Peter Jakob

Publications of Peter Jakob

• Visualization of inflammation using (19) F-magnetic resonance imaging and perfluorocarbons.

  Authors: Guido Stoll, Thomas Basse-Lüsebrink, Gesa Weise, Peter Jakob

  Wiley interdisciplinary reviews. Nanomedicine and nanobiotechnology. 03/2012;

  Inflammation plays a central pathophysiological role in a large number of diseases. While conventional magnetic resonance imaging (MRI) can depict gross tissue alterations due to proton changes,Inflammation plays a central pathophysiological role in a large number of diseases. While conventional magnetic resonance imaging (MRI) can depict gross tissue alterations due to proton changes, specific visualization of inflammation is an unmet task in clinical medicine. (19) F/(1) H MRI is a novel technology that allows tracking of stem and immune cells in experimental disease models after labelling with perfluorocarbon (PFC) emulsions. (19) F markers such as PFC compounds provide a unique signal in vivo due to the negligible (19) F background signal of the body. Concomitant acquisition of (1) H images places the labelled cells into their anatomical context. This novel imaging technique has been applied to monitor immune cell responses in myocardial infarction, pneumonia, bacterial abscess formation, peripheral nerve injury, and rejection of donor organs after transplantation. Upon systemic application PFC nanoparticles are preferentially phagozytosed by circulating monocytes/macrophages and, thus, the fluorine signal in inflamed organs mainly reflects macrophage infiltration. Moreover, attenuation of the inflammatory response after immunosuppressive or antibiotic treatments could be depicted based on (19) F/(1) H-MRI. Compared to other organ systems (19) F-MRI of neuroinflammation is still challenging, mainly because of lack in sensitivity. In focal cerebral ischemia early application of PFCs revealed ongoing thrombotic vessel occlusion rather than cell migration indicating that timing of contrast agent application is critical. Current restrictions of (19) F/(1) H-MRI in sensitivity may be overcome by improved imaging hardware, imaging sequences and reconstruction techniques, as well as improved label development and cell labelling procedures in the future. WIREs Nanomed Nanobiotechnol 2012 doi: 10.1002/wnan.1168 For further resources related to this article, please visit the WIREs website.

• Quantification and localization of contrast agents using delta relaxation enhanced magnetic resonance at 1.5 T.

  Authors: Uvo Christoph Hoelscher, Steffen Lother, Florian Fidler, Martin Blaimer, Peter Jakob

  Magma (New York, N.Y.). 11/2011;

  OBJECT: Delta relaxation enhanced magnetic resonance (dreMR) is a new imaging technique based on the idea of cycling the magnetic field B (0) during an imaging sequence. The method determines theOBJECT: Delta relaxation enhanced magnetic resonance (dreMR) is a new imaging technique based on the idea of cycling the magnetic field B (0) during an imaging sequence. The method determines the field dependency of the relaxation rate (relaxation dispersion dR (1)/dB). This quantity is of particular interest in contrast agent imaging because the parameter can be used to determine contrast agent concentrations and increases the ability to localize the contrast agent. MATERIALS AND METHODS: In this paper dreMR imaging was implemented on a clinical 1.5 T MR scanner combining conventional MR imaging with fast field-cycling. Two improvements to dreMR theory are presented describing the quantification of contrast agent concentrations from dreMR data and a correction for field-cycling with finite ramp times. RESULTS: Experiments demonstrate the use of the extended theory and show the measurement of contrast agent concentrations with the dreMR method. A second experiment performs localization of a contrast agent with a significant improvement in comparison to conventional imaging. CONCLUSION: dreMR imaging has been extended by a method to quantify contrast agent concentrations and improved for field-cycling with finite ramp times. Robust localization of contrast agents using dreMR imaging has been performed in a sample where conventional imaging delivers inconclusive results.

• Molecular magnetic resonance imaging (MRI) of inflamed myocardium using ferucarbotran in patients with acute myocardial infarction

  Authors: Ali Yilmaz, Sabine Rösch, Karin Klingel, Reinhard Kandolf, Xavier Helluy, Karl-Heinz Hiller, Peter Jakob, Udo Sechtem

  Journal of Cardiovascular Magnetic Resonance. 01/2011;

• Magnetic resonance imaging of tumors colonized with bacterial ferritin-expressing Escherichia coli.

  Authors: Philip J Hill, Jochen Stritzker, Miriam Scadeng, Ulrike Geissinger, Daniel Haddad, Thomas C Basse-Lüsebrink, Uwe Gbureck, Peter Jakob, Aladar A Szalay

  PloS one. 01/2011; 6(10):e25409.

