Intravascular Ultrasound Imaging Research Articles

Application of an enhanced device to transluminal retrieval of malappositioned coronary stents: An experimental study.

This study investigated the application of a novel enhanced device to retrieval of deployed stents in a porcine coronary model. Recurrence of in-stent restenosis and stent thrombosis still remains to be resolved. Under these conditions, it is sometimes necessary to retrieve malfunctional stents responsible for thrombosis. However, few data exist regarding the feasibility and safety of retrieval device use in previously deployed coronary stents. We have developed an enhanced device consisting of an asymmetric forceps, conducting shaft (1.6 mm diameter, 150 cm length), and control handle. Bare-metal stents (3 mm diameter) were implanted in four pigs to create a malapposition model. Coronary artery injury was evaluated by intravascular ultrasound (IVUS) and histological imaging on the first and 14th days. The device was delivered to the coronary artery using the existing catheter (7 Fr). After opening the forceps, the blade was forced into the space between the vessel wall and the stent, and the stent struts were then grasped with the forceps. This was then pulled back into the catheter, still grasping the stent struts with the forceps. All stents were successfully retrieved by this method (n = 4). On the first day, no apparent vessel wall injury was detectable by IVUS, although histological findings revealed damage to endothelial monolayer on retrieval of deployed stent. On the 14th day, mild intimal thickening was observed by IVUS and histology. These results demonstrate that the present device can be applied to transluminal retrieval of acquired malappositioned coronary stents.

Anatomical plaque and vessel characteristics are associated with hemodynamic indices including fractional flow reserve and coronary flow reserve: A prospective exploratory intravascular ultrasound analysis

ObjectivesTo assess the relationship between anatomical form and physiological function in atherosclerotic coronary arteries. BackgroundAlthough adverse cardiovascular events are predicted by plaque morphology or invasively-derived hemodynamic indices, the link between these important prognostic measures remains unexplored. MethodsPatients with stable angina underwent fractional flow reserve (FFR), coronary flow reserve (CFR), pressure-derived collateral flow index (CFIp), trans-myocardial biomarker sampling and radiofrequency intravascular ultrasound (IVUS) imaging prior to intervention. Physiological ischemia was defined as either FFR≤0.8 or CFR<2.0. ResultsMean FFR was 0.70±0.15 and CFR was 2.1±1.3, with 68/92 lesions having FFR≤0.8 and 61/92 having CFR<2.0. On IVUS, FFR≤0.8 lesions had reduced minimal luminal area (MLA, p=0.03), increased plaque burden (PB, p=0.04) and volume (p=0.01). There was no relationship between FFR and IVUS-defined plaque composition. FFR≤0.8 was observed in 75.3%, 72.4% and 70.4% of lesions with MLA≤4mm2, PB≥70% and thin-cap fibroatheroma, respectively. Multivariate regression demonstrated FFR≤0.8 was independently predicted by MLA (odds ratio (OR) 0.53, 95% CI 0.29–0.97, p=0.04) and PB (OR 1.10, 95% CI 1.01–1.21, p=0.03). There were no identifiable relationships between plaque structure and CFR or CFIp. CFR<2.0 was associated with whole vessel necrotic core increases (p=0.047), fibrofatty tissue reduction (p=0.004) and elevated baseline transmyocardial high-sensitivity C-reactive protein (hsCRP) gradients (p=0.02). ConclusionsMeasures of plaque structure including PB and MLA are independently associated with FFR, but not with CFR or CFIp. Instead, vessels with low CFR have increased lipid accumulation and a higher transmyocardial hsCRP gradient. These results may explain similarities in clinical outcomes between physiologically and anatomically orientated trials.

