Characterization of Atherosclerotic Plaques by Laser Speckle Imaging

Evaluation of collagen in atherosclerotic plaques: the use of two coherent laser-based imaging methods

“…Since scatterer motion causes a modulation of the laser speckle pattern, the measurement of temporal intensity variations provides information about the intrinsic viscoelastic properties of the plaque, which can be used to determine plaque morphology and collagen content. Using these principles, an ex vivo study has recently been conducted to demonstrate that the measurement of the decorrelation time constant of intensity modulations of time-varying laser speckle patterns provides a highly sensitive and specific method for the characterization of atherosclerotic plaques and the measurement of collagen content [43]. Sensitivity and specificity of 100% and 93%, respectively, were reported for the detection of unstable atherosclerotic plaques by LSI.…”

“…Thirdly, vessel wall pulsation and catheter motion during the cardiac cycle may influence the modulation of laser speckle patterns. It has been shown that LSI retains high sensitivity and specificity in detecting unstable plaques, even under high rates of arterial stretch [43], potentially providing high diagnostic efficacy during vessel pulsation. In addition, the relatively short acquisition time (~40 ms) required for LSI would give, during the resting phase of the cardiac cycle (minimal catheter motion), a temporal window sufficient for one to obtain diagnostic quality speckle data for reliable measurements in vivo.…”

Correction of optical absorption and scattering variations in laser speckle rheology measurements

“…Laser Speckle Rheology (LSR), an optical approach for the non-contact evaluation of the viscoelastic properties of the materials, has a number of industrial, chemical and biomedical applications related to material sciences, polymer engineering, food sciences, and clinical diagnosis [1][2][3][4][5][6][7][8][9][10][11]. The customary tool for measuring the viscoelastic properties is a mechanical rheometer, which evaluates the ratio of an applied oscillatory stress to the consequential strain in the specimen, over a limited oscillation frequency range to calculate the frequency-dependent viscoelastic modulus, G*(ω).…”

“…The customary tool for measuring the viscoelastic properties is a mechanical rheometer, which evaluates the ratio of an applied oscillatory stress to the consequential strain in the specimen, over a limited oscillation frequency range to calculate the frequency-dependent viscoelastic modulus, G*(ω). The capability of LSR for measuring this quantity in a non-destructive/non-contact manner from the speckle fluctuations is appealing, particularly in applications where mechanical manipulation may alter the sample properties and in cases where only small sample volumes are available for measurement [1][2][3][4][5][6][7][8][9][10][11]. In LSR, a small volume of the sample is illuminated by a mono-chromatic laser source and a high-speed CMOS camera is used to capture the temporal fluctuations of back-scattered speckle patterns, induced by Brownian displacements of scattering particles [1,[6][7][8][9][10][11][12][13].…”

“…The capability of LSR for measuring this quantity in a non-destructive/non-contact manner from the speckle fluctuations is appealing, particularly in applications where mechanical manipulation may alter the sample properties and in cases where only small sample volumes are available for measurement [1][2][3][4][5][6][7][8][9][10][11]. In LSR, a small volume of the sample is illuminated by a mono-chromatic laser source and a high-speed CMOS camera is used to capture the temporal fluctuations of back-scattered speckle patterns, induced by Brownian displacements of scattering particles [1,[6][7][8][9][10][11][12][13]. Cross correlation analysis of time-varying speckle image series yields the speckle intensity temporal autocorrelation curve, g 2 (t), from which the mean square displacement (MSD) of scattering particles, <Δr 2 (t)>, is retrieved [1,10,11,[14][15][16][17][18].…”