Search

Background: Autofluorescence lifetime (AFL) imaging, a robust technique that enables label-free molecular investigation of biological tissues, is being introduced into the field of cardiovascular diagnostics. However, detailed AFL characteristics of coronary arteries remain elusive and there is a lack of methodology enabling such characterization. Methods: We developed multispectral fluorescence lifetime imaging microscopy (FLIM) based on analog-mean-delay. Freshly sectioned coronary arteries and atheromas, harvested from 5 swine models, were imaged using FLIM and stained to label lipids, macrophages, collagen, and smooth muscle cells. The components were quantitated from digitized histological images and compared with the corresponding FLIM. Multispectral AFL parameters derived from 2 different spectral bands (390 nm and 450 nm) were analyzed. Results: FLIM provided a wide field-of-view, high-resolution AFL imaging of frozen sections. Principal compositions of coronary arteries, such as tunica media, tunica adventitia, elastic laminas, smooth muscle cell–enriched fibrous plaque, lipid-rich core, and foamy macrophages, were well visualized in FLIM images and were found to have each different AFL spectra. In particular, proatherogenic components including lipids and foamy macrophages exhibited significantly different AFL values compared with plaque-stabilizing collagen- or smooth muscle cell–enriched tissues ( P 0.87). Conclusions: FLIM provided detailed pixel-level AFL investigation of the complex composition of coronary artery and atheroma. Our FLIM strategy enabling an automated, comprehensive visualization of multiple plaque components from unlabeled sections will be highly useful to efficiently evaluate ex vivo samples without the need for histological staining and analysis.

Rationale: Inflammation plays a pivotal role in the pathogenesis of the acute coronary syndrome. Detecting plaques with high inflammatory activity and specifically treating those lesions can be crucial to prevent life-threatening cardiovascular events. Methods: Here, we developed a macrophage mannose receptor (MMR)-targeted theranostic nanodrug (mannose-polyethylene glycol-glycol chitosan-deoxycholic acid-cyanine 7-lobeglitazone; MMR-Lobe-Cy) designed to identify inflammatory activity as well as to deliver peroxisome proliferator-activated gamma (PPARγ) agonist, lobeglitazone, specifically to high-risk plaques based on the high mannose receptor specificity. The MMR-Lobe-Cy was intravenously injected into balloon-injured atheromatous rabbits and serial in vivo optical coherence tomography (OCT)-near-infrared fluorescence (NIRF) structural-molecular imaging was performed. Results: One week after MMR-Lobe-Cy administration, the inflammatory NIRF signals in the plaques notably decreased compared to the baseline whereas the signals in saline controls even increased over time. In accordance with in vivo imaging findings, ex vivo NIRF signals on fluorescence reflectance imaging (FRI) and plaque inflammation by immunostainings significantly decreased compared to oral lobeglitazone group or saline controls. The anti-inflammatory effect of MMR-Lobe-Cy was mediated by inhibition of TLR4/NF-κB pathway. Furthermore, acute resolution of inflammation altered the inflamed plaque into a stable phenotype with less macrophages and collagen-rich matrix. Conclusion: Macrophage targeted PPARγ activator labeled with NIRF rapidly stabilized the inflamed plaques in coronary sized artery, which could be quantitatively assessed using intravascular OCT-NIRF imaging. This novel theranostic approach provides a promising theranostic strategy for high-risk coronary plaques.

In this study, we report the in vivo imaging of reactive oxygen species (ROS)-overproducing pro-inflammatory macrophages in atherosclerotic plaques using a fluorescent ROS nanosensor. We designed the nanosensor by chemically conjugating hyaluronic acid (HA, a targeting ligand for CD44 receptor), chlorin e6 [Ce6; a near-infrared fluorescent (NIRF) dye], and a thioketal (TK) linker (ROS-degradable linker). The self-assembled nanosensor emitted weak NIRF signals in normal physiological conditions, whereas it emitted strong NIRF signals under ROS-abundant conditions. The cytocompatible nanosensor showed higher intracellular internalization via receptor-mediated endocytosis, which enabled the visualization of intracellular ROS in pro-inflammatory macrophages. Moreover, we demonstrated that the nanosensor enabled the successful targeting and imaging of CD44- and ROS-overproducing pro-inflammatory macrophages in atherosclerotic plaques, as validated by confocal microscopy and immunohistological analyses. These data suggest that our ROS nanosensor is suitable for ROS imaging in pro-inflammatory macrophages in vitro and in vivo and will be a promising approach for imaging atherosclerotic tissues and evaluating the effects of antioxidants.

Micro-optical coherence tomography (µOCT) is a novel imaging approach enabling visualization of the microstructures of biological tissues at a cellular or sub-cellular level. However, it has been challenging to develop a miniaturized flexible endoscopic µOCT probe allowing helical luminal scanning. In this study, we built a flexible endoscopic µOCT probe with an outer diameter of 1.2 mm, which acquires three-dimensional images of the arterial microstructures via helical scanning with an axial and lateral resolutions of 1.83 µm and 3.38 µm in air, respectively. Furthermore, the depth of focus of the µOCT imaging probe was extended two-fold using a binary phase spatial filter. We demonstrated that the present endoscopic µOCT could image cellular level features of a rabbit artery with high-risk atheroma and a bioresorbable scaffold-implanted swine coronary artery. This highly-translatable endoscopic µOCT will be a useful tool for investigating coronary artery disease and stent biology.

