Intravascular Ultrasound Cross Sections Research Articles

Development and Validation of Artificial Intelligence-Based Algorithms for Predicting the Segments Debulked by Rotational Atherectomy Using Intravascular Ultrasound Images

We develop and evaluate an artificial intelligence-based algorithm that uses pre-rotation atherectomy (RA) intravascular ultrasound (IVUS) images to automatically predict regions debulked by RA. A total of 2106 IVUS cross-sections from 60 patients with de novo severely calcified coronary lesions who underwent IVUS-guided RA were consecutively collected. The two identical IVUS images of pre- and post-RA were merged, and the orientations of the debulked segments identified in the merged images were marked on the outer circle of each IVUS image. The artificial intelligence model was developed based on ResNet (deep residual learning for image recognition). The architecture connected 36 fully connected layers, each corresponding to one of the 36 orientations segmented every 10°, to a single feature extractor. In each cross-sectional analysis, our artificial intelligence model achieved an average sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 81%, 72%, 46%, 90%, and 75%, respectively. In conclusion, the artificial intelligence-based algorithm can use information from pre-RA IVUS images to accurately predict regions debulked by RA and will assist interventional cardiologists in determining the treatment strategies for severely calcified coronary lesions.

Plaque burden estimated from optical coherence tomography with deep learning: In vivo validation using co-registered intravascular ultrasound.

The objective of the present study was to compare plaque burden (PB) calculated from optical coherence tomography (OCT) using deep learning (DL) with PB derived from co-registered intravascular ultrasound (IVUS). A DL algorithm was developed for automated plaque characterization and PB quantification from OCT images. However, the performance of this algorithm for PB quantification has not been validated. Five-year follow-up OCT and IVUS images from 15 patients implanted with bioresorbable vascular scaffold (BVS) at baseline were analyzed. Precise co-registration for 72 anatomical slices was achieved utilizing unique BVS radiopaque markers. PB derived from OCT DL and IVUS were compared. OCT cross-sections were divided into four subgroups with different media visibility level. The impact of media visibility on the numerical difference between OCT-derived and IVUS-derived PB was investigated. The stent sizes selected by OCT DL and IVUS were compared. Sixty-four paired OCT and IVUS cross-sections were compared. OCT DL showed good concordance with IVUS for PB assessment (ICC = 0.81, difference = -3.53 ± 6.17%, p < 0.001). The numerical difference between OCT DL-derived PB and IVUS-derived PB was not substantially impacted by missing segments of media visualization (p = 0.21). OCT DL showed a diagnostic accuracy of 92% in identifying PB > 65%. The stent sizes selected by OCT DL were smaller compared to the ones selected by IVUS (difference = 0.30 ± 0.34 mm, p < 0.001). The DL algorithm provides a feasible and reliable method for automated PB estimation from OCT, irrespective of media visibility. OCT DL showed good diagnostic accuracy in identifying PB > 65%, revealing its potential to complement conventional OCT imaging.

Validation of a simplified intravascular ultrasound core lab analysis method in stented coronary arteries.

To validate a simplified core laboratory intravascular ultrasound (IVUS) analysis method based on frames with visually determined minimal lumen areas (MLAs) as compared with a comprehensive (per frame) analysis method. IVUS-guided percutaneous coronary intervention has proven to be superior to angiography-guided stenting. In clinical practice, cross-sections with visually determined MLAare measured to determine lesion severity or minimal stent area (MSA), however, its accuracy has not been compared with a comprehensive per frame analysis method. A total of 50 stented coronary segments of anonymized core lab datasets were analyzed using a comprehensive analysis method and reanalyzed by two core lab analysts using the simplified method including a maximum of seven frames to be analyzed (the visually determined MSA, the first and last frame, and the MLA of each reference segment). The main parameters of interest were MSA, MLA in the reference segments, and plaque burden. The simplified method showed moderate agreement for measurement of the proximal MLA (7.51 ± 2.52 vs. 6.32 ± 1.88 mm2 , intraclass correlation coefficient [ICC] = 0.73), good agreement for the distal MLA (5.41 ± 1.85 vs. 5.11 ± 1.38 mm2 , ICC = 0.84) and plaque burden proximal (0.49 ± 0.12 vs. 0.50 ± 0.11, ICC = 0.88), and excellent agreement for the MSA (5.35 ± 1.05 vs. 5.32 ± 0.99 mm2 , ICC = 0.94) and plaque burden distal (0.47 ± 0.14 vs. 0.47 ± 0.12, ICC = 0.92), when compared with the comprehensive analysis method. Inter- and intraobserver analysis revealed good-to-excellent agreement for all parameters. Measuring poststenting IVUS cross-sections with visually determined MLAs by experienced core lab analysts is an accurate and reproducible method to identify MLAs.

