Classification of arterial plaque by spectral analysis of in vitro radio frequency intravascular ultrasound data

To test whether radio-frequency analysis of coronary plaques predicts the histological classification, r.f. data were collected using a 30 MHz intravascular ultrasound scanner. Two hundred ninety-nine regions-of-interest from eight postmortem coronary arteries were selected and identified by histology as falling into one of seven different tissue types. These are loose fibrous tissue (n = 78), moderate fibrous tissue (n = 27), dense fibrous tissue (n = 33), microcalcification (n = 14), calcified plaque (n = 55), lipid/fibrous mixture (n = 51) and homogeneous areas of lipid pool (n = 29). On the basis of a previous study, four spectral parameters were calculated for each of the regions-of-interest: maximum power (dB), mean power (dB), spectral slope (dB/MHz) over the bandwidth 18-35 MHz and the intercept of the spectral slope with the 0 Hz axis (dB). A minimum-distance classifier using the Mahalanobis (1948) distance was applied to the data. Following resubstitution of the training data into the classifier, the total correctly classified was 54%. The data were reclassified using three broader tissue groups: (1) calcified plaque, (2) lipid pool and (3) a mixed fibrous category, incorporating loose fibrous tissue, moderate fibrous tissue, dense fibrous tissue, lipid/fibrous mixture and microcalcification. The total correctly classified was 86%. Using "leave-one-out" cross-validation, the classification rates were 48% for seven tissue subgroups and 83% for three broader categories of tissue type.     

编织冠状动脉的血管内超声及光学相干断层显像影像特点

目的:总结编织冠状动脉(WCA)的血管内超声(IVUS)及光学相干断层显像(OCT)影像特点。方法:选取2013年1月至2020年7月于成都中医药大学附属医院、复旦大学附属中山医院、郑州市心血管病医院就诊,且冠状动脉造影疑诊WCA的患者37例,进行腔内影像学分析,总结确诊为WCA患者的IVUS及OCT特点。结果:37例...     

Comparison of longitudinal geometric measurement in human coronary arteries between frequency-domain optical coherence tomography and intravascular ultrasound

Previous studies have demonstrated the higher accuracy of frequency-domain optical coherence tomography (FD-OCT) for quantitative measurements in comparison with intravascular ultrasound (IVUS). However, those analyses were based on the cross-sectional images. The aim of this study was to assess the accuracy of FD-OCT for longitudinal geometric measurements of coronary arteries in comparison with IVUS. Between October 2011 and March 2012, we performed prospective FD-OCT and IVUS examinations in consecutive 77 patients who underwent percutaneous coronary intervention with single stent. Regression analysis and Bland–Altman analysis revealed an excellent correlation between the FD-OCT-measured stent lengths and IVUS-measured stent lengths (r = 0.986, p < 0.001; mean difference = ?0.51 mm). There was an excellent agreement between the actual stent lengths and the FD-OCT-measured stent lengths (r = 0.993, p < 0.001) as well as between the actual stent lengths and the IVUS-measured stent lengths (r = 0.981, p < 0.001). The difference between the actual stent lengths and the FD-OCT-measured stent lengths was significantly smaller than that between the actual stent lengths and the IVUS-measured stent lengths (0.15 ± 0.68 vs. 0.70 ± 1.15 mm, p < 0.001). Both FD-OCT (mean difference = ?0.04 and ?0.04 mm, respectively) and IVUS (mean difference = ?0.06 and ?0.06 mm, respectively) showed an excellent intra-observer and inter-observer reproducibility for the stent length measurements. In conclusion, FD-OCT provides accurate longitudinal measurement with excellent intra-observer and inter-observer reproducibility. FD-OCT might be a reliable technique for longitudinal geometric measurement in human coronary arteries.     

