A new approach of intra-operative real time diagnosis of metastasis by positron probe in gastroenterological carcinomas

（1）术中应用的正电子探针的开发Apollomec公司开发了具有两种类型探测器的正电子探针，用于β射线的塑料闪烁体和用于γ射线的BGO晶体。只有当同时探测到两条射线时，该探测器才算作真实的事件，以降低背景水平。（2）放射性同位素临床应用委员会我们的临床应用方案是计划在手术前在P3室注射^ F-FDG后，在手术过程中通过正电子探针测量放射性<18>。因此，<18>在上述委员会中评估了^ F对人体的影响。因此，委员会批准了^ F的使用<18>，因为它的半衰期很短，对人体的影响很小。（3）1F-FDG的注射时间的检查<18>事实上，需要延迟开始手术以在手术前注射<18>1F-FDG，因为合成和纯化1F-FDG需要时间<18>。因此，我们检查了<18><18>在手术前一天晚上注射^ F-FDG时是否可以测量^ F的放射性。^ F的半衰期<18>为109.8分钟。理论上，假设在注射16小时后测量，放射性降低至约1/256。我们对食管鳞癌巨大淋巴结转移患者次日早晨用γ探针测量放射性，但其计数非常细微，因此发现前一天注射的方案不适用于临床。结论<18>：FDG引导下的手术仍有许多问题有待解决，但FDG引导下的手术有可能成为提高手术质量的一个新的突破口。

(1)Development of positron probe for intra-operative applicationApollomec corporation developed positron probe with two types of detectors, plastic scintillator for beta rays and BGO crystal for gamma rays. This probe counts as a real event only when both rays are detected simultaneously in order to reduce background level.(2)Committee on clinical application of radioisotopeOur protocol in clinical application is planned to measure radioactivity by positron probe during operation after injection of ^<18>F-FDG in P3 room just before operation. Therefore, the influence to the human body of ^<18>F was evaluated in above-mentioned committee. As a result, the committee approved the usage of ^<18>F, because that half life is very short and the influence to the human body is very little.(3)Examination of injection time of ^<18>F-FDGAs a matter of fact, to delay to start operation is needed to inject ^<18>F-FDG just before operation, because it takes a time to synthesize and purify ^<18>F-FDG. Therefore, we examined whether radioactivity of ^<18>F could be measured or not when ^<18>F-FDG was injected in the evening of the day before operation. The half life of ^<18>F is 109.8 minute. Theoretically, radioactivity is reduced to about 1/256, assuming to measure after 16 hours of injection. We measured radioactivity by gamma probe next morning in patients of esophageal squamous cell carcinoma with huge lymph node metastasis, however, its count was very subtle, so that this protocol of previous day injection was found not to be clinically applicable. Above all, the necessity of injection of ^<18>F-FDG just before operation was suggested to maintain diagnostic quality and accuracy by positron probe.Conclusion : A lot of issues to have to be resolved are still remained, however, FDG-guided surgery may be the promising new approach to have a potential as a breakthrough of quality of surgery.