Abstract

In bum surgery necrotic tissue has to be removed prior to grafting. Tangential excision causes high blood loss and destruction of viable tissue. Pulsed infrared laser ablation can overcome both problems because of its high precision and the superficial coagulation of the remaining tissue. We investigated the ablation noise to realize an acoustic feedback system for a selective removal of necrotic tissue. We studied free-running Er:YAG laser ablation of gelatin and burnt skin. Acoustic signals were detected by a condenser microphone and a piezoelectric airborne transducer. Tissue discrimination was based on the evaluation of the normalized acoustic energy. The normalized acoustic energy differs significantly between gelatin samples of different water content and between necrotic and vital tissue. The normalized acoustic energy is a suitable parameter for the discrimination between necrotic and vital tissue.

© 1999 Optical Society of America