Background Photoactivation targeting macrophages has emerged as a therapeutic strategy for atherosclerosis, but limited targetable ability of photosensitizers to the lesions hinders its applications. Moreover, the molecular mechanistic insight to its phototherapeutic effects on atheroma is still lacking. Herein, we developed a macrophage targetable near-infrared fluorescence (NIRF) emitting phototheranostic agent by conjugating dextran sulfate (DS) to chlorin e6 (Ce6) and estimated its phototherapeutic feasibility in murine atheroma. Also, the phototherapeutic mechanisms of DS-Ce6 on atherosclerosis were investigated. Results The phototheranostic agent DS-Ce6 efficiently internalized into the activated macrophages and foam cells via scavenger receptor-A (SR-A) mediated endocytosis. Customized serial optical imaging-guided photoactivation of DS-Ce6 by light illumination reduced both atheroma burden and inflammation in murine models. Immuno-fluorescence and -histochemical analyses revealed that the photoactivation of DS-Ce6 produced a prominent increase in macrophage-associated apoptotic bodies 1 week after laser irradiation and induced autophagy with Mer tyrosine-protein kinase expression as early as day 1, indicative of an enhanced efferocytosis in atheroma. Conclusion Imaging-guided DS-Ce6 photoactivation was able to in vivo detect inflammatory activity in atheroma as well as to simultaneously reduce both plaque burden and inflammation by harmonic contribution of apoptosis, autophagy, and lesional efferocytosis. These results suggest that macrophage targetable phototheranostic nanoagents will be a promising theranostic strategy for high-risk atheroma. Graphical abstract

Visual Abstract, Highlights • Fluorescence lifetime imaging (FLIm) allows label-free biochemical visualization of atheromas; however, it remains unknown whether FLIm can characterize high-risk plaque features in coronary arteries in a beating heart. Also, implementation of a novel analytic methodology is required for multispectral FLIm because it yields massive biochemical readouts. • This study first demonstrated a simultaneous structural and biochemical assessment of high-risk plaques in the beating swine coronary arteries using a fully integrated optical coherence tomography-FLIm and a 2.9-F low-profile dual-modal catheter. • Biochemical components of atherosclerotic plaques, including lipids, macrophages, lipids+macrophages, and fibrotic tissues, had unique fluorescence lifetime signatures that were clearly distinguishable using multispectral FLIm. • Machine learning framework was successfully integrated with multispectral FLIm and enabled an automated, quantitative imaging of multiple key components associated with plaque destabilization., Summary Coronary plaque destabilization involves alterations in microstructure and biochemical composition; however, no imaging approach allows such comprehensive characterization. Herein, the authors demonstrated a simultaneous microstructural and biochemical assessment of high-risk plaques in the coronary arteries in a beating heart using a fully integrated optical coherence tomography and fluorescence lifetime imaging (FLIm). It was found that plaque components such as lipids, macrophages, lipids+macrophages, and fibrotic tissues had unique fluorescence lifetime signatures that were distinguishable using multispectral FLIm. Because FLIm yielded massive biochemical readouts, the authors incorporated machine learning framework into FLIm, and ultimately, their approach enabled an automated, quantitative imaging of multiple key components relevant for plaque destabilization.

Optical microscopy has been widely used in biomedical research as it provides photophysical and photochemical information of the target in subcellular spatial resolution without requiring physical contact with the specimen. To obtain a deeper understanding of biological phenomena, several efforts have been expended to combine such optical imaging modalities into a single microscope system. However, the use of multiple light sources and detectors through separated beam paths renders previous systems extremely complicated or slow for in vivo imaging. Herein, we propose a novel high-speed multimodal optical microscope system that simultaneously visualizes five different microscopic contrasts, i.e., two-photon excitation, second-harmonic generation, backscattered light, near-infrared fluorescence, and fluorescence lifetime, using a single femtosecond pulsed laser. Our proposed system can visualize five modal images with a frame rate of 3.7 fps in real-time, thereby providing complementary optical information that enhances both structural and functional contrasts. This highly photon-efficient multimodal microscope system enables various properties of biological tissues to be assessed.

Intravascular optical coherence tomography-fluorescence lifetime imaging (OCT-FLIm) provides co-registered structural and biochemical information of atherosclerotic plaques in a label-free manner. For intuitive image interpretation of OCT-FLIm, herein, we present a machine learning classifier where key biochemical components (lipids, lipids+macrophages, macrophages, fibrotic, and normal) related to plaque destabilization are characterized based on the combination of multispectral FLIm parameters and convolutional OCT features. Using dataset from in vivo atheromatous swine models, the classification accuracy was >92% for each plaque component according the five-fold cross validation. This highly translatable imaging strategy will open a new avenue for clinical intracoronary assessment of high-risk plaques.

Photoactivation is a promising theranostic tool to image and stabilize the atherosclerotic plaque by apoptosis induction in macrophages or other vascular cells; however, lack of effective drugs and mechanistic understanding hinder its clinical application for cardiovascular disease. Here, we developed the macrophage targeted photosensitizer delivery strategy and demonstrated that imaging assisted light activation reduced inflammation and burden of atherosclerotic plaques. Mechanistically, targeted photoactivation induced autophagy and increased MerTK expression in carotid atheroma as early as 1 day, and had 2-fold increase in macrophage-associated apoptotic cells, indicating efferocytosis enhancement. This multifunctional photoactivatable theranostic strategy could confer a promising tool for high-risk plaques.

