TY  - JOUR
A1  - Spitznagel, N.
A1  - Durig, T.
A1  - Zimanowski, B.
T1  - Trigger - and heat-transfer times measured during experimental molten-fuel-interactions
JF  - AIP Advances
N2  - A modified setup featuring high speed high resolution data and video recording was developed to obtain detailed information on trigger and heat transfer times during explosive molten fuel-coolant-interaction (MFCI). MFCI occurs predominantly in configurations where water is entrapped by hot melt. The setup was modified to allow direct observation of the trigger and explosion onset. In addition the influences of experimental control and data acquisition can now be more clearly distinguished from the pure phenomena. More precise experimental studies will facilitate the description of MFCI thermodynamics.
KW  - temperature measurement
KW  - data acquisition
KW  - heat transfer
KW  - expolsions
KW  - shock waves
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-128625
VL  - 3
IS  - 102126
ER  - 
TY  - JOUR
A1  - Tran-Gia, Johannes
A1  - Wech, Tobias
A1  - Bley, Thorsten
A1  - Köstler, Herbert
T1  - Model-Based Acceleration of Look-Locker T1 Mapping
JF  - PLoS One
N2  - Mapping the longitudinal relaxation time \(T_1\) has widespread applications in clinical MRI as it promises a quantitative comparison of tissue properties across subjects and scanners. Due to the long scan times of conventional methods, however, the use of quantitative MRI in clinical routine is still very limited. In this work, an acceleration of Inversion-Recovery Look-Locker (IR-LL) \(T_1\) mapping is presented. A model-based algorithm is used to iteratively enforce an exponential relaxation model to a highly undersampled radially acquired IR-LL dataset obtained after the application of a single global inversion pulse. Using the proposed technique, a \(T_1\) map of a single slice with 1.6mm in-plane resolution and 4mm slice thickness can be reconstructed from data acquired in only 6s. A time-consuming segmented IR experiment was used as gold standard for \(T_1\) mapping in this work. In the subsequent validation study, the model-based reconstruction of a single-inversion IR-LL dataset exhibited a \(T_1\) difference of less than 2.6% compared to the segmented IR-LL reference in a phantom consisting of vials with \(T_1\) values between 200ms and 3000ms. In vivo, the \(T_1\) difference was smaller than 5.5% in WM and GM of seven healthy volunteers. Additionally, the \(T_1\) values are comparable to standard literature values. Despite the high acceleration, all model-based reconstructions were of a visual quality comparable to fully sampled references. Finally, the reproducibility of the \(T_1\) mapping method was demonstrated in repeated acquisitions. In conclusion, the presented approach represents a promising way for fast and accurate \(T_1\) mapping using radial IR-LL acquisitions without the need of any segmentation.
KW  - algorithms
KW  - cerebrospinal fluid
KW  - NMR relaxation
KW  - data acquisition
KW  - relaxation (physics)
KW  - relaxation time
KW  - central nervous system
KW  - magnetic resonance imaging
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-126436
VL  - 10
IS  - 4
ER  - 
TY  - JOUR
A1  - Zeller, Mario
A1  - Müller, Alexander
A1  - Gutberlet, Marcel
A1  - Nichols, Thomas
A1  - Hahn, Dietbert
A1  - Köstler, Herbert
A1  - Bartsch, Andreas J.
T1  - Boosting BOLD fMRI by K-Space Density Weighted Echo Planar Imaging
JF  - PLoS ONE
N2  - Functional magnetic resonance imaging (fMRI) has become a powerful and influential method to non-invasively study neuronal brain activity. For this purpose, the blood oxygenation level-dependent (BOLD) effect is most widely used. T2* weighted echo planar imaging (EPI) is BOLD sensitive and the prevailing fMRI acquisition technique. Here, we present an alternative to its standard Cartesian recordings, i.e. k-space density weighted EPI, which is expected to increase the signal-to-noise ratio in fMRI data. Based on in vitro and in vivo pilot measurements, we show that fMRI by k-space density weighted EPI is feasible and that this new acquisition technique in fact boosted spatial and temporal SNR as well as the detection of local fMRI activations. Spatial resolution, spatial response function and echo time were identical for density weighted and conventional Cartesian EPI. The signal-to-noise ratio gain of density weighting can improve activation detection and has the potential to further increase the sensitivity of fMRI investigations.
KW  - data acquisition
KW  - density
KW  - echo planar imaging
KW  - functional magnetic resonance imaging
KW  - imaging techniques
KW  - matched filters
KW  - signal filtering
KW  - statistical data
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-97233
ER  -