Laser Bioeffects Resulting from Non-Linear Interactions of Ultrashort Pulses with Biological Systems

摘要

The original goal of this project was to determine the role of non- linear interactions underlying the bioeffects induced by ultrashort pulse laser pulses. As initially conceived, this line of investigation was to be principally directed at understanding the contribution of multiphoton absorption. This indeed was a major focus of the research project, but for various reasons the scope of the work was expanded to include identification of the intracellular mechanisms that determine the cellular response to the absorption of optical radiation, and to develop and implement a non-invasive means for measuring the thermal gradients induced by the absorption of laser radiation in tissue. Both of these ancillary projects were successful in that (1) the transcription factor NF-B was found to be activated by visible laser exposure in a way that appeared to be dependent on the absorption of laser energy in the melanin granules of the retinal pigment epithelial cell, and (2) by exploiting the temperature-dependent nature of the proton resonance frequency (PRF), magnetic resonance thermography was successfully used to measure temperature gradients induced in tissue phantoms during laser exposure, and these gradients closely followed the spatial distributions predicted by classical heat diffusion theory.