Reproducibility of qualitative assessment of stent struts coverage by optical coherence tomography

Assessment of stent strut coverage by optical coherence tomography (OCT) is not standardized. The methodology most commonly used is based on a visual binary qualitative assessment (strut covered or not). However, the influence of magnification (zoom setting) to the inter- and intra-observer agreements has not yet been evaluated. Aim of our study was therefore to evaluate the agreements of this approach, taking into account various zoom settings. 126 struts from 10 selected frames were independently evaluated by four observers using a stepwise approach increasing the zoom setting as following: (1) full view of the lumen (FV), (2) half view of the lumen (HV) and (3) a quarter view of the lumen (QV). Intra- and inter-observer agreements (κ) were assessed. The rate of uncoverage was determined for each strut as the number of times it was defined as uncovered divided by the total number of observations (maximum 12 = 3 zoom settings × 4 analysts) and expressed as percentage. The inter-observer κ values (mean [range]) were 0.32 [0.07–0.63], 0.40 [0.18–0.69] and 0.33 [0.09–0.6], within FV, HV and QV respectively. The intra-observer κ values were 0.60 [0.50–0.70], 0.75 [0.75–0.76] and 0.60 [0.50–0.70], within FV, HV and QV respectively. By increasing zoom setting the κ value of intra-observer agreement was 0.74 [0.58–0.83] (from FV to HV), 0.70 [0.56–0.83] (from HV to QV) and 0.70 [0.37–0.86] (from FV to QV). Overall, the rate of uncoverage was 15.5% [8.3–100%]. The OCT qualitative evaluation of strut coverage has wide inter and intra-observer agreements and is dependent of the zoom setting used during the analysis. A more reproducible approach would be needed to eventually increase the probability to link uncovered struts with clinical events.     

Relationship between endothelial vasomotor function and strut coverage after implantation of drug-eluting stent assessed by optical coherence tomography

The use of drug-eluting stent (DES) has been associated with incomplete endothelialization and coronary endothelial dysfunction. However, the relationship between endothelial vasomotor function and strut coverage evaluated by optical coherence tomography (OCT) has not been sufficiently assessed. Therefore, we evaluated the relationship between endothelial vasomotor function and the degree of stent strut coverage after DES implantation. Coronary angiography and OCT were performed in 112 patients at the 6-month follow-up after DES implantation. The patients were divided into tertiles according to the degree of strut coverage as was assessed by OCT. Endothelial vasomotor function was evaluated with intracoronary infusion of incremental doses of acetylcholine (Ach; 10^?8–10^?6 mol/L). Vascular responses at the proximal and distal segments to the stent margin were evaluated by quantitative coronary angiography analysis before and after Ach infusion. The percentage of uncovered struts in tertiles 1–3 was 4.2 ± 3.3, 17.3 ± 4.2 and 44.5 ± 14.4 %, respectively, (p < 0.001). The percentage of maximal vasoconstriction in tertiles 1–3 was 8.3, 9.1 and 8.1 % at proximal segment to the stent margin (p = 0.95), respectively, and 13.9, 11.1 and 14.2 % at distal segment to the stent margin (p = 0.74), respectively. The percentage of uncovered struts was not correlated with the degree of vasomotor function (r = ?0.01, p = 0.92 at the proximal segment; r = ?0.07, p = 0.47 at the distal segment). The percentage of strut coverage was not associated with the degree of abnormal vasoconstriction in response to intracoronary infusion of Ach 6 months after DES implantation.     

Optical coherence tomography endpoints in stent clinical investigations: strut coverage

Late stent thrombosis (LST) and very LST (VLST) are infrequent complications after drug-eluting stent (DES) implantation, but they carry a significant risk for patients. Delayed healing, which may be represented by incomplete stent coverage, has been observed in necropsy vessel specimens treated with DES. As a result, in vivo assessment of stent coverage, as well as stent apposition using optical coherence tomography (OCT), have been recently used as surrogate safety endpoints in clinical trials testing DES platforms. By adopting strut coverage assessed by OCT, one can assess the safety profile of the new generation of DES in preregistration studies. This article focuses on stent strut coverage as a central predictor of late DES thrombosis from the histopathological point of view, discusses the limitations of the current imaging modalities and presents the technical characteristics of OCT for the detection of neointimal coverage after stent implantation. We also review the preclinical and clinical investigations using this novel imaging modality.     

