Abstract
In this paper, we examine the pressure level and the wave form, which is the sound produced when incising biological tissue using a TEA-CO2 laser and a Middle-Infrared Free Electron Laser (MIR-FEL). The laser induced-sound pressure level is measured using a transducer with sensitivity in the range of 20 Hz to 70 kHz. We investigated the characteristics of sounds produced by the incision of soft and hard biological tissue using a laser. Focusing on the surface of the gelatin sample (a soft tissue), specifically on the water content at the point of incision, we estimated the water content from the surface electrical resistance, and found that there is a clear correlation between with the sound pressure level and the water content. Furthermore, we studied the FEL induced-sound of a wavelength around 10 μm for a hard biological tissue (a bone). As for the induced-sound wave form, we discovered that it was different to the result by the wavelength. This research is discussed in terms of the development of a photo-acoustic monitoring system for a safe, reliable laser scalpel and laser coagulation device.
