Schönau am Königssee, Germany
Schönau am Königssee, Germany

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Fuchs J.,University of Würzburg | Neuberger T.,Pennsylvania State University | Rolletschek H.,Leibniz Institute of Plant Genetics and Crop Plant Research | Schiebold S.,Leibniz Institute of Plant Genetics and Crop Plant Research | And 7 more authors.
Plant Physiology | Year: 2013

While often thought of as a smoking drug, tobacco (Nicotiana spp.) is now considered as a plant of choice for molecular farming and biofuel production. Here, we describe a noninvasive means of deriving both the distribution of lipid and the microtopology of the submillimeter tobacco seed, founded on nuclear magnetic resonance (NMR) technology. Our platform enables counting of seeds inside the intact tobacco capsule to measure seed sizes, to model the seed interior in three dimensions, to quantify the lipid content, and to visualize lipid gradients. Hundreds of seeds can be simultaneously imaged at an isotropic resolution of 25 mm, sufficient to assess each individual seed. The relative contributions of the embryo and the endosperm to both seed size and total lipid content could be assessed. The extension of the platform to a range of wild and cultivated Nicotiana species demonstrated certain evolutionary trends in both seed topology and pattern of lipid storage. The NMR analysis of transgenic tobacco plants with seed-specific ectopic expression of the plastidial phosphoenolpyruvate/phosphate translocator, displayed a trade off between seed size and oil concentration. The NMR-based assay of seed lipid content and topology has a number of potential applications, in particular providing a means to test and optimize transgenic strategies aimed at the manipulation of seed size, seed number, and lipid content in tobacco and other species with submillimeter seeds.

Borisjuk L.,Leibniz Institute of Plant Genetics and Crop Plant Research | Neuberger T.,Pennsylvania State University | Schwender J.,Brookhaven National Laboratory | Heinzel N.,Leibniz Institute of Plant Genetics and Crop Plant Research | And 11 more authors.
Plant Cell | Year: 2013

Constrained to develop within the seed, the plant embryo must adapt its shape and size to fit the space available. Here, we demonstrate how this adjustment shapes metabolism of photosynthetic embryo. Noninvasive NMR-based imaging of the developing oilseed rape (Brassica napus) seed illustrates that, following embryo bending, gradients in lipid concentration became established. These were correlated with the local photosynthetic electron transport rate and the accumulation of storage products. Experimentally induced changes in embryo morphology and/or light supply altered these gradients and were accompanied by alterations in both proteome and metabolome. Tissue-specific metabolic models predicted that the outer cotyledon and hypocotyl/radicle generate the bulk of plastidic reductant/ATP via photosynthesis, while the inner cotyledon, being enclosed by the outer cotyledon, is forced to grow essentially heterotrophically. Under field-relevant highlight conditions, major contribution of the ribulose-1,5-bisphosphate carboxylase/oxygenase-bypass to seed storage metabolism is predicted for the outer cotyledon and the hypocotyl/radicle only. Differences between in vitro- versus in planta-grown embryos suggest that metabolic heterogeneity of embryo is not observable by in vitro approaches. We conclude that in vivo metabolic fluxes are locally regulated and connected to seed architecture, driving the embryo toward an efficient use of available light and space. © 2013 American Society of Plant Biologists. All rights reserved.

Seiberlich N.,University Hospitals of Cleveland | Lee G.,University Hospitals of Cleveland | Ehses P.,Research Center Magnetic Resonance Bavaria | Duerk J.L.,University Hospitals of Cleveland | And 4 more authors.
Magnetic Resonance in Medicine | Year: 2011

Previous work has shown that the use of radial GRAPPA for the reconstruction of undersampled real-time free-breathing cardiac data allows for frame rates of up to 30 images/s. It is well known that the spiral trajectory offers a higher scan efficiency compared to radial trajectories. For this reason, we have developed a novel through-time spiral GRAPPA method and demonstrate its application to real-time cardiac imaging. By moving from the radial trajectory to the spiral trajectory, the temporal resolution can be further improved at lower acceleration factors compared to radial GRAPPA. In addition, the image quality is improved compared to those generated using the radial trajectory due to the lower acceleration factor. Here, we show that 2D frame rates of up to 56 images/s can be achieved using this parallel imaging method with the spiral trajectory. Copyright © 2011 Wiley Periodicals, Inc.

