3D Plaque Research Articles

A parametric study of the effect of 3D plaque shape on local hemodynamics and implications for plaque instability

The vast majority of heart attacks occur when vulnerable plaques rupture, releasing their lipid content into the blood stream leading to thrombus formation and blockage of a coronary artery. Detection of these unstable plaques before they rupture remains a challenge. Hemodynamic features including wall shear stress (WSS) and wall shear stress gradient (WSSG) near the vulnerable plaque and local inflammation are known to affect plaque instability. In this work, a computational workflow has been developed to enable a comprehensive parametric study detailing the effects of 3D plaque shape on local hemodynamics and their implications for plaque instability. Parameterized geometric 3D plaque models are created within a patient-specific coronary artery tree using a NURBS (non-uniform rational B-splines)-based vascular modeling pipeline. Realistic blood flow features are simulated by using a Navier–Stokes solver within an isogeometric finite-element analysis framework. Near wall hemodynamic quantities such as WSS and WSSG are quantified, and vascular distribution of an inflammatory marker (VCAM-1) is estimated. Results show that proximally skewed eccentric plaques have the most vulnerable combination of high WSS and high positive spatial WSSG, and the presence of multiple lesions increases risk of rupture. The computational tool developed in this work, in conjunction with clinical data, -could help identify surrogate markers of plaque instability, potentially leading to a noninvasive clinical procedure for the detection of vulnerable plaques before rupture.

Hepatocyte growth factor as indicator for subclinical atherosclerosis.

Background: Hepatocyte growth factor (HGF) is a pleiotropic cytokine mainly produced by mesenchymal cells. After endothelial damage by oxidized low-density lipoprotein (LDL), HGF is produced and released into the circulation in response. Due to this mechanism HGF has been proposed as possible clinical biomarker for clinical as well as subclinical atherosclerosis. Patients and methods: The conducted study is an observational, single centre, cohort study, including 171 patients with at least one cardiovascular risk factor or already established cardiovascular disease (CVD). Each patient underwent 3D plaque volumetry of the carotid and femoral arteries as well as physical examination and record of the medical history. Additionally, plasma HGF and further laboratory parameters like high sensitivity C-reactive protein and LDL-cholesterol were determined. Results: 169 patients were available for statistical analysis. In bivariate correlation, HGF showed a highly significant correlation with total plaque volume (TPV, r=0.48; p<0.001). In receiver operating characteristic (ROC) analysis for high TPV, HGF showed an area under the curve (AUC) of 0.68 (CI 95%: 0.59-0.77, p<0.001) with a sensitivity of 78% and a specificity of 52% to predict high TPV at a cut-off of 959 ng/ml. In the ROC-analysis for the presence of CVD, HGF demonstrated an AUC of 0.65 (95% CI 0.55-0.73; p=0.01) with a sensitivity of 77% and a specificity of 52%. Conclusions: Higher plasma levels of HGF are associated with higher atherosclerotic plaque volume as measured by 3D-ultrasound.

3D reconstruction of coronary artery bifurcations from intravascular ultrasound and angiography

Coronary bifurcation lesions represent a challenging anatomical subset, and the understanding of their 3D anatomy and plaque composition appears to play a key role in devising the optimal stenting strategy. This study proposes a new approach for the 3D reconstruction of coronary bifurcations and plaque materials by combining intravascular ultrasound (IVUS) and angiography. Three patient-specific silicone bifurcation models were 3D reconstructed and compared to micro-computed tomography (µCT) as the gold standard to test the accuracy and reproducibility of the proposed methodology. The clinical feasibility of the method was investigated in three diseased patient-specific bifurcations of varying anatomical complexity. The IVUS-based 3D reconstructed bifurcation models showed high agreement with the µCT reference models, with r2 values ranging from 0.88 to 0.99. The methodology successfully 3D reconstructed all the patient bifurcations, including plaque materials, in less than 60 min. Our proposed method is a simple, time-efficient, and user-friendly tool for accurate 3D reconstruction of coronary artery bifurcations. It can provide valuable information about bifurcation anatomy and plaque burden in the clinical setting, assisting in bifurcation stent planning and education.