Quantitative comparison of analysis methods for spectroscopic optical coherence tomography

Spectroscopic optical coherence tomography (sOCT) enables the mapping of chromophore concentrations and image contrast enhancement in tissue. Acquisition of depth resolved spectra by sOCT requires analysis methods with optimal spectral/spatial resolution and spectral recovery. In this article, we quantitatively compare the available methods, i.e. the short time Fourier transform (STFT), wavelet transforms, the Wigner-Ville distribution and the dual window method through simulations in tissue-like media. We conclude that all methods suffer from the trade-off in spectral/spatial resolution, and that the STFT is the optimal method for the specific application of the localized quantification of hemoglobin concentration and oxygen saturation.OCIS codes: (030.1640) Coherence, (070.4790) Spectrum analysis, (160.4760) Optical properties, (170.6510) Spectroscopy, tissue diagnostics     

Assessment of coronary stent by optical coherence tomography,methodology and definitions

Optical coherence tomography has emerged as a powerful tool for stent assessment, and in a short time, has become the modality of choice for studying stent and vascular interactions in vivo. In this review, we discuss qualitative and quantitative parameters used for stent assessment by OCT. Various qualitative/quantitative variables of stent assessment are discussed in the perspective of the clinical and research values of each of them.     

Predictors of acute scaffold recoil after implantation of the everolimus-eluting bioresorbable scaffold: an optical coherence tomography assessment in native coronary arteries

This study investigated the predictors of acute recoil after implantation of everolimus-eluting BRS based on optical coherence tomography (OCT). Thirty-nine patients (56 scaffolds) were enrolled. Acute absolute recoil by quantitative coronary angiography was defined as the difference between the mean diameter of the last inflated balloon (X) and the mean lumen diameter of BRS immediately after balloon deflation (Y). Acute percent recoil was defined as (X???Y)?×?100/X. Plaque eccentricity (PE) and plaque composition (PC) were assessed by OCT. PC was classified into two different types: calcific (score?=?1), fibrous and lipid (score?=?0). Based on the mean acute scaffold recoil value of the present study, scaffolds were divided into two groups: the low acute recoil group (LAR, n?=?34) and the high acute recoil group (HAR, n?=?22). Acute percent and absolute recoil were 6.4?±?3.0?% and 0.19?±?0.11 mm. PE, PC score and scaffold/artery ratio were significantly higher in HAR than in LAR. In multivariate logistic regression analysis, PE?>?1.49, PC score (score 1) and scaffold/artery ratio >1.07 were significant positive predictors for the occurrence of acute scaffold recoil (OR 10.7, 95?% CI 2.2–51.4, p?<?0.01; OR 5.6, 95?% CI 1.9–22.0, p?=?0.04; OR 12.4, 95?% CI 2.6–65.4, p?<?0.01, respectively). Acute recoil of BRS is influenced by BRS sizing as well as OCT-derived plaque characteristics.     

Major determinants for the uncovered stent struts on optical coherence tomography after drug-eluting stent implantation

There have been little data regarding major determinants for the uncovered stent struts after drug-eluting stent (DES) implantation on optical coherence tomography (OCT). We investigated the major determinants of incomplete neointimal coverage of DES struts on OCT after implantation in a large cohort of patients. A total of 261 patients with 279 lesions who were treated with various DESs were selected from the OCT registry database. The lesions were divided into two groups based on the ratio of uncovered struts to total struts in all OCT cross-sections; an uncovered group (highest quartile with % uncovered struts ≥5.4%, n?=?70), and covered group (the remaining lower quartiles with % uncovered struts <5.4%, n?=?209). The uncovered group was more likely to have complex lesions, smaller reference vessel and stent diameter, and longer stent, more use of sirolimus-eluting stents, and less use of zotarolimus-eluting stents compared with the covered group. Of these variables, the most significant determinant of uncovered stent struts was DES type (odds ratio [OR]?=?2.75, 95% confidence interval [CI]?=?1.94–3.89, P?<?0.001). The use of sirolimus-eluting stents (OR?=?2.44, 95% CI, 1.15–5.47, P?=?0.023) and zotarolimus-eluting stents (OR?=?0.02, 95% CI?=?0.01–0.25, P?=?0.002) were the only significant risk and protective factors for uncovered stent struts, respectively. This study demonstrated that DES type might be associated with the most important determinants of uncovered struts compared to any other clinical or angiographic factor.     

Quantitative analysis of early diabetic retinopathy based on optical coherence tomography angiography biological image

BACKGROUNDWith the development of the economy and improvements in living standards, the incidences of diabetes mellitus (DM) and diabetic retinopathy (DR), which is a complication of DM, are on the rise.AIMTo analyze early DR in patients with macular zone changes in biological images using optical coherence tomography angiography METHODSA prospective case study was performed on 59 participants: 35 healthy eyes (control group), 35 eyes with diabetes but no DR group (no DR group), and 35 eyes with mild DR (NPDR group). All quantitative comparisons of parameters, including the fovea vascularity area, circularity index, and vascular complexity parameters, were performed using a biological image analysis software.RESULTSThe foveal avascular zone (FAZ) area, FAZ circularity index, number of branches in the area, and the total of the single branches’ length in the area was 0.366 ± 0.031, 0.834 ± 0.037, 3241.8 ± 268.3, and 3.860 × 10⁷ ± 0.194 × 10⁷, and 0.421 ± 0.030, 0.739 ± 0.023, 2956.6 ± 476.4, and 3.177 × 10⁷ ± 0.161 × 10⁷ in the no DR group and the NPDR group, respectively, which were significantly different from the corresponding parameters of the control group (P < 0.05). Moreover, there were significant differences between these two groups (P < 0.05).CONCLUSIONThis study shows that early microcirculation changes in the macular area of the retina is associated with disease progression. Early changes in DR can be analyzed using optical coherence tomography angiography.     

