Excimer laser-induced simultaneous ablation and spectral identification of normal and atherosclerotic arterial tissue layers.

Abstract

A krypton-fluorine excimer laser at a 248-nm wavelength was used to irradiate normal and severely atherosclerotic segments of human postnortem femoral arteries. Single pulses and multiple pulses required for penetration or perforation of the arterial wall were applied with 16 nsec pulse width and 5 J/cm2/pulse energy fluence. The total fluorescence of irradiated and ablated tissue was analyzed in real-time mode by means of spectroscopy. Each laser pulse produced one spectrum that was characteristic of the composition of the tissue layer, which was ablated. Fluorescence spectroscopy indicated a broad-continuum emission between 300 and 700 nm with peak fluorescence of equal intensity at wavelengths of 370 and 460 nm (ratio, 1.004 + 0.087) for normal media layers. Atheromas without calcification (lipid, fibrous, and mixed) were found with spectral maxima at the same wavelengths but with significantly reduced intensity at 460 nm (ratio, 1.765+± 0.263; p<0.001). In contrast to this broad-continuum fluorescence, calcified plaques displayed multiple-line emission with the most prominent peaks at wavelengths of 397, 442, 450, 461, 528, and 558 nm. These fluorescence criteria identified the histologically classified target tissue precisely. Histological examination of the corresponding arterial layers indicated sharply delineated and circumscribed tissue ablation. These results indicate that simultaneous tissue identification (diagnosis) and ablation (treatment) by excimer laser irradiation is feasible under strict laboratory conditions. We conclude that this principle demonstrates the potential for laser beam control by means of target-specific ablation. (Circulation 1988;78:1031-

Single-laser approach for fluorescence guidance of excimer laser angioplasty at 308 nm: Evaluation in vitro and during coronary angioplasty

“…Arterial media, fibrous plaques and atheromas showed each fluorescence spectra with typical line shapes. These spectra did not change between saline and blood and resembled noncorrected spectra obtained in air [15,16,23]. Calcified lesions, however, yielded markedly different fluorescence spectra in saline and blood.…”

“…The different physical properties of these fluids may result in different photoproducts upon ablation and different absorption of fluorescence emission in the case of calcified lesions. The broad-banded spectra of calcified material in sa- line and blood also differed significantly from the corresponding spectrum in air dominated by calcium I and II lines [15,16,23,26]. This transition can be attributed to plasma formation in air which is not present in a fluid environment [23,26].…”

“…Laufer et al applied KrFl excimer laser emission at 248 nm focused with a lens [15] and XeCl laser pulses at 308 nm above and below the ablation threshold through a 1,000 m monofiber [16] to postmortem femoral artery segments. They demonstrated that arterial media, lipid plaques, and calcified lesions show characteristic fluorescence spectra following excimer laser excitation [15,16].…”

“…They demonstrated that arterial media, lipid plaques, and calcified lesions show characteristic fluorescence spectra following excimer laser excitation [15,16]. However, all these experiments were performed in room air.…”

“…Arterial fluorescence following excimer laser excitation has been studied in an air environment [15,16]. In the present study, a spectroscopy system was developed and coupled to a clinically approved XeCl excimer laser.…”