Coagulation and ablation of biological soft tissue by quantum cascade laser with peak wavelength of 5.7 μm

Abstract

Molecules such as water, proteins and lipids that are contained in biological tissue absorb mid-infrared (MIR) light, which allows such light to be used in laser surgical treatment. Esters, amides and water exhibit strong absorption bands in the 5–7 μm wavelength range, but at present there are no lasers in clinical use that can emit in this range. Therefore, the present study focused on the quantum cascade laser (QCL), which is a new type of semiconductor laser that can emit at MIR wavelengths and has recently achieved high output power. A high-power QCL with a peak wavelength of 5.7 μm was evaluated for use as a laser scalpel for ablating biological soft tissue. The interaction of the laser beam with chicken breast tissue was compared to a conventional CO 2 laser, based on surface and cross-sectional images. The QCL was found to have sufficient power to ablate soft tissue, and its coagulation, carbonization and ablation effects were similar to those for the CO 2 laser. The QCL also induced comparable photothermal effects because it acted as a pseudo-continuous wave laser due to its low peak power. A QCL can therefore be used as an effective laser scalpel, and also offers the possibility of less invasive treatment by targeting specific absorption bands in the MIR region.