Study of Photobleaching Effect induced by high-repetition rate UV fiber laser on Arterial Vessel Tissue: Application to the development of an intravascular optical diagnostic system

Atherosclerosis is one of the leading causes of deaths in modern society. The rupture-prone plaque can be characterized by time-resolved fluorescence spectroscopy (TRFS) based on the fluorescence decay characteristics of endogenous fluorophores of arterial wall including collagen, elastin, and lipids. However, the clinical application of TRFS has the limitations of time-consuming data acquisition and complex processing of the results. Our novel approach, simultaneous time and wavelength resolved fluorescent spectroscopy (STWRFS) enables rapid tissue diagnosis (on the order of milliseconds). Due to the fast data acquisition, we are able to translate the STWRFS technique to a near real time intravascular catheter- based system by using an ultrafast fiber laser (355 nm, 1 MHz). Since the laser with high repetition rate is used in such system, the photobleaching effect needs to be assessed for different experimental parameters, such as excitation energy, pulse repetition rate and rotational scanning speeds (30 Hz, 15 Hz, and 1 Hz) with the assumption that minimal bleaching would occur at a higher scanning speed. Emission intensity and average lifetime information obtained from 9 porcine aorta specimens will be measured at different linear scanning speeds equivalent to those rotational speeds for intravascular application at several excitation energies and pulse repetition rates. The procedure will be repeated again to statistically analyze the photobleaching effect and the fluorescence recovery. Using the results of this experiment, we hope to determine the optimal instrumental parameters for the catheter- based STWRFS system coupling with the ultrafast fiber laser.