An All-in-One Tool for 2D Atherosclerotic Disease Assessment and 3D Coronary Artery Reconstruction.

Diagnosis of coronary artery disease is mainly based on invasive imaging modalities such as X-ray angiography, intravascular ultrasound (IVUS) and optical coherence tomography (OCT). Computed tomography coronary angiography (CTCA) is also used as a non-invasive imaging alternative. In this work, we present a novel and unique tool for 3D coronary artery reconstruction and plaque characterization using the abovementioned imaging modalities or their combination. In particular, image processing and deep learning algorithms were employed and validated for the lumen and adventitia borders and plaque characterization at the IVUS and OCT frames. Strut detection is also achieved from the OCT images. Quantitative analysis of the X-ray angiography enables the 3D reconstruction of the lumen geometry and arterial centerline extraction. The fusion of the generated centerline with the results of the OCT or IVUS analysis enables hybrid coronary artery 3D reconstruction, including the plaques and the stent geometry. CTCA image processing using a 3D level set approach allows the reconstruction of the coronary arterial tree, the calcified and non-calcified plaques as well as the detection of the stent location. The modules of the tool were evaluated for efficiency with over 90% agreement of the 3D models with the manual annotations, while a usability assessment using external evaluators demonstrated high usability resulting in a mean System Usability Scale (SUS) score equal to 0.89, classifying the tool as "excellent".

Identifying vulnerable plaques: A 3D carotid plaque radiomics model based on HRMRI.

Identification of vulnerable carotid plaque is important for the treatment and prevention of stroke. In previous studies, plaque vulnerability was assessed qualitatively. We aimed to develop a 3D carotid plaque radiomics model based on high-resolution magnetic resonance imaging (HRMRI) to quantitatively identify vulnerable plaques. Ninety patients with carotid atherosclerosis who underwent HRMRI were randomized into training and test cohorts. Using the radiological characteristics of carotid plaques, a traditional model was constructed. A 3D carotid plaque radiomics model was constructed using the radiomics features of 3D T1-SPACE and its contrast-enhanced sequences. A combined model was constructed using radiological and radiomics characteristics. Nomogram was generated based on the combined models, and ROC curves were utilized to assess the performance of each model. 48 patients (53.33%) were symptomatic and 42 (46.67%) were asymptomatic. The traditional model was constructed using intraplaque hemorrhage, plaque enhancement, wall remodeling pattern, and lumen stenosis, and it provided an area under the curve (AUC) of 0.816 vs. 0.778 in the training and testing sets. In the two cohorts, the 3D carotid plaque radiomics model and the combined model had an AUC of 0.915 vs. 0.835 and 0.957 vs. 0.864, respectively. In the training set, both the radiomics model and the combination model outperformed the traditional model, but there was no significant difference between the radiomics model and the combined model. HRMRI-based 3D carotid radiomics models can improve the precision of detecting vulnerable carotid plaques, consequently improving risk classification and clinical decision-making in patients with carotid stenosis.

Correlation of cholesterol efflux capacity with femoral and carotid plaque volume measured by sonographic 3D plaque volumetry

