Microsecond laser ablation of thrombus and gelatin under clear liquids: Contact versus noncontact

Laser thrombolysis is a procedure for removing blood clots in occluded arteries using pulsed laser energy. The laser light is delivered through an optical fiber to the thrombus. The ablation process is profoundly affected by whether the optical fiber tip is inside a catheter or is in contact with the thrombus. This study measured ablation efficiency of 1-/spl mu/s laser pulses to remove a porcine clot confined in a silicone tube. The cavitation process was investigated by visualizing laser-induced bubble formation on gelatin targets with flash photography and measuring the acoustic transients with a pressure transducer. The laser spot size did not affect the mass of material removed. The efficiency of the contact ablation was at least three times greater than that of the noncontact ablation. Finally, the mass removed was closely correlated with the measured bubble expansion pressure.