Transvenous Intravascular Ultrasound–Guided Endovascular Treatment for Chronic Total Occlusion of the Infrainguinal Arteries

Purpose: To investigate the 1-year outcomes of transvenous intravascular ultrasound (IVUS)–guided endovascular therapy (EVT) for chronic total occlusion (CTO) of the lower extremity arteries. Methods: Transvenous IVUS-guided EVT was performed in 44 patients (50 limbs) with CTO of the femoropopliteal arteries or tibioperoneal trunk. Treatment involved crossing a guidewire through the CTO under the guidance of both fluoroscopic and IVUS imaging, along with insertion of the IVUS catheter into a vein parallel to the target artery. Primary success rate, complications, and target lesion revascularization (TLR) at 12-month follow-up were investigated. Results: Successful recanalization, defined as grade 3 flow (Thrombolysis in Myocardial Infarction score) and no flow-limiting dissection, was observed in 48 (96%) limbs. Two limbs with failed recanalization had a very long CTO lesion from the superficial femoral artery to below the knee. A bidirectional approach was selected in 11 (22%) limbs. Complications at the access site occurred in only 2 patients. The rate of freedom from TLR at 12 months was 77.9% (95% confidence interval 61.4 to 87.9). Conclusion: Transvenous IVUS-guided EVT is safe and can provide optimal short-term results for EVT of CTO in the infrainguinal arteries. IVUS-guided EVT may be one of the most effective treatment strategies for CTO of the femoropopliteal arteries or tibioperoneal trunk.

Detection of the Vulnerable Coronary Atherosclerotic Plaque—Promises and Limitations

The merit of imaging “vulnerable atherosclerotic plaques” remains highly controversial. This review aims at providing current evidence for both its benefit and limitations. Results from optical coherence tomography and intravascular ultrasound imaging in patients with coronary heart disease suggest that certain individual coronary atherosclerotic plaque characteristics, e.g., large lipid core in a fibroatheroma, are associated with greater risk of adverse patient outcome. However, a closer look at these studies reveals that these associations are confounded by the relationship of “vulnerable plaque” characteristics with baseline lumen obstruction, which is a known predictor of recurrent angina and the main component of the reported adverse patient outcome. Recent insights into the pathophysiology of acute coronary syndromes suggest it to be an exceedingly complex process involving numerous local and systemic factors, which hinders outcome prediction. The quest for the vulnerable plaque rests on the erroneous assumption that detecting coronary atherosclerotic lesions, which are prone to rupture or erode, will identify individuals at high risk of suffering acute coronary events. However, there is strong and consistent evidence suggesting that plaques most commonly rupture without associated clinical symptoms. Instead, ruptured plaques typically heal clinically silently and lead to plaque progression. The atherosclerotic disease burden, its metabolic activity, and risk factors for an inadequate response by the coagulation system to plaque disruption, on the other hand, are important predictors of acute coronary event risk and deserve our attention more than individual plaques.

Intravascular Ultrasound Imaging With Virtual Source Synthetic Aperture Focusing and Coherence Factor Weighting.

Intravascular ultrasound (IVUS) has been frequently used for coronary artery imaging clinically. More importantly, IVUS is the fundamental image modality for most advanced multimodality intravascular imaging techniques, since it provides a more comprehensive picture of vessel anatomy on which other imaging data can be superimposed. However, image quality in the deeper region is poor because of the downgraded lateral resolution and contrast-to-noise ratio (CNR). In this paper, we report on the application of an ultrasound beamforming method that combines virtual source synthetic aperture (VSSA) focusing and coherence factor weighting (CFW) to improve the IVUS image quality. The natural focal point of conventional IVUS transducer was treated as a virtual source that emits spherical waves within a certain region. Mono-static synthetic aperture focusing was conducted to achieve higher resolution. Coherence factor was calculated using delayed RF signals and applied to the synthesized beam to increase the CNR and focusing quality. The proposed method was tested through simulations in Field II and imaging experiments in both linear and rotational scans. The lateral resolution for linear scan mode is improved from 165-524 to 126-143 μm ; resolution for rotational scan mode improves by up to 42%. CNR improvement by up to 1.5 was observed on the anechoic cysts of different sizes and at different locations. Herein, it is demonstrated that the beamforming method, which combines VSSA and CFW, can significantly improve the IVUS image quality. This approach can be readily integrated into the current IVUS imaging system for enhanced clinical diagnosis.

