Structural and Metabolic Brain Imaging

Brain activation is (sometimes) reflected in changes of the acquired MR signal. Depending on the selected acquisition method, these changes may reflect underlying neuronal activation, or just very unspecific changes in local blood oxygenation or flow.The magnetic fingerprint of neuronal activation strongly depends on local physiological processes and on the underlying microscopic composition of the neuronal tissue and microvascular architecture and dynamics. High-resolution structural and quantitative imaging is thus a prerequisite to these structural and hemodynamic properties on a mesoscopic level.
current research

Deuterium spectroscopy is a novel and efficient way to observe energy metabolism in vivo. Due to its almost negligible natural abundance, 2H brought into the body e.g. in deuterated glucose can be observed in both its spatial distribution and its metabolic conversion. It is thus an interesting way to investigate pathologies, which change metabolic rates, like cancer. [more]
Ultra-high field Magnetic Resonance Imaging of whole post-mortem brains is complementary to histology and pathology studies and can be useful for tissue characterization, sectioning, 3D-reconstruction of sectioned tissue data, and for diagnosis and investigation of neurodegenerative diseases. To preserve the tissue, the cerebrospinal fluid must be replaced by a fixative agent such as formalin. [more]
Archeological samples are often precious and unique and cannot easily be examined without destroying them. Accordingly, noninvasive imaging techniques are an important means of investigating historic specimen. [more]
Multi-parametric mapping techniques are an important tool in quantitative brain MRI to enable characterization of tissues and early diagnosis of pathologies within short acquisition times. Longitudinal and transverse relaxation times have proved to be a useful measure for monitoring brain tumors or neurodegenerative diseases, such as multiple sclerosis, Parkinson’s disease, or Alzheimer’s disease. [more]
Early detection of Alzheimer’s may benefit from small voxel-sizes and enhancement of contrast at high field. By direct comparison with histology, our results suggest that amyloid plaque can be directly observed at 14.1T, thus paving the way for clinical applications at 9.4T and below. [more]
The anatomy of the brain nuclei located in the midbrain are challenging in view of their small size and limited available signal-to-noise-ratio. 9.4T offer distinct advantages, with greater contrast effects between structures and sufficient SNR even for voxel sizes of a few hundred micrometers. [more]
We analyze the feasibility of chemical exchange detection with balanced steady-state free precession experiments in brain tissues at high to ultra-high fields – an in vitro study. [more]
For clinical implementation, a chemical exchange saturation transfer (CEST) imaging sequence must be fast, with high signal-to-noise ratio (SNR), 3D coverage, and produce robust contrast. However, spectrally selective CEST contrast requires dense sampling of the Z-spectrum, which increases scan duration. This project proposes a compromise. [more]
Chemical exchange saturation transfer (CEST) allows for indirect detection of solute molecules via exchanging protons that transfer selectively applied saturation to the large water pool in tissue. While studies have been performed at clinical field strengths, CEST effects can be studied more specifically at higher field strengths where peak separation and selective saturation benefit from the increased frequency separation between resonances, proportional to the Larmor frequency. [more]
Chemical exchange saturation transfer (CEST) MRI enables the indirect detection of metabolites in small concentrations via exchange of protons in functional groups and water protons. CEST effects were observed in vivo for amide protons of proteins, amine protons of glutamate, guanidyl protons of creatine, and also for hydroxyl protons of glycosaminoglycans and myo‐inositol. [more]
The energy metabolism in the cells is largely handled by phosphorus metabolites. Mainly PCr and ATP are well-known high-energy phosphates that are easily visible in 31P-MR spectra. In addition, the resonance of NAD (Nicotinamide adenine dinucleotide), which is oxidized during the process of ATP formation by oxidative phosphorylation, may give important information on mitochondrial function. [more]
A direct link between tissue microstructure and its magnetic properties need to be established. Although ex vivo tissue in combination with histology is helpful in specific contexts (e.g. detection of amyloid plaques in Alzheimer’s in small tissue speciments) a more general use requires adaptation to high field and characterization of the fixation process per se. [more]
Diffusion-weighted imaging (DWI) is widely used for clinical disease assessment as it allows tracking of microstructural diffusion processes and fiber trajectories in white matter (WM) based on the anisotropic motion of water protons. Quantitative measures derived from diffusion tensor imaging (DTI), such as mean, axial, and radial diffusivity (MD, AD, RD) or fractional anisotropy (FA), reflect changes in the tissue microenvironment, facilitating the assessment and monitoring of degenerative diseases such as multiple sclerosis, Parkinson's disease, Alzheimer's disease, or tissue changes after acute ischemic stroke. [more]
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