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Österreichische Nationalbank Introduction Atherosclerosis is a systemic multifocal disease that can cause the narrowing and occlusion of arteries resulting in cardiovascular disease (CVD). Hypercholesterolemia plays a pivotal role in the pathogenesis of atherosclerotic plaques by the accumulation of cholesterol in the arterial wall. Cholesterol efflux mediated by HDL is capable of transporting cholesterol from the periphery back to the liver in a process called reverse cholesterol transport. Cholesterol efflux capacity (CEC) is inversely correlated with cardiovascular risk and proposed as a surrogate marker for reverse cholesterol transport. In this study, we set out to study a possible association between CEC and peripheral plaque volume. Methods Since lipid-lowering therapy interferes with CEC, we studied a subset of 176 patients (48.9% females) with a median age of 64 (IQR 57-70) without lipid-lowering medication that had been included in a study of 443 patients with at least one cardiovascular risk factor or established CVD. CETP-mediated cholesterol ester transfer was measured by quantifying the transfer of cholesterol ester from radiolabelled exogenous HDL to apoB-containing lipoproteins. CEC was determined using cAMP treated 3H-cholesterol-labeled J774 cells. Plaque volume in the carotid and the femoral artery was measured using a 3D ultrasound system equipped with semi-automatic software. Results We found a strong inverse correlation between CEC and high total plaque volume (p = 0.027) in patients without lipid-lowering therapy. On the other hand, there was no correlation between CETP-mediated cholesterol ester transfer (3h) and (16h), LDL- cholesterol, or lipoprotein(a) with total plaque volume. Conclusion CEC correlates inversely with peripheral atherosclerosis in patients not taking lipid-lowering therapy, further strengthening its role as a cardiovascular biomarker.

New 3-Dimensional Volumetric Ultrasound Method for Accurate Quantification of Atherosclerotic Plaque Volume

BackgroundCarotid and femoral plaque burden is a recognized biomarker of cardiovascular disease risk. A new electronic-sweep 3-dimensional (3D)–matrix transducer method can improve the functionality and image quality of vascular ultrasound atherosclerosis imaging. ObjectivesThis study aimed to validate this method for plaque volume measurement in early and intermediate–advanced plaques in the carotid and femoral territories. MethodsPlaque volumes were measured ex vivo in pig carotid and femoral artery specimens by 3-dimensional vascular ultrasound (3DVUS) using a 3D-matrix (electronic-sweep) transducer and its associated 3D plaque quantification software, and were compared with gold-standard histology. To test the clinical feasibility and accuracy of the 3D-matrix transducer, an experiment was conducted in intermediate–high risk individuals with carotid and femoral atherosclerosis. The results were compared with those obtained using the previously validated mechanical-sweep 3D transducer and established 2-dimensional (2D)–based plaque quantification software. ResultsIn the ex vivo study, the authors assessed 19 atherosclerotic plaques (plaque volume, 0.76 µL-56.30 μL), finding strong agreement between measurements with the 3D-matrix transducer and the histological gold-standard (intraclass correlation coefficient [ICC]: 0.992; [95% CI: 0.978-0.997]). In the clinical analysis of 20 patients (mean age 74.6 ± 4.45 years; 40% men), the authors found 64 (36 carotid and 28 femoral) of 80 scanned territories with atherosclerosis (measured atherosclerotic volume, 10 μL-859 μL). There was strong agreement between measurements made from electronic-sweep and mechanical-sweep 3DVUS transducers (ICC: 0.997 [95% CI: 0.995-0.998]). Agreement was also high between plaque volumes estimated by the 2D and 3D plaque quantification software applications (ICC: 0.999 [95% CI: 0.998-0.999]). Analysis time was significantly shorter with the 3D plaque quantification software than with the 2D multislice approach with a mean time reduction of 46%. Conclusions3DVUS using new matrix transducer technology, together with improved 3D plaque quantification software, simplifies the accurate volume measurement of early (small) and intermediate–advanced plaques located in carotid and femoral arteries.

