Intracoronary Raman spectroscopy could open new avenues for the study and management of coronary artery disease due to its potential to measure the chemical and molecular composition of coronary atherosclerotic lesions. We have fabricated and tested a 1.5-mm-diameter (4.5 Fr) Raman catheter capable of collecting Raman spectra in both the fingerprint (400-1800 cm(-1)) and high-wavenumber (2400-3800 cm(-1)) regions. Spectra were acquired in vivo, using a human-swine xenograft model, in which diseased human coronary arteries are grafted onto a living swine heart, replicating the disease and dynamic environment of the human circulatory system, including pulsatile flow and motion. Results show that distinct spectral differences, corresponding to the morphology and chemical composition of the artery wall, can be identified by intracoronary Raman spectroscopy in vivo.

Background—A method capable of determining atherosclerotic plaque composition and measuring plaque viscoelasticity can provide valuable insight into intrinsic features associated with plaque rupture and can enable the identification of high-risk lesions. In this article, we describe a new optical technique, laser speckle imaging (LSI), that measures an index of plaque viscoelasticity. We evaluate the potential of LSI for characterizing atherosclerotic plaque. Methods and Results—Time-varying helium-neon laser speckle images were acquired from 118 aortic plaque specimens from 14 human cadavers under static and deforming conditions (0 to 200 &mgr;m/s). Temporal fluctuations in the speckle patterns were quantified by exponential fitting of the normalized cross-correlation of sequential frames in each image series of speckle patterns to obtain the exponential decay time constant, &tgr;. The decorrelation time constants of thin-cap fibroatheromas (TCFA) (&tgr;=47.5±19.2 ms) were significantly lower than those of other atherosclerotic lesions (P<0.001), and the sensitivity and specificity of the LSI technique for identifying TCFAs were >90%. Speckle decorrelation time constants demonstrated strong correlation with histological measurements of plaque collagen (R=0.73, P<0.0001), fibrous cap thickness (R=0.87, P<0.0001), and necrotic core area (R=−0.81, P<0.0001). Under deforming conditions (10 to 200 &mgr;m/s), &tgr; correlated well with cap thickness in necrotic core fibroatheromas (P>0.05). Conclusions—The measurement of speckle decorrelation time constant from laser speckle images provides an index of plaque viscoelasticity and facilitates the characterization of plaque type. Our results demonstrate that LSI is a highly sensitive technique for characterizing plaque and identifying thin-cap fibroatheromas.

A. F. W. van der Steen—(8) 1034 A. Hoffman—(5) 626 A. J. Slifka—(8) 1042 A. Mol—(12) 1762 A. Pedotti—(3) 402 Abboud Shimon—(5) 616 Abdul I. Barakat—(4) 444 Abe Deanda—(12) 1736 Abidin Kayserilioglu—(11) 1607 Ahmad S. Khalil—(11) 1631 Aisha Shaheen—(7) 963 Ajit P. Yoganathan—(4) 429 Ajit P. Yoganathan—(12) 1815 Ajit P. Yoganathan—(3) 284 Ajit P. Yoganathan—(5) 557 Ajit P. Yoganathan—(9) 1158 Alan B. Lumsden—(6) 772 Alan D. Freed—(12) 1803 Alan W. Eberhardt—(2) 248 Alan W. L. Chiu—(6) 798 Alejandro J. Almarza—(7) 943 Aleksander S. Popel—(8) 991 Alexander A. Spector—(8) 991 Alexandra H. Chau—(11) 1631 Alfonso Palma—(11) 1595 Alfonso Palma—(5) 642 Ali El Kateeb—(6) 841 Alok Tewari—(8) 1071 Ana M. Barbero—(9) 1281 Andrea Mix—(9) 1167 Andreas Anayiotos—(7) 929 Andreas Voss—(5) 656 Andreas Voss—(9) 1167 Andrew D. McCulloch—(7) 888 Andrew Pullan—(5) 590 Andrew Yee—(11) 1546 Andrzej Krol—(9) 1175 András Czirók—(6) 854 Aneta Stefanovska—(11) 1574 Anna M. Wu—(11) 1640 Anne Humeau—(11) 1574 Antonios G. Mikos—(1) 63 Antonios G. Mikos—(9) 1238 Atsushi Shirai—(4) 415

