Basic science: The cutting edge in optical diagnostics and therapeutics of tissues and cells

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 156 KB
• Volume: 34
• Category: Article
• ISSN: 0196-8092
• DOI: 10.1002/lsm.20049

✦ Synopsis

Background and Objectives: Mechanisms of laser-tissue interaction have been a subject of interest. This study presents the effect of an artificially deposited liquid film on a biological tissue surface at near damage threshold laser fluences. Study Design/Materials and Methods: Pure water and perfluorocarbon films are respectively applied on porcine skeleton surface prior to a laser pulse with a varying liquid film thickness. Laser ablation efficiency is studied in the wavelength range between 3 and 10 mm using a wavelength-tunable Stanford amplified optical parametric amplifier (OPA). Depth and volume of the ablation crater are determined with an optical coherence tomography, and scanning electron microscope (SEM) investigations are performed on the irradiated surfaces. A piezoelectric transducer evaluates a laser-induced acoustic transient propagating into the target. Results: Since both liquids are optically denser than air, higher optical matching at the air-liquid interface enhances ablation rate. Lower boiling point of the perfluorocarbon results in explosive liquid vaporization, improving material removal rather than water. Applied liquid film decreases ablation threshold until the thickness reaches an optimal value. Conclusions: Application of a thin liquid film increases the ablation rate and lowers the damage threshold. Acoustic-transient generation reveals that the degree of ablation enhancement by the liquid layer increases nonlinearly with laser fluence. Augmentation of ablation efficiency is contingent on both applied liquid and thickness of the film.