Quantitative renal perfusion measurements in a rat model of acute kidney injury at 3T: testing inter- and intramethodical significance of ASL and DCE-MRI

OBJECTIVES

To establish arterial spin labelling (ASL) for quantitative renal perfusion measurements in a rat model at 3 Tesla and to test the diagnostic significance of ASL and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in a model of acute kidney injury (AKI).

MATERIAL AND METHODS

ASL and DCE-MRI were consecutively employed on six Lewis rats, five of which had a unilateral ischaemic AKI. All measurements in this study were performed on a 3 Tesla MR scanner using a FAIR True-FISP approach and a TWIST sequence for ASL and DCE-MRI, respectively. Perfusion maps were calculated for both methods and the cortical perfusion of healthy and diseased kidneys was inter- and intramethodically compared using a region-of-interest based analysis.

RESULTS/SIGNIFICANCE

Both methods produce significantly different values for the healthy and the diseased kidneys (P<0.01). The mean difference was 147±47 ml/100 g/min and 141±46 ml/100 g/min for ASL and DCE-MRI, respectively. ASL measurements yielded a mean cortical perfusion of 416±124 ml/100 g/min for the healthy and 316±102 ml/100 g/min for the diseased kidneys. The DCE-MRI values were systematically higher and the mean cortical renal blood flow (RBF) was found to be 542±85 ml/100 g/min (healthy) and 407±119 ml/100 g/min (AKI).

CONCLUSION

Both methods are equally able to detect abnormal perfusion in diseased (AKI) kidneys. This shows that ASL is a capable alternative to DCE-MRI regarding the detection of abnormal renal blood flow. Regarding absolute perfusion values, nontrivial differences and variations remain when comparing the two methods.

Freezing of glycerol-water mixtures under pressure

We investigated freezing of pure glycerol as well as glycerol-water (GW) mixtures with 3:1 and 3:2 volume fractions as a function of pressure in the 0-10 GPa range by ruby fluorescence spectroscopy and neutron scattering. We find that the glass transition pressure increases from 5.5 GPa for pure glycerol to 6.5 GPa for the 3:1 GW mixture, with unusually small pressure gradients above. For higher water concentrations close to 3:2, phase separation occurs above 2 GPa where most of the water is expelled in the form of ice VII. The results suggest that glycerol is able to effectively hydrogen bond not more than ≈2.5 H(2)O molecules per glycerol, which seems to support conclusions from molecular dynamics simulations. The data indicate that these fluids could become important as pressure transmitting media for neutron scattering in the 0-7 GPa range, including at low temperatures.

Pressure-induced polyamorphism in salty water

We investigated the metastable phase diagram of an ionic salt aqueous solution, LiCl:6D₂O, at high pressure and low temperature by neutron diffraction measurements and computer simulations. We show that the presence of salt triggers a stepwise transformation, under annealing at high pressure, to a new very high-density amorphous form. The transition occurs abruptly at 120 K and 2 GPa, is reversible, and is characterized by a sizeable enthalpy release. Simulations suggest that the polyamorphic transition is linked to a local structural reorganization of water molecules around the Li ions.

Establishment of a cross-European field site network in the ALARM project for assessing large-scale changes in biodiversity

The field site network (FSN) plays a central role in conducting joint research within all Assessing Large-scale Risks for biodiversity with tested Methods (ALARM) modules and provides a mechanism for integrating research on different topics in ALARM on the same site for measuring multiple impacts on biodiversity. The network covers most European climates and biogeographic regions, from Mediterranean through central European and boreal to subarctic. The project links databases with the European-wide field site network FSN, including geographic information system (GIS)-based information to characterise the test location for ALARM researchers for joint on-site research. Maps are provided in a standardised way and merged with other site-specific information. The application of GIS for these field sites and the information management promotes the use of the FSN for research and to disseminate the results. We conclude that ALARM FSN sites together with other research sites in Europe jointly could be used as a future backbone for research proposals.

Magnetic ordering in solid oxygen up to room temperature

Oxygen is the only elemental molecule which carries an electronic magnetic moment. As a consequence, the different solid phases encountered on cooling show various degrees of magnetic order, and similar behavior is expected under compression. Here we present neutron diffraction data which reveal the magnetic ordering under high pressure in the delta ("orange") phase, i.e., in the range 6-8 GPa and 20-240 K. We show that delta-O2 contains in total three different magnetic structures, all of them being antiferromagnetic and differing in the stacking sequence of O2 sheets along the c axis. This structural diversity can be explained by the quasi-two-dimensional nature of delta-O2 and the strong orientation dependence of the magnetic exchange interaction between O2 molecules. The results show that delta-O2 is a room temperature antiferromagnet.

Limitations of high urgency listing--ventricular assist device support in a neonate for 452 days

The Eurotransplant International Foundation in Leiden, the Netherlands, is responsible for mediation and allocation of organ donation procedures to its member countries Austria, Belgium, Croatia, Germany, Luxembourg, the Netherlands and Slovenia. To provide organs for the patients who require urgent transplantation, the "high urgent (HU)" status was introduced in 2001 in Germany . This new HU allocation system is applicable to neonates as well as adults. However, waiting times on HU status exceed several weeks to months. Therefore an increasing number of pediatric patients has to undergo implantation of a ventricular assist device (VAD). In the present report we discuss the current Eurotransplant heart allocation system for pediatric heart transplantation in the light of a neonate with 452 days on mechanical support. We compare the average waiting time of patients on HU status at our center and their outcome in 2007 and 2008 (Data obtained from Eurotransplant International Foundation). Waiting time on HU status in our center increased significantly from 2007 to 2008. Therefore more patients require VAD support as bridging to transplantation. The case of a neonate under long-term VAD support is an outstanding example of the negative effects of this development.

German disease management guidelines: surgical therapies for chronic heart failure

The German Disease Management Guideline "Chronic Heart Failure" intends to guide physicians working in the field of diagnosis and treatment of heart failure. The guideline provides a tool on the background of evidence based medicine. The following short review wants to give insights into the role of some surgical treatment options to improve heart failure, such as revascularization, ventricular reconstruction and aneurysmectomy, mitral valve reconstruction, ventricular assist devices and heart transplantation.