Quantitative comparison of analysis methods for spectroscopic optical coherence tomography: reply to comment

We reply to the comment by Kraszewski et al on “Quantitative comparison of analysis methods for spectroscopic optical coherence tomography.” We present additional simulations evaluating the proposed window function. We conclude that our simulations show good qualitative agreement with the results of Kraszewski, in support of their conclusion that SOCT optimization should include window shape, next to choice of window size and analysis algorithm.OCIS codes: (030.1640) Coherence, (070.4790) Spectrum analysis, (160.4760) Optical properties, (170.6510) Spectroscopy, tissue diagnostics     

Quantitative upper airway endoscopy with swept-source anatomical optical coherence tomography

Minimally invasive imaging of upper airway obstructions in children and adults is needed to improve clinical decision-making. Toward this goal, we demonstrate an anatomical optical coherence tomography (aOCT) system delivered via a small-bore, flexible endoscope to quantify the upper airway lumen geometry. Helical scans were obtained from a proximally-scanned fiber-optic catheter of 820 μm outer diameter and >2 mm focal length. Coupled with a long coherence length wavelength-swept light source, the system exhibited an SNR roll-off of < 10 dB over a 10 mm range. Operating at 10 rotations/s, the average accuracy of segmented cross-sectional areas was found to be −1.4 ± 1.0%. To demonstrate the capability of this system, aOCT was performed on a pediatric airway phantom and on ex vivo swine trachea. The ability for quantitative endoscopy afforded by this system can aid in diagnosis, medical and surgical decision making, and predictive modeling of upper airway obstructive disorders.OCIS codes: (170.4500) Optical coherence tomography, (170.3880) Medical and biological imaging, (170.3890) Medical optics instrumentation, (170.2150) Endoscopic imaging     

Very long-term follow-up of strut apposition and tissue coverage with Biolimus A9 stents analyzed by optical coherence tomography

First generation drug-eluting stents (DES) are associated with reduced in-stent restenosis but significant increased risk of very late stent thrombosis (VLST). The absence of polymer in DES systems may reduce the occurrence of VLST. Optic coherence tomography (OCT) has been used for stent analysis as a surrogate safety endpoint. This study aimed to assess the long-term follow up of strut apposition and tissue coverage of BioMatrix? DES by OCT. 20 patients undergoing BioMatrix? DES (n = 15) or S-Stent? BMS (n = 5) implantation were followed for at least 5 years and evaluated by quantitative coronary angiography, intravascular ultrasound, and OCT. The difference between the stent types was evaluated by nonparametric Mann–Whitney U test while categorical variables were evaluated by Fisher exact test. Rates of in-stent late loss were similar between groups [0.40 (0.21;0.77) vs. 0.68 (0.66; 0.82) mm, p = 0.205, for BioMatrix? and S-Stent?, respectively]. The vessel, stent and lumen volumes did not differ between groups. Patients treated with BioMatrix? had significantly less stent obstruction [5.6 (4.4;9.7) vs. 28.6 (24.7;29.0) %, p = 0.001]. OCT analysis of 12 stents (Biomatrix? = 9 and S-Stent? = 3) demonstrated 126 (8.7 %) uncovered struts in the BioMatrix? group compared to 23 (4.0 %) in the S-Stent? group (p = 0.297), being the majority of them well apposed (117/126 and 21/23, respectively, p = 0.292). Only 9 (0.6 %) struts in the DES and 2 (0.4 %) struts in the BMS groups were simultaneously uncovered and malapposed (p = 0.924). BioMatrix? DES was associated with lower rates of in-stent obstruction, and similar percentage of neointimal coverage on struts and of complete strut apposition.     