Introduction: Stress-associated neurobiological activity is associated with future cardiovascular events. However, whether the linkage between brain emotional activity and complex plaque characteristics exists during the phase of acute plaque instability needs to be elucidated. Objectives: We aimed to prospectively estimate brain amygdalar activity (AmygA), arterial inflammation (AI) and macrophage hematopoiesis (HEMA) according to the presence of complex plaque characteristics in patients with acute myocardial infarction (AMI). Methods: In a total of 45 AMI patients (mean 60.0 years, 84.4% male), 18F FDG-PET/CT imaging was performed within 45 days of index episode. Total plaque burden was assessed using the SYNTAX score. The culprit plaque was considered complex, if there were two or more of the following morphologic features: thrombus, ulceration, plaque irregularity, and impaired flow (TIMI Results: Average SYNTAX score ranged by 16.3±8.4 and 12 (26.7%) patients had intermediate to high score (≥22). Complex culprit plaque and significant flow limitation were present in 34 (75.6%) and 33 (73.3%) patients, respectively. AmygA increased significantly in those who had higher SYNTAX score (≥22; target-to-background ratio [TBR]: 0.68±0.08 vs. 0.63±0.06; p=0.004), complex culprit plaques (TBR: 0.66±0.05 vs. 0.60±0.04; p Conclusions: AmygA was markedly enhanced in AMI patients with complex plaque characteristics. These findings suggest that AmygA closely associates with loco-regional disease activity at the level of coronary vasculature.

Introduction: Autophagy plays a protective role in atherosclerosis and can promote efferocytosis of apoptotic cells. Photoactivation is a promising tool for treating cardiovascular disease, and induces autophagy in macrophages-derived foam cells, however, regulation of autophagy and efferocytosis by photoactivation in atherosclerotic plaque remains unknown. Objective: The present study aims to investigate whether macrophage targeted light activation induces autophagy and enhances efferocytosis in inflamed plaques Methods and Results: Targeted photoactivatable agent showed specific binding affinity and phototoxicity to scavenger receptor-expressing macrophages. Confocal microscopy analysis over time after irradiation demonstrated the induction of apoptosis and autophagy flux in macrophage-derived foam cells. The theranostic agent localized to macrophage scavenger receptors within atherosclerotic plaques, and intravital fluorescence microscopy imaged plaque inflammation and was used to monitor photobleaching after irradiation. Serial in vivo imaging analysis demonstrated that macrophage-specific photoactivation reduced plaque burden and inflammation after 1 week (Figure A). Mechanistically, targeted light activation induced autophagy within atheroma as early as 1 day (Figure B), and increased phagocytic receptor Mer tyrosine kinase (MerTK) expression. Targeted photoactivation had 2-fold-increase in macrophage-associated apoptotic bodies at one week after laser irradiation, indicating enhanced efferocytosis (Figure C). Conclusions: As a sensitive multifunctional therapeutic and imaging strategy, macrophage targeted photoactivation with autophagy induction could confer a promising theranostic strategy for the high-risk plaques.

Background/Objectives: Vascular spotty calcification is an actively regulated biological process resulting in plaque vulnerability. We investigated the feasibility of a novel alendronate-based near-infrared fluorescence (NIRF)-emitting probe to specifically target atherosclerotic calcification in a murine model in vivo using our customized high-resolution multichannel intravital molecular imaging system (IVFM). Methods/Results: We have fabricated a calcium-binding NIRF probe by chemically coupling alendronate, a specific targeting ligand, and NIRF-emitting Cy5.5 to the ends of azide-PEG-NHS ester (Al-Cy5.5). Prepared Al-Cy5.5 has high affinity for calcium phosphate-containing bone minerals. In vitro, Al-Cy5.5 specifically binds to RANKL-induced osteogenic-macrophages as compared to macrophages (p Conclusions: Our novel calcification targeted probe, Al-Cy5.5, was able to selectively target atheroma calcification in vivo in a murine model as assessed by optical IVFM. This novel targetable strategy is expected to provide a promising theranostic basis for calcified high-risk plaques by integration with multimodal customized catheter imaging system.

Rationale: Atherosclerotic plaque is a chronic inflammatory disorder involving lipid accumulation within arterial walls. In particular, macrophages mediate plaque progression and rupture. While PPARγ agonist is known to have favorable pleiotropic effects on atherogenesis, its clinical application has been very limited due to undesirable systemic effects. We hypothesized that the specific delivery of a PPARγ agonist to inflamed plaques could reduce plaque burden and inflammation without systemic adverse effects. Methods: Herein, we newly developed a macrophage mannose receptor (MMR)-targeted biocompatible nanocarrier loaded with lobeglitazone (MMR-Lobe), which is able to specifically activate PPARγ pathways within inflamed high-risk plaques, and investigated its anti-atherogenic and anti-inflammatory effects both in in vitro and in vivo experiments. Results: MMR-Lobe had a high affinity to macrophage foam cells, and it could efficiently promote cholesterol efflux via LXRα-, ABCA1, and ABCG1 dependent pathways, and inhibit plaque protease expression. Using in vivo serial optical imaging of carotid artery, MMR-Lobe markedly reduced both plaque burden and inflammation in atherogenic mice without undesirable systemic effects. Comprehensive analysis of en face aorta by ex vivo imaging and immunostaining well corroborated the in vivo findings. Conclusion: MMR-Lobe was able to activate PPARγ pathways within high-risk plaques and effectively reduce both plaque burden and inflammation. This novel targetable PPARγ activation in macrophages could be a promising therapeutic strategy for high-risk plaques.

