Detection of rupture-prone atherosclerotic plaques by time-resolved laser-induced fluorescence spectroscopy

Abstract

Objective-Plaque with dense inflammatory cells, including macrophages, thin fibrous cap and superficial necrotic/lipid core is thought to be prone-to-rupture. We report a time-resolved laserinduced fluorescence spectroscopy (TR-LIFS) technique for detection of such markers of plaque vulnerability in human plaques.Methods-The autofluorescence of carotid plaques (65 endarterectomy patients) induced by a pulsed laser (337 nm, 0.7 ns) was measured from 831 distinct areas. The emission was resolved spectrally-(360-550 nm range) and temporally-(0.3 ns resolution) using a prototype fiber-optic TR-LIFS apparatus. Lesions were evaluated microscopically and quantified as to the % of different components (fibrous cap, necrotic core, inflammatory cells, foam cells, mature and degraded collagen, elastic fibers, calcification, and smooth muscle cell of the vessel wall).Results-We determined that the spectral intensities and time-dependent parameters at discrete emission wavelengths 1) allow for discrimination (sensitivity >81%, specificity >94%) of various compositional and pathological features associated with plaque vulnerability including infiltration of macrophages into intima and necrotic/lipid core under a thin fibrous cap, and 2) show a linear correlation with plaque biochemical content: elastin (P<0.008), collagen (P<0.02), inflammatory cells (P<0.003), necrosis (P<0.004).Conclusion-Our results demonstrate the feasibility of TR-LIFS as a method for the identification of markers of plaque vulnerability. Current findings enable future development of TR-LIFS based clinical devices for rapid investigation of atherosclerotic plaques and detection of those at high-risk.

Fluorescence lifetime imaging for the characterization of the biochemical composition of atherosclerotic plaques

“…The LEC values reported here are in agreement with earlier reported time-resolved fluorescence spectroscopy measurements that have also reported Laguerre coefficient values from atherosclerotic plaque including lipid-rich specimens. 14,32 Ratios of FLIM-derived parameters are robust for assessing plaque composition because they describe in one variable the variation in fluorescence decay dynamics at both F377 and F460. Most obviously, CR samples have the highest τ R because of long τ F377 values.…”

“…1 and was further detailed in an earlier publication. 19 Based on previous TRFS results from human atherosclerotic plaque, 14 two filters were used: F377: 377/50 nm Journal of Biomedical Optics September 2011 r Vol. 16(9) 096018-2 and F460: 460/60 nm (center wavelength/bandwidth) that together provide discrimination between intrinsic fluorophores related to plaque vulnerability.…”

“…Moreover, the use of time-resolved fluorescence spectroscopy (TRFS), a technique designed to measure the fluorescence intensity decay dynamics (excited state lifetimes), was recently found to be capable of identifying markers of plaque vulnerability (inflammatory cell infiltration and collagen degradation in the fibrotic cap, presence of a necrotic core under a thin fibrotic cap) in both human carotid and aortic ex vivo plaque samples. 13,14 However, to date, TRFS has been limited to a large extent to providing single point measurements and is therefore lacking the imaging capability necessary for an extensive (surface) assessment of biochemical features of the arterial wall. A fluorescence lifetime imaging microscopy (FLIM) technique can address this limitation.…”

Nonlinear optical microscopy in decoding arterial diseases

“…Intravascular ultrasound (IVUS) and more recently optical coherence tomography are imaging technologies that are available to clinicians to visualize plaque structure in the vessel wall (Hodgson et al 1993;Yock and Fitzgerald 1998;Jang et al 2005;Barlis et al 2008a, b;Sun et al 2008;Barlis and Schmitt 2009). Recent studies have shown the potential of fluorescence lifetime imaging to differentiate thin plaques from thick plaques and thick-cap fibroatheroma based on UV-excited fluorescence lifetime data (Suhling et al 2005;Jo et al 2006;Marcu et al 2009;Phipps et al 2009;Thomas et al 2010). However, none of these methods are able to resolve the composition of individual plaques nor can they detect early compositional changes within atherosclerotic intima.…”

Caracterização de lipoproteína de baixa densidade (LDL) por meios espectroscópicos

“…A aterosclerose é uma doença progressiva, e o estudo com experimentos com modelo animal, principalmente com coelhos, tem contribuído para o entendimento da progressão da doença [41], [42].…”