Retinal optical coherence tomography image analysis by a restricted Boltzmann machine

Optical coherence tomography (OCT) is an emerging imaging technique for ophthalmic disease diagnosis. Two major problems in OCT image analysis are image enhancement and image segmentation. Deep learning methods have achieved excellent performance in image analysis. However, most of the deep learning-based image analysis models are supervised learning-based approaches and need a high volume of training data (e.g., reference clean images for image enhancement and accurate annotated images for segmentation). Moreover, acquiring reference clean images for OCT image enhancement and accurate annotation of the high volume of OCT images for segmentation is hard. So, it is difficult to extend these deep learning methods to the OCT image analysis. We propose an unsupervised learning-based approach for OCT image enhancement and abnormality segmentation, where the model can be trained without reference images. The image is reconstructed by Restricted Boltzmann Machine (RBM) by defining a target function and minimizing it. For OCT image enhancement, each image is independently learned by the RBM network and is eventually reconstructed. In the reconstruction phase, we use the ReLu function instead of the Sigmoid function. Reconstruction of images given by the RBM network leads to improved image contrast in comparison to other competitive methods in terms of contrast to noise ratio (CNR). For anomaly detection, hyper-reflective foci (HF) as one of the first signs in retinal OCTs of patients with diabetic macular edema (DME) are identified based on image reconstruction by RBM and post-processing by removing the HFs candidates outside the area between the first and the last retinal layers. Our anomaly detection method achieves a high ability to detect abnormalities.     

Automatic detection of bioresorbable vascular scaffold struts in intravascular optical coherence tomography pullback runs

Bioresorbable vascular scaffolds (BVS) have gained significant interest in both the technical and clinical communities as a possible alternative to metallic stents. For accurate BVS analysis, intravascular optical coherence tomography (IVOCT) is currently the most suitable imaging technique due to its high resolution and the translucency of polymeric BVS struts for near infrared light. However, given the large number of struts in an IVOCT pullback run, quantitative analysis is only feasible when struts are detected automatically. In this paper, we present an automated method to detect and measure BVS struts based on their black cores in IVOCT images. Validated using 3 baseline and 3 follow-up data sets, the method detected 93.7% of 4691 BVS struts correctly with 1.8% false positives. In total, the Dice’s coefficient for BVS strut areas was 0.84. It concludes that this method can detect BVS struts accurately and robustly for tissue coverage measurement, malapposition detection, strut distribution analysis or 3D scaffold reconstruction.OCIS codes: (100.6950) Tomographic image processing, (110.4500) Optical coherence tomography     

Differences between first-generation and second-generation drug-eluting stent regarding in-stent neoatherosclerosis characteristics: an optical coherence tomography analysis

We compared first-generation and second-generation drug-eluting stent (DES) with respect to neoatherosclerosis using optical coherence tomography or optical frequency domain imaging. In-stent restenoses in 102 first-generation and 114 second-generation DES were retrospectively assessed. Neoatherosclerosis, which was defined as the presence of lipid-laden neointima or calcification inside a stent, was observed in 33 (27.2%) and 31 (32.4%) lesions in the first-generation and second-generation DES respectively. In the first-generation DES group, the lipid length was significantly longer (5.5?±?3.8 vs. 3.1?±?2.1 mm, P?=?0.0007), the lipid arc was significantly larger (324?±?70° vs. 250?±?94°, P?=?0.002), the prevalence of a 360° lipid arc was significantly greater (58 vs. 31%, P?=?0.03), and the fibrous cap was significantly thinner (153?±?85 vs. 211?±?95 µm, P?=?0.02) compared with those in the second-generation DES group. These differences remained significant after adjusting for the age of the stent (lipid length: P?<?0.001; lipid arc: P?=?0.019; and fibrous cap thickness: P?<?0.001). The proliferation course and stability of neoatherosclerosis over time might be superior in second-generation DES.     

Quantitative analysis of vascular changes during photoimmunotherapy using speckle variance optical coherence tomography (SV-OCT)

Near-infrared (NIR) photoimmunotherapy (NIR-PIT) is an emerging cancer therapy based on a monoclonal antibody and phthalocyanine dye conjugate. Direct tumor necrosis and immunogenic cell death occur during NIR irradiation. However, the alteration of tumor blood vessels and blood volume inside the blood vessels induced by the NIR-PIT process is still unknown. In our study, a speckle variance (SV) algorithm combined with optical coherence tomography (OCT) technology was applied to monitor the change of blood vessels and the alterations of the blood volume inside the blood vessels during and after NIR-PIT treatment. Vascular density and the measurable diameter of the lumen in the blood vessel (the diameter of the region filled with blood) were extracted for quantitively uncovering the alterations of blood vessels and blood volume induced by NIR-PIT treatment. The results indicate that both the density and the diameter of the lumen in the blood vessels decrease during the NIR-PIT process, while histological results indicated the blood vessels were dilated. The increase of permeability of blood vessels could lead to the increase of the blood pool volume within the tumor (shown in histology) and results in the decrease of free-moving red blood cells inside the blood vessels (shown in SV-OCT).     

Detection of myocardial bridge by optical coherence tomography

The International Journal of Cardiovascular Imaging - Myocardial bridge (MB) is less commonly documented by angiography than autopsy. Optical coherence tomography (OCT) may be useful to detect...