Our research is devoted to the further development and application
of magnetic resonance imaging (MRI) and localized magnetic resonance
spectroscopy for noninvasive studies of animals and humans. Current
projects range from advanced methods that monitor the dynamics of
myocardial functions and blood flow in real time to neurofeedback
training in humans by functional brain mapping. The use of genetically
modified animals allows us to link molecular and genetic information
to MRI-accessible functions at the system level.
Our recent breakthrough towards real-time MRI is based on the use
of non-Cartesian spatial encoding, pronounced data undersampling,
and image reconstruction by regularized nonlinear inversion. Pertinent
techniques bear the potential to alter the future of (clinical) MRI. They
allow for movie recordings of speech production, turbulent flow or
the beating heart – without synchronization to the ECG and during
free breathing. The computational demand is met by a parallelized
algorithm and multiple graphical processing units which could be fully
integrated into the software framework of a commercial MRI system.
A second area of research focuses on studies of the functional organization
of the human brain and its axonal connectivity. Diffusion
MRI provides information about the orientational dependence of the
anisotropic water mobility in brain tissue and may be exploited for
three-dimensional reconstructions of nerve fiber tracts. In order to overcome
limitations of the standard echo-planar imaging technique we
developed a single-shot stimulated-echo MRI sequence which is now
further extended by radial undersampling and nonlinear inverse reconstruction.
Functional brain mapping deals with the neural encoding
of sensorimotor functions. Our results for fine-scale finger somatotopy
in humans indicate consistent intra-digit topographic maps for the
little but not the index finger within the primary somatosensory cortex.
Neurofeedback training of brain activity is a potential treatment option
for psychiatric diseases offering access to arbitrary structures. Our aim
is to investigate the role of fMRI-based neurofeedback in the anterior
mid-cingulate cortex which relates to higher-order cognitive processes.
Animal MRI research addresses the pathophysiologic mechanisms
underlying human brain disorders. The development of MRI techniques
for transgenic mice allows for structural, metabolic, and functional
assessments of the mouse brain at high spatial resolution. An
observation of utmost importance is the high but reversible elevation
of brain lactate in response to volatile anesthetics. The metabolite
responses to various neuromodulators indicate a stimulation of
adrenergic pathways as well as an inhibition of the respiratory chain.
Corresponding findings in conditional Cox10 mutant mice, in which
oligodendrocytes suffer from impaired oxidative energy metabolism,
suggest the use of lactate as brain energy source, so that oligodendrocytes
survive by enhanced nonoxidative glucose consumption which in
turn secures the maintainance of myelin as well as long-term axonal