Endothelial shear stress and vascular remodeling in bioresorbable scaffold and metallic stent

Background and aimsThe impact of endothelial shear stress (ESS) on vessel remodeling in vessels implanted with bioresorbable scaffold (BRS) as compared to metallic drug-eluting stent (DES) remains elusive. The aim of this study was to determine whether the relationship between ESS and remodeling patterns differs in BRS from those seen in metallic DES at 3-year follow-up. MethodsIn the ABSORB II randomized trial, lesions were investigated by serial coronary angiography and intravascular ultrasound (IVUS). Three-dimensional reconstructions of coronary arteries post-procedure and at 3 years were performed. ESS was quantified using non-Newtonian steady flow simulation. IVUS cross-sections in device segment were matched using identical landmarks. ResultsPaired ESS calculations post-procedure and at 3 years were feasible in 57 lesions in 56 patients. Post-procedure, median ESS at frame level was higher in BRS than in DES, with marginal statistical significance (0.97 ± 0.48 vs. 0.75 ± 0.39 Pa, p = 0.063). In the BRS arm, vessel area and lumen area showed larger increases in the highest tercile of median ESS post-procedure as compared to the lowest tercile. In contrast, in DES, no significant relationship between median ESS post-procedure and remodeling was observed. In multivariate analysis, smaller vessel area, larger lumen area, higher plaque burden post-procedure, and higher median ESS post-procedure were independently associated with expansive remodeling in matched frames. Only in BRS, younger age was an additional significant predictor of expansive remodeling. ConclusionsIn a subset of lesions with large plaque burden, shear stress could be associated with expansive remodeling and late lumen enlargement in BRS, while ESS had no impact on vessel dimension in metallic DES.

IVUS-based dosimetry on patients with repeat-radiated coronary arteries to the same site

Intracoronary radiation reduces recurrent in-stent restenosis (ISR). Repeat radiation may become necessary due to recurrent ISR. This study reports outcome-related dose calculations for twice-radiated coronary artery segments. A total of 22 patients with angiographic evidence of ISR in a previously treated native coronary artery were assigned for repeat percutaneous coronary intervention and intravascular brachytherapy (IVBT). Intravascular brachytherapy was performed either with a 192Ir- or a 90Sr/Y-source (prescription dose: 14-18 and 23 Gy each at 2 mm from the center of the source), or a 32P-source (20 Gy 1-mm deep to the vessel wall). The mean time interval between the two IVBT treatments was 394+/-306 days. For each patient, angiograms and intravascular ultrasound cross sections were reviewed, on the basis of anatomical landmarks, matched, and the twice-radiated vessel segment identified. Clinical follow-up at 379+/-146 days revealed a target vessel revascularization rate of 18.2% and a target lesion revascularization rate of 13.6%. One death was reported. Maximal dose and average dose at the endothelium were 261 and 124+/-72.3 Gy, and maximal dose and average dose at the adventitia-media border were 159 and 50.3+/-29.3 Gy. Fourteen patients had 1.71 times longer recurrence-free interval compared to the interval between both IVBT treatments. Repeat IVBT to the same ISR site is safe without any adverse clinical events at an average 12 months' follow-up. A second IVBT treatment led to a prolonged ISR-free survival for the majority of patients. The choice of isotope did not influence outcome.

