Luminal Contour Research Articles

Automated finite element approach to generate anatomical patient-specific biomechanical models of atherosclerotic arteries from virtual histology-intravascular ultrasound.

Despite advancements in early detection and treatment, atherosclerosis remains the leading cause of death across all cardiovascular diseases (CVD). Biomechanical analysis of atherosclerotic lesions has the potential to reveal biomechanically instable or rupture-prone regions. Treatment decisions rarely consider the biomechanics of the stenosed lesion due in-part to difficulties in obtaining this information in a clinical setting. Previous 3D FEA approaches have incompletely incorporated the complex curvature of arterial geometry, material heterogeneity, and use of patient-specific data. To address these limitations and clinical need, herein we present a user-friendly fully automated program to reconstruct and simulate the wall mechanics of patient-specific atherosclerotic coronary arteries. The program enables 3D reconstruction from patient-specific data with heterogenous tissue assignment and complex arterial curvature. Eleven arteries with coronary artery disease (CAD) underwent baseline and 6-month follow-up angiographic and virtual histology-intravascular ultrasound (VH-IVUS) imaging. VH-IVUS images were processed to remove background noise, extract VH plaque material data, and luminal and outer contours. Angiography data was used to orient the artery profiles along the 3D centerlines. The resulting surface mesh is then resampled for uniformity and tetrahedralized to generate the volumetric mesh using TetGen. A mesh convergence study revealed edge lengths between 0.04 mm and 0.2 mm produced constituent volumes that were largely unchanged, hence, to save computational resources, a value of 0.2 mm was used throughout. Materials are assigned and finite element analysis (FEA) is then performed to determine stresses and strains across the artery wall. In a representative artery, the highest average effective stress was in calcium elements with 235 kPa while necrotic elements had the lowest average stress, reaching as low as 0.79 kPa. After applying nodal smoothening, the maximum effective stress across 11 arteries remained below 288 kPa, implying biomechanically stable plaques. Indeed, all atherosclerotic plaques remained unruptured at the 6-month longitudinal follow up diagnosis. These results suggest our automated analysis may facilitate assessment of atherosclerotic plaque stability.

Incidence and natural history of coronary evagination after implanted biodegradable polymer sirolimus-eluting stent.

AimsThe incidence and temporal change in coronary evagination (CE) after first-generation drug-eluting stent implantation is well established, whereas that after biodegradable polymer sirolimus-eluting stent (BP-SES) implantation has not yet been evaluated. The aim of this study is to assess the incidence and natural history of CE after BP-SES implantation.Methods and resultsIn this multicenter registry, stable coronary lesions treated by Ultimaster BP-SES were evaluated by serial optical frequency domain imaging (OFDI) (at 0–1–12 or 0–3–12 months) and the incidence of CE was assessed. Coronary evagination was defined as the presence of an outward bulge in luminal vessel contour between apposed struts according to the following criteria: (i) evagination depth ≥10% of nominal stent diameter and (ii) evagination length ≥3.0 mm. Optical frequency domain imaging was obtained in 98, 47, 49, and 87 lesions at 0, 1, 3, and 12 months, respectively. Coronary evagination was observed in 20 (42.6%) and 12 (24.5%) lesions at 1 and 3 months, respectively, and all but one CE had resolved at 12 months. At 12 months, the mean CE area was almost zero and the mean malapposed stent area was also decreased. Comparison of the serial OFDI images indicated that CEs originated mostly from acute stent malapposition or coronary dissection behind the implanted stent.ConclusionsIn stable lesions, CE was occasionally observed with Ultimaster BP-SES at 1–3 months but mostly resolved within 12 months, without late-acquired stent malapposition. These findings suggest the safety and feasibility of biodegradable polymer coating on DES.

