Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie

Gottingen, Germany

Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie

Gottingen, Germany
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Schweisfurth M.A.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Schweisfurth M.A.,German Primate Center | Schweizer R.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Frahm J.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie
NeuroImage | Year: 2011

This study explored the question of intra-digit somatotopy of sensory representations in the little and index finger of 10 subjects using tactile stimulation of the fingertip (p1) and base (p4) and functional magnetic resonance imaging (fMRI) at 1.5. mm isotropic spatial resolution. The Euclidian distances between p1 and p4 peak representations in Brodmann area 3b resulted in 5.0 ± 0.7. mm for the little finger and 6.7 ± 0.5. mm for the index finger. These non-collocated representations were found to be consistently ordered across subjects for the little but not the index finger. When using separate distances for medial-lateral, anterior-posterior, and inferior-superior orientations, p4 was 1.9 ± 0.7. mm medial to p1 for the little finger in agreement with findings in macaque monkeys, whereas no consistent intra-digit somatotopy across subjects was found for the index finger. This discrepancy could point to differences in the map-forming processes based on sensory input. On the behavioral level it may be attributed to our everyday use of the hand, for which p4 of the index finger plays a much less important role than p4 of the little finger, which is located at the outer border of the hand. © 2011 Elsevier Inc.


Merrem A.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie
Investigative Radiology | Year: 2017

OBJECTIVE: The aim of this study was to develop a rapid diffusion-weighted (DW) magnetic resonance imaging (MRI) technique for whole-brain studies without susceptibility artifacts and measuring times below 3 minutes. MATERIALS AND METHODS: The proposed method combines a DW spin-echo module with a single-shot stimulated echo acquisition mode MRI sequence. Previous deficiencies in image quality due to limited signal-to-noise ratio are compensated for (1) by radial undersampling to enhance the flip angle and thus the signal strength of stimulated echoes; (2) by defining the image reconstruction as a nonlinear inverse problem, which is solved by the iteratively regularized Gauss-Newton method; and (3) by denoising with use of a modified nonlocal means filter. The method was implemented on a 3 T MRI system (64-channel head coil, 80 mT · m gradients) and evaluated for 10 healthy subjects and 2 patients with an ischemic lesion and epidermoid cyst, respectively. RESULTS: High-quality mean DW images of the entire brain were obtained by acquiring 1 non-DW image and 6 DW images with different diffusion directions at b = 1000 s · mm. The achievable resolution for a total measuring time of 84 seconds was 1.5 mm in plane with a section thickness of 4 mm (55 sections). A measuring time of 168 seconds allowed for an in-plane resolution of 1.25 mm and a section thickness of 3 mm (54 sections). Apparent diffusion coefficient values were in agreement with literature data. CONCLUSIONS: The proposed method for DW MRI offers immunity against susceptibility problems, high spatial resolution, adequate signal-to-noise ratio and clinically feasible scan times of less than 3 minutes for whole-brain studies. More extended clinical trials require accelerated computation and online reconstruction. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.


Dreha-Kulaczewski S.,University of Gottingen | Joseph A.A.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Joseph A.A.,German Center for Cardiovascular Research | Merboldt K.-D.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | And 4 more authors.
Journal of Neuroscience | Year: 2017

CSF flux is involved in the pathophysiology of neurodegenerative diseases and cognitive impairment after traumatic brain injury, all hallmarked by the accumulation of cellular metabolic waste. Its effective disposal via various CSF routes has been demonstrated in animal models. In contrast, the CSF dynamics in humans are still poorly understood. Using novel real-time MRI, forced inspiration has been identified recently as a main driving force of CSF flow in the human brain. Exploiting technical advances toward real-time phase-contrast MRI, the current work analyzed directions, velocities, and volumes of human CSF flow within the brain aqueduct as part of the internal ventricular system and in the spinal canal during respiratory cycles. A consistent upward CSF movement toward the brain in response to forced inspiration was seen in all subjects at the aqueduct, in 11/12 subjects at thoracic level 2, and in 4/12 subjects at thoracic level 5. Concomitant analyses of CSF dynamics and cerebral venous blood flow, that is, in epidural veins at cervical level 3, uniquely demonstrated CSF and venous flow to be closely communicating cerebral fluid systems in which inspiration-induced downward flow of venous blood due to reduced intrathoracic pressure is counterbalanced by an upward movement of CSF. The results extend our understanding of human CSF flux and open important clinical implications, including concepts for drug delivery and new classifications and therapeutic options for various forms of hydrocephalus and idiopathic intracranial hypertension. © 2017 the authors.