Blaimer M.,Research Center Magnetic Resonance Bavaria | Choli M.,Research Center Magnetic Resonance Bavaria | Jakob P.M.,Research Center Magnetic Resonance Bavaria | Griswold M.A.,Case Western Reserve University | Breuer F.A.,Research Center Magnetic Resonance Bavaria
Magnetic Resonance in Medicine | Year: 2013

Purpose: Parallel MRI methods are typically associated with a degradation of the signal-to-noise ratio (SNR). High scan time reduction factors are therefore restricted to applications with high intrinsic SNR. One possibility to increase the intrinsic SNR is to simultaneously excite several slices by means of multiband radio-frequency (RF) pulses and subsequently separate the slices by parallel MRI reconstruction algorithms. However, the separation of closely spaced slices may suffer from severe noise amplification when there is insufficient coil sensitivity variation along the slice direction. The purpose of this work is to apply a phase-constrained reconstruction for multiband experiments to minimize the noise amplification. Methods: Pre-defined phase differences between neighboring slices are induced and slice separation is performed by a phase-constrained parallel MRI reconstruction. Phase differences between neighboring slices are tailored to achieve optimal slice separation with minimized noise amplification. The potential of the method is demonstrated through multiband in-vivo experiments. Results: Noise amplification in multiband phase-constrained reconstructions is significantly reduced in comparison to standard multiband reconstruction when the phase difference between neighboring slices (distance = 12 mm) is 90°. Conclusions: Multiband phase-constrained parallel MRI has the potential for accelerated multi-slice imaging with an improved SNR performance. © 2013 Wiley Periodicals, Inc.

Michalska M.,University of Würzburg | MacHtoub L.,Innsbruck Medical University | Manthey H.D.,University of Würzburg | Bauer E.,Universitatsklinik Wurzburg | And 9 more authors.
Arteriosclerosis, Thrombosis, and Vascular Biology | Year: 2012

OBJECTIVE-: Noninvasive imaging of atherosclerosis remains challenging in clinical applications. Here, we applied noninvasive molecular imaging to detect vascular cell adhesion molecule-1 in early and advanced atherosclerotic lesions of apolipoprotein E-deficient mice. METHODS AND RESULTS-: Ultrasmall superparamagnetic iron oxide particles functionalized with (P03011) or without (P3007) vascular cell adhesion molecule-1-binding peptide were visualized by ultra high-field (17.6 T) magnetic resonance. Injection of P03011 resulted in a marked signal loss in the aortic root of apolipoprotein E-deficient mice fed a Western diet for 8 and 26 weeks in vivo and ex vivo, compared with preinjection measurements, P3007-injected mice, and P03011-or P3007-injected age-matched C57BL/6 controls. Histological analyses revealed iron accumulations in the intima, in colocalization with vascular cell adhesion molecule-1-expressing macrophages and endothelial cells. Coherent anti-Stokes Raman scattering microscopy demonstrated iron signals in the intima and media of the aortic root in the P03011-injected but not untreated apolipoprotein E-deficient mice, localized to macrophages, luminal endothelial-like cells, and medial regions containing smooth muscle cells. Electron microscopy confirmed iron particles enclosed in endothelial cells and in the vicinity of smooth muscle cells. CONCLUSION-: Using a combination of innovative imaging modalities, in this study, we demonstrate the feasibility of applying P03011 as a contrast agent for imaging of atherosclerosis. © 2012 American Heart Association, Inc.

Petzschner F.H.,Ludwig Maximilians University of Munich | Petzschner F.H.,Bernstein Center for Computational Neurosciences | Petzschner F.H.,University of Würzburg | Ponce I.P.,University of Würzburg | And 4 more authors.
Magnetic Resonance in Medicine | Year: 2011

Quantification of magnetic resonance parameters plays an increasingly important role in clinical applications, such as the detection and classification of neurodegenerative diseases. The major obstacle that remains for its widespread use in clinical routine is the long scanning times. Therefore, strategies that allow for significant decreases in scan time are highly desired. Recently, the k-t principal component analysis method was introduced for dynamic cardiac imaging to accelerate data acquisition. This is done by undersampling k-t space and constraining the reconstruction of the aliased data based on the k-t Broad-use Linear Acquisition Speed-up Technique (BLAST) concept and predetermined temporal basis functions. The objective of this study was to investigate whether the k-t principal component analysis concept can be adapted to parameter quantification, specifically allowing for significant acceleration of an inversion recovery fast imaging with steady state precession (TrueFISP) acquisition. We found that three basis functions and a single training data line in central k-space were sufficient to achieve up to an 8-fold acceleration of the quantification measurement. This allows for an estimation of relaxation times T 1 and T 2 and spin density in one slice with sub-millimeter in-plane resolution, in only 6 s. Our findings demonstrate that the k-t principal component analysis method is a potential candidate to bring the acquisition time for magnetic resonance parameter mapping to a clinically acceptable level. Copyright © 2011 Wiley-Liss, Inc.