Low major adverse cardiac event rates following bioresorbable vascular scaffold implantation: Impact of implantation technique on treatment outcomes

Background and objectiveStudies conducted across the world have reported that the rates of major adverse cardiac events (MACE) following the use of bioresorbable vascular scaffolds (BVS) are comparable to that noted with traditional drug eluting stents (DES). However, there is limited data on the immediate and medium-term clinical outcomes following the use of the Absorb BVS (Abbott Vascular, Santa Clara, SA) in the Indian context. This study was conducted to determine real-world evidence on the immediate and medium-term clinical outcomes in all patients undergoing percutaneous coronary intervention (PCI) with the Absorb BVS. MethodsData of all patients who were treated with Absorb BVS at our center were evaluated. Between December 2012 and October 2016, 142 patients underwent PCI with BVS. The MACE rates during hospitalization, at 30days, 3 months, 6 months after PCI, and every 6 months thereafter were the primary endpoints evaluated with median follow up of 13 months. ResultsMean age of the study participants was 53.7±11.8years. Intravascular ultrasound imaging was performed in 15.34% of patients. Predilatation and postdilatation were performed in 81.8% and 84.6% of scaffolds, respectively. There were no episodes of MACE during hospitalization. However, 1 BVS-related MACE was observed at the 1-month (0.7%) as well as at the ≥12 month (0.8%) follow up visits. At the 6- and 12-month follow up visits, 2 (1.5%) and 3 (2.5%) non-BVS-related MACEs, respectively, were recorded. ConclusionThe use of Absorb BVS in this real-world experience was associated with very good immediate and medium-term clinical outcomes.

Venography versus intravascular ultrasound for diagnosing and treating iliofemoral vein obstruction

The Venogram vs IVUS for Diagnosing Iliac vein Obstruction (VIDIO) trial was designed to compare the diagnostic efficacy of intravascular ultrasound (IVUS) with multiplanar venography for iliofemoral vein obstruction. During a 14-month period beginning July 2014, 100 patients with chronic Clinical, Etiologic, Anatomic, and Pathophysiologic clinical class C4 to C6 venous disease and suspected iliofemoral vein obstruction were enrolled at 11 U.S. and 3 European sites. The inferior vena cava and common iliac, external iliac, and common femoral veins were imaged. Venograms were measured for vein diameter; IVUS provided diameter and area measurements. Multiplanar venograms included three views: anteroposterior and 30-degree right and left anterior oblique views. A core laboratory evaluated the deidentified images, determining stenosis severity as the ratio between minimum luminal diameter and reference vessel diameter, minimal luminal area, and reference vessel area. A 50% diameter stenosis by venography and a 50% cross-sectional area reduction by IVUS were considered significant. Analyses assessed change in procedures performed on the basis of imaging method and concordance of measurements between each imaging method. Venography identified stenotic lesions in 51 of 100 subjects, whereas IVUS identified lesions in 81 of 100 subjects. Compared with IVUS, the diameter reduction was on average 11% less for venography (P< .001). The intraclass correlation coefficient was 0.505 for vein diameter stenosis calculated with the two methods. IVUS identified significant lesions not detected with three-view venography in 26.3% of patients. Investigators revised the treatment plan in 57 of 100 cases after IVUS, most often because of failure of venography to detect a significant lesion (41/57 [72%]). IVUS led to an increased number of stents in 13 of 57 subjects (23%) and the avoidance of an endovascular procedure in 3 of 57 subjects (5%). Overall, IVUS imaging changed the treatment plan in 57 patients; 54 patients had stents placed on the basis of IVUS detection of significant iliofemoral vein obstructive lesions not appreciated with venography, whereas 3 patients with significant lesions on venography had no stent placed on the basis of IVUS. IVUS is more sensitive for assessing treatable iliofemoral vein stenosis compared with multiplanar venography and frequently leads to revised treatment plans and the potential for improved clinical outcome.