Echolucent Carotid Plaques Becomes More Echogenic over Time – A 3D Ultrasound Study

Despite the presence of only a few established risk factors, some patients will experience atherosclerotic events. Therefore, methods for improved risk stratification for atherosclerotic events are wanted. We aimed to detect changes in carotid artery atherosclerotic plaque volume and echogenicity over time in patients with an acute thromboembolic event and in patients with chronic atherosclerotic disease, both treated with statin, using a novel 3D ultrasound system. We included two cohorts of patients; 70 patients, naïve to statin treatment, admitted with acute, first-time myocardial infarction (aMI), and 69 patients who had been on statin treatment for a minimum of 6 months with chronic peripheral arterial disease (cPAD). 3D ultrasound examination was performed at baseline and after 3 and 12 months. Plaque volume was quantified in 3D ultrasound plaque acquisitions, and echogenicity was assessed using grayscale median (GSM) and normalized with adventitia as reference. The aMI group had darker plaques than the cPAD group at baseline (mean GSM: 60.98, standard deviation (SD): 24.09 vs. 71.75, SD: 21.55; P=0.006), 3 months (63.64, SD: 20.47 vs. 73.44, SD: 20.46; P=0.006) and at 12 months follow-up (59.25, SD: 18.07 vs. 71.02, SD: 22.31; P=0.004). The differences were not significant after adjusting for traditional risk factors. Dividing both groups by the median GSM, the darkest half of the aMI group's had an increase in GSM mainly within the first 3 months (10.49, CI 95%: 2.45 to 18.53; P=0.012) and hereafter remained unchanged at 12 months follow-up (-0.53, CI 95%: -7.28 to 6.22, P=0.875). In the darkest cPAD group GSM also increased within 3 months (8.14, CI 95%: 1.85-14.32, P=0.012) and hereafter stabilized till 12 months (-2.54, CI 95%: -9.62 to 4.53, P=0.475). Plaque volume did not change in the aMI group from baseline (median: 55.41mm3, interquartile range (IQR): 24.24-84.31) to 12 months (58.67mm3, IQR: 31.81-93.51) (P=0.220) whereas there was a small decrease in the cPAD group from baseline (71.63mm3, IQR: 40.12-135.61) to 12 months (67.73mm3, IQR: 31.00-122.38) (P=0.026). Echolucent carotid plaque, assessed with the novel 3D matrix ultrasound system, had increasing GSM within 3 months period, indicating stabilization of the more vulnerable plaques in aMI and cPAD patients. Plaque volume decreased over 12 months follow-up in a long-term statin-treated patient with cPAD, but not during the first 12months statin therapy in patients with aMI.

High baseline fetuin-A levels are associated with lower atherosclerotic plaque progression as measured by 3D ultrasound

Background and aimsThe glycoprotein fetuin-A has anti-inflammatory effects, increases insulin resistance and plays an important role in calcium metabolism. The aim of our study was to assess the predictive value of fetuin-A on atherosclerotic plaque progression in comparison to the established cardiovascular biomarker high sensitivity C-reactive protein (hsCRP). MethodsIn this prospective, single center-, cohort study, we included 194 patients with at least one cardiovascular risk factor or established cardiovascular disease (CVD). Over a period of 4 years, each patient underwent 3D plaque volumetry of the carotid and femoral arteries on a yearly basis. To evaluate the predictive value of biomarkers in terms of plaque progression, the baseline values of fetuin-A and hsCRP were correlated with the plaque progression from baseline to the last follow up visit. Results171 patients were included in the final analysis. Baseline fetuin-A levels showed a significant negative correlation with plaque progression (r = −0.244; p = 0.001). In contrast, baseline hsCRP levels showed no correlation with plaque progression (r = 0.096, p = 0.20). In the ROC-analysis, fetuin-A had a significantly better predictive value than hsCRP (fetuin-A AUC 0.67; p = 0.001 vs hsCRP AUC 0.49; p = 0.88) with an optimal cut-off value at 712 μg/ml. In patients with high fetuin A levels (>712 μg/ml), a significantly lower plaque progression was observed compared to the group with low fetuin-A levels <712 μg/ml (high fetuin-A 197 mm3 vs. low fetuin-A 279 mm3; p = 0.01) ConclusionsHigher fetuin-A levels appear to predict lower atherosclerotic plaque progression in patients with or at risk of cardiovascular disease.

