Biomedical subjects

Guillermo J Tearney

Publications and source records attributed to Guillermo J Tearney.

24 records · Page 2Linked to original sources

PubMed2002

Characterization of human atherosclerosis by optical coherence tomography.

BACKGROUND: High-resolution visualization of atherosclerotic plaque morphology may be essential for identifying coronary plaques that cause acute coronary events. Optical coherence tomography (OCT) is an intravascular imaging modality capable of providing cross-sectional images of tissue with a resolution of 10 micro m. To date, OCT imaging has not been investigated in sufficient detail to assess its accuracy for characterizing atherosclerotic plaques. The aim of this study was to establish objective OCT image criteria for atherosclerotic plaque characterization in vitro. METHODS AND RESULTS: OCT images of 357 (diseased) atherosclerotic arterial segments obtained at autopsy were correlated with histology. OCT image criteria for 3 types of plaque were formulated by analysis of a subset (n=50) of arterial segments. OCT images of fibrous plaques were characterized by homogeneous, signal-rich regions; fibrocalcific plaques by well-delineated, signal-poor regions with sharp borders; and lipid-rich plaques by signal-poor regions with diffuse borders. Independent validation of these criteria by 2 OCT readers for the remaining segments (n=307) demonstrated a sensitivity and specificity ranging from 71% to 79% and 97% to 98% for fibrous plaques, 95% to 96% and 97% for fibrocalcific plaques, and 90% to 94% and 90% to 92% for lipid-rich plaques, respectively (overall agreement, kappa=0.83 to 0.84). The interobserver and intraobserver reliabilities of OCT assessment were high (kappa values of 0.88 and 0.91, respectively). CONCLUSIONS: Objective OCT criteria are highly sensitive and specific for characterizing different types of atherosclerotic plaques. These results represent an important step in validating this new intravascular imaging modality and will provide a basis for the interpretation of intracoronary OCT images obtained from patients.

Aged↗

PubMed2002

Visualization of coronary atherosclerotic plaques in patients using optical coherence tomography: comparison with intravascular ultrasound.

OBJECTIVES: The aim of this study was to evaluate the feasibility and the ability of intravascular optical coherence tomography (OCT) to visualize the components of coronary plaques in living patients. BACKGROUND: Disruption of a vulnerable coronary plaque with subsequent thrombosis is currently recognized as the primary mechanism for acute myocardial infarction. Although such plaques are considered to have a thin fibrous cap overlying a lipid pool, imaging modalities in current clinical practice do not have sufficient resolution to identify thin (< 65 microm) fibrous caps. Optical coherence tomography is a new imaging modality capable of obtaining cross-sectional images of coronary vessels at a resolution of approximately 10 microm. METHODS: The OCT images and corresponding histology of 42 coronary plaques were compared to establish OCT criteria for different types of plaques. Atherosclerotic lesions with mild to moderate stenosis were identified on angiograms in 10 patients undergoing cardiac catheterization. Optical coherence tomography and intravascular ultrasound (IVUS) images of these sites were obtained in all patients without complication. RESULTS: Comparison between OCT and histology demonstrated that lipid-rich plaques and fibrous plaques have distinct OCT characteristics. A total of 17 IVUS and OCT image pairs obtained from patients were compared. Axial resolution measured 13 +/- 3 microm with OCT and 98 +/- 19 microm with IVUS. All fibrous plaques, macrocalcifications and echolucent regions identified by IVUS were visualized in corresponding OCT images. Intimal hyperplasia and echolucent regions, which may correspond to lipid pools, were identified more frequently by OCT than by IVUS. CONCLUSIONS: Intracoronary OCT appears to be feasible and safe. Optical coherence tomography identified most architectural features detected by IVUS and may provide additional detailed structural information.

Cardiac Catheterization↗

PubMed2002

Optical coherence tomography of the biliary tree during ERCP.