We integrated two-photon microscopy (TPM), second harmonic imaging microscopy (SHIM), near-infrared fluorescence microscopy (NIRF), confocal laser scanning microscopy (CLSM), and fluorescence lifetime imaging microscopy (FLIM) in one microscope system. Using our microscope system, five different images were obtained simultaneously.

Multimodal optical coherence tomography (OCT) techniques are promising diagnostic tools to accurately assess high-risk atherosclerotic plaques. For rapid translation into clinical practice, the techniques should be performed through an intravascular imaging catheter without exogenous contrast agents under the same procedures as conventional imaging. In this study, we developed a label-free, multispectral, and catheter-based imaging system to simultaneously visualize the morphological and compositional information of coronary plaques by combining fluorescence lifetime imaging (FLIm) and OCT. Using a broadband hybrid optical rotary joint and a dual-modal imaging catheter, intravascular combined FLIm-OCT imaging was safely performed in an in vivo atherosclerotic coronary artery of atherosclerotic swine models without any imaging agent. Along with detailed coronary microstructure by OCT, the multispectral FLIm could accurately visualize fluorescence lifetime signature of key biochemical components of plaque in vivo (lipid, macrophage, and fibrous tissue) when comparing the corresponding histopathological stained-sections and ex vivo FLIm microscopy images. Especially, significant differences in fluorescence lifetime distribution were noted between lipid and macrophage (p < 0.0001), which were mostly indistinguishable with standalone OCT. Also, fluorescence lifetime distributions were significantly different according to plaque types (normal, fibrous vs. lipid-rich inflamed plaque, p < 0.0001). With these statistical differences in plaque types and components, lipid distribution characterization and inflammation level estimation were provided in a pixel-by-pixel manner for the further assessment of the high-risk atherosclerotic plaque. This highly translatable imaging strategy can offer new opportunity for clinical intracoronary detection of high-risk plaques and will be a promising next-generation multimodal OCT technique.

Purpose: Intravascular optical coherence tomography (IV-OCT) is a high-resolution imaging method used to visualize the microstructure of arterial walls in vivo. IV-OCT enables the clinician to clearly observe and accurately measure stent apposition and neointimal coverage of coronary stents, which are associated with side effects such as in-stent thrombosis. In this study, the authors present an algorithm for quantifying stent apposition and neointimal coverage by automatically detecting lumen contours and stent struts in IV-OCT images. Methods: The algorithm utilizes OCT intensity images and their first and second gradient images along the axial direction to detect lumen contours and stent strut candidates. These stent strut candidates are classified into true and false stent struts based on their features, using an artificial neural network with one hidden layer and ten nodes. After segmentation, either the protrusion distance (PD) or neointimal thickness (NT) for each strut is measured automatically. In randomly selected image sets covering a large variety of clinical scenarios, the results of the algorithm were compared to those of manual segmentation by IV-OCT readers. Results: Stent strut detection showed a 96.5% positive predictive value and a 92.9% true positive rate. In addition, case-by-case validation also showed comparable accuracy for most cases. High correlation coefficients (R > 0.99) were observed for PD and NT between the algorithmic and the manual results, showing little bias (0.20 and 0.46 μm, respectively) and a narrow range of limits of agreement (36 and 54 μm, respectively). In addition, the algorithm worked well in various clinical scenarios and even in cases with a low level of stent malapposition and neointimal coverage. Conclusions: The presented automatic algorithm enables robust and fast detection of lumen contours and stent struts and provides quantitative measurements of PD and NT. In addition, the algorithm was validated using various clinical cases to demonstrate its reliability. Therefore, this technique can be effectively utilized for clinical trials on stent-related side effects, including in-stent thrombosis and in-stent restenosis.

Aims Inflammation plays essential role in development of plaque disruption and coronary stent-associated complications. This study aimed to examine whether intracoronary dual-modal optical coherence tomography (OCT)-near-infrared fluorescence (NIRF) structural–molecular imaging with indocyanine green (ICG) can estimate inflammation in swine coronary artery. Methods and results After administration of clinically approved NIRF-enhancing ICG (2.0 mg/kg) or saline, rapid coronary imaging (20 mm/s pullback speed) using a fully integrated OCT-NIRF catheter was safely performed in 12 atheromatous Yucatan minipigs and in 7 drug-eluting stent (DES)-implanted Yorkshire pigs. Stronger NIRF activity was identified in OCT-proven high-risk plaque compared to normal or saline-injected controls ( P = 0.0016), which was validated on ex vivo fluorescence reflectance imaging. In vivo plaque target-to-background ratio (pTBR) was much higher in inflamed lipid-rich plaque compared to fibrous plaque ( P < 0.0001). In vivo and ex vivo peak pTBRs correlated significantly ( P < 0.0022). In vitro cellular ICG uptake and histological validations corroborated the OCT-NIRF findings in vivo . Indocyanine green colocalization with macrophages and lipids of human plaques was confirmed with autopsy atheroma specimens. Two weeks after DES deployment, OCT-NIRF imaging detected strong NIRF signals along stent struts, which was significantly higher than baseline ( P = 0.0156). Histologically, NIRF signals in peri-strut tissue co-localized well with macrophages. Conclusion The OCT-NIRF imaging with a clinical dose of ICG was feasible to accurately assess plaque inflammation and DES-related inflammation in a beating coronary artery. This highly translatable dual-modal molecular–structural imaging strategy could be relevant for clinical intracoronary estimation of high-risk plaques and DES biology.