Deep learning reveals 3D atherosclerotic plaque distribution and composition

Complications of atherosclerosis are the leading cause of morbidity and mortality worldwide. Various genetically modified mouse models are used to investigate disease trajectory with classical histology, currently the preferred methodology to elucidate plaque composition. Here, we show the strength of light-sheet fluorescence microscopy combined with deep learning image analysis for characterising and quantifying plaque burden and composition in whole aorta specimens. 3D imaging is a non-destructive method that requires minimal ex vivo handling and can be up-scaled to large sample sizes. Combined with deep learning, atherosclerotic plaque in mice can be identified without any ex vivo staining due to the autofluorescent nature of the tissue. The aorta and its branches can subsequently be segmented to determine how anatomical position affects plaque composition and progression. Here, we find the highest plaque accumulation in the aortic arch and brachiocephalic artery. Simultaneously, aortas can be stained for markers of interest (for example the pan immune cell marker CD45) and quantified. In ApoE−/− mice we observe that levels of CD45 reach a plateau after which increases in plaque volume no longer correlate to immune cell infiltration. All underlying code is made publicly available to ease adaption of the method.

NGAL Correlates with Femoral and Carotid Plaque Volume Assessed by Sonographic 3D Plaque Volumetry

Background/Objectives: Inflammation represents a cornerstone in the development of atherosclerosis and early detection is essential to avoid cardiovascular events. Biomarkers like interleukin-1 beta, interleukin-6, or high sensitivity CRP (hs-CRP) have been investigated intensively in this field. Since they have several limitations, additional biomarkers are needed for cardiovascular risk stratification. The acute phase protein, neutrophil gelatinase-associated lipocalin (NGAL), modulates inflammation and is elevated in cardiovascular disease (CVD). Moreover, it contributes to plaque destabilization. Methods: In this prospective, single-center study, we included 323 asymptomatic patients with at least one cardiovascular risk factor or established CVD. NGAL levels were measured in plasma samples using a commercially available ELISA. Carotid, femoral, and total atherosclerotic plaque volumes (PV) were measured using a 3D ultrasound system (Philips iU22). Patients were separated into a low (n = 243) and high (n = 80) total PV group. Results: NGAL was significantly higher in patients with high total PV versus patients with low total PV. The NGAL amplitude for the prediction of high total PV was significantly higher when compared with hs-CRP. A high predictive value could also be observed for patients without established CVD. Conclusion: NGAL seems to be a promising biomarker for the identification of asymptomatic patients with atherosclerotic disease.

Three-dimensional ultrasonographic evaluation of carotid artery plaque surface irregularity.

IntroductionThe aim of this study was to evaluate 3-dimensional (3D) ultrasonography (US) in determining the surface irregularity of carotid artery plaques.Material and methodsThis study included 50 patients (20 females and 30 males) aged between 56 and 82 years with plaques in the carotid artery which were detected during routine neck ultrasound. Simultaneously these cases were evaluated in terms of plaque echogenicities and surface characteristics with 2D and 3D US.Results3D imaging was successfully performed in 45 of the 50 cases and the technical success rate was 90%. A single plaque was detected in 64.4% of the patients, with the remaining 35.6% having more than one plaque. The lengths of the plaques ranged from 2 to 12 mm (mean: 3.98 ±1.70 mm); the widths ranged from 1.8 to 3.2 mm (mean: 2.11 ±0.37 mm). No significant difference was found between 2D and 3D plaque echo-structures (observer 1, p = 0.317; observer 2, p = 0.276), but there were significant differences between 2D and 3D plaque surface irregularities (observer 1, p = 0.002; observer 2, p = 0.004). The inter-observer agreement on 2D and 3D plaque echo-structure and surface irregularity was very good (k coefficients were 0.89 and 0.83, respectively, for echo-structure, and 0.91 and 0.95, respectively, for surface irregularity).ConclusionsThe present study shows that 3D US examination is a valuable non-invasive method for investigation of surface irregularity of carotid artery plaques.

