Preferential ablation of calcified arterial plaque with laser-induced plasmas

Laser endarterectomy, a promising new method of reopening stenotic or occluded arteries, has been limited by difficulties in ablating calcified plaque. This study demonstrates that pulsed, visible laser radiation (482 nm, 1 μs duration, 40-80 mJ/pulse) can ablate calcified plaque at intensities (50 MW/cm²) that are readily transmit, ted down flexible (320 μm diameter) optical fibers and at fluences which are below the threshold for ablating normal artery. The ablative process is characterized by a loud snapping sound, a luminescent plume, ejection of fine debris, and an ablation efficiency as high as 10 mg/J, suggesting that removal of material occurs primarily by formation of a plasma and fracturing of the plaque, rather than by thermal vaporization. The presence of a plasma associated with ablation of calcified plaque was documented by emission spectrum measurements.