MR Vessel Wall Imaging for Atherosclerosis and Vasculitis

Conventional imaging modalities, such as computed tomography angiography, MR angiography, transcranial Doppler ultrasonography, and digital subtraction angiography, are utilized in evaluating intraluminal or intravascular pathology of the intracranial vessels. Limitations of luminal imaging techniques can lead to inaccurate diagnosis, evaluation, and risk stratification, as many cerebrovascular pathologies contain an extrinsic vessel wall component. Furthermore, vessel wall imaging can provide information regarding extent, treatment response, and biopsy targets for vasculitis cases. Overall, while vessel wall imaging can provide robust data regarding intracranial pathologies, further prospective, multicenter studies are required to improve diagnostic application and accuracy.

Wall permeability on magnetic resonance imaging is associated with intracranial aneurysm symptoms and wall enhancement

OBJECTIVES

Wall remodeling and inflammation accompany symptomatic unruptured intracranial aneurysms (UIAs). The volume transfer constant (Ktrans) of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) reflects UIA wall permeability. Aneurysmal wall enhancement (AWE) on vessel wall MRI (VWI) is associated with inflammation. We hypothesized that Ktrans is related to symptomatic UIAs and AWE.

METHODS

Consecutive patients with UIAs were prospectively recruited for 3-T DCE-MRI and VWI from January 2018 to March 2023. UIAs were classified as asymptomatic and symptomatic if associated with sentinel headache or oculomotor nerve palsy. Ktrans and AWE were assessed on DCE-MRI and VWI, respectively. AWE was evaluated using the AWE pattern and wall enhancement index (WEI). Spearman's correlation coefficient and univariate and multivariate analyses were used to assess correlations between parameters.

RESULTS

We enrolled 82 patients with 100 UIAs (28 symptomatic and 72 asymptomatic). The median Ktrans (2.1 versus 0.4 min-1; p < 0.001) and WEI (1.5 versus 0.4; p < 0.001) were higher for symptomatic aneurysms than for asymptomatic aneurysms. Ktrans (odds ratio [OR]: 1.60, 95% confidence interval [95% CI]: 1.01-2.52; p = 0.04) and WEI (OR: 3.31, 95% CI: 1.05-10.42; p = 0.04) were independent risk factors for symptomatic aneurysms. Ktrans was positively correlated with WEI (Spearman's coefficient of rank correlation (rs) = 0.41, p < 0.001). The combination of Ktrans and WEI achieved an area under the curve of 0.81 for differentiating symptomatic from asymptomatic aneurysms.

CONCLUSIONS

Ktrans may be correlated with symptomatic aneurysms and AWE. Ktrans and WEI may provide an additional value than the PHASES score for risk stratification of UIAs.

CLINICAL RELEVANCE STATEMENT

The volume transfer constant (Ktrans) from DCE-MRI perfusion is associated with symptomatic aneurysms and provides additional value above the clinical PHASES score for risk stratification of intracranial aneurysms.

KEY POINTS

• The volume transfer constant is correlated with intracranial aneurysm symptoms and aneurysmal wall enhancement. • Dynamic contrast-enhanced and vessel wall MRI facilitates understanding of the pathophysiological characteristics of intracranial aneurysm walls. • The volume transfer constant and wall enhancement index perform better than the traditional PHASES score in differentiating symptomatic aneurysms.

Refined imaging features of culprit plaques improve the prediction of recurrence in intracranial atherosclerotic stroke within the middle cerebral artery territory