Comparison of intravascular ultrasound- and centerline computed tomography-determined aortic diameters during thoracic endovascular aortic repair

BackgroundAccurate sizing of stent grafts during thoracic endovascular aortic repair (TEVAR) is critical for a successful outcome. Centerline measurements using three-dimensional reconstruction of preoperative computed tomography angiography (CTA) is the current standard for stent graft sizing. However, this technique is predicated on an idealized straightened aorta and does not account for the variability in the aortic diameter during the cardiac cycle or the overall status of the patient's volume. Intravascular ultrasound (IVUS) offers real-time cross-sectional imaging of the aorta orthogonal to the support wire, thereby providing an adjunctive method for aortic diameter determination at the time of TEVAR. MethodsA retrospective review was performed on all patients who underwent TEVAR for nontraumatic aortic pathology from July 2015 to December 2015. Preoperative CTA images were reconstructed on a dedicated three-dimensional workstation. CTA centerline aortic diameter measurements were performed in major and minor axes at 1-cm intervals from the left subclavian origin to 20 cm distally. The IVUS images were acquired intraoperatively through 1-cm stepwise pullback along the aorta from the left subclavian origin to 20 cm. IVUS aortic diameters were measured at the maximum phase during the cardiac cycle. The average values of major and minor axes diameters from both modalities were calculated at each location for comparison. Linear regression analysis was performed to evaluate correlation, and Bland-Altman plots assessed agreement between different imaging modalities. ResultsDuring the study period, 26 patients underwent TEVAR. Of these, 20 patients had adequate CTA and IVUS images, providing 355 paired measurements. There was a high correlation between CTA- and IVUS-determined aortic diameters (R = 0.62; P < .001). However, Bland-Altman analysis showed that, compared with CT, IVUS resulted in larger aortic diameters, with the mean difference of 3.09 mm. There was a significant variability between IVUS and CTA with the standard deviation of difference (SD diff) of 4.56 mm. When stratified by the aortic position, a high degree of agreement was observed at the base of the left subclavian (position 0), with a mean difference of –2.69 mm and an SD diff of 4 mm. The agreement was the lowest at the angulated aortic segments (2 cm to 7 cm distal to the subclavian origin) with a mean difference up to 7.96 mm and an SD diff up to 8.27 mm. ConclusionsIVUS imaging and centerline CTA may provide significantly different aortic diameter measurements, particularly in angulated aortic segments. Caution must be taken when sizing a stent graft using CTA alone, particularly in an angulated proximal landing zone.

Acute changes in histopathology and intravascular imaging after catheter-based renal denervation in a porcine model.

ObjectivesWe first aimed to identify the histopathological changes occurring immediately after renal denervation (RDN) with radiofrequency energy, and then to assess the feasibility of determining procedural success using currently available clinical intravascular imaging techniques.BackgroundCatheter‐based RDN has been used as an alternative therapy for hypertension. However, no practical endpoint to determine procedural success during treatment has been established.MethodsA total of 39 ablation lesions were induced in vivo in eight porcine renal arteries and a total of 15 ablation lesions were induced ex vivo in five excised porcine renal arteries with a radiofrequency delivery device. Acute histological changes and appearance on intravascular imaging of the lesions were investigated with light microscopy, transmission electron microscopy, intravascular ultrasound (IVUS), and optical frequency domain imaging (OFDI).ResultsMarked changes were noted in media, adventitia, and perirenal‐arterial nerves immediately after in vivo ablation. Changes visualized on IVUS were characterized by focal adventitial thickening comprising a relatively echogenic layer around a heterogeneously hypoechoic interior region, and on OFDI as disappearance of the external elastic membrane signals with high scattering of signals in the surface layer. The changes after ex vivo ablation were histopathologically identical to those from in vivo ablation. There were statistically significant positive correlations in measured dimensions (area, depth, width, and diameter) of ablation lesions between histopathology and IVUS/OFDI findings (Pearson correlation coefficients = 0.69–0.77).ConclusionsThese findings suggest that observation of treated renal arteries by IVUS or OFDI immediately after RDN improves the success rate of RDN.

