Effect of contrast material injection protocol on first-pass myocardial perfusion assessed by dual-energy dual-layer computed tomography

Background: Dual-energy dual-layer computed tomography (CT) scanners can provide useful tools, such as iodine maps and virtual monochromatic images (VMI), for the evaluation of myocardial perfusion defects. Data about the influence of acquisition protocols and normal values are still lacking. Methods: Clinically indicated coronary CT-angiographies performed between January-October 2018 in a single university hospital with dual-energy dual-layer CT (DE-DLCT) and different injection protocols were retrospectively evaluated. The two protocols were: 35 mL in patients <80 kg and 0.5 mL/kg in patients >80 kg at 2.5 mL/sec (group A) or double contrast dose at 5 mL/sec (group B). Patients with coronary stenosis >50% were excluded. Regions of interest were manually drawn on 16 myocardial segments and iodine concentration was measured in mg/mL. Signal-to-noise, contrast-to-noise ratios (CNR) and image noise were measured on conventional images and VMI. Results: A total of 30 patients were included for each protocol. With iodine concentrations of 1.38 +/- 0.41 mg/mL for protocol A and 2.07 +/- 0.73 mg/mL for protocol B, the two groups were significantly different (P<0.001). No significant iodine concentration differences were found between the 16 segments (P=0.47 and P=0.09 for group A and B respectively), between basal, mid and apical segments for group A and B (P=0.28 and P=0.12 for group A and B respectively) and between wall regions for group A (P=0.06 on normalised data). In group B, iodine concentration was significantly different between three wall regions [highest values for the lateral wall, median =2.03 (1.06) mg/mL]. Post-hoc analysis showed highest contrast-to-noise and signal-to-noise in VMI at 40 eV (P<0.05). Conclusions: Iodine concentration in left ventricular myocardium of patients without significant coronary artery stenosis varied depending on the injection protocol and appeared more heterogeneous in different wall regions at faster injection rate and greater iodine load. Signal-to-noise and contrast-to-noise gradually improved when decreasing VMI energy, although at the expenses of higher noise, demonstrating the potential of DE-DLCT to enhance objective image quality

Determination of the myocardial area at risk after reperfused acute myocardial infarction with different imaging techniques: cardiac magnetic resonance imaging, multidetector computed tomography and histopathological validation

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Prognostic significance of vascular and valvular calcifications in low- and high-gradient aortic stenosis

International audienceAims In low-gradient aortic stenosis (LGAS), the high valvulo-arterial impedance observed despite low valvular gradient suggests a high vascular load. Thoracic aortic calcifications (TACs) and valvular aortic calcifications (VACs) are, respectively, surrogates of aortic load and aortic valvular gradient. The aim of this study was to compare the respective contributions of TAC and VAC on 3-year cardiovascular (CV) mortality following TAVI in LGAS vs. high-gradient aortic stenosis (HGAS) patients. Methods and results A total of 1396 consecutive patients were included. TAC and VAC were measured on the pre-TAVI CT-scan. About 435 (31.2%) patients had LGAS and 961 (68.8%) HGAS. LGAS patients were more prone to have diabetes, coronary artery disease (CAD), atrial fibrillation (AF), and lower left ventricular ejection fraction (LVEF), P<0.05 for all. During the 3 years after TAVI, 245(17.8%) patients experienced CV mortality, 92(21.6%) in LGAS and 153(16.2%) in HGAS patients, P=0.018. Multivariate analysis adjusted for age, gender, diabetes, AF, CAD, LVEF, renal function, vascular access, and aortic regurgitation showed that TAC but not VAC was associated with CV mortality in LGAS, hazard ratio (HR) 1.085 confidence interval (CI) (1.019–1.156), P=0.011, and HR 0.713 CI (0.439–1.8), P=0.235; the opposite was observed in HGAS patients with VAC but not TAC being associated with CV mortality, HR 1.342 CI (1.034–1.742), P=0.027, and HR 1.015 CI (0.955–1.079), P=0.626. Conclusion TAC plays a major prognostic role in LGAS while VAC remains the key in HGAS patients. This confirms that LGAS is a complex vascular and valvular disease

Vascular blood flow reconstruction with contrast-enhanced computerized tomography

International audienceIn this work, we study the measurement of blood velocity with contrast-enhanced computed tomography. The transport equation is used as a constraint to obtain stable solutions. The inverse problem is formulated as an optimal control problem. The density of the contrast agent is reconstructed together with the flow field. The existence of a minimizer of the regularization functional and a local unicity are demonstrated. The inversion scheme is tested on a simple numerical phantom

Vascular blood flow reconstruction from tomographic projections with the adjoint method and receding optimal control strategy

International audienceIn this work, we study the measurement of blood velocity with contrast enhanced computed tomography. The inverse problem is formulated as an optimal control problem with the transport equation as constraint. The velocity field is reconstructed with a receding optimal control strategy and the adjoint method. The convergence of the method is fast

Gadolinium enhancement vs WSS and Oscillatory shear Index (OSI) in human carotid atherosclerosis by MRI and CFD: A preliminary Study

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Animal models of atherosclerosis and magnetic resonance imaging for monitoring plaque progression.

