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Thesis (M.S.)--School of Dentistry. University of Missouri--Kansas City, 2006. / "A thesis in oral biology." Advisor: Simon R. MacNeill. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed Nov. 12, 2007. Includes bibliographical references (leaves 56-60). Online version of the print edition.

A new laser ablation mechanism of liquid water based on recent insights into its hydrogen bond dynamics has been studied and several applications of the ablation demonstrated. The mechanism, termed as Impulsive Heat Deposition through Vibrational Excitations (IHDVE), is based on the ability of the hydrogen bond network of water to rapidly thermalize vibrational O-H stretch excitations on a time scale of several picoseconds even for excitation intensities that are large enough to bring excited volumes far into the supercritical region. In this way, by using vibrationally resonant picosecond infrared laser pulses with sufficient energy, it is possible to drive ultrafast phase transitions in the excited water volume leading to a rapid and efficient ablation process of water and water rich targets with minimum perturbation of solute molecules of interest. The physics behind the IHDVE ablation process is outlined and the benefits of the IHDVE ablation are demonstrated for two important applications of tissue cutting and mass spectrometry of biomolecules. Finally, the development of two high power infrared laser systems suitable for the practical implementation of IHDVE is presented.

A new laser ablation mechanism of liquid water based on recent insights into its hydrogen bond dynamics has been studied and several applications of the ablation demonstrated. The mechanism, termed as Impulsive Heat Deposition through Vibrational Excitations (IHDVE), is based on the ability of the hydrogen bond network of water to rapidly thermalize vibrational O-H stretch excitations on a time scale of several picoseconds even for excitation intensities that are large enough to bring excited volumes far into the supercritical region. In this way, by using vibrationally resonant picosecond infrared laser pulses with sufficient energy, it is possible to drive ultrafast phase transitions in the excited water volume leading to a rapid and efficient ablation process of water and water rich targets with minimum perturbation of solute molecules of interest. The physics behind the IHDVE ablation process is outlined and the benefits of the IHDVE ablation are demonstrated for two important applications of tissue cutting and mass spectrometry of biomolecules. Finally, the development of two high power infrared laser systems suitable for the practical implementation of IHDVE is presented.

Femtosecond laser microsurgery has emerged as a remarkable technique for precise ablation of biological systems with minimal damage to their surrounding tissues. The combination of this technique with nonlinear optical imaging provides a means of microscopic visualization to guide such surgery in situ. A clinical endoscope capable of image-guided femtosecond laser microsurgery will provide physicians a means for cellular-level microsurgery with the highest precision. This dissertation focuses the development of a miniaturized fiber-coupled probe for image-guided microsurgery, towards future realization as a clinical endoscope. The first part of the dissertation describes the development of an 18-mm diameter probe. This development includes delivery of femtosecond laser pulses with pulse energy in excess of 1 µJ through air-core photonic bandgap fiber, laser beam scanning by a microelectromechanical system scanning mirror, and development of a new image reconstruction methodology for extracting increased temporal information during Lissajous beam scanning. During testing, the 18-mm probe compares favorably with the state-of-the-art as a microscopic imaging tool and we present the first known demonstration of cellular femtosecond laser microsurgery through an optical fiber. The second part of the dissertation explores further refinement of the design into a streamlined package with 9.6 mm diameter and improved imaging resolution. Study of the optical performance through analytical and computer-aided optical design indicates that simple custom lenses can be designed that require only commercial-grade manufacturing tolerances while still producing a fully aberration-corrected microsurgical endoscope. With the 9.6-mm probe, we demonstrate nonlinear optical imaging, including tissue imaging of intrinsic signals from collagen, using average laser powers 2-3× lower than the current state-of-the-art. We also demonstrate the use of the 9.6-mm probe in conjunction with gold nanoparticles for enhanced imaging and microsurgery through plasmonics. Finally, in the third part of this dissertation, we detail bench-top development of a new clinical application for combined femtosecond laser microsurgery and nonlinear optical imaging: the treatment of scarred vocal folds. We show the utility of femtosecond laser microsurgery for creating sub-epithelial voids in vocal fold tissue that can be useful for enhancing localization of injectable biomaterial treatments. We demonstrate that a single compact fiber laser system can be utilized for both microsurgery and imaging. Furthermore, the proposed clinical technique is shown to be achievable with parameters (e.g., pulse energy, focused spot size) that were found to be attainable with fiber-coupled probes while still achieving ablation speeds practical for clinical use. / text

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published_or_final_version / Medical Sciences / Master / Master of Medical Sciences