Radial volumetric imaging breath-hold examination (VIBE) with k-space weighted image contrast (KWIC) for dynamic gadoxetic acid (Gd-EOB-DTPA)-enhanced MRI of the liver: advantages over Cartesian VIBE in the arterial phase

To compare radial volumetric imaging breath-hold examination with k-space weighted image contrast reconstruction (r-VIBE-KWIC) to Cartesian VIBE (c-VIBE) in arterial phase dynamic gadoxetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (DCE-MRI) of the liver. We reviewed 53 consecutive DCE-MRI studies performed on a 3-T unit using c-VIBE and 53 consecutive cases performed using r-VIBE-KWIC with full-frame image subset (r-VIBEfull) and sub-frame image subsets (r-VIBEsub; temporal resolution, 2.5-3 s). All arterial phase images were scored by two readers on: (1) contrast-enhancement ratio (CER) in the abdominal aorta; (2) scan timing; (3) artefacts; (4) visualisation of the common, right, and left hepatic arteries. Mean abdominal aortic CERs for c-VIBE, r-VIBEfull, and r-VIBEsub were 3.2, 4.3 and 6.5, respectively. There were significant differences between each group (P < 0.0001). The mean score for c-VIBE was significantly lower than that for r-VIBEfull and r-VIBEsub in all factors except for visualisation of the common hepatic artery (P < 0.05). The mean score of all factors except for scan timing for r-VIBEsub was not significantly different from that for r-VIBEfull. Radial VIBE-KWIC provides higher image quality than c-VIBE, and r-VIBEsub features high temporal resolution without image degradation in arterial phase DCE-MRI. aEuro cent Radial VIBE-KWIC minimised artefact and produced high-quality and high-temporal-resolution images. aEuro cent Maximum abdominal aortic enhancement was observed on sub-frame images of r-VIBE-KWIC. aEuro cent Using r-VIBE-KWIC, optimal arterial phase images were obtained in over 90 %. aEuro cent Using r-VIBE-KWIC, visualisation of the hepatic arteries was improved. aEuro cent A two-reader study revealed r-VIBE-KWIC's advantages over Cartesian VIBE.ArticleEUROPEAN RADIOLOGY. 24(6):1290-1299 (2014)journal articl

(Accelerated) mass changes in the Siberian permafrost regions from GRACE

The Gravity Recovery and Climate Experiment (GRACE) satellite mission is now in orbit for more than 7 years. A number of studies regarding periodic signals as well as long-term trends have been carried out. Large scale mass variations have been detected in Greenland and Antarctica (due to ice melt) and North America Fennoscandia (due to glacial rebound). The long time span now also allows detecting smaller secular trends of mass variations as well as long-periodic signals. In our study, we address the permafrost-regime in Siberia, Russia, using the GRACE monthly solutions from the three main analysis centres GFZ, CSR and JPL and further institutions. Two major trends of about 0.5 µGal/yr can be clearly identified one concerning the lower Ob basin, the other centered in the Lena river watershed northeast of Lake Baikal. The observed trends show a different spatial and temporal behavior due to different climate and permafrost conditions. These trends could indicate long-term hydrological changes in the large Siberian watersheds of the Ob, Lena and Yenisei rivers. Earlier terrestrial investigations observe that discharge of Siberian rivers increased during low flow season, possibly caused by reactivation of groundwater as a result of permafrost degradation over the past decades. The GRACE data even indicate some accelerated mass changes in Siberia over the last 5 - 7 years. In this paper, we discuss the corresponding GRACE results and confront them with those from other investigations. Possible explanations for the mass variations in Siberia are given