Fusing in-vitro and in-vivo intravascular ultrasound data for plaque characterization

Accurate detection of in-vivo vulnerable plaque in coronary arteries is still an open problem. Recent studies show that it is highly related to tissue structure and composition. Intravascular Ultrasound (IVUS) is a powerful imaging technique that gives a detailed cross-sectional image of the vessel, allowing to explore arteries morphology. IVUS data validation is usually performed by comparing post-mortem (in-vitro) IVUS data and corresponding histological analysis of the tissue. The main drawback of this method is the few number of available case studies and validated data due to the complex procedure of histological analysis of the tissue. On the other hand, IVUS data from in-vivo cases is easy to obtain but it can not be histologically validated. In this work, we propose to enhance the in-vitro training data set by selectively including examples from in-vivo plaques. For this purpose, a Sequential Floating Forward Selection method is reformulated in the context of plaque characterization. The enhanced classifier performance is validated on in-vitro data set, yielding an overall accuracy of 91.59% in discriminating among fibrotic, lipidic and calcified plaques, while reducing the gap between in-vivo and in-vitro data analysis. Experimental results suggest that the obtained classifier could be properly applied on in-vivo plaque characterization and also demonstrate that the common hypothesis of assuming the difference between in-vivo and in-vitro as negligible is incorrect.     

Development of integrated backscatter intravascular ultrasound for tissue characterization of coronary plaques

Tissue characterization of plaques of coronary arteries is important to clarify the process of acute coronary syndrome and prevent it. The purpose of this study is to develop an online integrated backscatter intravascular ultrasound (IB-IVUS) system and validate the diagnostic accuracy for the characterization of coronary plaques. A personal computer equipped with custom software was connected to an IVUS imaging system. Images were acquired from 242 segments of 46 coronary arteries from 25 cadavers obtained at autopsy. In the training study, a total of 724 regions-of-interests on color-coded maps were compared with histologic images. In the validation study, a total of 192 cross-sections of coronary arteries were evaluated. Receiver operating characteristic curve analysis showed that the cut-off points of -49 dB (area under curve = 0.98) and -29 dB (area under curve = 0.99) were the most reliable predictors of lipid pools, fibrosis and calcification. In the validation study, the analysis using IB values classified fibrous, lipid-rich and fibrocalcific plaque components with a high accuracy of 93%, 90% and 96%, respectively. The overall agreement between histologic and IB-IVUS diagnoses (n = 175) was high (Cohen's kappa = 0.81). The IB-IVUS system provides high diagnostic accuracy for analysis of tissue characteristics of coronary plaques.     

Currently available methodologies for the processing of intravascular ultrasound and optical coherence tomography images

Optical coherence tomography and intravascular ultrasound are the most widely used methodologies in clinical practice as they provide high resolution cross-sectional images that allow comprehensive visualization of the lumen and plaque morphology. Several methods have been developed in recent years to process the output of these imaging modalities, which allow fast, reliable and reproducible detection of the luminal borders and characterization of plaque composition. These methods have proven useful in the study of the atherosclerotic process as they have facilitated analysis of a vast amount of data. This review presents currently available intravascular ultrasound and optical coherence tomography processing methodologies for segmenting and characterizing the plaque area, highlighting their advantages and disadvantages, and discusses the future trends in intravascular imaging.     

Unrestricted utilization of frequency domain optical coherence tomography in coronary interventions

Frequency domain optical coherence tomography (FD-OCT) has shown promise to evaluate coronary devices in clinical trials, however, little is known about its application in clinical practice. This prospective, single center initiative planned for 100 % FD-OCT utilization in all patients undergoing coronary interventions during a 60-day period. Operators pre-specified the planned intervention based on angiography alone. FD-OCT success was defined as acquisition of good quality images enabling adequate quantification of vessel dimensions and lesion/percutaneous coronary intervention (PCI) assessment. Impact on management occurred when angiography-based planning was altered based on FD-OCT data. There were 297 FD-OCT acquisitions performed in 155 vessels from 150 patients. There were no FD-OCT procedural related cardiac adverse events and success was obtained in 85.7 % of all target vessels (pre-PCI = 76.8 % vs. post-PCI = 90.1 %, p = 0.004). Success on the first pullback occurred in 80.3 % overall (61.9 % in the initial operator experience and 85.5 % after the third procedure). FD-OCT impact on management was 81.8 % pre-PCI and 54.8 % post-PCI. Stent malapposition was detected in 39.2 % (89.4 % underwent further intervention) and edge dissection in 32.5 % (21.1 % treated with stent). FD-OCT success and management impact were similar in ACS and non-ACS patients (82.1 vs. 81.1 %, p = 1.000, and 62.5 vs. 65.1 %, p = 0.854, respectively). FD-OCT is safe, can successfully be incorporated into routine practice, and alters procedural strategy in a high proportion of patients undergoing PCI.     

