First Results with Ablating Superficial Cell Layers of the Porcine Vocal Fold Using a Femtosecond Laser

Abstract

Summary Most of benign, precancerous and malignant epithelial lesions in the human endolarynx, especially the vocal fold require a highly precise and controllable therapy, providing an effective ablation of injured tissue under functional preservation of adjacent structures. The dominant instrument currently used in clinical laser surgery is the CO 2 laser. However, CO 2 laser therapies in the endolarynx may result in severe postoperative risks like impairment of the vocal fold and voice quality. The femtosecond (fs) lasers available today are mainly characterized by extreme short pulses ranging from about 10 fs (10 −14 s) to 1 ps (10 −12 s) and single pulse powers in the range of gigawatts (10 9 W) to terawatts (10 12 W). Thus a fs laser enables the exact ablation of cells or superficial cell layers in target tissue by inducing microplasms during nonlinear absorption processes directly on the target. This process minimizes thermal and mechanical stress into surrounding tissues (“cold ablation”). In this basic study we tried to ablate small volumes of cells from a highly sensitive tissue using an experimental fs laser system without producing secondary damages in the periphery of the lased area. The vocal folds of a porcine larynx were used as a tissue model. First results showed that minimal ablation depths below 200 μm were achieved when a 350 μJ pulse energy and a scan rate of 1mm/s were applied. No defects were observed in the structures beneath the ablated area. Therefore, fs lasers may be suitable for the therapy of superficial small-volume lesions in the endolarynx. This has to be validated in further preclinical studies.