The efficiency of laser ablation of thrombus depends on spot size, pulse energy and repetition rate. A 1 μs pulsed dye laser (504 nm) was used to ablate a gelatin-based thrombus model containing an absorbing dye under water. The gelatin was confined in 3 mm inner diameter tubes and pulse energies of 25-100 mJ were delivered via 300, 600, and 1000 μm core diameter fibers. The experiments were conducted at pulse repetition rates of 3 Hz and 10 Hz. The amount of gelatin removed was measured using a spectrophotometric method and ablation efficiency was defined as mass removed per pulse per unit energy. Flash photography was used to visualize the ablation process in 1 cm cuvettes. Results: More material was removed using bigger fibers in the 3 mm tubes at similar pulse energies. The amount of gelatin removed per pulse increased linearly with pulse energy. There was no significant change in the amount removed at pulse repetition rates of 3 Hz and 10 Hz. In the 1 cm cuvettes, the ablation mass was roughly the same with both the 300 μm and 1000 μm fibers. Flash photography of the ablation process in 1 cm cuvettes showed that less than 1% of the laser energy went into formation of a vapor bubble. The mass removed increased roughly linearly with bubble energy. Conclusions: Ablation mass increases linearly with pulse energy, but does not have a direct relationship with radiant exposure. It is independent of the repetition rate under 10 Hz.
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