In vivo detection of plaque erosion by intravascular optical coherence tomography using artificial intelligence

Plaque erosion is one of the most common underlying mechanisms for acute coronary syndrome (ACS). Optical coherence tomography (OCT) allows in vivo diagnosis of plaque erosion. However, challenge remains due to high inter- and intra-observer variability. We developed an artificial intelligence method based on deep learning for fully automated detection of plaque erosion in vivo, which achieved a recall of 0.800 ± 0.175, a precision of 0.734 ± 0.254, and an area under the precision-recall curve (AUC) of 0.707. Our proposed method is in good agreement with physicians, and can help improve the clinical diagnosis of plaque erosion and develop individualized treatment strategies for optimal management of ACS patients.     

Integrated optical coherence tomography, ultrasound and photoacoustic imaging for ovarian tissue characterization

Ovarian cancer has the lowest survival rate of the gynecologic cancers because it is predominantly diagnosed in Stages III or IV due to the lack of reliable symptoms, as well as the lack of efficacious screening techniques. Detection before the malignancy spreads or at the early stage would greatly improve the survival and benefit patient health. In this report, we present an integrated optical coherence tomography (OCT), ultrasound (US) and photoacoustic imaging (PAI) prototype endoscopy system for ovarian tissue characterization. The overall diameter of the prototype endoscope is 5 mm which is suitable for insertion through a standard 5-12.5mm endoscopic laparoscopic port during minimally invasive surgery. It consists of a ball-lensed OCT sample arm probe, a multimode fiber having the output end polished at 45 degree angle so as to deliver the light perpendicularly for PAI, and a high frequency ultrasound transducer with 35MHz center frequency. System characterizations of OCT, US and PAI are presented. In addition, results obtained from ex vivo porcine and human ovarian tissues are presented. The optical absorption contrast provided by PAI, the high resolution subsurface morphology provided by OCT, and the deeper tissue structure imaged by US demonstrate the synergy of the combined endoscopy and the superior performance of this hybrid device over each modality alone in ovarian tissue characterization.     

Multi-spectral intravascular photoacoustic/ultrasound/optical coherence tomography tri-modality system with a fully-integrated 0.9-mm full field-of-view catheter for plaque vulnerability imaging

Myocardial infarctions are most often caused by the so-called vulnerable plaques, usually featured as non-obstructive lesions with a lipid-rich necrotic core, thin-cap fibroatheroma, and large plaque size. The identification and quantification of these characteristics are the keys to evaluate plaque vulnerability. However, single modality intravascular methods, such as intravascular ultrasound, optical coherence tomography and photoacoustic, can hardly achieve all the comprehensive information to satisfy clinical needs. In this paper, for the first time, we developed a novel multi-spectral intravascular tri-modality (MS-IVTM) imaging system, which can perform 360° continuous rotation and pull-backing with a 0.9-mm miniature catheter and achieve simultaneous acquisition of both morphological characteristics and pathological compositions. Intravascular tri-modality imaging demonstrates the ability of our MS-IVTM system to provide macroscopic and microscopic structural information of the vessel wall, with identity and quantification of lipids with multi-wavelength excitation. This study offers clinicians and researchers a novel imaging tool to facilitate the accurate diagnosis of vulnerable atherosclerotic plaques. It also has the potential of clinical translations to help better identify and evaluate high-risk plaques during coronary interventions.     

In vivo volumetric analysis of coronary stent using optical coherence tomography with a novel balloon occlusion-flushing catheter: a comparison with intravascular ultrasound

Optical coherence tomography (OCT) is limited as an intravascular imaging tool because of interference with blood. This study tested a new balloon occlusion-flushing catheter for OCT scanning of stented coronary arteries and compared stent measurements between OCT and intravascular ultrasound (IVUS). Motorized pullback with OCT and IVUS was examined in coronary stents deployed in swine. Quantitative measurements were obtained and compared between both groups. In addition, stent strut thickness was compared among OCT, IVUS and actual measurement. The occlusion catheter successfully provided motorized pullback OCT images in the stented coronary arteries without any complications. There were no differences in calculated lumen volume. However, stent volumes were significantly smaller with OCT than with IVUS (p < 0.05). OCT significantly underestimated the stent strut thickness compared with the actual measurement. Although OCT underestimates the stent strut thickness, motorized pullback OCT imaging with the occlusion catheter can provide appropriate in-stent images in the porcine coronary arteries.     