The Influence of Enhanced External Counterpulsation Intervention on the Biomechanical Stress Distribution of Advanced Plaque: A 3D FSI Study Based on in vivo Animal Experiment

Enhanced external counterpulsation (EECP) is an effective therapy to provide beneficial assistance for the failing heart by reducing cardiac afterload and increasing blood flow perfusion noninvasively. The technique of EECP involves the use of the EECP device to inflate and deflate a series of compression cuffs wrapped around the patient’s calves, lower thighs, and upper thighs. As the result, the enhanced flow perfusion is derived from the device’s propelling blood from veins of lower body to arteries of upper body and increases the blood supply for the important organs and brain. In the ACCF/AHA Guideline and ESC Guideline on the management of stable ischemic heart disease and coronary artery disease, EECP has been given a Class IIb and Class IIa recommendation respectively. In the ASA Guideline on the early management of Acute Ischemic stroke, EECP has been given a Class IIa recommendation. However, considering that EECP performance significantly elevates the acute blood pressure level as well as the perfusion level in systemic arterial tree and in diastolic, whether it will increase the risk of hypertension-related events such as atherosclerotic plaque rupture causes great concern in its clinical applications. But, the influence of EECP intervention on plaque progression remains elusive to this day and need to be assessed. It is generally agreed that biomechanical stresses play important roles in advanced atherosclerotic plaque progression and rupture. We hypothesized that EECP may intervene the advanced plaque progression via induced the variation of mechanical stresses in plaques. In this present paper, a pilot study containing animal experiment and numerical simulation was conducted to quantify the variations of biomechanical stresses of the plaque during EECP intervention. An experimentally induced hypercholesterolemic porcine model was developed and the basic hemodynamic measurements were performed in vivo before and during EECP intervention. Meanwhile, 3D multi-component idealized models with fluid-structure interactions (FSI) for carotid atherosclerotic plaques were introduced to solve the wall shear stress (WSS) and plaque structural stress (PWS) before and during intervention. Three cases of fibrous cap thickness (FC=600, 200 and 65μm) and three cases of material properties of the plaque components (normal, hard and soft) were involved in the current study. Numerical results showed that the max WSS level at the throat of the plaque, the 3D critical plaque wall stress (3D CPWS) level at the fibrous cap and the global max plaque wall stress (GMPWS) level at the shoulder of the plaque were all significantly augmented during EECP. When FC=65μm, EECP intervention augmented 118.1%±1.1% of the Max WSS level, 15.56%±1.68% of the 3D CPWS level and 14.78%±0.24% of the GMPWS level comparing to situations without EECP intervention. Considering that blood flow shear stress and structural stress are indexes that are presently thought might contribute to advanced plaque progression and its final rupture, our pilot study thus suggests that EECP treatment may intervene the plaque progression by elevating the levels of these indexes. But whether EECP treatment will increase the risk of plaque rupture and should be taken into account in its patient selection need a further detailed study and follow-up observation.

Influence of Traditional Cardiovascular Risk Factors on Carotid and Femoral Atherosclerotic Plaque Volume as Measured by Three-Dimensional Ultrasound.

Background: Atherosclerosis is a systemic multifocal disease with a preference for the branching points of the arteries. In this study, we quantitatively measured carotid and femoral plaque volume in subjects with cardiovascular risk factors (CVRF) and/or established atherosclerotic disease using a 3D ultrasound technique. Methods: In this prospective, single-centre study, we included 404 patients (median age 64; 56.9% men) with at least one CVRF or established cardiovascular disease. Plaque volume was measured using 3D ultrasound equipped with an automated software. Results: We found a strong correlation of plaque volume with CVRF and the number of vascular beds involved. The strongest associations with total and femoral plaque volume were noted for smoking, hypertension, age, as well as for the presence of peripheral arterial occlusive disease (p < 0.05). Carotid plaque volume was best predicted by hyperlipidaemia, hypertension, age, as well as the presence of cerebrovascular disease and coronary artery disease (p < 0.05). Conclusion: We conclude that smoking appears to be associated with total and femoral plaque volume, whereas hyperlipidaemia seems to be associated with carotid plaque volume. Measurement of 3D plaque volume is a practical and reproducible technique with the potential to become an additional screening tool in cardiovascular risk stratification.