Can ultrasonography differentiate anastomotic and non-anastomotic biliary strictures after orthotopic liver transplantation- a single‐center experience

PurposeTo evaluate the role of ultrasonography (US) in differentiating anastomotic biliary strictures (AS) and non-anastomotic biliary strictures (NAS) after orthotopic liver transplantation (OLT). MethodThis retrospective study included 1259 OLT recipients between 2005−2018. Seventy-six with anastomotic strictures (AS) and 103 with non-anastomotic strictures (NAS) were analyzed. The reference standard was cholangiography. The sensitivity, specificity, accuracy of US was evaluated. ResultsThere were significant differences between AS and NAS groups (p < 0.001) for skipped and irregular dilatation of intrahepatic bile duct and visualization of hilar biliary lumen. The better US imaging feature for NAS was poorly visualized and non- visible hilar bile duct luminal contour. The sensitivity, specificity and accuracy were 94.2 %, 84.2 % and 88.9 % respectively. Combined two predictors greatly increased the specificity to 93.4 % while diminished its sensitivity and accuracy. ConclusionUS is useful and efficient to differentiate AS and NAS after OLT.

Potential relationship between high wall shear stress and plaque rupture that cause acute coronary syndrome: insights from optical coherence tomography based computational fluid dynamic simulation

Abstract Background The direct relationship between plaque rupture (PR) that cause acute coronary syndrome (ACS) and wall shear stress (WSS) remains uncertain. Methods From the Kobe University ACS-OCT registry, one hundred ACS patients whose culprit lesions had PR documented by optical coherence tomography (OCT) were enrolled. Lesion-specific 3D coronary artery models were created using OCT data. Specifically, at the ruptured portion, the tracing of the luminal edge of the residual fibrous cap was smoothly extrapolated to reconstruct the luminal contour before PR. Then, WSS was computed from computational fluid dynamics (CFD) analysis by a single core laboratory. Relationships between WSS and the location of PR were assessed with 1) longitudinal 3-mm segmental analysis and 2) circumferential analysis. In the longitudinal segmental analysis, each culprit lesion was subdivided into five 3-mm segments with respect to the minimum lumen area (MLA) location at the centered segment (Figure. 1). In the circumferential analysis, we measured WSS values at five points from PR site and non-PR site on the cross-sections with PR. Also, each ruptured plaque was categorized into the lateral type PR (L-PR), central type PR (C-PR), and others according to the relation between the site of tearing and the cavity (Figure. 2). Results In the longitudinal 3-mm segmental analysis, the incidences of PR at upstream (UP1 and 2), MLA, and downstream (DN1 and 2) were 45%, 40%, and 15%, respectively. The highest average WSS was located in UP1 in the upstream PR (UP1: 15.5 (10.4–26.3) vs. others: 6.8 (3.3–14.7) Pa, p&amp;lt;0.001) and MLA segment in the MLA PR (MLA: 18.8 (6.0–34.3) vs. others: 6.5 (3.1–11.8) Pa, p&amp;lt;0.001), and the second highest WSS was located at DN1 in the downstream PR (DN1: 5.8 (3.7–11.5) vs. others: 5.5 (3.7–16.5) Pa, p=0.035). In the circumferential analysis, the average WSS at PR site was significantly higher than that of non-PR site (18.7 (7.2–35.1) vs. 13.9 (5.2–30.3) Pa, p&amp;lt;0.001). The incidence of L-PR, C-PR, and others were 51%, 42%, and 7%, respectively. In the L-PR, the peak WSS was most frequently observed in the lateral site (66.7%), whereas that in the C-PR was most frequently observed in the center site (70%) (Figure. 3). In the L-PR, the peak WSS value was significantly lower (44.6 (19.6–65.2) vs. 84.7 (36.6–177.5) Pa, p&amp;lt;0.001), and the thickness of broken fibrous cap was significantly thinner (40 (30–50) vs. 80 (67.5–100) μm, p&amp;lt;0.001), and the lumen area at peak WSS site was significantly larger than those of C-PR (1.5 (1.3–2.0) vs. 1.4 (1.1–1.6) mm2, p=0.008). Multivariate analysis demonstrated that the presence of peak WSS at lateral site, thinner broken fibrous cap thickness, and larger lumen area at peak WSS site were independently associated with the development of the L-PR. Conclusions A combined approach with CFD simulation and morphological plaque evaluation by using OCT might be helpful to predict future ACS events induced by PR. Funding Acknowledgement Type of funding source: None