Method for parametric imaging of attenuation by intravascular optical coherence tomography

Catheter-based intravascular optical coherence tomography (IVOCT) is a powerful imaging modality for visualization of atherosclerosis with high resolution. Quantitative characterization of various tissue types by attenuation coefficient (AC) extraction has been proven to be a potentially significant application of OCT attenuation imaging. However, existing methods for AC extraction from OCT suffer from the challenge of variability in complex tissue types in IVOCT pullback data such as healthy vessel wall, mixed atherosclerotic plaques, plaques with a single component and stent struts, etc. This challenge leads to the ineffectiveness in the tissue differentiation by AC representation based on single scattering model of OCT signal. In this paper, we propose a novel method based on multiple scattering model for parametric imaging of optical attenuation by AC retrieval from IVOCT images conventionally acquired during cardiac catheterization. The OCT signal characterized by the AC is physically modeled by Monte Carlo simulation. Then, the pixel-wise AC retrieval is achieved by iteratively minimizing an error function regarding the modeled and measured backscattered signal. This method provides a general scheme for AC extraction from IVOCT without the premise of complete attenuation of the incident light through the imaging depths. Results of computer-simulated and clinical images demonstrate that the method can avoid overestimation at the end of the depth profile in comparison with the approaches based on the depth-resolved (DR) model. The energy error depth and structural similarity are improved by about 30% and 10% respectively compared with DR. It provides a useful way to differentiate and characterize arterial tissue types in IVOCT images.     

Quantified coronary frequency domain optical coherence tomography signal analysis for the evaluation of erythrocyte-rich thrombus: ex-vivo validation study

Previous study has demonstrated that erythrocyte-rich thrombi contain more inflammatory cells and reflect high thrombus burden, leading to impaired myocardial reperfusion in myocardial infarction. The aim of this study is to investigate the utility of quantified frequency domain optical coherence tomography (FD-OCT) signal analysis in evaluating the erythrocyte-rich thrombus with ex-vivo materials. We evaluated 54 specimens of coronary artery thrombus obtained by thrombectomy catheter from 8 patients who underwent primary percutaneous coronary intervention. The thrombi were immersed in saline immediately after thrombectomy and FD-OCT image acquisition was performed ex-vivo. Quantitative analysis for all contiguous frames was performed by the dedicated automated software (OCT system software, Light Lab Inc.). For the maximum thrombus area, mean signal intensity (MSI) and normalized standard deviation of signal (NSD) was evaluated. All thrombi were stained using double staining of phosphotungstic acid—hematoxylin and eosin to enable automatic extraction of erythrocyte from fibrin. Computer-assisted analysis was performed using dedicated image processing software (WinROOF, Mitani Corp., Tokyo, Japan) for color identification of the erythrocyte area. Erythrocyte-rich thrombus, defined as % erythrocyte [(erythrocyte area/total thrombus area)?×?100]?≥?10%, showed significantly lower MSI [4.39?±?0.24 vs. 4.74?±?0.35, p?=?0.002] than that of <10%. The cut-off point for prediction of erythrocyte-rich thrombus was defined as MSI?≤?4.56, sensitivity: 87.5%, specificity: 82.9%, area under the curve: 0.836, respectively). The present ex-vivo study suggested the utility of quantified FD-OCT signal analysis on the detection of erythrocyte-rich thrombus.     

The potential of RF backscattered IVUS data and multidetector-row computed tomography images for tissue characterization of human coronary atherosclerotic plaques

The aim is to compare virtual histology which uses spectral analysis of backscattered intravascular ultrasound (VH–IVUS) and multidetector-row computed tomography (MDCT) for the characterization of coronary atherosclerotic plaques obtained by directional coronary atherectomy (DCA). We performed DCA in 15 de novo native coronary stenotic lesions (15 patients) and selected one or two segments within the plaque from each patient (total 29 segments). Then, we evaluated the accuracy of the VH–IVUS findings in 50 sites among the 29 segments compared with the histopathology findings. MDCT was performed in all patients before percutanous coronary intervention (PCI), and CT density values were measured. VH–IVUS data analysis correlated well with histopathological examination (predictive accuracy: 66.7% for fibrous, 100% for fibro-fatty, 100% for necrotic core, and 100% for dense calcium regions, respectively). In addition, CT density values between fibrous and fibro-fatty plaques classified by histopathology were 100.0 ± 26.0 HU versus 110.4 ± 67.9 HU, there were no difference among them (P = 0.594). These findings indicated that the validation of plaque characteristics using VH–IVUS correlates well with histopathology. While tissue characterization using CT density could be difficult to distinguish between fibro-fatty and fibrous tissue.     

