开发了原型检测器。对原型检测器进行了成功的评估，所产生的图像与模拟结果中获得的图像相似，从而表明该方法为术中成像淋巴结转移提供了新的可能性。