Recurrence is a significant adverse outcome of ischemic stroke (IS), particularly in cases of intracranial arteriosclerosis (ICAS). In this study, we investigated the impact of imaging features of culprit plaque using high-resolution magnetic resonance vessel wall imaging (HR-MR-VWI) on the prediction of IS recurrence. A total of 86 patients diagnosed with ICAS-related IS within the middle cerebral artery (MCA) territory were included, of which 23.25% experienced recurrent IS within one year. Our findings revealed significant differences between the recurrence and non-recurrence groups in terms of age (p = 0.007), diabetes mellitus (p = 0.031), hyperhomocysteinemia (p = 0.021), artery-artery embolism (AAE) infarction (p = 0.019), prominent enhancement (p = 0.013), and surface irregularity of the culprit plaque (p = 0.009). Age (HR = 1.063, p = 0.005), AAE infarction (HR = 5.708, p = 0.008), and prominent enhancement of the culprit plaque (HR = 4.105, p = 0.025) were identified as independent risk factors for stroke recurrence. The areas under the receiver operating characteristic curve (AUCs) for predicting IS recurrence using clinical factors, conventional imaging findings, HR-MR-VWI plaque features, and a combination of clinical and conventional imaging models were 0.728, 0.645, 0.705, and 0.814, respectively. Notably, the combination model demonstrated superior predictive performance with an AUC of 0.870. Similarly, AUC of combination model for predicting IS recurrence in validation cohort which enrolled another 37 patients was 0.865. In conclusion, the presence of obvious enhancement in culprit plaque on HR-MR-VWI is a valuable factor in predicting IS recurrence in ICAS-related strokes within the MCA territory. Furthermore, our combination model, incorporating plaque features, exhibited improved prediction accuracy.

Motion detection and correction for carotid MRI using a markerless optical system

PURPOSE

Motion related artifact is a challenge for MRI, especially when imaging regions like the carotid artery where complex motion (abrupt and bulk motion) may occur. This study aims to develop a non-contact motion detection and correction system for carotid MRI using a markerless optical tracking system.

METHODS

The proposed markerless optical tracking system consisted of a cross-line laser, an MRI-compatible camera and plastic holders mounted inside the scanner bore. The neck motion of the subject can be captured by monitoring the change of the projected laser position in real-time. The system was used to correct both abrupt motion and bulk motion for carotid MRI. The abrupt motion (e.g. coughing) was compensated by discarding the corrupted k-space lines and re-estimating the missing lines using SPIRiT algorithm. The bulk motion was corrected by phase adjustment of k-space lines according to the measured 1D-translational bulk motion (along anterior-posterior direction) and optimized in-plane translation parameters. Ten volunteers underwent carotid MRI with real-time neck motion detection and retrospective motion correction. Artery sharpness, vessel wall thickness and overall image quality score were compared between the motion-corrupted image and motion-corrected images of different correction strategies.

RESULTS

Both the abrupt motion and the bulk motion during carotid scanning were successfully detected and corrected. The results of ten volunteers demonstrated significant improvement in carotid artery sharpness, vessel wall thickness measurement, and overall image quality score using the proposed markerless optical tracking system and motion correction strategies.

CONCLUSION

The proposed markerless structured light based motion detection and correction system can sensitively detect both abrupt and bulk motion during carotid MR scans. By correcting for both abrupt and bulk motion, vessel wall delineation was improved in carotid MR images, which could potentially facilitate carotid plaque identification and atherosclerosis diagnosis in the future.

Retinal vessel wall imaging using fluorescein angiography and adaptive optics imaging in acute branch retinal artery occlusion

PURPOSE

To report the retinal vessel wall changes in a patient with acute branch retinal artery occlusion with fundus fluorescein angiography and adaptive optics imaging.

METHODS

Retrospective, observational case.

CASE DESCRIPTION

A 49-year-old female with cardiac ailment complained of sudden onset superior field loss for 4 days in her right eye. Her presenting visual acuity in the right eye was 20/20, N6. She was diagnosed with right eye infero-temporal branch retinal artery occlusion. A golden-yellow, round coloured embolus was noted on clinical examination obstructing the temporal division of the inferior branch of central retinal artery. Patient underwent ocular massage, anterior chamber paracentesis and oral Acetazolamide (Tab. Diamox 250 mg QID) medications. Vessel wall changes were noted using fluorescein angiography and adaptive optics retinal imaging at presentation and 10-day follow-up visit.