Assessment of vulnerable plaque and vulnerable patient by optical coherence tomography

Optical coherence tomography (OCT) is an intravascular imaging modality, which provides high resolution images up to 10-20 microm. This feature of OCT allows the visualization of specific components of the atherosclerotic plaques in vivo, similar to the histological examinations in vitro. OCT has made a great contribution to the investigation of the pathophysiology of acute coronary syndrome (ACS) in vivo. Furthermore, OCT has a potential not only to detect vulnerable plaques but also to identify vulnerable patients, and may enable us to predict and prevent ACS in the near future.     

光学相干断层成像指导血管内冲击波钙化碎裂术治疗冠状动脉重度钙化病变的有效性和安全性

目的 探讨在光学相干断层成像（optical coherence tomography, OCT）指导下，冲击波钙化碎裂术（intravascular lithotripsy, IVL）治疗冠状动脉重度钙化病变的有效性和安全性。方法 选择2022年8月至2023年3月江南大学附属医院收治的20例冠状动脉重度钙化患者，在OCT指导下应用冠状动脉内冲击波导管对钙化病变进行预处理，随后植入药物洗脱支架（drug-eluting stent, DES）。比较IVL治疗前、IVL治疗后、支架植入后OCT相关参数，包括钙化病变的长度、角度和厚度，最小管腔面积、最小管腔直径、支架膨胀系数、钙化断裂数、支架膨胀率、斑块光衰指数（index of plaque attenuation, IPA）、虚拟血流储备分数（virtual fractional flow reserve, VFR）等。记录患者围手术期发生的主要不良心血管事件（major adverse cardiovascular events, MACEs）。结果 20例患者中，男性12例、女性8例；平均年龄（65.3±9.69）岁。与IVL前相比，最严重钙化病变处的最小管腔直径在IVL后显著扩大[（2.45±0.37）mm vs（2.64±0.33）mm, P＜ 0.05]，最小管腔面积在IVL后显著增加[（3.78±0.81）mm² vs （5.22±1.45）mm²，P＜0.05]；钙化角度在IVL后显著减小[（324.5±94.2）° vs（284.3±79.4）°，P＜0.001]，钙化厚度和长度无明显变化。100%的病变发生钙化断裂，85%的病变发生≥2个钙化断裂；支架植入成功率100%，支架膨胀率（97.10±5.28）%。最严重钙化处支架植入后IPA＜110，VFR＞0.8。所有患者围手术期未发生MACEs。结论 OCT指导下，采用IVL预处理重度冠状动脉钙化病变并植入支架是安全有效的。     

Coronary plaque composition as assessed by greyscale intravascular ultrasound and radiofrequency spectral data analysis

Objectives (i) To explore the relation between greyscale intravascular ultrasound (IVUS) plaque qualitative classification and IVUS radiofrequency data (RFD) analysis tissue types; (ii) to evaluate if plaque composition as assessed by RFD analysis can be predicted by visual assessment of greyscale IVUS images. Methods In 120 IVUS-RFD cross-sections, a sector of the plaque with homogenous tissue composition (e.g., fibrous, fibrofatty, necrotic core, and dense calcium) was selected. Two experienced observers analyzed twice the corresponding greyscale IVUS images to: (1) classify the selected sectors according to greyscale IVUS plaque type classification and (2) predict the tissue type expected in the sector by RFD analysis. Results In the greyscale IVUS plaque type classification, the observers agreed in 90/120 sectors (κ = 0.64). Calcified, soft and mixed plaques by greyscale IVUS classification were mainly composed of dense calcium, fibrofatty, and necrotic core, respectively, in the RFD analysis. The plaques classified in greyscale IVUS as fibrous were actually fibrous tissue by IVUS RFD in only 30% of the cases. Overall, high interobserver variability in the prediction of RFD results by visual assessment of greyscale IVUS images (κ = 0.23 for observer 1 and 0.55 for observer 2) was found. Sensitivities for detection of calcified tissue and NC by greyscale IVUS visual assessment were 88% and 58%, respectively. Conclusions High interobserver variability in the prediction of tissue type by visual assessment of greyscale IVUS images was observed. This underlines the need of quantitative methods for the analysis of the ultrasound characteristics of coronary plaque components.