Enhanced diode laser ablation using submucosal injection of indocyanine green solution: Part I ; Irradiation to the resected porcine gastric walls and canine gastric walls under laparotomy

High-power diode laser ablation with indocyanine green (ICG) solution injection to the submucosal layer was evaluated for the treatment of early gastric cancer. The diode laser beam with 805nm in wavelength was irradiated to the resected porcine gastric wall and canine gastric wall under laparotomy with ICG solution (1 mg/ml) injection. The injected ICG solution was used to enhance the tissue absorption of the submucosa to the diode laser emission. The gastric wall with 5% glucose solution injection was also prepared to compare the ablation characteristics. Using 12 or 25 W of the laser power with 2mm diameter beam, we found the ICG injected submucosa was completely ablated by the diode laser radiation. We could apply the high intensity diode laser beam, because ICG dyed layer prevented direct laser penetration to muscularis propriae. Although the laser irradiation easily removed the mucosal layer in the case with saline injection, it could not ablated the submucosa with 12 W. We could easily judge the ablated depth by surface color change. When ICG dyed submucosal layer was completely removed, the muscularis propriae was recognized by thin brown color. We think these findings were extremely important, because we can prevent gastric perforation by endoscopic observation of color change of the ablated surface.