  Recent studies have shown that human ferritin can be used as a reporter of gene expression for magnetic resonance imaging (MRI). Bacteria also encode three classes of ferritin-type molecules withRecent studies have shown that human ferritin can be used as a reporter of gene expression for magnetic resonance imaging (MRI). Bacteria also encode three classes of ferritin-type molecules with iron accumulation properties. Here, we investigated whether these bacterial ferritins can also be used as MRI reporter genes and which of the bacterial ferritins is the most suitable reporter. Bacterial ferritins were overexpressed in probiotic E. coli Nissle 1917. Cultures of these bacteria were analyzed and those generating highest MRI contrast were further investigated in tumor bearing mice. Among members of three classes of bacterial ferritin tested, bacterioferritin showed the most promise as a reporter gene. Although all three proteins accumulated similar amounts of iron when overexpressed individually, bacterioferritin showed the highest contrast change. By site-directed mutagenesis we also show that the heme iron, a unique part of the bacterioferritin molecule, is not critical for MRI contrast change. Tumor-specific induction of bacterioferritin-expression in colonized tumors resulted in contrast changes within the bacteria-colonized tumors. Our data suggest that colonization and gene expression by live vectors expressing bacterioferritin can be monitored by MRI due to contrast changes.

• Visualization of abscess formation in a murine thigh infection model of Staphylococcus aureus by 19F-magnetic resonance imaging (MRI).

  Authors: Tobias Hertlein, Volker Sturm, Stefan Kircher, Thomas Basse-Lüsebrink, Daniel Haddad, Knut Ohlsen, Peter Jakob

  PloS one. 01/2011; 6(3):e18246.

  During the last years, (19)F-MRI and perfluorocarbon nanoemulsion (PFC) emerged as a powerful contrast agent based MRI methodology to track cells and to visualize inflammation. We applied this newDuring the last years, (19)F-MRI and perfluorocarbon nanoemulsion (PFC) emerged as a powerful contrast agent based MRI methodology to track cells and to visualize inflammation. We applied this new modality to visualize deep tissue abscesses during acute and chronic phase of inflammation caused by Staphylococcus aureus infection. In this study, a murine thigh infection model was used to induce abscess formation and PFC or CLIO (cross linked ironoxides) was administered during acute or chronic phase of inflammation. 24 h after inoculation, the contrast agent accumulation was imaged at the site of infection by MRI. Measurements revealed a strong accumulation of PFC at the abscess rim at acute and chronic phase of infection. The pattern was similar to CLIO accumulation at chronic phase and formed a hollow sphere around the edema area. Histology revealed strong influx of neutrophils at the site of infection and to a smaller extend macrophages during acute phase and strong influx of macrophages at chronic phase of inflammation. We introduce (19)F-MRI in combination with PFC nanoemulsions as a new platform to visualize abscess formation in a murine thigh infection model of S. aureus. The possibility to track immune cells in vivo by this modality offers new opportunities to investigate host immune response, the efficacy of antibacterial therapies and the influence of virulence factors for pathogenesis.

• Sustained reperfusion after blockade of glycoprotein-receptor-Ib in focal cerebral ischemia: an MRI study at 17.6 Tesla.

  Authors: Mirko Pham, Xavier Helluy, Christoph Kleinschnitz, Peter Kraft, Andreas J Bartsch, Peter Jakob, Bernhard Nieswandt, Martin Bendszus, Guido Stoll

  PloS one. 01/2011; 6(4):e18386.

