Laser-assisted Hair transplantation: Histological Comparison Between Holmium:YAG and CO_2 Lasers

摘要

The histological effects of flash-scanned CO_2 (λ = 10.6μm) and pulsed Holmium:YAG (Ho:YAG, λ = 2.12μm) lasers were evaluated in human scalp following the creation of hair transplant recipient channels. Ho:YAG laser irradiation created larger zones of thermal injury (superficial de-epitheliazation, thermal necrosis, and thermal damage) adjacent to the laser channels than irradiation with the CO_2 laser device. When the two lasers created recipient sites of nearly equal depth, the Holmium:YAG laser caused a larger region of lateral thermal damage (589.30μm) than the CO_2 laser (118.07μm). In addition, Holmium:YAG irradiated specimens exhibited fractures or discontinuities beyond the region of clear thermal injury. This shearing effect is consistent with the photoacoustic mechanism of ablation associated with pulsed mid-IR laser irradiation. In contrast, channels created with the CO_2 exhibited minimal epithelial disruption and significantly less lateral thermal damage. While the Holmium:YAG laser is a useful tool for ablating soft tissue with minimal char in select applications (sinus surgery, arthroscopic surgery), this study suggests that the use of the CO_2 laser for the creation of transplantation recipient channels results in significantly less lateral thermal injury for the laser parameters employed.