Soft tissue cutting efficiency by 980 nm laser with carbon-, erbium-, and titanium-doped optothermal fiber converters.

Abstract

The use of near-IR diode lasers for contact soft tissue surgery is attended by a risk of severe thermal damage of surrounding tissues due to the low cutting efficiency of these lasers. To increase the cutting efficiency of a near-IR lasers in contact surgery special tips (converters) which transform laser light to heat are used. The present in vivo study evaluated temperature dynamics and soft tissue cutting efficiency of 980 nm diode laser equipped with standard carbon- and novel erbium- and titanium-doped converters. For in vitro treatment on soft tissue (chicken thigh), 980 nm diode laser was used. The radiation was delivered to the tissue by a quartz fiber with a core diameter of 400 ± 5 µm. The carbon-, erbium-, or titanium-doped converters were mounted at the fiber distal end. The converters temperature was measured by IR-sensor integrated into the laser radiation delivery system. The temperature dynamics of each converter during soft tissue treatment was evaluated. The converter was in contact with the soft tissue surface and moved across the surface of soft tissue with a speed of 1, 3, or 6 mm/s. The average power of laser radiation was 0.3, 1.0, or 4.0 W. The collateral thermal damage of treated soft tissues was evaluated using NTBC stain. The width and depth of coagulation and ablation zones of laser wounds was determined. The soft tissue cutting efficiency with different converters was calculated. The cutting efficiency, collateral damage, and converter temperature in contact with soft tissue change depending on the type of converter, the power of laser radiation and the converter movement speed along the tissue surface. Maximal converter temperature (1,980 ± 154 °C), at which a tissue cut takes place, was fixed for Ti-doped converter for laser power of 4.0 W and movement speed of 1 mm/s. Minimal converter temperature (540 ± 30 °C), at which a tissue cut takes place, was fixed for Ti-doped converter for laser power of 1.0 W and movement speed of 6 mm/s. Maximal depth of coagulation (0.72 ± 0.10 mm) was fixed for Ti-doped converter for laser power of 4.0 W and movement speed of 1 mm/s. Minimal depth of coagulation (0.11 ± 0.02 mm) was fixed for C-doped converter for laser power of 0.3 W and movement speed of 3 mm/s. Maximal cutting efficiency (0.57 mm3 /W) was fixed for Er-doped converter for laser power of 1.0 W and movement speed of 1 mm/s. Minimal cutting efficiency (0.02 mm3 /W) was fixed for C-doped converter for laser power of 4.0 W and movement speed of 6 mm/s. All three studied types of converters can be used for contact surgery of soft tissues by 980 nm diode laser. Er-doped and Ti-doped converters are more resistant to laser heating then C-doped converter, they dissect soft tissue more effectively. This will also expand the potential of everyday routine clinical procedures, making them safer, faster, and easier. These converters can be used in general surgery, plastic surgery, dermatology, angioplasty, dentistry, neurosurgery, etc. Lasers Surg. Med. 51:185-200, 2019. © 2018 Wiley Periodicals, Inc.