CONCLUSION

This case highlights the importance of multimodal retinal imaging like fluorescein angiography and adaptive optics imaging in identifying and understanding the retinal vessel wall changes in the occluded vascular segment of the retina.

The mechanical and morphological properties of systemic and pulmonary arteries differ in the earth boa, a snake without ventricular pressure separation

The walls of the mammalian aorta and pulmonary artery are characterized by diverging morphologies and mechanical properties, which has been correlated with high systemic and low pulmonary blood pressures, as a result of intraventricular pressure separation. However, the relation between intraventricular pressure separation and diverging aortic and pulmonary artery wall morphologies and mechanical characteristics is not understood. The snake cardiovascular system poses a unique model for the study of this question, since representatives both with and without intraventricular pressure separation exist. In this study we perform uniaxial tensile testing on vessel samples taken from the aortas and pulmonary arteries of the earth boa, Acrantophis madagascariensis, a species without intraventricular pressure separation. We then compare these morphological and mechanical characteristics with samples from the ball python, Python regius, and the yellow anaconda, Eunectes notaeus, species with and without intraventricular pressure separation, respectively. Our data suggest that although the aortas and pulmonary arteries of A. madagascariensis respond similarly to the same intramural blood pressures, they diverge in morphology, and that this attribute extends to E. notaeus. In contrast, P. regius aortas and pulmonary arteries diverge both morphologically and in terms of their mechanical properties. Our data indicate that intraventricular pressure separation cannot fully explain diverging aortic and pulmonary artery morphologies. Following the Law of Laplace, we propose that pulmonary arteries of small luminal diameter represent a mechanism to protect the fragile pulmonary vasculature by reducing the blood volume that passes through, to which genetic factors may contribute more strongly than physiological parameters.

Intracranial aneurysm wall (in)stability-current state of knowledge and clinical perspectives

Intracranial aneurysm (IA), a local outpouching of cerebral arteries, is present in 3 to 5% of the population. Once formed, an IA can remain stable, grow, or rupture. Determining the evolution of IAs is almost impossible. Rupture of an IA leads to subarachnoid hemorrhage and affects mostly young people with heavy consequences in terms of death, disabilities, and socioeconomic burden. Even if the large majority of IAs will never rupture, it is critical to determine which IA might be at risk of rupture. IA (in)stability is dependent on the composition of its wall and on its ability to repair. The biology of the IA wall is complex and not completely understood. Nowadays, the risk of rupture of an IA is estimated in clinics by using scores based on the characteristics of the IA itself and on the anamnesis of the patient. Classification and prediction using these scores are not satisfying and decisions whether a patient should be observed or treated need to be better informed by more reliable biomarkers. In the present review, the effects of known risk factors for rupture, as well as the effects of biomechanical forces on the IA wall composition, will be summarized. Moreover, recent advances in high-resolution vessel wall magnetic resonance imaging, which are promising tools to discriminate between stable and unstable IAs, will be described. Common data elements recently defined to improve IA disease knowledge and disease management will be presented. Finally, recent findings in genetics will be introduced and future directions in the field of IA will be exposed.

The association between hemodynamics and wall characteristics in human intracranial aneurysms: a review

Hemodynamics plays a key role in the natural history of intracranial aneurysms (IAs). However, studies exploring the association between aneurysmal hemodynamics and the biological and mechanical characteristics of the IA wall in humans are sparse. In this review, we survey the current body of literature, summarize the studies' methodologies and findings, and assess the degree of consensus among them. We used PubMed to perform a systematic review of studies that explored the association between hemodynamics and human IA wall features using different sources. We identified 28 publications characterizing aneurysmal flow and the IA wall: 4 using resected tissues, 17 using intraoperative images, and 7 using vessel wall magnetic resonance imaging (MRI). Based on correlation to IA tissue, higher flow conditions, such as high wall shear stress (WSS) with complex pattern and elevated pressure, were associated with degenerated walls and collagens with unphysiological orientation and faster synthesis. MRI studies strongly supported that low flow, characterized by low WSS and high blood residence time, was associated with thicker walls and post-contrast enhancement. While significant discrepancies were found among those utilized intraoperative images, they generally supported that thicker walls coexist at regions with prolonged residence time and that thinner regions are mainly exposed to higher pressure with complex WSS patterns. The current body of literature supports a theory of two general hemodynamic-biologic mechanisms for IA development. One, where low flow conditions are associated with thickening and atherosclerotic-like remodeling, and the other where high and impinging flow conditions are related to wall degeneration, thinning, and collagen remodeling.

