Subnanosecond Probing of the Ablation of Soft Plaque from Arterial Wall by 308 nm Laser Pulses Delivered Through a Fiber

Abstract

Ablation and etching in air by pulsed, ultraviolet (308 nm) laser radiation of the surface of a sample of soft plaque attached to the arterial wall was probed by pulses of visible laser radiation (596 nm; < 1 ns FWHM). The ultraviolet radiation was delivered to the sample by an optical fiber 600 m in diameter. The results of the probing were recorded photographically. Ablation and etching in air of the intimal wall by laser pulses at the same wavelength was also probed in the same manner for comparison. When the fiber tip was 0.5 mm above the sample surface, the ablation that was caused by the laser pulse was readily seen as a blast wave of expanding gases that was followed by the ejection of solid particulates. When the fiber tip was lightly pressed down on the surface of the plaque or intimal wall, the ablation was hindered in the case of the plaque and nearly suppressed in the intimal wall. When ablation of the soft plaque did occur, it was violent in nature. These results exemplify the pressure effects that have to be taken into consideration in the clinical use of laser angioplasty. © 1990 IEEE