Simultaneous Registration of Location and Orientation in Intravascular Ultrasound Pullbacks Pairs Via 3D Graph-Based Optimization.

A novel method is reported for simultaneous registration of location (axial direction) and orientation (circumferential direction) of two intravascular ultrasound (IVUS) pullbacks of the same vessel taken at different times. Monitoring plaque progression or regression (e.g., during lipid treatment) is of high clinical relevance. Our method uses a 3D graph optimization approach, in which the cost function jointly reflects similarity of plaque morphology and plaque/perivascular image appearance. Graph arcs incorporate prior information about temporal correspondence of the two IVUS sequences and limited angular twisting between consecutive IVUS images. Additionally, our approach automatically identifies starting and ending frame pairs in the two IVUS pullbacks. Validation of our method was performed in 29 pairs of IVUS baseline/follow-up pullback sequences consisting of 8 622 IVUS image frames in total. In comparison to manual registration by three experts, the average location and orientation registration errors ranged from 0.72 mm to 0.79 mm and from 7.3(°) to 9.3(°), respectively, all close to the inter-observer variability with no difference being statistically significant (p = NS). Rotation angles determined by our automated approach and expert observers showed high correlation (r(2) of 0.97 to 0.98) and agreed closely (mutual bias between the automated method and expert observers ranged from -1.57(°) to 0.15(°)). Compared with state-of-the-art approaches, the new method offers lower errors in both location and orientation registration. Our method offers highly automated and accurate IVUS pullback registration and can be employed in IVUS-based studies of coronary disease progression, enabling more focal studies of coronary plaque development and transition of vulnerability.

Standardized evaluation methodology and reference database for evaluating IVUS image segmentation.

This paper describes an evaluation framework that allows a standardized and quantitative comparison of IVUS lumen and media segmentation algorithms. This framework has been introduced at the MICCAI 2011 Computing and Visualization for (Intra)Vascular Imaging (CVII) workshop, comparing the results of eight teams that participated. We describe the available data-base comprising of multi-center, multi-vendor and multi-frequency IVUS datasets, their acquisition, the creation of the reference standard and the evaluation measures. The approaches address segmentation of the lumen, the media, or both borders; semi- or fully-automatic operation; and 2-D vs. 3-D methodology. Three performance measures for quantitative analysis have been proposed. The results of the evaluation indicate that segmentation of the vessel lumen and media is possible with an accuracy that is comparable to manual annotation when semi-automatic methods are used, as well as encouraging results can be obtained also in case of fully-automatic segmentation. The analysis performed in this paper also highlights the challenges in IVUS segmentation that remains to be solved.

The prediction of coronary artery disease based on non-invasive examinations and heme oxygenase 1 polymorphism versus virtual histology.

OBJECTIVE: Prediction of coronary atherosclerosis in patients with stable angina based on non-invasive examinations. METHODS: Pro-inflammatory markers, heme oxygenase-1 (HO-1) polymorphism, lipid levels, Framingham risk score (FRS), and carotid ultrasound were analyzed and compared to grayscale and virtual histology intravascular ultrasound (VH-IVUS). RESULTS: A total of 101 patients were included, and genetic analysis was performed on 81 patients (80.2%). The HO-1 risk polymorphism was more frequent in patients post-myocardial infarction (61.3% vs 32%; P=.0097), or with diabetes (68.4% vs 35.5%; P=.011) or a higher FRS (21.5 vs 15.7; P=.014). Plaques in patients with the HO-1 risk polymorphism contained less fibro-fatty tissue (17.1% vs 23.2%; P=.005) and more necrotic core (NC; 17.1% vs 12.7%; P=.02) and calcification (10.2% vs 5.7%; P=.035) compared to patients without the HO-1 risk polymorphism. Carotid intima media thickness (P=.05) and carotid bulb plaque (P=.008) predicted plaque burden. The level of Apo A inversely correlated with NC (P=.047; r = -0.27) and was lower in patients with VH-thin-cap fibroatheroma (VH-TCFA; 1.19 mmol/L vs 1.3 mmol/L; P=.04). FRS correlated with NC (P=.007; r = 0.2), with angiographic disease severity (P=.032; r = 0.21) and was higher in patients with VH-TCFA (9.1 vs 7.8; P=.03). CONCLUSION: Carotid ultrasound and HO-1 polymorphism improve coronary atherosclerosis prediction.

Virtual histology evaluation of atherosclerosis regression during atorvastatin and ezetimibe administration: HEAVEN study.

BACKGROUND: There is no study focusing on changes in coronary atherosclerosis during dual lipid-lowering therapy with statin and ezetimibe. METHODS AND RESULTS: Eighty-nine patients with stable angina randomized in a 1:1 ratio to Group A (aggressive therapy: atorvastatin 80mg, ezetimibe 10mg) and Group S (standard therapy) were analyzed. Treatment period was 12 months. Coronary arteries were examined by intravascular ultrasound and virtual histology. We found a decrease in the percent atheroma volume (PAV) (-0.4%) in Group A compared with an increase (+1.4%) in Group S (P=0.014) and this was accompanied by an increased frequency of combined atherosclerosis regression (increased lumen volume+decreased PAV) in group A (40.5%) compared with group S (14.9%) (P=0.007). The target low-density lipoprotein cholesterol level <2mmol/L, presence of at least 4 of 5 atherosclerotic risk factors, and decreased level of vascular cellular adhesive molecule were independent predictors of plaque regression. There were no significant differences in plaque composition between the 2 groups over the study duration. However, during analysis of the 2 groups together, fibrous and fibro-fatty tissues decreased and dense calcification and necrotic core increased during follow-up. CONCLUSIONS: Dual lipid-lowering therapy starts atherosclerosis regression, but does not lead to significant changes in plaque composition. The continuous shift in plaque from fibro and fibro-fatty to necrotic with calcification was present in both groups.

IVUS-based assessment of 3D morphology and virtual histology: prediction of atherosclerotic plaque status and changes.

Comprehensive analysis of coronary morphology, plaque composition, hemodynamics, and systemic cardiovascular biomarkers is hypothesized to allow prediction of plaque development. We report the status of a comprehensive project, in which baseline and follow-up intravascular ultrasound imaging of coronary arteries during routine coronary interventions serve as a source of quantitative data for development of a predictive classifier for determining plaque progression over the course of a year from baseline data.