Determination of Plaque Distribution in Intravascular Ultrasound Imaging: Visualization of an Unfolded Artery

A novel three-dimensional intravascular ultrasound (3D IVUS) reconstruction algorithm was developed to provide volumetric 3D visualization of plaque distribution across an unfolded artery. An arterial phantom was utilized to validate the nonlinear interpolation technique to generate intermediary IVUS images. Following the intermediary IVUS image generation, volumetric 3D IVUS visualization was performed. Smooth transitional changes in shape and grayscale were found between the intermediary and original slices. Volumetric 3D IVUS visualization of the unfolded curved artery provided realistic luminal surface images with physiologic grayscale information. This novel 3D IVUS visualization strategy has the potential to help with assessment of 3D plaque distribution across the curved arterial structure.

Tissue characterization of non-culprit intermediate coronary lesions in non ST elevation acute coronary syndromes.

BackgroundDisruption of vulnerable plaques is the most common cause of acute coronary syndromes. Intravascular ultrasound facilitates cross-sectional imaging of coronary arteries. We aimed at using IVUS to investigate the morphology and tissue characteristics of atherosclerotic plaques of non-culprit intermediate coronary lesions in non-ST elevation ACS setting.MethodsIVUS assessment of sixty-one intermediate coronary lesions in twenty-eight patients with the diagnosis of Non ST elevation acute coronary syndromes. Ultrasound signals were obtained by an IVUS system using a 40-MHz catheter.ResultsMean age was 53.2 ± 9.1 years. Males = 20 (71.4%). Smoking in 17 (60.7%), hypertension in 16 (57.1%), Dyslipidemia in 12 (42.9%) and DM in 8 (28.6%). Culprit vessels represent 42% of affected vessels. Sixty-one intermediate lesions were detected. Twenty-nine lesions in culprit vessels and thirty-two lesions in non-culprit vessels with higher lipidic content in lesions of culprit vessels (P < 0.001) while a higher calcific content in lesions of non-culprit vessels (P < 0.001). Higher calcific content of proximal more than distal lesions (P = 0.048). Negative remodeling in 55.7% of lesions.ConclusionsA higher lipidic content in lesions of culprit vessels, while the lesions of non-culprit vessels were more calcific. Higher calcific content of proximal more than distal lesions was defined as well.

Sex differences in plaque characteristics by intravascular imaging in patients with coronary artery disease.

We aimed to study sex differences in coronary plaque burden and plaque composition in patients with coronary artery disease (CAD). Virtual histology intravascular ultrasound (VH-IVUS) and near-infrared spectroscopy (NIRS) imaging of a non-culprit coronary artery was performed in 178 (23.5%) women and 581 (76.5%) men who underwent invasive management of stable angina pectoris (SAP) or acute coronary syndrome (ACS). Women were older and had a worse cardiovascular risk profile than men, but less extended angiographic coronary disease. Irrespective of the presenting diagnosis, women had lower VH-IVUS-derived plaque burden than men (38.1% vs. 40.5% in SAP, and 35.9% vs. 38.8% in ACS). Standardised (mean 211 vs. 263 mm3 in SAP, and 199 vs. 245 mm3 in ACS) total plaque volume was lower in women. Volumes of fibrous tissue, fibro-fatty tissue, necrotic core and dense calcium were also lower in women. NIRS-derived lipid core burden index (LCBI) was lower in women, in particular in SAP (mean LCBI in the worst 4 mm 220 vs. 240). The observed differences remained significant after adjustment for clinical characteristics. Women had more favourable plaque characteristics than men, despite their worse risk profile. Long-term follow-up studies are required to evaluate the clinical consequences.