Cystic Adventitial Disease of the Popliteal Artery : A Rare Case with Review of Literature

Cystic adventitial disease (CAD) is a rare non-atheromatous affection of the popliteal artery, often misdiagnosed, leading to increasing morbidity and eventual disability. More commonly unilateral, this condition tends to affect males in their fourth and fifth decades. Diagnosis is usually suggested with ultrasonography (USG) and is further confirmed with digital subtraction angiography (DSA). Magnetic resonance imaging (MRI) angiography is another non-invasive method for diagnosis of CAD. Where DSA gives information about the luminal contour and severity of narrowing, MRI helps in evaluation of the extramural component and surrounding soft tissue. Management is in the form of resection of the involved popliteal artery segment.

Automated Artery Localization and Vessel Wall Segmentation using Tracklet Refinement and Polar Conversion.

Quantitative analysis of blood vessel wall structures is important to study atherosclerotic diseases and assess cardiovascular event risks. To achieve this, accurate identification of vessel luminal and outer wall contours is needed. Computer-assisted tools exist, but manual preprocessing steps, such as region of interest identification and/or boundary initialization, are still needed. In addition, prior knowledge of the ring shape of vessel walls has not been fully explored in designing segmentation methods. In this work, a fully automated artery localization and vessel wall segmentation system is proposed. A tracklet refinement algorithm was adapted to robustly identify the artery of interest from a neural network-based artery centerline identification architecture. Image patches were extracted from the centerlines and converted in a polar coordinate system for vessel wall segmentation. The segmentation method used 3D polar information and overcame problems such as contour discontinuity, complex vessel geometry, and interference from neighboring vessels. Verified by a large (>32000 images) carotid artery dataset collected from multiple sites, the proposed system was shown to better automatically segment the vessel wall than traditional vessel wall segmentation methods or standard convolutional neural network approaches. In addition, a segmentation uncertainty score was estimated to effectively identify slices likely to have errors and prompt manual confirmation of the segmentation. This robust vessel wall segmentation system has applications in different vascular beds and will facilitate vessel wall feature extraction and cardiovascular risk assessment.

Eponymous "valves" of the nasolacrimal drainage apparatus. I. A historical review.

The nasolacrimal drainage apparatus (NDA) is of interest to anatomists, radiologists, and ophthalmologists alike, owing to its intricate luminal contour, complex surrounding structural morphology, and its clinical relevance. Here, we review the history of anatomical descriptions of so-called luminal "valves" of the NDA, including the numerous historical figures whose eponyms adorn the NDA. By 1908, multiple false "valves" that are likely no more than mounds of mucosa along the NDA had been recorded. In the modern era, these have all been largely considered speculative in nature and function aside from the consistently described true valve of Hasner (plica lacrimalis). Back then, eight so-called "valves" were believed to be identifiable. These were the "valves" of Foltz, Bochdalek, Rosenmüller, Huschke, Aubaret, Béraud or Krause, Taillefer, and Hasner or Cruveilhier or Bianchi. With the advent of detailed characterization through modern high-resolution imaging techniques, such as digital subtraction dacryocystography (DS-DCG), many of these valvular folds have come into question owing to their inconsistent identification. This historical review should be useful for greater understanding and accurate contextual interpretation of "valves" encountered on DS-DCG studies, and in clinical management and therapeutic planning of patients prior to undergoing luminal procedures on the NDA. Clin. Anat., 2018. © 2018 Wiley Periodicals, Inc.

MR Venous Flow in Sigmoid Sinus Diverticulum.

