Quantitative MRI in cardiometabolic disease: From conventional cardiac and liver tissue mapping techniques to multi-parametric approaches

Cardiometabolic disease refers to the spectrum of chronic conditions that include diabetes, hypertension, atheromatosis, non-alcoholic fatty liver disease, and their long-term impact on cardiovascular health. Histological studies have confirmed several modifications at the tissue level in cardiometabolic disease. Recently, quantitative MR methods have enabled non-invasive myocardial and liver tissue characterization. MR relaxation mapping techniques such as T1, T1ρ, T2 and T2* provide a pixel-by-pixel representation of the corresponding tissue specific relaxation times, which have been shown to correlate with fibrosis, altered tissue perfusion, oedema and iron levels. Proton density fat fraction mapping approaches allow measurement of lipid tissue in the organ of interest. Several studies have demonstrated their utility as early diagnostic biomarkers and their potential to bear prognostic implications. Conventionally, the quantification of these parameters by MRI relies on the acquisition of sequential scans, encoding and mapping only one parameter per scan. However, this methodology is time inefficient and suffers from the confounding effects of the relaxation parameters in each single map, limiting wider clinical and research applications. To address these limitations, several novel approaches have been proposed that encode multiple tissue parameters simultaneously, providing co-registered multiparametric information of the tissues of interest. This review aims to describe the multi-faceted myocardial and hepatic tissue alterations in cardiometabolic disease and to motivate the application of relaxometry and proton-density cardiac and liver tissue mapping techniques. Current approaches in myocardial and liver tissue characterization as well as latest technical developments in multiparametric quantitative MRI are included. Limitations and challenges of these novel approaches, and recommendations to facilitate clinical validation are also discussed

Пористые ковалентные орагнические полимеры, используемые в люминисцентных методах анализа

В последнее время химическая промышленность развивается колоссальными темпами,вследствие чего активно растёт объём применяемых химических продуктов, которые в свою очередь приводят к загрязнению почвы, водных биологических систем и окружающей среды. Для контроля качества окружающей среды используются различные методы анализа, мы решили рассмотреть один из наиболее быстрых и чувствительных методов, люминесцентный. Поэтому мы решили получить пять различных образцов пористых ковалентных веществ, которые могут быть использованы, как анализаторы при люминесцентном методе

Prosthetic heart valve evaluation by magnetic resonance imaging

Objective: To evaluate the potential of magnetic resonance imaging (MRI) for evaluation of velocity fields downstream of prosthetic aortic valves. Furthermore, to provide comparative data from bileaflet aortic valve prostheses in vitro and in patients. Methods: A pulsatile flow loop was set up in a 7.0 Tesla MRI scanner to study fluid velocity data downstream of a 25 mm aortic bileaflet heart valve prosthesis. Three dimensional surface plots of velocity fields were displayed. In six NYHA class I patients blood velocity profiles were studied downstream of their St. Jude Medical aortic valves using a 1.5 Tesla MRI whole-body scanner. Blood velocity data were displayed as mentioned above. Results: Fluid velocity profiles obtained from in vitro studies 0.25 valve diameter downstream of the valve exhibited significant details about the cross sectional distribution of fluid velocities. This distribution completely reflected the valve design. Blood velocity profiles in humans were considerably smoother and in some cases skewed with the highest velocities toward the anterior-right ascending aortic wall. Conclusion: Display and interpretation of fluid and blood velocity data obtained downstream of prosthetic valves is feasible both in vitro and in vivo using the MRI technique. An in vitro model with a straight tube and the test valve oriented orthogonally to the long axis of the test tube does not entail fluid velocity profiles which are compatible to those obtained from humans, probably due to the much more complex human geometry, and variable alignment of the valve with the ascending aorta. With the steadily improving quality of MRI scanners this technique has significant potential for comparative in vitro and in vivo hemodynamic evaluation of heart valve

Monitoring Vascular Permeability and Remodeling After Endothelial Injury in a Murine Model Using a Magnetic Resonance Albumin-Binding Contrast Agent

Background-Despite the beneficial effects of vascular interventions, these procedures may damage the endothelium leading to increased vascular permeability and remodeling. Re-endothelialization of the vessel wall, with functionally and structurally intact cells, is controlled by endothelial nitric oxide synthase (NOS3) and is crucial for attenuating adverse effects after injury. We investigated the applicability of the albumin-binding MR contrast agent, gadofosveset, to noninvasively monitor focal changes in vascular permeability and remodeling, after injury, in NOS3-knockout (NOS3(-/-)) and wild-type (WT) mice in vivo.Methods and Results-WT and NOS3(-/-) mice were imaged at 7, 15, and 30 days after aortic denudation or sham-surgery. T-1 mapping (R-1=1/T-1, s(-1)) and delayed-enhanced MRI were used as measurements of vascular permeability (R-1) and remodeling (vessel wall enhancement, mm(2)) after gadofosveset injection, respectively. Denudation resulted in higher vascular permeability and vessel wall enhancement 7 days after injury in both strains compared with sham-operated animals. However, impaired re-endothelialization and increased neovascularization in NOS3(-/-) mice resulted in significantly higher R-1 at 15 and 30 days post injury compared with WT mice that showed re-endothelialization and lack of neovascularization (R-1 [s(-1)]=15 days: (-/-)(NOS3)4.02 [interquartile range, IQR, 3.77-4.41] versus (WT)2.39 [IQR, 2.35-2.92]; 30 days: (-/-)(NOS3)4.23 [IQR, 3.94-4.68] versus (WT)2.64 [IQR, 2.33-2.80]). Similarly, vessel wall enhancement was higher in NOS3(-/-) but recovered in WT mice (area [mm(2)]=15 days: (-/-)(NOS3)5.20 [IQR, 4.68-6.80] versus (WT)2.13 [IQR, 0.97-3.31]; 30 days: (-/-)(NOS3)7.35 [IQR, 5.66-8.61] versus (WT)1.60 [IQR, 1.40-3.18]). Ex vivo histological studies corroborated the MRI findings.Conclusions-We demonstrate that increased vascular permeability and remodeling, after injury, can be assessed noninvasively using an albumin-binding MR contrast agent and may be used as surrogate markers for evaluating the healing response of the vessel wall after injury.</p