InSilc: 3D Reconstruction and plaque characterization tool.

Coronary artery disease (CAD) is the leading cause of mortality in Europe and worldwide. Atherosclerosis is the most common pathologic process that is highly related with CAD, while the implantation of drug-eluting Bioresorbable Vascular Scaffolds (BVS) is the most promising procedure for treating patients with CAD. InSilc is an textbfin silico clinical trial (ISCT) platform for the development and assessment of drugeluting BVS. The InSilc platform provides insight in the performance of drug-eluting BVS in their short term and medium/long term through the Mechanical Modelling Module, the Deployment Module, the Fluid Dynamics Module, the Myocardial Perfusion Module, the Drug-delivery Module and the Degradation Module. In order for the aforementioned modules to be developed, the utilization of the reconstructed patient specific arterial segment and the BVS design are required, which is achieved through the 3D reconstruction and plaque characterization tool.In this study, the overall architecture of the InSilc platform is presented with special emphasis on the 3D reconstruction and plaque characterization tool. The tool will be able to implement different medical image processing workflows. The workflows will require minimum user intervention in order to be used in large scale clinical trials.

Carotid plaque segmentation from three-dimensional ultrasound images by direct three-dimensional sparse field level-set optimization

Total plaque volume (TPV) measured from 3D carotid ultrasound has been shown to be able to predict cardiovascular events and is sensitive in detecting treatment effects. Manual plaque segmentation was performed in previous studies to quantify TPV, but is tedious, requires long training times and is prone to observer variability. This article introduces the first 3D direct volume-based level-set algorithm to segment plaques from 3D carotid ultrasound images. The plaque surfaces were first initialized based on the lumen and outer wall boundaries generated by a previously described semi-automatic algorithm and then deformed by a direct three-dimensional sparse field level-set algorithm, which enforced the longitudinal continuity of the segmented plaque surfaces. This is a marked advantage as compared to a previously proposed 2D slice-by-slice plaque segmentation method. In plaque boundary initialization, the previous technique performed a search on lines connecting corresponding point pairs of the outer wall and lumen boundaries. A limitation of this initialization strategy was that an inaccurate initial plaque boundary would be generated if the plaque was not enclosed entirely by the wall and lumen boundaries. A mechanism is proposed to extend the search range in order to capture the entire plaque if the outer wall boundary lies on a weak edge in the 3D ultrasound image. The proposed method was compared with the previously described 2D slice-by-slice plaque segmentation method in 26 three-dimensional carotid ultrasound images containing 27 plaques with volumes ranging from 12.5 to 450.0 mm3. The manually segmented plaque boundaries serve as the surrogate gold standard. Segmentation accuracy was quantified by volume-, area- and distance-based metrics, including absolute plaque volume difference (|ΔPV|), Dice similarity coefficient (DSC), mean and maximum absolute distance (MAD and MAXD). The proposed direct 3D plaque segmentation algorithm was associated with a significantly lower |ΔPV|, MAD and MAXD, and a significantly higher DSC compared to the previously described slice-by-slice algorithm (|ΔPV|:p=0.012, DSC: p=2.1×10−4, MAD: p=1.3×10−4, MAXD: p=5.2×10−4). The proposed 3D volume-based algorithm required 72±22 s to segment a plaque, which is 40% lower than the 2D slice-by-slice algorithm (114±18 s). The proposed automatic plaque segmentation method generates accurate and reproducible boundaries efficiently and will allow for streamlining plaque quantification based on 3D ultrasound images.

3D Fiber Orientation in Atherosclerotic Carotid Plaques.