The pathophysiological progression of chronic diseases, including atherosclerosis and cancer, is closely related to compositional changes in biological tissues containing endogenous fluorophores such as collagen, elastin, and NADH, which exhibit strong autofluorescence under ultraviolet excitation. Fluorescence lifetime imaging (FLIm) provides robust detection of the compositional changes by measuring fluorescence lifetime, which is an inherent property of a fluorophore. In this paper, we present a dual-modality system combining a multispectral analog-mean-delay (AMD) FLIm and a high-speed swept-source optical coherence tomography (OCT) to simultaneously visualize the cross-sectional morphology and biochemical compositional information of a biological tissue. Experiments using standard fluorescent solutions showed that the fluorescence lifetime could be measured with a precision of less than 40 psec using the multispectral AMD-FLIm without averaging. In addition, we performed ex vivo imaging on rabbit iliac normal-looking and atherosclerotic specimens to demonstrate the feasibility of the combined FLIm-OCT system for atherosclerosis imaging. We expect that the combined FLIm-OCT will be a promising next-generation imaging technique for diagnosing atherosclerosis and cancer due to the advantages of the proposed label-free high-precision multispectral lifetime measurement.

Intraplaque hemorrhages (IPH) accelerate plaque destabilization via oxidative stress, free cholesterol secretion, macrophage accumulation, and necrotic core expansion. Macrophages in these hemoglobin-exposed segments differentiate into a distinct phenotype characterized by the expression of CD163

Micro-optical coherence tomography (μOCT) is an advanced imaging technique that acquires a three-dimensional microstructure of biological samples with a high spatial resolution, up to 1 μm, by using a broadband light source and a high numerical aperture (NA) lens. As high NA produces a short depth of focus (DOF), extending the DOF is necessary to obtain a reasonable imaging depth. However, due to the complexity of optics and the limited space, it has been challenging to fabricate endoscopic μOCT, which is essential for clinical translation. Here, we report an endoscopic μOCT probe with an extended DOF by using a binary phase spatial filter. The imaging results from latex beads demonstrated that the μOCT probe achieved an axial resolution of 2.49 μm and a lateral resolution of 2.59 μm with a DOF extended by a factor of 2. The feasibility of clinical use was demonstrated by ex vivo imaging of the rabbit iliac artery.

Background— Lipid-rich inflamed coronary plaques are prone to rupture. The purpose of this study was to assess lipid-rich inflamed plaques in vivo using fully integrated high-speed optical coherence tomography (OCT)/near-infrared fluorescence (NIRF) molecular imaging with a Food and Drug Administration–approved indocyanine green (ICG). Methods and Results— An integrated high-speed intravascular OCT/NIRF imaging catheter and a dual-modal OCT/NIRF system were constructed based on a clinical OCT platform. For imaging lipid-rich inflamed plaques, the Food and Drug Administration–approved NIRF-emitting ICG (2.25 mg/kg) or saline was injected intravenously into rabbit models with experimental atheromata induced by balloon injury and 12- to 14-week high-cholesterol diets. Twenty minutes after injection, in vivo OCT/NIRF imaging of the infrarenal aorta and iliac arteries was acquired only under contrast flushing through catheter (pullback speed up to ≤20 mm/s). NIRF signals were strongly detected in the OCT-visualized atheromata of the ICG-injected rabbits. The in vivo NIRF target-to-background ratio was significantly larger in the ICG-injected rabbits than in the saline-injected controls ( P P P r =0.85) without significant bias (0.41). Cellular ICG uptake, correlative fluorescence microscopy, and histopathology also corroborated the in vivo imaging findings. Conclusions— Integrated OCT/NIRF structural/molecular imaging with a Food and Drug Administration –approved ICG accurately identified lipid-rich inflamed atheromata in coronary-sized vessels. This highly translatable dual-modal imaging approach could enhance our capabilities to detect high-risk coronary plaques.

This work reports the use of pulsed wire evaporation (PWE) method to prepare cobalt (Co) nano-particles. The effect of charging voltage on the average particle size and particle morphology was studied. The Co nano-particles were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and BET surface area analysis. SEM and TEM observations showed that the Co particles had spherical shape and were linked to each other because of their magnetic property. The XRD analyses confirmed that Co nano-particles had FCC structure without any presence of impurity phase. Average particle size was calculated by three methods; TEM, BET and XRD. The results showed that the particle size decreased with increasing charging voltage and then attempted to saturate, which was explained with crystallite size of the Co wire, superheating factor and specific energy input into the wire.

