Background and Objective:
Previous studies have demonstrated that during Xenon-Chloride excimer laser ablation of tissue, r a p idly expanding and imploding bubbles (diameter < 3 mm), predominantly containing water vapor, are formed. These short lived bubbles (life time < 300 ps) induce mechanical damage in adjacent tissue. In the present study, a theoretical analysis of the volume of vaporized water is correlated with measured bubble volumes formed in hemoglobin solution.
Study DesignIMateriaZs and Methods: The dimensions of the rapidly expanding and imploding vapor bubble induced by the XeCl excimer laser pulses (308 nm, 115 ns), delivered via a 300,550, or 950 pm diameter monofiber in 16% w/v hemoglobin solution (at 37"C), were measured. Results: Theoretical analysis and the experimental data correlated well (correlation coefficient r = 0.97). The diameter of excimer laser induced bubbles increased with increasing pulse energy. For a given radiant exposure, the bubble size was decreased by either decreasing the fiber tip area or by decreasing the absorption coefficient of the hemoglobin solution. Conclzcswn: We conclude that, for a wide range of conditions, theory agrees well with experimental data. Thus, during delivery of excimer laser pulses in blood, bubble dimensions can be reduced by flushing with saline or by reduction of the area radiated with each laser pulse, for example, by pulse multiplexing or using a smaller multifiber catheter.