Heismann B.,Siemens AG | Heismann B.,Friedrich - Alexander - University, Erlangen - Nuremberg | Ott M.,Research Center Magnetic Resonance Bavaria | Grodzki D.,Siemens AG
Magnetic Resonance in Medicine | Year: 2015

Purpose: Clinical MRI patients typically experience elevated acoustic noise levels of 80-110 dB(A). In this study, standard clinical turbo spin echo (TSE) and gradient echo (GRE) sequences were optimized for reduced acoustic noise at preserved diagnostic image quality. Methods: The physical sources of acoustic noise generation in an MRI gradient coil were analyzed. A sequence conversion algorithm was derived that optimized the gradient time scheme for an arbitrary MRI sequence, preserving the governing spin physics. The algorithm was applied to generate "quiet" versions of standard clinical TSE and GRE sequences. Results: The first volunteer images indicated that contrast-to-noise ratio and perceived diagnostic image quality remained on the same level for the algorithmic optimization. Additional careful TSE- and GRE-specific protocol adaptions yielded total acoustic noise reductions of up to 14.4 dB(A) for the TSE and up to 16.8 dB(A) for the GRE. Conclusion: A physical sound pressure reduction of 81% (TSE) and 86% (GRE) for MRI patients was achieved. The results can be used to render MRI scans more patient-friendly in clinical practice, particularly for patients who are young, scared, or elderly. © 2014 Wiley Periodicals, Inc.

Hahn T.,University of Würzburg | Heinzel S.,University of Würzburg | Dresler T.,University of Würzburg | Plichta M.M.,University of Würzburg | And 8 more authors.
Human Brain Mapping | Year: 2011

The impact of individual differences on human reward processing has been a focus of research in recent years, particularly, as they are associated with a variety of neuropsychiatric diseases including addiction and attention-deficit/hyperactivity disorder. Studies exploring the neural basis of individual differences in reward sensitivity have consistently implicated the ventral striatum (VS) as a core component of the human reward system. However, the mechanisms of dopaminergic neurotransmission underlying ventral striatal activation as well as trait reward sensitivity remain speculative. We addressed this issue by investigating the triadic interplay between VS reactivity during reward anticipation using functional magnetic resonance imaging, trait reward sensitivity, and dopamine (DA) transporter genotype (40-bp 3'VNTR of DAT, SLC6A3) affecting synaptic DA neurotransmission. Our results show that DAT variation moderates the association between VS-reactivity and trait reward sensitivity. Specifically, homozygote carriers of the DAT 10-repeat allele exhibit a strong positive correlation between reward sensitivity and reward-related VS activity whereas this relationship is absent in the DAT 9-repeat allele carriers. We discuss the possibility that this moderation of VS-trait relation might arise from DAT-dependent differences in DA availability affecting synaptic plasticity within the VS. Generally, studying the impact of dopaminergic gene variations on the relation between reward-related brain activity and trait reward sensitivity might facilitate the investigation of complex mechanisms underlying disorders linked to dysregulation of DA neurotransmission. © 2010 Wiley-Liss, Inc.

Blaimer M.,Research Center Magnetic Resonance Bavaria | Jakob P.M.,Research Center Magnetic Resonance Bavaria | Breuer F.A.,Research Center Magnetic Resonance Bavaria
Magnetic Resonance in Medicine | Year: 2014

Purpose To implement a regularization method for the phase-constrained generalized partially parallel acquisitions (GRAPPA) algorithm to reduce image artifacts caused by data inconsistencies. Methods Phase-constrained GRAPPA reconstructions are implemented through the use of virtual coils. To that end, synthetic virtual coils are generated by using complex conjugate symmetric signals from the actual coils. Regularization is achieved by applying coefficient-based penalty factors during the GRAPPA calibration procedure. Different penalizing factors are applied for the actual and virtual coils. The method is tested in vivo using T2-weighted turbo spin echo (TSE) images. Results T2 signal decay perturbs conjugate k-space symmetry and produces artifacts in phase-constrained parallel MRI reconstructions of T2-weighted TSE images. Using the proposed regularization method, artifacts are suppressed at the cost of noise amplification. However, there is still a significant SNR gain compared with conventional GRAPPA. Conclusion The proposed regularization method is an efficient approach for artifact suppression and maintains the SNR benefit of phase-constrained parallel MRI over conventional parallel MRI. © 2013 Wiley Periodicals, Inc.

Koktzoglou I.,NorthShore University HealthSystem | Sheehan J.J.,NorthShore University HealthSystem | Dunkle E.E.,NorthShore University HealthSystem | Breuer F.A.,Research Center Magnetic Resonance Bavaria | Edelman R.R.,NorthShore University HealthSystem
Magnetic Resonance in Medicine | Year: 2010

Contrast-enhanced magnetic resonance angiography is routinely performed using parallel imaging to best capture the first pass of contrast material through the target vasculature, followed by digital subtraction to suppress the appearance of unwanted signal from background tissue. Both processes, however, amplify noise and can produce uninterpretable images when large acceleration factors are used. Using a phantom study of contrast-enhanced magnetic resonance angiography, we show that complex subtraction processing prior to partially parallel reconstruction improves reconstruction accuracy relative to magnitude subtraction processing for reduction factors as large as 12. Time-resolved contrast-enhanced magnetic resonance angiographic data obtainedwith complex subtraction in volunteers supported the results of the phantom study and when compared with magnitude subtraction processing demonstrated reduced geometry factors as well as improved image quality at large reduction factors. © 2010 Wiley-Liss, Inc.

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