In this study, magnetic pulsed compaction (MPC), a very short duration, high-density preform molding method was used to produce bulks from initial WC–7.5 wt.% Co and WC–12 wt.% Co with varied consolidation conditions, followed by subsequent sintering. Mechanically alloyed powders with compositions of WC–7.5 wt.% Co and WC–12 wt.% Co were used and combinations of pressures of 0.5G Pa, 1.0 GPa, 1.5 GPa, 2.0 GPa, 2.5 GPa and 3 GPa were applied to form the bulks. Maximum densities for WC–7.5 wt.% Co and WC–12 wt.% Co after magnetic pulsed compaction were found to be around 70%, which later turned nearly 92% after sintering, while a maximum hardness of over 1430 Hv was observed in WC–12 wt.% Co sample. Density, hardness and crack length all suggested a gradual pattern or trend in MPC-ed bulks that can yield almost fully dense, commercially applicable products with high mechanical properties after sintering.

Introduction: Atherosclerosis is a process of lipid accumulation and inflammation. In particular, plaque macrophages are associated with fibrous cap destabilization and rupture. We hypothesized that the specific delivery of a PPAR-γ agonist to inflamed plaques via nanoprobe (NP) targeting macrophage mannose receptors could reduce plaque burden and inflammation. Methods and Results: Macrophage mannose receptor targetable nanoprobe (MMR-NP) was fabricated by chemically conjugating thiolated glycol chitosan with mannose-PEG-maleimide, followed by incorporating PPAR-γ agonist (lobeglitazone) into this nanoscale delivery system (MMR-Lobe). For in vivo monitoring of therapeutic response, near-infrared fluorescence NP was prepared by conjugation of Cy5.5 (ext/emi 675/694 nm) with MMR-NP. In cellular uptake study, the MMR-NP showed high affinity to mannose receptors on macrophages. MMR-Lobe attenuated LPS-induced inflammatory cytokines such as TNF-α, IL-6, and MMP-9 in RAW264.7 cells. Additionally, MMR-Lobe increased expression of ABCA1, ABCG1 and LXR-α, known as PPAR-γ regulator genes involved in cholesterol efflux, in RAW264.7 cells. Using a customized high-resolution intravital fluorescence microscope, the in vivo serial imaging of carotid atheroma in apoE-/- mice injected with MMR-Lobe (7 mg/kg, twice weekly for 4 weeks) revealed a significant decrease in plaque burden and inflammation (Figure) as compared to baseline, or non-treated controls, or p.o. Lobe treated mice (p Conclusions: MMR-Lobe was able to selectively target atheroma macrophages, and effectively reduce both plaque burden and inflammation as assessed by serial intravital optical imaging. We suggest that nanoprobe-mediated PPAR-γ agonist delivery targeting plaque macrophages holds a promising theranostic approach for high-risk atheromata.

Background: Reactive oxygen species (ROS) play a central role in cigarette smoking-induced atherogenesis. The present study aims to assess the smoking-induced acute oxidative stress within vasculatures, and evaluates whether the resveratrol, a natural polyphenol antioxidant, can counteract this ROS production, using a customized, high resolution intravital optical imaging in real-time. Methods and Results: 20-week-old male C57BL/6 mice were divided into four groups according to the preceding administration of resveratrol (R) (25mg/kg via gavage, for 7 days) and exposure to cigarette smoke (CS). To in vivo assess acute oxidative stress in blood vessels, dihydroethidium, which forms a red fluorescence (ethidium, excitation/emission: 520nm/610nm) upon reaction with ROS, was injected intraperitoneally. During CS exposure, temporal changes of fluorescence signals from the mouse cremaster muscle including vasculatures were assessed by intravital optical imaging for 15 minutes. Fluorescence signals were much more pronounced in CS exposed mice than controls (p Conclusions: The intravital optical imaging was able to in vivo estimate the dynamic changes of ROS production by CS exposure. Our data demonstrated that even a brief exposure to CS increased oxidative stress in vasculatures promptly, and the resveratrol exerts protective effects against the CS-induced acute oxidative stress.

Intravascular optical coherence tomography (IV-OCT) is a high-resolution imaging method used to visualize the microstructure of arterial walls in vivo. IV-OCT enables the clinician to clearly observe and accurately measure stent apposition and neointimal coverage of coronary stents, which are associated with side effects such as in-stent thrombosis. In this study, the authors present an algorithm for quantifying stent apposition and neointimal coverage by automatically detecting lumen contours and stent struts in IV-OCT images.The algorithm utilizes OCT intensity images and their first and second gradient images along the axial direction to detect lumen contours and stent strut candidates. These stent strut candidates are classified into true and false stent struts based on their features, using an artificial neural network with one hidden layer and ten nodes. After segmentation, either the protrusion distance (PD) or neointimal thickness (NT) for each strut is measured automatically. In randomly selected image sets covering a large variety of clinical scenarios, the results of the algorithm were compared to those of manual segmentation by IV-OCT readers.Stent strut detection showed a 96.5% positive predictive value and a 92.9% true positive rate. In addition, case-by-case validation also showed comparable accuracy for most cases. High correlation coefficients (R0.99) were observed for PD and NT between the algorithmic and the manual results, showing little bias (0.20 and 0.46 μm, respectively) and a narrow range of limits of agreement (36 and 54 μm, respectively). In addition, the algorithm worked well in various clinical scenarios and even in cases with a low level of stent malapposition and neointimal coverage.The presented automatic algorithm enables robust and fast detection of lumen contours and stent struts and provides quantitative measurements of PD and NT. In addition, the algorithm was validated using various clinical cases to demonstrate its reliability. Therefore, this technique can be effectively utilized for clinical trials on stent-related side effects, including in-stent thrombosis and in-stent restenosis.

