Enhanced diode laser ablation using submucosal injection of indocyanine green solution: Part II ; - Endoscopic irradiation to the canine stomach

Endoscopic diode laser ablation using indocyanine green (ICG) was performed to the canine stomach to assess the safety and efficacy for the treatment of early gastric cancer. Approximately 8 ml of ICG solution with the concentration of 1 mg/ml was administrated to the submucosal layer so that the mucosal surface was elevated within the limits of 4 cm in diameter. Twenty five watts non-contact with 3 mm beam spot diameter was irradiated to the gastric wall by the 1 second pulse mode. With this irradiated condition, 4 or 5 repeat irradiation could remove the mucosal layer without carbonization. The ICG containing submucosal layer was efficiently ablated even with laser output of 5W. By observing the color tone of the irradiated surface, we could judge the ablation depth. Histological examination revealed the submucosal layer was almost eliminated when the irradiated surface presented light green or yellowish green. In this case the muscularis propriae was not damaged because the ICG solution blocked the direct laser penetration. Six days after irradiation, endoscopic examination and histological examination showed satisfactory healing process. We think this combination therapy using diode laser irradiation and the ICG solution injection into the submucosal layer would be useful for early gastric cancer with/without the submucosal invasion, especially in inoperable cases.