Atherosclerotic plaque rupture is the primary trigger of fatal cardiovascular events. Fibrillar collagen in atherosclerotic plaques and their directionality are anticipated to play a crucial role in plaque rupture. This study aimed assessing 3D fiber orientations and architecture in atherosclerotic plaques for the first time. Seven carotid plaques were imaged ex-vivo with a state-of-the-art Diffusion Tensor Imaging (DTI) technique, using a high magnetic field (9.4Tesla) MRI scanner. A 3D spin-echo sequence with uni-polar diffusion sensitizing pulsed field gradients was utilized for DTI and fiber directions were assessed from diffusion tensor measurements. The distribution of the 3D fiber orientations in atherosclerotic plaques were quantified and the principal fiber orientations (circumferential, longitudinal or radial) were determined. Overall, 52% of the fiber orientations in the carotid plaque specimens were closest to the circumferential direction, 34% to the longitudinal direction, and 14% to the radial direction. Statistically no significant difference was measured in the amount of the fiber orientations between the concentric and eccentric plaque sites. However, concentric plaque sites showed a distinct structural organization, where the principally longitudinally oriented fibers were closer to the luminal side and the principally circumferentially oriented fibers were located more abluminally. The acquired unique information on 3D plaque fiber direction will help understanding pathobiological mechanisms of atherosclerotic plaque progression and pave the road to more realistic biomechanical plaque modeling for rupture assessment.

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.

Abstract WP215: Role of Conventional Mri Brain for Basilar Artery Plaque Detection in Solitary Pontine Infarct

Background: Solitary pontine infarct is divided into paramedian pontine infarct (PPI) and small deep pontine infarct (SDPI). The novel high-resolution MRI is the current useful imaging method to characterize vessel walls and detect atherosclerotic plaques of the intracranial arteries. However, high-resolution MRI is not included in routine imaging protocol for patient with acute stroke. We intend to determine the role of conventional MRI and MRA of the brain in solitary pontine infarct. Material and Method: Fifty patients with pontine infarct undergo imaging study of MRI of the brain on T1-weighted image, T2-weighted image and post-gadolinium T1-weighted image (if available) to assess the presence of atherosclerotic plaque, and MRA of the brain using 3-dimensional time-of-flight MRA (3D TOF MRA) to assess the basilar artery luminography. Basilar artery assesses by axial T2-weighted image was scored as “presence of plaque” or “absence of plaque” and 3D TOF MRA of basilar artery is scored as “normal”, “irregular” or “stenosis” ≥ 30%. Pontine infarction is divided into paramedian pontine infarction (PPI) and small deep pontine infarction (SDPI) groups. Results: Fifty patients with pontine infarction are included, thirty-five with PPI and fifteen with SDPI. Conventional axial T2WI MRI of the brain detected basilar artery atherosclerotic plaques in about 50% of patients with pontine infarction: 51.4% (18 of 35 cases) in PPI and 46.7% (7 of 15 cases) in SDPI. No plaque is found in all cases of normal-appearing basilar luminography on 3D TOF MRA and plaque was identified in all patients with basilar artery stenosis on 3D TOF MRA. Conclusion: Basilar artery atherosclerotic branch disease is frequently detected in both groups of solitary pontine infarct (PPI and SDPI). Conventional MRI and MRA of the brain are the useful imaging methods that may characterize intracranial vessel wall abnormalities and may be helpful in further study of intracranial arterial diseases and in comprehension of stroke mechanisms.

Three-Dimensional Carotid Plaque MR Imaging.

There has been significant progress made in 3-dimensional (3D) carotid plaque MR imaging techniques in recent years. Three-dimensional plaque imaging clearly represents the future in clinical use. With effective flow-suppression techniques, choices of different contrast weighting acquisitions, and time-efficient imaging approaches, 3D plaque imaging offers flexible imaging plane and view angle analysis, large coverage, multivascular beds capability, and even can be used in fast screening.