Intravascular optical coherence tomography (IV-OCT) is a high-resolution imaging method used to visualize the internal structures of walls of coronary arteries in vivo. However, accurate characterization of atherosclerotic plaques with gray-scale IV-OCT images is often limited by various intrinsic artifacts. In this study, we present an algorithm for characterizing lipid-rich plaques with a spectroscopic OCT technique based on a Gaussian center of mass (GCOM) metric. The GCOM metric, which reflects the absorbance properties of lipids, was validated using a lipid phantom. In addition, the proposed characterization method was successfully demonstrated in vivo using an atherosclerotic rabbit model and was found to have a sensitivity and specificity of 94.3% and 76.7% for lipid classification, respectively.

Macrophages mediate atheroma expansion and disruption, and denote high-risk arterial plaques. Therefore, they are substantially gaining importance as a diagnostic imaging target for the detection of rupture-prone plaques. Here, we developed an injectable near-infrared fluorescence (NIRF) probe by chemically conjugating thiolated glycol chitosan with cholesteryl chloroformate, NIRF dye (cyanine 5.5 or 7), and maleimide-polyethylene glycol-mannose as mannose receptor binding ligands to specifically target a subset of macrophages abundant in high-risk plaques. This probe showed high affinity to mannose receptors, low toxicity, and allowed the direct visualization of plaque macrophages in murine carotid atheroma. After the scale-up of the MMR-NIRF probe, the administration of the probe facilitated in vivo intravascular imaging of plaque inflammation in coronary-sized vessels of atheromatous rabbits using a custom-built dual-modal optical coherence tomography (OCT)-NIRF catheter-based imaging system. This novel imaging approach represents a potential imaging strategy enabling the identification of high-risk plaques in vivo and holds promise for future clinical implications.

While high-speed intracoronary optical coherence tomography (OCT) provides three-dimensional (3D) visualization of coronary arteries in vivo, imaging speeds remain insufficient to avoid motion artifacts induced by heartbeat, limiting the clinical utility of OCT. In this paper, we demonstrate development of a high-speed intracoronary OCT system (frame rate: 500 frames/s, pullback speed: 100 mm/s) along with prospective electrocardiogram (ECG) triggering technology, which enabled volumetric imaging of long coronary segments within a single cardiac cycle (70 mm pullback in 0.7 s) with minimal cardiac motion artifact. This technology permitted detailed visualization of 3D architecture of the coronary arterial wall of a swine in vivo and fine structure of the implanted stent. (C) 2016 Optical Society of America

In this research, magnetic pulsed compaction (MPC), a very short duration, high-density perform molding method was used to produce bulks from initial WC 7.5 wt% Co and WC 12 wt% Co, followed by subsequent sintering. Mechanically alloyed powders with compositions of WC 7.5 wt% Co and WC 12 wt% Co were used for molding where each specimen weighed 2.0 g and pressures of 0.5 GPa, 1.0 GPa, 1.5 GPa, 2.0 GPa, 2.5 GPa and 3 GPa were applied to form the bulks. Maximum densities for WC 7.5 wt% Co and WC 12 wt% Co after magnetic pulsed compaction were found to be around 64% and 67%, respectively, which later turned into nearly 97% after sintering, while a maximum hardness of over 1430 HV was observed in WC 12 wt% Co sample. Density, hardness and crack length all suggested a gradual pattern or trend in MPC-ed bulks that can yield almost fully dense, commercially applicable products with high mechanical properties after sintering.

In this research, the coating behavior of Mg and Fe desulfurization powder fabricated by low energy and conventional planetary mill equipment was investigated as a function of milling time, which produces uniform Fe coated powders due to milling energy. Since high energy ball milling results in breaking the Fe coated Mg powders into coarse particles, low energy ball milling was considered appropriate for this study, and can be implemented in desulfurization industry widely. XRD and FE-SEM analyses were carried out to investigate the microstructure and distribution of the coating material. The thickness of the Fe coating layer reaches a maximum of 14 at 20 milling hours. The BCC structures of Fe particles are deformed due to the slip system of Fe coated Mg particles.

WOS:000301482400001 Nanosized Ag particles were obtained in liquid medium, which is composed of deionized water and sodium hexametaphosphate, using pulsed wire evaporation within hundreds of microseconds from pure initial Ag wire (99.98%), with varying voltage. Changes in powder morphology and microstructure due to change in supply voltage was observed by FE-SEM and HR-TEM, and phase structure of powders was analyzed by XRD. The results revealed that average particle size slightly increased with increasing supply voltage without any impurity and oxide phase, which was explained in terms of addition of stabilizer into the coolant liquid. The experimental results also suggest that addition of sodium hexametaphosphate into the coolant liquid is good for enhancing the dispersibility property of silver nanopowders.