Evaluating renal arterial wall by non-enhanced 2D and 3D free-breathing black-blood techniques: Initial experience

OBJECTIVES

To evaluate the feasibility and reproducibility of 2D and 3D black-blood sequences in measuring morphology of renal arterial wall.

METHODS

The 2D and 3D imaging sequences used variable-refocusing-flip-angle and constant-low-refocusing-flip-angle turbo spin echo (TSE) readout respectively, with delicately selected black-blood scheme and respiratory motion trigger for free-breathing imaging. Fourteen healthy subjects and three patients with Takayasu arteritis underwent renal artery wall imaging with 3D double inversion recovery (DIR) TSE and 2D Variable Flip Angle-TSE (VFA-TSE) black-blood sequences at 3.0 T. Four healthy subjects were randomly selected for scan-rescan reproducibility experiments. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and morphology of arterial wall were measured and compared using paired-t-test or Wilcoxon signed-rank test between 2D and 3D sequences. The inter-observer, intra-observer and scan-rescan agreements of above measurements were determined using intraclass correlation coefficient (ICC).

RESULTS

The 2D and 3D imaging sequences showed similar morphological measurements (lumen area, wall area, mean wall thickness and maximum wall thickness) of renal arterial wall (all P > 0.05) and excellent agreement (ICC: 0.853-0.954). Compared to 2D imaging, 3D imaging exhibited significantly lower SNR_lumen (P < 0.01) and SNR_wall (P = 0.037), similar contrast-to-noise ratio (CNR) (P = 0.285), and higher CNR efficiency (CNR_eff) (P < 0.01). Both 2D and 3D imaging showed good to excellent inter-observer (ICC: 0.723-0.997), intra-observer (ICC: 0.749-0.996) and scan-rescan (ICC: 0.710-0.992) reproducibility in measuring renal arterial wall morphology, SNR and CNR, respectively.

CONCLUSIONS

Both high-resolution free-breathing 2D VFA-TSE and 3D DIR TSE black-blood sequences are feasible and reproducible in high-resolution renal arterial wall imaging. The 2D imaging has high SNR, whereas 3D imaging has high imaging efficiency.

Endothelial Progenitors in the Tumor Microenvironment

Tumor vascularization refers to the formation of new blood vessels within a tumor and is considered one of the hallmarks of cancer. Tumor vessels supply the tumor with oxygen and nutrients, required to sustain tumor growth and progression, and provide a gateway for tumor metastasis through the blood or lymphatic vasculature. Blood vessels display an angiocrine capacity of supporting the survival and proliferation of tumor cells through the production of growth factors and cytokines. Although tumor vasculature plays an essential role in sustaining tumor growth, it represents at the same time an essential way to deliver drugs and immune cells to the tumor. However, tumor vasculature exhibits many morphological and functional abnormalities, thus resulting in the formation of hypoxic areas within tumors, believed to represent a mechanism to maintain tumor cells in an invasive state.Tumors are vascularized through a variety of modalities, mainly represented by angiogenesis, where VEGF and other members of the VEGF family play a key role. This has represented the basis for the development of anti-VEGF blocking agents and their use in cancer therapy: however, these agents failed to induce significant therapeutic effects.Much less is known about the cellular origin of vessel network in tumors. Various cell types may contribute to tumor vasculature in different tumors or in the same tumor, such as mature endothelial cells, endothelial progenitor cells (EPCs), or the same tumor cells through a process of transdifferentiation. Early studies have suggested a role for bone marrow-derived EPCs; these cells do not are true EPCs but myeloid progenitors differentiating into monocytic cells, exerting a proangiogenic effect through a paracrine mechanism. More recent studies have shown the existence of tissue-resident endothelial vascular progenitors (EVPs) present at the level of vessel endothelium and their possible involvement as cells of origin of tumor vasculature.

