The absorption coefficient of the arterial thrombus is 7~10 fold greater than that of arterial wall for the wave lengths of 480~510nm. This fact suggest that selective laser thrombus ablation could be possible without ablation of surrounding vessel wall in this wavelengths.

Pulsed dye laser(488nm, 2.2µs, 10Hz) thrombus ablation was investigated in viro. Ablation threshods of whole blood clot and normal aortic tissue were measured using a 1.5mm multifiber laser catheter(14×150µm). Whole blood clot samples were lasered to determine the ablation efficiency. The operative fluence was 80mJ/mm2. The transmission efficiencies of 488nm wave length through various transmission media(including contrast media of saline solution) were observed using a ύ Fr arterial sheath filled with transmission medium.

The ablation threshold for fresh whole blood clot in saline solution was 36.5±2.4mJ/mm2(9.0±0.6mJ/pulse) as compared with that for normal human aortic tissue which was over 405mJ/mm2(>100mJ/pulse)(p<0.05). Pulsed dye laser ablated whole blood clot with the efficiency at 0.026±0.009gm/J. The role of thrombus ablation was 0.154±0.056gm/min. This experiment also revealed that cotrast media(Ultravist® 370, Schering, France) allows light tramission of 488nm wave length at relatively high efficiency.

These facts suggested that selective pulsed dye laser ablation of fresh intravascular thrombi can be obtained at relatively low energy fluence without damaging the surrounding vascular tissue. A new pulse dye laser delivery system such as catheter system or native coronary artery filled with contrast media, which has large area of frontfiring face, may facilitate a safe and effective thrombus ablation.