A. Vogel et al., MINIMIZATION OF CAVITATION EFFECTS IN PULSED-LASER ABLATION ILLUSTRATED ON LASER ANGIOPLASTY, Applied physics. B, Lasers and optics, 62(2), 1996, pp. 173-182
Cavitation effects in pulsed laser ablation can cause severe deformati
on of tissue near the ablation site. In angioplasty, they result in a
harmful dilatation and invagination of the vessel walls. We suggest to
reduce cavitation effects by dividing the laser pulse energy into a p
re-pulse with low and an ablation pulse with high energy. The pre-puls
e creates a small cavitation bubble which can be filled by the ablatio
n products of the main pulse. For suitable energy ratios between the p
ulses, this bubble will not be enlarged by the ablation products, and
the maximal bubble size remains much smaller than after a single ablat
ion pulse. The concept was analyzed by numerical calculations based on
the Gilmore model. of cavitation dynamics and by high-speed photograp
hy of the effects of single and double pulses performed with a silicon
e tube as vessel model. The use of double pulses prevents the deformat
ion of the vessel walls. The concept works with an energy ratio of up
to about 1.30 between the pulses. For the calculated optimal ratio of
1:14.6, the bubble volume is reduced by a factor of 17.7. The ablation
pulse is best applied when the pre-pulse bubble is maximally expanded
, but the timing is not very critical.