Intra-arterial in-situ bevacizumab injection effect on angiogenesis. Results on a swine angiogenesis model

BACKGROUND AND PURPOSE

In this study we tested the effect of antiangiogenics on a swine angiogenesis model that shares some brain AVM histological characteristics. The objective was to determine bevacizumab effects on retia volumes and on vessels' wall.

MATERIALS AND METHODS

Fifteen pigs were divided into 3 groups: Five animals served as controls (group A), 5 animals underwent endovascular left external and common carotid artery occlusion (group B) and 5 animals underwent the same procedure and had an intra-arterial in-situ injection of bevacizumab (groupC) 2 months after the occlusion. A DSA associated with 3D-rotational angiography was performed at day 0 and at 3 months in all groups in order to measure rete mirabile volumes. The animals were sacrificed at 3 months and the retia were harvested for pathological and immunohistochemistry examinations.

RESULTS

All VEGF-A receptors were blocked at the site of injection and there was a local enhanced endothelial proliferation and apoptosis. The volume of the retia remained unchanged after the bevacizumab injection. Retia vessels presented comparable media thickness, higher endothelial proliferation and apoptosis after the anti-VEGF injection.

CONCLUSION

A single in-situ injection of bevacizumab in this swine angiogenesis model showed no change in retia volume and an extensive blockage of VEGF receptors at the site of injection one month later. Rete mirabile vessels presented comparable media thickness, higher endothelial proliferation and apoptosis after the anti-VEGF injection, suggesting that bevacizumab antiangiogenic effect does not fragilize vessel wall. More studies are needed to confirm these preliminary insights of in-situ antiangiogenic effect on vascular malformations.

Segmentation of carotid arterial walls using neural networks

BACKGROUND

Automated, accurate, objective, and quantitative medical image segmentation has remained a challenging goal in computer science since its inception. This study applies the technique of convolutional neural networks (CNNs) to the task of segmenting carotid arteries to aid in the assessment of pathology.

AIM

To investigate CNN’s utility as an ancillary tool for researchers who require accurate segmentation of carotid vessels.

METHODS

An expert reader delineated vessel wall boundaries on 4422 axial T2-weighted magnetic resonance images of bilateral carotid arteries from 189 subjects with clinically evident atherosclerotic disease. A portion of this dataset was used to train two CNNs (one to segment the vessel lumen and the other to segment the vessel wall) with the remaining portion used to test the algorithm’s efficacy by comparing CNN segmented images with those of an expert reader.

RESULTS

Overall quantitative assessment between automated and manual segmentations was determined by computing the DICE coefficient for each pair of segmented images in the test dataset for each CNN applied. The average DICE coefficient for the test dataset (CNN segmentations compared to expert’s segmentations) was 0.96 for the lumen and 0.87 for the vessel wall. Pearson correlation values and the intra-class correlation coefficient (ICC) were computed for the lumen (Pearson = 0.98, ICC = 0.98) and vessel wall (Pearson = 0.88, ICC = 0.86) segmentations. Bland-Altman plots of area measurements for the CNN and expert readers indicate good agreement with a mean bias of 1%-8%.

CONCLUSION

Although the technique produces reasonable results that are on par with expert human assessments, our application requires human supervision and monitoring to ensure consistent results. We intend to deploy this algorithm as part of a software platform to lessen researchers’ workload to more quickly obtain reliable results.