Case reports demonstrate that coiling of a sigmoid sinus diverticulum can treat pulsatile tinnitus. We hypothesized that MR imaging 4D flow and computational fluid dynamics would reveal distinct blood flow patterns in the venous outflow tract in these patients. Patients with pulsatile tinnitus of suspected venous etiology underwent MR imaging at 3T, using venous phase contrast-enhanced MR angiography, 4D flow, and 2D phase contrast. The contrast-enhanced MRA contours were evaluated to determine the presence and extent of a sigmoid sinus diverticulum. Computational fluid dynamics analysis was performed using the 4D flow inlet flow and the luminal contours from contrast-enhanced MRA as boundary conditions. In addition, computational fluid dynamics was performed for the expected post treatment conditions by smoothing the venous geometry to exclude the sigmoid sinus diverticulum from the anatomic boundary conditions. Streamlines were generated from the 4D flow and computational fluid dynamics velocity maps, and flow patterns were examined for the presence of rotational components. Twenty-five patients with pulsatile tinnitus of suspected venous etiology and 10 control subjects were enrolled. Five (20%) of the symptomatic subjects had sigmoid sinus diverticula, all associated with an upstream stenosis. In each of these patients, but none of the controls, a stenosis-related flow jet was directed toward the opening of the sigmoid sinus diverticulum with rotational flow patterns in the sigmoid sinus diverticulum and parent sigmoid sinus on both 4D flow and computational fluid dynamics. Consistent patterns of blood flow can be visualized in a sigmoid sinus diverticulum and the parent sinus using 4D flow and computational fluid dynamics. Strong components of rotational blood flow were seen in subjects with sigmoid sinus diverticula that were absent in controls.

3D reconstruction of coronary arteries from 2D angiographic projections using non-uniform rational basis splines (NURBS) for accurate modelling of coronary stenoses.

ObjectiveAssessment of coronary stenosis severity is crucial in clinical practice. This study proposes a novel method to generate 3D models of stenotic coronary arteries, directly from 2D coronary images, and suitable for immediate assessment of the stenosis severity.MethodsFrom multiple 2D X-ray coronary arteriogram projections, 2D vessels were extracted. A 3D centreline was reconstructed as intersection of surfaces from corresponding branches. Next, 3D luminal contours were generated in a two-step process: first, a Non-Uniform Rational B-Spline (NURBS) circular contour was designed and, second, its control points were adjusted to interpolate computed 3D boundary points. Finally, a 3D surface was generated as an interpolation across the control points of the contours and used in the analysis of the severity of a lesion. To evaluate the method, we compared 3D reconstructed lesions with Optical Coherence Tomography (OCT), an invasive imaging modality that enables high-resolution endoluminal visualization of lesion anatomy.ResultsValidation was performed on routine clinical data. Analysis of paired cross-sectional area discrepancies indicated that the proposed method more closely represented OCT contours than conventional approaches in luminal surface reconstruction, with overall root-mean-square errors ranging from 0.213mm2 to 1.013mm2, and maximum error of 1.837mm2. Comparison of volume reduction due to a lesion with corresponding FFR measurement suggests that the method may help in estimating the physiological significance of a lesion.ConclusionThe algorithm accurately reconstructed 3D models of lesioned arteries and enabled quantitative assessment of stenoses. The proposed method has the potential to allow immediate analysis of the stenoses in clinical practice, thereby providing incremental diagnostic and prognostic information to guide treatments in real time and without the need for invasive techniques.

Two-year vascular responses to drug-eluting stents with biodegradable polymer versus durable polymer: An optical coherence tomography sub-study of the NEXT

BackgroundThis study aimed to compare very late vascular response after stent implantation between everolimus-eluting stent (EES) with a thin, non-adhesive, durable, biocompatible fluorinated polymer and biolimus-eluting stent (BES) with a biodegradable polymer by optical coherence tomography (OCT). Methods and resultsIn the NOBORI-BES Versus XIENCE V/PROMUS-EES Trial (NEXT), a formal OCT substudy investigated 48 patients (27 EES-treated lesions in 23 patients and 28 BES-treated lesions in 25 patients) with 2-year (18–30 months) follow-up imaging at 18 centers. The percentage of uncovered strut by neointima was significantly lower in EES compared with BES (2.1±4.7% vs. 7.9±10.8%, p=0.013). The percentage of malapposed strut was not different between EES and BES (0.1±0.3% vs. 0.5±1.3%, p=0.138). The frequency of stent with evagination, which is identified as outward bulges in the luminal contour between struts, was significantly lower in EES compared with BES (22% vs. 86%, p<0.001). The frequency of neoatherosclerosis was not different between EES and BES (11% vs. 11%, p=1.000). ConclusionsAt 2 years after stent implantation, uncovered stent strut by neointima and evagination were less frequently observed in EES compared with BES. This OCT study suggests that the very late vascular response is different between EES and BES.