  Inhibition of early platelet adhesion by blockade of glycoprotein-IB (GPIb) protects mice from ischemic stroke. To elucidate underlying mechanisms in-vivo, infarct development was followed byInhibition of early platelet adhesion by blockade of glycoprotein-IB (GPIb) protects mice from ischemic stroke. To elucidate underlying mechanisms in-vivo, infarct development was followed by ultra-high field MRI at 17.6 Tesla. Cerebral infarction was induced by transient-middle-cerebral-artery-occlusion (tMCAO) for 1 hour in C57/BL6 control mice (N = 10) and mice treated with 100 µg Fab-fragments of the GPIb blocking antibody p0p/B 1 h after tMCAO (N = 10). To control for the effect of reperfusion, additional mice underwent permanent occlusion and received anti-GPIb treatment (N = 6; pMCAO) or remained without treatment (N = 3; pMCAO). MRI 2 h and 24 h after MCAO measured cerebral-blood-flow (CBF) by continuous arterial-spin labelling, the apparent-diffusion-coefficient (ADC), quantitative-T2 and T2-weighted imaging. All images were registered to a standard mouse brain MRI atlas and statistically analysed voxel-wise, and by cortico-subcortical ROI analysis. Anti-GPIb treatment led to a relative increase of postischemic CBF vs. controls in the cortical territory of the MCA (2 h: 44.2±6.9 ml/100 g/min versus 24 h: 60.5±8.4; p = 0.0012, F((1,18)) = 14.63) after tMCAO. Subcortical CBF 2 h after tMCAO was higher in anti-GPIb treated animals (45.3±5.9 vs. controls: 33.6±4.3; p = 0.04). In both regions, CBF findings were clearly related to a lower probability of infarction (Cortex/Subcortex of treated group: 35%/65% vs. controls: 95%/100%) and improved quantitative-T2 and ADC. After pMCAO, anti-GPIb treated mice developed similar infarcts preceded by severe irreversible hypoperfusion as controls after tMCAO indicating dependency of stroke protection on reperfusion. Blockade of platelet adhesion by anti-GPIb-Fab-fragments results in substantially improved CBF early during reperfusion. This finding was in exact spatial correspondence with the prevention of cerebral infarction and indicates in-vivo an increased patency of the microcirculation. Thus, progression of infarction during early ischemia and reperfusion can be mitigated by anti-platelet treatment.

• Outcome of experimental stroke in C57Bl/6 and Sv/129 mice assessed by multimodal ultra-high field MRI.

  Authors: Mirko Pham, Xavier Helluy, Stefan Braeuninger, Peter Jakob, Guido Stoll, Christoph Kleinschnitz, Martin Bendszus

  Experimental & translational stroke medicine. 03/2010; 2:6.

  Transgenic mice bred on C57Bl/6 or Sv/129 genetic background are frequently used in stroke research. It is well established that variations in cerebrovascular anatomy and hemodynamics can influenceTransgenic mice bred on C57Bl/6 or Sv/129 genetic background are frequently used in stroke research. It is well established that variations in cerebrovascular anatomy and hemodynamics can influence stroke outcome in different inbred mouse lines. We compared stroke development in C57Bl/6 and Sv/129 mice in the widely used model of transient middle cerebral artery occlusion (tMCAO) by multimodal ultra-high field magnetic resonance imaging (MRI).C57Bl/6 and Sv/129 mice underwent 60 min of tMCAO and were analyzed by MRI 2 h and 24 h afterwards. Structural and functional images were registered to a standard anatomical template. Probability maps of infarction were rendered by automated segmentation from quantitative T2-relaxometric images. Whole-brain segmentation of infarction was accomplished manually on high-resolution T2-weighted (T2-w) RARE images. Cerebral perfusion (cerebral blood flow, CBF) was measured quantitatively by modified continuous arterial-spin-labeling (CASL) and apparent diffusion coefficients (ADC) by spin-echo diffusion-weighted imaging (DWI).Probabilities of cortical (95.1% +/- 3.1 vs. 92.1% +/- 2.5; p > 0.05) and subcortical (100% vs. 100%; p > 0.05) infarctions at 24 h were similar in both groups as was the whole-brain volumetric extent of cerebral infarction. In addition, CBF and ADC values did not differ between C57Bl/6 and Sv/129 mice at any time point or region of interest.The C57Bl/6 and Sv/129 genetic background is no major confounding factor of infarct size and cerebral perfusion in the tMCAO model.

• High-resolution 3D magnetic resonance imaging and quantification of carious lesions and dental pulp in vivo.

  Authors: Olga Tymofiyeva, Julian Boldt, Kurt Rottner, Florian Schmid, Ernst-Juergen Richter, Peter Jakob

  Magma (New York, N.Y.). 11/2009;

  OBJECTIVE: The purpose of the study was to assess the feasibility of MRI of three-dimensional visualization and quantification of carious lesions, as well as measurement of the distance between theOBJECTIVE: The purpose of the study was to assess the feasibility of MRI of three-dimensional visualization and quantification of carious lesions, as well as measurement of the distance between the lesion and dental pulp in vivo. MATERIALS AND METHODS: High-resolution 3D MRI was performed to measure seven carious lesions in vivo using gelatinous gadolinium-based oral contrast medium in combination with an intraoral radio frequency receiver coil on a clinical 1.5 T MRI scanner. Extension of the carious lesion in three spatial dimensions and the minimum distance between the lesion and dental pulp were quantified. When possible, the result was compared to an X-ray projection and an impression of the lesion taken using a plastic impression material before and after dental treatment. RESULTS: Carious lesions, including pit and fissure, approximal lesions, and occult dentin caries, could be visualized due to the MRI signal rise in the porous affected dentin. The minimum distance between the carious lesion and dental pulp could be determined in all cases. CONCLUSION: The results presented demonstrate the feasibility of high-resolution dental MRI to three-dimensionally visualize and quantify carious lesions, including approximal and occult caries lesions, and measure the minimum distance to the dental pulp.