Assessment of quantitative methods for enhancement measurement on vessel wall magnetic resonance imaging evaluation of intracranial atherosclerosis

PURPOSE

Quantitative measures of vessel wall magnetic resonance imaging (vwMRI) for the evaluation of intracranial atherosclerotic disease (ICAD) offers standardization not available with previously used qualitative approaches that may be difficult to replicate.

METHODS

vwMRI studies performed to evaluate ICAD that had caused a stroke were analyzed. Two blinded reviewers qualitatively rated culprit lesions for the presence of enhancement on T1 delay alternating with nutation for tailored excitation (DANTE) SPACE images. At least 3 months later, quantitative analysis was performed of the same images, comparing lesion enhancement to reference structures. Cohen's kappa and intraclass correlation coefficients were calculated to assess agreement. Ratios of enhancement of lesions to references were compared to qualitative ratings.

RESULTS

Studies from 54 patients met inclusion criteria. A mean of 49 (90.7%) lesions were qualitatively rated as enhancing, with good inter-rater agreement (κ = 0.783). Among reference structure candidates, low infundibulum demonstrated the highest inter-rater agreement on pre- and post-contrast imaging. The ratio of percentage increase in plaque signal following contrast to the same measure in low infundibulum demonstrated the highest agreement with qualitative assessment, with highest agreement seen with a ratio of 0.8 set as a threshold (κ = 0.675).

CONCLUSION

Quantitative metrics can yield objective data to better standardize techniques and acceptance of vwMRI evaluation of ICAD. The low infundibulum had the highest inter-rater agreement on both pre- and post-contrast images and is best suited as a normally enhancing reference structure. Such quantitative techniques should be implemented in future research of vwMRI for the evaluation of ICAD.

Ex vivo vessel wall thickness measurements of the human circle of Willis using 7T MRI

BACKGROUND AND AIMS

MRI can detect intracranial vessel wall thickening before any luminal stenosis is present. Apart from representing a vessel wall lesion, wall thickening could also reflect normal (age-related) variations in vessel wall thickness present throughout the intracranial arterial vasculature. The aim of this study was to perform vessel wall thickness measurements of the major intracranial arteries in ex vivo circle of Willis (CoW) specimens using 7T MRI, to obtain more detailed information about wall thickness variations of the intracranial arteries.

METHODS

Fifteen human CoW specimens were scanned at 7T MRI with an ultrahigh-resolution T₁-weighted sequence. Five specimens were used for validation of MRI measurements with histology and evaluation of inter-rater reliability and agreement. The other 10 specimens from patients with (n = 5) and without (n = 5) cerebrovascular disease were used for vessel wall thickness measurements over the entire length of the major arterial segments of the CoW using MRI only.

RESULTS

MRI measurements showed excellent agreement with histology. Mean wall thickness varied from 0.45 to 0.66 mm, minimum wall thickness from 0.31 to 0.42 mm, maximum wall thickness from 0.52 to 0.86 mm, and normalized wall index from 0.64 to 0.75. On average, vessel walls were thicker for symptomatic patients compared to asymptomatic patients.

CONCLUSIONS

High-resolution MRI enables accurate measurement of vessel wall thickness in ex vivo CoW specimens. Vessel wall thickness measurements over the entire length of segments showed considerable variation both within and between arterial segments of patients.

Intracranial Vessel Wall Imaging with Magnetic Resonance Imaging: Current Techniques and Applications

Vessel wall magnetic resonance imaging (VW-MRI) is a modern imaging technique with expanding applications in the characterization of intracranial vessel wall pathology. VW-MRI provides added diagnostic capacity compared with conventional luminal imaging methods. This review explores the principles of VW-MRI and typical imaging features of various vessel wall pathologies, such as atherosclerosis, dissection, and vasculitis. Radiologists should be familiar with this important imaging technique, given its increasing use and future relevance to everyday practice.