Coronary evaginations and peri-scaffold aneurysms following implantation of bioresorbable scaffolds: incidence, outcome, and optical coherence tomography analysis of possible mechanisms.

Peri-stent coronary evaginations may disturb flow and have been proposed as possible risk factor for late stent thrombosis. We describe incidence, predictors, and possible mechanisms of coronary evaginations 12 months after implantation of bioresorbable vascular scaffolds (BVS). One hundred and two BVS implanted in 90 patients (age 63 ± 13 years, 71 males, 14 diabetics) were analysed with angiography and optical coherence tomography (OCT) 12 months after implantation. Evaginations were identified as any hollow in the luminal vessel contour between well-apposed struts and were classified as major when extending ≥3 mm with a depth ≥10% of the BVS diameter. Fifty-five (54%) of the BVS (50(56%) of the patients) had at least one evagination (6.1 ± 6.2 evaginations per BVS), with a mean volume of 1.9 ± 1.9 mm(3). Major evaginations were only found in one patient, and in-BVS aneurysms in three patients (4BVS). The presence of evaginations was strongly associated with that of malapposition (P = 0.003) and strut fractures (P = 0.01). No association could be shown between the presence and volume of the evaginations and any clinical variable or the presence of uncovered struts (P > 0.5). Peri-strut low-intensity areas (PSLIA) were present in 29 (53%) of the BVS with evaginations and 12 (26%) of those without (P = 0.0049); their presence was independently associated with the presence, the number (P < 0.003) and volume of the evaginations (P = 0.004) and with that of strut fracture. Optical coherence tomography-detected evaginations are relatively common after BVS implantation, but, as for modern drug-eluting metallic stents, major evaginations are very rare. Optical coherence tomography evidence of immature neointima and strut fractures were associated with more severe development of evaginations.

Tissue-engineered tracheal reconstruction using mesenchymal stem cells seeded on a porcine cartilage powder scaffold.

Tissue engineering using a biocompatible scaffold with various cells might be a solution for tracheal reconstruction. We investigated the plausibility of using mesenchymal stem cells (MSCs) seeded on a porcine cartilage powder (PCP) scaffold for tracheal defect repair. PCP made with minced and decellularized porcine articular cartilage was molded into a 5 × 12 mm (height × diameter) scaffold. MSCs from young rabbit bone marrow were expanded and cultured with the PCP scaffold. After 7 weeks culture, the tracheal implants were transplanted on a 5 × 10 mm tracheal defect in six rabbits. 6 and 10 weeks postoperatively, the implanted area was evaluated. None of the six rabbits showed any sign of respiratory distress. Endoscopic examination revealed that respiratory epithelium completely covered the regenerated trachea and there were no signs of collapse or blockage. A patent luminal contour of the trachea was observed on the computed tomography scan in all six rabbits and the reconstructed areas were not narrow compared to normal adjacent trachea. Histologic examination showed that neo-cartilage was successfully produced with minimal inflammation or granulation tissue. Ciliary beating frequency of the regenerated epithelium was not significantly different from the normal adjacent mucosa. MSCs cultured with a PCP scaffold successfully restored not only the shape but also the function of the trachea without any graft rejection.