BACKGROUND: Optical coherence tomography (OCT) is a high-resolution imaging technique that produces cross-sectional images in vivo. This is a report of the first use of OCT to acquire images of the biliary tree during ERCP. METHODS: A 2.6-mm diameter OCT catheter delivered through the accessory channel of a duodenoscope was used to acquire images of the intrahepatic and extrahepatic bile ducts in 5 patients. Histology-correlated OCT images of 5 cadaveric livers, each imaged at 3 sites, were used to guide interpretation of the in vivo images. RESULTS: Biliary ductal epithelium and subepithelial structures, including peribiliary glands, vasculature, and hepatic parenchyma, were visualized in vivo. The papillary architecture of cholangiocarcinoma was identified by OCT. There were no OCT-related complications. CONCLUSIONS: High-resolution OCT imaging of the biliary tree is feasible and may provide useful diagnostic information during ERCP.

Bile Duct Diseases↗

PubMedDate not supplied

Intravascular optical coherence tomography: cellular imaging.

The vast majority of acute coronary events are attributed to rupture or erosion of high-risk or vulnerable plaques. Novel imaging techniques are being actively sought that can detect quiescent vulnerable features within coronary plaque and thereby identify populations at risk, monitor plaque progression, and target therapy appropriately. Optical coherence tomography is an intravascular imaging modality capable of detecting and characterizing coronary plaque in vivo. Recently, optical coherence tomography quantification of macrophage infiltration within atherosclerotic plaque ex vivo was demonstrated. Application of this technique to clinical practice yields a hybrid image incorporating plaque morphology with a measure of biologic activity. In a recently conducted clinical study assessing macrophage distributions in patients, evidence supporting both the vulnerable plaque model and the hypothesis of multifocal inflammatory risk, linked by the common thread of increased macrophage infiltration, has been found. These results suggest that elevated multifocal coronary macrophage content, present both in culprit lesions and at remote sites, serves as a background for heightened risk. Superimposed on this inflammatory background, local increases in macrophage content, particularly at the cap surface and at areas at high risk for rupture, further promote the instability of individual lesions.

Blood Vessels↗

PubMedDate not supplied

Measurement of fibrous cap thickness in atherosclerotic plaques by spatiotemporal analysis of laser speckle images.

Necrotic-core fibroatheromas (NCFA) with thin, mechanically weak fibrous caps overlying lipid cores comprise the majority of plaques that rupture and cause acute myocardial infarction. Laser speckle imaging (LSI) has been recently demonstrated to enable atherosclerotic plaque characterization with high accuracy. We investigate spatio-temporal analysis of LSI data, in conjunction with diffusion theory and Monte Carlo modeling of light transport, to estimate fibrous cap thickness in NCFAs. Time-varying laser speckle images of 20 NCFAs are selected for analysis. Spatio-temporal intensity fluctuations are analyzed by exponential fitting of the windowed normalized cross-correlation of sequential laser speckle patterns to obtain the speckle decorrelation time constant, tau(rho), as a function of distance rho from the source entry location. The distance, rho', at which tau(rho) dropped to 65% of its maximum value is recorded. Diffusion theory and Monte Carlo models are utilized to estimate the maximum photon penetration depth, zmax(rho'), for a distance equal to rho', measured from LSI. Measurements of zmax(rho') correlate well with histological measurements of fibrous cap thickness (R=0.78, p<0.0001), and paired t-tests show no significant difference between the groups (p=0.4). These results demonstrate that spatio-temporal LSI may allow the estimation of fibrous cap thickness in NCFAs, which is an important predictor of plaque stability.

Algorithms↗

PubMedDate not supplied

Optical coherence tomography for imaging the vulnerable plaque.

While our understanding of vulnerable coronary plaque is still at an early stage, the concept that certain types of plaques predispose patients to developing an acute myocardial infarction continues to be at the forefront of cardiology research. Intracoronary optical coherence tomography (OCT) has been developed to both identify and study these lesions due to its distinct resolution advantage over other imaging modalities. We review clinical research conducted at the Massachusetts General Hospital over the past five years to develop, validate, and utilize this technology to improve our understanding of vulnerable plaque. Our results show that intracoronary OCT may be safely conducted in patients and that it provides abundant information regarding plaque microscopic morphology, which is essential to the identification and study of high-risk lesions. Even though many basic biological, clinical, and technological challenges must be addressed prior to widespread use of this technology, the unique capabilities of OCT ensure that it will have a prominent role in shaping the future of cardiology.

Algorithms↗