IP045. Management of Abdominal Aortic Aneurysms With Atypical Renal Artery Anatomy

Renal artery anomalies occur at a rate of 1% to 2%, and with a growing number of renal transplants performed annually, we are more frequently faced with particular challenges to abdominal aortic aneurysm repair. We describe here adjuncts used to manage such anatomic variants. This is a retrospective review of a prospectively collected database of all abdominal aortic aneurysms repaired in a single academic vascular surgery practice. Patients with renal transplants, congenital single/pelvic kidneys arising from the distal abdominal aorta or iliac arteries, and horseshoe kidneys were included in the review. Over an 8-year period, 18 patients were identified (prior renal transplant, n = 9; horseshoe kidney, n = 3; congenital single/pelvic kidney, n = 6). All prior transplant patients were treated with endovascular repair, with four requiring aortouniiliac extension to the external iliac artery contralateral to the renal transplant for aneurysm exclusion (with retrograde flow via cross femoral bypass providing renal perfusion). Additionally, three transplant patients required carotid artery access for device deployment due to severe iliofemoral occlusive disease or origin of renal transplant off of the internal iliac artery. Two horseshoe kidney patients underwent open aneurysm repair with direct reimplantation of accessory renal arteries, while one underwent standard endovascular repair with exclusion of an isthmus branch. While there was no renal dysfunction noted, the patient did have a prolonged course of abdominal pain postoperatively due to infarct of the devascularized renal segment. Of the congenital single/pelvic kidney cohort, two underwent open repair with renal reimplantation, two underwent standard endovascular repair, one was treated with aortouniiliac and cross-femoral bypass, and one was treated in a staged fashion with initial ileorenal bypass and subsequent fenestrated endovascular repair. Intravascular ultrasound imaging was used to minimize contrast use in patients with chronic renal insufficiency (creatinine >1.2 mg/dL, n = 6). Over a mean follow-up of 41.7 months (range, 1-110 months), there were no aortic related deaths or reinterventions, no decline in renal function (measured by serum creatinine and glomerular filtration rate), and 100% patency of the preserved renal arteries. Atypical renal anatomy provides unique challenges to abdominal aortic aneurysm repair. The use of technical adjuncts can make repair of such aneurysms safe with good long-term outcomes that do not impair renal function.

Contemporary outcomes after venography-guided treatment of patients with May-Thurner syndrome.

Patients with May-Thurner syndrome (MTS) present with a spectrum of findings ranging from mild left leg edema to extensive iliofemoral deep venous thrombosis (DVT). Whereas asymptomatic left common iliac vein (LCIV) compression can be seen in a high proportion of normal individuals on axial imaging, the percentage of these persons with symptomatic compression is small, and debate exists about the optimal clinical and diagnostic criteria to treat these lesions in patients with symptomatic venous disease. We evaluated our approach to venography-guided therapy for individuals with symptomatic LCIV compression and report the outcomes. All patients with suspected May-Thurner compression of the LCIV between 2008 and 2015 were analyzed retrospectively. Patients with chronic iliocaval lesions not associated with compression of the LCIV were excluded from analysis. Criteria for intervention included LCIV compression in the setting of (1) leg edema/venous claudication with associated venographic findings (collateralization, iliac contrast stagnation, and contralateral cross cross-filling), or (2) left leg deep venous thrombosis. Outcome measures included presenting Clinical, Etiology, Anatomy, Pathophysiology (CEAP) score, postintervention CEAP score, primary patency, and secondary patency. Technical success was defined as successful stent implantation without intraoperative device complications, establishment of in-line central venous flow, and less than 30% residual LCIV stenosis. Of the 63 patients evaluated, 32 (51%) had nonthrombotic MTS and presented with leg edema (100%) or venous claudication (47%). Thirty-one patients (49%) had thrombotic MTS and presented with acute (26%) or chronic (71%) DVT, leg edema (100%), or venous claudication (74%). The mean presenting CEAP score was 3.06 and 3.23 for nonthrombotic and thrombotic MTS, respectively. Forty-four patients (70%) underwent successful intervention with primary stenting (70%) or thrombolysis and stenting (30%); 14 nonthrombotic MTS patients were treated conservatively with compression therapy alone, and 5 thrombotic MTS patients were treated with lysis or angioplasty alone. Clinical improvement and decrease in CEAP score occurred in 95% and 77% of stented patients compared with 58% and 32% of nonstented patients. Complete symptom resolution was achieved in 48% of patients overall, or 64% of stented patients and only 21% of nonstented patients. Complications included two early reocclusions. Primary and secondary 2-year patency rates were 93% and 97% (mean follow-up, 20.3 months) for stented patients. Venography-guided treatment of MTS is associated with excellent 1-year patency rates and a significant reduction in symptoms and CEAP score. Treating symptomatic MTS patients on the basis of physiologically relevant venographic findings rather than by intravascular ultrasound imaging alone results in excellent long-term patency and clinical outcomes but may result in undertreatment of some patients who could benefit from stent implantation.