International audienceAtherosclerosis, the main cause of heart attack and stroke, is the leading cause of death in most modern countries. Preventing clinical events depends on a better understanding of the mechanism of atherosclerotic plaque destabilization. Our knowledge on the characteristics of vulnerable plaques in humans has grown past decades. Histological studies have provided a precise definition of high-risk lesions and novel imaging methods for human atherosclerotic plaque characterization have made significant progress. However the pathological mechanisms leading from stable lesions to the formation of vulnerable plaques remain uncertain and the related clinical events are unpredictable. An animal model mimicking human plaque destablization is required as well as an in vivo imaging method to assess and monitor atherosclerosis progression. Magnetic resonance imaging (MRI) is increasingly used for in vivo assessment of atherosclerotic plaques in the human carotids. MRI provides well-characterized morphological and functional features of human atherosclerotic plaque which can be also assessed in animal models. This review summarizes the most common species used as animal models for experimental atherosclerosis, the techniques to induce atherosclerosis and to obtain vulnerable plaques, together with the role of MRI for monitoring atherosclerotic plaques in animals

Comparison of five one-step reconstruction algorithms for spectral CT

International audienceOver the last decade, dual-energy CT scanners have gone from prototypes to clinically available machines, and spectral photon counting CT scanners are following. They require a specific reconstruction process, consisting of two steps: material decomposition and tomographic reconstruction. The two steps can be done 5 separately in either order, but in both cases, some information is lost along the way. As an alternative, "one-step inversion" methods have been proposed, which perform decomposition and reconstruction simultaneously. For most CT applications, reconstruction time is critical for practical usability, and one-step methods are typically 10 slower than their two-step counterparts. The goal of this paper is to provide an independent comparison of five one-step inversion algorithms, focused mainly on convergence speed, but also on memory footprint, stability, and ease of use. We adapted and implemented a Bayesian method which uses non-linear conjugate 15 gradient for minimization [1], three methods based on quadratic surrogates [2, 3, 4], and a primal-dual method based on MOCCA, a modified Chambolle-Pock algorithm [5]. Experiments were performed on both simulated and real data. Some of these methods can be accelerated by using µ-preconditioning, i.e. by performing 20 all internal computations not with the actual materials the object is made of, but with carefully chosen linear combinations of those. In this paper, we also evaluate the impact of three different µ-preconditioners on convergence speed. Our results show that the method of Mechlem et al. [4] is much faster than the others, while 25 being only slightly less stable and more complex: it requires less than 100 iterations, versus several thousands for other methods. It seems to be the only viable candidate for implementation into a real multi-energy scanner

Estimation de paramètres mécaniques de la paroi carotidienne par imagerie ultrasonore in vivo pour la détection précoce de comportements pathologiques

National audienceLes maladies cardiovasculaires représentent la première cause de mortalité dans les pays industrialisés. Il est donc important d'effectuer un diagnostic précoce, préférentiellement de manière non invasive, pour traiter une vaste population. Les propriétés mécaniques des artères, notamment la carotide, sont affectées par l'athérosclérose, et sont considérées comme de bons indicateurs d'une manifestation pathologique précoce. Le comportement de la paroi de la carotide au long du cycle cardiaque présente plusieurs phénomènes particuliers dont l'analyse par imagerie ultrasonore permet de remonter aux causes pathologiques. Ce travail s'intéresse à l'étude conjointe de ces paramètres mécaniques au long d'une séquence d'images échographiques. Nous considérons principalement la force de cisaillement longitudinale exercée par le sang sur la paroi, l'onde de pouls causée par l'effet de dilatation-contraction radiale, et la compression élastique des couches de l'artère. Notre approche trouve son originalité dans le fait qu'elle prend en compte conjointement plusieurs paramètres mécaniques obtenus in vivo et se destine prioritairement à une application clinique pratique pouvant fournir une aide au diagnostic. Les séquences d'images ultrasonores traitées sont des coupes longitudinales de la carotide commune acquises avec un échographe clinique. Nous effectuons une analyse spatio-temporelle en considérant que le mouvement de chaque point de la paroi est continu dans le temps et dans l'espace. Le déplacement est estimé précisément grâce à un algorithme de mise en correspondance de blocs déformables. En fonction des paramètres à estimer pour l'étude du déplacement des couches de la carotide, les tailles de blocs et de noyau utilisés sont déterminées de manière optimale. Un comportement pathologique peut finalement être détecté à partir des paramètres extraits en comparaison de la déformation attendue d'une artère saine