Intravascular Ultrasound Evidence for Stabilization of Compensatory Enlargement of the Femoropopliteal Segment after Endograft Placement

To document whether the vasodilatory response seen at the anastomotic segment 6 months after placement of a balloon-expandable endograft in the femoropopliteal segment progresses between 6 and 24 months. Twelve patients (9 men; median age 65 years, range 47-75) treated with an investigational polytetrafluoroethylene (PTFE) endograft for obstructive disease of the femoropopliteal segment were studied with intravascular ultrasound (IVUS) immediately after placement and at 6 months (first follow-up period) and 24 months (second follow-up period). Matched IVUS cross sections derived from the endograft and the anastomotic segment were analyzed for changes in lumen (LA), vessel (VA), and plaque areas (PLA). Five patients had complete IVUS surveillance at both the first (mean 8 months, range 7-9) and second (mean 25 months, range 23-26) follow-up periods; 1 patient was lost to follow-up during the second interval, and another 6 were excluded owing to graft occlusion (n = 4) or no IVUS surveillance available (n = 2) during the second follow-up period. Matched IVUS cross sections derived from the endograft showed no significant change in LA during both follow-up periods (-8% and +1%, respectively). There was no evidence for intimal hyperplasia or endograft recoil. During both follow-up periods, IVUS cross sections derived from the anastomotic segment revealed significant increases in LA (+37% and +8%, respectively) and VA (+26% and +6%, respectively) (both p < 0.05). The change in PLA during both follow-up periods was not significant (+13% and +3%, respectively). The PTFE endograft seems to inhibit both intimal hyperplasia and constrictive remodeling. The short-term (6-month) vascular dilatory response seen at the anastomotic segment tends to stabilize at 2 years. Therefore, this endovascular anastomosis acts as an "ideal" end-to-end anastomosis.

Correlation between high frequency intravascular ultrasound and histomorphology in human coronary arteries

OBJECTIVETo test the efficacy of high frequency intravascular ultrasound (IVUS) transducers in identifying lipid/necrotic pools in atherosclerotic plaques.METHODS40 MHz transducers were used for in vitro IVUS assessment of 12 arterial segments (10 coronary and two carotid arteries, dissected from five different necropsy cases). IVUS acquisition was performed at 0.5 mm/s after ligature of the branching points to generate a closed system. Lipid/necrotic areas were defined by IVUS as large echolucent intraplaque areas surrounded by tissue with higher echodensity. To obtain histopathological sections corresponding to IVUS cross sections, vessels were divided into consecutive 3 mm long segments using the most distal recorded IVUS image as the starting reference. Samples were then fixed with 10% buffered formalin, processed for histopathological study, serially cut, and stained using the Movat pentacrome method.RESULTS122 sections were analysed. Lipid pools were observed by histology in 30 sections (25%). IVUS revealed the presence of lipid pools in 19 of these sections (16%; sensitivity 65%, specificity 95%).CONCLUSIONSIn vitro assessment of lipid/necrotic pools with high frequency transducers was achieved with good accuracy. This opens new perspectives for future IVUS characterisation of atherosclerotic plaques.

Intravascular ultrasound insights into plaque composition.

Previous studies correlating histomorphology with 20-30 MHz-derived intravascular ultrasound (IVUS) images showed that IVUS provides to some extent qualitative information on plaque composition. IVUS imaging proved to define calcifications with high sensitivity and specificity but was found to be less accurate in the assessment of soft components. Nevertheless previous studies on atherosclerotic plaque characterization were limited by use of low-frequency transducers that did not define accurately soft components. Our goal was to test the effectiveness of high frequency IVUS transducers in the identification of lipid/necrotic pools in atherosclerotic plaques. Forty MHz transducers were used for in vitro IVUS assessment of 12 arterial segments (10 coronary arteries and 2 carotid arteries dissected from 5 different autopsy cases). IVUS acquisition was performed at a 0.5 mm/s speed after ligature of the branching points to generate a closed system. Lipid necrotic areas were defined by IVUS as large echolucent intraplaque areas surrounded by tissue with higher echodensity. To obtain histopathologic sections corresponding to IVUS cross sections, vessels were divided into consecutive 3 mm-long segments using the most distal recorded IVUS image as the starting reference. Then, samples were fixed with 10% buffered formalin, processed for histopathologic study, serially cut, and stained with the Movat penthacrome method. One hundred twenty-two sections were analyzed. Lipid pools were observed by histology in 30 cross sections (25%). IVUS revealed the presence of lipid pools in 19 of 122 cross sections with a sensitivity and specificity of 67% and 94%, respectively. High frequency transducers accurately identify lipid/necrotic pools and open new perspectives on future IVUS characterization of atherosclerotic plaques.