Tracheal reconstruction using chondrocytes seeded on a poly(l-lactic-co-glycolic acid)-fibrin/hyaluronan

Reconstruction of trachea is still a clinical dilemma. Tissue engineering is a recent and promising concept to resolve this problem. This study evaluated the feasibility of allogeneic chondrocytes cultured with fibrin/hyaluronic acid (HA) hydrogel and degradable porous poly(L-lactic-co-glycolic acid) (PLGA) scaffold for partial tracheal reconstruction. Chondrocytes from rabbit articular cartilage were expanded and cultured with fibrin/HA hydrogel and injected into a 5 × 10 mm-sized, curved patch-shape PLGA scaffold. After 4 weeks in vitro culture, the scaffold was implanted on a tracheal defect in eight rabbits. Six and 10 weeks postoperatively, the implanted sites were evaluated by bronchoscope and radiologic and histologic analyses. Ciliary beat frequency (CBF) of regenerated epithelium was also evaluated. None of the eight rabbits showed any sign of respiratory distress. Bronchoscopic examination did not reveal stenosis of the reconstructed trachea and the defects were completely recovered with respiratory epithelium. Computed tomography scan showed good luminal contour of trachea. Histologic data showed that the implanted chondrocytes successfully formed neocartilage with minimal granulation tissue. CBF of regenerated epithelium was similar to that of normal epithelium. Partial tracheal defect was successfully reconstructed anatomically and functionally using allogeneic chondrocytes cultured with PLGA-fibrin/HA composite scaffold.

Flow disturbances in stent-related coronary evaginations: a computational fluid-dynamic simulation study

Angiographic ectasias and aneurysms in stented segments have been associated with late stent thrombosis. Using optical coherence tomography (OCT), some stented segments show coronary evaginations reminiscent of ectasias. The purpose of this study was to explore, using computational fluid-dynamic (CFD) simulations, whether OCT-detected coronary evaginations can induce local changes in blood flow. OCT-detected evaginations are defined as outward bulges in the luminal vessel contour between struts, with the depth of the bulge exceeding the actual strut thickness. Evaginations can be characterised cross-sectionally by depth and along the stented segment by total length. Assuming an ellipsoid shape, we modelled 3-D evaginations with different sizes by varying the depth from 0.2-1.0 mm, and the length from 1-9 mm. For the flow simulation we used average flow velocity data from non-diseased coronary arteries. The change in flow with varying evagination sizes was assessed using a particle tracing test where the particle transit time within the segment with evagination was compared with that of a control vessel. The presence of the evagination caused a delayed particle transit time which increased with the evagination size. The change in flow consisted locally of recirculation within the evagination, as well as flow deceleration due to a larger lumen - seen as a deflection of flow towards the evagination. CFD simulation of 3-D evaginations and blood flow suggests that evaginations affect flow locally, with a flow disturbance that increases with increasing evagination size.

Tissue-engineered tracheal reconstruction using chondrocyte seeded on a porcine cartilage-derived substance scaffold

ObjectivesTracheal reconstruction with tissue-engineering technique has come into the limelight in the realm of head and neck surgery. We intended to evaluate the plausibility of allogenic chondrocytes cultured with porcine cartilage-derived substance (PCS) scaffold for partial tracheal defect reconstruction. MethodsPowder made from crushed and decellularized porcine articular cartilage was formed as 5mm×12mm (height×diameter) scaffold. Chondrocytes from rabbit articular cartilage were expanded and cultured with PCS scaffold. After 7 weeks culture, the scaffolds were implanted on a 5mm×10mm artificial tracheal defect in six rabbits. Two, four and eight weeks postoperatively, the sites were evaluated endoscopically, radiologically, histologically and functionally. ResultsNone of the six rabbits showed any sign of respiratory distress. Endoscopic examination did not show any collapse or blockage of the reconstructed trachea and the defects were completely covered with regenerated respiratory epithelium. Computed tomography showed good luminal contour of trachea. Postoperative histologic data showed that the implanted chondrocyte successfully formed neo-cartilage with minimal inflammatory response and granulation tissue. Ciliary beat frequency of regenerated epithelium was similar to those of normal adjacent mucosa. ConclusionsThe shape and function of reconstructed trachea using allogenic chondrocytes cultured with PCS scaffold was restored successfully without any graft rejection.