Watanabe T.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Frahm J.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Michaelis T.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie
NeuroImage | Year: 2016

Using proton MRS and MRI of mouse brain at 9.4 T, this work provides the first in vivo evidence of pH-dependent concurrent changes of three amide signals and related metabolic responses to hypercapnia and hypothermia. During hypercapnia, amide proton MRS signals of glutamine at 6.8-6.9 ppm and 7.6 ppm as well as of unspecific compounds at 8.1-8.3 ppm increase by at least 50% both at 37 °C and 22 °C. These changes reflect a reduced proton exchange with water. They are strongly correlated with intracellular pH which ranges from 6.75 ± 0.10 to 7.13 ± 0.06 as determined from a shift in creatine phosphokinase equilibrium. In MRI, saturation transfer from aliphatic as well as aromatic and/or amide protons alters slightly during hypercapnia and significantly during hypothermia. The asymmetry in magnetization transfer ratios decreased slightly during hypercapnia and hypothermia. Regardless of pH or temperature, saturation transfer from aliphatic protons between -2 and -4 ppm frequency offset to water protons is significantly greater than that from aromatic/amide protons at corresponding offsets between +2 and +4 ppm. Irradiation of aliphatic compounds at -3.5 ppm frequency offset from water predominantly saturates lipids and water associated with myelin. Taken together, the results indicate that, for the B1 power used in this study, dipolar coupling between aliphatic and water protons rather than proton exchange is the dominant factor in Z-spectra and magnetization transfer ratio asymmetry of the brain in vivo. © 2016 Elsevier Inc.


Watanabe T.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Frahm J.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Michaelis T.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie
NeuroImage | Year: 2010

This work demonstrates manganese-enhanced magnetization transfer (MT) MRI to improve the contrast of myelinated structures in mouse brain in vivo. Systemic administration of manganese chloride led to a reduction of the MT ratio by 23% in white matter and 35% in gray matter. The effect increased their contrast-to-noise ratio by 48% and facilitated a mapping of myelin-rich white matter tissues. Relaxation time measurements revealed the manganese-induced shortening of T1 to be smaller in the corpus callosum (-42%) than in the cortex (-52%) or hippocampus (-60%). These findings are in line with the assumption that a high myelin and correspondingly low water content hinder the free diffusion and uptake of manganese ions. The resulting preferential accumulation of manganese in gray matter structures causes a stronger reduction of the MT saturation in gray matter than in white matter. Extending MRI assessments with conventional MT contrast, manganese-enhanced MT MRI at 76 × 80 × 160 μm3 resolution and 2.35 T field strength allowed for a delineation of small myelinated structures such as the fornix, mammillothalamic tract, and fasciculus retroflexus in the living mouse brain. © 2009 Elsevier Inc. All rights reserved.


Schweisfurth M.A.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Schweisfurth M.A.,German Primate Center | Frahm J.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Schweizer R.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie
Frontiers in Human Neuroscience | Year: 2014

This study determined the individual maps of all fingers in Brodmann area 3b of the human primary somatosensory cortex in a single fMRI session by tactile stimulation at 19 sites across all phalanges and digit bases of the 5 right-hand digits. To quantify basic features of the digit maps within and across subjects, we applied standard descriptive measures, but also implemented a novel quantitative analysis. This so-called Direction/Order (DiOr) method tested whether subjects exhibited an ordering of peak fMRI representations along their individual direction of alignment through the set of analyzed phalanges and whether these individual directions were similar across subjects. Across-digit analysis demonstrated that for each set of homologous phalanges, the D5-to-D1 representations were successively represented along a common direction of alignment. Hence, the wellknown mediolateral D5-to-D1 somatotopy was not only confirmed for the distal phalanges (p1), but could also be shown for the medial (p2) and proximal phalanges (p3). In contrast, the peak activation for the digit bases (p4) only partly elicited that digit succession. Complementary, intra-digit analysis revealed a divergent picture of map topography for the different digits. Within D5 (and in a trend: D4), an ordered p1-to-p3 succession was found across subjects, pointing to a consistent intra-digit somatotopy for D5, with p3 generally found medial-posterior to p1. In contrast, for D1, D2, and D3, most subjects did not present with ordered p1-to-p3 maps nor were directions of alignment similarly oriented between subjects. These digits therefore exhibited highly diverse representation patterns across subjects. © 2014 Schweis furth, Frahm and Schweizer.