High-resolution imaging provides a significant means for accurate material modulus estimation and mechanical characterization. Within the realm of in vivo soft tissue characterization, particularly on small biological length scales such as arterial atherosclerotic plaques, optical coherence tomography (OCT) offers a desirable imaging modality with higher spatial resolution and contrast of tissue as compared with intravascular ultrasound (IVUS). Based on recent advances in OCT imaging and elastography, we present a fully integrated system for tissue elasticity reconstruction, and assess the benefits of OCT on the distribution results of four representative tissue block models. We demonstrate accuracy, with displacement residuals on the order of 10−6 mm (more than 3 orders of magnitude less than average calculated displacements), and high-resolution estimates, with the ability to resolve inclusions of 0.15 mm diameter.

Finite element analysis is a powerful tool for investigating the biomechanics of atherosclerosis and has thereby provided an improved understanding of acute myocardial infarction. Structural analysis of arterial walls is traditionally performed using geometry contours derived from histology. In this paper we demonstrate the first use of a new imaging technique, optical coherence tomography (OCT), as a basis for finite element analysis. There are two primary benefits of OCT relative to histology: 1) imaging is performed without excessive tissue handling, providing a more realistic geometry than histology and avoiding structural artifacts common to histologic processing, and 2) OCT imaging can be performed in vivo, making it possible to study disease progression and the effect of therapeutic treatments in animal models and living patients. Patterns of mechanical stress and strain distributions computed from finite element analysis based on OCT were compared with those from modeling based on “gold standard” histology. Our results indicate that vascular structure and composition determined by OCT provides an adequate basis for investigating the biomechanical factors relevant to atherosclerosis and acute myocardial infarction.

A variational approach to tissue velocimetry in optical coherence elastography (OCE) is presented. It exploits prior information about vessel wall velocities to reduce the sensitivity of conventional tracking methods to speckle decorrelation and noise.

A. Artmann-Temiz—(9) 1243 A. G. Isasi—(7) 932 A. J. Reid—(10) 1355 A. Nagaraj—(2) 257 A. Wahle—(12) 1628 Abbas F. Jawad—(7) 924 Abhinav Chhabra—(1) 18 Adam C. Aufder Heide—(8) 1161 Adel Alhadlaq—(7) 911 Adler Salazar—(2) 189 Adriana L. Vega—(12) 1710 Agah Uguz—(5) 773 Ajit P. Yoganathan—(11) 1461 Ajit P. Yoganathan—(8) 1050 Ajit P.—(12) 1607 Ajit. P. Yoganathan—(4) 555 Alan W. L. Chiu—(5) 732 Alejandro J. Almarza—(1) 2 Aleksander S. Popel—(5) 645 Alex Koulakov—(9) 1265 Alexander C. Wright—(1) (70) Alexandra H. Chau—(11) 1494 Aliakbar Afshari—(5) 756 Allan S. Jones—(6) 880 Allen Klinger—(9) 1317 Allison Hubel—(2) 274 Amanda W. Law—(3) 360 Andrew D. McCulloch—(12) 1599 Andrew Hamilton—(4) 544 Andrew J. L. Walsh—(3) 430 Anna R. Derubeis—(1) (160) Anne Mundermann—(3) 447 Anthony Escarcega—(2) 306 Anubhav Garg—(4) 563 Arin Lynn Isenstein —(1) 18 Arnold I. Caplan—(7) 911 Ashwin Nagaraj—(4) 544 Asit K. Saha—(6) 871 Aurelio Cappozzo—(5) 764 Aurora Lopez—(7) 911

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text A. Chau, R. Chan, M. Kaazempur-Mofrad, N. Iftimia, M. Shishkov, G. Tearney, and B. Bouma, "Vascular Optical Coherence Elastography: Assessment of Conventional Velocimetry Applied to OCT," in Biomedical Topical Meeting, OSA Technical Digest (Optica Publishing Group, 2004), paper FH47. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article