Coronary evaginations are associated with positive vessel remodelling and are nearly absent following implantation of newer-generation drug-eluting stents: an optical coherence tomography and intravascular ultrasound study

The purpose of this study was to assess the occurrence, predictors, and mechanisms of optical coherence tomography (OCT)-detected coronary evaginations following drug-eluting stent (DES) implantation. Angiographic ectasias and aneurysms in stented segments have been associated with a risk of late stent thrombosis. Using OCT, some stented segments show coronary evaginations reminiscent of ectasias. Evaginations were defined as outward bulges in the luminal contour between struts. They were considered major evaginations (MEs) when extending ≥3 mm along the vessel length, with a depth ≥10% of the stent diameter. A total of 228 patients who had sirolimus (SES)-, paclitaxel-, biolimus-, everolimus (EES)-, or zotarolimus (ZES)-eluting stents implanted in 254 lesions, were analysed after 1, 2, or 5 years; and serial assessment using OCT and intravascular ultrasound (IVUS) was performed post-intervention and after 1 year in 42 patients. Major evaginations occurred frequently at all time points in SES (∼26%) and were rarely seen in EES (3%) and ZES (2%, P = 0.003). Sirolimus-eluting stent implantation was the strongest independent predictor of ME [adjusted OR (95% CI) 9.1 (1.1-77.4), P = 0.008]. Malapposed and uncovered struts were more common in lesions with vs. without ME (77 vs. 25%, P < 0.001 and 95 vs. 20%, P < 0.001, respectively) as was thrombus [49 vs. 14%, OR 7.3 (95% CI: 1.7-31.2), P = 0.007]. Post-intervention intra-stent dissection and protrusion of the vessel wall into the lumen were associated with an increased risk of evagination at follow-up [OR (95% CI): 2.9 (1.8-4.9), P < 0.001 and 3.3 (1.6-6.9), P = 0.001, respectively]. In paired IVUS analyses, lesions with ME showed a larger increase in the external elastic membrane area (20% area change) compared with lesions without ME (5% area change, P < 0.001). Optical coherence tomography-detected MEs are a specific morphological footprint of early-generation SES and are nearly absent in newer-generation ZES and EES. Evaginations appear to be related to vessel injury at baseline; are associated with positive vessel remodelling; and correlate with uncoverage, malapposition, and thrombus at follow-up.

Compensation of in-plane rigid motion for in vivo intracoronary ultrasound image sequence

Intracoronary ultrasound (ICUS) is an interventional imaging modality that is used to acquire a series of tomographic images from the vascular lumen, for diagnosis and treatment of coronary artery diseases in clinical settings. Motion artifacts caused by cardiac dynamics and the pulsatile blood flow within the vascular lumen, during continuous pullback (non-gated) ICUS image acquisition, hinder visualization of longitudinal cuts, assessment of arterial morphology and hemodynamics, and three-dimensional (3-D) vessel reconstruction. The aim of this study is to develop a method to compensate for in-plane rigid motion in non-gated in vivo ICUS sequences. The signals associated with cardiac motion are first detected from the gray-scale image sequence. They are represented with rigid motion parameters between luminal contours extracted from successive slices. Subsequently, the signals were filtered to separate the dynamic components caused by cardiac motion from those caused by the irregular morphology of the vascular lumen. Dynamic components were then compensated by performing a back transformation of related pixels within the vessel region in each frame. The method is validated by computer-simulation and using real ICUS image data. Possible sources of error are discussed based on the experimental results.