Plaque area increase and vascular remodeling contribute to lumen area change after percutaneous transluminal angioplasty of the femoropopliteal artery: An intravascular ultrasound study

Objective: The aim of the study was to assess the change in lumen area (LA), plaque area (PLA), and vessel area (VA) after percutaneous transluminal angioplasty (PTA) of the femoropopliteal artery. Methods: This was a prospective study. Twenty patients were studied with intravascular ultrasound (IVUS) immediately after PTA and at follow-up examination. Multiple corresponding IVUS cross-sections were analyzed at the segments that were dilated by PTA (ie, treated sites; n = 168), including the most stenotic site (n = 20) and the nondilated segments (ie, reference sites; n = 77). Results: At follow-up examination, both the PLA increase (13%) and the VA decrease (9%) resulted in a significant LA decrease (43%) at the most stenotic sites ( P = .001). At the treated sites, the LA decrease (15%) was smaller and was caused by the PLA increase (15%). At the reference sites, the PLA increase (15%) and the VA increase (6%) resulted in a slight LA decrease (3%). An analysis of the IVUS cross-sections that were grouped according to LA change (difference ≥10%) revealed a similar PLA increase in all the groups: the type of vascular remodeling (VA decrease, no change, or increase) determined the LA change. At the treated sites, the LA change and the VA change correlated closely ( r = 0.77, P < .001). At the treated sites, significantly more PLA increase was seen in the IVUS cross-sections that showed hard lesion or media rupture ( P < .05). No relationhip was found between the presence of dissection and the quantitative changes. Conclusion: At the most stenotic sites, lumen narrowing was caused by plaque increase and vessel shrinkage. Both the treated sites and the reference sites showed a significant PLA increase: the type of vascular remodeling determined the LA change at follow-up examination. The extent of the PLA increase was significantly larger in the IVUS cross-sections that showed hard lesion or media rupture. (J Vasc Surg 1999;29:430-41.)

Failure of intravascular ultrasound to predict dissection after balloon angioplasty by using plaque characteristics

Intravascular ultrasound (IVUS) is more sensitive than angiography in the assessment of plaque characteristics before intervention and vascular damage after balloon angioplasty. On the basis of IVUS data, this finding may improve clinical treatment by reducing the incidence of severe dissections after balloon angioplasty. We therefore studied the relation between plaque characteristics and dissections after balloon angioplasty. First, an in vitro study on atherosclerotic arteries ( n = 42) was performed in which IVUS images were compared with histologic sections to validate the IVUS technique; second, the in vitro findings were compared with IVUS findings obtained in vivo ( n = 73). Dissections were observed in 37 histologic sections and visualized on IVUS in 22 (59%) of the corresponding ultrasonic cross-sections; in vivo dissections were demonstrated by IVUS in 46 (63%) cases. Dissections were generally seen at the thinnest region of the plaque on both histologic sections (92%) and IVUS cross-sections (in vitro 83%; in vivo 93%). No significant relation was found between pre-interventional plaque characteristics such as composition features and eccentricity and the incidence, location, and extent of postinterventional dissections. Thus IVUS is able to identify dissections after balloon angioplasty, generally occurring at the site of the thinnest plaque diameter. However, neither the incidence nor the severity of these dissections was related to any of the preinterventional plaque characteristics. (Am Heart J 1997;134:1075-81.)