Three-Dimensional Intravascular Reconstruction Techniques Based on Intravascular Ultrasound: A Technical Review.

Intravascular ultrasound (IVUS) imaging provides two-dimensional (2-D) real-time luminal and transmural cross-sectional images of intravascular vessels with detailed pathological information. It has offered significant advantages in terms of diagnosis and guidance and has been increasingly introduced from coronary interventions into more generalized endovascular surgery. However, IVUS itself does not provide spatial pose information for its generated images, making it difficult to construct a 3-D intravascular visualization. To address this limitation, IVUS imaging-driven 3-D intravascular reconstruction techniques have been developed. These techniques enable accurate diagnosis and quantitative measurements of intravascular diseases to facilitate optimal treatment determination. Such reconstruction extends the IVUS imaging modality from pure diagnostic assistance to intraoperative navigation and guidance and supports both therapeutic options and interventional operations. This paper presents a comprehensive survey of technological advances and recent progress on IVUS imaging-based 3-D intravascular reconstruction and its state-of-the-art applications. Limitations of existing technologies and prospects of new technologies are also discussed.

Combined intracoronary 2D–3D optical coherence tomography and intravascular ultrasound imaging in left main severe stent malapposition

Combined intracoronary 2D–3D optical coherence tomography and intravascular ultrasound imaging in left main severe stent malapposition

Guiding multimodal registration with learned optimization updates.

In this paper, we address the multimodal registration problem from a novel perspective, aiming to predict the transformation aligning images directly from their visual appearance. We formulate the prediction as a supervised regression task, with joint image descriptors as input and the output are the parameters of the transformation that guide the moving image towards alignment. We model the joint local appearance with context aware descriptors that capture both local and global cues simultaneously in the two modalities, while the regression function is based on the gradient boosted trees method capable of handling the very large contextual feature space. The good properties of our predictions allow us to couple them with a simple gradient-based optimization for the final registration. Our approach can be applied to any transformation parametrization as well as a broad range of modality pairs. Our method learns the relationship between the intensity distributions of a pair of modalities by using prior knowledge in the form of a small training set of aligned image pairs (in the order of 1-5 in our experiments). We demonstrate the flexibility and generality of our method by evaluating its performance on a variety of multimodal imaging pairs obtained from two publicly available datasets, RIRE (brain MR, CT and PET) and IXI (brain MR). We also show results for the very challenging deformable registration of Intravascular Ultrasound and Histology images. In these experiments, our approach has a larger capture range when compared to other state-of-the-art methods, while improving registration accuracy in complex cases.

Intravascular Ultrasound Analysis of Intraplaque Versus Subintimal Tracking in Percutaneous Intervention for Coronary Chronic Total Occlusions and Association With Procedural Outcomes

ObjectivesUsing intravascular ultrasound (IVUS), the authors compared outcomes by observed wire position (intraplaque vs. subintimal) achieved during successful chronic total occlusion (CTO) lesion treatment. BackgroundRecent successes in CTO percutaneous coronary intervention (PCI) have used both intraluminal and subintimal wire tracking to improve procedural success. IVUS may be used to determine the course of wire tracking after crossing a CTO. MethodsFrom March 2014 to March 2016, data were collected into a single-center database from 219 patients undergoing CTO PCI with concomitant IVUS imaging. IVUS-visualized wire tracking patterns were then retrospectively examined. Clinical outcomes with a composite in-hospital cardiovascular endpoint of all-cause death, periprocedural myocardial infarction, and in-hospital target lesion revascularization were analyzed along with IVUS-detected vascular injury. ResultsOf the 524 lesions assessed, 219 patients with successfully recanalized CTO lesions had adequate IVUS imaging and were included. Subintimal tracking was detected in 52.1% of overall cases (86.7% dissection re-entry, 27.9% wire escalation). Minimal stent area of the CTO segment and prevalence of significant edge dissection were similar in the 2 groups. In the subintimal tracking group, there was a higher rate of the composite endpoint, mostly driven by periprocedural myocardial infarction. Subintimal tracking was associated with significantly greater IVUS-detected vascular injury, angiographic dye staining/extravasation, and branch occlusion. ConclusionsIVUS-detected subintimal tracking is observed in approximately one-half of all successful CTO PCI cases and is associated with an expected higher, yet acceptable, event rate with no difference in minimal stent area or edge dissection among patients undergoing contemporary hybrid CTO PCI.