• The Metabolic Role of the Legume Endosperm: A Non-invasive Imaging Study.

  Authors: Gerd Melkus, Hardy Rolletschek, Ruslana Radchuk, Johannes Fuchs, Twan Rutten, Ulrich Wobus, Thomas Altmann, Peter Jakob, Ljudmilla Borisjuk

  Plant physiology. 09/2009;

  Although essential for normal seed development in the legumes, the metabolic role of the endosperm remains uncertain. We designed non invasive nuclear magnetic resonance (NMR) tools for the in vivoAlthough essential for normal seed development in the legumes, the metabolic role of the endosperm remains uncertain. We designed non invasive nuclear magnetic resonance (NMR) tools for the in vivo study on key metabolites in the transient liquid endosperm of intact pea seeds. The steady state levels of sucrose, glutamine and alanine could be monitored and their distribution within the embryo sac visualized. Seed structure was digitalized as a 3-dimensional model, providing volume information for distinct seed organs. The NMR method, combined with laser micro-dissection, isotope labelling, in situ hybridization and electron microscopy, was used to contrast the wild type endosperm with that of a mutant in which embryo growth is retarded. Expression of sequences encoding amino acid and sucrose transporters was up-regulated earlier in the endosperm than in the embryo, and this activity led to the accumulation of soluble metabolites in the endosperm vacuole. The endosperm provides a temporary source of nutrition, permits space for embryo growth, and acts as a buffer between the maternal organism and its offspring. The concentration of sucrose in the endosperm vacuole is developmentally controlled, while the total amount accumulated depends on the growth of the embryo. The endosperm concentration of glutamine is a limiting factor for protein storage. The properties of the endosperm ensure that the young embryo develops within a homeostatic environment, necessary to sustain embryogenesis. We argue for a degree of metabolite-mediated control exerted by the endosperm on the growth of, and assimilate storage by the embryo.

• Functional repair of embolized vessels in maize roots after temporal drought stress, as demonstrated by magnetic resonance imaging.

  Authors: Ilja Kaufmann, Thomas Schulze-Till, Heike U Schneider, Ulrich Zimmermann, Peter Jakob, Lars H Wegner

  The New phytologist. 07/2009;

  * Xylem sap under high tension is in a metastable state and tends to cavitate, frequently leading to an interruption of the continuous water columns. Mechanisms of cavitation repair are* Xylem sap under high tension is in a metastable state and tends to cavitate, frequently leading to an interruption of the continuous water columns. Mechanisms of cavitation repair are controversially discussed. * Magnetic resonance (MR) imaging provides a noninvasive, high spatial and temporal resolution approach to monitor xylem cavitation, refilling, and functionality. * Spin density maps of drought-stressed maize taproots were recorded to localize cavitation events and to visualize the refilling processes; c. 2 h after release of the nutrient solution from the homemade MR imaging cuvette that received the root, late metaxylem vessels started to cavitate randomly as identified by a loss of signal intensity. After c. 6 h plants were rewatered, leading to a repair of water columns in five out of eight roots. Sap ascent during refilling, monitored with multislice MR imaging sequences, varied between 0.5 mm min(-1) and 3.3 mm min(-1). Flow imaging of apparently refilled vessels was performed to test for functional repair. Occasionally, a collapse of xylem vessels under tension was observed; this collapse was reversible upon rewatering. * Refilling was an all-or-none process only observed under low-light conditions. Absence of flow in some of the apparently refilled vessels indicates that functionality was not restored in these particular vessels, despite a recovery of the spin density signal.

• Monitoring of Tumor Oxygenation Changes in Head-and-Neck Carcinoma Patients Breathing a Hyperoxic Hypercapnic Gas Mixture with a Noninvasive MRI Technique.

  Authors: Markus Kotas, Peter Schmitt, Peter Jakob, Michael Flentje

  Strahlentherapie und Onkologie : Organ der Deutschen Rontgengesellschaft ... [et al]. 02/2009; 185(1):19-26.