Effect of balloon angioplasty in femoropopliteal arteries assessed by intravascular ultrasound

To study the effects of balloon angioplasty (PTA) of the femoropopliteal artery with intravascular ultrasound (IVUS). Corresponding IVUS cross-sections (n = 1033) obtained before and after PTA from 115 procedures were analysed. Vascular damage including plaque rupture, dissection and media rupture was assessed. Free lumen area (FLA), media-bounded area (MBA) and plaque area (PLA) were measured. After PTA vascular damage was seen at the target site in 83 (72%) arteries: plaque rupture in 30 (26%), dissection in 66 (57%) and media rupture in 20 (17%) arteries. The FLA increased from 5.4 +/- 3.4 mm2 to 14.1 +/- 5.0 mm2 (p < 0.001), MBA increased from 26.9 +/- 10.0 mm2 to 32.9 +/- 10.7 mm2 (p < 0.001) and PLA decreased from 21.6 +/- 8.5 mm2 to 18.8 +/- 8.0 mm2 (p < 0.001). The increase in MBA accounted for 68% of lumen gain. The frequency of vascular damage and the relative contribution of MBA increase and PLA decrease to luminal gain were not different in procedures with balloon diameter < or = 5 mm and > or = 6 mm. Vascular damage is common following PTA. Lumen gain is mainly due to vessel expansion and, to a lesser extent, to a decrease in plaque area.

Paradoxical Arterial Wall Shrinkage May Contribute to Luminal Narrowing of Human Atherosclerotic Femoral Arteries

This study was done to assess how local changes in vessel size, together with plaque load, determine luminal narrowing in atherosclerotic arteries. Fifty-one human femoral arteries were analyzed: 32 postmortem and 19 in vivo by 30-MHz intravascular ultrasound. Histological and intravascular ultrasound cross sections were examined every 0.5 cm over an arterial segment 10 to 15 cm long. In each cross section we measured the lumen area and the area circumscribed by the internal elastic lamina (the IEL area). In each arterial segment, the cross section that contained the least amount of plaque was the reference site. For each cross section, the lumen area stenosis was expressed as percent of the lumen area in the reference site. Similarly, the IEL area was expressed as percent of the IEL area in the reference site (the relative IEL area). There was a significant negative correlation between the relative IEL area and the lumen area stenosis percentage (r = -.62, P < .001 for histology and r = -.66, P < .001 for intravascular ultrasound). When lumen area stenosis was less than about 25%, mainly compensatory enlargement was observed. When lumen area stenosis exceeded about 25%, however, mainly a decrease of the IEL area was observed, which is consistent with arterial wall shrinkage. Furthermore, the increase in plaque area does not account for the total loss of luminal area. There was a moderate correlation between an increase in plaque area and reduction of the corresponding lumen area (r = .49 and r = .56 for histology and intravascular ultrasound, respectively). The decrease in luminal area cannot be attributed to plaque increase alone. Arterial wall shrinkage is a paradoxical mechanism that may contribute to severe luminal narrowing of the atherosclerotic human femoral artery.

1000–33 On-line Automated Lumen Volume Measurement With 3-D Intracoronary Ultrasound During Coronary Interventions

The aim of the study was the clinical validation of an on-line fully automated lumen detection technique with intravascular ultrasound (IVUS). Assessment of lumen dimensions with IVUS was performed in 10 pts undergoing transcatheter therapy (5 PTCA, 2 DCA, 3 Stents). The images of 10 coronary segments 20 mm long in the treated area were acquired during motorized pull-back (1 mm/s) and processed using an automated contour detection algorithm based on acoustic quantification of blood backscatter and coronary wall. For each segment, 171 ultrasound images (8.5/mm) were processed in the laboratory, immediately after acquisition (processing time: 1.35 min.) and subsequently corrected off-line by an experienced analyst. Segment lumen volume was calculated by multiplying mean lumen area by segment length. Of the 1,710 on-line IVUS cross-sections obtained, 232 (13.6%) could not be analyzed due to failure of the algorithm used for lumen detection induced by presence of side branches, lack of sharpness of the lumen-wall interface or shadowing from calcium interpreted as lumen. On the remaining frames (1,478; 86.4%), on-line vs off-line comparison for mean lumen area and segment volume was performed. On-line measurement of lumen area and volume were highly correlated with the off-line measurements (r = 0.85 for area; see fig. for lumen), with a mean difference of 7.4 ± 14.1% and 5.9 ± 5.4% for lumen area and volume, respectively. In selected optimal sequences of images acquired during coronary interventions, on-line automated quantitative 3-D provides reliable measurements of lumen dimension, requiring limited manual interaction.Download : Download high-res image (57KB)Download : Download full-size image