Relationship between Automated Coronary Calcium Volumes and a Set of Manual Coronary Lumen Volume, Vessel Volume and Atheroma Volume in Japanese Diabetic Cohort

INTRODUCTION

A high degree of correlation exists between Coronary Artery Diseases (CAD) and calcification of the vessel wall. For Percutaneous Coronary Interventional (PCI) planning, it is essential to have an exact understanding of the extent to which calcium volume is correlated to the lumen, vessel, and atheroma volume regions in the coronary artery, which is unclear in recent studies.

AIM

Four automated Coronary Calcium Volume (aCCV) measurement methods {threshold, Fuzzy c-Means (FCM), K-means, and Hidden Markov Random Field (HMRF)} and its correlation with three manual (experts) coronary parameters namely: Coronary Vessel Volume (mCVV), Coronary Lumen Volume (mCLV), and Coronary Atheroma Volume (mCAV), was determined in a Japanese diabetic cohort.

MATERIALS AND METHODS

Intravascular Ultrasound (IVUS) image dataset from 19 patients (around 40,090 frames) was collected using 40 MHz IVUS catheter (Atlantis^® SR Pro, Boston Scientific^®, pullback speed of 0.5 mm/sec). The methodology consisted of automatically computing the calcium volume in the entire IVUS coronary videos using FCM, K-means, and HMRF based pixel classification and comparing it against the previously published threshold-based method. The Coefficient of Correlation (CC) was then established between the four aCCV and three manually (experts) coronary parameters: mCVV, mCLV, and mCAV computed using iMAP software Boston Scientific^®. Statistical tests (Two-tailed paired Student t-test, Wilcoxon signed rank test, Mann-Whitney test, Chi-square test, and Kolmogorov-Smirnov KS-test) were performed to demonstrate consistency, reliability, and accuracy of the proposed work.

RESULTS

Correlation coefficient of: (a) automated threshold-based volume; (b) automated FCM based volume; (c) automated K-means based volume; and (d) automated HMRF based volume and corresponding three manually (expert's) coronary parameters (mCLV, mCVV, mCAV) were: (0.51, 0.40, 0.48), (0.52, 0.38, 0.49), (0.56, 0.45, 0.52), and (0.57, 0.42, 0.56), respectively. The CC between age and haemoglobin was 0.50.

CONCLUSION

Automated coronary volume measurement using HMRF method is more accurate compared to threshold, FCM, and K-means-based method, since it is more strongly correlated with three expert's readings.

Vascular pentraxin 3 controls arterial thrombosis by targeting collagen and fibrinogen induced platelets aggregation

Aim

The long pentraxin PTX3 plays a non-redundant role during acute myocardial infarction, atherosclerosis and in the orchestration of tissue repair and remodeling during vascular injury, clotting and fibrin deposition. The aim of this work is to investigate the molecular mechanisms underlying the protective role of PTX3 during arterial thrombosis.

Methods and results

PTX3 KO mice transplanted with bone marrow from WT or PTX3 KO mice presented a significant reduction in carotid artery blood flow following FeCl₃ induced arterial thrombosis (− 80.36 ± 11.5% and − 95.53 ± 4.46%), while in WT mice transplanted with bone marrow from either WT or PTX3 KO mice, the reduction was less dramatic (− 45.55 ± 1.37% and − 53.39 ± 9.8%), thus pointing to a protective effect independent of a hematopoietic cell's derived PTX3. By using P-selectin/PTX3 double KO mice, we further excluded a role for P-selectin, a target of PTX3 released by neutrophils, in vascular protection played by PTX3. In agreement with a minor role for hematopoietic cell-derived PTX3, platelet activation (assessed by flow cytometric expression of markers of platelet activation) was similar in PTX3 KO and WT mice as were haemostatic properties. Histological analysis indicated that PTX3 localizes within the thrombus and the vessel wall, and specific experiments with the N-terminal and the C-terminal PTX3 domain showed the ability of PTX3 to selectively dampen either fibrinogen or collagen induced platelet adhesion and aggregation.

Conclusion

PTX3 interacts with fibrinogen and collagen and, by dampening their pro-thrombotic effects, plays a protective role during arterial thrombosis.