Dreha-Kulaczewski S.,University of Gottingen | Joseph A.A.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Joseph A.A.,German Center for Cardiovascular Research | Merboldt K.-D.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | And 4 more authors.
Journal of Neuroscience | Year: 2015

The mechanisms behind CSF flow in humans are still not fully known. CSF circulates from its primary production sites at the choroid plexus through the brain ventricles to reach the outer surface of the brain in the subarachnoid spaces from where it drains into venous bloodstream and cervical lymphatics. According to a recent concept of brain fluid transport, established in rodents, CSF from the brain surface also enters the brain tissue along para-arterial routes and exits through paravenous spaces again into subarachnoid compartments. This unidirectional flow is mainly driven by arterial pulsation. To investigate how CSF flow is regulated in humans, we applied a novel real-time magnetic resonance imaging technique at high spatial (0.75 mm) and temporal (50 ms) resolution in healthy human subjects. We observed significant CSF flow exclusively with inspiration. In particular, during forced breathing, high CSF flow was elicited during every inspiration, whereas breath holding suppressed it. Only a minor flow component could be ascribed to cardiac pulsation. The present results unambiguously identify inspiration as the most important driving force for CSF flow in humans. Inspiratory thoracic pressure reduction is expected to directly modulate the hydrostatic pressure conditions for the low-resistance paravenous, venous, and lymphatic clearance routes of CSF. Furthermore, the experimental approach opens new clinical opportunities to study the pathophysiology of various forms of hydrocephalus and to design therapeutic strategies in relation to CSF flow alterations. © 2015 the authors.


Hofer S.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Karaus A.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Frahm J.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie
Frontiers in Neuroanatomy | Year: 2010

The human visual system comprises elongated fiber pathways that represent a serious challenge for diffusion tensor imaging (DTI) and fiber tractography: while tracking of frontal fiber bundles may be compromised by the nearby presence of air-filled cavities, nerves, and eye muscles, the anatomic courses of the three main fiber bundles of the optic radiation are subject to pronounced inter-subject variability. Here, tractography of the entire visual pathway was achieved in six healthy subjects at high spatial accuracy, that is, at 1.8 mm isotropic spatial resolution, without susceptibility-induced distortions, and in direct correspondence to anatomic MRI structures. Using a newly developed diffusion-weighted single-shot STEAM MRI sequence, we were able to track the thin optic nerve including the nasal optic nerve fibers, which cross the optic chiasm, and to dissect the optic radiation into the anterior ventral bundle (Meyer's loop), the central bundle, and the dorsal bundle. Apart from scientific applications these results in single subjects promise advances in the planning of neurosurgical procedures to avoid unnecessary damage to the visual fiber system.


Sumpf T.J.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Uecker M.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Boretius S.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Frahm J.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie
Journal of Magnetic Resonance Imaging | Year: 2011

Purpose: To develop a model-based reconstruction technique for T2 mapping based on multi-echo spin-echo MRI sequences with highly undersampled Cartesian data encoding. Materials and Methods: The proposed technique relies on a nonlinear inverse reconstruction algorithm which directly estimates a T2 and spin-density map from a train of undersampled spin echoes. The method is applicable to acquisitions with single receiver coils but benefits from multi-element coil arrays. The algorithm is validated for trains of 16 spin echoes with a spacing of 10 to 12 ms using numerical simulations as well as human brain MRI at 3 Tesla (T). Results: When compared with a standard T2 fitting procedure using fully sampled T2-weighted images, and depending on the available signal-to-noise ratio and number of coil elements, model-based nonlinear inverse reconstructions for both simulated and in vivo MRI data yield accurate T2 estimates for undersampling factors of 5 to 10. Conclusion: This work describes a promising strategy for T2-weighted MRI that simultaneously offers accurate T2 relaxation times and properly T2-weighted images at arbitrary echo times. For a standard spin-echo MRI sequence with Cartesian encoding, the method allows for a much higher degree of undersampling than obtainable by conventional parallel imaging. © 2011 Wiley-Liss, Inc.


Zhang S.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Block K.T.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie | Frahm J.,Biomedizinische Nmr Forschungs Gmbh Am Max Planck Institute For Biophysikalische Chemie
Journal of Magnetic Resonance Imaging | Year: 2010

Purpose: To develop technical advances for real-time magnetic resonance imaging (MRI) that allow for improved image quality and high frame rates. Materials and Methods: The approach is based on a combination of fast low-angle shot (FLASH) MRI sequences with radial data sampling and view sharing of successive acquisitions. Gridding reconstructions provide images free from streaking or motion artifacts and with a flexible trade-off between spatial and temporal resolution. Immediate image reconstruction and online display is accomplished with the use of an unmodified 3 T MRI system. For receive coils with a large number of elements this process is supported by a user-selectable channel compression that is based on a principal component analysis and performed during initial preparation scans. Results: In preliminary applications to healthy volunteers, real-time radial FLASH MRI visualized continuous movements of the temporomandibular joint during voluntary opening and closing of the mouth at high spatial resolution (0.75 mm in-plane) and monitored cardiac functions at high temporal resolution (20 images per second) during free breathing and without synchronization to the electrocardiogram. Conclusion: Real-time radial FLASH MRI emerges as a simple and versatile tool for a large range of clinical applications. © 2009 Wiley-Liss, Inc.

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