Estimated random rate for an intraoperative use of the forceps-type coincidence detector

In surgical cancer treatment, extensive lymph node (LN) dissection has been noted as being related to postoperative complications. On the other hand, it has also been reported that approximately 95% of the resected LNs in esophagectomy were not metastases. Therefore, optimization of LN dissection with intraoperative LN diagnosis is expected to reduce postoperative complications. As a biomarker for LNs metastasis,
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F-fluoro-2-deoxy-D-glucose (FDG) provides a high diagnostic performance in positron emission tomography (PET). To realize intraoperative FDG-PET measurement for individual LNs, we have proposed a forceps-type coincidence detector, which consists of a pair of small scintillation detectors mounted on the head of a forceps to detect an annihilation-radiation pair. The proposed device can quantify activity concentration in a small area between the heads of its forceps. However, most of the injected FDG spreads over organs outside of the field-of-detection of the device, which may increase the random rate, and statistical error of the LN activity measurement should be carefully assessed with a practical short data acquisition time such as 30 s. In this research, we simulated LN diagnosis with the proposed forceps-type coincidence detector (with BGO crystals) by modeling an actual FDG distribution in each organ. With a clinically typical injection dose of FDG and at the time of two half-lives of
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F passing, the random fraction was less than 30% and the statistical error was less than 5 %, which supported the feasibility of in-vivo use of our forceps-type coincidence detector currently under development.