  PURPOSE: : To implement and evaluate a noninvasive functional MRI technique for measuring tumor tissue oxygenation changes in head-and-neck carcinoma patients. PATIENTS AND METHODS: : TissuePURPOSE: : To implement and evaluate a noninvasive functional MRI technique for measuring tumor tissue oxygenation changes in head-and-neck carcinoma patients. PATIENTS AND METHODS: : Tissue oxygenation changes were determined quantitatively in 13 patients with head-and-neck cancer. The MR examinations were performed on a clinical MR scanner at 1.5 T. Different breathing gases (air, 2% CO(2) and 98% O(2), 100% oxygen) were administered to induce oxygenation changes. A multigradient echo sequence was used for quantification of the apparent transverse relaxation time T2*. RESULTS: : Pixel-by-pixel analysis of the T2* values in tumors showed a shift toward higher values corresponding to oxygenation increase and correlated with a median shift toward positive values in the DeltaT2* fraction under carbogen and oxygen breathing in most but not all patients. A slightly pronounced T2* increase breathing oxygen compared with 2% CO(2)/98% O(2) was found. Furthermore, a statistically significant difference in the heterogeneity of oxygenation changes induced by oxygen or 2% CO(2)/ 98% O(2) breathing was seen. CONCLUSION: : Measurement of oxygenation changes in head-and-neck tumor patients is feasible by the presented MRI technique. Tumor oxygenation and oxygenation changes were heterogeneous among the investigated patients. To the authors' knowledge, they are the first to describe a statistically significant difference in the heterogeneity of oxygenation changes induced by oxygen or 2% CO(2)/98% O(2) breathing using a noninvasive MRI technique.

• In vivo comparison of atherosclerotic plaque progression with vessel wall strain and blood flow velocity in apoE(-/-) mice with MR microscopy at 17.6 T.

  Authors: Volker Herold, Jeremy Wellen, Christian Ziener, Thomas Weber, Karl-Heinz Hiller, Peter Nordbeck, Eberhard Rommel, Axel Haase, Wolfgang Bauer, Peter Jakob, Susanta Sarkar

  Magma (New York, N.Y.). 02/2009;

  OBJECT: At present, in vivo plaque characterization in mice by MRI is typically limited to the visualization of vascular lesions with no accompanying analysis of vessel wall function. The aim of thisOBJECT: At present, in vivo plaque characterization in mice by MRI is typically limited to the visualization of vascular lesions with no accompanying analysis of vessel wall function. The aim of this study was to analyze the influence of atherosclerotic plaque development on the morphological and mechanical characteristics of the aortic vessel wall in a pre-clinical murine model of atherosclerosis. MATERIALS AND METHODS: Groups of apolipoprotein E-deficient (apoE(-/-)) and C57BL/6J control mice fed a high-fat diet were monitored over a 12-week time period by high-field MRI. Multi-Slice-Multi-Spin-Echo and Phase-Contrast MRI sequences were employed to track changes to aortic vessel wall area, blood flow velocity and distensibility. RESULTS: After 6- and 12-weeks, significant changes in vessel wall area and circumferential strain were detected in the apoE(-/-) mice relative to the control animals. Blood flow velocity and intravascular lumen remained unchanged in both groups, findings that are in agreement with the theory of positive remodeling of the ascending aorta during plaque progression. CONCLUSION: This study has demonstrated the application of high-field MRI for characterizing the temporal progression of morphological and mechanical changes to murine aortic vasculature associated with atherosclerotic lesion development.

• Ex vivo expanded hematopoietic progenitor cells improve cardiac function after myocardial infarction: role of beta-catenin transduction and cell dose.

  Authors: Christian Templin, Daniel Kotlarz, Jörg Faulhaber, Sabine Schnabel, Karsten Grote, Gustavo Salguero, Maren Luchtefeld, Karl-Heinz Hiller, Peter Jakob, Hassan Y Naim, Bernhard Schieffer, Denise Hilfiker-Kleiner, Ulf Landmesser, Florian P Limbourg, Helmut Drexler

  Journal of molecular and cellular cardiology. 10/2008; 45(3):394-403.

