Regional in vivo transit time measurements of aortic pulse wave velocity in mice with high-field CMR at 17.6 Tesla

<p>Abstract</p> <p>Background</p> <p>Transgenic mouse models are increasingly used to study the pathophysiology of human cardiovascular diseases. The aortic pulse wave velocity (PWV) is an indirect measure for vascular stiffness and a marker for cardiovascular risk.</p> <p>Results</p> <p>This study presents a cardiovascular magnetic resonance (CMR) transit time (TT) method that allows the determination of the PWV in the descending murine aorta by analyzing blood flow waveforms. Systolic flow pulses were recorded with a temporal resolution of 1 ms applying phase velocity encoding. In a first step, the CMR method was validated by pressure waveform measurements on a pulsatile elastic vessel phantom. In a second step, the CMR method was applied to measure PWVs in a group of five eight-month-old apolipoprotein E deficient (ApoE^(-/-)) mice and an age matched group of four C57Bl/6J mice. The ApoE^(-/-)group had a higher mean PWV (PWV = 3.0 ± 0.6 m/s) than the C57Bl/6J group (PWV = 2.4 ± 0.4 m/s). The difference was statistically significant (p = 0.014).</p> <p>Conclusions</p> <p>The findings of this study demonstrate that high field CMR is applicable to non-invasively determine and distinguish PWVs in the arterial system of healthy and diseased groups of mice.</p

Method to Increase Resource Efficiency in Production with the Use of MFCA

In order to decrease carbon emissions and to address the problem of resource scarcity, the production industry as major consumer of energy and resources is forced to act and increase the resource efficiency of their production lines. However, for production managers it is often hard to determine, how and where to start implementing efficiency measures to reach the highest positive impact. The Material Flow Cost Accounting (MFCA), a method that became increasingly important over the last years, has proven to be a suitable tool to visualize and assess resource waste with resulting CO2-emissions as well as costs. Though, a stringent approach, how to get from the completed MFCA to the identification of appropriate resource efficiency measures and how to evaluate the impact of these measures is lacking. This paper therefore presents a method to derive and implement resource efficiency measures in production with the use of MFCA to find hotspots. The method includes the goal definition for resource efficiency, the gathering of resource transparency of the production process with hotspot methods, the implementation of the MFCA itself and the systematic analysis of the gathered results. The method is applied in the two production lines of the Energy efficiency, Technology and Application center (ETA) and the Center for industrial Productivity (CiP) at Technical University of Darmstadt, where a representative product is produced within an agile production network

Fast retrospectively triggered local pulse-wave velocity measurements in mice with CMR-microscopy using a radial trajectory

Background The aortic pulse-wave velocity (PWV) is an important indicator of cardiovascular risk. In recent studies MRI methods have been developed to measure this parameter noninvasively in mice. Present techniques require additional hardware for cardiac and respiratory gating. In this work a robust self-gated measurement of the local PWV in mice without the need of triggering probes is proposed. Methods The local PWV of 6-months-old wild-type C57BL/6J mice (n=6) was measured in the abdominal aorta with a retrospectively triggered radial Phase Contrast (PC) MR sequence using the flow-area (QA) method. A navigator signal was extracted from the CMR data of highly asymmetric radial projections with short repetition time (TR=3 ms) and post-processed with high-pass and low-pass filters for retrospective cardiac and respiratory gating. The self-gating signal was used for a reconstruction of high-resolution Cine frames of the aortic motion. To assess the local PWV the volume flow Q and the cross-sectional area A of the aorta were determined. The results were compared with the values measured with a triggered Cartesian and an undersampled triggered radial PC-Cine sequence. Results In all examined animals a self-gating signal could be extracted and used for retrospective breath-gating and PC-Cine reconstruction. With the non-triggered measurement PWV values of 2.3±0.2 m/s were determined. These values are in agreement with those measured with the triggered Cartesian (2.4±0.2 m/s) and the triggered radial (2.3±0.2 m/s) measurement. Due to the strong robustness of the radial trajectory against undersampling an acceleration of more than two relative to the prospectively triggered Cartesian sampling could be achieved with the retrospective method. Conclusion With the radial flow-encoding sequence the extraction of a self-gating signal is feasible. The retrospective method enables a robust and fast measurement of the local PWV without the need of additional trigger hardware

Elektronik

Mikro- und nanoelektronische Schaltungen und Systeme fallen aufgrund der Gesamtabmessungen der Chips zwar zunächst nicht als Nanotechnologie ins Auge - Chips bestehen aber aus bis zu einigen Milliarden einzelner miteinander integrierter Bauelemente, die mittlerweile Abmessungen von bis unter 30 nm haben, bei Schichtdicken bis hinunter zu einem Nanometer. Die Herstellung, Funktionalität und Zuverlässigkeit mikro- und nanoelektronischer Systeme hängt von einer Vielzahl von Nanoeffekten ab. Insgesamt ist die Mikro- und Nanoelektronik für viele industrielle Branchen in Deutschland und Europa eine Schlüsselindustrie. Wegen der technologischen Komplexität erfordert die Forschung auf diesem Gebiet breite Kooperationen zwischen Industrie, Instituten und Universitäten. Fraunhofer-Institute wie das IISB und das ENAS tragen wesentlich zur Forschung und Anwendung in diesem Gebiet bei

Local versus global aortic pulse wave velocity in early atherosclerosis: An animal study in ApoE−/−^{-/-} mice using ultrahigh field MRI

Increased aortic stiffness is known to be associated with atherosclerosis and has a predictive value for cardiovascular events. This study aims to investigate the local distribution of early arterial stiffening due to initial atherosclerotic lesions. Therefore, global and local pulse wave velocity (PWV) were measured in ApoE$^{-/-}$ and wild type (WT) mice using ultrahigh field MRI. For quantification of global aortic stiffness, a new multi-point transit-time (TT) method was implemented and validated to determine the global PWV in the murine aorta. Local aortic stiffness was measured by assessing the local PWV in the upper abdominal aorta, using the flow/area (QA) method. Significant differences between age matched ApoE$^{-/-}$ and WT mice were determined for global and local PWV measurements (global PWV: ApoE$^{-/-}$: 2.7 ±0.2m/s vs WT: 2.1±0.2m/s, P<0.03; local PWV: ApoE$^{-/-}$: 2.9±0.2m/s vs WT: 2.2±0.2m/s, P<0.03). Within the WT mouse group, the global PWV correlated well with the local PWV in the upper abdominal aorta (R$^2$ = 0.75, P<0.01), implying a widely uniform arterial elasticity. In ApoE$^{-/-}$ animals, however, no significant correlation between individual local and global PWV was present (R$^2$ = 0.07, P = 0.53), implying a heterogeneous distribution of vascular stiffening in early atherosclerosis. The assessment of global PWV using the new multi-point TT measurement technique was validated against a pressure wire measurement in a vessel phantom and showed excellent agreement. The experimental results demonstrate that vascular stiffening caused by early atherosclerosis is unequally distributed over the length of large vessels. This finding implies that assessing heterogeneity of arterial stiffness by multiple local measurements of PWV might be more sensitive than global PWV to identify early atherosclerotic lesions