Optimized Preoperative Peritumoral ICG Injection

Early in the study, ICG (Dongindang Pharmaceutical) was diluted using distilled water to a concentration of 1.25 mg/ml. At four points around the primary tumour, 0.6 ml ICG solution was endoscopically injected into the submucosal layer on the day before surgery during a routine endoscopic preoperative localization process. Thus, a total of 3 mg ICG was used. However, with the advancement in fluorescent imaging devices, the administered amount of ICG was subsequently reduced. The da Vinci Si (Intuitive Surgical) System employs a conventional laparoscopic camera arrangement with an externally placed camera. In contrast, the da Vinci Xi (Intuitive Surgical) System uses an inside-the-patient chip-on-a-tip configuration, resulting in higher sensitivity to fluorescent signals and displaying stronger signals^{22 (link)}.
As a result of system differences and enhancements in fluorescent imaging sensitivity, the concentration of ICG needed to be optimized. From 2015 onward, ICG was diluted to a concentration of 0.625 mg/ml, and the total amount of ICG used was 1.5 mg, which is half the amount of the previously used. The feasibility of this institutional preoperative peritumoral ICG injection protocol has previously been reported^{15 (link)–17 (link),19 (link),23 (link)}.