  Cell-based therapy after myocardial infarction (MI) is a promising therapeutic option but the relevant cell subsets and dosage requirements are poorly defined. We hypothesized that cell therapy forCell-based therapy after myocardial infarction (MI) is a promising therapeutic option but the relevant cell subsets and dosage requirements are poorly defined. We hypothesized that cell therapy for myocardial infarction is improved by ex vivo expansion and high-dose transplantation of defined hematopoietic progenitor cells (HPCs). Since beta-catenin promotes self-renewal of stem cells we evaluated the therapeutic efficacy of beta-catenin-mediated ex vivo expansion of mouse HPCs in a mouse model of myocardial ischemia/reperfusion followed by intraarterial cell delivery. The impact of cell dose was determined by comparing a low-dose (LD, 5 x 10(5) cells) vs. a high-dose (HD, 1 x 10(7) cells) cell transplantation regimen of beta-catenin-HPCs. The impact of beta-catenin modification of HPCs was determined by comparing control-transduced HPCs (GFP-HPCs) vs. transgenic beta-catenin-HPCs. HD beta-catenin-HPCs significantly improved LV function and end-systolic and end-diastolic dimensions as compared to saline and LD beta-catenin-HPCs. Furthermore, while treatment with HD GFP-HPC resulted in a modest cardiac improvement the application of beta-catenin-HPCs was superior, resulting in a significant improvement in EF, FS and LVESD over saline and control GFP-HPC treatment. Although myocardial engraftment of HPCs was only transient, as determined by cell quantification after dye labeling, beta-catenin-HPC treatment significantly decreased infarct size, reduced cardiomyocyte apoptosis and increased capillary angiogenesis in vitro and in vivo. Ex vivo expanded HPCs improve cardiac function and remodeling post MI in a cell number- and beta-catenin-dependent manner.

• Quantitative in vivo (1)H spectroscopic imaging of metabolites in the early postnatal mouse brain at 17.6 T.

  Authors: Kilian Weiss, Gerd Melkus, Peter Jakob, Cornelius Faber

  Magma (New York, N.Y.). 10/2008;

  OBJECT: Early postnatal brain maturation is closely connected to local changes of metabolite levels. Spatially resolved in vivo (1)H NMR spectroscopic imaging is applied to follow absolute changes ofOBJECT: Early postnatal brain maturation is closely connected to local changes of metabolite levels. Spatially resolved in vivo (1)H NMR spectroscopic imaging is applied to follow absolute changes of brain metabolites in early postnatal mouse brain. MATERIALS AND METHODS: A short echo time semi LASER (localization by adiabatic selective refocusing) chemical shift imaging (CSI) sequence incorporating weighted k-space averaging was implemented at high magnetic field (17.6 T). In vivo measurements were carried out on postnatal days 5, 8, 12, 16, and 20. In vivo relaxation times T (1) and T (2) were measured using variable repetition times or a CPMG sequence, respectively, combined with LASER single voxel localization. RESULTS: Spectra were obtained with a spatial resolution of (1 x 1) mm(2) in a 1.5 mm slice as early as postnatal day 5. Maturational changes of absolute metabolite concentrations of major metabolites were calculated in four different brain regions. A significant increase of N-acetylaspartate (NAA), total creatine (tCr), and glutamate/glutamine (Glx) concentration was paralleled by a decrease of taurine (Tau) concentration with age (P < 0.05). Differences between brain regions were found for NAA, tCr, and Tau (P < 0.05). Furthermore, in vivo T (1) and T (2) of the four major brain metabolites in adult mice are reported. CONCLUSION: The implemented semi LASER CSI sequence allows following regional changes of metabolite levels. It is suitable for investigation of local differences in brain metabolism and development.

• Reconstruction of undersampled non-Cartesian data sets using pseudo-Cartesian GRAPPA in conjunction with GROG.

  Authors: Nicole Seiberlich, Felix Breuer, Robin Heidemann, Martin Blaimer, Mark Griswold, Peter Jakob

  Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine. 06/2008; 59(5):1127-37.

  Most k-space-based parallel imaging reconstruction techniques, such as Generalized Autocalibrating Partially Parallel Acquisitions (GRAPPA), necessitate the acquisition of regularly sampled CartesianMost k-space-based parallel imaging reconstruction techniques, such as Generalized Autocalibrating Partially Parallel Acquisitions (GRAPPA), necessitate the acquisition of regularly sampled Cartesian k-space data to reconstruct a nonaliased image efficiently. However, non-Cartesian sampling schemes offer some inherent advantages to the user due to their better coverage of the center of k-space and faster acquisition times. On the other hand, these sampling schemes have the disadvantage that the points acquired generally do not lie on a grid and have complex k-space sampling patterns. Thus, the extension of Cartesian GRAPPA to non-Cartesian sequences is nontrivial. This study introduces a simple, novel method for performing Cartesian GRAPPA reconstructions on undersampled non-Cartesian k-space data gridded using GROG (GRAPPA Operator Gridding) to arrive at a nonaliased image. Because the undersampled non-Cartesian data cannot be reconstructed using a single GRAPPA kernel, several Cartesian patterns are selected for the reconstruction. This flexibility in terms of both the appearance and number of patterns allows this pseudo-Cartesian GRAPPA to be used with undersampled data sets acquired with any non-Cartesian trajectory. The successful implementation of the reconstruction algorithm using several different trajectories, including radial, rosette, spiral, one-dimensional non-Cartesian, and zig-zag trajectories, is demonstrated.

