Laparoscopic detection of sentinel node in gastric cancer surgery by indocyanine green fluorescence imaging

Indocyanine green (ICG) fluorescence imaging is a promising technique for detection of sentinel node (SN) as it avoids unnecessary resection. However, the ICG fluorescence imaging system cannot be used in laparoscopic surgery because of technological difficulties. A prototype laparoscopic detection system comprising an electron multiplier charge-coupled device (EM-CCD) as the detector and a xenon lamp as the light source was developed. The CCD camera head was attached to the end of a specially designed laparoscope that could transmit ICG fluorescence. The system allows visualization of both color and fluorescence images. Laparoscopic surgery in ten patients with gastric cancer included SN biopsy using ICG dye, ICG fluorescence images using our system, and laparoscopy-assisted gastrectomy (LAG) with lymphadenectomy. SNs were sliced into 2-mm sections for histological examination and imprint cytology. Immediately after intraoperative ICG injection by endoscopy, the laparoscopic ICG fluorescence imaging system allowed easy visualization of the lymphatic vessels draining from the primary gastric tumor toward the lymph nodes and traced the moving injected dye, whereas lymph vessels and nodes were hardly recognized by ICG green color through a standard laparoscope. Surgeons could confirm the removed lymph nodes stained with ICG by fluorescent imaging. SNs were successfully detected in all patients. Three patients had suspicious metastases in the SNs; two patients had lymph node metastases only in the SNs. Our newly developed laparoscopic ICG fluorescence imaging system is promising in the detection of SNs in laparoscopic gastric cancer surgery. The preliminary results suggest an easier and shorter learning curve of dye-guided SN biopsy in laparoscopic gastric surgery.