MICROPULSE, Q-SWITCHED 2-MICRON LASER FOR ANGIOPLASTY

A COMMERCIAL MODEL OF A PULSED, 2-MICRON-WAVELENGTH, SOLID-STATE LASER WILL BE MODIFIED AND TESTED FOR EFFICIENT Q-SWITCHED PERFORMANCE BY FORCING EMISSION OF A TRAIN OF Q-SWITCHED MICROPULSES. AT LEAST TWO DIFFERENT TYPES OF LASER CRYSTALS-TM:CR:YAG AND HO:TM:CR:YAG-WILL BE USED TO INVESTIGATE THE DIFFERENCES IN PULSE PARAMETERS FOR THE TWO- AND THREE-STEP ENERGY TRANSFER MECHANISMS RESPONSIBLE FOR LASER ACTION IN THESE CRYSTALS. CONTROL OVER PULSE-TO-PULSE SEPARATION AND, THEREFORE, OVER THE ENERGY PER MICROPULSE WILL BE ACCOMPLISHED BY VARYING THE RADIO-FREQUENCY PULSES CONTROLLING THE Q-SWITCH. HIGHLY EFFICIENT OPERATION IS ENVISIONED DUE TO THE ABILITY TO EXTRACT ENERGY DURING ALL OF THE PUMPING CYCLE. FUSED-SILICA FIBERS WILL BE USED TO DELIVER LASER RADIATION TO TISSUE FOR A STUDY OF LASER-TISSUE INTERACTIONS. SPECIAL ATTENTION WILL BE GIVEN TO ABLATION OF CALCIFIED ANDFIBROTIC PLAQUES. THE AMOUNT OF ACOUSTICAL DAMAGE TO NEIGHBORING TISSUE, PRODUCED AT FLUENCES NECESSARY TO REMOVECALCIFICATIONS, WILL BE STUDIED AS A FUNCTION OF LASER WAVELENGTH, TOTAL PULSE ENERGY, AND MICROPULSE PARAMETERS. THE STARTING LASER PARAMETERS WILL BE PRESELECTED FOR THE TISSUE STUDIES BY ANALYZING ACOUSTICAL SIGNALS IN AGAR GEL AT VARIOUS DISTANCES FROM THE POINT OF INCIDENCE.