• Self-calibrating GRAPPA operator gridding for radial and spiral trajectories.

  Authors: Nicole Seiberlich, Felix Breuer, Martin Blaimer, Peter Jakob, Mark Griswold

  Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine. 05/2008; 59(4):930-5.

  Self-calibrating GRAPPA operator gridding (GROG) is a method by which non-Cartesian MRI data can be gridded using spatial information from a multichannel coil array without the need for an additionalSelf-calibrating GRAPPA operator gridding (GROG) is a method by which non-Cartesian MRI data can be gridded using spatial information from a multichannel coil array without the need for an additional calibration dataset. Using self-calibrating GROG, the non-Cartesian datapoints are shifted to nearby k-space locations using parallel imaging weight sets determined from the datapoints themselves. GROG employs the GRAPPA Operator, a special formulation of the general reconstruction method GRAPPA, to perform these shifts. Although GROG can be used to grid undersampled datasets, it is important to note that this method uses parallel imaging only for gridding, and not to reconstruct artifact-free images from undersampled data. The innovation introduced here, namely, self-calibrating GROG, allows the shift operators to be calculated directly out of the non-Cartesian data themselves. This eliminates the need for an additional calibration dataset, which reduces the imaging time and also makes the GROG reconstruction more robust by removing possible inconsistencies between the calibration and non-Cartesian datasets. Simulated and in vivo examples of radial and spiral datasets gridded using self-calibrating GROG are compared to images gridded using the standard method of convolution gridding.

• Quantitative imaging of oil storage in developing crop seeds.

  Authors: Thomas Neuberger, Nese Sreenivasulu, Markus Rokitta, Hardy Rolletschek, Cornelia Göbel, Twan Rutten, Volodja Radchuk, Ivo Feussner, Ulrich Wobus, Peter Jakob, Andrew Webb, Ljudmilla Borisjuk

  Plant biotechnology journal. 02/2008; 6(1):31-45.

  In this article, we present a tool which allows the rapid and non-invasive detection and quantitative visualization of lipid in living seeds at a variety of stages using frequency-selected magneticIn this article, we present a tool which allows the rapid and non-invasive detection and quantitative visualization of lipid in living seeds at a variety of stages using frequency-selected magnetic resonance imaging. The method provides quantitative lipid maps with a resolution close to the cellular level (in-plane 31 microm x 31 microm). The reliability of the method was demonstrated using two contrasting subjects: the barley grain (monocot, 2% oil, highly compartmentalized) and the soybean grain (dicot, 20% oil, economically important oilseed). Steep gradients in local oil storage were defined at the organ- and tissue-specific scales. These gradients were closely coordinated with tissue differentiation and seed maturation, as revealed by electron microscopy and biochemical and gene expression analysis. The method can be used to elucidate similar oil accumulation processes in different tissues/organs, as well as to follow the fate of storage lipids during deposition and subsequent mobilization.

• Physical and biological properties of barium cross-linked alginate membranes.

  Authors: Heiko Zimmermann, Felix Wählisch, Claudia Baier, Markus Westhoff, Randolph Reuss, Dirk Zimmermann, Marcus Behringer, Friederike Ehrhart, Alisa Katsen-Globa, Christoph Giese, Uwe Marx, Vladimir L Sukhorukov, Julio A Vásquez, Peter Jakob, Stephen G Shirley, Ulrich Zimmermann

  Biomaterials. 04/2007; 28(7):1327-45.