Automatic quantitative analysis of in‐stent restenosis using FD‐OCT in vivo intra‐arterial imaging

A new segmentation technique is implemented for automatic lumen area extraction and stent strut detection in intravascular optical coherence tomography (OCT) images for the purpose of quantitative analysis of in-stent restenosis (ISR). In addition, a user-friendly graphical user interface (GUI) is developed based on the employed algorithm toward clinical use. Four clinical datasets of frequency-domain OCT scans of the human femoral artery were analyzed. First, a segmentation method based on fuzzy C means (FCM) clustering and wavelet transform (WT) was applied toward inner luminal contour extraction. Subsequently, stent strut positions were detected by utilizing metrics derived from the local maxima of the wavelet transform into the FCM membership function. The inner lumen contour and the position of stent strut were extracted with high precision. Compared to manual segmentation by an expert physician, the automatic lumen contour delineation had an average overlap value of 0.917 ± 0.065 for all OCT images included in the study. The strut detection procedure achieved an overall accuracy of 93.80% and successfully identified 9.57 ± 0.5 struts for every OCT image. Processing time was confined to approximately 2.5 s per OCT frame. A new fast and robust automatic segmentation technique combining FCM and WT for lumen border extraction and strut detection in intravascular OCT images was designed and implemented. The proposed algorithm integrated in a GUI represents a step forward toward the employment of automated quantitative analysis of ISR in clinical practice.

Transplantation of Autologous Chondrocytes Seeded on a Fibrin/Hyaluronan Composite Gel Into Tracheal Cartilage Defects in Rabbits: Preliminary Results

Reconstruction of tracheal defects is one of the most difficult procedures in head and neck surgery. To date, various reconstructing techniques have been used with no consensus on the best approach. This study investigated the feasibility of using a fibrin/hyaluronic acid (HA) composite gel with autologous chondrocytes for tracheal reconstruction. Chondrocytes from autologous rabbit auricular cartilages were expanded and seeded into a culture dish at high density to form stable tracheal cartilages mechanically using a fibrin/HA composite gel. A 1-cm long by 0.5-cm wide defect was created by a scalpel on the cervical tracheae of six rabbits. Tissue-engineered cartilages using fibrin/HA composite were trimmed and fixed to the defect boundaries with tissuecol. Postoperatively, the site was evaluated endoscopically, histologically, radiologically, and functionally. None of the six rabbits showed signs of respiratory distress. Postoperatively, in all cases, rigid telescopic examination showed that the implanted scaffolds were completely covered with regenerated mucosa without granulation or stenosis. Histologically, the grafts showed no signs of inflammatory reaction and were covered with ciliated epithelium. Even when grafts were broken and migrated from their original insertion site, the implanted cartilages were well preserved. However, the grafts did show signs of mechanical failure at the implantation site. The beat frequency of ciliated epithelium on implants was very similar to that of normal respiratory mucosa. In conclusion, implants with autologous chondrocytes cultured with fibrin/HA showed good tracheal luminal contour, functional epithelial regeneration, and preservation of neocartilage without inflammation but lacked adequate mechanical stability.

SU-E-I-90: Fast and Robust Algorithm Towards Vessel Lumen and Stent Strut Detection in Optical Coherence Tomography.

Optical Coherence Tomography (OCT) is a catheter-based imaging method that employs near-infrared light to produce high-resolution cross-sectional intravascular images. We propose a new segmentation technique for automatic lumen area extraction and stent strut detection in intravascular OCT images for the purpose of quantitative analysis of neointimal hyperplasia (NIH). Two clinical dataset of frequency-domainOCT scans of the human femoral artery were analyzed. First, a segmentation method based on Fuzzy C-Means (FCM) clustering and Wavelet Transform (WT) was applied towards inner luminal contour extraction. Subsequently, stent strut positions were detected by utilizing metrics derived from the local maxima of the wavelet transform into the FCM membership function. The inner lumen contour and the position of stent strut were extracted with very high accuracy. Compared with manual segmentation by an expert physician, the automatic segmentation had an average overlap value of 0.917 ± 0.065 for all OCT images included in the study. The strut detection procedure successfully identified 6.7 ± 0.5 struts for each OCT image. A new fast and robust automatic segmentation technique combining FCM and WT for lumen border extraction and strut detection in intravascular OCT images was designed and implemented. The proposed algorithm may be employed for automated quantitative morphological analysis of in-stent neointimal hyperplasia.