Abstract 383: Patient-Specific Coronary Models Combining Intravascular Ultrasound and Optical Coherence Tomography Lead to More Accurate Plaque Cap Thickness and Stress/Strain Quantifications

Accurate cap thickness and stress/strain quantifications are of fundamental importance for vulnerable plaque research. An innovative modeling approach combining intravascular ultrasound (IVUS) and optical coherence tomography (OCT) is introduced for more accurate patient-specific coronary morphology and stress/strain calculations. In vivo IVUS and OCT coronary plaque data were acquired from two patients with informed consent obtained. IVUS and OCT images were segmented, co-registered, and merged to form the IVUS+OCT data set, with OCT providing accurate cap thickness. Biplane angiography provided 3D vessel curvature. Due to IVUS resolution (150 μm), original virtual histology (VH) IVUS data often had lipid core exposed to lumen since it sets cap thickness as zero when cap thickness &lt;150 μm. VH-IVUS data were processed with minimum cap thickness set as 50 and 180 μm to generate IVUS50 and IVUS180 data sets for modeling use. 3D fluid-structure interaction models based on IVUS+OCT, IVUS50 and IVUS180 data sets were constructed to investigate the impact of OCT cap thickness improvement on stress/strain calculations. Figure 1 is a brief summary of results from 27 slices with cap covering lipid cores from 2 patients. Mean cap thickness (unit: mm) from Patient 1 was 0.353 (OCT), 0.201 (IVUS50), and 0.329 (IVUS180), respectively. Patient 2 mean cap thickness was 0.320 (OCT), 0.224 (IVUS50), and 0.285 (IVUS180). IVUS50 underestimated cap thickness (27 slices) by 34.5%, compared to OCT cap values. IVUS50 overestimated mean cap stress (27 slices) by 45.8%, compared to OCT cap stress (96.4 vs. 66.1 kPa). IVUS50 maximum cap stress was 59.2% higher than that from IVUS+OCT model (564.2 vs. 354.5 kPa). Differences between IVUS and IVUS+OCT models for mean cap strain and flow shear stress were modest (cap strain: &lt;12%; FSS &lt;2%). Conclusion: IVUS+OCT data and models could provide more accurate cap thickness and stress/strain calculations which will serve as basis for plaque research.

Accurate three-dimensional modeling of blood vessels using computer tomography, intravascular ultrasound, and biplane angiogram images

In this paper, we propose a novel method for three-dimensional (3D) blood vessel modeling. Given the incomplete nature of medical images, a 3D blood vessel model that includes the intima and adventitia cannot be reconstructed with a single medical image. Intravascular ultrasound (IVUS) images are used to obtain detailed intimal and adventitial information. Then, X-ray angiogram images are used to calculate the position and orientation of IVUS images. Combining these medical images can generate a 3D blood vessel model. To visualize a blood vessel via IVUS, a catheter that is attached to a miniaturized ultrasound device is inserted into the blood vessel. The insertion of the catheter deforms the blood vessel. This deformation is reflected in the 3D blood vessel model that is developed from combining IVUS and X-ray angiogram images. To address this problem, we propose a novel method for 3D blood vessel modeling using undeformed intimal and adventitial information from IVUS images. Our proposed method has potential applications in hemodynamic analysis.