  We describe the manufacture of highly stable and elastic alginate membranes with good cell adhesivity and adjustable permeability. Clinical grade, ultra-high viscosity alginate is gelled by diffusionWe describe the manufacture of highly stable and elastic alginate membranes with good cell adhesivity and adjustable permeability. Clinical grade, ultra-high viscosity alginate is gelled by diffusion of Ba2+ followed by use of the "crystal gun" [Zimmermann H. et al., Fabrication of homogeneously cross-linked, functional alginate microcapsules validated by NMR-, CLSM- and AFM-imaging. Biomaterials 2003;24:2083-96]. Burst pressure of well-hydrated membranes is between 34 and 325kPa depending on manufacture and storage details. Water flows induced by sorbitol and raffinose (probably diffusional) are lower than those caused by PEG 6000, which may be related to a Hagen-Poiseuille flow. Hydraulic conductivity, L(p), from PEG-induced flows ranges between 2.4x10(-12) and 6.5x10(-12) m Pa(-1)s(-1). Hydraulic conductivity measured with hydrostatic pressure up to 6 kPa is 2-3 orders of magnitude higher and decreases with increasing pressure to about 3x10(-10) m Pa(-1)s(-1) at 4kPa. Mechanical introduction of 200 microm-diameter pores increases hydraulic conductivity dramatically without loss of mechanical stability or flexibility. NMR imaging with Cu2+ as contrast agent shows a layered structure in membranes cross-linked for 2h. Phase contrast and atomic force microscopy in liquid environment reveals surface protrusions and cavities correlating with steps of the production process. Murine L929 cells adhere strongly to the rough surface of crystal-bombarded membranes. NaCl-mediated membrane swelling can be prevented by partial replacement of salt with sorbitol allowing cell culture on the membranes.

• Correlation of MRT imaging with real-time axiography of TMJ clicks.

  Authors: Olga Tymofiyeva, Peter Proff, Ernst-Jürgen Richter, Peter Jakob, Jochen Fanghänel, Tomas Gedrange, Kurt Rottner

  Annals of anatomy = Anatomischer Anzeiger : official organ of the Anatomische Gesellschaft. 02/2007; 189(4):356-61.

  There is a series of tools useful for gathering diagnostic information on patients with temporomandibular joint disorders. Tracings of the joint movement (axiography) provide useful information aboutThere is a series of tools useful for gathering diagnostic information on patients with temporomandibular joint disorders. Tracings of the joint movement (axiography) provide useful information about the motion of the joints. Since the availability of electronic axiographic tracers, the movement of the condyles can be resolved with high resolution both in space and in time. In order to obtain information about the anatomical relation of the joint surfaces and the disc, magnetic resonance tomography imaging (MRI) is routinely carried out. It is common practice to take MR images of the joints with the mouth closed and fully open. In order to correlate the MR images with the axiographic tracings, a series of images can provide much more information. In this study we examined patients with distinct temporomandibular joint (TMJ) clicks. In one case, the click occurs once a day, while in the other case the click happens every time the mouth is opened. In order to obtain information about both motion and anatomical relation of the TMJ at and around the position where the clicks occur, we recorded a series of MRI scans with the mouth gradually opened and before and after joint clicks. Real-time axiographic tracings during the click were taken with an optimized system where the polar moments were reduced as much as possible to follow the movement during the click. These tracings were correlated with the MRI scans to determine the exact internal conditions of the TMJ and the changes during the click. In particular cases, the additional information provided by this procedure can be useful in deciding whether and which therapeutic intervention is advisable.

• Assessment of inhibitory potency of antibiotics by MRI: apparent T2 as a marker of cell growth.

  Authors: Verena Hoerr, Kerstin Hoffmann, Curd Schollmayer, Ulrike Holzgrabe, Axel Haase, Peter Jakob, Cornelius Faber

  Magma (New York, N.Y.). 12/2006; 19(5):247-55.

  A new method to assess the antibiotic potency by MRI has been developed. Correlating 1H NMR spectra of bacterial cultures with the extracellular parameters T2, OD600, and pH, a relationship betweenA new method to assess the antibiotic potency by MRI has been developed. Correlating 1H NMR spectra of bacterial cultures with the extracellular parameters T2, OD600, and pH, a relationship between cell growth and T2 variations was established. T2 is influenced by chemical exchange that depends on pH, composition, and concentration of the medium. Changes in the medium from bacterial metabolism are reflected in alternating T2 values. At 17.6 T, growth curves based on T2 values were measured simultaneously of several cultures of Streptococcus vestibularis. From T2 growth curves in the presence of varying concentrations of vancomycin, the minimum inhibitory concentration of the antibiotic could be determined to be 0.33+/-0.08 microM. This value was in good agreement with the result obtained by the conventional broth microdilution. In principle, T2 growth curves can be determined on a large number of cultures simultaneously and may potentially be used as a novel tool in high through-put screening of novel anti-infective substances.