Silfine. Co., LTD, 374-2, Shinsuri, Eumbongmyeon, AsanCity, Chungnam, 336-862, Korea(Received May 7, 2010, Revised May 27, 2010, Accepted June 8, 2010)Abstract In this research, the optimal manufacturing conditions of fine Si powders from Si scrap were inves-tigated as a function of different initial powder size using the high-energy ball milling equipment, which producesthe fine powder by means of an ultra high-energy within a short duration. The morphological change of the pow-ders according to the milling time was observed by Scanning electron microscopy (SEM). With the increasingmilling time, the size of Si powder was decreased. In addition, more energy and stress for milling were requiredwith the decreasing initial powder size. The refinement of Si scrap was rapidly carried out at 10min ball millingtime. However, the refined powder started to agglomerate at 30 min milling time, while the powder size becameuniform at 60 min milling time.Keywords : Microstructure, High energy milling, Si, Silicon scrap, Refinement

Introduction: Intraplaque hemorrhages (IPHs) are associated with rupture-prone plaques. Within IPHs, macrophages differentiate into a specific phenotype characterized by the expression of mannose receptors. The purpose of this study was to investigate the feasibility of intravascular optical coherence tomography (OCT)-near infrared fluorescence (NIRF) structural-molecular imaging combined with a NIRF probe targeting mannose receptors to estimate IPHs in vivo. Methods and Results: IPH was induced by injecting centrifuged autologous erythrocytes through a micro-infusion catheter into rabbit aortic plaques. Normal chow diet was continued for an additional 6 weeks for macrophage differentiation. 48 hours after intravenous injection of our newly synthesized NIRF labeled nanoprobe (ex/em 750/773 nm) targeting macrophage mannose receptors at a dose of 10 mg/kg, OCT-NIRF imaging demonstrated highly enhanced NIRF signals in IPH lesions characterized by black-dotted neovessels surrounded with heterogenous OCT signals (asterisk), suggesting the association of mannose receptor positive macrophages with intraplaque hemorrhagic transformation (Figure). FM and histologic findings from the corresponding sister sections corroborated the in vivo imagings, which demonstrated the co-localization of NIRF signals with macrophage mannose receptors and hemorrhagic compositions. Conclusions: OCT-NIRF imaging with a NIRF probe targeting mannose receptors could provide a promising novel strategy to estimate IPH-associated macrophages and detect high-risk plaques.

Introduction: Plaque inflammation is associated with fibrous cap destabilization and rupture. Hypothesis: We hypothesized that the specific delivery of a novel PPARγ agonist, lobeglitazone, to inflamed plaques via nanoparticle (NP) targeting mannose receptors on macrophages could reduce inflammation in atheromata and thus, tested it using serial optical intravital molecular imaging. Methods and Results: A novel near-infrared fluorescence (NIRF) probe was fabricated by chemically conjugating thiolated glycol chitosan with mannose-PEG, and NIRF dye Cy5.5 (ext/emi 675/694 nm) for imaging. Lobeglitazone was incorporated into NIRF-NP targeting macrophage mannose receptors (MMR). In vitro, MMR-NIRF-NP was selectively uptaken by RAW264.7 cells, and NIRF signals were estimated to be 10-fold over control group (p Conclusions: Lobeglitazone-incorporated MMR-NIRF-NP was able to selectively target and image atheroma macrophages, and effectively reduce plaque inflammation as assessed by intravital optical imaging. NP-mediated lobeglitazone delivery could be a promising therapeutic strategy for high-risk plaque stabilization.

Recent advances in high-speed intracoronary optical coherence tomography (OCT) have enabled visualization of 3-dimensional (3D) microstructure of long coronary artery segments in vivo [(1)][1]; however, imaging speed remains insufficient to avoid detrimental cardiac motion artifacts in imaging

Background: Acute coronary syndrome is frequently caused by rupture of macrophage abundant plaques with a large lipid-rich core. The present study aimed to investigate whether a fully integrated OCT/NIRF imaging combined with a clinically available near-infrared fluorescence (NIRF) enhancing ICG can detect the inflamed, lipid-rich plaques in swine coronary atheromata whose phenotype is similar to human vulnerable fibroatheroma. Methods and Results: Accelerated atherosclerosis was made by coronary balloon denudation in alloxan induced diabetic minipigs. A rapid coronary imaging (20 mm/sec pullback speed) using a fully integrated OCT/NIRF catheter was safely performed 30 minutes after I.V. injection of ICG (2.0 mg/kg) just under contrast purge. OCT clearly identified the lipid-rich plaques with fibrous cap. Simultaneously acquired, distance-calibrated NIRF imaging detected lipid-laden macrophage signals in OCT-proven plaques (figure). The in vivo plaque target-to-background ratio (pTBR) was significantly higher in ICG-injected swine compared to non-diabetic swines or saline-injected controls (pex vivo fluorescence reflectance imaging (FRI) (figure). The in vivo and ex vivo peak pTBRs correlated significantly (pIn vitro experiments, and histopathology including fluorescence microscopic imaging and immunostaining of the plaque sections corroborated the findings in vivo . Conlusions: An OCT/NIRF imaging with a clinical use of ICG accurately identified macrophage abundant, lipid-rich coronary plaques in diabetic atheromatous minipigs. This highly translatable dual-modal molecular-structural imaging could be relevant for clinical intracoronary detection of high-risk plaques.