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PTX3 deficiency in non-hematopoietic cells results in increased arterial thrombosis.

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Defects in the PTX3-P-selectin axis are not responsible for increased arterial thrombosis.

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PTX3 might limit the pro-thrombotic potential of fibrinogen and collagen on platelets adhesion and aggregation.

Assessment of image features for vessel wall segmentation in intravascular ultrasound images

BACKGROUND

Intravascular ultrasound (IVUS) provides axial greyscale images, allowing the assessment of the vessel wall and the surrounding tissues. Several studies have described automatic segmentation of the luminal boundary and the media-adventitia interface by means of different image features.

PURPOSE

The aim of the present study is to evaluate the capability of some of the most relevant state-of-the-art image features for segmenting IVUS images. The study is focused on Volcano 20 MHz frames not containing plaque or containing fibrotic plaques, and, in principle, it could not be applied to frames containing shadows, calcified plaques, bifurcations and side vessels.

METHODS

Several image filters, textural descriptors, edge detectors, noise and spatial measures were taken into account. The assessment is based on classification techniques previously used for IVUS segmentation, assigning to each pixel a continuous likelihood value obtained using support vector machines (SVMs). To retrieve relevant features, sequential feature selection was performed guided by the area under the precision-recall curve (AUC-PR).

RESULTS

Subsets of relevant image features for lumen, plaque and surrounding tissues characterization were obtained, and SVMs trained with these features were able to accurately identify those regions. The experimental results were evaluated with respect to ground truth segmentations from a publicly available dataset, reaching values of AUC-PR up to 0.97 and Jaccard index close to 0.85.

CONCLUSION

Noise-reduction filters and Haralick's textural features denoted their relevance to identify lumen and background. Laws' textural features, local binary patterns, Gabor filters and edge detectors had less relevance in the selection process.

Feasibility of coronary artery wall thickening assessment in asymptomatic coronary artery disease using phase-sensitive dual-inversion recovery MRI at 3T

OBJECTIVES

The purpose of this study was to (a) investigate the image quality of phase-sensitive dual-inversion recovery (PS-DIR) coronary wall imaging in healthy subjects and in subjects with known coronary artery disease (CAD) and to (b) investigate the utilization of PS-DIR at 3T in the assessment of coronary artery thickening in subjects with asymptomatic but variable degrees of CAD.

MATERIALS AND METHODS

A total of 37 subjects participated in this institutional review board-approved and HIPAA-compliant study. These included 21 subjects with known CAD as identified on multidetector computed tomography angiography (MDCT). Sixteen healthy subjects without known history of CAD were included. All subjects were scanned using free-breathing PS-DIR magnetic resonance imaging (MRI) for the assessment of coronary wall thickness at 3T. Lumen-tissue contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR) and quantitative vessel parameters including lumen area and wall thickness were measured. Statistical analyses were performed.

RESULTS

PS-DIR was successfully completed in 76% of patients and in 88% of the healthy subjects. Phase-sensitive signed-magnitude reconstruction, compared to modulus-magnitude images, significantly improved lumen-tissue CNR in healthy subjects (26.73±11.95 vs. 14.65±9.57, P<.001) and in patients (21.45±7.61 vs. 16.65±5.85, P<.001). There was no difference in image CNR and SNR between groups. In arterial segments free of plaques, coronary wall was thicker in patients in comparison to healthy subjects (1.74±0.27 mm vs. 1.17±0.14 mm, P<.001), without a change in lumen area (4.51±2.42 mm2 vs. 5.71±3.11mm2, P=.25).

CONCLUSIONS

This is the first study to demonstrate the feasibility of successfully obtaining vessel wall images at 3T using PS-DIR in asymptomatic patients with known variable degrees of CAD as detected by MDCT. This was achieved with a fixed subject-invariant planning of blood signal nulling. With that limitation alleviated, PS-DIR coronary wall MRI is capable of detecting arterial thickening and positive arterial remodeling at 3T in asymptomatic CAD.