Low-invasive Soft Tissue Incision with 6.1.MU.m-light Irradiation-Gelatin Ablation Properties-
For low-invasive laser treatment, stable absorption properties of tissue during laser treatment are essentially needed, which enable us to predict irradiation effect (ablation depth, thermally-altered depth) using them. There are water and proteins as main absorber in the mid-infrared range. During laser treatment, the absorption properties of soft tissue are changed due to laser-induced temperature rise and leading to the induction of unexpected irradiation effects. We have proposed and demonstrated a novel, low-invasive laser surgery with 6.1-μm-light irradiation. 6.1-μm-light can resonantly excite both OH bending (water) and amide-I (proteins). The absorption properties of soft tissue during laser treatment would be come considerably stable because they do not remarkably depend on the surrounding temperature and the water concentration. We examined the gelatin ablation properties by λ=6.1-μm irradiation using a tunable mid-infrared Free-Electron Laser and showed that λ=6.1-μm irradiation is one of the candidates for a low-invasive soft tissue incision. Gelatins were used as a model substrate for soft tissue. From these experiments, it was found as follows. (1) Enhanced gelatin ablation occurred near λ=6.1-μm, but not λ=6.45-μm (Amide II of proteins). (2) The gelatins were removed due to water vaporization, which is reflected in the static absorption properties of the gelatin before laser irradiation. Thus, we showed the applicability of λ=6.1-μm -light for a new light source to realize a low-invasive soft tissue incision.